全文获取类型
收费全文 | 8177篇 |
免费 | 742篇 |
国内免费 | 1126篇 |
专业分类
化学 | 72篇 |
力学 | 207篇 |
综合类 | 187篇 |
数学 | 8380篇 |
物理学 | 1199篇 |
出版年
2024年 | 9篇 |
2023年 | 87篇 |
2022年 | 82篇 |
2021年 | 127篇 |
2020年 | 174篇 |
2019年 | 244篇 |
2018年 | 236篇 |
2017年 | 244篇 |
2016年 | 259篇 |
2015年 | 177篇 |
2014年 | 401篇 |
2013年 | 628篇 |
2012年 | 332篇 |
2011年 | 476篇 |
2010年 | 466篇 |
2009年 | 659篇 |
2008年 | 625篇 |
2007年 | 656篇 |
2006年 | 550篇 |
2005年 | 497篇 |
2004年 | 419篇 |
2003年 | 444篇 |
2002年 | 389篇 |
2001年 | 248篇 |
2000年 | 288篇 |
1999年 | 270篇 |
1998年 | 240篇 |
1997年 | 218篇 |
1996年 | 134篇 |
1995年 | 74篇 |
1994年 | 64篇 |
1993年 | 42篇 |
1992年 | 35篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 16篇 |
1984年 | 27篇 |
1983年 | 15篇 |
1982年 | 23篇 |
1981年 | 15篇 |
1980年 | 20篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The existence of solutions for the 2n-order m-point boundary value problem at resonance is obtained by using the coincidence degree theory of Mawhin.We give an example to demonstrate our result.The interest is that the nonlinear term may be noncontinuous. 相似文献
102.
The kinetics of crack growth in a viscoelastic orthotropic plate made of a composite material is analyzed. The external load is the superposition of a cyclic load and a constant tensile load. The level of the tensile load is assumed to exceed the amplitude of the cyclic load. The kinetic curves are compared with the constant tension curves. The effect of the cyclic component is studied.Translated from Prikladnaya Mekhanika, Vol. 40, No. 9, pp. 116–122, September 2004. 相似文献
103.
Variable Order and Distributed Order Fractional Operators 总被引:1,自引:0,他引:1
Many physical processes appear to exhibit fractional order behavior thatmay vary with time or space. The continuum of order in the fractionalcalculus allows the order of the fractional operator to be considered asa variable. This paper develops the concept of variable and distributedorder fractional operators. Definitions based on the Riemann–Liouvilledefinition are introduced and the behavior of the new operators isstudied. Several time domain definitions that assign different argumentsto the order q in the Riemann–Liouville definition are introduced. Foreach of these definitions various characteristics are determined. Theseinclude: time invariance of the operator, operator initialization,physical realization, linearity, operational transforms, and memorycharacteristics of the defining kernels.A measure (m
2) for memory retentiveness of the order history isintroduced. A generalized linear argument for the order q allows theconcept of `tailored' variable order fractional operators whose m
2 memory may be chosen for a particular application. Memory retentiveness (m
2) andorder dynamic behavior are investigated and applications are shown.The concept of distributed order operators where the order of thetime based operator depends on an additional independent (spatial)variable is also forwarded. Several definitions and their Laplacetransforms are developed, analysis methods with these operators aredemonstrated, and examples shown. Finally operators of multivariable anddistributed order are defined and their various applications areoutlined. 相似文献
104.
In this paper a basic, easily to multi-contact problems extendable, non-smooth approach is applied to analyze a bar striking an inelastic half-space. Coulomb contact is assumed and modeled by using set-valued Newtonian impact laws in normal as well as in tangential direction. The resulting linear complementarity problem contains all possible impact states and provides an instantaneous collision operator that respects all inequality constraints. This operator depends on the orientation of the bar and determines uniquely the post-impact velocities as functions of the pre-impact state. Different types of solutions may occur, including “stick’’ and “slip’’. In this context, stick and slip have to be understood as the two cases characterized by the tangential impulsive force as an element of either the set-valued or of the single-valued domain of the friction law. Depending on the choice of parameters, sign reversal of the tangential contact velocity is possible. For certain inertia properties and initial conditions, the collision operator yields an impact, even for initially vanishing normal contact velocity. This phenomenon is well known as the Painlevé paradox. The results obtained by this fully non-smooth rigid body approach are compared with those of other impact models, such as a lumped mass model with compliance elements, and a collision operator used for particle interactions in flows.AMR: 160A, 160B, 160Y, 292B, 292Y 相似文献
105.
WANG Shou-dong 《应用数学和力学(英文版)》2005,26(8):1007-1016
IntroductionWith the development of modern industry, various pollutants discharge into the air,rivers, lakes and oceans, which makes the environmental qualities worse and has bad effectson the mankind’s health and the sustained development of industry an… 相似文献
106.
This paper deals with the spectral and qualitative problems associated with the one-dimensional ergodic Schrödinger equation. Let A
2 be the set of those energies for which the real projective flow admits an invariant linear measure with square integrable density function. On this set we calculate the directional derivative of the Floquet coefficient and prove the existence of a nontangential limit of the Weyl m-functions in the L
1-topology. In particular, we verify that the known Dieft–Simon inequality for the derivative of the rotation number obtained from Kotani's theory is in fact an equality. In the bounded orbit case we deduce the uniform boundedness of the Weyl m-functions and obtain necessary and sufficient conditions to assure their uniform convergence. 相似文献
107.
Ionel Sorinel Ciuperca 《Journal of Dynamics and Differential Equations》1998,10(1):73-108
We consider the Schrödinger operator on two types of domains depending on a small parameter : dumbbell domains and thin domains with varying orders of thinness. In both situations we compare the eigenvalues and eigenvectors of the Schrödinger operator with the corresponding eigenvalues and eigenvectors of a limit operator defined on the limit domain. 相似文献
108.
We characterize boundedness, compactness and weak compactness of Volterra operators acting between different weighted Banach spaces of entire functions with sup‐norms in terms of the symbol g; thus we complement recent work by Bassallote, Contreras, Hernández‐Mancera, Martín and Paul 3 for spaces of holomorphic functions on the disc and by Constantin and Peláez 16 for reflexive weighted Fock spaces. 相似文献
109.
Simon P. Eveson Vladimir D. Stepanov Elena P. Ushakova 《Mathematische Nachrichten》2015,288(8-9):877-897
An embedding inequality of Sobolev type is characterized in the paper with help of a duality principle and boundedness criteria for the Hardy–Steklov integral operator in weighted Lebesgue spaces. 相似文献
110.
In this study, we propose a modelling framework for evaluating companies financed by random liabilities, such as insurance companies or commercial banks. In this approach, earnings and costs are driven by double exponential jump–diffusion processes and bankruptcy is declared when the income falls below a default threshold, which is proportional to the charges. A change of numeraire, under the Esscher risk neutral measure, is used to reduce the dimension. A closed form expression for the value of equity is obtained in terms of the expected present value operators, with and without disinvestment delay. In both cases, we determine the default threshold that maximizes the shareholder’s equity. Subsequently, the probabilities of default are obtained by inverting the Laplace transform of the bankruptcy time. In numerical applications of the proposed model, we apply a procedure for calibration based on market and accounting data to explain the behaviour of shares for two real-world examples of insurance companies. 相似文献