全文获取类型
收费全文 | 34315篇 |
免费 | 2871篇 |
国内免费 | 10篇 |
出版年
2023年 | 193篇 |
2022年 | 424篇 |
2021年 | 834篇 |
2020年 | 561篇 |
2019年 | 706篇 |
2018年 | 845篇 |
2017年 | 762篇 |
2016年 | 1094篇 |
2015年 | 1507篇 |
2014年 | 1725篇 |
2013年 | 2057篇 |
2012年 | 2348篇 |
2011年 | 2222篇 |
2010年 | 1380篇 |
2009年 | 1200篇 |
2008年 | 1547篇 |
2007年 | 1577篇 |
2006年 | 1364篇 |
2005年 | 1315篇 |
2004年 | 1246篇 |
2003年 | 1095篇 |
2002年 | 1048篇 |
2001年 | 733篇 |
2000年 | 668篇 |
1999年 | 583篇 |
1998年 | 314篇 |
1997年 | 267篇 |
1996年 | 264篇 |
1995年 | 216篇 |
1994年 | 252篇 |
1993年 | 212篇 |
1992年 | 381篇 |
1991年 | 357篇 |
1990年 | 328篇 |
1989年 | 330篇 |
1988年 | 310篇 |
1987年 | 353篇 |
1986年 | 275篇 |
1985年 | 281篇 |
1984年 | 270篇 |
1983年 | 231篇 |
1982年 | 191篇 |
1981年 | 183篇 |
1980年 | 168篇 |
1979年 | 235篇 |
1978年 | 208篇 |
1975年 | 181篇 |
1974年 | 175篇 |
1973年 | 176篇 |
1972年 | 177篇 |
排序方式: 共有10000条查询结果,搜索用时 56 毫秒
31.
32.
33.
34.
Household‐level correlates of children's physical activity levels in and across 12 countries
下载免费PDF全文
![点击此处可从《Obesity (Silver Spring, Md.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Deirdre M. Harrington Fiona Gillison Stephanie T. Broyles Jean‐Philippe Chaput Mikael Fogelholm Gang Hu Rebecca Kuriyan Anura Kurpad Allana G. LeBlanc Carol Maher Jose Maia Victor Matsudo Timothy Olds Vincent Onywera Olga L. Sarmiento Martyn Standage Mark S. Tremblay Catrine Tudor‐Locke Pei Zhao Peter T. Katzmarzyk for the ISCOLE Research Group 《Obesity (Silver Spring, Md.)》2016,24(10):2150-2157
35.
The TREX enzymes process DNA as the major 3′→5′ exonuclease activity in mammalian cells. TREX2 and TREX1 are members of the DnaQ family of exonucleases and utilize a two metal ion catalytic mechanism of hydrolysis. The structure of the dimeric TREX2 enzyme in complex with single-stranded DNA has revealed binding properties that are distinct from the TREX1 protein. The TREX2 protein undergoes a conformational change in the active site upon DNA binding including ordering of active site residues and a shift of an active site helix. Surprisingly, even when a single monomer binds DNA, both monomers in the dimer undergo the structural rearrangement. From this we have proposed a model for DNA binding and 3′ hydrolysis for the TREX2 dimer. The structure also shows how TREX proteins potentially interact with double-stranded DNA and suggest features that might be involved in strand denaturation to provide a single-stranded substrate for the active site. 相似文献
36.
37.
38.
Rachael V. Gallagher Lesley Hughes Michelle R. Leishman Peter D. Wilson 《Biological invasions》2010,12(12):4049-4063
Potential interactions between climate change and exotic plant invasions may affect areas of high conservation value, such
as land set aside for the protection of endangered species or ecological communities. We investigated this issue in eastern
Australia using species distribution models for five exotic vines under climate regimes for 2020 and 2050. We examined how
projected changes in the distribution of climatically suitable habitat may coincide with the remaining remnants of an endangered
ecological community—littoral rainforests—in this region. The number of known infestations of each weed in tropical, subtropical
and temperate areas was used to assess the likelihood of further expansion into areas projected to provide suitable habitat
under future conditions. Littoral rainforest reserves were consistently predicted to provide bioclimatically suitable habitat
for the five vines examined under both current and future climate scenarios. We explore the consequences and potential strategies
for managing exotic plant invasions in these protected areas in the coming decades. 相似文献
39.
Distinction between mouse DNA polymerases alpha and beta by tryptic peptide mapping. 总被引:2,自引:2,他引:0
Results presented here and in a previous paper (Tanabe et al. (1979) Biochemistry 18, 3401--3406) indicate that mouse beta-polymerase is a single polypeptide with an apparent molecular weight of 40,000. This polypeptide has now been analyzed by tryptic peptide mapping. Comparison of the results with identical analysis of mouse alpha-polymerase reveals that the tryptic peptides derived from the two enzymes are different. These results indicate that beta-polymerase is neither a subunit of alpha-polymerase nor a proteolytic degradation product of alpha-polymerase. 相似文献
40.