全文获取类型
收费全文 | 53260篇 |
免费 | 4896篇 |
国内免费 | 30篇 |
专业分类
58186篇 |
出版年
2022年 | 383篇 |
2021年 | 809篇 |
2020年 | 489篇 |
2019年 | 600篇 |
2018年 | 735篇 |
2017年 | 695篇 |
2016年 | 1111篇 |
2015年 | 1854篇 |
2014年 | 2064篇 |
2013年 | 2689篇 |
2012年 | 3420篇 |
2011年 | 3455篇 |
2010年 | 2244篇 |
2009年 | 2010篇 |
2008年 | 2852篇 |
2007年 | 3016篇 |
2006年 | 2902篇 |
2005年 | 2753篇 |
2004年 | 2661篇 |
2003年 | 2533篇 |
2002年 | 2407篇 |
2001年 | 602篇 |
2000年 | 501篇 |
1999年 | 654篇 |
1998年 | 777篇 |
1997年 | 585篇 |
1996年 | 511篇 |
1995年 | 464篇 |
1994年 | 448篇 |
1993年 | 474篇 |
1992年 | 530篇 |
1991年 | 442篇 |
1990年 | 451篇 |
1989年 | 433篇 |
1988年 | 421篇 |
1987年 | 364篇 |
1986年 | 384篇 |
1985年 | 416篇 |
1984年 | 499篇 |
1983年 | 403篇 |
1982年 | 498篇 |
1981年 | 531篇 |
1980年 | 412篇 |
1979年 | 352篇 |
1978年 | 365篇 |
1977年 | 316篇 |
1976年 | 352篇 |
1975年 | 238篇 |
1974年 | 312篇 |
1973年 | 287篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
Michitaro Nagasawa James Amigo Chan Charles J. Sih 《Prostaglandins & other lipid mediators》1974,8(3):221-230
Prostaglandins E1, F1α and A2 were covalently joined to the surface of Sepharose as carboxamide linkages. The insolubilized prostaglandins were shown to function effectively in the purification of 15(S) -hydroxyprostaglandin dehydrogenase. 相似文献
93.
94.
Serotyping is the foundation of pathogenic Escherichia coli diagnostics; however, few laboratories have this capacity. We developed a molecular serotyping protocol that targets, genetically, the same somatic and flagellar antigens of E. coli O26:H11 used in traditional serotyping. It correctly serotypes strains untypeable by traditional methods, affording primary laboratories serotyping capabilities. 相似文献
95.
Richard P. Duncan 《Biological invasions》2016,18(4):985-996
Both the size of founding populations (propagule size) and environmental suitability are known to influence whether a species newly introduced to a location will establish a self-sustaining population. However, these two factors do not operate independently: it is the interaction between propagule size and environmental suitability that determines the probability an introduced population will establish. Here I use the example of dung beetle introductions to Australia to illustrate the importance of this interaction. I first describe equations that model establishment success jointly as a function of propagule size and environmental suitability. I then show how these equations provide insight into the different outcomes observed in two dung beetle species widely introduced to Australia. In one species, variation in propagule size had relatively little influence on establishment success due to large variation in environmental suitability, leading to an essentially bimodal outcome: sites were either very suitable for establishment and introductions succeeded, or sites were unsuitable and introductions failed regardless of propagule size. For the second species, there was much less variation among locations in environmental suitability, leading to propagule size having a strong influence on establishment success. These examples highlight how the interplay between environmental suitability and founding population size is central to determining the probability an introduced species will establish. 相似文献
96.
97.
Nutrition and fat production in submerged cultures of a strain of Penicillium lilacinum 总被引:1,自引:0,他引:1
B Duncan 《Mycologia》1973,65(1):211-214
98.
99.
100.
E. coli cells containing a temperature-sensitivednaE mutation, in the α-subunit of holoenzyme DNA polymerase III, do not survive at the restrictive temperature. Such cells may
survive in the presence of thepcbA1 mutation, an allele of thegyrB gene. Such survival is dependent on an active DNA polymerase I. Evidence indicates that DNA polymerase I interacts directly
in the replisome (REP·A). Despite normal survival for cells using thepcbA replication pathway after some type of DNA damage, we have noted a failure of damage-induced mutagenesis. Here we present
evidence supporting a model of replisome pausing in cells dependent upon thepcbA replication pathway. The model argues that the (REP·A) complex pauses longer at the site of the lesion, allowing excision
repair to occur completely. In the normal replication pathway (REP·E) bypass of the lesion occurs, fixing the mutation. 相似文献