全文获取类型
收费全文 | 26067篇 |
免费 | 2366篇 |
国内免费 | 57篇 |
出版年
2021年 | 310篇 |
2020年 | 190篇 |
2019年 | 252篇 |
2018年 | 316篇 |
2017年 | 267篇 |
2016年 | 441篇 |
2015年 | 780篇 |
2014年 | 876篇 |
2013年 | 1279篇 |
2012年 | 1489篇 |
2011年 | 1446篇 |
2010年 | 909篇 |
2009年 | 863篇 |
2008年 | 1292篇 |
2007年 | 1349篇 |
2006年 | 1229篇 |
2005年 | 1216篇 |
2004年 | 1157篇 |
2003年 | 1117篇 |
2002年 | 1088篇 |
2001年 | 403篇 |
2000年 | 367篇 |
1999年 | 421篇 |
1998年 | 338篇 |
1997年 | 263篇 |
1996年 | 244篇 |
1995年 | 239篇 |
1994年 | 263篇 |
1993年 | 208篇 |
1992年 | 306篇 |
1991年 | 268篇 |
1990年 | 238篇 |
1989年 | 254篇 |
1988年 | 261篇 |
1987年 | 243篇 |
1986年 | 240篇 |
1985年 | 247篇 |
1984年 | 259篇 |
1983年 | 244篇 |
1982年 | 272篇 |
1981年 | 290篇 |
1980年 | 241篇 |
1979年 | 227篇 |
1978年 | 258篇 |
1977年 | 215篇 |
1976年 | 189篇 |
1975年 | 206篇 |
1974年 | 227篇 |
1973年 | 202篇 |
1968年 | 146篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
2.
3.
4.
The health profile of cloned animals. 总被引:17,自引:0,他引:17
5.
George John Acton 《Phytochemistry》1974,13(8):1303-1310
The light-dependent increment in RNase activity (which is ribosome bound in cell extracts) is distributed as a gradient increasing from base to hook of lupin hypocotyls. No evidence was found of non-specific or of specific activation of pre-formed enzyme molecules following isolation, either before or after (latent activity) destruction of particles. The autodegradation capacity of ribosomes isolated from irradiated cells was almost double that of ribosomes from etiolated tissue. It is proposed that association between the bulk of the light-controlled RNase fraction and lupin ribosomes results from binding of soluble protein. It is not clear whether binding is specific or an artifact of isolation. 相似文献
6.
E. Backe G. Lotz U. Tittelbach H. Thurmer E. Gierke N. Kersten A. Bernard G. Wallenstein W. D. Schneider 《Biomarkers》2000,5(2):119-128
The inflammation markers alpha-1-antitrypsin (AAT), Clara cell protein (CC-16), soluble interleukin-2-receptor (IL-R) and the soluble adhesion molecule E-selectin, the intercellular adhesion molecule (ICAM-1) and the vascular adhesion molecule (VCAM-1) were determined in the serum of 195 salt-exposed miners to analyse dose-response relationships between markers and potash dust. Alpha-1-antitrypsin, Clara-cell protein, IL2-R, E-selectin and VCAM-1 were not changed by salt exposure, however the ICAM-1 level in the serum fell slightly as the salt exposure increased. This effect was strongest in the group of smokers, still visible in the group of ex-smokers, no effect was seen in non-smokers. Markers, with the exception of VCAM-1, were influenced by tobacco exposure. Since markers were not elevated in relation to salt dust exposure, the results do not support an inflammatory effect of potash dust on the respiratory system. 相似文献
7.
John A. Schneider Rakhi Dandona Shravani Pasupneti Vemu Lakshmi Chuanhong Liao Vijay Yeldandi Kenneth H. Mayer 《PloS one》2010,5(7)
Studies of HIV prevention interventions such as pre-exposure prophylaxis (PREP) and circumcision in India are limited. The present study sought to investigate Indian truck-drivers initial commitment to PREP and circumcision utilizing the AIDS Risk Reduction Model. Ninety truck-drivers completed an in-depth qualitative interview and provided a blood sample for HIV and HSV-2 testing. Truck-drivers exhibited low levels of initial commitment towards PREP and even lower for circumcision. However, potential leverage points for increasing commitment were realized in fear of infecting family rather than self, self-perceptions of risk, and for PREP focusing on cultural beliefs towards medication and physicians. Cost was a major barrier to both HIV prevention interventions. Despite these barriers, our findings suggest that the ARRM may be useful in identifying several leverage points that may be used by peers, health care providers and public health field workers to enhance initial commitment to novel HIV prevention interventions in India. 相似文献
8.
9.
10.