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991.
Linear Frameworks for Block Ciphers 总被引:1,自引:0,他引:1
Inthis paper we generalize the structure of the ciphers Shark, Square, BKSQ, Crypton and Rijndael. We show that the linearcomponents play an essential role in the effect of the nonlinearS-boxes in providing resistance against differential and linearcryptanalysis and provide upper bounds for the probability ofdifferential characteristics and the correlation of linear approximationsfor the general structure. We show how good linear componentscan be constructed efficiently from Maximum-Distance Separablecodes. The presented block cipher structure can make optimaluse of a wide range of processor word lengths and its parallelismallows very fast dedicated hardware implementations. Cipherswith variable block length can be constructed by varying certainparameters in the presented structure. 相似文献
992.
Reiko Heckel Hartmut Ehrig Uwe Wolter Andrea Corradini 《Applied Categorical Structures》2001,9(1):83-110
The classical algebraic approach to graph transformation is a mathematical theory based on categorical techniques with several interesting applications in computer science. In this paper, a new semantics of graph transformation systems (in the algebraic, double-pushout (DPO) approach) is proposed in order to make them suitable for the specification of concurrent and reactive systems. Classically, a graph transformation system comes with a fixed behavioral interpretation. Firstly, all transformation steps are intended to be completely specified by the rules of the system, that is, there is an implicit frame condition: it is assumed that there is a complete control about the evolution of the system. Hence, the interaction between the system and its (possibly unknown) environment, which is essential in a reactive system, cannot be modeled explicitly. Secondly, each sequence of transformation steps represents a legal computation of the system, and this makes it difficult to model systems with control. The first issue is addressed by providing graph transformation rules with a loose semantics, allowing for unspecified effects which are interpreted as activities of the environment. This is formalized by the notion of double-pullback transitions, which replace (and generalize) the well-known double-pushout diagrams by allowing for spontaneous changes in the context of a rule application. Two characterizations of double-pullback transitions are provided: the first one describes them in terms of extended direct DPO derivations, and the second one as incomplete views of parallel or amalgamated derivations. The issue of constraining the behavior of a system to transformation sequences satisfying certain properties is addressed instead by introducing a general notion of logic of behavioral constraints, which includes instances like start graphs, application and consistency conditions, and temporal logic constraints. The loose semantics of a system with restricted behavior is defined as a category of coalgebras over a suitable functor. Such category has a final object which includes all finite and infinite transition sequences satisfying the constraints. 相似文献
993.
基于Poincare变换的滑动轴承非线性油膜力数据库方法 总被引:16,自引:0,他引:16
运用状态空间Poincare变换使径向滑动轴承动力系统的部分状态变量由无限区间变换到有限区间,在经过变换的状态空间中求解Reynolds方程,建立了径向滑动轴承非线性油膜力数据库及相应的插值拟合程序,实现了非线性油膜力的快速准确获得。通过滑动轴承,转子系统运动瞬态分析和Poincare映射方法验证了数据库及拟合程序的精度。 相似文献
994.
995.
K.T. Joseph A.S. Vasudeva Murthy 《NoDEA : Nonlinear Differential Equations and Applications》2001,8(2):173-193
In this paper we study a system of nonlinear partial differential equations which we write as a Burgers equation for matrix
and use the Hopf-Cole transformation to linearize it. Using this method we solve initial value problem and initial boundary
value problems for some systems of parabolic partial differential equations. Also we study an initial value problem for a
system of nonlinear partial differential equations of first order which does not have solution in the standard distribution
sense and construct an explicit solution in the algebra of generalized functions of Colombeau.
Received November 1999 相似文献
996.
Double-wave description of mesoscopic resistance-inductance-capacitance coupled circuit with power source
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Quantum fluctuations in the mesoscopic capacitance-inductance-resistance coupled circuit with a power source are investigated using canonical transformation and a double wavefunction. We confirm that the fluctuations are not influenced by the power source. As a new method, the double wavefunction describes a single system of the coupled circuit, whereas the single wavefunction describes a quantum ensemble. 相似文献
997.
998.
氯柱硼镁石的合成及其在20℃水中的溶解相转化动力学研究 总被引:2,自引:0,他引:2
报道了合成氯柱硼镁石的快捷方法及该复盐在20℃水中的溶解和相转化过程.结果表明:该复盐在水中呈现不同步溶解,首先溶脱掉MgCl2·6H2O,生成中间产物MgO·B2O2·4H2O,随后发生转化,最终转化产物是2MgO·3B2O2·15H2O.拟合出了溶解转化结晶动力学方程,提出了溶解转化结晶反应机制. 相似文献
999.
Joon T. Park John R. Shapley Kwangyeol Lee Hyunjoon Song 《Journal of Cluster Science》2000,11(2):343-358
A comprehensive review of the hydrocarbon derivative chemistry of WOs3 mixed-metal cluster compounds including synthesis, reactivity, ligand transformation, and solution dynamics is presented. 相似文献
1000.
Ultrafine aluminum nitride (AlN) powders were obtained by chemical vapor deposition via AlCl3–NH3–N2 system operated at various temperatures and at a same 200 cm3/min flow rate of NH3 and N2, respectively. It has been shown that when the reaction temperature of AlCl3 and NH3 was above 600°C, then crystalline AlN powder can be formed; whereas, amorphous AlN was obtained with NH4Cl if reacted in a lower-temperature zone of the reaction chamber. The amorphous AlN powder was heat treated at 1400°C under NH3 and N2 atmosphere for 2 h, then the crystalline phases of the obtained powder belong to a single phase of AlN; a mixture of AlN and Al2O3 and only AlON, respectively. On the other hand, if crystalline AlN powder is heat treated at 1400°C under N2 atmosphere for 2 h, the crystalline phases were composed of the major phase of AlN and a minor phase of Al2O3. The morphology, particle size and agglomerate size of the AlN powder were strongly dependent on the heat-treatment temperature. The particle size of AlN powder increases from 28.1 to 45.0 nm, as the heat treatment temperature increases from 800 to 1400°C. 相似文献