全文获取类型
收费全文 | 650篇 |
免费 | 28篇 |
国内免费 | 62篇 |
专业分类
化学 | 87篇 |
晶体学 | 1篇 |
力学 | 25篇 |
综合类 | 3篇 |
数学 | 483篇 |
物理学 | 141篇 |
出版年
2024年 | 1篇 |
2023年 | 14篇 |
2022年 | 15篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 16篇 |
2018年 | 11篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 20篇 |
2014年 | 34篇 |
2013年 | 57篇 |
2012年 | 28篇 |
2011年 | 43篇 |
2010年 | 28篇 |
2009年 | 42篇 |
2008年 | 61篇 |
2007年 | 30篇 |
2006年 | 33篇 |
2005年 | 36篇 |
2004年 | 17篇 |
2003年 | 19篇 |
2002年 | 28篇 |
2001年 | 20篇 |
2000年 | 7篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有740条查询结果,搜索用时 15 毫秒
81.
Jiunn-Wei Chen Hiroaki Kohyama Kazuaki Ohnishi Udit Raha Yue-Long Shen 《Physics letters. [Part B]》2010
We present a combined analysis of the space- and time-like electromagnetic pion form factors in light-cone perturbative QCD with transverse momentum dependence and Sudakov suppression. Including the genuine non-perturbative “soft” QCD and the power suppressed twist-3 corrections to the standard twist-2 perturbative QCD result, the experimental form factor data available at moderate energies/momentum transfers can be explained reasonably well. To this end, the bulk of the existing discrepancy between the space- and time-like experimental data is ostensibly reconciled. 相似文献
82.
Amit Verma 《Physics letters. A》2010,374(8):1009-1020
A generalized notion of higher order nonclassicality (in terms of higher order moments) is introduced. Under this generalized framework of higher order nonclassicality, conditions of higher order squeezing and higher order subpoissonian photon statistics are derived. A simpler form of the Hong-Mandel higher order squeezing criterion is derived under this framework by using an operator ordering theorem introduced by us in [A. Pathak, J. Phys. A 33 (2000) 5607]. It is also generalized for multi-photon Bose operators of Brandt and Greenberg. Similarly, condition for higher order subpoissonian photon statistics is derived by normal ordering of higher powers of number operator. Further, with the help of simple density matrices, it is shown that the higher order antibunching (HOA) and higher order subpoissonian photon statistics (HOSPS) are not the manifestation of the same phenomenon and consequently it is incorrect to use the condition of HOA as a test of HOSPS. It is also shown that the HOA and HOSPS may exist even in absence of the corresponding lower order phenomenon. Binomial state, nonlinear first order excited squeezed state (NLESS) and nonlinear vacuum squeezed state (NLVSS) are used as examples of quantum state and it is shown that these states may show higher order nonclassical characteristics. It is observed that the Binomial state which is always antibunched, is not always higher order squeezed and NLVSS which shows higher order squeezing does not show HOSPS and HOA. The opposite is observed in NLESS and consequently it is established that the HOSPS and HOS are two independent signatures of higher order nonclassicality. 相似文献
83.
Djurdje Cvijovi? 《Physica A》2010,389(8):1594-1600
Lee, in a series of papers, described a unified formulation of the statistical thermodynamics of ideal quantum gases in terms of the polylogarithm functions, . It is aimed here to investigate the functions , for s=0,−1,−2,…, which are, following Lee, referred to as the polypseudologarithms (or polypseudologs) of order n≡−s. Various known results regarding polypseudologs, mainly obtained in widely differing contexts and currently scattered throughout the literature, have been brought together along with many new results and insights and they all have been proved in a simple and unified manner. In addition, a new general explicit closed-form formula for these functions involving the Carlitz-Scoville higher tangent numbers has been established. 相似文献
84.
85.
