全文获取类型
收费全文 | 69659篇 |
免费 | 6201篇 |
国内免费 | 188篇 |
出版年
2022年 | 569篇 |
2021年 | 1236篇 |
2020年 | 749篇 |
2019年 | 961篇 |
2018年 | 1402篇 |
2017年 | 1108篇 |
2016年 | 1942篇 |
2015年 | 3136篇 |
2014年 | 3472篇 |
2013年 | 4094篇 |
2012年 | 5267篇 |
2011年 | 5014篇 |
2010年 | 3194篇 |
2009年 | 2804篇 |
2008年 | 4025篇 |
2007年 | 3738篇 |
2006年 | 3443篇 |
2005年 | 3107篇 |
2004年 | 3048篇 |
2003年 | 2685篇 |
2002年 | 2343篇 |
2001年 | 1971篇 |
2000年 | 1824篇 |
1999年 | 1465篇 |
1998年 | 666篇 |
1997年 | 611篇 |
1996年 | 522篇 |
1995年 | 502篇 |
1994年 | 436篇 |
1993年 | 411篇 |
1992年 | 828篇 |
1991年 | 710篇 |
1990年 | 655篇 |
1989年 | 672篇 |
1988年 | 576篇 |
1987年 | 549篇 |
1986年 | 469篇 |
1985年 | 471篇 |
1984年 | 391篇 |
1983年 | 322篇 |
1982年 | 288篇 |
1981年 | 265篇 |
1980年 | 253篇 |
1979年 | 324篇 |
1978年 | 307篇 |
1977年 | 246篇 |
1976年 | 261篇 |
1975年 | 245篇 |
1974年 | 291篇 |
1973年 | 240篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Hyperthermic treatment at 43 degrees C suppressed the growth of Ehrlich ascites tumor (EAT) cells in vitro. Incubation of EAT cells at 43 degrees C for as little as 1.5 h totally abolished the transplantability of the tumor. At the same time, the rate of cellular glucose uptake, the density of glucose transporter on the cells as well as the extent of thymidine, uridine and leucine incorporation were significantly reduced. 相似文献
82.
J J Tarín S Pérez-Albalá A Aguilar J Mi?arro C Hermenegildo A Cano 《Biology of reproduction》1999,61(5):1347-1355
Aims of this study were to analyze the long-term effects of postovulatory aging of mouse oocytes on 1) reproductive traits of parental (F(0)) and first (F(1))-generation females (pregnancy rate, gestation length, litter size, perinatal death, and sex ratio of offspring) and 2) developmental and behavioral variables of F(1) and second-generation (F(2)) offspring (birth weight and weight gain during preweaning development, postnatal day of attainment of immediate righting, spontaneous motor activity, and passive and active conditioned learning ability). Hybrid (C57BL/6JIco x CBA/JIco) females were artificially inseminated at 13 h (control group) or 22 h (oocyte-aged group) after GnRH injection. Experimental (oocyte-aged group) F(0) females exhibited lower pregnancy rate, shortened gestation length, decreased litter size, higher perinatal death of their pups, and increased percentage of male offspring compared to control F(0) females. Postovulatory aging of oocytes was also associated with increased number of growth-retarded pups, delayed development of the righting reflex, and higher spontaneous motor activity and emotionality of F(1) offspring. Postovulatory aging of F(0) oocytes did not affect birth weight, weight gain during preweaning development, passive and active conditioned learning ability of F(1) offspring, or reproductive traits of F(1) females or developmental and behavior variables of F(2) offspring. 相似文献
83.
84.
85.
Scaffolding proteins are involved in the incorporation, anchoring, maintenance, and removal of AMPA receptors (AMPARs) at synapses, either through a direct interaction with AMPARs or via indirect association through auxiliary subunits of transmembrane AMPAR regulatory proteins (TARPs). Synaptic scaffolding molecule (S-SCAM) is a newly characterized member of the scaffolding proteins critical for the regulation and maintenance of AMPAR levels at synapses, and directly binds to TARPs through a PDZ interaction. However, the functional significance of S-SCAM–TARP interaction in the regulation of AMPARs has not been tested. Here we show that overexpression of the C-terminal peptide of TARP-γ2 fused to EGFP abolished the S-SCAM-mediated enhancement of surface GluA2 expression. Conversely, the deletion of the PDZ-5 domain of S-SCAM that binds TARPs greatly attenuated the S-SCAM-induced increase of surface GluA2 expression. In contrast, the deletion of the guanylate kinase domain of S-SCAM did not show a significant effect on the regulation of AMPARs. Together, these results suggest that S-SCAM is regulating AMPARs through TARPs. 相似文献
86.
Effect of membrane additives on vesicle fusion 总被引:1,自引:0,他引:1
A large variety of alkyl derivatives were found to either slow or block the low-temperature induced fusion of dipalmitoylphosphatidylcholine small unilamellar vesicles (DPPC SUV) when incorporated into the SUV bilayer at five mol%. Only corn oil was fusogenic. 相似文献
87.
88.
Virion conformational forms and the complex inactivation kinetics of echovirus by chlorine in water 总被引:1,自引:0,他引:1
Aberrant inactivation kinetics were observed when monodispersed echovirus type 1 (Farouk) was inactivated with chlorine. An initial 1- to 2-log10-unit decrease in titer was followed by lag period, during which the titer stayed the same or increased, and this was followed by a final decline in titer. First-order kinetics were obtained with poliovirus type 1 under the same conditions. Isoelectric focusing studies of echovirus before chlorine treatment showed that the virus distributed into two pH-dependent and interconvertible isoelectric forms. After chlorine treatment all remaining virus infectivity was associated with a third pH-independent isoelectric form. The complex inactivation kinetics appeared to be due to shifts between these conformational forms during inactivation in certain ionic environments. Under certain conditions the conformational shifts resulted in substantial resistance of monodispersed echovirus to chlorine. 相似文献
89.
Young J. Oh Jonathan W. Francis George J. Markelonis Tae H. Oh 《Journal of neurochemistry》1992,58(6):2131-2138
Peripheral-type benzodiazepine binding sites (PTBBS) are markedly increased in the injured CNS. Astrocytes appear to be the primary cell type which express increased PTBBS. Because certain cytokines within the injured CNS are potent mitogens for astrocytes, we examined the effects of two such cytokines, interleukin (IL)-1 beta and tumor necrosis factor (TNF), on PTBBS in cultured astrocytes using [3H]Ro 5-4864 as the specific ligand. Purified cultures of either polygonal or process-bearing astrocytes were prepared from neonatal rat cerebral hemispheres. At a concentration of 1.8 nM, specific binding of the radioactive ligand to polygonal astrocytes reached equilibrium within 60 min and was half-maximal by 5-10 min. By contrast, specific binding to process-bearing astrocytes barely exceeded background levels. IL-1 and TNF increased PTBBS within polygonal astrocytes in both dose- and time-dependent manners. At 10-50 ng/ml, IL-1 beta and TNF-alpha elevated [3H]Ro 5-4864 binding in polygonal astrocyte cultures 65 and 87%, respectively, above the level in control cultures. However, no changes in PTBBS were seen within polygonal astrocytes after IL-2 treatment. Scatchard analysis of saturation binding experiments suggested that the increase in PTBBS promoted by TNF was due to an increased number of binding sites present in polygonal astrocytes and not due to an increase in receptor affinity. Binding data suggested that PTBBS within cultures of process-bearing astrocytes were virtually absent irrespective of the treatment. These in vitro data suggest that certain cytokines found in the injured brain may be involved in up-regulating PTBBS within a particular subtype of astrocyte. 相似文献
90.