全文获取类型
收费全文 | 15280篇 |
免费 | 28篇 |
国内免费 | 47篇 |
专业分类
系统科学 | 87篇 |
丛书文集 | 181篇 |
教育与普及 | 32篇 |
理论与方法论 | 74篇 |
现状及发展 | 6210篇 |
研究方法 | 796篇 |
综合类 | 7687篇 |
自然研究 | 288篇 |
出版年
2013年 | 110篇 |
2012年 | 270篇 |
2011年 | 550篇 |
2010年 | 108篇 |
2008年 | 326篇 |
2007年 | 311篇 |
2006年 | 332篇 |
2005年 | 339篇 |
2004年 | 324篇 |
2003年 | 285篇 |
2002年 | 265篇 |
2001年 | 462篇 |
2000年 | 447篇 |
1999年 | 311篇 |
1992年 | 271篇 |
1991年 | 198篇 |
1990年 | 226篇 |
1989年 | 220篇 |
1988年 | 225篇 |
1987年 | 222篇 |
1986年 | 207篇 |
1985年 | 296篇 |
1984年 | 232篇 |
1983年 | 160篇 |
1982年 | 167篇 |
1981年 | 153篇 |
1980年 | 184篇 |
1979年 | 422篇 |
1978年 | 309篇 |
1977年 | 309篇 |
1976年 | 289篇 |
1975年 | 323篇 |
1974年 | 390篇 |
1973年 | 366篇 |
1972年 | 381篇 |
1971年 | 435篇 |
1970年 | 553篇 |
1969年 | 465篇 |
1968年 | 471篇 |
1967年 | 431篇 |
1966年 | 387篇 |
1965年 | 285篇 |
1964年 | 87篇 |
1959年 | 169篇 |
1958年 | 297篇 |
1957年 | 199篇 |
1956年 | 185篇 |
1955年 | 150篇 |
1954年 | 185篇 |
1948年 | 138篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
161.
Two canids, Vulpes vulpes and Canis lupus , are recorded from shoreline deposits of Lake Bonneville in north central Utah. Both species are new records in the Pleistocene sediments of Utah and add to our scarce knowledge of the large carnivores that inhabited the shoreline environments of Lake Bonneville. 相似文献
162.
James E. Johnson 《西北部美国博物学家》2011,46(4)
Crayfish distribution and composition in Utah are poorly documented. Based upon limited collections, the native Pacifastacus gambelii is widespread and often abundant in the Bear and Weber river drainages and is occasionally represented in smaller tributaries to the Great Salt Lake and to the Raft River. Pacifastacus leniusculus was collected from Utah County and Procambarus clarkii from Tooele County; the origin of these populations is not known. The nonnative crayfish Orconectes virilis is currently abundant in the Virgin, Price, and Duchesne river basins and the Glen Canyon, Flaming Gorge, Deer Creek, and Starvation reservoirs; it is expanding in Huntington North, Scofield, and Willard reservoirs. Further work is required to develop a more complete inventory and monitor the impacts on aquatic ecosystems of expanding nonnative crayfish populations. Surreptitious stockings can be dealt with only if the public is made aware of the adverse consequences of ill-conceived introductions. 相似文献
163.
Purdue MP Johansson M Zelenika D Toro JR Scelo G Moore LE Prokhortchouk E Wu X Kiemeney LA Gaborieau V Jacobs KB Chow WH Zaridze D Matveev V Lubinski J Trubicka J Szeszenia-Dabrowska N Lissowska J Rudnai P Fabianova E Bucur A Bencko V Foretova L Janout V Boffetta P Colt JS Davis FG Schwartz KL Banks RE Selby PJ Harnden P Berg CD Hsing AW Grubb RL Boeing H Vineis P Clavel-Chapelon F Palli D Tumino R Krogh V Panico S Duell EJ Quirós JR Sanchez MJ Navarro C Ardanaz E Dorronsoro M Khaw KT Allen NE 《Nature genetics》2011,43(1):60-65
164.
Becker-Heck A Zohn IE Okabe N Pollock A Lenhart KB Sullivan-Brown J McSheene J Loges NT Olbrich H Haeffner K Fliegauf M Horvath J Reinhardt R Nielsen KG Marthin JK Baktai G Anderson KV Geisler R Niswander L Omran H Burdine RD 《Nature genetics》2011,43(1):79-84
Primary ciliary dyskinesia (PCD) is a genetically heterogeneous autosomal recessive disorder characterized by recurrent infections of the respiratory tract associated with the abnormal function of motile cilia. Approximately half of individuals with PCD also have alterations in the left-right organization of their internal organ positioning, including situs inversus and situs ambiguous (Kartagener's syndrome). Here, we identify an uncharacterized coiled-coil domain containing a protein, CCDC40, essential for correct left-right patterning in mouse, zebrafish and human. In mouse and zebrafish, Ccdc40 is expressed in tissues that contain motile cilia, and mutations in Ccdc40 result in cilia with reduced ranges of motility. We further show that CCDC40 mutations in humans result in a variant of PCD characterized by misplacement of the central pair of microtubules and defective assembly of inner dynein arms and dynein regulatory complexes. CCDC40 localizes to motile cilia and the apical cytoplasm and is required for axonemal recruitment of CCDC39, disruption of which underlies a similar variant of PCD. 相似文献
165.
