全文获取类型
收费全文 | 12562篇 |
免费 | 1456篇 |
国内免费 | 1041篇 |
专业分类
化学 | 9056篇 |
晶体学 | 129篇 |
力学 | 544篇 |
综合类 | 110篇 |
数学 | 1613篇 |
物理学 | 3607篇 |
出版年
2024年 | 34篇 |
2023年 | 193篇 |
2022年 | 338篇 |
2021年 | 364篇 |
2020年 | 401篇 |
2019年 | 389篇 |
2018年 | 319篇 |
2017年 | 343篇 |
2016年 | 578篇 |
2015年 | 501篇 |
2014年 | 700篇 |
2013年 | 947篇 |
2012年 | 1090篇 |
2011年 | 1104篇 |
2010年 | 752篇 |
2009年 | 682篇 |
2008年 | 776篇 |
2007年 | 660篇 |
2006年 | 557篇 |
2005年 | 518篇 |
2004年 | 457篇 |
2003年 | 429篇 |
2002年 | 434篇 |
2001年 | 296篇 |
2000年 | 198篇 |
1999年 | 233篇 |
1998年 | 167篇 |
1997年 | 138篇 |
1996年 | 152篇 |
1995年 | 112篇 |
1994年 | 118篇 |
1993年 | 117篇 |
1992年 | 93篇 |
1991年 | 94篇 |
1990年 | 63篇 |
1989年 | 72篇 |
1988年 | 53篇 |
1987年 | 47篇 |
1986年 | 50篇 |
1985年 | 48篇 |
1984年 | 41篇 |
1983年 | 20篇 |
1982年 | 26篇 |
1981年 | 25篇 |
1980年 | 28篇 |
1979年 | 21篇 |
1978年 | 26篇 |
1977年 | 30篇 |
1975年 | 21篇 |
1957年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
The graded Hecke algebra for a finite Weyl group is intimately related to the geometry of the Springer correspondence. A
construction of Drinfeld produces an analogue of a graded Hecke algebra for any finite subgroup of GL(V). This paper classifies all the algebras obtained by applying Drinfeld's construction to complex reflection groups. By giving
explicit (though nontrivial) isomorphisms, we show that the graded Hecke algebras for finite real reflection groups constructed
by Lusztig are all isomorphic to algebras obtained by Drinfeld's construction. The classification shows that there exist
algebras obtained from Drinfeld's construction which are not graded Hecke algebras as defined by Lusztig for real as well
as complex reflection groups.
Received: July 25, 2001 相似文献
32.
R. Ochoa-Land?&#x;n M. Flores-Acosta R. Ram?&#x;rez-Bon H. Arizpe-Chávez F.F. Castillón-Barraza 《Journal of Physics and Chemistry of Solids》2003,64(11):2245-2251
CdS clusters were synthesized in A type zeolite by reaction in alkaline aqueous solution at temperatures from 30 to 70 °C. The optical properties of the samples were studied by diffuse reflectance and photoluminescence spectroscopy. Their crystalline structure and morphology were studied by X-ray diffraction and by transmission and scanning electron microscopy. We found that at lower temperatures the CdS clusters are encapsulated in the zeolite cages. We compared the properties of these clusters with those encapsulated in the cages of zeolites X and Y, prepared by similar methods. CdS clusters smaller than the CdS exciton diameter are also formed outside the cages in the zeolite matrix. The size of these clusters increases with temperature producing a red-shift of the absorption edge in the optical absorption spectra. 相似文献
33.
Bruzón M. S. Gandarias M. L. Muriel C. Ramírez J. Saez S. Romero F. R. 《Theoretical and Mathematical Physics》2003,137(1):1367-1377
We use the classical and nonclassical methods to obtain symmetry reductions and exact solutions of the (2+1)-dimensional integrable Calogero–Bogoyavlenskii–Schiff equation. Although this (2+1)-dimensional equation arises in a nonlocal form, it can be written as a system of differential equations and, in potential form, as a fourth-order partial differential equation. The classical and nonclassical methods yield some exact solutions of the (2+1)-dimensional equation that involve several arbitrary functions and hence exhibit a rich variety of qualitative behavior. 相似文献
34.
