全文获取类型
收费全文 | 365028篇 |
免费 | 2600篇 |
国内免费 | 787篇 |
专业分类
化学 | 166161篇 |
晶体学 | 5131篇 |
力学 | 17864篇 |
综合类 | 16篇 |
数学 | 40334篇 |
物理学 | 106044篇 |
无线电 | 32865篇 |
出版年
2020年 | 3617篇 |
2019年 | 4541篇 |
2018年 | 6389篇 |
2017年 | 6392篇 |
2016年 | 8187篇 |
2015年 | 3838篇 |
2014年 | 7336篇 |
2013年 | 14656篇 |
2012年 | 11456篇 |
2011年 | 13542篇 |
2010年 | 11170篇 |
2009年 | 11792篇 |
2008年 | 13526篇 |
2007年 | 13599篇 |
2006年 | 12191篇 |
2005年 | 10960篇 |
2004年 | 10448篇 |
2003年 | 9545篇 |
2002年 | 9625篇 |
2001年 | 10576篇 |
2000年 | 8147篇 |
1999年 | 6403篇 |
1998年 | 5698篇 |
1997年 | 5616篇 |
1996年 | 5059篇 |
1995年 | 4555篇 |
1994年 | 4617篇 |
1993年 | 4540篇 |
1992年 | 4771篇 |
1991年 | 5092篇 |
1990年 | 5029篇 |
1989年 | 4998篇 |
1988年 | 4742篇 |
1987年 | 4505篇 |
1986年 | 4230篇 |
1985年 | 5380篇 |
1984年 | 5363篇 |
1983年 | 4572篇 |
1982年 | 4570篇 |
1981年 | 4401篇 |
1980年 | 4072篇 |
1979年 | 4615篇 |
1978年 | 4724篇 |
1977年 | 4882篇 |
1976年 | 4961篇 |
1975年 | 4638篇 |
1974年 | 4494篇 |
1973年 | 4757篇 |
1972年 | 3728篇 |
1971年 | 3462篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
M. I. Kurkin V. V. Leskovets V. V. Nikolaev E. A. Turov L. V. Turov 《Physics of the Solid State》2003,45(4):685-690
The possibility of excitation of NMR signals by an ac electric field in magnetically ordered crystals is discussed. Such signals can be recorded using the time-dependent component of the electric polarization vector. It is assumed that the electric and magnetic characteristics are coupled to each other through magnetoelectric and antiferroelectric interactions. Several types of magnetic structures are analyzed in which these interactions are not forbidden by symmetry. Such structures include two-sublattice single-position ferro-and antiferromagnetic phases in centrosymmetrical crystals, two-sublattice magnetic crystals without a center of symmetry (such as KNiPO4), and four-sublattice antiferromagnetic crystals with three types of antiferromagnetism vectors (such as Cr2O3 and α-Fe2O3). 相似文献
972.
S. S. Andreev A. D. Akhsakhalyan M. A. Bibishkin N. I. Chkhalo S. V. Gaponov S. A. Gusev E. B. Kluenkov K. A. Prokhorov N. N. Salashchenko F. Schafers S. Yu. Zuev 《Central European Journal of Physics》2003,1(1):191-209
We present research investigations in the field of multilayer optics in X-ray and extreme ultra-violet ranges (XUV), aimed
at the development of optical elements for applications in experiments in physics and in scientific instrumentation. We discuss
normal incidence multilayer optics in the spectral region of “water window”, multilayer optics for collimation and focusing
of hard X-ray, multilayer dispersing elements for X-ray spectroscopy of high-temperature plasma, multilayer dispersing elements
for analysis of low Z-elements. Our research pays special attention to optimization of multilayer optics for projection EUV-lithography
(ψ-13nm) and short period multilayer optics. 相似文献
973.
Computability and computational complexity were first considered over the fields of real and complex numbers and generalized to arbitrary algebraic systems. This article approaches the theory of computational complexity over an arbitrary algebraic system by taking computability over the list extension for a computational model of it. We study the resultant polynomial complexity classes and mention some NP-complete problems. 相似文献
974.
We consider some types of packet discretization for continuous spectra in quantum scattering problems. As we previously showed, this discretization leads to a convenient finite-dimensional (i.e., matrix) approximation for integral operators in the scattering theory and allows reducing the solution of singular integral equations connected with the scattering theory to some suitable purely algebraic equations on an analytic basis. All singularities are explicitly singled out. Our primary emphasis is on realizing the method practically. 相似文献
975.
This paper develops a theory for the global solution of nonconvex optimization problems with parameter-embedded linear dynamic systems. A quite general problem formulation is introduced and a solution is shown to exists. A convexity theory for integrals is then developed to construct convex relaxations for utilization in a branch-and-bound framework to calculate a global minimum. Interval analysis is employed to generate bounds on the state variables implied by the bounds on the embedded parameters. These bounds, along with basic integration theory, are used to prove convergence of the branch-and-bound algorithm to the global minimum of the optimization problem. The implementation of the algorithm is then considered and several numerical case studies are examined thoroughly 相似文献
976.
Azuelos G. Benslama K. Costanzo D. Couture G. Garcia J.E. Hinchliffe I. Kanaya N. Lechowski M. Mehdiyev R. Polesello G. Ros E. Rousseau D. 《The European Physical Journal C - Particles and Fields》2004,39(2):13-24
The European Physical Journal C - We discuss possible searches for the new particles predicted by Little Higgs Models at the LHC. By using a simulation of the ATLAS detector, we demonstrate how the... 相似文献
977.
H. Okumura T. Takahagi N. Nagai S. Shingubara 《Journal of Polymer Science.Polymer Physics》2003,41(17):2071-2078
The structural change in the depth direction of a polyimide (UPILEX‐S) film treated in alkaline solution, which was a representative surface treatment used to form a seed layer for plating and to improve the adhesive strength, was analyzed by means of micro Fourier transform infrared attenuated total reflection (FTIR‐ATR) line analysis with gradient shaving preparation. The polyimide film was treated with KOH. The imide ring opened through the alkaline treatment, and the amide structure and carboxylic acid salt were formed. The attainment depth of this structural change was almost proportional to the treatment time, and it reached about 8 μm after a 30‐min treatment. The degree of structural change through the alkaline treatment was almost constant after it reached a considerably degraded stage, and the chemically changed region penetrated into the inner part of the film from the surface. An intermediate layer before the final degraded stage appeared in the treated layer, and its thickness increased with the treatment time. The region that was changed chemically by the alkaline treatment progressed to the inner part simultaneously and continuously as the treatment time increased. The combined use of gradient shaving preparation and micro FTIR‐ATR line analysis was found to be extremely effective for the depth profiling of organic materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2071–2078, 2003 相似文献
978.
A band-dominant function on the Euclidean sphere embedded in R q+1 is the restriction to this sphere of an entire function of q+1 complex variables having a finite exponential type in each of its variables. We develop a method to represent such a function using finitely many bits, using the values of the function at scattered sites on the sphere. The number of bits required in our representation is asymptotically the same as the metric entropy of the class of such functions with respect to any of the L p norms on the sphere. 相似文献
979.
V. N. Dubinin 《Journal of Mathematical Sciences》2004,122(6):3623-3629
The classical Schwarz inequality on the boundary of the disk for the functions regular in the disk is refined in various directions. Inequalities involving zeros of the function, an inequality for points mapped to symmetric points on the circle, and an inverse estimate for univalent functions are presented. Other inequalities are discussed, and the possibility of applying them to estimates of polynomials and rational functions is indicated. Bibliography: 17 titles. 相似文献
980.