全文获取类型
收费全文 | 54716篇 |
免费 | 4994篇 |
国内免费 | 30篇 |
出版年
2022年 | 403篇 |
2021年 | 836篇 |
2020年 | 493篇 |
2019年 | 637篇 |
2018年 | 782篇 |
2017年 | 727篇 |
2016年 | 1130篇 |
2015年 | 1957篇 |
2014年 | 2120篇 |
2013年 | 2805篇 |
2012年 | 3552篇 |
2011年 | 3604篇 |
2010年 | 2364篇 |
2009年 | 2098篇 |
2008年 | 3019篇 |
2007年 | 3119篇 |
2006年 | 3010篇 |
2005年 | 2883篇 |
2004年 | 2792篇 |
2003年 | 2686篇 |
2002年 | 2566篇 |
2001年 | 596篇 |
2000年 | 511篇 |
1999年 | 668篇 |
1998年 | 813篇 |
1997年 | 596篇 |
1996年 | 523篇 |
1995年 | 477篇 |
1994年 | 467篇 |
1993年 | 492篇 |
1992年 | 521篇 |
1991年 | 445篇 |
1990年 | 429篇 |
1989年 | 411篇 |
1988年 | 391篇 |
1987年 | 361篇 |
1986年 | 365篇 |
1985年 | 411篇 |
1984年 | 484篇 |
1983年 | 391篇 |
1982年 | 510篇 |
1981年 | 514篇 |
1980年 | 410篇 |
1979年 | 337篇 |
1978年 | 347篇 |
1977年 | 305篇 |
1976年 | 337篇 |
1975年 | 228篇 |
1974年 | 285篇 |
1973年 | 280篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
93.
94.
95.
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
96.
97.
98.
99.
Summary The kinetics of thermal deactivation for thermostable DNA polymerase enzymes were investigated by using the experimental data published elsewhere (Nielson et al. 1996. Strategies. 9, 7–8). The order of deactivation (a) and the deactivation rate constants (k
d) were determined for different Taq DNA polymerase enzymes and were found to be of first order. 相似文献
100.
Bruce Y. Lee Sarah M. Bartsch Marie C. Ferguson Patrick T. Wedlock Kelly J. OShea Sheryl S. Siegmund Sarah N. Cox James A. McKinnell 《PLoS computational biology》2021,17(1)
Finding medications or vaccines that may decrease the infectious period of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) could potentially reduce transmission in the broader population. We developed a computational model of the U.S. simulating the spread of SARS-CoV-2 and the potential clinical and economic impact of reducing the infectious period duration. Simulation experiments found that reducing the average infectious period duration could avert a median of 442,852 [treating 25% of symptomatic cases, reducing by 0.5 days, reproductive number (R0) 3.5, and starting treatment when 15% of the population has been exposed] to 44.4 million SARS-CoV-2 cases (treating 75% of all infected cases, reducing by 3.5 days, R0 2.0). With R0 2.5, reducing the average infectious period duration by 0.5 days for 25% of symptomatic cases averted 1.4 million cases and 99,398 hospitalizations; increasing to 75% of symptomatic cases averted 2.8 million cases. At $500/person, treating 25% of symptomatic cases saved $209.5 billion (societal perspective). Further reducing the average infectious period duration by 3.5 days averted 7.4 million cases (treating 25% of symptomatic cases). Expanding treatment to 75% of all infected cases, including asymptomatic infections (R0 2.5), averted 35.9 million cases and 4 million hospitalizations, saving $48.8 billion (societal perspective and starting treatment after 5% of the population has been exposed). Our study quantifies the potential effects of reducing the SARS-CoV-2 infectious period duration. 相似文献