全文获取类型
收费全文 | 58634篇 |
免费 | 4895篇 |
国内免费 | 84篇 |
专业分类
63613篇 |
出版年
2023年 | 215篇 |
2022年 | 616篇 |
2021年 | 1062篇 |
2020年 | 596篇 |
2019年 | 809篇 |
2018年 | 1212篇 |
2017年 | 966篇 |
2016年 | 1660篇 |
2015年 | 2718篇 |
2014年 | 3029篇 |
2013年 | 3549篇 |
2012年 | 4563篇 |
2011年 | 4353篇 |
2010年 | 2771篇 |
2009年 | 2447篇 |
2008年 | 3447篇 |
2007年 | 3233篇 |
2006年 | 2948篇 |
2005年 | 2674篇 |
2004年 | 2589篇 |
2003年 | 2311篇 |
2002年 | 1996篇 |
2001年 | 1671篇 |
2000年 | 1563篇 |
1999年 | 1252篇 |
1998年 | 543篇 |
1997年 | 488篇 |
1996年 | 416篇 |
1995年 | 403篇 |
1994年 | 315篇 |
1993年 | 303篇 |
1992年 | 643篇 |
1991年 | 528篇 |
1990年 | 481篇 |
1989年 | 484篇 |
1988年 | 410篇 |
1987年 | 396篇 |
1986年 | 321篇 |
1985年 | 333篇 |
1984年 | 274篇 |
1983年 | 227篇 |
1982年 | 189篇 |
1981年 | 163篇 |
1980年 | 160篇 |
1979年 | 224篇 |
1978年 | 199篇 |
1977年 | 181篇 |
1976年 | 173篇 |
1974年 | 199篇 |
1972年 | 156篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Avian oviductal fluids contain phosphorylating-dephosphorylating enzymes that might function in sperm-oocyte interactions. Phosphorprotein phosphatase and protein kinase have been purified 20-fold and 40-fold, respectively. The latter easily aggregates and is highly labile. Other properties are comparable to those of holoenzymes. 相似文献
72.
73.
74.
75.
76.
77.
88 rice and 75 soybean samples were collected from 8 provinces of Korea from March through September in 1988. The Fusarium mycotoxins, zearalenone was analyzed by direct competitive enzyme linked immunosorbent assay. 10.2% of rice and 9.3 % of soybean samples contained detectable zearalenone. The average levels of zearalenone of rice and soybean samples were 11.78μg/kg and 7.70μ/kg, respectively. 相似文献
78.
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
79.
80.