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排序方式: 共有174条查询结果,搜索用时 15 毫秒
41.
Li J Jiang T Mao JH Balmain A Peterson L Harris C Rao PH Havlak P Gibbs R Cai WW 《Nature genetics》2004,36(9):952-954
By analyzing genomic copy-number differences using high-resolution mouse whole-genome BAC arrays, we uncover substantial differences in regional DNA content between inbred strains of mice. The identification of these apparently common segmental polymorphisms suggests that these differences can contribute to genetic variability and pathologic susceptibility. 相似文献
42.
43.
Nonsense-mediated messenger RNA decay (NMD) is triggered by premature translation termination, but the features distinguishing premature from normal termination are unknown. One model for NMD suggests that decay-inducing factors bound to mRNAs during early processing events are routinely removed by elongating ribosomes but remain associated with mRNAs when termination is premature, triggering rapid turnover. Recent experiments challenge this notion and suggest a model that posits that mRNA decay is activated by the intrinsically aberrant nature of premature termination. Here we use a primer extension inhibition (toeprinting) assay to delineate ribosome positioning and find that premature translation termination in yeast extracts is indeed aberrant. Ribosomes encountering premature UAA or UGA codons in the CAN1 mRNA fail to release and, instead, migrate to upstream AUGs. This anomaly depends on prior nonsense codon recognition and is eliminated in extracts derived from cells lacking the principal NMD factor, Upf1p, or by flanking the nonsense codon with a normal 3'-untranslated region (UTR). Tethered poly(A)-binding protein (Pab1p), used as a mimic of a normal 3'-UTR, recruits the termination factor Sup35p (eRF3) and stabilizes nonsense-containing mRNAs. These findings indicate that efficient termination and mRNA stability are dependent on a properly configured 3'-UTR. 相似文献
44.
Global analysis of protein localization in budding yeast 总被引:1,自引:0,他引:1
45.
Losos JB Leal M Glor RE De Queiroz K Hertz PE Rodríguez Schettino L Lara AC Jackman TR Larson A 《Nature》2003,424(6948):542-545
Niche conservatism--the tendency for closely related species to be ecologically similar--is widespread. However, most studies compare closely related taxa that occur in allopatry; in sympatry, the stabilizing forces that promote niche conservatism, and thus inhibit niche shifts, may be countered by natural selection favouring ecological divergence to minimize the intensity of interspecific interactions. Consequently, the relative importance of niche conservatism versus niche divergence in determining community structure has received little attention. Here, we examine a tropical lizard community in which species have a long evolutionary history of ecological interaction. We find that evolutionary divergence overcomes niche conservatism: closely related species are no more ecologically similar than expected by random divergence and some distantly related species are ecologically similar, leading to a community in which the relationship between ecological similarity and phylogenetic relatedness is very weak. Despite this lack of niche conservatism, the ecological structuring of the community has a phylogenetic component: niche complementarity only occurs among distantly related species, which suggests that the strength of ecological interactions among species may be related to phylogeny, but it is not necessarily the most closely related species that interact most strongly. 相似文献
46.
Shi Y Sawada J Sui G Affar el B Whetstine JR Lan F Ogawa H Luke MP Nakatani Y Shi Y 《Nature》2003,422(6933):735-738
47.
p53 mutant mice that display early ageing-associated phenotypes. 总被引:56,自引:0,他引:56
Stuart D Tyner Sundaresan Venkatachalam Jene Choi Stephen Jones Nader Ghebranious Herbert Igelmann Xiongbin Lu Gabrielle Soron Benjamin Cooper Cory Brayton Sang Hee Park Timothy Thompson Gerard Karsenty Allan Bradley Lawrence A Donehower 《Nature》2002,415(6867):45-53
The p53 tumour suppressor is activated by numerous stressors to induce apoptosis, cell cycle arrest, or senescence. To study the biological effects of altered p53 function, we generated mice with a deletion mutation in the first six exons of the p53 gene that express a truncated RNA capable of encoding a carboxy-terminal p53 fragment. This mutation confers phenotypes consistent with activated p53 rather than inactivated p53. Mutant (p53+/m) mice exhibit enhanced resistance to spontaneous tumours compared with wild-type (p53+/+) littermates. As p53+/m mice age, they display an early onset of phenotypes associated with ageing. These include reduced longevity, osteoporosis, generalized organ atrophy and a diminished stress tolerance. A second line of transgenic mice containing a temperature-sensitive mutant allele of p53 also exhibits early ageing phenotypes. These data suggest that p53 has a role in regulating organismal ageing. 相似文献
48.