Kalay E Yigit G Aslan Y Brown KE Pohl E Bicknell LS Kayserili H Li Y Tüysüz B Nürnberg G Kiess W Koegl M Baessmann I Buruk K Toraman B Kayipmaz S Kul S Ikbal M Turner DJ Taylor MS Aerts J Scott C Milstein K Dollfus H Wieczorek D Brunner HG Hurles M Jackson AP Rauch A Nürnberg P Karagüzel A Wollnik B 《Nature genetics》2011,43(1):23-26
Functional impairment of DNA damage response pathways leads to increased genomic instability. Here we describe the centrosomal protein CEP152 as a new regulator of genomic integrity and cellular response to DNA damage. Using homozygosity mapping and exome sequencing, we identified CEP152 mutations in Seckel syndrome and showed that impaired CEP152 function leads to accumulation of genomic defects resulting from replicative stress through enhanced activation of ATM signaling and increased H2AX phosphorylation. 相似文献
166.
Macgregor S Montgomery GW Liu JZ Zhao ZZ Henders AK Stark M Schmid H Holland EA Duffy DL Zhang M Painter JN Nyholt DR Maskiell JA Jetann J Ferguson M Cust AE Jenkins MA Whiteman DC Olsson H Puig S Bianchi-Scarrà G Hansson J Demenais F Landi MT Dębniak T Mackie R Azizi E Bressac-de Paillerets B Goldstein AM Kanetsky PA Gruis NA Elder DE Newton-Bishop JA Bishop DT Iles MM Helsing P Amos CI Wei Q Wang LE Lee JE Qureshi AA Kefford RF Giles GG Armstrong BK Aitken JF Han J Hopper JL Trent JM Brown KM 《Nature genetics》2011,43(11):1114-1118
We performed a genome-wide association study of melanoma in a discovery cohort of 2,168 Australian individuals with melanoma and 4,387 control individuals. In this discovery phase, we confirm several previously characterized melanoma-associated loci at MC1R, ASIP and MTAP-CDKN2A. We selected variants at nine loci for replication in three independent case-control studies (Europe: 2,804 subjects with melanoma, 7,618 control subjects; United States 1: 1,804 subjects with melanoma, 1,026 control subjects; United States 2: 585 subjects with melanoma, 6,500 control subjects). The combined meta-analysis of all case-control studies identified a new susceptibility locus at 1q21.3 (rs7412746, P = 9.0 × 10(-11), OR in combined replication cohorts of 0.89 (95% CI 0.85-0.95)). We also show evidence suggesting that melanoma associates with 1q42.12 (rs3219090, P = 9.3 × 10(-8)). The associated variants at the 1q21.3 locus span a region with ten genes, and plausible candidate genes for melanoma susceptibility include ARNT and SETDB1. Variants at the 1q21.3 locus do not seem to be associated with human pigmentation or measures of nevus density. 相似文献
167.
Chasman DI Schürks M Anttila V de Vries B Schminke U Launer LJ Terwindt GM van den Maagdenberg AM Fendrich K Völzke H Ernst F Griffiths LR Buring JE Kallela M Freilinger T Kubisch C Ridker PM Palotie A Ferrari MD Hoffmann W Zee RY Kurth T 《Nature genetics》2011,43(7):695-698
Migraine is a common, heterogeneous and heritable neurological disorder. Its pathophysiology is incompletely understood, and its genetic influences at the population level are unknown. In a population-based genome-wide analysis including 5,122 migraineurs and 18,108 non-migraineurs, rs2651899 (1p36.32, PRDM16), rs10166942 (2q37.1, TRPM8) and rs11172113 (12q13.3, LRP1) were among the top seven associations (P < 5 × 10(-6)) with migraine. These SNPs were significant in a meta-analysis among three replication cohorts and met genome-wide significance in a meta-analysis combining the discovery and replication cohorts (rs2651899, odds ratio (OR) = 1.11, P = 3.8 × 10(-9); rs10166942, OR = 0.85, P = 5.5 × 10(-12); and rs11172113, OR = 0.90, P = 4.3 × 10(-9)). The associations at rs2651899 and rs10166942 were specific for migraine compared with non-migraine headache. None of the three SNP associations was preferential for migraine with aura or without aura, nor were any associations specific for migraine features. TRPM8 has been the focus of neuropathic pain models, whereas LRP1 modulates neuronal glutamate signaling, plausibly linking both genes to migraine pathophysiology. 相似文献
168.
