全文获取类型
收费全文 | 10202篇 |
免费 | 1012篇 |
国内免费 | 1889篇 |
专业分类
化学 | 3816篇 |
晶体学 | 141篇 |
力学 | 2029篇 |
综合类 | 153篇 |
数学 | 4670篇 |
物理学 | 2294篇 |
出版年
2024年 | 11篇 |
2023年 | 139篇 |
2022年 | 251篇 |
2021年 | 280篇 |
2020年 | 397篇 |
2019年 | 350篇 |
2018年 | 320篇 |
2017年 | 432篇 |
2016年 | 425篇 |
2015年 | 304篇 |
2014年 | 474篇 |
2013年 | 871篇 |
2012年 | 524篇 |
2011年 | 671篇 |
2010年 | 522篇 |
2009年 | 694篇 |
2008年 | 717篇 |
2007年 | 697篇 |
2006年 | 654篇 |
2005年 | 636篇 |
2004年 | 496篇 |
2003年 | 462篇 |
2002年 | 373篇 |
2001年 | 350篇 |
2000年 | 322篇 |
1999年 | 287篇 |
1998年 | 284篇 |
1997年 | 229篇 |
1996年 | 170篇 |
1995年 | 125篇 |
1994年 | 115篇 |
1993年 | 90篇 |
1992年 | 74篇 |
1991年 | 60篇 |
1990年 | 43篇 |
1989年 | 34篇 |
1988年 | 32篇 |
1987年 | 33篇 |
1986年 | 29篇 |
1985年 | 18篇 |
1984年 | 26篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 4篇 |
1972年 | 3篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
介绍未确知数学方法,并用未确知数学方法分析处理物理实验数据,与传统的数据处理方法比较,未确知数学方法不必对数据作任何假设,因此更合理,也更符合实际。 相似文献
72.
The load-carrying capacity of circular plates made of a fiber-reinforced composite and loaded with axisymmetric transverse forces under axisymmetric boundary conditions is investigated. The plates can be freely supported or clamped along their contour. To the known yield condition used, in the plane of main bending moments, there correspond irregular hexagons, which depend on the mechanical properties of composite constituents and some characteristic geometrical parameters. It is shown that, depending on the ratio of ultimate radial and circumferential bending moments, in the plastic state, the circular plates (the central part of the clamped plates) take the form of a cone or a frustum of cone. For each of the cases, the limit load is found, which is a function of the above-mentioned mechanical parameters. The statically allowable fields of bending moments and the corresponding allowable fields of deflection rates are determined. The solutions found are exact. Special cases for the freely supported plates are analyzed, and the results obtained are presented in the form of graphs.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 177–192, March–April, 2005. 相似文献
73.
Monique Laurent 《Mathematical Programming》2007,109(2-3):239-261
We give a hierarchy of semidefinite upper bounds for the maximum size A(n,d) of a binary code of word length n and minimum distance at least d. At any fixed stage in the hierarchy, the bound can be computed (to an arbitrary precision) in time polynomial in n; this is based on a result of de Klerk et al. (Math Program, 2006) about the regular ∗-representation for matrix ∗-algebras.
The Delsarte bound for A(n,d) is the first bound in the hierarchy, and the new bound of Schrijver (IEEE Trans. Inform. Theory 51:2859–2866, 2005) is located
between the first and second bounds in the hierarchy. While computing the second bound involves a semidefinite program with
O(n
7) variables and thus seems out of reach for interesting values of n, Schrijver’s bound can be computed via a semidefinite program of size O(n
3), a result which uses the explicit block-diagonalization of the Terwilliger algebra. We propose two strengthenings of Schrijver’s
bound with the same computational complexity.
Supported by the Netherlands Organisation for Scientific Research grant NWO 639.032.203. 相似文献
74.
75.
V. P. Maslov 《Theoretical and Mathematical Physics》2007,150(1):102-122
From the standpoint of thermodynamic averaging of fission microprocesses, we investigate the origin of radioactive release
in an NPP after an accident or after resource depletion. The genesis of the NPP release is interpreted as a new thermodynamic
phenomenon, a zeroth-order phase transition. This problem setting results in a problem in probabilistic number theory. We
prove the corresponding theorem leading to quantization of the Zipf law for the frequency of a zeroth-order phase transition
with different values of the jump of the Gibbs thermodynamic potential. We introduce the notion of hole dimension.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 150, No. 1, pp. 118–142, January, 2007. 相似文献
76.
李辉 《宁波大学学报(理工版)》1995,(1)
本文对低叠合面钢筋破简支在合梁二阶段受力的斜截面抗剪性能进行了试验研究,并运用非线性有限元分析和试验实测数据,得出了一个适合于集中荷载下高低叠合面叠合梁的抗剪强度计算公式. 相似文献
77.
78.
现场抽样调查中,由于测量误差的存在,使得所测变量实测值的方差增大,通过增加每个体的测量次数可以控制测量误差,但这样每个体调查费用增大。本文对测量信度R,每个体测量次数m与相应所需的样本含量nm、调查费用Tn的关系进行了探讨,并介绍了如何根据R,及每个体测量费用占其总费用构成比C,确定最佳测量次数m值,以达到最佳控制调查费用的目的,这对我们在大型现场调查中进行经济效益分析具有重大的理论指导意义。 相似文献
79.
Youssef Saab 《Journal of Heuristics》1997,3(3):207-224
A heuristic optimization methodology, Dynamic Contraction (DC), is introduced as an approach for solving a wide variety of hard combinatorial problems. Contraction is an operation that maps an instance of a problem to a smaller instance of the same problem. DC is an iterative improvement strategy that relies on contraction as a mechanism for escaping local minima. As a byproduct of contraction, efficiency is improved due to a reduction of problem size. Effectiveness of DC is shown through simple applications to two classical combinatorial problems: The graph bisection problem and the traveling salesman problem. 相似文献
80.
Algorithms for systematical search of inverse in arithmetic operations with fuzzy numbers are discussed. The fuzzy number derived is considered either in a discrete representation of its support or described by the parameters of the corresponding membership function formula. Both algorithms are easy to be programmed for desk calculators. 相似文献