全文获取类型
收费全文 | 4520篇 |
免费 | 421篇 |
国内免费 | 458篇 |
专业分类
化学 | 250篇 |
晶体学 | 14篇 |
力学 | 268篇 |
综合类 | 111篇 |
数学 | 4113篇 |
物理学 | 643篇 |
出版年
2023年 | 60篇 |
2022年 | 78篇 |
2021年 | 90篇 |
2020年 | 137篇 |
2019年 | 130篇 |
2018年 | 126篇 |
2017年 | 136篇 |
2016年 | 137篇 |
2015年 | 90篇 |
2014年 | 197篇 |
2013年 | 392篇 |
2012年 | 183篇 |
2011年 | 236篇 |
2010年 | 224篇 |
2009年 | 278篇 |
2008年 | 287篇 |
2007年 | 305篇 |
2006年 | 303篇 |
2005年 | 270篇 |
2004年 | 225篇 |
2003年 | 205篇 |
2002年 | 210篇 |
2001年 | 165篇 |
2000年 | 151篇 |
1999年 | 142篇 |
1998年 | 103篇 |
1997年 | 90篇 |
1996年 | 84篇 |
1995年 | 65篇 |
1994年 | 66篇 |
1993年 | 31篇 |
1992年 | 30篇 |
1991年 | 20篇 |
1990年 | 21篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 22篇 |
1985年 | 22篇 |
1984年 | 15篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1978年 | 4篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1957年 | 3篇 |
1936年 | 1篇 |
排序方式: 共有5399条查询结果,搜索用时 31 毫秒
1.
This paper proposes a method for solving optimisation problems involving piecewise quadratic functions. The method provides a solution in a finite number of iterations, and the computational complexity of the proposed method is locally polynomial of the problem dimension, i.e., if the initial point belongs to the sufficiently small neighbourhood of the solution set. Proposed method could be applied for solving large systems of linear inequalities. 相似文献
2.
The efficient evaluation of multivariate polynomials at many points is an important operation for polynomial system solving. Kedlaya and Umans have recently devised a theoretically efficient algorithm for this task when the coefficients are integers or when they lie in a finite field. In this paper, we assume that the set of points where we need to evaluate is fixed and “sufficiently generic”. Under these restrictions, we present a quasi-optimal algorithm for multi-point evaluation over general fields. We also present a quasi-optimal algorithm for the opposite interpolation task. 相似文献
3.
《Operations Research Letters》2021,49(4):548-552
In this paper, we employ an asymptotic assumption to show that the maximum of finitely many convex polynomials is an asymptotically well behaved function. We also give two examples to illustrate our main result. As an application, we reproduce some known results appeared recently in the literature. 相似文献
4.
谱体积方法是一种本质上解决网格依赖性的高精度CFD计算方法,本文研究了二维Euler方程的谱体积方法,提出一种基于切比雪夫多项式的单元分割方法,建立了基于WENO的变量限制器方法,并发展了结合谱体积和控制体的问题单元标记方法.采用15°超声速压缩拐角和NACA0012跨声速流动两个典型算例进行验证,结果表明,该分区方法具有更好的计算精度,标记方法可有效识别不连续区域,在较少的网格下即可获得与密网格传统有限体积法相当的计算精度. 相似文献
5.
6.
研究了广义半交换环的幂零结构,定义了一类新的环类,即幂零$\alpha$-半交换环.说明了$\alpha$-半交换环与半交换环, $\alpha$-半交换环和$\alpha$-刚性环等环密切相关,通过构造反例说明了幂零$\alpha$-半交换环未必是$\alpha$-半交换环.研究了幂零$\alpha$-半交换环的各种性质,推广和统一了与环的半交换性质有关的若干结论. 相似文献
7.
8.
Hasan Kara Muhammad Aamir Ali Hüseyin Budak 《Mathematical Methods in the Applied Sciences》2021,44(1):104-123
In this paper, we define interval‐valued left‐sided and right‐sided generalized fractional double integrals. We establish inequalities of Hermite‐Hadamard like for coordinated interval‐valued convex functions by applying our newly defined integrals. 相似文献
9.
Prof. Makoto Tadokoro Masaki Itoh Ryota Nishimura Kensuke Sekiguchi Dr. Norihisa Hoshino Dr. Hajime Kamebuchi Prof. Jun Miyazaki Dr. Fumiya Kobayashi Prof. Motohiro Mizuno Prof. Tomoyuki Akutagawa 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(47):e202201397
A new H-bonded crystal [RuIII(Him)3(Im)3] with three imidazole (Him) and three imidazolate (Im−) groups was prepared to obtain a higher-temperature proton conductor than a Nafion membrane with water driving. The crystal is constructed by complementary N−H⋅⋅⋅N H-bonds between the RuIII complexes and has a rare Icy-c* cubic network topology with a twofold interpenetration without crystal anisotropy. The crystals show a proton conductivity of 3.08×10−5 S cm−1 at 450 K and a faster conductivity than those formed by only HIms. The high proton conductivity is attributed to not only molecular rotations and hopping motions of HIm frameworks that are activated at ∼113 K, but also isotropic whole-molecule rotation of [RuIII(Him)3(Im)3] at temperatures greater than 420 K. The latter rotation was confirmed by solid-state 2H NMR spectroscopy; probable proton conduction routes were predicted and theoretically considered. 相似文献