全文获取类型
收费全文 | 18723篇 |
免费 | 2231篇 |
国内免费 | 1768篇 |
专业分类
化学 | 12753篇 |
晶体学 | 517篇 |
力学 | 1746篇 |
综合类 | 121篇 |
数学 | 632篇 |
物理学 | 6953篇 |
出版年
2024年 | 52篇 |
2023年 | 297篇 |
2022年 | 479篇 |
2021年 | 566篇 |
2020年 | 901篇 |
2019年 | 581篇 |
2018年 | 504篇 |
2017年 | 676篇 |
2016年 | 964篇 |
2015年 | 912篇 |
2014年 | 1038篇 |
2013年 | 1451篇 |
2012年 | 945篇 |
2011年 | 1160篇 |
2010年 | 1014篇 |
2009年 | 1130篇 |
2008年 | 1229篇 |
2007年 | 1257篇 |
2006年 | 1061篇 |
2005年 | 899篇 |
2004年 | 855篇 |
2003年 | 817篇 |
2002年 | 599篇 |
2001年 | 493篇 |
2000年 | 428篇 |
1999年 | 348篇 |
1998年 | 317篇 |
1997年 | 266篇 |
1996年 | 242篇 |
1995年 | 187篇 |
1994年 | 191篇 |
1993年 | 152篇 |
1992年 | 130篇 |
1991年 | 90篇 |
1990年 | 87篇 |
1989年 | 71篇 |
1988年 | 56篇 |
1987年 | 52篇 |
1986年 | 47篇 |
1985年 | 31篇 |
1984年 | 36篇 |
1983年 | 22篇 |
1982年 | 30篇 |
1981年 | 17篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1971年 | 6篇 |
1970年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
Summary The RHF and geometry optimization sections of the ab initio quantum chemistry code, GAMESS, have been optimized for a network of parallel microprocessors, Inmos T800-20 transputers, using both indirect and direct SCF techniques. The results indicate great scope for implementation of such codes on small parallel computer systems, very high efficiencies having been achieved, particularly in the cases of direct SCF and geometry optimization with large basis sets.The work, although performed upon one particular parallel system, the Meiko Computing Surface, is applicable to a wide range of parallel systems with both shared and distributed memory. 相似文献
112.
The conformation and dimension of SPU polyanion have been studied by viscosity and quasi-elastic light scattering methods. The rigidity of SPU is somewhat similar to CMC and its hydrodynamic radius decreases only slowly with increasing concentration of NaCl. 相似文献
113.
Hans -Peter Deutsch 《Journal of statistical physics》1992,67(5-6):1039-1082
A complete outline is given for how to determine the critical properties of polymer mixtures with extrapolation methods similar to the Ferrenberg-Swendsen techniques recently devised for spin systems. By measuring not only averages but the whole distribution of the quantities of interest, it is possible to extrapolate the data obtained in only a few simulations nearT
c
over the entire critical region, thereby saving at least 90% of the computer time normally needed to locate susceptibility peaks or cumulant intersections and still getting more precise results. A complete picture of the critical properties of polymer mixtures in the thermodynamic limit is then obtained with finite-size scaling functions. Since the amount of information extracted from a simulation in this way is drastically increased as compared to conventional methods, the investigation of mixtures with long chains or built-in asymmetries is now possible. As an example, the critical points, exponents, and amplitudes of dense, symmetric polymer mixtures with chain lengths ranging fromN=16 up toN=256 are determined within the framework of the 3D bond fluctuation model using grand canonical simulation techniques. As an example for an asymmetry, the generalization of the method to asymmetric monomer potentials is briefly discussed. 相似文献
114.
115.
含氰基的酚醛树脂,具有优异的耐高温性能和高温下的机械强度,在315℃下性能变化甚小;不着火,发烟量低,有良好的加工成型性能。热固化过程中氰基成三嗪环而交联,没有小分子脱出,是一类具有广泛发展前景的新型热固性树脂。 相似文献
116.
Almeria Natansohn 《先进技术聚合物》1994,5(3):133-145
The recent literature on polymeric charge transfer complexes is reviewed with emphasis on the author's own work. After a definition of the area and a survey of investigations on the spatial arrangement of donor and acceptor sites in the solid state, a variety of applications of these complexes is presented. Electrically conductive polymers are excluded. These applications are: compatibilization of polymer blends, liquid crystalline supramolecular organization, new developments in photo-conductivity, electroluminescence, nonlinear optical properties, photorefractivity and reversible optical storage. 相似文献
117.
Polypropylenes of differing morphologies were examined by differential thermal analysis. The problems of reordering during
the programmed heating are discussed. Four potential procedures by which the reordering could be inhibited are considered,
and three of these are experimentally assessed. Their advantages and deficiencies are identified. Two pretreatments, an etching
and a crosslinking, are recognised as able to qualitatively characterise the initial morphology, with a preference for the
former. A test to identify the occurrence of reordering is identified.
In celebration of the 60th birthday of Dr. Andrew K. Galwey 相似文献
118.
Organically modified solid-state silicates (ORMOSILS) doped with a new laser dye 1,3,5,7,8-pentamethylpyrromethene-2,6-disulfonate-BF2 complex (pyrromethene 556) have been synthesized by a sol-gel method and the compositional effects on pore characteristics, fluorescence and lasing properties have been investigated. It is found that the use of dimethylsulfoxide and γ-glycidoxypropyltrimethoxysilane could greatly change the structure properties of sol-gel derived ORMOSILS cage, and thus the fluorescence and lasing properties of the materials could improve significantly. A successful laser oscillation from this dye-doped ORMOSILS sample has been achieved upon pumping with a Q-switched frequency-doubled Nd:YAG laser at 532 nm. A slope efficiency of 54% with a useful lifetime greater than 10,000 shots has been demonstrated at a pump repetition rate of 1 Hz and a pump intensity of 1 J/cm2 by using the new ORMOSILS cage on our newly designed laser system. Our results have shown that it is possible to obtain a high-efficiency with a long-lifetime for a compact new laser device by low cost dye-doped solid-state ORMOSILS. 相似文献
119.
Summary Two polyampholyte copolymers based on sodium-2-acrylamido-2-methylsulfonate (NaAMPS) and methacryloyloxyethyltrimethylammonium
chloride (MADQUAT) have been prepared either in homogeneous solution or by an inverse microemulsion polymerization technique.
The copolymer microstructure was shown to depend on the method of preparation. The microemulsion polymerization yields copolymers
with a monomer sequence distribution not far from random while those obtained by polymerization in solution have a strong
tendency to alternation. The aqueous-solution properties of the two samples have been investigated by viscometry. The results
show that the charge distribution along the copolymer chain affects considerably its conformation, in good agreement with
recent theoretical studies.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994 相似文献
120.
Summary A Modified-Melt-Powder-Melt-Growth (MMPMG) technique has been developed for the preparation of melt-textured Y-Ba−Cu−O pellets.
To test their performances, the samples were characterized with respect to their microstructure, pinning strength and interaction
force with permanent magnets. A superconducting magnetic bearing was built and integrated in a levitating flywheel system
for energy storage.
Paper presented at the “VII Congresso SATT?, Torino, 4–7 October 1994.
Under a Fondazione Confalonieri grant. 相似文献