全文获取类型
收费全文 | 692945篇 |
免费 | 70512篇 |
国内免费 | 374篇 |
出版年
2018年 | 7214篇 |
2017年 | 7020篇 |
2016年 | 9340篇 |
2015年 | 11122篇 |
2014年 | 13650篇 |
2013年 | 19733篇 |
2012年 | 22296篇 |
2011年 | 22984篇 |
2010年 | 15711篇 |
2009年 | 14223篇 |
2008年 | 20246篇 |
2007年 | 20960篇 |
2006年 | 19730篇 |
2005年 | 18886篇 |
2004年 | 18726篇 |
2003年 | 17976篇 |
2002年 | 17443篇 |
2001年 | 34321篇 |
2000年 | 34137篇 |
1999年 | 26535篇 |
1998年 | 8276篇 |
1997年 | 8721篇 |
1996年 | 8059篇 |
1995年 | 7427篇 |
1994年 | 7153篇 |
1993年 | 7080篇 |
1992年 | 20855篇 |
1991年 | 20248篇 |
1990年 | 19608篇 |
1989年 | 19265篇 |
1988年 | 17618篇 |
1987年 | 16468篇 |
1986年 | 15276篇 |
1985年 | 15203篇 |
1984年 | 12374篇 |
1983年 | 10359篇 |
1982年 | 7539篇 |
1981年 | 6690篇 |
1980年 | 6424篇 |
1979年 | 11464篇 |
1978年 | 8775篇 |
1977年 | 8067篇 |
1976年 | 7477篇 |
1975年 | 8461篇 |
1974年 | 9182篇 |
1973年 | 8965篇 |
1972年 | 8112篇 |
1971年 | 7452篇 |
1970年 | 6455篇 |
1969年 | 6190篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
DNA was efficiently and quantitatively isolated from extremely small quantities of mycelia (0.1–10 mg) of different phytopathogenic
moulds by grinding freeze-dried mycelia with glass beads and then using a commercial DNA extraction kit. The efficiency of
disruption of the mycelia and the quantitative DNA extraction was proved by microscopy and the quantification of isolated
DNA by real time PCR.
Presented at the 27th Mykotoxin-Workshop, Dortmund, Germany, June 13–15, 2005
Financial support: German Research Foundation (DFG grant Pr 708/2). J.M. thanks the Cusanuswerk for a doctoral scholarship 相似文献
993.
This study evaluated the genetic consequences of a reintroduction of the endangered annual plant Cordylanthus maritimus ssp. maritimus to Sweetwater Marsh (San Diego County, California). A survey of 21 enzyme loci in natural populations revealed that genetic diversity is very low and is primarily found as rare alleles at a few loci, making this species especially susceptible to the loss of alleles and heterozygosity through genetic drift. The reintroduction was performed in 1991 and 1992 by sowing seeds (collected from Tijuana Estuary) in numerous small patches of suitable habitat. For this study, leaf tissue was collected from all plants in all patches during flowering in 1995 and surveyed for genotype at the three enzyme loci that are polymorphic at Tijuana Estuary. Rare alleles were absent in 27 out of 30 patches for Pgm-1, in 17 out of 30 patches for Pgm-2, and in 10 out of 11 patches for Mdh-1. In all, half of the patches lacked any rare allele. Rare alleles tended to occur in patches with few individuals. Overall rare allele frequency was lower than in the colonies from which seeds were collected at two of the three loci, and heterozygosity was reduced. The Sweetwater Marsh population is at risk of losing most of its genetic variation at enzyme loci through the extinction of patches with few individuals. Future reintroduction attempts should attempt to create contiguous sets of patches or to periodically reseed existing patches to reduce the loss of genetic variation. 相似文献
994.
995.
Chromosomal RNA: an artifact of preparation? 总被引:2,自引:0,他引:2
996.
997.
998.
L V Loskutova M A Gilinski? 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》1987,37(6):1070-1074
Character of conditioned reaction of passive avoidance was analyzed in Wistar line male rats after neurochemical destruction of terminal dopaminergic fields of the amygdalar complex. 6-hydroxydopamine was bilaterally administered to the central nucleus of the amygdalar complex after preliminary treating with desmethylimipramine for selective destruction of dopaminergic terminals. Lowering of dopamine level in the amygdalar complex led to a weakening of reproduction and to prolongation of spontaneous extinction of conditioned reaction. Features of conditioned reaction are highly similar to the effect of latent inhibition connected with attention deficit. It is suggested that activity of terminal fields of the amygdalar complex is one of the mechanisms providing for attention and intensifying selection of information in learning. 相似文献
999.
S Glazer M M Vartanova N N Konstantinova 《Biulleten' eksperimental'no? biologii i meditsiny》1985,100(10):414-415
Significant adverse correlation of the fetus mass and the degree of its hydration was noted at term in rats with placental insufficiency induced by ligation of about 40% of preplacental vessels on the 16th day of gestation. Disorders revealed in transplacental water-salt metabolism are apparently of some importance for the pathogenesis of fetal growth retardation. Even moderate retardation alters fetal respiratory activity in anoxia, which is associated with the changes in the function of respiratory centres and neuromuscular abnormalities. 相似文献
1000.
V I Sharapov I A Sokirchenko O R Grek V A Shkurupi? A V Dolgov 《Biulleten' eksperimental'no? biologii i meditsiny》1986,101(3):277-279
The experiments on rats have shown that total hepatic ischemia reduces the content of microsomal cytochromes P-450 and b5 and causes amidopyrine and aniline disturbances over a 2-3-week post-ischemic period. The analysis of hepatocyte ultrastructure has revealed the interdependence of structural and functional changes in endoplasmic reticulum during recovery period. The damage of monooxygenase inducibility correlated with stable decline in the number of fixed ribosomes in post-ischemic period. 相似文献