全文获取类型
收费全文 | 132234篇 |
免费 | 15640篇 |
国内免费 | 10752篇 |
专业分类
化学 | 58044篇 |
晶体学 | 887篇 |
力学 | 9452篇 |
综合类 | 2085篇 |
数学 | 51956篇 |
物理学 | 36202篇 |
出版年
2024年 | 189篇 |
2023年 | 1227篇 |
2022年 | 1955篇 |
2021年 | 3770篇 |
2020年 | 3528篇 |
2019年 | 3478篇 |
2018年 | 3139篇 |
2017年 | 3931篇 |
2016年 | 4723篇 |
2015年 | 4086篇 |
2014年 | 6058篇 |
2013年 | 9532篇 |
2012年 | 6925篇 |
2011年 | 7554篇 |
2010年 | 6678篇 |
2009年 | 8166篇 |
2008年 | 8330篇 |
2007年 | 8777篇 |
2006年 | 7424篇 |
2005年 | 6399篇 |
2004年 | 5640篇 |
2003年 | 5258篇 |
2002年 | 7074篇 |
2001年 | 4304篇 |
2000年 | 3610篇 |
1999年 | 3085篇 |
1998年 | 2784篇 |
1997年 | 2468篇 |
1996年 | 2001篇 |
1995年 | 1822篇 |
1994年 | 1601篇 |
1993年 | 1391篇 |
1992年 | 1314篇 |
1991年 | 954篇 |
1990年 | 828篇 |
1989年 | 667篇 |
1988年 | 696篇 |
1987年 | 575篇 |
1986年 | 533篇 |
1985年 | 723篇 |
1984年 | 591篇 |
1983年 | 299篇 |
1982年 | 548篇 |
1981年 | 709篇 |
1980年 | 620篇 |
1979年 | 650篇 |
1978年 | 538篇 |
1977年 | 438篇 |
1976年 | 355篇 |
1973年 | 213篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We give combinatorial proofs that certain families of differences of products of Schur functions are monomial-positive. We
show in addition that such monomial-positivity is to be expected of a large class of generating functions with combinatorial
definitions similar to Schur functions. These generating functions are defined on posets with labelled Hasse diagrams and
include for example generating functions of Stanley's (P,ω)-partitions.
T.L. was supported in part by NSF DMS-0600677. 相似文献
992.
A finite volume solver for the 2D depth‐integrated harmonic hyperbolic formulation of the mild‐slope equation for wave propagation is presented and discussed. The solver is implemented on unstructured triangular meshes and the solution methodology is based upon a Godunov‐type second‐order finite volume scheme, whereby the numerical fluxes are computed using Roe's flux function. The eigensystem of the mild‐slope equations is derived and used for the construction of Roe's matrix. A formulation that updates the unknown variables in time implicitly is presented, which produces a more accurate and reliable scheme than hitherto available. Boundary conditions for different types of boundaries are also derived. The agreement of the computed results with analytical results for a range of wave propagation/transformation problems is very good, and the model is found to be virtually paraxiality‐free. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
993.
均值-方差效用函数在证券组合投资决策中的应用 总被引:3,自引:0,他引:3
本文利用均值—方差效用函数,按期望效用最大化准则建立并分析了证券组合投资决策模型。在投资者的效用函数为指数型效用函数时,得到了两基金定理分离权重的计算公式。得出了在均值——方差效用函数条件下期望效用最大化准则与M—V期望收益最大化准则一致的结论。 相似文献
994.
Dragos Ghioca 《Journal of Number Theory》2007,125(1):85-94
We study the v-adic distance from the torsion of a Drinfeld module to an affine variety. 相似文献
995.
平衡规划问题的熵函数方法及其在混合交通流中的应用 总被引:1,自引:0,他引:1
将参变极值问题的极大熵函数方法应用到求解平衡规划问题中,通过先验分布信息和Kullback熵概念,给出了平衡规划问题基于Kullback熵表示的熵函数求解方法,并将平衡规划的极大熵函数方法应用于求解混合交通平衡分配问题. 相似文献
996.
For any Sturm-Liouville problem with a separable boundary condition and whose leading coefficient function changes sign (exactly once), we first give a geometric characterization of its eigenvalues λn using the eigenvalues of some corresponding problems with a definite leading coefficient function. Consequences of this characterization include simple proofs of the existence of the λn's, their Prüfer angle characterization, and a way for determining their indices from the zeros of their eigenfunctions. Then, interlacing relations among the λn's and the eigenvalues of the corresponding problems are obtained. Using these relations, a simple proof of asymptotic formulas for the λn's is given. 相似文献
997.
We give several new constructions for moderate rank elliptic curves over Q(T). In particular we construct infinitely many rational elliptic surfaces (not in Weierstrass form) of rank 6 over Q using polynomials of degree two in T. While our method generates linearly independent points, we are able to show the rank is exactly 6 without having to verify the points are independent. The method generalizes; however, the higher rank surfaces are not rational, and we need to check that the constructed points are linearly independent. 相似文献
998.
针对一般的非线性规划问题,利用某些Lagrange型函数给出了一类Lagrangian对偶问题的一般模型,并证明它与原问题之间存在零对偶间隙.针对具体的一类增广La- grangian对偶问题以及几类由非线性卷积函数构成的Lagrangian对偶问题,详细讨论了零对偶间隙的存在性.进一步,讨论了在最优路径存在的前提下,最优路径的收敛性质. 相似文献
999.
Wei-yi SU~ 《中国科学A辑(英文版)》2007,50(7):1005-1014
The Lipschitz class Lipαon a local field K is defined in this note,and the equivalent relationship between the Lipschitz class Lipαand the Holder type space C~α(K)is proved.Then,those important characteristics on the Euclidean space R~n and the local field K are compared,so that one may interpret the essential differences between the analyses on R~n and K.Finally,the Cantor type fractal functionθ(x)is showed in the Lipschitz class Lip(m,K),m<(ln 2/ln 3). 相似文献
1000.
A. I. Golovashkin G. N. Izmaïlov G. V. Kuleshova T. Q. Khánh A. M. Tskhovrebov L. N. Zherikhina 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,58(3):243-249
A scheme of magnetic calorimeter for registration of rare events
characterized by small energy release (cosmic rays, WIMPs, solitary X-ray
quanta) is proposed. The calorimeter is brought to operation by adiabatic
demagnetization, and its magnetic response is measured by a quantum
interferometer (SQUID, A. Barone and G. Paterno, Physics and applications of Josephson Effect). Special consideration is given to the specific
features of calorimeter operation in the ferromagnetic transition region.
The trigger registration of ultrasmall energy release by a ferromagnetic
system in the metastable state is described. 相似文献