全文获取类型
收费全文 | 1440220篇 |
免费 | 137894篇 |
国内免费 | 1446篇 |
专业分类
1579560篇 |
出版年
2021年 | 17945篇 |
2019年 | 16148篇 |
2018年 | 17803篇 |
2017年 | 16511篇 |
2016年 | 28212篇 |
2015年 | 42577篇 |
2014年 | 50603篇 |
2013年 | 76846篇 |
2012年 | 39032篇 |
2011年 | 27805篇 |
2010年 | 43947篇 |
2009年 | 45273篇 |
2008年 | 26358篇 |
2007年 | 24658篇 |
2006年 | 29540篇 |
2005年 | 30529篇 |
2004年 | 29812篇 |
2003年 | 27281篇 |
2002年 | 25261篇 |
2001年 | 38431篇 |
2000年 | 36205篇 |
1999年 | 35061篇 |
1998年 | 25987篇 |
1997年 | 25993篇 |
1996年 | 25470篇 |
1995年 | 23645篇 |
1994年 | 23451篇 |
1993年 | 22662篇 |
1992年 | 30844篇 |
1991年 | 29491篇 |
1990年 | 28162篇 |
1989年 | 28587篇 |
1988年 | 26465篇 |
1987年 | 25214篇 |
1986年 | 24061篇 |
1985年 | 25912篇 |
1984年 | 25038篇 |
1983年 | 22164篇 |
1982年 | 21923篇 |
1981年 | 21213篇 |
1980年 | 19751篇 |
1979年 | 21724篇 |
1978年 | 19804篇 |
1977年 | 18866篇 |
1976年 | 17972篇 |
1975年 | 17821篇 |
1974年 | 18267篇 |
1973年 | 18550篇 |
1972年 | 16124篇 |
1971年 | 14505篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
983.
Y. Crouau 《Behavioural processes》1985,11(1):21-30
The cavernicolous crustacean Antromysis juberthiei showed unexpected behavior when presented with food extract : it avoids the area of odor inflow. This avoidance reaction is reduced by removal of various combinations of antennae and disappears almost with bilateral removal of the first antennae (the aesthetasc-bearing antennules). 相似文献
984.
985.
Summary The ability of microorganisms to produce hydantoinase and L-N-carbamoylase could be established by an overlay assay. Enzyme producing strains form clear areas around their colonies caused by the cleavage of D,L-indolylmethylhydantoin. A second overlayer with a tryptophan-auxotroph yeast enables us to detect microorganisms which are able to produce L-tryptophan from D,L-indolylmethylhydantoin. 相似文献
986.
A C Srivastava A J Pinching M W Adler R Robertson R Higgs 《BMJ (Clinical research ed.)》1987,294(6570):495-496
Dr A C Srivastava has written to us to describe a case that raises the suggestion that people infected with the human immuno-deficiency virus (HIV) should carry identity cards. We asked two physicians, a general practitioner working with patients with the acquired immune deficiency syndrome (AIDS), and a general practitioner with a special interest in medical ethics to respond to the broad issues raised by Dr Srivastava''s letter. 相似文献
987.
Verapamil is a calcium-channel blocking agent, commonly used for chronic treatment of heart conditions. We have previously demonstrated that verapamil acts as a co-mutagen in a bacterial mutagenicity test for some experimental anilinoacridine antitumour drugs. Within the anilinoacridines series there are several compounds which are apparently non-mutagenic (or very weak mutagens) in the absence of verapamil, but strong mutagens in its presence. We have now tested a wider range of materials for verapamil enhancement of mutagenicity, to include some of those to which persons on verapamil therapy might be exposed through life-style or occupation. Some verapamil enhancement of mutagenicity was seen with most mutagenic compounds including anticancer drugs, antiparasitic agents, one biological stain and one hair dye. A number of tricyclic antidepressants and biological stains were tested and found to be non-mutagenic. If these results extrapolate to mammalian cells, long-term verapamil therapy could potentially increase the effects of certain environmental mutagens. 相似文献
988.
989.
990.