全文获取类型
收费全文 | 2813篇 |
免费 | 368篇 |
专业分类
3181篇 |
出版年
2021年 | 26篇 |
2019年 | 31篇 |
2018年 | 32篇 |
2017年 | 32篇 |
2016年 | 51篇 |
2015年 | 85篇 |
2014年 | 71篇 |
2013年 | 133篇 |
2012年 | 124篇 |
2011年 | 131篇 |
2010年 | 72篇 |
2009年 | 66篇 |
2008年 | 99篇 |
2007年 | 122篇 |
2006年 | 109篇 |
2005年 | 126篇 |
2004年 | 111篇 |
2003年 | 80篇 |
2002年 | 78篇 |
2001年 | 71篇 |
2000年 | 97篇 |
1999年 | 84篇 |
1998年 | 46篇 |
1997年 | 54篇 |
1996年 | 35篇 |
1995年 | 34篇 |
1994年 | 35篇 |
1993年 | 30篇 |
1992年 | 76篇 |
1991年 | 49篇 |
1990年 | 65篇 |
1989年 | 61篇 |
1988年 | 55篇 |
1987年 | 52篇 |
1986年 | 43篇 |
1985年 | 49篇 |
1984年 | 29篇 |
1983年 | 36篇 |
1982年 | 36篇 |
1981年 | 30篇 |
1980年 | 36篇 |
1979年 | 39篇 |
1978年 | 30篇 |
1977年 | 32篇 |
1976年 | 31篇 |
1975年 | 26篇 |
1974年 | 31篇 |
1973年 | 27篇 |
1972年 | 28篇 |
1970年 | 25篇 |
排序方式: 共有3181条查询结果,搜索用时 0 毫秒
961.
Inference of the Genetic Architecture Underlying BMI and Height with the Use of 20,240 Sibling Pairs
Gibran Hemani Jian Yang Anna Vinkhuyzen Joseph?E. Powell Gonneke Willemsen Jouke-Jan Hottenga Abdel Abdellaoui Massimo Mangino Ana?M. Valdes Sarah?E. Medland Pamela?A. Madden Andrew?C. Heath Anjali?K. Henders Dale?R. Nyholt Eco?J.C. de?Geus Patrik?K.E. Magnusson Erik Ingelsson Grant?W. Montgomery Timothy?D. Spector Dorret?I. Boomsma Nancy?L. Pedersen Nicholas?G. Martin Peter?M. Visscher 《American journal of human genetics》2013,93(5):865-875
Evidence that complex traits are highly polygenic has been presented by population-based genome-wide association studies (GWASs) through the identification of many significant variants, as well as by family-based de novo sequencing studies indicating that several traits have a large mutational target size. Here, using a third study design, we show results consistent with extreme polygenicity for body mass index (BMI) and height. On a sample of 20,240 siblings (from 9,570 nuclear families), we used a within-family method to obtain narrow-sense heritability estimates of 0.42 (SE = 0.17, p = 0.01) and 0.69 (SE = 0.14, p = 6 × 10−7) for BMI and height, respectively, after adjusting for covariates. The genomic inflation factors from locus-specific linkage analysis were 1.69 (SE = 0.21, p = 0.04) for BMI and 2.18 (SE = 0.21, p = 2 × 10−10) for height. This inflation is free of confounding and congruent with polygenicity, consistent with observations of ever-increasing genomic-inflation factors from GWASs with large sample sizes, implying that those signals are due to true genetic signals across the genome rather than population stratification. We also demonstrate that the distribution of the observed test statistics is consistent with both rare and common variants underlying a polygenic architecture and that previous reports of linkage signals in complex traits are probably a consequence of polygenic architecture rather than the segregation of variants with large effects. The convergent empirical evidence from GWASs, de novo studies, and within-family segregation implies that family-based sequencing studies for complex traits require very large sample sizes because the effects of causal variants are small on average. 相似文献
962.
5-Oxo-ETE (5-oxo-6,8,11,14-eicosatetraenoic acid) is formed from the 5-lipoxygenase product 5-HETE (5S-hydroxy-6,8,11,14-eicosatetraenoic acid) by 5-hydroxyeicosanoid dehydrogenase (5-HEDH). The cofactor NADP+ is a limiting factor in the synthesis of 5-oxo-ETE because of its low concentrations in unperturbed cells. Activation of the respiratory burst in phagocytic cells, oxidative stress, and cell death all dramatically elevate both intracellular NADP+ levels and 5-oxo-ETE synthesis. 5-HEDH is widely expressed in inflammatory, structural, and tumor cells. Cells devoid of 5-lipoxygenase can synthesize 5-oxo-ETE by transcellular biosynthesis using inflammatory cell-derived 5-HETE. 5-Oxo-ETE is a chemoattractant for neutrophils, monocytes, and basophils and promotes the proliferation of tumor cells. However, its primary target appears to be the eosinophil, for which it is a highly potent chemoattractant. The actions of 5-oxo-ETE are mediated by the highly selective OXE receptor, which signals by activating various second messenger pathways through the release of the βγ-dimer from Gi/o proteins to which it is coupled. Because of its potent effects on eosinophils, 5-oxo-ETE may be an important mediator in asthma, and, because of its proliferative effects, may also contribute to tumor progression. Selective OXE receptor antagonists, which are currently under development, could be useful therapeutic agents in asthma and other allergic diseases. 相似文献
963.
