全文获取类型
收费全文 | 4265篇 |
免费 | 141篇 |
国内免费 | 13篇 |
专业分类
化学 | 3366篇 |
晶体学 | 110篇 |
力学 | 198篇 |
数学 | 163篇 |
物理学 | 582篇 |
出版年
2023年 | 28篇 |
2022年 | 41篇 |
2021年 | 69篇 |
2020年 | 82篇 |
2019年 | 109篇 |
2018年 | 113篇 |
2017年 | 80篇 |
2016年 | 151篇 |
2015年 | 103篇 |
2014年 | 186篇 |
2013年 | 453篇 |
2012年 | 301篇 |
2011年 | 268篇 |
2010年 | 176篇 |
2009年 | 152篇 |
2008年 | 241篇 |
2007年 | 231篇 |
2006年 | 171篇 |
2005年 | 174篇 |
2004年 | 162篇 |
2003年 | 144篇 |
2002年 | 117篇 |
2001年 | 42篇 |
2000年 | 47篇 |
1999年 | 36篇 |
1998年 | 23篇 |
1997年 | 26篇 |
1996年 | 42篇 |
1995年 | 27篇 |
1994年 | 31篇 |
1993年 | 31篇 |
1992年 | 32篇 |
1991年 | 28篇 |
1990年 | 40篇 |
1989年 | 33篇 |
1988年 | 26篇 |
1987年 | 32篇 |
1986年 | 29篇 |
1985年 | 40篇 |
1984年 | 44篇 |
1983年 | 32篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 24篇 |
1979年 | 18篇 |
1978年 | 15篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1975年 | 20篇 |
1974年 | 10篇 |
排序方式: 共有4419条查询结果,搜索用时 31 毫秒
991.
992.
Indium trichloride (20 mol%) in nitromethane permits ionic Diels–Alder reaction of a variety of 2,3-olefinic acetals to form the corresponding cycloadducts in good yields with good endo selectivities. 相似文献
993.
994.
Anand G. Patil Dilip Reddy Russell D'Souza Anagha Damre 《Biomedical chromatography : BMC》2010,24(6):620-625
A simple, sensitive and specific reverse‐phase high‐performance liquid chromatographic (RP‐HPLC) method with fluorescence detection was developed for quantitation of quinidine from HBSS buffer. The method was applicable in the bi‐directional transport assay for evaluation of the inhibitory effect of test compounds on P‐glycoprotein‐mediated quinidine transport; quinidine was used as a probe P‐glycoprotein substrate. The calibration curve was linear (correlation coefficient ≥99) in the range 0.30–100.00 nm. The method was validated and is specific and sensitive with limit of quantitation of 300 pm for quinidine. The method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions where the analyte was found to be stable. The applicability and reliability of the analytical method was evaluated by successful demonstration of efflux ratio (PappB → A/PappA → B) in the Caco‐2 cell monolayer efflux assay. The efflux ratio for quinidine (100 nm) alone was 10.8, which reduced to less than 2 in the presence of the classical P‐gp inhibitors verapamil and ketoconazole (100 μm each). Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
995.
Vadde Ramakrishna Sake Rajasekhar Lokireddy Sudarsana Reddy 《Applied biochemistry and biotechnology》2010,160(1):63-71
Proteolytic enzymes play a central role in the biochemical mechanism of germination. The present study reported the presence
of Zn2+-dependent endoproteases in the dry seeds of grass pea (Lathyrus sativus L.) with maximum caseinolytic activity observed at pH 8.0. Studies with class-specific inhibitors (specific for cysteine,
serine, aspartate, and metalloproteases) on crude extract identified the inhibitory effect of 1,10-phenanthroline. This inhibitory
effect was overcome by addition of Zn2+, not with Fe, Ca, Cu, Mg, or Co and indicates that the protease is Zn2+ dependent. This metalloprotease was further characterized by attempting gelatin-PAGE zymography and observed three distinct
zones of proteolytic activity with higher mobility. The protease fraction consisted of three isoforms as evidenced by the
appearance of three different bands on gelatin-PAGE zymogram. We also purified these proteases to 110-fold by a three-step
procedure comprising crude extract from dry seeds, (NH4)2SO4 fractionation, and casein–alginate affinity chromatography. The molecular mass of isoforms of metalloproteases is 25, 18,
and 14 kDa. 相似文献
996.
997.
998.
Srinivasa Reddy Mothe 《Tetrahedron letters》2010,51(16):2136-459
A method to prepare a variety of substituted 3-acyl-5-hydroxybenzofurans efficiently that relies on copper(II) triflate-catalyzed cycloaddition of unactivated 1,4-benzoquinones with 1,3-dicarbonyl compounds is reported. The reaction was shown to be operationally straightforward and proceeds expediently under mild conditions to give the corresponding products in good to excellent yields (up to 95%) and with complete regioselectivity. 相似文献
999.
1000.