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   358篇
  免费   22篇
  国内免费   368篇
化学   537篇
晶体学   5篇
力学   29篇
综合类   3篇
数学   39篇
物理学   135篇
  2021年   2篇
  2020年   3篇
  2019年   8篇
  2018年   3篇
  2017年   3篇
  2016年   4篇
  2015年   4篇
  2014年   4篇
  2013年   19篇
  2012年   12篇
  2011年   27篇
  2010年   11篇
  2009年   20篇
  2008年   6篇
  2007年   11篇
  2006年   15篇
  2005年   16篇
  2004年   22篇
  2003年   25篇
  2002年   29篇
  2001年   16篇
  2000年   46篇
  1999年   106篇
  1998年   100篇
  1997年   70篇
  1996年   66篇
  1995年   3篇
  1993年   19篇
  1992年   3篇
  1991年   4篇
  1988年   5篇
  1987年   2篇
  1985年   3篇
  1984年   3篇
  1983年   5篇
  1981年   2篇
  1979年   2篇
  1978年   6篇
  1977年   4篇
  1976年   4篇
  1975年   6篇
  1973年   2篇
  1970年   2篇
  1965年   4篇
  1954年   1篇
  1948年   1篇
  1942年   1篇
  1939年   1篇
  1934年   1篇
  1933年   3篇
排序方式: 共有748条查询结果,搜索用时 15 毫秒
101.
Mar?elja's theory of a superconductor without long-range order is cast in a microscopic form. As a consequence, it is found that such a superconductor is gapless. Therefore, measurements of the tunneling density of states should provide a test of this theory.  相似文献   
102.
The binary fission process in 159Tb and natAg induced by 600 MeV protons has been investigated yielding fission cross sections (1.9 and 1.0 mb, respectively) and mean values of the total kinetic energies (100 and 62 MeV, respectively).  相似文献   
103.
The mass distributions from the binary fission of Ag, La and Tb induced by 600 MeV protons are presented. The experimental results are compared with the predictions of macroscopic theories, in particular the version of the liquid drop model including dynamical and statistical effects.  相似文献   
104.
Mass-separated ion beams of the alkali elements Na, K, and Fr, and of the element Tl, were produced by bombarding a uranium target with 600 MeV protons, 890 MeV3He2 +, and 936 MeV12C4 +. Isotopic production yields are reported. In the case of the12C beam, these are thick target yields. Absolute cross-sections for the proton beam data were deduced by normalizing the delay-time corrected yield curves to measured cross-sections. For products farthest away from stability, the3He2 + beam generally gives the highest yields.  相似文献   
105.
<正>We describe a mobile molecular Doppler wind lidar(DWL) based on double-edge technique for wind measurement of altitudes ranging from 10 to 40 km.A triple Fabry-Perot etalon is employed as a frequency discriminator to determine the Doppler shift proportional to the wind velocity.The lidar operates at 355 nm with a 45-cm-aperture telescope and a matching azimuth-over-elevation scanner that provides full hemispherical pointing.To guarantee wind accuracy,a single servo loop is used to monitor the outgoing laser frequency to remove inaccuracies due to the frequency drift of the laser or the etalon.The standard deviation of the outgoing laser frequency drift is 6.18 MHz and the corresponding velocity error is 1.11 m/s.The wind profiles measured by the DWL are in good agreement with the results of the wind profile radar(WPR).Evaluation is achieved by comparing at altitudes from 2 to 8 km.The relative error of horizontal wind speed is from 0.8 to 1.8 m/s in the compared ranges.The wind accuracy is less than 6 m/s at 40 km and 3 m/s at 10 km.  相似文献   
106.
Atomistic simulations are reported of a model of CO2 in water. CO2 is modelled by partial charges and Lennard-Jones interaction sites on each atom; the SPC/E model for water is used. Good agreement with experiment is found for the translational diffusion constants. The variation of the dynamics with the potential parameter was investigated. As expected, the orientational correlation times increase as the magnitude of the quadrupole moment is increased, but the translational diffusion constants are found to be surprisingly insensitive to the magnitude of the CO2 quadrupole moment. The translational friction coefficient was resolved into electrostatic, Lennard-Jones and cross-terms; the Lennard-Jones contribution is found to be the largest. Varying the Lennard-Jones size parameter affects both translational and reorientational motion. In order to try to understand these results further, the variation of solvation free energy was investigated and the solvent structure around carbon dioxide was examined as the electrostatic and Lennard-Jones parameters were changed. The temperature dependence of the self-diffusion constant of pure SPC/E water was determined.  相似文献   
107.
We consider a mixture of N ideal, polytropic gases. Each species is described by a distribution function fi(t, x, v, I) ≥ 0, 1 ≤ i ≤ N, defined on , and its evolution is governed by a Boltzmann-type equation. In order to recover the energy law of polytropic gases, the authors of [4] proposed a kinetic model in the framework of a weighted L1 space. Another approach has been developed in [3] in the context of polyatomic gases. Following this previous lead, our model provides a L2 framework in both variables v and I, to eventually perform a mathematical study of the diffusion asymptotics, as it was done in [2] for a model without energy exchange. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   
108.
Three new ruthenium(II)-arene halido complexes, [(η6-p-cymene) RuX(L)] (1–3), were synthesized in a reaction of [(η6-p-cymene)RuX2]2 with 5-chloro-1H-benzimidazole-2-carboxylic acid (HL) in ethanol (X = Cl (1), Br (2), I (3)). The complexes were characterized by elemental analysis, mass spectrometry, IR, 1H and 13C NMR spectroscopy. The cytotoxic activity of the ligand precursor and its ruthenium complexes was tested by MTT assay in human cancer cell lines: lung adenocarcinoma (A549), myelogenous leukemia (K562) as well as in one normal human fetal lung fibroblast cell line (MRC-5). The results show that ruthenium(II)-arene complexes possess enhanced cytotoxicity when compared to HL in the range of concentrations up to 300 µM. In terms of halido ligand substitution, cytotoxic activity toward A549 and K562 cell lines in 1–3 serie significantly increased (e.g., IC50 values for K562: 1: 205.76 µM; 2: 174.77 µM; 3: 83.97 µM). All studied compounds were found to be ineffective toward MRC-5. Hydrolysis of 1–3 was followed by UV-vis spectroscopy at 25?°C, revealing ligand-substitution reactions at the Ru(II) center. Compounds 2 and 3 underwent rapid hydrolysis ranging from a few minutes for the aquation to ca. 20?min, confirming typical Ru-arene behavior in aqueous solutions.  相似文献   
109.
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