《Mathematische Nachrichten》2018,291(2-3):443-491
In this paper, we propose the concepts of Caputo fractional derivatives and Caputo type Hadamard fractional derivatives for piecewise continuous functions. We obtain general solutions of four classes of impulsive fractional differential equations (Theorem 3.1–Theorem 3.4) respectively. These results are applied to converting boundary value problems for impulsive fractional differential equations to integral equations. Some comments are made on recently published papers (see Section 4). 相似文献
86.
An explicit solution of the spectral problem of the non-local Schrödinger operator obtained as the sum of the square root of the Laplacian and a quartic potential in one dimension is presented. The eigenvalues are obtained as zeroes of special functions related to the fourth order Airy function, and closed formulae for the Fourier transform of the eigenfunctions are derived. These representations allow to derive further spectral properties such as estimates of spectral gaps, heat trace and the asymptotic distribution of eigenvalues, as well as a detailed analysis of the eigenfunctions. A subtle spectral effect is observed which manifests in an exponentially tight approximation of the spectrum by the zeroes of the dominating term in the Fourier representation of the eigenfunctions and its derivative. 相似文献
87.
《Annals of Pure and Applied Logic》2020,171(3):102754
We introduce a new axiom called inductive dichotomy, a weak variant of the axiom of inductive definition, and analyze the relationships with other variants of inductive definition and with related axioms, in the general second order framework, including second order arithmetic, second order set theory and higher order arithmetic. By applying these results to the investigations on the determinacy axioms, we show the following. (i) Clopen determinacy is consistency-wise strictly weaker than open determinacy in these frameworks, except second order arithmetic; this is an enhancement of Schweber–Hachtman separation of open and clopen determinacy into the consistency-wise separation. (ii) Hausdorff–Kuratowski hierarchy of differences of opens is faithfully reflected by the hierarchy of consistency strengths of corresponding parameter-free determinacies in the aforementioned frameworks; this result is valid also in second order arithmetic only except clopen determinacy. 相似文献
88.
By characterizing Asplund operators through Fréchet differentiability property of convex functions, we show the following Bishop–Phelps–Bollobás theorem: Suppose that X is a Banach space,T : X → C(K) is an Asplund operator with ║T║= 1, and that x_0 ∈ S_X, 0 ε satisfy ║T(x_0)║ 1-ε~2/2.Then there exist x_ε∈ S_X and an Asplund operator S : X → C(K) of norm one so that ║S(x_ε)║ = 1, x_0-x_ε ε and ║T-S║ ε.Making use of this theorem, we further show a dual version of Bishop–Phelps–Bollobás property for a strong Radon–Nikodym operator T : ?_1 → Y of norm one: Suppose that y_0~*∈ S_(Y~*), ε≥ 0 satisfy T~*(y_0~*) 1-ε~2/2. Then there exist y_ε~*∈ S_(Y~*), x_ε∈(±e_n), y_ε∈ S_Y, and a strong Radon–Nikodym operator S : ?_1 → Y of norm one so that (ⅰ)║S(x_ε)║= 1;(ⅱ) S(x_ε) = y_ε;(ⅲ)║T-S║ ε;(ⅳ)║S~*(y_ε~*)║=y_ε~*, y_ε= 1;(ⅴ)║y_0~*-y_ε~*║ ε and (ⅵ)║T~*-S~*║ ε,where(e_n) denotes the standard unit vector basis of ?_1. 相似文献
89.
At the meeting of the joint Bologna Declaration, EU representatives agreed on the establishment of a common European Higher Education Area by 2010. Since then, several universities have implemented pilot projects, although no formal research has been carried out to analyse their results. In this study, we analysed one of these pilot-projects with two objectives. First, we examined the performance of the new system as compared to that of the traditional system. We used a procedure based on a modified model of Data Envelopment Analysis that is able to distinguish students’ efficiency (managerial efficiency) from efficiency based on the educational programme used (programme efficiency). Then we analysed whether the different systems perform differently for different types of students. 相似文献
90.
分析独立学院高等数学课程体系的现状及存在的问题,阐述对独立学院高等数学课程体系构建的原则,并就课程体系中的教学模式、教学内容、与教材建设方面提出一些方案和建议. 相似文献