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   798篇
  免费   27篇
  国内免费   5篇
化学   628篇
晶体学   14篇
力学   3篇
数学   37篇
物理学   148篇
  2023年   3篇
  2022年   4篇
  2021年   9篇
  2020年   6篇
  2019年   13篇
  2018年   4篇
  2016年   19篇
  2015年   19篇
  2014年   19篇
  2013年   30篇
  2012年   34篇
  2011年   39篇
  2010年   25篇
  2009年   28篇
  2008年   36篇
  2007年   45篇
  2006年   44篇
  2005年   52篇
  2004年   32篇
  2003年   37篇
  2002年   36篇
  2001年   15篇
  2000年   9篇
  1999年   17篇
  1998年   6篇
  1997年   17篇
  1996年   6篇
  1995年   10篇
  1993年   7篇
  1992年   6篇
  1991年   8篇
  1990年   7篇
  1989年   4篇
  1988年   7篇
  1987年   8篇
  1986年   12篇
  1985年   12篇
  1984年   11篇
  1983年   9篇
  1982年   18篇
  1981年   7篇
  1980年   8篇
  1979年   11篇
  1978年   16篇
  1977年   12篇
  1976年   11篇
  1975年   7篇
  1974年   8篇
  1973年   11篇
  1967年   3篇
排序方式: 共有830条查询结果,搜索用时 15 毫秒
1.
Journal of Thermal Analysis and Calorimetry - Nitrocellulose (NC) is prone to spontaneous decomposition with exothermic heat release and thus is generally evaluated for stability during the storage...  相似文献   
2.
Gold nanoparticles with different mean sizes were formed on antimony-doped tin oxide nanocrystals by the temperature-varied deposition-precipitation method (Au/ATO NCs). Au/ATO NCs possess strong absorption in the near-infrared region due to Drude excitation in addition to the localized surface plasmon resonance (LSPR) of AuNPs around 530 nm. Au/ATO NCs show thermally activated catalytic activity for the oxidation of cinnamyl alcohol to cinnamaldehyde by hydrogen peroxide. The catalytic activity increases with a decrease in the mean Au particle size (dAu) at 5.3 nm≤dAu≤8.2 nm. Light irradiation (λex >660 nm, ∼0.5 sun) of Au/ATO NCs increases the rate of reaction by more than twice with ∼95 % selectivity. Kinetic analyses indicated that the striking enhancement of the reaction stems from the rise in the temperature near the catalyst surface of ∼30 K due to the photothermal effect of the ATO NCs.  相似文献   
3.
4.
5.
The self-restoration properties in VWP networks are investigated with optimization about spare wavelength by simulations. Rapid restoration can be achieved by selection of rerouting path with long delay and no delay-limitation for new routes.  相似文献   
6.
We have investigated the spin-1 Ising model on the simple cubic lattice with bilinear, biquadratic interaction and anisotropic energy (BEG model). We have been specially interested in the case of antiferro biquadratic interaction, because the interaction will cause the competition with bilinear interaction and anisotropy. A two-sublattice ordering, so called the staggered quadrupole (SQ) phase, occurs as long as biquadratic interaction is negative large enough. We have obtained a full phase diagram in the whole interaction parameter space (for the positive bilinear interaction) by the Bethe approximation, and found several kinds of phase transitions, such as successive, re-entrant and double re-entrant transitions. These transitions are also confirmed by Monte Carlo simulations on simple cubic lattices.  相似文献   
7.
8.
Katsumi Kubota 《Tetrahedron》2006,62(49):11397-11401
The first highly enantioselective silicon Lewis acid catalyst for an asymmetric organic transformation has been developed. The catalyst derives its activity from the strain induced in the silicon center by virtue of being constrained in a five-membered ring. A simple tridentate ligand has been developed and the derived chlorosilane complex catalyzes the Diels-Alder cycloaddition of methacrolein and cyclopentadiene with 94% ee.  相似文献   
9.
An approach to deduce the mechanism of stabilization of the hybrid-derived populations in the Ohomopterus ground beetles has been made by comparative studies on the phylogenetic trees of the mitochondrial and nuclear DNA. A phylogenetic tree based on the internal transcribed spacer (ITS) of nuclear ribosomal gene roughly reflects the relations of morphological species group, while mitochondrial NADH dehydrogenase subunit 5 (ND5) gene shows a considerable different topology on the tree; there exist several geographically-linked lineages, most of which consist of more than one species. These results suggest that the replacement of mitochondria has occurred widely in the Ohomopterus species. In most cases, hybridization is unidirectional, i.e., the species A (♂) hybridized with another species B (♀) and not vice versa, with accompanied replacement of mitochondria of A by those of B. The results also suggest that partial or complete occupation of the distribution territory by a hybrid-derived morphological species. The morphological appearance of the resultant hybrid-derivatives are recognized as that of the original species A. Emergence of a morphological new species from a hybrid-derived population has been exemplified.  相似文献   
10.
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