35.
Ru Ju Wang Feng Ying LiTing Zhang Deng Ji Fang WangHong Chen Chang Qing Jin 《Solid State Communications》2003,127(1):47-50
Using pulse echo overlap measurement, the elastic behavior of amorphous carbon has been studied at ambient and low temperatures. The smaller ratio B/G of the bulk modulus to shear modulus and smaller Poisson's ratio σ at room temperature indicate that there is an intrinsic stiffening of transverse acoustic phonons in the amorphous carbon. The acoustic velocity and attenuation for longitudinal modes have been measured between 2.1 and 300 K at three frequencies of 7, 21 and 35 MHz, respectively. Their frequency and temperature dependence are observed. The elastic constant C11 increases with decreasing temperature and show enhanced stiffening at low temperatures. In the 130-220 K region, the abnormal change and effect of longitudinal velocity and attenuation with temperature and frequency, and a phase transition associated with structure relaxations are discussed. 相似文献
36.
The paper presents results of perturbative calculations for nucleon Compton scattering. The results are given for the real incoming photon and for the virtual incoming photon. 相似文献
37.
作为H.F.Trotter[3]中一个结果的模拟,本文给出实二次函数域K中基本单位ε的范为N(ε)=g的一些充分必要条件,其中g为K的常数域Fq的非零乘法群Fq^*的生成元(2├q)。利用图论的语言,本文还给出了N(ε)=g的一些充分条件,这些条件对于数域也同样地适用,从而推广了Trotter[3]和前人工作中关于充分条件的结果。 相似文献
38.
Muon irradiation of pure liquid 3‐chloropropene, CH2=CH-CH2Cl, yields a primary radical, \dot\mboxCH2-CHMu-CH2Cl, and a secondary radical, MuCH2-\rm\dot\mboxCH-CH2Cl. 2‐methyl‐3‐chloropropene yields only the tertiary radical, MuCH2-\rm\dot\mboxC(CH3)-CH2Cl. These three chloroalkyl radicals have been characterized by μSR and μLCR, and the hyperfine coupling constants (hfcs)
have been determined over a range of temperatures, either in the pure liquid precursor or in concentrated solution. The temperature
variation of the hfcs has been analyzed to obtain estimates of the barrier to internal rotation about the C_\alpha-C_\beta
axis for various alkyl groups, and also their minimum energy conformations, i.e. their orientations with respect to the axis
of the 2p_z orbital of the unpaired electron. The tertiary radical is particularly interesting because all three methyl‐like
groups, -CH3,-CH2Cl and -CH2Mu, are represented. The results can be compared to electron spin resonance data for analogous radicals, to provide information
on the effects of Mu substitution for H.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
39.
40.
Measurement of small-signal and large-signal responses of packaged laser modules at high temperature
Ning Hua Zhu Ji Min Wen Hai Peng Song Shang Jian Zhang Liang Xie 《Optical and Quantum Electronics》2006,38(15):1245-1257
In this paper, the pulsed injection method is extended to measure the chip temperature of various packaged laser modules,
such as the DFB laser modules, the FP laser modules, and the EML laser modules. An optimal injection condition is obtained
by investigating the dependence of the lasing wavelength on the width and period of the injection pulse in a relatively wide
temperature range. The small-signal frequency responses and large-signal performances of packaged laser modules at different
chip temperature are measured. The adiabatic small-signal modulation characteristics of packaged LD are first extracted. In
the large-signal measurement, the effects of chip temperature, bias current and driving signal on the performances of the
laser modules are discussed. It has been found that the large-signal performances of the EML modules depend on the different
red-shift speeds of the DFB and EAM sections as chip temperature varying, and the optimal characteristics may be achieved
at higher temperature. 相似文献