全文获取类型
收费全文 | 12630篇 |
免费 | 1263篇 |
国内免费 | 3篇 |
出版年
2021年 | 141篇 |
2020年 | 89篇 |
2019年 | 111篇 |
2018年 | 122篇 |
2017年 | 132篇 |
2016年 | 263篇 |
2015年 | 345篇 |
2014年 | 413篇 |
2013年 | 588篇 |
2012年 | 670篇 |
2011年 | 695篇 |
2010年 | 476篇 |
2009年 | 480篇 |
2008年 | 624篇 |
2007年 | 672篇 |
2006年 | 614篇 |
2005年 | 607篇 |
2004年 | 595篇 |
2003年 | 626篇 |
2002年 | 595篇 |
2001年 | 289篇 |
2000年 | 256篇 |
1999年 | 236篇 |
1998年 | 202篇 |
1997年 | 157篇 |
1996年 | 144篇 |
1995年 | 156篇 |
1994年 | 133篇 |
1993年 | 107篇 |
1992年 | 201篇 |
1991年 | 176篇 |
1990年 | 155篇 |
1989年 | 165篇 |
1988年 | 155篇 |
1987年 | 127篇 |
1986年 | 110篇 |
1985年 | 114篇 |
1984年 | 132篇 |
1983年 | 94篇 |
1982年 | 116篇 |
1981年 | 88篇 |
1980年 | 102篇 |
1979年 | 126篇 |
1978年 | 90篇 |
1977年 | 88篇 |
1976年 | 98篇 |
1975年 | 94篇 |
1974年 | 84篇 |
1973年 | 80篇 |
1972年 | 78篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The health profile of cloned animals. 总被引:17,自引:0,他引:17
2.
Maurice Campbell 《BMJ (Clinical research ed.)》1948,2(4579):669-671
3.
Alain Dejean Arthur Compin Jacques H. C. Delabie Frdric Azmar Bruno Corbara Maurice Leponce 《Ecological Entomology》2019,44(4):560-570
1. Ants are widespread in tropical rainforests, including in the canopy where territorially dominant arboreal species represent the main part of the arthropod biomass. 2. By mapping the territories of dominant arboreal ant species and using a null model analysis and a pairwise approach this study was able to show the presence of an ant mosaic on the upper canopy of a primary Neotropical rainforest (c. 1 ha sampled; 157 tall trees from 28 families). Although Neotropical rainforest canopies are frequently irregular, with tree crowns at different heights breaking the continuity of the territories of dominant ants, the latter are preserved via underground galleries or trails laid on the ground. 3. The distribution of the trees influences the structure of the ant mosaic, something related to the attractiveness of tree taxa for certain arboreal ant species rather than others. 4. Small‐scale natural disturbances, most likely strong winds in the area studied (presence of canopy gaps), play a role by favouring the presence of two ant species typical of secondary formations: Camponotus femoratus and Crematogaster levior, which live in parabiosis (i.e. share territories and nests but lodge in different cavities) and build conspicuous ant gardens. In addition, pioneer Cecropia myrmecophytic trees were recorded. 相似文献
4.
Background
In heterogeneous environments, sex-biased dispersal could lead to environmental adaptive parental effects, with offspring selected to perform in the same way as the parent dispersing least, because this parent is more likely to be locally adapted. We investigate this hypothesis by simulating varying levels of sex-biased dispersal in a patchy environment. The relative advantage of a strategy involving pure maternal (or paternal) inheritance is then compared with a strategy involving classical biparental inheritance in plants and in animals. 相似文献5.
Use of ATP bioluminescence measurements for the estimation of biomass during biological humification
Summary The development of the microflora during the humification of grape pulp has been investigated by the determination of ATP using the bioluminescence technique. Several extraction methods were tested including the use of dimethylsulphoxide, trichloroacetic acid, grinding and ultrasonification. Dimethylsulphoxide and ultrasonification for 15 sec appeared to be the most effective. The ATP extract was stabilized when it was mixed with 0.75 mM glycine, 4.4 mM Mg-EDTA, pH 7.5 and frozen. The relative error of the ATP assay by bioluminescence did not exceed 6.5%. This method allowed us to show that at least five distinct reproducible microbial phases exist during grape pulp humification. These results show that the microbial biomass changes noticeably and at distinct times during composting. 相似文献
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