全文获取类型
收费全文 | 980篇 |
免费 | 10篇 |
国内免费 | 34篇 |
专业分类
系统科学 | 20篇 |
丛书文集 | 2篇 |
教育与普及 | 3篇 |
理论与方法论 | 12篇 |
现状及发展 | 206篇 |
研究方法 | 131篇 |
综合类 | 624篇 |
自然研究 | 26篇 |
出版年
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 18篇 |
2012年 | 67篇 |
2011年 | 95篇 |
2010年 | 37篇 |
2009年 | 24篇 |
2008年 | 52篇 |
2007年 | 66篇 |
2006年 | 52篇 |
2005年 | 63篇 |
2004年 | 39篇 |
2003年 | 64篇 |
2002年 | 53篇 |
2001年 | 40篇 |
2000年 | 42篇 |
1999年 | 20篇 |
1996年 | 4篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1971年 | 9篇 |
1970年 | 9篇 |
1969年 | 7篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1966年 | 5篇 |
1965年 | 7篇 |
排序方式: 共有1024条查询结果,搜索用时 187 毫秒
971.
Zusammenfassung Die Insulinwirkung auf die Magensäuresekretion wurde in männlichen Sprague-Dawley Ratten untersucht, deren Pylorus 2 h vorher unterbunden war. Eine Dosis-Wirkungskurve wurde aufgestellt. Maximale Sekretion von Magensäure und Magensaft wurden durch s.c. Injektion von 4 Einheiten krystallinischen Zink-Insulins per 100 g Körpergewicht erzielt. Grössere Dosen von Insulin unterdrücken Säure- und Magensaftsekretion. Das Verhalten der Elektrolyte im Magensaft spricht sowohl für die Neutralisierungs-Verdünnungshypothese als auch für die Austausch-Diffusionshypothese zur Erklärung der Magensaftproduktion. 相似文献
972.
R. G. Nagele J. F. Pietrolungo H. Lee 《Cellular and molecular life sciences : CMLS》1981,37(3):304-306
Summary Coated vesicles were found to accumulate Ca++ in neuroepithelial cells and may play a role in regulating the contractile activities of apical microfilament bundles during uplifting of neural folds in the chick.This study was supported in part by grants from the Research Council and the Charles and Johanna Busch Memorial Fund of Rutgers University. 相似文献
973.
Distribution of tunichrome and vanadium in sea squirt blood cells sorted by flow cytometry 总被引:1,自引:0,他引:1
E M Oltz S Pollack T Delohery M J Smith M Ojika S Lee K Kustin K Nakanishi 《Experientia》1989,45(2):186-190
Specialized blood cells of many tunicates accumulate high concentrations of vanadium and phenolic peptide pigments called tunichromes (TC). In order to determine whether V and TC reside in the same cells, Ascidia nigra and Ascidia ceratodes blood cell subpopulations were isolated by fluorescence-activated cell sorting (flow cytometry) and chemically analyzed. V was found in the spherical, green/grey signet ring cells, and to a lesser degree in the mulberry-shaped, yellow/green morula cells (MRs), whereas free TC was detected mainly in MRs. 相似文献
974.
应用~3H-TdR光镜和电镜放射自显影观察表明,MGc80-3 细胞标记指数达31.51%,标记银粒集中于分裂间期的S期细胞核中,细胞核呈重标记状态,绝大多数标记银粒分布于细胞核常染色质区域,少数见于核孔附近的常染色质或核孔附近的细胞质中,核仁未见标记,显示细胞内 DNA合成十分活跃。但经 dBcAMP诱导后,标记指数则降至 4.35%,细胞核呈弱标记状态,电镜放射自显影则未在细胞核内见到标记银粒,表明其DNA合成受到明显抑制。这种变化是由于dBcAMP诱导胃癌细胞内cAMP水平提高而实现的,认为DNA合成抑制是导致MGc80-3细胞走向分化的一个重要原因,对于癌变细胞恶性表型逆转具有重要作用。 相似文献
975.
A number of IDSs have been proposed for a networked or distributed environment. A modified DIDS using federated peertopeer architecture, MCR (Multicast Reflector) and modified shaker protocol were proposed. The suggested scheme can be implemented easily and performs the information sharing between lowlevel IDS agents. As all users within a group monitor each other's, the common control server can perform detect intrusions with less cost and support the detection of the inside intruders. 相似文献
976.
HSIAO Taichung LEE Bingjean CHOU Tienyin LIEN Huipain CHANG Yinghuei 《武汉大学学报:自然科学英文版》2007,12(4):610-618
Since 2002,the Soil and Water Conservation Bureau,which is responsible for the conservation and administrative man-agement of hillside in Taiwan,has been cooperating with Feng Chia University. Together,they have successfully carried out the establishment and maintenance of 13 fixed debris flow monitoring stations over the island and 2 mobile debris flow monitoring sta-tions. During July 2004,a powerful southwest air current brought by Mindulle Typhoon caused serious flood in central and southern Taiwan. This paper aims to describe the establishment of debris flow monitoring systems in Taiwan and the observation of the debris flow event during Mindulle Typhoon at Aiyuzi River in Shenmu Village,Nantou County by the monitoring station. 相似文献
977.
