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   2399篇
  免费   75篇
  国内免费   20篇
化学   1425篇
晶体学   18篇
力学   34篇
数学   423篇
物理学   594篇
  2023年   17篇
  2022年   48篇
  2021年   64篇
  2020年   49篇
  2019年   67篇
  2018年   63篇
  2017年   57篇
  2016年   79篇
  2015年   90篇
  2014年   76篇
  2013年   161篇
  2012年   136篇
  2011年   165篇
  2010年   117篇
  2009年   118篇
  2008年   167篇
  2007年   142篇
  2006年   175篇
  2005年   137篇
  2004年   95篇
  2003年   84篇
  2002年   91篇
  2001年   41篇
  2000年   31篇
  1999年   36篇
  1998年   29篇
  1997年   24篇
  1996年   33篇
  1995年   18篇
  1994年   12篇
  1993年   14篇
  1992年   10篇
  1991年   9篇
  1990年   2篇
  1989年   5篇
  1988年   4篇
  1985年   4篇
  1984年   4篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1980年   1篇
  1979年   2篇
  1978年   2篇
  1976年   1篇
  1975年   2篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
  1969年   2篇
排序方式: 共有2494条查询结果,搜索用时 31 毫秒
951.
A new method of 1-fluorosilatrane synthesis on the basis of silicon tetrafluoride complexes obtained from SiO2 is offered. Chemical properties of 1-fluorosilatrane in reactions of nucleophilic substitution are investigated. It is shown that fluorine can be substituted by O-nucleophiles (lithium methoxide, isopropoxide and phenoxide) and C-nucleophile (lithium phenylacetylenide).  相似文献   
952.
This review covers an important domain of p-adic mathematical physics — quantum mechanics with p-adic valued wave functions. We start with basic mathematical constructions of this quantum model: Hilbert spaces over quadratic extensions of the field of p-adic numbers ? p , operators — symmetric, unitary, isometric, one-parameter groups of unitary isometric operators, the p-adic version of Schrödinger’s quantization, representation of canonical commutation relations in Heisenberg andWeyl forms, spectral properties of the operator of p-adic coordinate.We also present postulates of p-adic valued quantization. Here observables as well as probabilities take values in ? p . A physical interpretation of p-adic quantities is provided through approximation by rational numbers.  相似文献   
953.
The DyIII ions in the dimer [Dy2(H2tea)2(O2CPh)4]·2H2O (1) (H3tea = triethanolamine) have the 9-coordinate monocapped square-antiprismatic ligand field environment. Compound 1 shows slow relaxation of magnetization which is observable only with applied magnetic fields. This is consistent with the idea that low-symmetry ligand fields allow for the quantum tunneling of magnetization. This is reflected by the fact that there are no observable maxima in the out-of-phase ac susceptibility above 1.8 K. The {g}-tensor of the DyIII ions {g x = 11, g y = 8.2, g z = 1} further underlying the reduced uniaxiality in this system was determined in electron paramagnetic resonance (X- and Q-band) studies of 1 at temperatures down to 4 K.  相似文献   
954.
The moduli space ${\mathcal {NK}}The moduli space NK{\mathcal {NK}} of infinitesimal deformations of a nearly K?hler structure on a compact 6-dimensional manifold is described by a certain eigenspace of the Laplace operator acting on co-closed primitive (1, 1) forms (cf. Moroianu et al. in Pacific J Math 235:57–72, 2008). Using the Hermitian Laplace operator and some representation theory, we compute the space NK{\mathcal {NK}} on all 6-dimensional homogeneous nearly K?hler manifolds. It turns out that the nearly K?hler structure is rigid except for the flag manifold F(1, 2) = SU3/T 2, which carries an 8-dimensional moduli space of infinitesimal nearly K?hler deformations, modeled on the Lie algebra \mathfraksu3{\mathfrak{su}_3} of the isometry group.  相似文献   
955.
A two-dimensional optical spectrometer is demonstrated using simple optical components. This spectrometer is based on ultrafast two-dimensional (2D) frequency-dispersed pump-probe spectroscopy and can be used for single-shot correlation spectroscopy. To demonstrate functionality of this device, we measure the 2D correlation spectrum of atomic rubidium.  相似文献   
956.
The polarization correlation parameter C nn in the elastic proton-proton scattering was for the first time measured with a high statistical accuracy at 1 GeV using an unpolarized proton beam incident on an unpolarized proton target. Both outgoing protons from the reaction were detected in coincidence by means of a two-arm focusing magnetic spectrometer installed at nonsymmetric angles corresponding to the center-of-mass scattering angle Θcm = 62.25°. The correlation parameter C nn , as well as polarizations P 1 and P 2 of the secondary protons, were measured by means of multiwire proportional chamber polarimeters placed at the focal planes of each spectrometer arm. The obtained data are compared with the predictions of the phase-shift analysis. The connection with the experiment on C nn and polarization measurements in the (p, 2p) reaction on 4He and other light nuclei in similar kinematics is discussed  相似文献   
957.
958.
Eigenvalue problem for Poincare-Steklov-3 integral equation is reduced to the solution of three transcendential equations for three unknown numbers, moduli of pants. The complete list of antisymmetric eigenfunctions of integral equation in terms of Kleinian membranes is given.  相似文献   
959.
Double-differential cross sections of inclusive light-ion (p, d, t, 3He and α) production in carbon induced by 96 MeV neutrons have been measured at eight laboratory angles from 20° to 160° in steps of 20°. Experimental techniques, as well as procedures for data taking and data reduction, are presented. Deduced energy-differential and production cross sections are herewith reported. Experimental cross sections are compared with theoretical reaction model calculations and experimental data in the literature. The measured production cross sections for protons, deuterons, tritons, 3He, and α particles support the trends suggested by data at lower energies. Deduced partial kerma coefficients for carbon are also shown.  相似文献   
960.
Zinc pyrithione is ubiquitous in commercial products particularly antidandruff shampoos. For the efficacy of zinc pyrithione therapeutic cleansers to be assessed accurately, the distribution of particles on the scalp needs to be visualized. Currently, no technique is available which provides the chemical specificity and sensitivity required. Here, we report application of fluorescence‐lifetime imaging microscopy (FLIM) for high‐contrast mapping of zinc pyrithione distribution on the scalp. Characterization of the zinc pyrithione emission by using both one‐photon excitation at five specific wavelengths and two‐photon excitation in the range of 740–820 nm revealed its FLIM fingerprint—a characteristic short average time‐weighted emission lifetime of ΤZnPT = 250 ps. Bandpass‐filtering FLIM signals at ΤZnPT enabled an efficient discrimination between the zinc pyrithione and major endogenous skin species in comparison with that of the conventional reflectance confocal microscopy. Our findings provide means for in vivo high‐sensitivity assaying and high‐contrast imaging of zinc pyrithione in biological systems.  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