全文获取类型
收费全文 | 48863篇 |
免费 | 10893篇 |
国内免费 | 2365篇 |
专业分类
化学 | 50199篇 |
晶体学 | 495篇 |
力学 | 1113篇 |
综合类 | 110篇 |
数学 | 3450篇 |
物理学 | 6754篇 |
出版年
2024年 | 36篇 |
2023年 | 220篇 |
2022年 | 458篇 |
2021年 | 620篇 |
2020年 | 1635篇 |
2019年 | 2945篇 |
2018年 | 1345篇 |
2017年 | 998篇 |
2016年 | 3871篇 |
2015年 | 3993篇 |
2014年 | 4102篇 |
2013年 | 4975篇 |
2012年 | 4165篇 |
2011年 | 3400篇 |
2010年 | 3623篇 |
2009年 | 3510篇 |
2008年 | 3278篇 |
2007年 | 2545篇 |
2006年 | 2215篇 |
2005年 | 2223篇 |
2004年 | 1980篇 |
2003年 | 1809篇 |
2002年 | 2483篇 |
2001年 | 1735篇 |
2000年 | 1509篇 |
1999年 | 645篇 |
1998年 | 224篇 |
1997年 | 163篇 |
1996年 | 178篇 |
1995年 | 162篇 |
1994年 | 137篇 |
1993年 | 137篇 |
1992年 | 109篇 |
1991年 | 98篇 |
1990年 | 81篇 |
1989年 | 85篇 |
1988年 | 46篇 |
1987年 | 48篇 |
1986年 | 38篇 |
1985年 | 54篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 22篇 |
1981年 | 23篇 |
1980年 | 17篇 |
1977年 | 10篇 |
1959年 | 12篇 |
1958年 | 11篇 |
1957年 | 15篇 |
1956年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
62.
Quantization of Underdamped, Critically Damped, and Overdamped Electric Circuits with a Power Source
Jeong-Ryeol Choi 《International Journal of Theoretical Physics》2002,41(10):1931-1939
We have investigated the quantum mechanical effect of the underdamped, critically damped, and overdamped electric circuits with a power source. The charge of the underdamped circuit oscillates while those of the critically damped and overdamped ones don't. The wave function of the system of overdamped circuit represented parabolic cylinder function while underdamped circuit was represented by well-known Hermite polynomial. The eigenvalues of underdamped circuit is discrete while those of the critically damped and overdamped ones are given as continuously. 相似文献
63.
离子交换富集-导数火焰原子吸收法测定自来水中Cu,Fe和Zn 总被引:7,自引:0,他引:7
本文研究了用 2 0 1× 7阳离子交换树脂对自来水中的微量元素进行交换富集 ,采用微量脉冲进样 导数火焰原子吸收法测定富集后溶液中的Cu ,Fe和Zn ,该方法灵敏度分别为 0 2 9,0 5 9和 0 0 6 μg·L- 1 ,精密度分别为 4 2 8% ,1 95 %和 2 2 8% ,检测限分别为 1 2 8,5 85和 0 6 8μg·L- 1 ,回收率分别为 91 13% ,10 1 34%和99 84 % ,本方法大大减少了需样量 ,简便快速 ,灵敏度高。 相似文献
64.
Based on the Collins formula and irradiance moments definition, the propagation of the kurtosis parameter of super-Gaussian beams through a spherically aberrated lens is studied. Detailed numerical results are given. It is shown that, as compared with aberration-free super-Gaussian beams, the profile of spherically aberrated super-Gaussian beams can be leptokurtic, mesokurtic or platykurtic, depending on the aberration and propagation distance. The results for the spherically aberrated Gaussian beams can be dealt with as a special case treated in this paper. Finally, the advantage of our method is pointed out. 相似文献
65.
A (w,r) cover‐free family is a family of subsets of a finite set such that no intersection of w members of the family is covered by a union of r others. A (w,r) superimposed code is the incidence matrix of such a family. Such a family also arises in cryptography as the concept of key distribution pattern. In the present paper, we give some new results on superimposed codes. First we construct superimposed codes from super‐simple designs which give us results better than superimposed codes constructed by other known methods. Next we prove the uniqueness of the (1,2) superimposed code of size 9 × 12, the (2,2) superimposed code of size 14 × 8, and the (2,3) superimposed code of size 30 × 10. Finally, we improve numerical values of upper bounds for the asymptotic rate of some (w,r) superimposed codes. © 2004 Wiley Periodicals, Inc. 相似文献
66.
Summary Some estimators of maximum likelihood type are constructed for estimating functionals of one-dimensional Gibbs states. We also show that those estimators are strongly consistent, asymptotically normal and asymptotically efficient. 相似文献
67.
Myungjin Jeon Dongsoong Han Kyeongsu Park Gundon Choi 《Journal of Applied Mathematics and Computing》2005,18(1-2):235-246
We present an interpolating, univariate subdivision scheme which preserves the discrete curvature and tangent direction at each step of subdivision. Since the polygon have a geometric information of some original (in some sense) curve as a discrete curvature, we can expect that the limit curve has the same curvature at each vertex as the control polygon. We estimate the curvature bound of odd vertices and give an error estimate for restoring a curve from sampled vertices on curves. 相似文献
68.
69.
70.
A graph G is N2‐locally connected if for every vertex ν in G, the edges not incident with ν but having at least one end adjacent to ν in G induce a connected graph. In 1990, Ryjá?ek conjectured that every 3‐connected N2‐locally connected claw‐free graph is Hamiltonian. This conjecture is proved in this note. © 2004 Wiley Periodicals, Inc. J Graph Theory 48: 142–146, 2005 相似文献