Helgadottir A Manolescu A Helgason A Thorleifsson G Thorsteinsdottir U Gudbjartsson DF Gretarsdottir S Magnusson KP Gudmundsson G Hicks A Jonsson T Grant SF Sainz J O'Brien SJ Sveinbjornsdottir S Valdimarsson EM Matthiasson SE Levey AI Abramson JL Reilly MP Vaccarino V Wolfe ML Gudnason V Quyyumi AA Topol EJ Rader DJ Thorgeirsson G Gulcher JR Hakonarson H Kong A Stefansson K 《Nature genetics》2006,38(1):68-74
Variants of the gene ALOX5AP (also known as FLAP) encoding arachidonate 5-lipoxygenase activating protein are known to be associated with risk of myocardial infarction. Here we show that a haplotype (HapK) spanning the LTA4H gene encoding leukotriene A4 hydrolase, a protein in the same biochemical pathway as ALOX5AP, confers modest risk of myocardial infarction in an Icelandic cohort. Measurements of leukotriene B4 (LTB4) production suggest that this risk is mediated through upregulation of the leukotriene pathway. Three cohorts from the United States also show that HapK confers a modest relative risk (1.16) in European Americans, but it confers a threefold larger risk in African Americans. About 27% of the European American controls carried at least one copy of HapK, as compared with only 6% of African American controls. Our analyses indicate that HapK is very rare in Africa and that its occurrence in African Americans is due to European admixture. Interactions with other genetic or environmental risk factors that are more common in African Americans are likely to account for the greater relative risk conferred by HapK in this group. 相似文献
49.
An important mechanism for ice cloud formation in the Earth's atmosphere is homogeneous nucleation of ice in aqueous droplets, and this process is generally assumed to produce hexagonal ice. However, there are some reports that the metastable crystalline phase of ice, cubic ice, may form in the Earth's atmosphere. Here we present laboratory experiments demonstrating that cubic ice forms when micrometre-sized droplets of pure water and aqueous solutions freeze homogeneously at cooling rates approaching those found in the atmosphere. We find that the formation of cubic ice is dominant when droplets freeze at temperatures below 190 K, which is in the temperature range relevant for polar stratospheric clouds and clouds in the tropical tropopause region. These results, together with heat transfer calculations, suggest that cubic ice will form in the Earth's atmosphere. If there were a significant fraction of cubic ice in some cold clouds this could increase their water vapour pressure, and modify their microphysics and ice particle size distributions. Under specific conditions this may lead to enhanced dehydration of the tropopause region. 相似文献
50.
Porco CC Baker E Barbara J Beurle K Brahic A Burns JA Charnoz S Cooper N Dawson DD Del Genio AD Denk T Dones L Dyudina U Evans MW Fussner S Giese B Grazier K Helfenstein P Ingersoll AP Jacobson RA Johnson TV McEwen A Murray CD Neukum G Owen WM Perry J Roatsch T Spitale J Squyres S Thomas P Tiscareno M Turtle EP Vasavada AR Veverka J Wagner R West R 《Nature》2005,434(7030):159-168
Titan, the largest moon of Saturn, is the only satellite in the Solar System with a substantial atmosphere. The atmosphere is poorly understood and obscures the surface, leading to intense speculation about Titan's nature. Here we present observations of Titan from the imaging science experiment onboard the Cassini spacecraft that address some of these issues. The images reveal intricate surface albedo features that suggest aeolian, tectonic and fluvial processes; they also show a few circular features that could be impact structures. These observations imply that substantial surface modification has occurred over Titan's history. We have not directly detected liquids on the surface to date. Convective clouds are found to be common near the south pole, and the motion of mid-latitude clouds consistently indicates eastward winds, from which we infer that the troposphere is rotating faster than the surface. A detached haze at an altitude of 500 km is 150-200 km higher than that observed by Voyager, and more tenuous haze layers are also resolved. 相似文献