全文获取类型
收费全文 | 21255篇 |
免费 | 1749篇 |
国内免费 | 2259篇 |
出版年
2024年 | 75篇 |
2023年 | 356篇 |
2022年 | 811篇 |
2021年 | 1238篇 |
2020年 | 876篇 |
2019年 | 1044篇 |
2018年 | 958篇 |
2017年 | 745篇 |
2016年 | 945篇 |
2015年 | 1355篇 |
2014年 | 1553篇 |
2013年 | 1647篇 |
2012年 | 2029篇 |
2011年 | 1785篇 |
2010年 | 1028篇 |
2009年 | 912篇 |
2008年 | 1172篇 |
2007年 | 931篇 |
2006年 | 841篇 |
2005年 | 732篇 |
2004年 | 628篇 |
2003年 | 512篇 |
2002年 | 435篇 |
2001年 | 373篇 |
2000年 | 315篇 |
1999年 | 305篇 |
1998年 | 208篇 |
1997年 | 189篇 |
1996年 | 161篇 |
1995年 | 166篇 |
1994年 | 143篇 |
1993年 | 111篇 |
1992年 | 110篇 |
1991年 | 116篇 |
1990年 | 97篇 |
1989年 | 85篇 |
1988年 | 56篇 |
1987年 | 39篇 |
1986年 | 38篇 |
1985年 | 38篇 |
1984年 | 30篇 |
1983年 | 34篇 |
1982年 | 16篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1968年 | 2篇 |
1966年 | 2篇 |
1950年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
1.
2.
3.
Plants of four isolines of soyabean [Glycine max(L.) Merrill]Clark, vizL71-920 (maturity genecomplemente1e2e3 ), L80-5914 (E1e2e3), Clark(e1E2E3), and L65-3366 (E1E2E3), were grown inshort (12.25 h d - 1natural light) and long days (12.25 h d- 1natural light supplemented with 2.75 h d - 1low-irradianceartificial light) from first flowering to maturity in a polythenetunnel maintained at 30/24°C (day/night). Whereas therewere few differences among the isolines grown in short days,in long days the dominant alleles increased crop duration, biomassand seed yield substantially. Increases in biological and economicyield were not solely a consequence of longer crop duration:the dominant alleles also increased crop growth rate and radiationuse efficiency in long days (from 1.3 g MJ - 1total radiationine1e2e3 to 2.8 g MJ - 1inE1E2E3 ). Greater radiation use efficiencyresulted from a relatively longer leaf area duration, betterdistribution and orientation of a larger mass of leaves withinthe canopy, and smaller partitioning of assimilates to reproductivestructures. The work reveals the substantial effects of thethree lociE1 / e1, E2/ e2and E3/e3 on the response of plantgrowth, as well as development, to environment. Their relevanceto crop adaptation is discussed. Copyright 2000 Annals of BotanyCompany Glycine max(L.) Merrill, soyabean, maturity genes, flowering, phenology, growth, yield 相似文献
4.
<正>Aristolochic acids, mutational signature, and hepatocellular carcinoma Aristolochic acids (AA) are the etiologic agents of aristolochic acid nephropathy (AAN) and contribute to the global prevalence of chronic kidney disease and urothelial cancer (Grollman et al., 2007). DNA adducts formed by AA generate a unique AT transversions mutation spectrum at 相似文献
5.
6.
Caitlin M. Cossaboom Laura Córdoba Dianjun Cao Yan-Yan Ni Xiang-Jin Meng 《Journal of virology》2012,86(23):13124-13125
Hepatitis E virus (HEV) is a single-strand positive-sense RNA virus in the family Hepeviridae. The disease caused by HEV, hepatitis E, is an important public health problem in developing countries of Asia and Africa and is also endemic in many industrialized countries, including the United States. HEV has been identified from several other animal species in addition to humans, including the pig, chicken, mongoose, deer, rabbit, ferret, bat, and fish. Here we report the complete genome sequence of the first strain of HEV from rabbits in the United States. Sequence and phylogenetic analyses revealed that the U.S. rabbit HEV is a distant member of the zoonotic genotype 3 HEV, thus raising a concern for potential zoonotic human infection. A unique 90-nucleotide insertion within the X domain of the ORF1 was identified in the rabbit HEV, and this insertion may play a role in the species tropism of HEV. 相似文献
7.
8.
Fei Mi Ying Zhang Dan Yang Xiaozhao Tang Pengfei Wang Xiaoxia He Yunrun Zhang Jianyong Dong Yang Cao Chunli Liu Ke-Qin Zhang Jianping Xu 《PloS one》2016,11(2)
During the past 40 years, more than 400 Sudden Unexplained Deaths (SUDs) have occurred in Yunnan, southwestern China. Epidemiological and toxicological analyses suggested that a newly discovered mushroom called Trogia venenata was the leading culprit for SUDs. At present, relatively little is known about the genetics and natural history of this mushroom. In this study, we analyzed the sequence variation at four DNA fragments among 232 fruiting bodies of T. venenata collected from seven locations. Our ITS sequence analyses confirmed that all the isolates belonged to the same species. The widespread presence of sequence heterozygosity within many strains at each of three protein-coding genes suggested that the fruiting bodies were diploid, dikaryotic or heterokaryotic. Within individual geographic populations, we found significant deviations of genotype frequencies from Hardy-Weinberg expectations, with the overall observed heterozygosity lower than that expected under random mating, consistent with prevalent inbreeding within local populations. The geographic populations were overall genetically differentiated. Interestingly, while a positive correlation was found between population genetic distance and geographic distance, there was little correlation between genetic distance and barium concentration difference for the geographic populations. Our results suggest frequent inbreeding, geographic structuring, and limited gene flow among geographic populations of T. venenata from southwestern China. 相似文献
9.
10.
贝壳历来是生物工程和材料学研究的重要对象。贝壳中的贝壳基质蛋白质在贝壳的形成与发育过程中具有重要的调控作用。Whirlin类蛋白质(Whirlin-like protein,WLP)是一种从厚壳贻贝(Mytilus coruscus)中鉴定的新型贝壳基质蛋白质。序列分析结果显示,该蛋白质含有PDZ(postsynaptic density/Discs large/Zonula occludens)结构域,而该结构域对贝壳生物矿化的影响目前尚无报道。为深入了解WLP在贝壳形成中对碳酸钙晶体的影响,在序列分析基础上,采用密码子优化结合原核重组表达,获得其重组表达产物后,开展了重组WLP对碳酸钙晶体形貌及晶型的影响研究,结晶速度抑制以及碳酸钙晶体结合分析。分析结果表明,重组WLP能诱导文石型碳酸钙晶体的形貌和方解石型碳酸钙晶体的晶型发生改变;同时重组WLP对碳酸钙晶体具有结合作用,且能抑制碳酸钙晶体的结晶速度。上述结果表明,WLP对贝壳的形成及发育具有重要影响,并可能在贝壳肌棱柱层的形成中发挥了重要作用。 相似文献