全文获取类型
收费全文 | 17399篇 |
免费 | 1525篇 |
国内免费 | 1382篇 |
出版年
2024年 | 48篇 |
2023年 | 231篇 |
2022年 | 569篇 |
2021年 | 898篇 |
2020年 | 608篇 |
2019年 | 714篇 |
2018年 | 745篇 |
2017年 | 589篇 |
2016年 | 720篇 |
2015年 | 1061篇 |
2014年 | 1225篇 |
2013年 | 1357篇 |
2012年 | 1598篇 |
2011年 | 1359篇 |
2010年 | 803篇 |
2009年 | 712篇 |
2008年 | 932篇 |
2007年 | 801篇 |
2006年 | 716篇 |
2005年 | 613篇 |
2004年 | 534篇 |
2003年 | 463篇 |
2002年 | 435篇 |
2001年 | 364篇 |
2000年 | 307篇 |
1999年 | 286篇 |
1998年 | 215篇 |
1997年 | 187篇 |
1996年 | 172篇 |
1995年 | 150篇 |
1994年 | 146篇 |
1993年 | 114篇 |
1992年 | 109篇 |
1991年 | 113篇 |
1990年 | 84篇 |
1989年 | 61篇 |
1988年 | 58篇 |
1987年 | 35篇 |
1986年 | 33篇 |
1985年 | 31篇 |
1984年 | 46篇 |
1983年 | 27篇 |
1982年 | 14篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1971年 | 3篇 |
1968年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Z Zhong A Toukdarian D Helinski V Knauf S Sykes J E Wilkinson C O'Bryne T Shea C DeLoughery R Caspi 《Applied and environmental microbiology》2001,67(12):5771-5779
An agar-degrading marine bacterium identified as a Microscilla species was isolated from coastal California marine sediment. This organism harbored a single 101-kb circular DNA plasmid designated pSD15. The complete nucleotide sequence of pSD15 was obtained, and sequence analysis indicated a number of genes putatively encoding a variety of enzymes involved in polysaccharide utilization. The most striking feature was the occurrence of five putative agarase genes. Loss of the plasmid, which occurred at a surprisingly high frequency, was associated with loss of agarase activity, supporting the sequence analysis results. 相似文献
3.
4.
Food availability is important to the dynamics of animal social organizations or populations. However, the role of winter
food availability in animal population dynamics is still controversial. We carried out an experimental study to test Lack’s
hypothesis that reduced food in winter limits survival and spring numbers of breeding individuals of social groups, using
the Mongolian gerbil (Meriones unguiculatus) as model species. We established 24 gerbil social groups in 24, 10 × 10 m, pens in September 2008. We provided wheat seeds
as supplemental food in 12 enclosures from September 2008 to March 2009; the other 12 enclosures, not provided with supplemental
food, served as controls. We live-trapped gerbils at a 2-week interval from September to April. Supplemental food during winter
increased biweekly survival by 10% relative to that in control groups. Only four control social groups survived to the end
of our study whereas all 12 food-supplemented social groups survived through our study period. Supplemental food also increased
cumulative numbers of recruits and group sizes of gerbils. We conclude that winter food availability limits winter survival
and spring social groups or population sizes of Mongolian gerbils. 相似文献
5.
Yunfan Sun Liang Wu Yu Zhong Kaiqian Zhou Yong Hou Zifei Wang Zefan Zhang Jiarui Xie Chunqing Wang Dandan Chen Yaling Huang Xiaochan Wei Yinghong Shi Zhikun Zhao Yuehua Li Ziwei Guo Qichao Yu Liqin Xu Jia Fan 《Cell》2021,184(2):404-421.e16
- Download : Download high-res image (233KB)
- Download : Download full-size image
6.
7.
8.
9.
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
10.