全文获取类型
收费全文 | 8287篇 |
免费 | 642篇 |
国内免费 | 532篇 |
专业分类
9461篇 |
出版年
2024年 | 17篇 |
2023年 | 143篇 |
2022年 | 201篇 |
2021年 | 241篇 |
2020年 | 231篇 |
2019年 | 310篇 |
2018年 | 278篇 |
2017年 | 219篇 |
2016年 | 242篇 |
2015年 | 337篇 |
2014年 | 430篇 |
2013年 | 521篇 |
2012年 | 332篇 |
2011年 | 425篇 |
2010年 | 398篇 |
2009年 | 424篇 |
2008年 | 498篇 |
2007年 | 480篇 |
2006年 | 408篇 |
2005年 | 342篇 |
2004年 | 343篇 |
2003年 | 316篇 |
2002年 | 329篇 |
2001年 | 251篇 |
2000年 | 218篇 |
1999年 | 193篇 |
1998年 | 174篇 |
1997年 | 163篇 |
1996年 | 155篇 |
1995年 | 132篇 |
1994年 | 107篇 |
1993年 | 103篇 |
1992年 | 83篇 |
1991年 | 68篇 |
1990年 | 62篇 |
1989年 | 59篇 |
1988年 | 49篇 |
1987年 | 22篇 |
1986年 | 32篇 |
1985年 | 33篇 |
1984年 | 35篇 |
1983年 | 21篇 |
1982年 | 12篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有9461条查询结果,搜索用时 0 毫秒
991.
Sanda Clejan Robert S. Dotson Charles F. Ide Barbara S. Beckman 《Cell biochemistry and biophysics》1997,27(3):203-225
Initial studies with the erythropoietin-sensitive human hematopoietic cell line, TF1, demonstrated both multifarious effects
of pulsed electromagnetic field (EMF) exposure on lipid signal transduction and antiproliferative effects of EMF. Stimulation
of TF1 cells with erythropoietin resulted in increased phosphatidylinositol 3-kinase activity within 2 min. Addition of wortmannin,
an inhibitor of phosphatidylinositol 3-kinase, produced a decrease in cell proliferation as measured by accumulation of cells
in the G0/G1 phase of the cell cycle and suppression of erythropoietin-induced DNA synthesis. Similar effects on cell proliferation were
seen under EMF treatment. Phosphatidylinositol 3-kinase activity in erythropoietin-stimulated TF1 cells, measured in whole-cell
extracts, increased 34% within 2 min and remained above basal levels for at least 20 min. EMF decreased erythropoietin-stimulated
phosphatidylinositol 3-kinase activity to lower than basal levels. Additionally, translocation of the 85-kDa regulatory subunit
(p85) of phosphatidylinositol 3-kinase to the membrane was prevented by EMF. Phosphatidylinositol-specific phospholipase C
was activated, as reflected by increases in diacylglycerol and inositol trisphosphate at 15–60 s after EMF treatment. These
results provide the first evidence of subtle coordinated changes by EMF associated with loss of phosphatidylinositol 3-kinase
activity, inhibition of the translocation of p85 to the membrane, and activation of phosphatidylinositol-phospholipase C. 相似文献
992.
993.
Vitté-Mony I Korneluk RG Diaz-Mitoma F 《Apoptosis : an international journal on programmed cell death》1997,2(6):501-509
A new family of human genes xiap, hiap-1 and hiap-2, which are homologous to the baculovirus iap (inhibitor of apoptosis)
genes cp-iap and op-iap, has been recently cloned and shown to suppress apoptosis after serum withdrawal or exposure to a
free radical inducer. In order to examine the role of one of these human genes, namely xiap, in lymphoid cells, we studied
XIAP expression, after PHA stimulation in three different human T cell lines. We report here that stimulation with PHA resulted
in the human T cell lines undergoing apoptosis, as assessed by DNA fragmentation and by propidiumiodide (PI) staining and
flow cytometry. When XIAP protein expression was evaluated by Western blot, we observed that the induction of apoptosis by
PHA was associated with a parallel decrease of XIAP expression. We also provide evidence that stably transfected Jurkat cells
containing the xiap open reading frame became resistant to PHA-induced apoptosis. These data suggest a role for XIAP protein
in the regulation of apoptosis in lymphoid cells.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
994.
巨噬细胞免疫调变信号:Raf-1,MAPK p44,MAPK p42和p38 MAPK的研究 总被引:2,自引:0,他引:2
为了了解巨噬细胞免疫调变机理,我们应用LPS和PMA处理小鼠抑制性巨噬细胞,观察到Ras下游信号分子Raf-1,分裂原激活蛋白激酶MAPK p44,MAPK p42和p38 MAPK均被活化,发现forskolin能增强p38 MAPK的活性,进一步提示PKC和PKA途径增强了p38 MAPK的磷酸化效应,为我们了解LPS如何激活p38 MAPK信号通路提供了一个新的机会。 相似文献
995.
The native Goα was purified from bovine brain cortex and palmitoylated in vitro. The in vitro palmitoylation site was the same as that in vivo. The internal palmitoylation of purified native Goα was found to be largely maintained. The apparant palmitoylation ratio was significantly increased after the Goa was treated with DTT. The GTPg S binding characteristic of Goα was not influenced by palmitoylation, however, the affinity for LUVs was increased dramatically. The in vitro palmitoylation model of Goα provides a better basis for studying the functional role of G protein palmitoylation in signal transduction. 相似文献
996.
997.
C. A. Salinas D. A. R. Sinclair K. O''Hare H. W. Brock 《Molecular & general genetics : MGG》1998,257(6):672-680
Processing of the 3′ end of mRNA precursors depends on several proteins. The multisubunit cleavage and polyadenylation specificity
factor (CPSF) is required for cleavage of the mRNA precursor as well as polyadenylation. CPSF interacts with the cleavage
stimulatory factor complex (CstF), and this interaction increases the specificity of binding. Following cleavage downstream
of the AAUAAA site, CPSF and poly(A) polymerase (PAP) are required for efficient polyadenylation. Recently, it has been shown
that 160-kDa subunit of CPSF interacts directly with the 77-kDa subunit of CstF, which is homologous to the product encoded
by the Drosophila gene su(f), and with PAP. Here we report the cloning and characterization of a Drosophila homologue of CPSF-160. The 1329-amino acid dCPSF protein exhibits about 45% and 20% sequence identity, respectively, to its
mammalian and yeast counterparts over its entire length. We show that the CPSF homologue is expressed throughout development
and that CPSF is essential for viability. Mutations in the cpsf gene did not alter the phenotype of homozygous su(f) mutations, suggesting that, for most genes, processing of 3′ termini is not sensitive to small changes in cpsf and su(f) dosage.
Received: 6 June 1997 / Accepted: 5 November 1997 相似文献
998.
999.
F.-Nora Vögtle Björn Brändl Austin Larson Manuela Pendziwiat Marisa W. Friederich Susan M. White Alice Basinger Cansu Kücükköse Hiltrud Muhle Johanna A. Jähn Oliver Keminer Katherine L. Helbig Carolyn F. Delto Lisa Myketin Dirk Mossmann Nils Burger Noriko Miyake Audrey Burnett Ingo Helbig 《American journal of human genetics》2018,102(4):557-573
1000.