全文获取类型
收费全文 | 5152篇 |
免费 | 367篇 |
国内免费 | 1447篇 |
专业分类
化学 | 5023篇 |
晶体学 | 137篇 |
力学 | 347篇 |
综合类 | 59篇 |
数学 | 666篇 |
物理学 | 734篇 |
出版年
2024年 | 2篇 |
2023年 | 35篇 |
2022年 | 63篇 |
2021年 | 116篇 |
2020年 | 114篇 |
2019年 | 113篇 |
2018年 | 111篇 |
2017年 | 148篇 |
2016年 | 176篇 |
2015年 | 166篇 |
2014年 | 210篇 |
2013年 | 445篇 |
2012年 | 288篇 |
2011年 | 258篇 |
2010年 | 242篇 |
2009年 | 273篇 |
2008年 | 332篇 |
2007年 | 381篇 |
2006年 | 382篇 |
2005年 | 341篇 |
2004年 | 310篇 |
2003年 | 290篇 |
2002年 | 269篇 |
2001年 | 186篇 |
2000年 | 205篇 |
1999年 | 217篇 |
1998年 | 161篇 |
1997年 | 159篇 |
1996年 | 128篇 |
1995年 | 120篇 |
1994年 | 120篇 |
1993年 | 76篇 |
1992年 | 103篇 |
1991年 | 67篇 |
1990年 | 62篇 |
1989年 | 69篇 |
1988年 | 53篇 |
1987年 | 36篇 |
1986年 | 29篇 |
1985年 | 34篇 |
1984年 | 21篇 |
1983年 | 25篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有6966条查询结果,搜索用时 31 毫秒
21.
Standard ODE methods such as linear multistep methods encounter difficulties when applied to differential-algebraic equations (DAEs) of index greater than 1. In particular, previous results for index 2 DAEs have practically ruled out the use of all explicit methods and of implicit multistep methods other than backward difference formulas (BDFs) because of stability considerations. In this paper we embed known results for semi-explicit index 1 and 2 DAEs in a more comprehensive theory based on compound multistep and one-leg discretizations. This explains and characterizes the necessary requirements that a method must fulfill in order to be applicable to semi-explicit DAEs. Thus we conclude that the most useful discretizations are those that avoid discretization of the constraint. A freer use of e.g. explicit methods for the non-stiff differential part of the DAE is then possible.Dedicated to Germund Dahlquist on the occasion of his 70th birthdayThis author thanks the Centro de Estadística y Software Matemático de la Universidad Simón Bolivar (CESMa) for permitting her free use of its research facilities.Partial support by the Swedish Research Council for Engineering Sciences TFR under contract no. 222/91-405. 相似文献
22.
B. Satco 《Journal of Mathematical Analysis and Applications》2007,332(2):919-933
Existence theorems and some properties of solutions set of three boundary value second order differential equations and inclusions in Banach spaces are obtained under Henstock, respectively Henstock-Kurzweil-Pettis integrability assumptions. Our results extend those obtained by Azzam, Castaing and Thibault in the Bochner integrability setting and in the Pettis integrability one. The continuity of the (unique) solution with respect to a parameter in the single-valued case is also studied. 相似文献
23.
In this paper, the authors study the inclusion relations between Dirichlet type spaces DT and α-Bloch spacesβα by means of higher radial derivative. The strictness and the best possibility of the inclusion relations are shown with constructive methods.Furthermore, they sharpen one of the results when T = n, which proves that a conjecture in [7] is true. 相似文献
24.
Yiran He 《Journal of Global Optimization》2007,39(3):419-426
The existence of global error bound for convex inclusion problems is discussed in this paper, including pointwise global error
bound and uniform global error bound. The existence of uniform global error bound has been carefully studied in Burke and
Tseng (SIAM J. Optim. 6(2), 265–282, 1996) which unifies and extends many existing results. Our results on the uniform global
error bound (see Theorem 3.2) generalize Theorem 9 in Burke and Tseng (1996) by weakening the constraint qualification and
by widening the varying range of the parameter. As an application, the existence of global error bound for convex multifunctions
is also discussed. 相似文献
25.
聚醚醚酮链结构与反应的模型化合物的量子化学研究 总被引:1,自引:1,他引:0
利用AM1方法对聚醚醚酮模型化合物全优化,结果为:芳环平均相互扭转角为33.0度,桥键角117.0-118.0度,其分子结构拓扑图形表明:所有苯环(核)为平面构型,但其内角扭曲;其氢原子对苯环构型无实质性贡献,在更长链的计算中,冻结苯核与氢原子也得出满意结果,根据Mulliken键序与电荷讨论了醚交换与磺化反应。 相似文献
26.
FIXEDPOINTSANDCOUPLEDFIXEDPOINTSFORINCREASINGOPERATORSWITHAPPLICMIONSTODIFFERENTIALINCLUSIONSINBANACHSPACESZHANGSHISHENGANDHU... 相似文献
27.
28.
We propose general variational inclusion problems which are slightly different from corresponding problems considered in several recent papers in the literature and show that they are advantageous. Sufficient conditions for the solution existence are established. As applications we derive consequences for several special cases of variational inclusion problems, quasioptimization problems, equilibrium problems and implicit variational inequalities and show that they improve the results of some recent existing papers. 相似文献
29.
蒋忠樟 《数学的实践与认识》2007,37(15):174-179
实对称正定矩阵的复合矩阵正定性的研究已有结论,但对于一般意义下的正定矩阵的复合矩阵是否仍然是正定的研究需要利用一般的正定矩阵的标准形的复合矩阵进行讨论,给出了一般公式及具体算法,为讨论其复合矩阵的正定性提供了基础条件. 相似文献
30.
Lai-Jiu Lin 《Journal of Global Optimization》2007,38(1):21-39
In this paper, we study an existence theorem of systems of generalized quasivariational inclusions problem. By this result,
we establish the existence theorems of solutions of systems of generalized equations, systems of generalized vector quasiequilibrium
problem, collective variational fixed point, systems of generalized quasiloose saddle point, systems of minimax theorem, mathematical
program with systems of variational inclusions constraints, mathematical program with systems of equilibrium constraints and
systems of bilevel problem and semi-infinite problem with systems of equilibrium problem constraints.
This research was supported by the National Science Council of the Republic of China. 相似文献