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   308篇
  免费   17篇
化学   214篇
晶体学   2篇
力学   11篇
数学   31篇
物理学   67篇
  2023年   4篇
  2022年   5篇
  2021年   4篇
  2019年   7篇
  2018年   2篇
  2017年   3篇
  2016年   9篇
  2015年   7篇
  2014年   4篇
  2013年   10篇
  2012年   22篇
  2011年   16篇
  2010年   6篇
  2009年   14篇
  2008年   27篇
  2007年   16篇
  2006年   13篇
  2005年   24篇
  2004年   12篇
  2003年   17篇
  2002年   13篇
  2001年   5篇
  2000年   2篇
  1999年   3篇
  1998年   3篇
  1997年   6篇
  1996年   3篇
  1995年   3篇
  1994年   4篇
  1993年   2篇
  1990年   3篇
  1989年   2篇
  1988年   3篇
  1987年   3篇
  1985年   6篇
  1984年   4篇
  1981年   4篇
  1980年   2篇
  1979年   2篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1974年   2篇
  1971年   2篇
  1970年   2篇
  1969年   3篇
  1965年   1篇
  1964年   2篇
  1962年   1篇
  1961年   1篇
排序方式: 共有325条查询结果,搜索用时 15 毫秒
61.
Dispersed water droplets are often seen in environmental air flows in rain, cloud, mist, sea spray and so on. It is therefore of great importance to precisely estimate heat transfer between water droplets and atmospheric air in developing a reliable climate model. The purpose of this study is to fabricate the measurement system for the temperature of a small water droplet in air flow under the controlled relative humidity condition and to investigate the effect of relative humidity on heat transfer across the surface of an evaporating water droplet in air flow. The results show that the droplet temperature decreases in the low-relative-humidity condition, whereas it increases in the high-relative-humidity condition. Nusselt number on the droplet surface is not affected by the relative humidity.  相似文献   
62.
9,10-Dicyanoanthracene-sensitized photo-oxygenation of 2,2-diaryl-3-(2,2-diarylvinyl)oxiranes 3 in acetonitrile did not afford the corresponding 1,2,4-trioxepines 4, but 1,2,4-trioxolanes 7. The structural assignment of 7 was reported, and the mechanism of the formation of 7 was proposed.  相似文献   
63.
Summary: A numerical method is presented for simulating charged colloidal dispersions in electrolyte solutions. Utilizing a smoothed profile for colloid‐solvent boundaries, efficient mesoscopic simulations are enabled for modeling dispersions of many colloidal particles exhibiting many‐body electrostatic interactions. The validity of the method was examined for simple colloid geometries, and the efficiency was demonstrated by calculating stable structures of two‐dimensional dispersions, which resulted in the formation of colloidal crystals.

Formation of a charged colloidal crystal.  相似文献   

64.
Expressions of the flows of atoms A and B of a binary system in a crystal are derived as the response to the imposed gradients of temperature and chemical potentials. The formulation is done using the pair approximation of the Path Probability Method of irreversible statistical mechanics and atomic migration is assumed to be via the vacancy mechanism. The energy carried by photons (and electrons) under the temperature gradient is assumed to be independent of the atomic flux. For the case near equilibrium, linear relations are derived among the atomic fluxes, the energy flux (associated with atomic flux) and the gradients. The Onsager reciprocal relations are proved to hold among the coefficients, including those related to energy flows. The heat of transport (energy carried by a diffusing atom) and the heat conduction due to atomic flux are thus unambigously derived.  相似文献   
65.
66.
Benzylic acetates reacted with arylboronic acids in the presence of a DPEphos-[Pd(eta3-C3H5)Cl]2 catalyst when tert-amyl alcohol was used as a solvent, and the catalytic cross-couplings produced diarylmethanes in high yields (up to 94% isolated yield).  相似文献   
67.
A high-performance liquid chromatographic method has been developed for the quantification of 1-hydroxypyrene (1-OHP) in human urine using deuterated 1-hydroxypyrene ([2H9]1-OHP) as an internal standard with fluorescence detection. [2H9]1-OHP was prepared enzymatically from deuterated pyrene ([2H10]Pyr) with cytochrome P450 1A1. It eluted immediately prior to non-deuterated 1-OHP on alkylamide-type reversed-phase columns and had nearly the same fluorescence characteristics as non-deuterated 1-OHP. The detection limit was 0.1 microg/L and the calibration range was from 1 to 100 nmol/L. Urine sample treatment involved enzymatic hydrolysis followed by solid-phase extraction using Sep-Pak C18 cartridges. The proposed method was used to determine urinary 1-OHP in smokers and non-smokers.  相似文献   
68.
Summary LetX be a positive random variable with the survival function and the densityf. LetX have the moments μ=E(X) and μ2=E(X 2) and put ε=|1-μ2/2μ2|. Put and . It is proved that the following inequalities hold: , for allx>0, ifq(x) is monotone and that , ifq 1 (x) is monotone. It is also shown that Brown's inequality which holds wheneverq 1 (x) is increasing is not valid in general whenq 1 is decreasing. The Institute of Statistical Mathematics  相似文献   
69.
Cyclotrimerization of two different, unsymmetrical acetylenes and p-toluenesulfonylnitrile with a divalent titanium alkoxide reagent, Ti(O-i-Pr)4/2 i-PrMgCl, yielded single pyridyltitanium compounds in a highly selective manner. These metalated pyridines were confirmed by deuteriolysis to give the corresponding deuterated pyridines and underwent iodinolysis and copper-catalyzed alkylation to demonstrate their synthetic utility. Alternatively, a different type of cyclotrimerization of an alkynamide, terminal acetylenes, and alpha-alkoxynitriles mediated by the same titanium(II) alkoxide again proceeded in a highly selective manner to give single pyridines having a titanated side chain.  相似文献   
70.
Various 8-hydroxy-5-deazaflavin derivatives were synthesized as the model compounds of coenzyme F420-These compounds oxidized benzylamine to benzaldehyde more efficiently than the corresponding 8-unsubstituted 5-deazaflavins.  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