全文获取类型
收费全文 | 3141篇 |
免费 | 206篇 |
国内免费 | 266篇 |
专业分类
化学 | 268篇 |
晶体学 | 17篇 |
力学 | 168篇 |
综合类 | 20篇 |
数学 | 1246篇 |
物理学 | 1156篇 |
综合类 | 738篇 |
出版年
2024年 | 4篇 |
2023年 | 59篇 |
2022年 | 63篇 |
2021年 | 69篇 |
2020年 | 90篇 |
2019年 | 60篇 |
2018年 | 61篇 |
2017年 | 79篇 |
2016年 | 80篇 |
2015年 | 72篇 |
2014年 | 111篇 |
2013年 | 217篇 |
2012年 | 95篇 |
2011年 | 145篇 |
2010年 | 121篇 |
2009年 | 168篇 |
2008年 | 205篇 |
2007年 | 171篇 |
2006年 | 181篇 |
2005年 | 161篇 |
2004年 | 146篇 |
2003年 | 132篇 |
2002年 | 157篇 |
2001年 | 127篇 |
2000年 | 131篇 |
1999年 | 109篇 |
1998年 | 88篇 |
1997年 | 92篇 |
1996年 | 54篇 |
1995年 | 42篇 |
1994年 | 50篇 |
1993年 | 35篇 |
1992年 | 37篇 |
1991年 | 28篇 |
1990年 | 29篇 |
1989年 | 29篇 |
1988年 | 30篇 |
1987年 | 19篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 2篇 |
排序方式: 共有3613条查询结果,搜索用时 15 毫秒
1.
2.
3.
为了研究绝缘子在不同电压下表现的积污特性,利用流体力学的相关知识和电场理论,建立了模拟风沙的多物理场仿真模型.研究结果表明,周围流动速度较小时,绝缘子两端的电压增大,积污质量发会有一定程度的增加,且积污与电场力的变化密切相关,结合静电场分析会更准确;周围流动速度较大时,即使电压增大,积污质量也不会发生太大的变化. 相似文献
4.
Nonclassical light states are important for both conceptual and practical reasons: they are basic ingredients in testing and exploring quantum foundations, and are crucial resources in quantum technologies. Various useful criteria have been developed to detect nonclassicality in the literature, and several meaningful measures of nonclassicality have been introduced and measured experimentally. In this work, by use of a non-Hermitian generalization of the Wigner-Yanase-Dyson skew information and playing with operator ordering in evaluating average photon number, we develop a novel family of criteria for detecting nonclassicality of light based on Lieb's concavity, which is a deep and powerful result concerning interaction between quantum states and observables. We elucidate the information-theoretic as well as the physical meaning of the criteria, and illustrate their effectiveness in capturing and quantifying nonclassicality of various important light states. 相似文献
5.
We give a sheaf theoretic interpretation of Potts models with external magnetic field, in terms of constructible sheaves and their Euler characteristics. We show that the polynomial countability question for the hypersurfaces defined by the vanishing of the partition function is affected by changes in the magnetic field: elementary examples suffice to see non-polynomially countable cases that become polynomially countable after a perturbation of the magnetic field. The same recursive formula for the Grothendieck classes, under edge-doubling operations, holds as in the case without magnetic field, but the closed formulae for specific examples like banana graphs differ in the presence of magnetic field. We give examples of computation of the Euler characteristic with compact support, for the set of real zeros, and find a similar exponential growth with the size of the graph. This can be viewed as a measure of topological and algorithmic complexity. We also consider the computational complexity question for evaluations of the polynomial, and show both tractable and NP-hard examples, using dynamic programming. 相似文献
6.
陶琳 《曲阜师范大学学报》2004,30(4):65-67
研究以不同初速度进入互相垂直的匀强磁场和均强电场中的带电粒子束的运动情形,并同相似的力学运动相比拟,建立了直观的力学模型。 相似文献
7.
8.
Lu Chuanrong 《数学年刊B辑(英文版)》1997,18(1):71-78
Let $\{\xi_{\bold t}, {\bold t}
\in {\bold Z}^d\}$ be a nonuniform $\varphi$-mixing strictly stationary
real random field with
$E\xi_{\bold 0}=0, E|\xi_{\bold 0}|^{2+\delta}<\infty$ for some
$0<\delta<1$. A sufficient
condition is given for the sequence of partial sum set-indexed process
$\{Z_n(A),\ A\in \Cal A\}$ to converge to Brownian motion. By a direct
calculation, the author shows
that the result holds for a more general class of set index ${\Cal A}$, where
${\Cal A}$ is assumed only to have the metric entropy exponent $r, 0相似文献
9.
10.
In this paper we continue to study the spectral norms and their completions ([4]) in the case of the algebraic closure $ \overline {\mathbb Q} $ of ? in ?. Let $ \widetilde{\overline{\mathbb{Q}}} $ be the completion of $ \overline {\mathbb Q} $ relative to the spectral norm. We prove that $ \widetilde{\overline{\mathbb{Q}}} $ can be identified with the R‐subalgebra of all symmetric functions of C(G), where C(G) denotes the ?‐Banach algebra of all continuous functions defined on the absolute Galois group G = Gal$ {\overline {\mathbb Q}} / {\mathbb Q} $. We prove that any compact, closed to conjugation subset of ? is the pseudo‐orbit of a suitable element of $ \widetilde{\overline{\mathbb{Q}}} $. We also prove that the topological closure of any algebraic number field in $ \widetilde{\overline{\mathbb{Q}}} $ is of the form $\widetilde{\mathbb{Q}[x]}$ with x in $ \widetilde{\overline{\mathbb{Q}}} $. 相似文献