全文获取类型
收费全文 | 188204篇 |
免费 | 3148篇 |
国内免费 | 858篇 |
出版年
2021年 | 499篇 |
2019年 | 425篇 |
2018年 | 13081篇 |
2017年 | 12029篇 |
2016年 | 10662篇 |
2015年 | 7193篇 |
2014年 | 6587篇 |
2013年 | 6646篇 |
2012年 | 9751篇 |
2011年 | 15682篇 |
2010年 | 14577篇 |
2009年 | 10705篇 |
2008年 | 11008篇 |
2007年 | 12554篇 |
2006年 | 1509篇 |
2005年 | 7615篇 |
2004年 | 6705篇 |
2003年 | 4959篇 |
2002年 | 2225篇 |
2001年 | 1541篇 |
2000年 | 691篇 |
1999年 | 1632篇 |
1998年 | 424篇 |
1992年 | 1993篇 |
1991年 | 2090篇 |
1990年 | 2121篇 |
1989年 | 2044篇 |
1988年 | 2002篇 |
1987年 | 1845篇 |
1986年 | 1650篇 |
1985年 | 1677篇 |
1984年 | 1123篇 |
1983年 | 872篇 |
1982年 | 480篇 |
1981年 | 442篇 |
1979年 | 1091篇 |
1978年 | 770篇 |
1977年 | 614篇 |
1976年 | 637篇 |
1975年 | 899篇 |
1974年 | 998篇 |
1973年 | 1012篇 |
1972年 | 1204篇 |
1971年 | 1209篇 |
1970年 | 828篇 |
1969年 | 839篇 |
1968年 | 738篇 |
1967年 | 755篇 |
1966年 | 593篇 |
1965年 | 450篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Indomethacin and substance BW-755C in experiments on isolated myometrium striae of pregnant white rats exert an inhibiting effect on the contractile uterus function due to inhibition of cyclooxygenase or lipoxygenase ways of the arachidonic acid transformation. Prostaglandin F2 alpha is sensitive to functioning of the cyclooxygenase and lipoxygenase ways of the arachidonic acid transformation, while oxytocin--only lipoxygenase one. Conclusions rest on results from multiparametric analysis of the contractile uterus function suggested by authors and confirmed by the pattern recognition method--the Karunen-Loev orthogonal decomposition. 相似文献
72.
73.
74.
M Kh Ga?nutdinov S I Mirmakhmudova N M Mullagalieva Ia Kh Turakulov 《Biulleten' eksperimental'no? biologii i meditsiny》1984,97(3):293-295
Addition of a thermostable cytoplasmic fraction leads to the uncoupling of oxidative phosphorylation of the mitochondria. In hyperthyrosis such an effect manifests itself more powerfully than in the control. Addition of the thermostable cytoplasmic fraction induces electrogenic phosphate transport via the mitochondrial membrane. In hyperthyrosis, the activity of the thermostable inducer of phosphate transport in the cytoplasm increases. The functioning of the phosphate cycle may be the cause of the uncoupling of oxidative phosphorylation of the mitochondria during the disease in question. 相似文献
75.
Transcriptional regulatory network triggered by oxidative signals configures the early response mechanisms of japonica rice to chilling stress 总被引:3,自引:0,他引:3
76.
Thyroid hormones are potent, instantaneous, and reversible inhibitors of ethanol oxidation catalyzed by isozymes of class I and II human alcohol dehydrogenase (ADH). None of the thyroid hormones inhibits class III ADH. At pH 7.40 the apparent Ki values vary between 55 and 110 microM for triiodothyronine, 35 and greater than 200 microM for thyroxine, and 10 and 23 microM for triiodothyroacetic acid. The inhibition is of a mixed type toward both NAD+ and ethanol. The binding of the thyroid hormone triiodothyronine to beta 1 gamma 1 ADH is mutually exclusive with 1,10-phenanthroline, 4-methylpyrazole, and testosterone, identifying a binding site(s) for the thyroid hormones, which overlap(s) both the 1,10-phenanthroline site near the active site zinc atom and the testosterone binding site, the latter being a regulatory site on the gamma-subunit-containing isozymes and distinct from their catalytic site. The inhibition by thyroid hormones may have implications for regulation of ADH catalysis of ethanol and alcohols in the intermediary metabolism of dopamine, norepinephrine, and serotonin and in steroid metabolism. In concert with other hormonal regulators, e.g., testosterone, the rate of ADH catalysis is capable of being fine tuned in accord with both substrate and modulator concentrations. 相似文献
77.
Recent studies have revealed an unexpected synergism between two seemingly unrelated protein families: CCN matricellular proteins
and the tumor necrosis factor (TNF) family of cytokines. CCN proteins are dynamically expressed at sites of injury repair
and inflammation, where TNF cytokines are also expressed. Although TNFα is an apoptotic inducer in some cancer cells, it activates
NFκB to promote survival and proliferation in normal cells, and its cytotoxicity requires inhibition of de novo protein synthesis
or NFκB signaling. The presence of CCN1, CCN2, or CCN3 overrides this requirement and unmasks the apoptotic potential of TNFα,
thus converting TNFα from a proliferation-promoting protein into an apoptotic inducer. These CCN proteins also enhance the
cytotoxicity of other TNF cytokines, including LTα, FasL, and TRAIL. Mechanistically, CCNs function through integrin α6β1 and the heparan sulfate proteoglycan (HSPG) syndecan-4 to induce reactive oxygen species (ROS) accumulation, which is essential
for apoptotic synergism. Mutant CCN1 proteins defective for binding α6β1-HSPGs are unable to induce ROS or apoptotic synergism with TNF cytokines. Further, knockin mice that express an α6β1-HSPG-binding defective CCN1 are blunted in TNFα- and Fas-mediated apoptosis, indicating that CCN1 is a physiologic regulator
of these processes. These findings implicate CCN proteins as contextual regulators of the inflammatory response by dictating
or enhancing the cytotoxicity of TNFα and related cytokines. 相似文献
78.
79.
Background
Introductions of non-native tiger salamanders into the range of California tiger salamanders have provided a rare opportunity to study the early stages of secondary contact and hybridization. We produced first- and second-generation hybrid salamanders in the lab and measured viability among these early-generation hybrid crosses to determine the strength of the initial barrier to gene exchange. We also created contemporary-generation hybrids in the lab and evaluated the extent to which selection has affected fitness over approximately 20 generations of admixture. Additionally, we examined the inheritance of quantitative phenotypic variation to better understand how evolution has progressed since secondary contact. 相似文献80.