全文获取类型
收费全文 | 5943篇 |
免费 | 588篇 |
国内免费 | 538篇 |
专业分类
化学 | 436篇 |
晶体学 | 7篇 |
力学 | 417篇 |
综合类 | 107篇 |
数学 | 4345篇 |
物理学 | 1757篇 |
出版年
2023年 | 47篇 |
2022年 | 58篇 |
2021年 | 76篇 |
2020年 | 115篇 |
2019年 | 121篇 |
2018年 | 107篇 |
2017年 | 139篇 |
2016年 | 165篇 |
2015年 | 133篇 |
2014年 | 222篇 |
2013年 | 479篇 |
2012年 | 285篇 |
2011年 | 340篇 |
2010年 | 287篇 |
2009年 | 386篇 |
2008年 | 414篇 |
2007年 | 396篇 |
2006年 | 406篇 |
2005年 | 311篇 |
2004年 | 278篇 |
2003年 | 270篇 |
2002年 | 254篇 |
2001年 | 230篇 |
2000年 | 206篇 |
1999年 | 210篇 |
1998年 | 174篇 |
1997年 | 117篇 |
1996年 | 132篇 |
1995年 | 79篇 |
1994年 | 78篇 |
1993年 | 70篇 |
1992年 | 46篇 |
1991年 | 41篇 |
1990年 | 46篇 |
1989年 | 26篇 |
1988年 | 45篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 36篇 |
1984年 | 37篇 |
1983年 | 16篇 |
1982年 | 28篇 |
1981年 | 17篇 |
1980年 | 17篇 |
1979年 | 23篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1970年 | 3篇 |
排序方式: 共有7069条查询结果,搜索用时 29 毫秒
101.
This article concerns the existence of global smooth solution for scalar conservation laws with degenerate viscosity in 2-dimensional space. The analysis is based on successive approximation and maximum principle. 相似文献
102.
Numerous versions of the Lanczos τ-methods have been extensively used to produce polynomial approximations for functions verifying
a linear differential equation with polynomial coefficients. In the case of an initial-value problem, an adapted τ-method
based on Chebyshev series and the use of symbolic computation lead to a rational approximation of the solution on a region
of the complex plane. Numerical examples show that the simplicity of the method does not prevent a high accuracy of results.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
103.
A new flow electrical conductance instrument was constructed and tested on dilute NaCl solutions up to 458 K, and on more
concentrated solutions (maximum 0.436 mol⋅kg−1) at 373 K. The results of the new instrument agreed with those of previous authors within the estimated experimental errors.
The model of Bernard et al. (J. Phys. Chem. 96, 3833–3840 (1992), MSA) was found to represent the high-temperature results without introducing an ion-pairing equilibrium constant. The Fuoss–Hsia
conductance equation as given by Fernandez-Prini was found to represent the dilute concentrations with Λ° (NaCl) as the only adjustable parameter. It was found that Λ° (NaCl) could be expressed as a function of solvent viscosity and density by using three parameters found by regression of
literature results between 278.15 and 523 K. This equation along with the FHFP theory permits the equivalent conductivity
of dilute sodium chloride solutions to be calculated within the accuracy of the existing experimental measurements. 相似文献
104.
THE STEP-TRANSITION OPERATORS FOR MULTI-STEP METHODS OF ODE'S 总被引:1,自引:0,他引:1
Feng K. 《计算数学(英文版)》1998,(3)
1.'IntroductionThedisad~ageofsymplecticmethodsinusingtheinformationfrompasttimestepsleadstotheirneedingmorefunctionevaluationthannonsymplecticmethods.Thisdisadvantagecanbeovercomeifonecouldconstructsymplecticmulti-stepmethods.But'theaestProblemshouldbesolvedistogiveoutthedefinitionofsymplecticmultistepmethod.Ulltilnow,apopularideaisthatanm-stepmethodonMmaybewrittenasaone-stepmethodonMa.Inpaper12,71,theauthorshaveinvestigatedthecircumstanceunderWhichadifferenceschemecanpreservetheproductsympl… 相似文献
105.
Nicholas J. Curro Charles P. Slichter 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1998,130(2):186-194
Measurement ofT2G, the Gaussian component of the spin-echo envelope of planar Cu nuclei in high-temperature superconductors, gives important information about the real part of the Cu electron spin susceptibility. In the traditional picture of the planar Cu echo decay, the internuclear coupling is assumed to remain static with respect to spin–lattice relaxation and mutual exchange fluctuations. In some circumstances, however, this assumption breaks down. We calculate the internuclear corrections arising from spin–lattice relaxation to the conventional theory ofT2Gand show thatT2Gcan be easily corrected for these effects. We argue that mutual exchanges due to the perpendicular indirect couplings are suppressed in these materials. For YBa2Cu4O8, we find a correction on the order of 10% inT2Gand using the corrected values we find that the isotope ratio63T2G/65T2Gagrees with theory. 相似文献
106.
Tony Shardlow 《BIT Numerical Mathematics》2006,46(1):111-125
We describe a backward error analysis for stochastic differential equations with respect to weak convergence. Modified equations are provided for forward and backward Euler approximations to Itô SDEs with additive noise, and extensions to other types of equation and approximation are discussed. 相似文献
107.
108.
N. B. Brusnikina A. V. Lotov 《Computational Mathematics and Mathematical Physics》2007,47(11):1779-1787
A method is proposed for approximating the reachable set of a dynamic system with a state space dimension no higher than six-eight considered on a finite time interval. The system is governed by linear differential equations with piecewise constant coefficients and impulse actions specified at prescribed times. The method is based on guaranteed-accuracy polyhedral approximations of reachable sets at researcher-specified times. Every approximation is constructed using the preceding one. A procedure is described for choosing parameters of the method that ensure the required accuracy with close-to-minimal time costs. 相似文献
109.
110.
为了精确计算束流在离子光学系统中的传输,用Visual FORTRAN 6.5语言编写了一个计算程序,长约13000行. 此程序可以计算由三圆筒单透镜、三膜片单透镜、双元筒透镜、均匀场静电加速管、磁四极透镜、六极磁铁、静电四极透镜、偏转磁铁、螺线管透镜、ExB~正交电磁场分析器、静电偏转器、漂浮管、QWR(Quarter Wave Resonators)和SLR(Split Loop Resonators)射频加速元件等元件任意组成的离子光学系统. 粒子轨迹的计算可精确到三级近似. 粒子的分布类型也可以有多种选择. 程序具有最优化计算功能,即可以自动调整元件的参数,以实现所需要的光学条件. 各元件之后的横向和纵向相图以及系统的束流包络线以图形方式显示在屏幕上. 相似文献