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81.
82.
83.
王立中 《中国科学A辑(英文版)》2002,45(12):1578-1581
In this paper, we focus on the structure of p-blocks with defect group satisfying some special condition. These special conditions
include: two elements of the defect group are conjugate to each other in defect D if and only if they are conjugate to each
other in G; the number of conjugacy classes whose p-part is contained in P by conjugacy is not larger than ∣P∣ 相似文献
84.
W.H. Enright 《Numerical Algorithms》2002,31(1-4):125-137
In the last decade it has become standard for students and researchers to be introduced to state-of-the-art numerical software through a problem solving environment (PSE) rather than through the use of scientific libraries callable from a high level language such as Fortran or C. In this paper we will identify the constraints and implications that this imposes on the ODE software we investigate and develop. In particular, the way a numerical solution is displayed and viewed by a user dictates that new measures of performance and quality must be adopted. We will use the MATLAB environment and ODE software for initial value problems, boundary value problems and delay problems to illustrate the issues that arise and the progress that has been made. One of the major implications is the expectation that accurate approximations at off-mesh points must be provided. Traditional numerical methods for ODEs have produced approximations to the underlying solution on an associated discrete, adaptively chosen mesh. In recent years it has become common for the ODE software to also deliver approximations at off-mesh values of the independent variable. Such a feature can be extremely valuable in applications and leads to new measures of quality and performance which are more meaningful to users and more consistently interpreted and implemented in contemporary ODE software. Numerical examples of the robust and reliable behaviour of such software will be presented and the cost/reliability trade-offs that arise will be quantified. 相似文献
85.
N. B. Éshkobilov 《Journal of Applied Spectroscopy》2002,69(3):477-479
The main series of a silver atom with n = 5–70 are investigated. Perturbations of the np
2
P
1/2,3/2 states with n = 10 and 17 caused by interaction with the selfionization 4d5s5p
4
P
1/2,3/2 states are detected. Energies of the selfionization states are determined. 相似文献
86.
The effect of the grain boundary microstructure on the anisotropy and coercivity was investigated in an HDDR Nd-Fe-B permanent
magnetic alloy. Considering the special microstructure of its magnetic powder grain, an anisotropic theoretical model influenced
simultaneously by the structure defect at the grain boundary and the exchange coupling interaction was put forward. The variations
of the structure defect factors based on the nucleation and pinning mechanism with 2r
0/lex (where r
0 and lex are the defect thickness and the length of exchange coupling, respectively) were calculated. The results show that the coercivity
mechanism of an HDDR Nd-Fe-B permanent magnetic alloy is greatly related to its microstructure defect at the grain boundary.
For a fixed lex, when 2r
0/lex < 1.67, the coercivity is controlled by the pinning mechanism; when 2r
0/lex > 1.67, it is determined by the nucleation mechanism. The coercivity reaches the maximum when 2r
0/lex = 1.67. The calculation result is consistent well with the experimental result given by Morimoto et al.
Supported by the National Natural Science Foundation of China (Grant No. 50671055) 相似文献
87.
Several aspects of localized defects in the Frenkel-Kontorova, classicalXY chain and analogous models with a finite range of interactions are discussed from a general point of view. Precise definitions are given for defect phase shifts (charges) and for creation, pinning, and interaction energies. Corresponding definitions are also provided for interfaces (localized regions separating two phases). For the nearest-neighbor Frenkel-Kontorova model, the various defect energies are related to areas enclosed by contours joining heteroclinic points of the area-preserving map generated by the conditions of mechanical equilibrium. 相似文献
88.
分析了制作高功率连续激光反射镜材料的热性能、缺陷及其加工工艺, 提出了制作高功率激光反射镜应考虑的几个关键问题: 反射镜材料的综合热性能比值S, 材料的微观结构、缺陷的大小和晶向的选择, 以及加工工艺的设计。并介绍了实验结果。 相似文献
89.
G.V. Lewis C.R.A. Catlow A.N. Cormack 《Journal of Physics and Chemistry of Solids》1985,46(11):1227-1233
We present the results of a computer simulation study of the defect formation and migration energies in Fe3O4. Calculated Frenkel and Schottky energies are found to be similar in magnitude and both are considerably reduced by screening due to electron redistribution around the charged-defect species. The calculations also suggest that cation diffusion is mainly effected by a colinear interstitialcy mechanism at low Po2 and by a simple octahedral vacancy mechanism at higher Po2. 相似文献
90.
A general trend of supramolecular chemistry is the building of mesoscopic-oriented nanotubes. When the typical radius of the channel almost fits the mean supramolecular cross-sectional radius, the guest supramolecule is ultraconfined in the channel. In that case, only rotational disorder around the channel axis is allowed. For sufficiently low temperatures, we expect this 2D disorder to be static on the NMR timescale, and it should reflect the local symmetry of the channels. In this article, we show that experiments performed with deuterium single crystal solid-state NMR as a function of rotation around the channel axis may lead to important information concerning the static orientational disorder of the confined supramolecules. Using an inversion method with Tikhonov regularization and a positivity constraint, that also takes into account of the nonideal pulse sequence response, the orientational probability density can be obtained from 1D experiments performed at different angles, even for significant disorder. As a first step, the method is validated on four different theoretical distributions. It is then applied to 2H NMR single crystal experiments performed on an archetype of parallel channels intergrowth compounds: selectively deuterated 1,10-decanedicarboxylic diacids in hydrogenated urea channels. The diacids form one-dimensional infinite hydrogen-bonded chains ultraconfined in urea linear channels. 相似文献