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971.
Evolutionary structural optimisation using an additive algorithm 总被引:1,自引:0,他引:1
The evolutionary structural optimisation (ESO) method has been under continuous development since 1992. Traditionally, the method was conceived from the engineering perspective that the topology and shape of structures were naturally conservative for safety reasons and therefore contained an excess of material. To move from the conservative design to a more optimum design would therefore involve the removal of material. Thus the ESO method started from a design space much bigger than the optimum and the final topology or shape emerged by a process of removal of unwanted/inefficient/lowly stresses material. The original algorithms allowed for two forms of evolution. One was there the understressed material could be removed from anywhere in the allowable design space, and with compensation for checker-boarding this produces an optimum topology under the prescribed environments. The second form only allows removal from the surface or parts of the surface (called nibbling in the ESO lexicon); this produces a Min–Max situation where the maximum surface stress is reduced to a minimum. It has been demonstrated that the ESO process produces a surface that is an iso-stress contour thus satisfying the Min–Max optimality criterion. The present paper addresses the opposite evolutionary process whereby the structure evolves from a base which is the minimum structural form required to carry the load regardless of the magnitude of the stress levels. Material is added in the proximity of high stress to ameliorate its effect and hence the final structural form emerges. Only singly connected regions are formed in the present analysis and thus the additive ESO process is the opposite of the nibbling SO, mentioned above, that produces optimum surface shapes. The paper presents a brief background to the current state of structural optimisation research. This is followed by a discussion of the strategies for the additive ESO (AESO) algorithm and two examples are presented. 相似文献
972.
Statistical energy analysis (SEA) is commonly used in industry to predict high-frequency vibrational response of structures. Since only local modes are used in SEA, only high-frequency responses can be predicted. This study extends SEA to the middle-frequency region by additionally using global modes. Methods using impedance matrices that can be found by NASTRAN are developed. Then the results are post processed to determine coupling loss factors. 相似文献
973.
Toshiyuki Sugawa 《Transactions of the American Mathematical Society》2001,353(9):3603-3615
In this note, we show, in a quantitative fashion, that the limit set of a non-elementary Kleinian group is uniformly perfect if the quotient orbifold is of Lehner type, i.e., if the space of integrable holomorphic quadratic differentials on it is continuously contained in the space of (hyperbolically) bounded ones. This result covers the known case when the group is analytically finite. As applications, we present estimates of the Hausdorff dimension of the limit set and the translation lengths in the region of discontinuity for such a Kleinian group. Several examples will also be given.
974.
V. V. Korableva 《Siberian Mathematical Journal》2008,49(2):273-286
We determine the ranks of the permutation representations of the simple groups B l (q), C l (q), and D l (q) on the cosets of the parabolic maximal subgroups. 相似文献
975.
Fuyi Li Yanbiao Zhang Yuhua Li 《Journal of Mathematical Analysis and Applications》2008,344(1):417-428
In this paper, we consider the fourth-order Neumann boundary value problem u(4)(t)−2u″(t)+u(t)=f(t,u(t)) for all t∈[0,1] and subject to u′(0)=u′(1)=u?(0)=u?(1)=0. Using the fixed point index and the critical group, we establish the existence theorem of solutions that guarantees the problem has at least one positive solution and two sign-changing solutions under certain conditions. 相似文献
976.
本文简要介绍了计算C G系数的生群元矩阵方程法,给出计算二十面体群C G系数时采用的简化计算方法,并给出了Ⅰ群C G系数的计算结果。 相似文献
977.
In this paper, adaptive finite element method is developed for the estimation of distributed parameter in elliptic equation.
Both upper and lower error bound are derived and used to improve the accuracy by appropriate mesh refinement. An efficient
preconditioned project gradient algorithm is employed to solve the nonlinear least-squares problem arising in the context
of parameter identification problem. The efficiency of our error estimators is demonstrated by some numerical experiments.
相似文献
978.
Xin Tang 《Frontiers of Mathematics in China》2008,3(3):371-397
In this paper, we construct families of irreducible representations for a class of quantum groups U
q
(ƒ
m
(K)). First, we give a natural construction of irreducible weight representations for U
q
(ƒ
m
(K)) using methods in spectral theory developed by Rosenberg. Second, we study the Whittaker model for the center of U
q
(ƒ
m
(K)). As a result, the structure of Whittaker representations is determined, and all irreducible Whittaker representations are
explicitly constructed. Finally, we prove that the annihilator of a Whittaker representation is centrally generated.
相似文献
979.
In this paper, we prove that a group G is isomorphic to M, where M is a simple K
4-group, if and only if the following hold: (1) |G| = |M|, (2) nse(G) = nse(M).
相似文献
980.
We study primitive theta functions, which were first introduced by Shintani, in a purely local setting. We investigate a metaplectic representation of U(1) acting on the space of local primitive theta functions and give its explicit irreducible decomposition. As a by-product, we give a new proof of epsilon dichotomy for (U(1),U(1)). 相似文献