全文获取类型
收费全文 | 52155篇 |
免费 | 6504篇 |
国内免费 | 21964篇 |
出版年
2024年 | 261篇 |
2023年 | 1388篇 |
2022年 | 2363篇 |
2021年 | 2983篇 |
2020年 | 2775篇 |
2019年 | 3200篇 |
2018年 | 2349篇 |
2017年 | 2092篇 |
2016年 | 2392篇 |
2015年 | 3292篇 |
2014年 | 4358篇 |
2013年 | 4059篇 |
2012年 | 5482篇 |
2011年 | 5229篇 |
2010年 | 4036篇 |
2009年 | 4047篇 |
2008年 | 4355篇 |
2007年 | 4032篇 |
2006年 | 3757篇 |
2005年 | 3192篇 |
2004年 | 2459篇 |
2003年 | 2121篇 |
2002年 | 1888篇 |
2001年 | 1725篇 |
2000年 | 1551篇 |
1999年 | 1063篇 |
1998年 | 586篇 |
1997年 | 434篇 |
1996年 | 371篇 |
1995年 | 308篇 |
1994年 | 253篇 |
1993年 | 225篇 |
1992年 | 233篇 |
1991年 | 208篇 |
1990年 | 188篇 |
1989年 | 141篇 |
1988年 | 165篇 |
1987年 | 124篇 |
1986年 | 128篇 |
1985年 | 133篇 |
1984年 | 91篇 |
1983年 | 64篇 |
1982年 | 104篇 |
1981年 | 52篇 |
1980年 | 23篇 |
1979年 | 36篇 |
1977年 | 20篇 |
1976年 | 18篇 |
1957年 | 22篇 |
1950年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
趾钩是鳞翅目幼虫分类上常用的特征之一。从本世纪40年代起,神冈等对家蚕幼虫腹足趾钩进行了广泛的研究,中岛(1956)对柞蚕幼虫腹足趾钩有过简短的报告。柞蚕幼虫腹足趾钩不但与地理品种分化有关,而且,由于柞蚕幼虫在野外山林中生活,柞蚕取食等活动,均靠趾钩把握柞枝,趾钩与柞蚕把握力有着密切关系。现将柞蚕幼虫腹足趾钩的形态特征扼要报告如下。 相似文献
113.
作者曾于1986年首次报道了在我国四川省汶川县卧龙地区发现的指虻属(Isshikia)一新种——汶川指虻。本文再次记述了在我国海南省发现的另一指虻属新种——海南指虻。另外同时记述在我国西藏地区发现的瘤虻属(Hybomitra)一新种——黑须瘤虻。模式标本均保存于中国科学院动物研究所。 相似文献
114.
The gIII glycoproteins of bovine herpesvirus 1 (BHV-1) and of pseudorabies virus (PRV) are structurally homologous. Both proteins also play preeminent roles in mediating virus attachment to permissive cells. To directly compare the functional relation between these glycoproteins, we constructed a recombinant BHV-1 in which the BHV-1 gIII coding sequence was replaced by the PRV gene homolog. The resultant recombinant virus efficiently expressed PRV gIII and then incorporated it into its envelope. The levels of PRV gIII expression and incorporation were equivalent to those achieved by the wild-type virus for BHV-1 gIII. The recombinant virus was fully susceptible to neutralization by anti-PRV gIII neutralizing antibody. In addition, the virus attachment and penetration functions, as well as the virus replication efficiency, which were lost by deleting the BHV-1 gIII gene, were restored by expressing the PRV gIII homolog in its place. These results demonstrated that PRV gIII and BHV-1 gIII share complementary functions. 相似文献
115.
Renmei Ren Kanhui Yan Yanjie Su Hanjun Qi Bin Liang Wunyong Bao Frans B. M. de Waal 《Primates; journal of primatology》1991,32(3):321-327
Observations were made following 130 spontaneous aggressive incidents in two small breeding groups of captive golden monkeys
(Rhinopithecus roxellanae roxellanae). Participants were observed both during the first 10 min following these incidents and during matched control observations.
An increased contact rate was observed between opponents following the aggressive incident. Post-conflict contacts were characterized
by a number of behavior patterns: open mouth, rapid grooming, embrace, and crouching. Adult males played an important role
as mediator in agonistic disputes among females: males intervened in 93.6% of female fights. It is speculated that this intervention
behavior is related to the species' organization into one-male units. 相似文献
116.
Oxidation of dimethyl sulfide byPseudomonas acidovorans DMR-11 isolated from peat biofilter 总被引:1,自引:0,他引:1
Summary
Pseudomonas acidovorans DMR-11, capable of oxidizing dimethyl sulfide (DMS), was isolated from peat biofilter. DMS as a sole carbon or energy source was not degraded, but it was co-degraded in the medium containing organic carbon sources. The removal rate of DMS in heat-treated glucose medium was 1.12×10–17 mole/h cell at 30 °C. Dimethyl sulfoxide (DMSO) was the only product of DMS oxidation and was formed stoichiometrically. DMS was reversibly evolved in excess of DMSO. The cell free extract of strain DMR-11 oxidized DMS in presence of NADPH. 相似文献
117.
Summary The NAD(P)H fluorescence ofPseudomonas aeruginosa dropped sharply upon addition of nitrate to an anaerobic culture, indicating that denitrification is not limited by mass
transfer of nitrate through cell membrane to reach nitrate reductase. The effect of added nitrate concentration on fluorescence
drop followed a typical saturation kinetics. The maximum specific denitrification rate under the studied condition was found
to be 0.26±0.05 g NO
3
−
-N/g cells-hr. 相似文献
118.
119.
作者测定并分析了43只雄貉睾丸宽度、血清睾酮水平的季节性变化。结果表明:睾丸宽度和血清睾酮水平呈明显的年周期季节性变化(p<0.01)。秋分(9月)时,睾丸宽度开始增大(p<0.05 );血清睾酮水平在10月开始升高(p<0.05)。各月雄貉的平均睾酮水平与平均睾丸宽度是极显著的正相关(r=0.83,p<0.01 n=11)。雄貉繁殖季节初期,血清睾酮水平与其首、末次的交配日期呈显著负相关(r=-0.525和r=-0.476,p<0.05,n=19)。 相似文献
120.