全文获取类型
收费全文 | 11901篇 |
免费 | 1262篇 |
国内免费 | 1403篇 |
专业分类
化学 | 1109篇 |
晶体学 | 18篇 |
力学 | 760篇 |
综合类 | 317篇 |
数学 | 10186篇 |
物理学 | 2176篇 |
出版年
2024年 | 11篇 |
2023年 | 140篇 |
2022年 | 146篇 |
2021年 | 213篇 |
2020年 | 283篇 |
2019年 | 304篇 |
2018年 | 284篇 |
2017年 | 344篇 |
2016年 | 375篇 |
2015年 | 292篇 |
2014年 | 540篇 |
2013年 | 828篇 |
2012年 | 500篇 |
2011年 | 691篇 |
2010年 | 637篇 |
2009年 | 815篇 |
2008年 | 893篇 |
2007年 | 957篇 |
2006年 | 779篇 |
2005年 | 736篇 |
2004年 | 549篇 |
2003年 | 602篇 |
2002年 | 520篇 |
2001年 | 410篇 |
2000年 | 462篇 |
1999年 | 415篇 |
1998年 | 379篇 |
1997年 | 316篇 |
1996年 | 232篇 |
1995年 | 133篇 |
1994年 | 139篇 |
1993年 | 93篇 |
1992年 | 64篇 |
1991年 | 60篇 |
1990年 | 45篇 |
1989年 | 35篇 |
1988年 | 41篇 |
1987年 | 26篇 |
1986年 | 23篇 |
1985年 | 40篇 |
1984年 | 39篇 |
1983年 | 14篇 |
1982年 | 33篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 21篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 9篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
1.
高端芯片制造所需要的极紫外光刻技术位于我国当前面临35项"卡脖子"关键核心技术之首.高转换效率的极紫外光源是极紫外光刻系统的重要组成部分.本文通过采用双激光脉冲打靶技术实现较强的6.7 nm极紫外光输出.首先,理论计算Gd18+—Gd27+离子最外层4d壳层的4p-4d和4d-4f能级之间跃迁、以及Gd14+—Gd17+离子最外层4f壳层的4d-4f能级之间跃迁对波长为6.7 nm附近极紫外光的贡献.其后开展实验研究,结果表明,随着双脉冲之间延时的逐渐增加,波长为6.7 nm附近的极紫外光辐射强度呈现先减弱、后增加、之后再减弱的变化趋势,在双脉冲延时为100 ns处产生的极紫外光辐射最强.并且,在延时为100 ns处产生的光谱效率最高,相比于单脉冲激光产生的光谱效率提升了33%.此外,发现双激光脉冲打靶技术可以有效地减弱等离子体的自吸收效应,获得的6.7 nm附近极紫外光谱宽度均小于单激光脉冲打靶的情形,且在脉冲延时为30 ns时刻所产生的光谱宽度最窄,约为单独主脉冲产生极紫外光谱宽度的1/3.同时... 相似文献
2.
探讨了经济增长及金融发展与城乡收入差距之间互动影响,刻画了三者间的逻辑关系,并基于广西1990-2017年的统计数据,运用状态空间模型及卡尔曼滤波算法对三者间动态关系进行了实证分析.结果显示:经济增长对城乡收入差距呈现倒U型曲线形态,而金融发展则显示出具有不断缩小城乡收入差距的趋势. 相似文献
3.
4.
5.
6.
《Mathematische Nachrichten》2018,291(8-9):1177-1190
We introduce homogeneous Besov and Triebel–Lizorkin spaces with variable indexes. We show that their study reduces to the study of inhomogeneous variable exponent spaces and homogeneous constant exponent spaces. Corollaries include trace space characterizations and Sobolev embeddings. 相似文献
7.
In this paper we study the domain of the generator of stable processes, stable-like processes and more general pseudo- and integro-differential operators which naturally arise both in analysis and as infinitesimal generators of Lévy- and Lévy-type (Feller) processes. In particular we obtain conditions on the symbol of the operator ensuring that certain (variable order) Hölder and Hölder–Zygmund spaces are in the domain. We use tools from probability theory to investigate the small-time asymptotics of the generalized moments of a Lévy or Lévy-type process , for functions f which are not necessarily bounded or differentiable. The pointwise limit exists for fixed if f satisfies a Hölder condition at x. Moreover, we give sufficient conditions which ensure that the limit exists uniformly in the space of continuous functions vanishing at infinity. As an application we prove that the domain of the generator of contains certain Hölder spaces of variable order. Our results apply, in particular, to stable-like processes, relativistic stable-like processes, solutions of Lévy-driven SDEs and Lévy processes. 相似文献
8.
For a general dyadic grid, we give a Calderón–Zygmund type decomposition, which is the principle fact about the multilinear maximal function on the upper half‐spaces. Using the decomposition, we study the boundedness of . We obtain a natural extension to the multilinear setting of Muckenhoupt's weak‐type characterization. We also partially obtain characterizations of Muckenhoupt's strong‐type inequalities with one weight. Assuming the reverse Hölder's condition, we get a multilinear analogue of Sawyer's two weight theorem. Moreover, we also get Hytönen–Pérez type weighted estimates. 相似文献
9.
Pham Duy Khanh Tran Hong Mo Trinh T. T. Tran 《Numerical Functional Analysis & Optimization》2019,40(8):924-943
Necessary and sufficient conditions for qualitative properties of infinite dimensional linear programing problems such as solvability, duality, and complementary slackness conditions are studied in this article. As illustrations for the results, we investigate the parametric version of Gale’s example. 相似文献
10.
Rishikesh Yadav Ramakanta Meher Vishnu Narayan Mishra 《Mathematical Methods in the Applied Sciences》2019,42(18):7172-7191
In this paper, we study the approximation properties of bivariate summation‐integral–type operators with two parameters . The present work deals within the polynomial weight space. The rate of convergence is obtained while the function belonging to the set of all continuous and bounded function defined on ([0],∞)(×[0],∞) and function belonging to the polynomial weight space with two parameters, also convergence properties, are studied. To know the asymptotic behavior of the proposed bivariate operators, we prove the Voronovskaya type theorem and show the graphical representation for the convergence of the bivariate operators, which is illustrated by graphics using Mathematica. Also with the help of Mathematica, we discuss the comparison by means of the convergence of the proposed bivariate summation‐integral–type operators and Szász‐Mirakjan‐Kantorovich operators for function of two variables with two parameters to the function. In the same direction, we compute the absolute numerical error for the bivariate operators by using Mathematica and is illustrated by tables and also the comparison takes place of the proposed bivariate operators with the bivariate Szász‐Mirakjan operators in the sense of absolute error, which is represented by table. At last, we study the simultaneous approximation for the first‐order partial derivative of the function. 相似文献