Hahn CN Chong CE Carmichael CL Wilkins EJ Brautigan PJ Li XC Babic M Lin M Carmagnac A Lee YK Kok CH Gagliardi L Friend KL Ekert PG Butcher CM Brown AL Lewis ID To LB Timms AE Storek J Moore S Altree M Escher R Bardy PG Suthers GK D'Andrea RJ Horwitz MS Scott HS 《Nature genetics》2011,43(10):1012-1017
169.
Greasewood ( Sarcobatus ) is a succulent-leaved, halophytic shrub of North American origin. The genus comprises 2 species: Sarcobatus baileyi and Sarcobatus vermiculatus. Sarcobatus vermiculatus is common throughout much of western North America, but S. baileyi is much more limited in distribution and was previously thought to be endemic to Nevada. Here we document and describe a S. baileyi population in eastern California, comparing its morphology and ecology to an adjacent S. vermiculatus population. Morphologically, S. baileyi is smaller in stature but produces larger seeds; however, fewer S. baileyi seeds germinated and survived a 20-day laboratory incubation compared to seeds of S. vermiculatus. Sarcobatus baileyi has higher leaf Na concentrations and operates at much lower plant water potentials than S. vermiculatus under field conditions; however, no significant differences were observed between the 2 species in long-term water-use efficiency as measured by leaf δ13C. Leaf Na concentrations were very low in both species. Overall, these species differ greatly in a number of traits that are consistent with the upland, nonphreatophytic character of S. baileyi, which is in stark contrast to the phreatophytic character of S. vermiculatus. Both species, however, are very salt tolerant and have low leaf N concentrations, indicating the low nutrient availability and the potentially high salinity of their extreme habitats. Further investigation of comparable desert ridge environments should be conducted to determine the extent of S. baileyi in eastern California, and common garden comparisons of the 2 species should be conducted to compare their ecophysiological traits. El ";greasewood” ( Sarcobatus ) es un arbusto halofítico de origen norteamericano con hojas suculentas. El género consta de dos especies: Sarcobatus baileyi y Sarcobatus vermiculatus. Aunque S. vermiculatus es común en gran parte del oeste de Norteamerica, S. baileyi tiene una distribución mucho más limitada. Se pensaba anteriormente que S. baileyi era endémico a Nevada, pero aquí documentamos y describimos una población en el este de California, comparando su morfología y ecología con las de una población adyacente de S. vermiculatus. Morfológicamente, S. baileyi es más pequeña de altura, pero produce semillas más grandes. Sin embargo, menos semillas de S. baileyi germinaron y sobrevivieron a una incubación en laboratorio de 20 días, comparado con S. vermiculatus. Sarcobatus baileyi opera con potenciales de agua mucho más bajos que los de S. vermiculatus en condiciones de campo y tiene mayores concentraciones de Na en sus hojas. No obstante, no se observaron diferencias significativas en la eficiencia del uso de agua a largo plazo, medida en términos de δ13C entre las 2 especies. Las concentraciones de N en las hojas fueron muy bajas en ambas especies. En general, estas especies difieren mucho en varios rasgos que son consistentes con el carácter no freatofítico de S. baileyi de tierras altas, el cual contrasta claramente con el carácter freatofítico de S. vermiculatus. Ambas especies, sin embargo, son bastante tolerantes a la sal y tienen concentraciones bajas de N en hojas, lo cual indica la baja disponibilidad de nutrientes y la potencial alta salinidad en sus hábitats extremos. Investigaciones adicionales en ambientes comparables de bordes desérticos deberán llevarse a cabo para determinar la extensión S. baileyi en el este de California, además de comparaciones de las dos especies en jardín para comparar sus rasgos ecofisiológicos. 相似文献
170.
Observations of changes in population density of native White River springfish ( Crenichthys baileyi ) in Pahranagat Valley led to the following hypothesis: introduced convict cichlids ( Cichlasoma nigrofasciatum ) cause reduced growth and recruitment; cover reduces the magnitude of the effect. The hypothesis was tested by establishing sympatric and allopatric groups of the two species in experimental aquaria with and without cover. Change in volume (= mass) and length of the two species over a three-month period in spring 1986 and 1987 was measured and analyzed using 2 × 2 factorial analyses. Convict cichlids caused reduced growth and eliminated recruitment of springfish under the experimental conditions. Cover did not influence growth but positively affected recruitment of springfish in allopatry. It is likely that a portion of the reduced springfish population densities in nature can be attributed to adverse effects from introduced cichlids. 相似文献