Lindsey Powell 《Visual Anthropology: Published in cooperation with the Commission on Visual Anthropology》2013,26(1):65-90
Japanese television networks regularly broadcast a number of popular travel programs that present a highly problematic, ethnocentric, and racist worldview. Especially troubling is the fact that this genre reinforces a notion of Japanese superiority in relation to so-called "naked tribes." The "primitives" are brought to Japan, bathed, clothed, given a few yen, and sent to the mall to learn how to be modern consumers. This article briefly explores the history of ideologies of travel in Japan and how they tend to reinforce a problematic relationship with foreigners, especially people from the Third World; then describes and criticizes two contemporary television programs, Secret Region and Japan!! and World Tearful Sojourn Diary . 相似文献
964.
965.
966.
Introduction
In contrast to the defence mechanism of RNA interference (RNAi) in plants and invertebrates, its role in the innate response to virus infection of mammals is a matter of debate. Since RNAi has a well-established role in controlling infection of the alphavirus Sindbis virus (SINV) in insects, we have used this virus to investigate the role of RNAi in SINV infection of human cells.Results
SINV AR339 and TR339-GFP were adapted to grow in HEK293 cells. Deep sequencing of small RNAs (sRNAs) early in SINV infection (4 and 6 hpi) showed low abundance (0.8%) of viral sRNAs (vsRNAs), with no size, sequence or location specific patterns characteristic of Dicer products nor did they possess any discernible pattern to ascribe to a specific RNAi biogenesis pathway. This was supported by multiple variants for each sequence, and lack of hot spots along the viral genome sequence. The abundance of the best defined vsRNAs was below the limit of Northern blot detection. The adaptation of the virus to HEK293 cells showed little sequence changes compared to the reference; however, a SNP in E1 gene with a preference from G to C was found.Deep sequencing results showed little variation of expression of cellular microRNAs (miRNAs) at 4 and 6 hpi compared to uninfected cells. Twelve miRNAs exhibiting some minor differential expression by sequencing, showed no difference in expression by Northern blot analysis.Conclusions
We show that, unlike SINV infection of invertebrates, generation of Dicer-dependent svRNAs and change in expression of cellular miRNAs were not detected as part of the Human response to SINV. 相似文献967.
M.N. Greco M.A. Connelly G.C. Leo M.W. Olson E. Powell Z. Huang M. Hawkins C. Smith C. Schalk-Hihi A.L. Darrow H. Xin W. Lang B.P. Damiano D.J. Hlasta 《Bioorganic & medicinal chemistry letters》2013,23(9):2595-2597
By screening directed libraries of serine hydrolase inhibitors using the cell surface form of endothelial lipase (EL), we identified a series of carbamate-derived (EL) inhibitors. Compound 3 raised plasma HDL-C levels in the mouse, and a correlation was found between HDL-C and plasma compound levels. Spectroscopic and kinetic studies support a covalent mechanism of inhibition. Our findings represent the first report of EL inhibition as an effective means for increasing HDL-C in an in vivo model. 相似文献
968.
Ford SE Paterno J Scarpa E Stokes NA Kim Y Powell EN Bushek D 《Diseases of aquatic organisms》2011,93(3):251-256
The advent of molecular detection assays has provided a set of very sensitive tools for the detection of pathogens in marine organisms, but it has also raised problems of how to interpret positive signals that are not accompanied by visual confirmation. PCR-positive results have recently been reported for Haplosporidium nelsoni (MSX), a pathogen of the oyster Crassostrea virginica in 31 of 40 oysters from 6 sites in the Gulf of Mexico and the Caribbean Sea. Histological confirmation of the PCR results was not undertaken, and no haplosporidian has been reported from the numerous histological studies and surveys of oysters in the region. To further investigate the possibility that H. nelsoni is present in this region, we sampled 210 oysters from 40 sites around the Gulf of Mexico and Puerto Rico using PCR and 180 of these using tissue-section histology also. None of the oysters showed evidence of H. nelsoni by PCR or of any haplosporidian by histology. We cannot, therefore, confirm that H. nelsoni is present and widespread in the Gulf of Mexico and the Caribbean Sea. Our results do not prove that H. nelsoni is absent from the region, but taken together with results from previous histological surveys, they suggest that for the purposes of controlling oyster importation, the region should continue to be considered free of the parasite. 相似文献
969.
970.
Treatment of the ammonia adduct of tris(pentafluorophenyl)borane with 1.5 equivalents of pyrimidine affords a crystalline supramolecular complex. The solid state structure of the chloroform solvate has been determined by X-ray crystallography and is composed of two interpenetrating chiral (10,3)-a (srs) nets assembled through N-H?N hydrogen bonding interactions. 相似文献