全文获取类型
收费全文 | 507508篇 |
免费 | 54653篇 |
国内免费 | 196篇 |
专业分类
562357篇 |
出版年
2018年 | 4884篇 |
2016年 | 6550篇 |
2015年 | 8404篇 |
2014年 | 9940篇 |
2013年 | 13844篇 |
2012年 | 15598篇 |
2011年 | 16066篇 |
2010年 | 11163篇 |
2009年 | 10231篇 |
2008年 | 14649篇 |
2007年 | 15195篇 |
2006年 | 14246篇 |
2005年 | 13604篇 |
2004年 | 13574篇 |
2003年 | 12769篇 |
2002年 | 12487篇 |
2001年 | 20915篇 |
2000年 | 20749篇 |
1999年 | 16549篇 |
1998年 | 5970篇 |
1997年 | 6181篇 |
1996年 | 5729篇 |
1995年 | 5374篇 |
1994年 | 5208篇 |
1993年 | 5280篇 |
1992年 | 13646篇 |
1991年 | 13539篇 |
1990年 | 13337篇 |
1989年 | 12773篇 |
1988年 | 12228篇 |
1987年 | 11779篇 |
1986年 | 10956篇 |
1985年 | 10783篇 |
1984年 | 9058篇 |
1983年 | 7840篇 |
1982年 | 6000篇 |
1981年 | 5404篇 |
1980年 | 5176篇 |
1979年 | 8672篇 |
1978年 | 6851篇 |
1977年 | 6329篇 |
1976年 | 6066篇 |
1975年 | 6616篇 |
1974年 | 7458篇 |
1973年 | 7344篇 |
1972年 | 6807篇 |
1971年 | 6156篇 |
1970年 | 5473篇 |
1969年 | 5454篇 |
1968年 | 5172篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
A. V. Nikolayev Yu. V. Kirichek O. I. Ostrovskaya I. I. Maletina K. I. Petko L. M. Yagupol’skii 《Neurophysiology》1999,31(3):191-193
With the use of a patch-clamp technique in the whole-cell configuration, we studied the effects of pinacidil and its fluorine
derivatives on A-type potassium current (I
A) through the membrane of pyramidal neurons of the rat hippocampus. Hydrogen peroxide (10 mM) exerted no influence on the
rate of inactivation ofI
A; therefore, this current is probably mediated by Shal Kv4.2 potassium channels. Pinacidil demonstrated the properties of
a weakI
A blocker: in the 500 μM concentration it blocked about 45% of the current, while 50 μM of pinacidil fluorine derivatives were
capable of blocking up to 30% ofI
A. The effects of pinacidil and its derivatives showed no dependence on the stimulating potential. A similar pattern of the
effects of pinacidil fluorine derivatives, which are an order of magnitude stronger than those of pinacidil itself, allows
us to suppose that the imine nitrogen of the tested compounds is significantly more involved in the molecular interaction
with the site of an A-type potassium channel than the pyridine nitrogen. 相似文献
92.
93.
Donald E. Rivett Dean Hewish Alan Kirkpatrick Jerome Werkmeister 《Journal of Protein Chemistry》1999,18(3):291-295
Nine fatty acid–peptide hybrid molecules were constructed using the general formula CH3(CH2)
n
CO-Phe Asp Cys-amide and tested for their ability to inhibit cell lysis induced by the membrane-active peptide melittin. All of these molecules, where n = 4–14, inhibited the action of melittin to some extent, but the longer carbon chains were most effective. Several potential inhibitors were also constructed with conservative substitutions in the peptide portion of the molecule. All were effective to varying degrees. We concluded that in the hexapeptide inhibitor published by Blondelle et al. (1993), the role of the first three residues is only to provide hydrophobic interaction with the melittin and has no particular amino acid sequence specificity. Some of these inhibitors were found to inhibit the lytic activity of a melittin analogue which had only superficial sequence similarity to melittin and also a truncated form of melittin, indicating the generality of the action of the inhibitors.Deceased 5/4/98 相似文献
94.
95.
96.
97.
HIF-1 expression in healing wounds: HIF-1alpha induction in primary inflammatory cells by TNF-alpha 总被引:12,自引:0,他引:12
98.
99.
100.
The cell surface of the parasitic protozoan Leishmania mexicana is coated by glycosylphosphatidylinositol (GPI)-anchored glycoproteins, a GPI-anchored lipophosphoglycan and a class of free GPI glycolipids. To investigate whether the anchor or free GPIs are required for parasite growth we cloned the L.mexicana gene for dolichol-phosphate-mannose synthase (DPMS) and attempted to create DPMS knockout mutants by targeted gene deletion. DPMS catalyzes the formation of dolichol-phosphate mannose, the sugar donor for all mannose additions in the biosynthesis of both the anchor and free GPIs, except for a alpha1-3-linked mannose residue that is added exclusively to the free GPIs and lipophosphoglycan anchor precursors. The requirement for dolichol-phosphate-mannose in other glycosylation pathways in L.mexicana is minimal. Deletion of both alleles of the DPMS gene (lmdpms) consistently resulted in amplification of the lmdpms chromosomal locus unless the promastigotes were first transfected with an episomal copy of lmdpms, indicating that lmdpms, and possibly GPI biosynthesis, is essential for parasite growth. As evidence presented in this and previous studies indicates that neither GPI-anchored glycoproteins nor lipophosphoglycan are required for growth of cultured parasites, it is possible that the abundant and functionally uncharacterized free GPIs are essential membrane components. 相似文献