全文获取类型
收费全文 | 19238篇 |
免费 | 2171篇 |
国内免费 | 1544篇 |
专业分类
化学 | 2727篇 |
晶体学 | 62篇 |
力学 | 1793篇 |
综合类 | 575篇 |
数学 | 12349篇 |
物理学 | 5447篇 |
出版年
2023年 | 146篇 |
2022年 | 248篇 |
2021年 | 331篇 |
2020年 | 388篇 |
2019年 | 385篇 |
2018年 | 449篇 |
2017年 | 518篇 |
2016年 | 605篇 |
2015年 | 414篇 |
2014年 | 768篇 |
2013年 | 1280篇 |
2012年 | 887篇 |
2011年 | 1150篇 |
2010年 | 1140篇 |
2009年 | 1359篇 |
2008年 | 1387篇 |
2007年 | 1357篇 |
2006年 | 1282篇 |
2005年 | 1025篇 |
2004年 | 912篇 |
2003年 | 841篇 |
2002年 | 813篇 |
2001年 | 651篇 |
2000年 | 618篇 |
1999年 | 568篇 |
1998年 | 456篇 |
1997年 | 431篇 |
1996年 | 344篇 |
1995年 | 310篇 |
1994年 | 231篇 |
1993年 | 209篇 |
1992年 | 205篇 |
1991年 | 137篇 |
1990年 | 137篇 |
1989年 | 111篇 |
1988年 | 93篇 |
1987年 | 84篇 |
1986年 | 55篇 |
1985年 | 77篇 |
1984年 | 68篇 |
1983年 | 40篇 |
1982年 | 74篇 |
1981年 | 47篇 |
1980年 | 45篇 |
1979年 | 68篇 |
1978年 | 43篇 |
1977年 | 43篇 |
1976年 | 24篇 |
1974年 | 25篇 |
1973年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We demonstrate that a pair of additive quintic equations in at least 34 variables has a nontrivial integral solution, subject only to an 11-adic solubility hypothesis. This is achieved by an application of the Hardy–Littlewood method, for which we require a sharp estimate for a 33.998th moment of quintic exponential sums. We are able to employ p-adic iteration in a form that allows the estimation of such a mean value over a complete unit square, thereby providing an approach that is technically simpler than those of previous workers and flexible enough to be applied to related problems. 相似文献
102.
In this paper, we establish the existence of upper and lower solutions for a periodic boundary value problems (PBVP for short) of impulsive differential equations. which guarantees the existence of at least one solution for the problem. As an application, these results are applied to PBVP of ODE and some examples are given to illustrate our results. 相似文献
103.
Héctor J. Sussmann 《Set-Valued Analysis》2002,10(2-3):233-285
It is shown that the construction of needle variations can be carried out for almost lower semicontinuous differential inclusions rather than for the case of ordinary single-valued continuously differentiable vector fields usually considered in the literature. The construction leads to needle variations whose flows are in general set-valued but still have good differentiability properties. The variations are constructed by using single-valued selections that are not necessarily continuous with respect to the state variable, but have instead a much weaker 'integral continuity' property, somewhat more general that the 'directional continuity' considered in previous work by A. Cambini and S. Querci, A. Pucci, and A. Bressan. The existence of many such selections is proved by slightly adapting an argument due to Bressan, extending it from the lower semicontinuous to the almost lower semicontinuous case, and strengthening it to yield not only directional continuity at all points but also full continuity at a specified point. 相似文献
104.
抓好数学建模竞赛 推动数学教学改革 总被引:5,自引:0,他引:5
本文通过近几年组织数学建模教学和指导学生参加竞赛的实践 ,探索抓好数学建模竞赛 ,促进数学教学改革 ,推动数学素质教育 ,提高人才培养质量的途径、措施和方法 相似文献
105.
运输网络中最小饱和流的求解 总被引:4,自引:0,他引:4
运输网络中常常由于流量的不可控易发生堵塞现象.网络发生堵塞时的饱和流值达不到最大流值.最小饱和流是运输网络,尤其是紧急疏散网络设计中很重要的一个参数.通过建立网络的割集矩阵来确定网络的堵塞截面,基于此提出了求解最小饱和流的线性规划模型及算法.举例分析表明,利用该算法计算网络最小饱和流更加简便、更加实用. 相似文献
106.
Anatoliy Malyarenko 《Journal of Theoretical Probability》2006,19(2):263-288
We prove a general functional limit theorem for multiparameter fractional Brownian motion. The functional law of the iterated
logarithm, functional Lévy’s modulus of continuity and many other results are its particular cases. Applications to approximation
theory are discussed.
相似文献
107.
Maxim Perelstein 《Pramana》2006,67(5):813-820
Little Higgs models are an interesting extension of the Standard Model at the TeV scale. They provide a simple and attractive
mechanism of electroweak symmetry breaking. We review one of the simplest models of this class, the Littlest Higgs model,
and its extension with T parity. The model with T parity satisfies precision electroweak constraints without fine-tuning, contains an attractive dark matter candidate, and
leads to interesting phenomenology at the Large Hadron Collider (LHC). 相似文献
108.
本文研究具有受迫性的广义二维KdV-Burgers方程的周期行波解,为了获得周期行波解的存在唯一性定理,使唤用特定系数法和Schauder不动点定理获得了受迫广义KdV-Burgers方程周期行波解存在唯一性的条件.并获得了周期行波解的一些先验估计式. 相似文献
109.
相位差与q变形广义相干叠加态的压缩特性 总被引:1,自引:0,他引:1
对于q变形的非简谐振子广义相干态的叠加态β〉+eiφβeiδ〉,其量子涨落的可能高阶压缩阶数可以表示为k≠2πn/δ,这里n是整数.当δ=π时,压缩阶数不能是偶数即只能是奇数,这正是q变形非简谐振子广义奇偶相干态的结果.由此表明参数相位差δ对决定q变形的非简谐振子广义相干态叠加态的高阶压缩阶数起决定性作用. 相似文献
110.
The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field. 相似文献