全文获取类型
收费全文 | 2636篇 |
免费 | 590篇 |
国内免费 | 181篇 |
专业分类
化学 | 532篇 |
晶体学 | 9篇 |
力学 | 289篇 |
综合类 | 54篇 |
数学 | 894篇 |
物理学 | 1629篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 50篇 |
2021年 | 46篇 |
2020年 | 50篇 |
2019年 | 52篇 |
2018年 | 71篇 |
2017年 | 87篇 |
2016年 | 91篇 |
2015年 | 66篇 |
2014年 | 161篇 |
2013年 | 194篇 |
2012年 | 172篇 |
2011年 | 199篇 |
2010年 | 161篇 |
2009年 | 187篇 |
2008年 | 195篇 |
2007年 | 180篇 |
2006年 | 160篇 |
2005年 | 140篇 |
2004年 | 142篇 |
2003年 | 118篇 |
2002年 | 117篇 |
2001年 | 107篇 |
2000年 | 97篇 |
1999年 | 76篇 |
1998年 | 93篇 |
1997年 | 63篇 |
1996年 | 61篇 |
1995年 | 47篇 |
1994年 | 22篇 |
1993年 | 29篇 |
1992年 | 23篇 |
1991年 | 21篇 |
1990年 | 14篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有3407条查询结果,搜索用时 15 毫秒
151.
本文提出了一种CAD/CAM齿形误差的最优化算法。本算法收敛速度快、拟合误差小,能够按照预定设计要求对齿形精度加以控制,实现最优化自动搜索,同时给出数值计算结果。 相似文献
152.
Z.?Simic M.?S.?DimitrijevicEmail author L.?C.?Popovic M.?D.?Dacic 《Journal of Applied Spectroscopy》2005,72(3):443-446
Using a semiclassical approach, we have considered electron-, proton-, and ionized helium-impact line widths and shifts for
the F III 2p3
4So-3s 4P resonant line. Moreover, for 10 F III multiplets where the full semiclassical perturbation approach is not applicable in
an adequate way due to the lack of reliable atomic data, electron-impact line widths have been calculated within the modified
semiempirical approach. Results are obtained as a function of temperature for perturber density of 1017 cm−3. The theoretical data obtained have been used to consider the influence of Stark broadening for A-type star atmosphere conditions.
__________
Published in Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 3, pp. 412–415, May–June, 2005. 相似文献
153.
The conditions for realization of the regime of self-oscillations of the intensity of a continuously pumped solid-state laser have been qualitatively analyzed using a system of kinetic equations. It has been established that, in the case where a thin semiconductor layer absorbing light at frequencies close to the lasing frequency is placed into the cavity of such a laser, self-oscillations of its radiation intensity arise as a result of the amplitude-phase self-modulation of the laser light field.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 136–139, January–February, 2005. 相似文献
154.
David Jacquemart Robert Gamache 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,96(2):205-239
This paper describes a semi-empirical calculation of the air-broadened half-widths and the air pressure-induced frequency shifts for the H216O isotopologue. This semi-empirical calculation is based on fits of several recent high-quality measurements and theoretical calculations to the first-order terms in the expansion of the complex Robert-Bonamy (CRB) equations, which yields a second- and first-order polynomial function of the differences in the upper- and lower-state vibrational quantum numbers for the half-width and line shift, respectively. The aim of this work was to obtain a complete set of air-broadened half-widths and air pressure-induced frequency shifts for transitions of H216O present in the HITRAN database from microwave to the visible in order to supplement the observed and calculated values. For around 700 sets of rotational quantum numbers (), semi-empirical coefficients describing the vibrational dependence of the air-broadened half-widths and the air pressure-induced frequency shifts have been obtained directly from the fit of experimental and/or theoretical data. The accuracy of the parameters deduced from this calculation is estimated to be between 5% and 10% for the air-broadened half-widths and between 0.001 and for the air pressure-induced frequency shifts. For sets of rotational quantum numbers for which either none or insufficient experimental/theoretical data were available to deduce a vibrational dependence, further approximations have been used to obtain a complete set of semi-empirical coefficients. 相似文献
155.
Vincent Mathew 《International Journal of Infrared and Millimeter Waves》2005,26(4):563-573
This paper presents an analysis of frequency dependent propagation characteristics of microstrip lines with anisotropic substrate and overlay. The method involves setting up of the Greens functions corresponding to the structure and formulating a dispersion relation in Fourier transform domain. The dispersion relation is constructed in a Galerkins procedure. Numerical results are also presented. 相似文献
156.
A.?A.?MakovetskiiEmail author Yu.?S.?Milyavskii L.?M.?Averina A.?A.?Zamyatin 《Journal of Applied Spectroscopy》2004,71(6):916-921
The curing kinetics of films produced from compositions based on UV-curable oligourethaneacrylates is investigated using, as a source of radiation, an individual spectral line separated by a monochromator from the radiation of a DRT-400 mercury tubular lamp. It has been established that in the region of spectral sensitivity of the composition, the curing time of the film is inversely proportional to the intensity of volumetric absorption of the radiation-source photons by the initiator at the lower surface of the film under study. Individual contributions of some of the lines to the process of composition curing by using the integral spectrum of the radiation source have been evaluated. The spectral-kinetic results obtained were confirmed when using the compositions under study as protective coatings of optical quartz fibers.Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 71, No. 6, pp. 836–840, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date. 相似文献
157.
In this paper we describe vanishing and non-vanishing of cohomology of “most” line bundles over Schubert subvarieties of flag
varieties for rank 2 semisimple algebraic groups. 相似文献
158.
S.?IzumiyaEmail author D.?Pei M.?C.?Romero-Fuster M.?Takahashi 《Bulletin of the Brazilian Mathematical Society》2004,35(2):177-198
We introduce the notion of horospherical ridges for submanifolds of codimension 2 in hyperbolic n-space, and study some of their properties.*Work partially supported by DGCYT grant no. BFM2003-02037. 相似文献
159.
Neural Network Models for Finline Discontinuities 总被引:1,自引:0,他引:1
The radial basis network is used as the finline discontinuities electromagnetic artifical neural network(EMANN) models. EM software analysis is employed to characterize finline discontinuities. EMANN models are then trained using physical parameters and frequency as inputs and equivalent electric circuit element parameters of finline discontinuities as outputs. Once trained , the EMANN models can simulate equivalent electric circuit element parameters of finline step, notch and strip very fast and efficiently. 相似文献
160.
Yuan-Qing Qiao Franklin D. Tall 《Proceedings of the American Mathematical Society》2003,131(12):3929-3936
In this paper we prove the equivalence between the existence of perfectly normal, non-metrizable, non-archimedean spaces and the existence of ``generalized Souslin lines", i.e., linearly ordered spaces in which every collection of disjoint open intervals is -discrete, but which do not have a -discrete dense set. The key ingredient is the observation that every first countable linearly ordered space has a dense non-archimedean subspace.