全文获取类型
收费全文 | 173728篇 |
免费 | 12880篇 |
国内免费 | 51篇 |
出版年
2022年 | 1076篇 |
2021年 | 2546篇 |
2020年 | 1750篇 |
2019年 | 2022篇 |
2018年 | 3593篇 |
2017年 | 3215篇 |
2016年 | 4732篇 |
2015年 | 7158篇 |
2014年 | 7752篇 |
2013年 | 9729篇 |
2012年 | 12264篇 |
2011年 | 11445篇 |
2010年 | 7381篇 |
2009年 | 6359篇 |
2008年 | 9558篇 |
2007年 | 9375篇 |
2006年 | 8961篇 |
2005年 | 8226篇 |
2004年 | 8059篇 |
2003年 | 7539篇 |
2002年 | 7026篇 |
2001年 | 2971篇 |
2000年 | 2599篇 |
1999年 | 2449篇 |
1998年 | 1926篇 |
1997年 | 1322篇 |
1996年 | 1316篇 |
1995年 | 1211篇 |
1994年 | 1079篇 |
1993年 | 1093篇 |
1992年 | 1564篇 |
1991年 | 1389篇 |
1990年 | 1379篇 |
1989年 | 1429篇 |
1988年 | 1234篇 |
1987年 | 1216篇 |
1986年 | 1119篇 |
1985年 | 1355篇 |
1984年 | 1299篇 |
1983年 | 1161篇 |
1982年 | 1170篇 |
1981年 | 1068篇 |
1980年 | 1057篇 |
1979年 | 1055篇 |
1978年 | 948篇 |
1977年 | 885篇 |
1976年 | 831篇 |
1975年 | 886篇 |
1974年 | 974篇 |
1973年 | 940篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
181.
182.
183.
184.
W J Koopman M H Gillis J R David 《Journal of immunology (Baltimore, Md. : 1950)》1973,110(6):1609-1614
185.
186.
Six peripheral blood lymphoid fractions (total lymphocytes, non-T, T, Tar (autologous rosette-forming T cells/precursor), T mu (helper), and T gamma (suppressor) lymphocytes) isolated through rosetting procedures were examined for the presence of ferritin by a direct immunofluorescence technique. Although ferritin was present in all lymphoid fractions studied, a significantly higher proportion of ferritin-containing cells were detected in the T-cell fraction than in the non-T-cell fraction, (mean +/- SD = 7.9 +/- 1.6% and 5.0 +/- 1.2%, respectively). T mu- and T gamma-cell fractions showed a twofold increase in the number of ferritin-positive cells (14.1 +/- 1.4% and 15.4 +/- 2.6%, respectively), as compared with Tar (7.0 +/- 0.9%)-and total lymphocyte (6.9 +/- 1.3%)-cell fractions. These results indicate that ferritin is preferentially distributed in T mu and T gamma lymphocytes and may constitute the basis for explaining some of the roles exercised by these cells in the control of other biological systems. 相似文献
187.
188.
Kinga Michno David Knight Jorge M. Campussano Diana van de Hoef Gabrielle L. Boulianne 《PloS one》2009,4(9)
Much of our current understanding about neurodegenerative diseases can be attributed to the study of inherited forms of these disorders. For example, mutations in the presenilin 1 and 2 genes have been linked to early onset familial forms of Alzheimer''s disease (FAD). Using the Drosophila central nervous system as a model we have investigated the role of presenilin in one of the earliest cellular defects associated with Alzheimer''s disease, intracellular calcium deregulation. We show that expression of either wild type or FAD-mutant presenilin in Drosophila CNS neurons has no impact on resting calcium levels but does give rise to deficits in intracellular calcium stores. Furthermore, we show that a loss-of-function mutation in calmodulin, a key regulator of intracellular calcium, can suppress presenilin-induced deficits in calcium stores. Our data support a model whereby presenilin plays a role in regulating intracellular calcium stores and demonstrate that Drosophila can be used to study the link between presenilin and calcium deregulation. 相似文献
189.
Charles E. Wenner John C. Cheney L. David Tomei 《Journal of cellular biochemistry》1981,15(2):161-168
The introduction of either PGF2α (10?7 M) or TPA (10?7 M) stimulated, ouabain-sensitive 86Rb+ influx at 30 min in postconfluent 3T3-4 mouse fibroblast cultures by 117% and 124%, respectively. Both TPA and PGF2α at these concentrations stimulated the incorporation of 3H-TdR into DNA. TPA had the greatest stimulatory effect, which was similar to that obtained with 10% fetal calf serum. In accord with the idea that modulation of membrane processes such as Na+/K+ pump activity in fibroblasts may reflect important events related to the initiation of DNA synthesis, it was observed that in both 3T3-4 and C3H-1 0T½ cells there were parallel increases in 3H-TdR incorporation and ouabain-sensitive 86Rb+ influxes with 10?7 M TPA, whereas PGF2α stimulated a significant increase in 3H-TdR incorporation in 3T3-4 but not C3H-10T½ cells and only marginal increases in ouabain-sensitive 86Rb+ influx in both. Therefore, although there appears to be a close correlation between Na+/K+ pump activation and subsequent S-phase entry following TPA stimulation, a similar correlation for PGF2α cannot be confirmed. 相似文献
190.