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   714篇
  免费   40篇
  国内免费   2篇
化学   661篇
晶体学   5篇
力学   3篇
数学   3篇
物理学   84篇
  2022年   3篇
  2021年   4篇
  2020年   8篇
  2019年   9篇
  2018年   3篇
  2017年   5篇
  2016年   19篇
  2015年   20篇
  2014年   11篇
  2013年   35篇
  2012年   60篇
  2011年   75篇
  2010年   29篇
  2009年   19篇
  2008年   63篇
  2007年   42篇
  2006年   48篇
  2005年   36篇
  2004年   39篇
  2003年   44篇
  2002年   37篇
  2001年   3篇
  2000年   14篇
  1999年   6篇
  1998年   5篇
  1997年   2篇
  1996年   4篇
  1995年   7篇
  1994年   3篇
  1992年   12篇
  1991年   7篇
  1990年   5篇
  1989年   3篇
  1988年   7篇
  1987年   4篇
  1986年   6篇
  1985年   6篇
  1984年   4篇
  1983年   4篇
  1982年   2篇
  1981年   4篇
  1980年   6篇
  1979年   12篇
  1978年   2篇
  1977年   2篇
  1975年   2篇
  1974年   2篇
  1973年   5篇
  1971年   4篇
  1967年   1篇
排序方式: 共有756条查询结果,搜索用时 31 毫秒
101.
It is shown that Boltzmann's equation written in terms of microscopic density (namely the unaveraged Boltzmann function) has a wider range of validity as well as finer resolvability for fluctuations than the conventional Boltzmann equation governing Boltzmann's function. In fact the new Boltzmann equation for ideal gases has implications as a microscopically exact continuity equation like Klimontovich's equation for plasmas, and can be derived without invoking any statistical concepts, e.g., distribution functions, or molecular chaos. The Boltzmann equation in the older formalism is obtained by averaging this equation only under a restricted condition of the molecular chaos. The new Boltzmann equation is seen to contain information comparable with Liouville's equation, and serves as a master kinetic equation. A new hierarchy system is formulated in a certain parallelism to the BBGKY hierarchy. They are shown to yield an identical one-particle equation. The difference between the two hierarchy systems first appears in the two-particle equation. The difference is twofold. First, the present formalism includes thermal fluctuations that are missing in the BBGKY formalism. Second, the former allows us to formulate multi-time correlations as well, whereas the latter is restricted to simultaneous correlation. These two features are favorably utilized in deriving the Landau-Lifshitz fluctuation law in a most straightforward manner. Also, equations describing the nonequilibrium interaction between thermal and fluid-dynamical fluctuations are derived.  相似文献   
102.
103.
104.
105.
The reactivity of neurotransmitters toward hydrogen abstraction by an active oxygen species (the cumylperoxyl radical) is comparable to that of a strong antioxidant such as catechin due to the strong intramolecular hydrogen bonding, which has been successfully detected by ESR.  相似文献   
106.
Photoinduced electron transfer of DNA as well as DNA bases with 9-mesityl-10-methylacridinium ion results in formation of all types of DNA base radical cations, which have been detected as the transient absorption spectra measurements, leading to efficient DNA cleavage in the absence of O2.  相似文献   
107.
The anionic organic dye, zincon, was found to be a colorimetric probe for spermine and spermidine at pH 4.0 in pure aqueous solution through its aggregation by electrostatic interactions with them. The addition of spermine and spermidine led to bathochromic shifts with color changes from yellow to purple and dark brown, respectively, while other amines and basic amino acids induced no or minimal spectral and color changes. From Job’s plot and titration experiments, zincon interacted with spermine (+4 charges) and spermidine (+3 charges) in 4:1 and 3:1 stoichiometric ratios, respectively, indicating that each positive charge was bound to one zincon molecule. The detection limits were determined to be 25.1 for spermine and 30.7 nM for spermidine, which were sufficient below the critical concentration for cancer diagnosis. The results indicated that zincon can be a good candidate for simple, convenient colorimetric detection of spermine and spermidine in aqueous solution.  相似文献   
108.
Dark-spot formation by vector beams   总被引:1,自引:0,他引:1  
Kozawa Y  Sato S 《Optics letters》2008,33(20):2326-2328
Dark-spot formation is demonstrated by calculating electric-field distribution near the focus produced by focusing higher-order transverse-mode vector beams with radial and azimuthal polarizations in addition to Laguerre-Gaussian beams with linear and circular polarizations. The size of the dark spot in the radial direction varies from one beam to another, but the size in the axial direction is almost the same. The radially polarized TM02-mode beam is predicted to form a dark spot solely by an axial electric field.  相似文献   
109.
An asymmetric total synthesis of the guaiane sesquiterpene (?)‐englerin A, a potent and selective inhibitor of the growth of renal cancer cell lines, was accomplished. The basis of the approach is a highly diastereo‐ and enantioselective carbonyl ylide cycloaddition with an ethyl vinyl ether dipolarophile under catalysis by dirhodium(II) tetrakis[N‐tetrachlorophthaloyl‐(S)‐tert‐leucinate], [Rh2(S‐TCPTTL)4], to construct the oxabicyclo[3.2.1]octane framework with concomitant introduction of the oxygen substituent at C9 on the exo‐face. Another notable feature of the synthesis is ruthenium tetraoxide‐catalyzed chemoselective oxidative conversion of C9 ethyl ether to C9 acetate.  相似文献   
110.
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