全文获取类型
收费全文 | 5138篇 |
免费 | 319篇 |
国内免费 | 259篇 |
专业分类
化学 | 961篇 |
晶体学 | 5篇 |
力学 | 304篇 |
综合类 | 23篇 |
数学 | 3411篇 |
物理学 | 1012篇 |
出版年
2023年 | 59篇 |
2022年 | 84篇 |
2021年 | 117篇 |
2020年 | 91篇 |
2019年 | 108篇 |
2018年 | 94篇 |
2017年 | 120篇 |
2016年 | 115篇 |
2015年 | 115篇 |
2014年 | 217篇 |
2013年 | 415篇 |
2012年 | 262篇 |
2011年 | 304篇 |
2010年 | 280篇 |
2009年 | 370篇 |
2008年 | 407篇 |
2007年 | 384篇 |
2006年 | 249篇 |
2005年 | 177篇 |
2004年 | 198篇 |
2003年 | 157篇 |
2002年 | 147篇 |
2001年 | 99篇 |
2000年 | 89篇 |
1999年 | 81篇 |
1998年 | 91篇 |
1997年 | 79篇 |
1996年 | 107篇 |
1995年 | 75篇 |
1994年 | 95篇 |
1993年 | 69篇 |
1992年 | 61篇 |
1991年 | 35篇 |
1990年 | 37篇 |
1989年 | 29篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 30篇 |
1985年 | 33篇 |
1984年 | 29篇 |
1983年 | 12篇 |
1982年 | 41篇 |
1981年 | 18篇 |
1980年 | 22篇 |
1979年 | 29篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1976年 | 8篇 |
1973年 | 2篇 |
1969年 | 1篇 |
排序方式: 共有5716条查询结果,搜索用时 15 毫秒
61.
ρ混合、φ混合、ψ混合线性模型M估计的强相合性 总被引:5,自引:3,他引:2
研究了 ρ混合、φ混合、ψ混合样本线性模型中回归参数M估计的强相合性 ,在条件不变的情况下 ,获得与独立情形一样的M估计是强相合的充分条件 ,推广了文 [1 ]定理 2 . 相似文献
62.
Testing goodness of fit for the distribution of errors in multivariate linear models 总被引:2,自引:0,他引:2
M.D. Jimnez Gamero J. Muoz García R. Pino Mejías 《Journal of multivariate analysis》2005,95(2):301-322
In this paper, to test goodness of fit to any fixed distribution of errors in multivariate linear models, we consider a weighted integral of the squared modulus of the difference between the empirical characteristic function of the residuals and the characteristic function under the null hypothesis. We study the limiting behaviour of this test statistic under the null hypothesis and under alternatives. In the asymptotics, the rank of the design matrix is allowed to grow with the sample size. 相似文献
63.
References: 《理论物理通讯》2007,48(9):428-430
By virtue of the technique of integration within an ordered product of operators, we derive the normal ordering expansion of a one- and two-mode combination squeezing operator for two harmonic oscillators with coordinatemomentum coupling. It turns out that this squeezing operator just diagonalizes the Hamiltonian H = p21/2m1 m1ω21x21/2 p22/2m2 m2ω22x22/2 - λx2p1, so its ground state is a one- and two-mode combination squeezed state.Quantum fluctuation in the ground state is calculated. 相似文献
64.
The classes ofL
1-matrices,L
2-matrices,L
3-matrices andW-matrices are introduced to study solvability of a linear complementarity problem via solving a linear program. Three sufficient
conditions are presented to guarantee that a linear complementarity problem is solvable via a linear program. The new sufficient
conditions are weaker than the ones introduced by Mangasarian. This fact is also illustrated by an example.
Partially supported by NSFC.
This author is also with College of Business Administration of Human University as a Lotus chair professor. 相似文献
65.
A flow model in combination with a statistical-dynamical turbulence generator and a linearised Euler time-domain model for sound waves were used to simulate the effect of screen-induced turbulence on the noise level in the acoustical shadow of a screen in wind. Instead of simulating a great number of different frozen turbulence realisations, the concept of transient turbulence was successfully tested and applied. This concept is adequate to the time-domain model and reduces the computational demands. Several two-dimensional simulations allowed to isolate the individual effects of wind and screen on the propagation of 500 Hz sound waves over a 4-m high noise barrier. At a distance of 250 m from the source (240 m behind the screen) the sheltering effect of the screen and the refraction effect of the wind are in the order of 6 and 4 dB, respectively. The screen-induced turbulence leads to fluctuations in the noise level with a standard deviation of 1.2 dB and a maximum amplitude of 3 dB. However, the time averaged effect turned out to be in the order of merely 0.2 dB. The effect of the screen-induced turbulence on the average noise level behind the screen is therefore negligible. 相似文献
66.
利用集值映射不动点定理及最优化问题与变分不等式的关系给出线性G^↑ateaux可微的锥凸映射的广义有效点的一个存在性定理。 相似文献
67.
A linear inequality system with infinitely many constraints is polynomial (analytical) if its index set is a compact interval
of the real line and all its coefficients are polynomial (analytical, respectively) functions of the index on this interval.
This paper provides an example of analytical system whose solution set cannot be the solution set of any polynomial system.
Research supported by DGES of Spain and FEDER of UE, Grant BFM2002-04114-C02-01.
Research supported by CONACyT of Mexico, Grant 130036.
Research partially supported by CONACyT of Mexico, Grant 44003. 相似文献
68.
In the paper, the behaviour of interior point algorithms is analyzed by using a variable metric method approach. A class of
polynomial variable metric algorithms is given achieving O ((n/β)L) iterations for solving a canonical form linear optimization problem with respect to a wide class of Riemannian metrics,
wheren is the number of dimensions and β a fixed value. It is shown that the vector fields of several interior point algorithms
for linear optimization is the negative Riemannian gradient vector field of a linear a potential or a logarithmic barrier
function for suitable Riemannian metrics.
Research Partially supported by the Hungarian National Research Foundation, Grant Nos. OTKA-T016413 and OTKA-2116. 相似文献
69.
THE SCHWARZIAN DERIVATIVE IN SEVERAL COMPLEX VARIABLES(II) 总被引:1,自引:0,他引:1
THESCHWARZIANDERIVATIVEINSEVERALCOMPLEXVARIABLES(II)GONGSHENGYUQIHUANGZHENGXUEANManuscriptreceivedAugust30,1996.De... 相似文献
70.
具有离散参数齐次随机场的线性预测(V) 总被引:1,自引:1,他引:0
本文提出并研究下列四类线性预测问题:2(n0),6(n0),5(NO,n0)及3(N0,n0).不仅求出了它们的预测误差,而且也求出了它们的预测值.因而不仅推广了而且也改进了[2-5]中的结果.本文还给出了场{X(m,n)}的一个新形式的表示式. 相似文献