全文获取类型
收费全文 | 1377985篇 |
免费 | 123710篇 |
国内免费 | 1559篇 |
专业分类
1503254篇 |
出版年
2021年 | 17887篇 |
2019年 | 16213篇 |
2018年 | 17549篇 |
2017年 | 16322篇 |
2016年 | 28035篇 |
2015年 | 42572篇 |
2014年 | 50769篇 |
2013年 | 77096篇 |
2012年 | 37650篇 |
2011年 | 25989篇 |
2010年 | 43524篇 |
2009年 | 44896篇 |
2008年 | 24639篇 |
2007年 | 22834篇 |
2006年 | 28347篇 |
2005年 | 29195篇 |
2004年 | 28507篇 |
2003年 | 26037篇 |
2002年 | 24274篇 |
2001年 | 35205篇 |
2000年 | 32811篇 |
1999年 | 32482篇 |
1998年 | 25619篇 |
1997年 | 25364篇 |
1996年 | 24846篇 |
1995年 | 23033篇 |
1994年 | 22858篇 |
1993年 | 21942篇 |
1992年 | 27905篇 |
1991年 | 26025篇 |
1990年 | 24639篇 |
1989年 | 25436篇 |
1988年 | 23408篇 |
1987年 | 22149篇 |
1986年 | 21294篇 |
1985年 | 23202篇 |
1984年 | 22845篇 |
1983年 | 20075篇 |
1982年 | 20803篇 |
1981年 | 20011篇 |
1980年 | 18603篇 |
1979年 | 19074篇 |
1978年 | 18073篇 |
1977年 | 17324篇 |
1976年 | 16496篇 |
1975年 | 16115篇 |
1974年 | 16812篇 |
1973年 | 17138篇 |
1972年 | 14701篇 |
1971年 | 13433篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
Tansley Review No. 112 总被引:4,自引:0,他引:4
105.
106.
Binding of the cationic tetra(tributylammoniomethyl)-substituted hydroxoaluminum phthalocyanine (AlPcN4) to bilayer lipid membranes was studied by fluorescence correlation spectroscopy (FCS) and intramembrane field compensation (IFC) methods. With neutral phosphatidylcholine membranes, AlPcN4 appeared to bind more effectively than the negatively charged tetrasulfonated aluminum phthalocyanine (AlPcS4), which was attributed to the enhancement of the coordination interaction of aluminum with the phosphate moiety of phosphatidylcholine by the electric field created by positively charged groups of AlPcN4. The inhibitory effect of fluoride ions on the membrane binding of both AlPcN4 and AlPcS4 supported the essential role of aluminum-phosphate coordination in the interaction of these phthalocyanines with phospholipids. The presence of negative or positive charges on the surface of lipid membranes modulated the binding of AlPcN4 and AlPcS4 in accord with the character (attraction or repulsion) of the electrostatic interaction, thus showing the significant contribution of the latter to the phthalocyanine adsorption on lipid bilayers. The data on the photodynamic activity of AlPcN4 and AlPcS4 as measured by sensitized photoinactivation of gramicidin channels in bilayer lipid membranes correlated well with the binding data obtained by FCS and IFC techniques. The reduced photodynamic activity of AlPcN4 with neutral membranes violating this correlation was attributed to the concentration quenching of singlet excited states as proved by the data on the AlPcN4 fluorescence quenching. 相似文献
107.
Wendy A. Douglass Robert H. Hyland Christopher D. Buckley Aymen Al-Shamkhani Jacqueline M. Shaw Sarah L. Scarth David L. Simmons S.K.Alex Law 《FEBS letters》1998,440(3):125
The cysteine-rich region (CRR) of the β2 integrin subunit was replaced by that of β1 to give the chimera β2NV1. β2NV1 can combine with αL to form a variant leukocyte-function-associated antigen (LFA)-1 on COS cell surface, suggesting that the specificity of the β2 interaction with αL does not lie in the CRR. Unlike those expressing wild-type LFA-1, COS cells expressing αLβ2NV1 are constitutively active in intercellular adhesion molecule (ICAM)-1 adhesion. These results suggest that activation of LFA-1 involves the release of an intramolecular constraint, which is maintained, in part, by the authentic β2 CRR. 相似文献
108.
109.
110.
The ability to metabolically label proteins with 35S-methionine is critical for the analysis of protein synthesis and turnover. Despite the importance of this approach, however, efficient labeling of proteins in vivo is often limited by a low number of available methionine residues, or by deleterious side-effects associated with protein overexpression. To overcome these limitations, we have created a methionine-rich variant of the widely used HA tag, called HAM, for use with ectopically expressed proteins. Here we describe the development of a series of vectors, and corresponding antisera, for the expression and detection of HAM-tagged proteins in mammalian cells. We show that the HAM tag dramatically improves the sensitivity of 35S-methionine labeling, and permits the analysis of Myc oncoprotein turnover even when HAM-tagged Myc is expressed at levels comparable to that of the endogenous protein. Because of the improved sensitivity provided by the HAM tag, the vectors and antisera described here should be useful for the analysis of protein synthesis and destruction at physiological levels of protein expression. 相似文献