全文获取类型
收费全文 | 732194篇 |
免费 | 73745篇 |
国内免费 | 994篇 |
出版年
2018年 | 19019篇 |
2017年 | 17612篇 |
2016年 | 16685篇 |
2015年 | 13289篇 |
2014年 | 14526篇 |
2013年 | 20215篇 |
2012年 | 27441篇 |
2011年 | 36314篇 |
2010年 | 27618篇 |
2009年 | 22516篇 |
2008年 | 30148篇 |
2007年 | 32672篇 |
2006年 | 18750篇 |
2005年 | 19099篇 |
2004年 | 18491篇 |
2003年 | 17894篇 |
2002年 | 16818篇 |
2001年 | 24671篇 |
2000年 | 25125篇 |
1999年 | 20100篇 |
1998年 | 7351篇 |
1997年 | 7610篇 |
1996年 | 7353篇 |
1995年 | 7095篇 |
1994年 | 7076篇 |
1993年 | 6908篇 |
1992年 | 17258篇 |
1991年 | 17078篇 |
1990年 | 16620篇 |
1989年 | 16148篇 |
1988年 | 15092篇 |
1987年 | 14448篇 |
1986年 | 13474篇 |
1985年 | 13683篇 |
1984年 | 11534篇 |
1983年 | 10183篇 |
1982年 | 7862篇 |
1981年 | 7359篇 |
1980年 | 6889篇 |
1979年 | 11403篇 |
1978年 | 8890篇 |
1977年 | 8175篇 |
1976年 | 7781篇 |
1975年 | 8633篇 |
1974年 | 8936篇 |
1973年 | 8778篇 |
1972年 | 8801篇 |
1971年 | 7739篇 |
1970年 | 6299篇 |
1969年 | 5941篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
851.
852.
Biochemical, biological, and immunological properties of chemically deglycosylated human choriogonadotropin 总被引:5,自引:0,他引:5
A chemical method of deglycosylation of human choriogonadotropin (hCG) was used to assess the role of carbohydrate moiety in the maintenance of quaternary structure and functional parameters such as receptor binding, immunological activity, and in vitro biological response. Treatment of purified hCG with anhydrous HF at 0 degrees C for 60 min was effective in removing more than 75% of the carbohydrate moiety. This extent of deglycosylation altered its chromatographic characteristics as revealed by retarded behavior on Sephadex G-100 and failure to be retained on concanavalin A-Sepharose. The electrophoretic heterogeneity present in native hCG was markedly reduced by deglycosylation. The deglycosylated hCG was stable in the lyophilized form and retained its quaternary structure as revealed by the fluorescence probe 8-anilino 1-naphthalene sulfonic acid, receptor binding, and immunological activities. Unlike receptor binding and immunological activities, which were fully retained, the ability of the hormone to stimulate cyclic AMP accumulation in vitro in rat interstitial cells was completely abolished. 相似文献
853.
854.
Emin Oguzhan Oguz Hayati Yuksel Yasar Enli A. Cevik Tufan Gunfer Turgut 《Biological trace element research》2010,133(3):335-341
Copper is an essential trace element that is extremely toxic to organisms and organs at high doses. We have investigated the
histological and biochemical effects of a toxic dose of copper sulfate on the liver of term Ross broiler chicks. Fertilized
eggs were divided into three groups: experimental, injected with 50 mcg/0.1 ml copper sulfate in the air chambers on day 1;
sham, injected with 0.1 ml saline; and control, no injection. Term chicks were killed and their livers investigated histologically,
with hematoxylin–eosin-stained sections examined under light microscopy, and biochemically, for malondialdehyde and glutathione
levels. Histological examinations showed copper-treated samples with granular degeneration and necrosis of hepatocytes and
impairment to the cell lining of the remark cords. The samples had a congestive appearance, with blood in the vena centralis
and sinusoids, slight connective tissue increase, and lymphocyte infiltration. Control and sham group sections had normal
appearances. As oxidative damage parameters, in the copper-treated group, malondialdehyde levels were increased and glutathione
levels decreased. In the sham and control groups, there were no significant differences. At this toxic dose, copper sulfate
shows oxidative damage according to the histology of term chick liver that are confirmed biochemically by the changes in malondialdehyde
and glutathione levels. 相似文献
855.
DONALD R. STRONG Jr 《Ecological Entomology》1982,7(2):217-220
Abstract. 1. Adults of rolled-leaf hispine beetles (Chrysomelidae, Coleoptera) spend their lives in the scrolls formed by immature leaves of Heliconia (Heli-coniaceae, Monocotyledonae) in Tropical America. As many as eight hispine species can intermingle in the host scrolls at a single site. Scrolls of single host species are invariably occupied by adults of more than one hispine species, and as many as five species can simultaneously occupy one scroll.
2. I made virgin scrolls, which had never contained any insects, by growing leaves under the cover of plastic bags.
3. Thirty-seven combinations of single hispine and Heliconia species were experimentally created in the virgin scrolls, at two sites and in two seasons, in Costa Rica. Combinations included all abundant host species at the sites.
4. All beetles left all leaves of the twenty-eight unnatural beetle—host combinations, within 24 h. On the other hand, none of the nine natural combinations was completely abandoned within the experimental period.
5. Thus, host specificity is not broader in the absence of similar hispine species that might be competitors, and interspecies competition does not affect this obvious aspect of resource utilization for these phytophagous insects. 相似文献
2. I made virgin scrolls, which had never contained any insects, by growing leaves under the cover of plastic bags.
3. Thirty-seven combinations of single hispine and Heliconia species were experimentally created in the virgin scrolls, at two sites and in two seasons, in Costa Rica. Combinations included all abundant host species at the sites.
4. All beetles left all leaves of the twenty-eight unnatural beetle—host combinations, within 24 h. On the other hand, none of the nine natural combinations was completely abandoned within the experimental period.
5. Thus, host specificity is not broader in the absence of similar hispine species that might be competitors, and interspecies competition does not affect this obvious aspect of resource utilization for these phytophagous insects. 相似文献
856.
857.
858.
859.
860.