全文获取类型
收费全文 | 6691篇 |
免费 | 634篇 |
国内免费 | 544篇 |
专业分类
化学 | 1575篇 |
晶体学 | 43篇 |
力学 | 1285篇 |
综合类 | 138篇 |
数学 | 2830篇 |
物理学 | 1998篇 |
出版年
2024年 | 9篇 |
2023年 | 38篇 |
2022年 | 117篇 |
2021年 | 158篇 |
2020年 | 147篇 |
2019年 | 155篇 |
2018年 | 139篇 |
2017年 | 179篇 |
2016年 | 231篇 |
2015年 | 175篇 |
2014年 | 265篇 |
2013年 | 470篇 |
2012年 | 373篇 |
2011年 | 360篇 |
2010年 | 315篇 |
2009年 | 399篇 |
2008年 | 411篇 |
2007年 | 375篇 |
2006年 | 401篇 |
2005年 | 308篇 |
2004年 | 328篇 |
2003年 | 273篇 |
2002年 | 295篇 |
2001年 | 243篇 |
2000年 | 214篇 |
1999年 | 213篇 |
1998年 | 171篇 |
1997年 | 151篇 |
1996年 | 126篇 |
1995年 | 121篇 |
1994年 | 97篇 |
1993年 | 88篇 |
1992年 | 77篇 |
1991年 | 69篇 |
1990年 | 71篇 |
1989年 | 59篇 |
1988年 | 29篇 |
1987年 | 36篇 |
1986年 | 41篇 |
1985年 | 19篇 |
1984年 | 25篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 24篇 |
1980年 | 6篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1973年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有7869条查询结果,搜索用时 109 毫秒
81.
82.
An efficient algorithm for solving nonlinear programs with noisy equality constraints is introduced and analyzed. The unknown exact constraints are replaced by surrogates based on the bundle idea, a well-known strategy from nonsmooth optimization. This concept allows us to perform a fast computation of the surrogates by solving simple quadratic optimization problems, control the memory needed by the algorithm, and prove the differentiability properties of the surrogate functions. The latter aspect allows us to invoke a sequential quadratic programming method. The overall algorithm is of the quasi-Newton type. Besides convergence theorems, qualification results are given and numerical test runs are discussed. 相似文献
83.
Let G be a graph and f : V(G)→{1,3,5,…}. Then a subgraph H of G is called a (1,f)-odd subgraph if degH(x){1,3,…,f(x)} for all xV(H). If f(x)=1 for all xV(G), then a (1,f)-odd subgraph is nothing but a matching. A (1,f)-odd subgraph H of G is said to be maximum if G has no (1,f)-odd subgraph K such that |K|>|H|. We show that (1,f)-odd subgraphs have some properties similar to those of matchings, in particular, we give a formula for the order of a maximum (1,f)-odd subgraph, which is similar to that for the order of a maximum matching. 相似文献
84.
The constrained optimization problem with a quadratic cost functional and two quadratic equality constraints has been studied by Bar-on and Grasse, with positive-definite matrix in the objective. In this note, we shall relax the matrix in the objective to be positive semidefinite. A necessary and sufficient condition to characterize a local optimal solution to be global is established. Also, a perturbation scheme is proposed to solve this generalized problem. 相似文献
85.
We investigate certain classes of normal completely positive (CP) maps on the hyperfinite II1 factorA. Using the representation theory of a suitable irrational rotation algebra, we propose some computable invariants for such
CP maps.
Dedicated to Professor K B Sinha 相似文献
86.
Binglin Lu 《Journal of statistical physics》1987,49(3-4):669-684
The coagulation equation with kernelK
ij
=A+B(i+j)+C
ij and arbitrary initial conditions is studied analytically and a simple expression for the solution is found. For monodisperse initial conditions, we recover the known size distribution expressed in terms of a degeneracy factorN
k, which is determined by a recursion relation. For polydisperse initial conditions, a similar solution form is found, which includes a degeneracy factorN
kl, also determined by a recursion relation. The physical meaning ofN
kl and the recursion relation is given. A method to get explicit expressions forN
k andN
kl is illustrated. Finally, the pre-gel solution is given explicitly and a general method to get the post-gel solution is proposed. 相似文献
87.
Rescaled mean spherical approximation (RMSA) has been used to calculate the structure factor for the aqueous suspension of
polystyrene macroions with the interaction potential taken according to Derjaguin and Landau (1941) and Verwey and Overbeek
(1948) (DLVO) model. The effects of charge over the macroion and size on the surface potential and therefore, the structure
factor have been studied. The breakdown of the DLVO potential with an excess charge over the macroion (⩾800e) has been reported.
The oscillation in the first peak height of structure factor versus wave vector curve with size has been correlated with the
Debye length. 相似文献
88.
89.
S.S. Joshi 《Applied Surface Science》2006,252(24):8539-8543
In the present work, for the first time, heterojunction has been fabricated using electrochemically deposited isotype p-selenium-p-polyaniline from a single solution bath. The structural characterization of selenium and polyaniline thin film was carried out using XRD technique. Polyaniline exhibited amorphous structure while selenium offered monoclinic (β) phase. The junction was formed by electrodepositing polyaniline over selenium film and heating at 423 K. The current density versus voltage (J-V) plot showed the formation of a junction with ideality factor of 1.16. From J-V characteristics at different temperatures, static resistance (Rs), dynamic resistance (Rd), and rectification ratio of diodes were determined. Heat treatment above 448 K caused junction breakdown. 相似文献
90.
框式约束凸二次规划问题的内点算法 总被引:4,自引:0,他引:4
张艺 《高等学校计算数学学报》2002,24(2):163-168
In this paper,a primal-dual interior point algorithm for convex quadratic progromming problem with box constrains is presented.It can be started at any primal-dual interior feasible point.If the initial point is close to the central path,it becomes a central path-following alogorithm and requires a total of O(√nL)number of iterations,where L is the input length. 相似文献