全文获取类型
收费全文 | 3586篇 |
免费 | 150篇 |
国内免费 | 180篇 |
专业分类
化学 | 333篇 |
晶体学 | 4篇 |
力学 | 420篇 |
综合类 | 11篇 |
数学 | 1966篇 |
物理学 | 1182篇 |
出版年
2024年 | 5篇 |
2023年 | 53篇 |
2022年 | 53篇 |
2021年 | 41篇 |
2020年 | 77篇 |
2019年 | 78篇 |
2018年 | 74篇 |
2017年 | 96篇 |
2016年 | 89篇 |
2015年 | 101篇 |
2014年 | 228篇 |
2013年 | 361篇 |
2012年 | 184篇 |
2011年 | 248篇 |
2010年 | 261篇 |
2009年 | 311篇 |
2008年 | 292篇 |
2007年 | 287篇 |
2006年 | 175篇 |
2005年 | 116篇 |
2004年 | 121篇 |
2003年 | 77篇 |
2002年 | 86篇 |
2001年 | 77篇 |
2000年 | 60篇 |
1999年 | 48篇 |
1998年 | 50篇 |
1997年 | 38篇 |
1996年 | 28篇 |
1995年 | 33篇 |
1994年 | 15篇 |
1993年 | 18篇 |
1992年 | 24篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有3916条查询结果,搜索用时 14 毫秒
991.
Sigeo Aki 《Annals of the Institute of Statistical Mathematics》1985,37(1):205-224
Summary This paper considers discrete distributions of orderk based on a binary sequence which is defined as an extension of independent trials with a constant success probability and
is more practical than the independent trials. Some results on calculation of probabilities and characteristics of the distributions
are obtained as well as their formal expressions. Examples and an application are also given.
The Institute of Statistical Mathematics 相似文献
992.
993.
该文利用拓扑度方法研究了一类时滞依赖状态的广义Duffing型泛函微分方程x'(t)$ 该文利用拓扑度方法研究了一类时滞依赖状态的广义Duffing型泛函微分方程x'(t)$ 该文利用拓扑度方法研究了一类时滞依赖状态的广义Duffing型泛函微分方程x'(t) g(x(t-τ(t,x(t))))=f(t)周期解的存在性,得到了方程周期解存在的充分条件和必要条件.研究了当滞量为常值时,方程周期解的存在唯一性.并且给出了所研究问题的一个应用实例. 相似文献
994.
We consider the Hermite trigonometric interpolation problem of order 1 for equidistant nodes, i.e., the problem of finding a trigonometric polynomial t that interpolates the values of a function and of its derivative at equidistant points. We give a formula for the Fourier coefficients of t in terms of those of the two classical trigonometric polynomials interpolating the values and those of the derivative separately. This formula yields the coefficients with a single FFT. It also gives an aliasing formula for the error in the coefficients which, on its turn, yields error bounds and convergence results for differentiable as well as analytic functions. We then consider the Lagrangian formula and eliminate the unstable factor by switching to the barycentric formula. We also give simplified formulae for even and odd functions, as well as consequent formulae for Hermite interpolation between Chebyshev points. 相似文献
995.
We use Brouwer degree to prove existence and multiplicity results for the periodic solutions of some nonlinear second order difference equations involving discrete -Laplacian. We obtain in particular upper and lower solutions theorems, Ambrosetti–Prodi type multiplicity results, sharp existence conditions for nonlinearities which are bounded from below or from above and necessary and sufficient conditions for the existence of positive periodic solutions when the nonlinearity is singular at 0. 相似文献
996.
It is first observed that a uniformly bounded cosine operator function C() and the associated sine function S() are totally non-stable. Then, using a zero-one law for the Abel limit of a closed linear operator, we prove some results concerning strong mean stability and uniform mean stability of C(). Among them are: (1) C() is strongly (C,1)-mean stable (or (C,2)-mean stable, or Abel-mean stable) if and only if 0ρ(A)σc(A); (2) C() is uniformly (C,2)-mean stable if and only if S() is uniformly (C,1)-mean stable, if and only if , if and only if , if and only if C() is uniformly Abel-mean stable, if and only if S() is uniformly Abel-mean stable, if and only if 0ρ(A). 相似文献
997.
Carl Heinrich Rohwer 《Numerical Algorithms》2007,45(1-4):239-251
Intuition suggests that the variance of additive noise contaminating a signal can be estimated by investigation of the highest
resolution level in a local Nonlinear Multiresolution Analysis. In the case of the Discrete Pulse Transforms with LULU-operators well known elegant identities between B-splines lead to some surprisingly simple and useful results. 相似文献
998.
Philippe Artzner Freddy Delbaen Jean-Marc Eber David Heath Hyejin Ku 《Annals of Operations Research》2007,152(1):5-22
Starting with a time-0 coherent risk measure defined for “value processes”, we also define risk measurement processes. Two
other constructions of measurement processes are given in terms of sets of test probabilities. These latter constructions
are identical and are related to the former construction when the sets fulfill a stability condition also met in multiperiod
treatment of ambiguity as in decision-making. We finally deduce risk measurements for the final value of locked-in positions
and repeat a warning concerning Tail-Value-at-Risk. 相似文献
999.
The classical discrete location problem is extended here, where the candidate facilities are subject to failure. The unreliable location problem is defined by introducing the probability that a facility may become inactive. The formulation and the solution procedure have been motivated by an application to model and solve a large size problem for locating base stations in a cellular communication network. We formulate the unreliable discrete location problems as 0–1 integer programming models, and implement an enhanced dual-based solution method to determine locations of these facilities to minimize the sum of fixed cost and expected operating (transportation) cost. Computational tests of some well-known problems have shown that the heuristic is efficient and effective for solving these unreliable location problems. 相似文献
1000.
Herminia I. Calvete Carmen Galé María-José Oliveros Belén Sánchez-Valverde 《European Journal of Operational Research》2007
The classical vehicle routing problem involves designing a set of routes for a fleet of vehicles based at one central depot that is required to serve a number of geographically dispersed customers, while minimizing the total travel distance or the total distribution cost. Each route originates and terminates at the central depot and customers demands are known. In many practical distribution problems, besides a hard time window associated with each customer, defining a time interval in which the customer should be served, managers establish multiple objectives to be considered, like avoiding underutilization of labor and vehicle capacity, while meeting the preferences of customers regarding the time of the day in which they would like to be served (soft time windows). This work investigates the use of goal programming to model these problems. To solve the model, an enumeration-followed-by-optimization approach is proposed which first computes feasible routes and then selects the set of best ones. Computational results show that this approach is adequate for medium-sized delivery problems. 相似文献