全文获取类型
收费全文 | 11526篇 |
免费 | 1378篇 |
国内免费 | 796篇 |
专业分类
化学 | 2021篇 |
晶体学 | 101篇 |
力学 | 2725篇 |
综合类 | 113篇 |
数学 | 6324篇 |
物理学 | 2416篇 |
出版年
2024年 | 19篇 |
2023年 | 121篇 |
2022年 | 176篇 |
2021年 | 216篇 |
2020年 | 364篇 |
2019年 | 313篇 |
2018年 | 290篇 |
2017年 | 325篇 |
2016年 | 430篇 |
2015年 | 376篇 |
2014年 | 551篇 |
2013年 | 1060篇 |
2012年 | 522篇 |
2011年 | 652篇 |
2010年 | 530篇 |
2009年 | 665篇 |
2008年 | 674篇 |
2007年 | 678篇 |
2006年 | 645篇 |
2005年 | 569篇 |
2004年 | 534篇 |
2003年 | 490篇 |
2002年 | 451篇 |
2001年 | 359篇 |
2000年 | 391篇 |
1999年 | 303篇 |
1998年 | 311篇 |
1997年 | 264篇 |
1996年 | 223篇 |
1995年 | 155篇 |
1994年 | 158篇 |
1993年 | 125篇 |
1992年 | 123篇 |
1991年 | 106篇 |
1990年 | 86篇 |
1989年 | 55篇 |
1988年 | 38篇 |
1987年 | 36篇 |
1986年 | 32篇 |
1985年 | 43篇 |
1984年 | 58篇 |
1983年 | 33篇 |
1982年 | 41篇 |
1981年 | 29篇 |
1980年 | 19篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1976年 | 5篇 |
1973年 | 8篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
An initial-value method is given for second-order singularly perturbed boundary-value problems with a boundary layer at one endpoint. The idea is to replace the original two-point boundary value problem by two suitable initial-value problems. The method is very easy to use and to implement. Nontrivial text problems are used to show the feasibility of the given method, its versatility, and its performance in solving linear and nonlinear singularly perturbed problems.This work was supported in part by the Consiglio Nazionale delle Ricerche, Contract No. 86.02108.01, and in part by the Ministero della Pubblica Istruzione. 相似文献
132.
133.
Minoru Murata 《Journal of Functional Analysis》2002,194(1):53-141
We consider positive solutions of elliptic partial differential equations on non-compact domains of Riemannian manifolds. We explicitly determine Martin boundaries and Martin kernels for a class of elliptic equations in skew product form by exploiting and developing perturbation theory for elliptic equations and short/long-time estimates for fundamental solutions of parabolic equations. 相似文献
134.
泊松类型方程边界元解法 总被引:2,自引:0,他引:2
本文采用高阶拉普拉斯算子基本解将泊松类型方程的区域积分全部变换成边界积分,使计算问题的维数减少一维.通过斯托克斯方程的算例,表明本文所用的方法是有效的方法。 相似文献
135.
气体放电击穿过程的物理和数值研究 总被引:1,自引:0,他引:1
胡希伟 《核聚变与等离子体物理》1994,14(1):44-50
本文对低气压(10^-2Pa)热阴极气体放电的击穿过程给出了物理描述和相应的双流体数学型,并发展了一种选择和调整未知初始条件的有效算法,可以通过伴随试射法得到对初始条件十分敏感的非线性两点边值常微分方程组的数值解,从而给出这类气体放电中击穿过程的定量描述。 相似文献
136.
用三维样边界元法分析水闸闸室结构。底板,闸墩和载水墙等为其子结构,交通桥,工作桥和胸墙等处理为内部支撑。地基和边载可以是任意的,只要能给定地表位移面力关系。在各种工况下,不论是设置平板门还是弧形门,是平底板是反拱底板,即使在稀疏剖分下也能给出高精度的位移场,应力场和地基反力场。 相似文献
137.
This paper develops a mathematical model of the ring-spinning process that takes into account its non-stationary nature. A complex system of differential equations is obtained, which from a mathematical point of view constitutes a ‘free-boundary’ problem. Its solution involves definition of suitable boundary conditions related to the mechanical characteristics of the process and of the spinning machine itself. The boundary conditions which determine the solution are pointed out. A numerical solution of the system of differential equations can be obtained by the Finite-Segments method, as shown in an example. 相似文献
138.
T. Hayashita T. Kurosawa T. Miyata K. Tanaka M. Igawa 《Colloid and polymer science》1994,272(12):1611-1619
The cationic azo-surfactants possessing different spacers and tail alkyl chain lengths have been synthesized by azocoupling ofp-alkylaniline orop-ethoxyaniline with phenol, followed by alkylation and quaternalization with dibromoalkane and trimethylamine, respectively. These surfactants showed a good solubility in water. A reversibletrans-cis isomerization of the azosurfactants by photoirradiation was assessed by UV-Vis absorption spectra. Due to a difference in HLB between thetrans- andcis-surfactants, the observed critical micelle concentration (CMC) values and the electric conductivity of the surfactant solution at above the CMC were significantly affected by the photoinducedtrans-cis isomerization. The azo-surfactants bearing moderate alkyl chain lengths such as surfactants 6 (R2=C2H4, R3=C4H9) and 9 (R2=C4H8, R3=C2H5) were found to be effective to achieve large CMC changes (3.6 mmol/L for 6 and 5.9 mmol/L for 9) by UV-light irradiation. The replacement of the tail chain species also affected the photoresponsive function. The surfactant 12, possessingp-ethoxy group as the tail chain, was found to form a stable micelle aggregation as compared with the structurally related surfactant 10 having ethyl unit as its tail group, but it exhibited a large CMC change (5.3 mmol/L) by UV-light irradiation. 相似文献
139.
王同科 《高等学校计算数学学报(英文版)》2002,11(2):213-225
1 IntroductionFinitevolumeelementmethodorFVEMusesavolumeintegralformulationofthedif ferentialequationwithafinitepartitioningsetofvolumetodiscretizetheequation ,thenre strictstheadmissiblefunctionstoalinearfiniteelementspacetodiscretizethesolution ([1 -4 ] ) .… 相似文献
140.
We use boundary value methods to compute consistent initial values for fully implicit nonlinear differential-algebraic equations.
The obtained algorithm uses variable order formulae and a deferred correction technique to evaluate the error. A rigorous
theory is stated for nonlinear index 1, 2 and 3 DAEs of Hessenberg form. Numerical tests on classical index 1, 2 and 3 DAE
problems are reported.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献