全文获取类型
收费全文 | 17337篇 |
免费 | 1711篇 |
国内免费 | 6篇 |
出版年
2022年 | 131篇 |
2021年 | 247篇 |
2020年 | 168篇 |
2019年 | 189篇 |
2018年 | 253篇 |
2017年 | 218篇 |
2016年 | 436篇 |
2015年 | 619篇 |
2014年 | 735篇 |
2013年 | 881篇 |
2012年 | 1146篇 |
2011年 | 1155篇 |
2010年 | 730篇 |
2009年 | 681篇 |
2008年 | 911篇 |
2007年 | 949篇 |
2006年 | 851篇 |
2005年 | 868篇 |
2004年 | 843篇 |
2003年 | 800篇 |
2002年 | 771篇 |
2001年 | 322篇 |
2000年 | 272篇 |
1999年 | 265篇 |
1998年 | 251篇 |
1997年 | 182篇 |
1996年 | 168篇 |
1995年 | 168篇 |
1994年 | 170篇 |
1993年 | 140篇 |
1992年 | 205篇 |
1991年 | 185篇 |
1990年 | 160篇 |
1989年 | 176篇 |
1988年 | 164篇 |
1987年 | 148篇 |
1986年 | 123篇 |
1985年 | 136篇 |
1984年 | 131篇 |
1983年 | 128篇 |
1982年 | 147篇 |
1981年 | 101篇 |
1980年 | 94篇 |
1979年 | 129篇 |
1978年 | 106篇 |
1977年 | 88篇 |
1976年 | 99篇 |
1975年 | 92篇 |
1974年 | 84篇 |
1973年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Maurice Campbell 《BMJ (Clinical research ed.)》1948,2(4579):669-671
2.
Marianne E. Walsh Charles M. Collins Thomas F. Jenkins Alan D. Hewitt Jeff Stark Karen Myers 《Soil & Sediment Contamination》2003,12(5):631-645
Fort Greely, Alaska has an extensive complex of weapon training and testing areas located on lands withdrawn from the public domain under the Military Lands Withdrawal Act (PL106-65). The Army has pledged to implement a program to identify possible munitions contamination. Because of the large size (344,165,000 m2) of the high hazard impact areas, characterization of these constituents will be difficult. We used an authoritative sampling design to find locations most likely to contain explosives-residues on three impact areas. We focused our sampling on surface soils and collected multi-increment and discrete samples at locations of known firing events and from areas on the range that had craters, pieces of munitions, targets, or a designation as a firing point. In the two impact areas used primarily by the Army, RDX was the most frequently detected explosive. In the impact area that was also used by the Air Force, TNT was the most frequently detected explosive. Where detected, the explosives concentrations generally were low (<0.05 mg/kg) except in soils near low-order detonations, where the explosive-filler was in contact with the soil surface. These low-order detonations potentially can serve as localized sources for groundwater contamination if positioned in recharge areas. 相似文献
3.
4.
5.
6.
7.
8.
9.
10.
Susan Morrison Grace John-Stewart John J. Egessa Sezi Mubezi Sylvia Kusemererwa Dennis K. Bii Nulu Bulya Francis Mugume James D. Campbell Jonathan Wangisi Elizabeth A. Bukusi Connie Celum Jared M. Baeten Partners PrEP Study Team 《PloS one》2015,10(10)
During an HIV-1 prevention clinical trial in East Africa, we observed 16 cases of primary HIV-1 infection in women coincident with pregnancy or breastfeeding. Nine of eleven pregnant women initiated rapid combination antiretroviral therapy (ART), despite having CD4 counts exceeding national criteria for ART initiation; breastfeeding women initiated ART or replacement feeding. Rapid ART initiation during primary HIV-1 infection during pregnancy and breastfeeding is feasible in this setting. 相似文献