首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   838篇
  免费   20篇
化学   645篇
晶体学   6篇
力学   11篇
数学   32篇
物理学   164篇
  2023年   5篇
  2021年   12篇
  2020年   17篇
  2019年   13篇
  2018年   7篇
  2017年   8篇
  2016年   8篇
  2015年   11篇
  2014年   17篇
  2013年   34篇
  2012年   21篇
  2011年   30篇
  2010年   20篇
  2009年   17篇
  2008年   45篇
  2007年   40篇
  2006年   37篇
  2005年   25篇
  2004年   33篇
  2003年   41篇
  2002年   38篇
  2001年   34篇
  2000年   34篇
  1999年   16篇
  1998年   9篇
  1997年   14篇
  1996年   8篇
  1995年   13篇
  1994年   8篇
  1993年   10篇
  1992年   21篇
  1991年   14篇
  1990年   15篇
  1988年   11篇
  1987年   8篇
  1986年   5篇
  1985年   20篇
  1984年   20篇
  1983年   13篇
  1982年   8篇
  1981年   9篇
  1980年   12篇
  1979年   9篇
  1978年   8篇
  1977年   12篇
  1976年   6篇
  1975年   8篇
  1974年   4篇
  1973年   11篇
  1968年   4篇
排序方式: 共有858条查询结果,搜索用时 15 毫秒
1.
2.
Effects of various cardioactive agents and a water extract of the pilose antler of Cervus nippon var. mantchuricus on periodic beating of cultured myocardial cell sheets were examined by using an image analyzing system. Norepinephrine increased the beating rate and the beating amplitude, whereas digoxin and forskolin enlarged only the beating amplitude. Verapamil and propranolol decreased both the beating rate and the beating amplitude. The water extract of the pilose antler showed no remarkable effects in a standard medium (2.1 mM Ca2+). However, it significantly increased the beating amplitude when the beating was suppressed by replacement with a low calcium medium (0.5 mM Ca2+). A similar effect was found for 70% ethanol-soluble and -insoluble fractions of the extract.  相似文献   
3.
A non-halogen highly flame-retardant 0.9mm optical fiber and 2.0mm simplex optical cord, which are harmonized with the ecosystem, have been developed. The characteristics of them are presented in this paper.  相似文献   
4.
Linear propagation of two pulses through methanol solution of aluminum phthalocyanine chloride is investigated using a modified white-light Michelson interferometer. The observed coherence time of the white light is 6 fs, and the separation between the two-excitation pulses is set to about 10 fs. The excitation is dependent on the phase-relation between the two pulses. We have observed an enhancement of the excitation when the two pulses are in-phase and strong suppression of the excitation when the two pulses are out of phase by π.  相似文献   
5.
6.
7.
8.
9.
Kubo K  Hattori A 《Electrophoresis》2001,22(16):3389-3394
The use of polyamines as electroosmotic modifiers has been shown to be effective in enhancing resolution of protein glycoforms in capillary zone electrophoresis (CZE) using a bare capillary tube. In this study, effectiveness was evaluated by using a polyacrylamide-coated capillary tube instead of a bare capillary tube. Electropherograms obtained in the presence of polyamines were inferior to those obtained in their absence with respect to resolution. Electrophoretic mobility of the proteins decreased and their peaks were broadened by polyamines bound to them. This unfavorable effect was dependent on both the species of polyamines and the pH values of the electrolyte buffer. The reduction of resolution caused by polyamines was in the following order: spermidine (SPD) approximately spermidine-tri-hydrochloride (SPD-HCI) > putrescine (PUT) > hexamethonium chloride (HMC). The observed effect can be ascribed to the formation of complexes between the proteins and the polyamines. In addition, for the bare capillary tube the complexes showed interaction with the inner surface, resulting in local suppression of electroosmosis and poor resolution. The high resolution obtained in the coated capillary tube was reduced in the presence of the polyamines. Thus, the use of the polyamines has a negative effect on the analysis of protein microheterogeneity as a result of protein-polyamine interaction.  相似文献   
10.
The INDO calculations were performed on the three azines: pyridazine, pyrimidine, and pyrazine. The cannonical molecular orbitais obtained by these calculations were then transformed into the localized molecular orbitals. With the use of the localized molecular orbitals, the variation in the lone-pair orbital energies of these molecules were pursued in the light of the through-space and/or the through-bond interactions between the specified localized molecular orbitals in a molecule selectively. The interactions were expressed by the summation of several terms: through-space, through-bond, through-virtuals and coupling terms.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号