全文获取类型
收费全文 | 6839篇 |
免费 | 945篇 |
国内免费 | 229篇 |
专业分类
化学 | 309篇 |
晶体学 | 73篇 |
力学 | 2656篇 |
综合类 | 94篇 |
数学 | 2068篇 |
物理学 | 2813篇 |
出版年
2024年 | 8篇 |
2023年 | 46篇 |
2022年 | 106篇 |
2021年 | 151篇 |
2020年 | 176篇 |
2019年 | 130篇 |
2018年 | 134篇 |
2017年 | 188篇 |
2016年 | 179篇 |
2015年 | 161篇 |
2014年 | 242篇 |
2013年 | 415篇 |
2012年 | 356篇 |
2011年 | 415篇 |
2010年 | 315篇 |
2009年 | 386篇 |
2008年 | 411篇 |
2007年 | 460篇 |
2006年 | 481篇 |
2005年 | 418篇 |
2004年 | 332篇 |
2003年 | 331篇 |
2002年 | 307篇 |
2001年 | 290篇 |
2000年 | 239篇 |
1999年 | 210篇 |
1998年 | 180篇 |
1997年 | 152篇 |
1996年 | 121篇 |
1995年 | 107篇 |
1994年 | 93篇 |
1993年 | 69篇 |
1992年 | 65篇 |
1991年 | 48篇 |
1990年 | 51篇 |
1989年 | 21篇 |
1988年 | 18篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 30篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1957年 | 4篇 |
排序方式: 共有8013条查询结果,搜索用时 859 毫秒
91.
介绍了一种检验定性指标的有效方法,可用于确定产品的合格率和评价检验人员的检验水平。用该方法分析了某厂产品的一项实际指标,合格率为91 4%,还对该厂10名检验员的检验水平作了客观的评价。 相似文献
92.
A numerical model is presented to calculate V(z) and V(x, z) curves for a line focus acoustic microscope and a specimen containing a subsurface crack. In this model, a Gaussian beam which is tracked through the lens into the coupling fluid and into the specimen, interacts with the crack. The numerical approach is based on the solution of singular integral equations by the boundary element method. The system of singular integral equations follows from the conditions at the interface of the coupling fluid and the specimen and on the faces of the crack. An electromechanical reciprocity relation is used to express the voltage at the terminals of the microscope's transducer in terms of the calculated incident and back-scattered fields. V(z) and V(x, z) curves are presented for various locations and orientations of the crack. The characteristic features of the V(z) and particularly the V(x, z) curves, as they relate to crack configuration, are discussed in some detail. 相似文献
93.
Higher-order implicit strong numerical schemes for stochastic differential equations 总被引:2,自引:0,他引:2
Higher-order implicit numerical methods which are suitable for stiff stochastic differential equations are proposed. These are based on a stochastic Taylor expansion and converge strongly to the corresponding solution of the stochastic differential equation as the time step size converges to zero. The regions of absolute stability of these implicit and related explicit methods are also examined. 相似文献
94.
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
95.
Lisa F. Shatz 《国际流体数值方法杂志》2004,44(2):147-174
The indirect boundary element method was used to study the hydrodynamics of oscillatory viscous flow over prolate and oblate spheroids, and over hemispheroidal bodies hinged to a plate. Analytic techniques, such as spheroidal coordinates, method of images, and series representations, were used to make the numerical methods more efficient. A novel method for computing the hydrodynamic torque was used, since for oscillatory flow the torque cannot be computed directly from the weightings. Instead, a Green's function for torque was derived to compute the torque indirectly from the weightings. For full spheroids, the method was checked by comparing the results to exact solutions at low and high frequencies, and to results computed using the singularity method. For hemispheroids hinged to a plate, the method for low frequencies was checked by comparing the results to previous results, and to exact solutions at high frequencies. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
96.
97.
98.
S. F. Chekmarev R. Mitri V. Bonaci-Koutecký 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):45-48
The ab initio molecular
dynamics (AIMD) [1] is combined with the heuristic, successive
confinement method of surveying a potential energy surface (PES)
[2], thereby offering a framework for the simulation study of
kinetics and equilibrium properties of metallic clusters. This
approach is applied to the study of Au4,
a cluster possessing a simple but specific PES, which consists
of very shallow and deep basins and due to this presents a
challenge to the conventional AIMD methods. Among other things,
the probabilities of the transitions between isomers have been
found, and on this basis, both the time-dependent and
equilibrium populations of the isomers have been calculated for
the conditions typical of the NeNePo experiments [3] in the
femtosecond pump-probe spectroscopy. 相似文献
99.
含k-次增生算子的Ishikawa迭代的收敛性问题 总被引:9,自引:0,他引:9
主要研究了非线性方程x Tx=f的Ishikawa迭代解.其中T为k-次增生的或增生的,并在一致光滑和任意的实Banach空间分别研究了上述方程的带误差的Ishikawa迭代解,从而推广了已知的一些结果。 相似文献
100.
本文讨论延迟微分方程单支方法的非线性稳定性 .对于 Kα,β,γ类非线性延迟微分方程 ,我们证明带有线性插值的 G( c,p,q) -代数稳定的单支方法当 c≤ 1时是 GR( p/2 ,q/2 ) -稳定及弱 GAR( p/2 ,q/2 ) -稳定的 ,当 c<1时是 GAR( p/2 ,q/2 ) -稳定的 .最后的数值试验表明了上述结论的正确性 . 相似文献