全文获取类型
收费全文 | 111854篇 |
免费 | 8508篇 |
国内免费 | 9913篇 |
专业分类
化学 | 45146篇 |
晶体学 | 650篇 |
力学 | 9959篇 |
综合类 | 1701篇 |
数学 | 33999篇 |
物理学 | 38820篇 |
出版年
2024年 | 167篇 |
2023年 | 1008篇 |
2022年 | 2324篇 |
2021年 | 2393篇 |
2020年 | 2444篇 |
2019年 | 2602篇 |
2018年 | 2247篇 |
2017年 | 2675篇 |
2016年 | 3033篇 |
2015年 | 2632篇 |
2014年 | 3901篇 |
2013年 | 7209篇 |
2012年 | 4518篇 |
2011年 | 5080篇 |
2010年 | 4232篇 |
2009年 | 6135篇 |
2008年 | 6761篇 |
2007年 | 7293篇 |
2006年 | 6519篇 |
2005年 | 5518篇 |
2004年 | 4975篇 |
2003年 | 5112篇 |
2002年 | 5194篇 |
2001年 | 4069篇 |
2000年 | 3939篇 |
1999年 | 3465篇 |
1998年 | 3303篇 |
1997年 | 2508篇 |
1996年 | 2255篇 |
1995年 | 1975篇 |
1994年 | 1915篇 |
1993年 | 1544篇 |
1992年 | 1549篇 |
1991年 | 1176篇 |
1990年 | 1016篇 |
1989年 | 859篇 |
1988年 | 773篇 |
1987年 | 658篇 |
1986年 | 566篇 |
1985年 | 624篇 |
1984年 | 601篇 |
1983年 | 313篇 |
1982年 | 481篇 |
1981年 | 538篇 |
1980年 | 384篇 |
1979年 | 383篇 |
1978年 | 312篇 |
1977年 | 300篇 |
1976年 | 224篇 |
1973年 | 159篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Bobby Wilson 《偏微分方程通讯》2015,40(8):1521-1542
This article explores the questions of long time orbital stability in high order Sobolev norms of plane wave solutions to the NLSE in the defocusing case. 相似文献
42.
Mourad Kainane Mezadek Mohamed Kainane Mezadek Michael Reissig 《Mathematical Methods in the Applied Sciences》2020,43(6):3117-3147
In this paper, we study the global (in time) existence of small data solutions to the Cauchy problem for the semilinear wave equation with friction, viscoelastic damping, and a power nonlinearity. We are interested in the connection between regularity assumptions for the data and the admissible range of exponents p in the power nonlinearity. 相似文献
43.
Recent Progress in the $L_p$ Theory for Elliptic and Parabolic Equations with Discontinuous Coefficients 下载免费PDF全文
Hongjie Dong 《分析论及其应用》2020,36(2):161-199
In this paper, we review some results over the last 10-15 years on elliptic and parabolic equations with discontinuous coefficients. We begin with an approach given by N. V. Krylov to parabolic equations in the whole space with $\rm{VMO}_x$ coefficients. We then discuss some subsequent development including elliptic and parabolic equations with coefficients which are allowed to be merely measurable in one or two space directions, weighted $L_p$estimates with Muckenhoupt ($A_p$) weights, non-local elliptic and parabolic equations, as well as fully nonlinear elliptic and parabolic equations. 相似文献
44.
分析学生对二氧化碳的3个典型学科认知障碍,以“二氧化碳的捕捉”为情境,通过“尝试捕捉二氧化碳”“谁在捕捉二氧化碳”“捕捉背后的原理”等3个主要环节,实现对学科认知障碍的突破,展示了一种新的中考复习教学思路。 相似文献
45.
This paper deals with the Cauchy–Dirichlet problem for the fractional Cahn–Hilliard equation. The main results consist of global (in time) existence of weak solutions, characterization of parabolic smoothing effects (implying under proper condition eventual boundedness of trajectories), and convergence of each solution to a (single) equilibrium. In particular, to prove the convergence result, a variant of the so-called ?ojasiewicz–Simon inequality is provided for the fractional Dirichlet Laplacian and (possibly) non-analytic (but ) nonlinearities. 相似文献
46.
Jerry Ray Dias 《Molecular physics》2020,118(12)
Cycloparaphenylene ([r]CPP) and cyclacene ([r]CA) series are models for short carbon nanotubes. It is shown that armchair edges in model cycloparaphenylenes possess greater aromaticity and cyclic conjugation than do zigzag edges in model cyclacenes. According to Aihara’s bond resonance energy (BRE) and Bosanac and Gutman energy effect (ef) measurements, cycloparaphenylenes are twice as aromatic as cyclacenes. The general solution of all eigenvalues of all members of the cycloparaphenylene series is given. The origin of the recurrence of some eigenvalues are determined. 相似文献
47.
48.
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
49.
Gas-phase 21Ne nuclear magnetic resonance spectra were measured at the natural abundance of 21Ne isotope for samples consisting of pressurized neon up to 60 bar at room temperature and applying the magnetic field of the strength B0 = 11.7574 T. It showed that the nuclear magnetic resonance frequency is linearly dependent on the density of gaseous neon. The resonance frequency was extrapolated to the zero-density point, and it permitted the determination of the 21Ne nuclear magnetic moment, μ(21Ne) = 0.6617774(10) μN. The present value of μ(21Ne) is not influenced by the bulk magnetic susceptibility of neon and interactions between neon atoms; therefore, it is more precise and reliable than the previous result obtained for μ(21Ne). 相似文献
50.