Mice deficient for corticotropin-releasing hormone receptor-2 display anxiety-like behaviour and are hypersensitive to stress 总被引:21,自引:0,他引:21
Bale TL Contarino A Smith GW Chan R Gold LH Sawchenko PE Koob GF Vale WW Lee KF 《Nature genetics》2000,24(4):410-414
Corticotropin-releasing hormone (Crh) is a critical coordinator of the hypothalamic-pituitary-adrenal (HPA) axis. In response to stress, Crh released from the paraventricular nucleus (PVN) of the hypothalamus activates Crh receptors on anterior pituitary corticotropes, resulting in release of adrenocorticotropic hormone (Acth) into the bloodstream. Acth in turn activates Acth receptors in the adrenal cortex to increase synthesis and release of glucocorticoids. The receptors for Crh, Crhr1 and Crhr2, are found throughout the central nervous system and periphery. Crh has a higher affinity for Crhr1 than for Crhr2, and urocortin (Ucn), a Crh-related peptide, is thought to be the endogenous ligand for Crhr2 because it binds with almost 40-fold higher affinity than does Crh. Crhr1 and Crhr2 share approximately 71% amino acid sequence similarity and are distinct in their localization within the brain and peripheral tissues. We generated mice deficient for Crhr2 to determine the physiological role of this receptor. Crhr2-mutant mice are hypersensitive to stress and display increased anxiety-like behaviour. Mutant mice have normal basal feeding and weight gain, but decreased food intake following food deprivation. Intravenous Ucn produces no effect on mean arterial pressure in the mutant mice. 相似文献
978.
Lee YA Wahn U Kehrt R Tarani L Businco L Gustafsson D Andersson F Oranje AP Wolkertstorfer A v Berg A Hoffmann U Küster W Wienker T Rüschendorf F Reis A 《Nature genetics》2000,26(4):470-473
Atopic dermatitis (eczema) is a chronic inflammatory skin disease with onset mainly in early childhood It is commonly the initial clinical manifestation of allergic disease, often preceding the onset of respiratory allergies. Along with asthma and allergic rhinitis, atopic dermatitis is an important manifestation of atopy that is characterized by the formation of allergy antibodies (IgE) to environmental allergens. In the developed countries, the prevalence of atopic dermatitis is approximately 15%, with a steady increase over the past decades. Genetic and environmental factors interact to determine disease susceptibility and expression, and twin studies indicate that the genetic contribution is substantial. To identify susceptibility loci for atopic dermatitis, we ascertained 199 families with at least two affected siblings based on established diagnostic criteria. A genome-wide linkage study revealed highly significant evidence for linkage on chromosome 3q21 (Zall=4.31, P= 8.42 10(-6)). Moreover, this locus provided significant evidence for linkage of allergic sensitization under the assumption of paternal imprinting (hlod=3.71,alpha=44%), further supporting the presence of an atopy gene in this region. Our findings indicate that distinct genetic factors contribute to susceptibility to atopic dermatitis and that the study of this disease opens new avenues to dissect the genetics of atopy. 相似文献
979.
Tong ZB Gold L Pfeifer KE Dorward H Lee E Bondy CA Dean J Nelson LM 《Nature genetics》2000,26(3):267-268
Maternal effect genes produce mRNA or proteins that accumulate in the egg during oogenesis. We show here that Mater, a mouse oocyte protein dependent on the maternal genome, is essential for embryonic development beyond the two-cell stage. Females lacking the maternal effect gene Mater are sterile. Null males are fertile. 相似文献
980.
Genome-wide analysis of single-nucleotide polymorphisms in human expressed sequences 总被引:16,自引:0,他引:16
Single-nucleotide polymorphisms (SNPs) have been explored as a high-resolution marker set for accelerating the mapping of disease genes. Here we report 48,196 candidate SNPs detected by statistical analysis of human expressed sequence tags (ESTs), associated primarily with coding regions of genes. We used Bayesian inference to weigh evidence for true polymorphism versus sequencing error, misalignment or ambiguity, misclustering or chimaeric EST sequences, assessing data such as raw chromatogram height, sharpness, overlap and spacing, sequencing error rates, context-sensitivity and cDNA library origin. Three separate validations-comparison with 54 genes screened for SNPs independently, verification of HLA-A polymorphisms and restriction fragment length polymorphism (RFLP) testing-verified 70%, 89% and 71% of our predicted SNPs, respectively. Our method detects tenfold more true HLA-A SNPs than previous analyses of the EST data. We found SNPs in a large fraction of known disease genes, including some disease-causing mutations (for example, the HbS sickle-cell mutation). Our comprehensive analysis of human coding region polymorphism provides a public resource for mapping of disease genes (available at http://www.bioinformatics.ucla.edu/snp). 相似文献