全文获取类型
收费全文 | 35768篇 |
免费 | 2149篇 |
国内免费 | 3636篇 |
专业分类
化学 | 19474篇 |
晶体学 | 674篇 |
力学 | 1734篇 |
综合类 | 310篇 |
数学 | 5285篇 |
物理学 | 14076篇 |
出版年
2024年 | 20篇 |
2023年 | 155篇 |
2022年 | 544篇 |
2021年 | 760篇 |
2020年 | 764篇 |
2019年 | 980篇 |
2018年 | 1376篇 |
2017年 | 1599篇 |
2016年 | 1787篇 |
2015年 | 1084篇 |
2014年 | 1775篇 |
2013年 | 2605篇 |
2012年 | 2424篇 |
2011年 | 2562篇 |
2010年 | 2673篇 |
2009年 | 2666篇 |
2008年 | 2669篇 |
2007年 | 2501篇 |
2006年 | 2279篇 |
2005年 | 1643篇 |
2004年 | 1192篇 |
2003年 | 738篇 |
2002年 | 881篇 |
2001年 | 834篇 |
2000年 | 1131篇 |
1999年 | 755篇 |
1998年 | 710篇 |
1997年 | 642篇 |
1996年 | 270篇 |
1995年 | 178篇 |
1994年 | 174篇 |
1993年 | 126篇 |
1992年 | 141篇 |
1991年 | 119篇 |
1990年 | 110篇 |
1989年 | 93篇 |
1988年 | 74篇 |
1987年 | 66篇 |
1986年 | 63篇 |
1985年 | 56篇 |
1984年 | 50篇 |
1983年 | 60篇 |
1982年 | 28篇 |
1981年 | 34篇 |
1980年 | 20篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1975年 | 9篇 |
1968年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
O. I. Gyrdasova V. N. Krasil’nikov I. G. Grigorov G. V. Bazuev 《Russian Journal of Inorganic Chemistry》2006,51(6):949-955
The effect of ethylene glycol (EG) on the formation of whiskers and fibers of complex oxides with the general formula MCo2O4 upon the thermolysis of M1/3Co2/3C2O4 (M = Zn, Mn) oxalates has been studied. New compounds (solvates) are formed when powdered oxalates are heated with EG. In the solvates, EG molecules substitute for water molecules according to the reaction M1/3Co2/3C2O4 · 2H2O + HOCH2CH2OH = M1/3Co2/3C2O4(HOCH2CH2OH) + 2H2O. The solvates have been characterized using X-ray powder diffraction, microscopy, IR spectroscopy, thermogravimetry, and chemical analysis. The shape, structure, and particle size of the thermolysis products of EG-modified oxalates have been determined using scanning electron microscopy. 相似文献
72.
YBa2Cu3O7-x (YBCO) bulk is one of the most important high temperature superconducting materials for magnetic levitation applications, because it has a high magnetic irreversibility field Hirr at liquid nitrogen temperature, and can grow into large grains. The levitation force of YBCO bulk is proportional to the critical current density (Jc) and grain radius (r)[1], so higher Jc and r are appreciated for YBCO bulks to achieve higher levitation force. Now single-domain YBCO bulks up to s… 相似文献
73.
A Promising MoO_x-based Catalyst for n-Heptane Isomerization 总被引:1,自引:0,他引:1
Song Hai CHAI Xin Ping WANG* Ying Jun WANG Tian Xi CAI State Key Laboratory of Fine Chemicals Dalian University of Technology Dalian 《中国化学快报》2003,14(7)
The increasing demand for higher-octane gasoline and the regulations limiting the amount of aromatics in the fuel motivate the interest in catalytic isomerization of n-alkanes. In the last ten years, transition metal oxides or oxycarbides based on molybdenum or tungstate have attracted much attention due to their high activity and isomerization selectivity compared to the conventional bifunctional supported platinum catalyst and high resistance to sulphur and nitrogen catalyst poisons1-5. Ma… 相似文献
74.
75.
相对论重离子碰撞实验中混合事件方法的研究 总被引:1,自引:0,他引:1
把RQMD(Relativistic Quantum Molecular Dynamics)产生器产生的数据输入作为原始事例取样,讨论了在比较复杂的背景情况下,一种新的混合事件方法,用以证实在相对论重离子碰撞实验中高能量激发共振态的存在.并以共振态重子Δ++为例演示了这一方法的应用. 相似文献
76.
WANG Mingwei LI Bo FENG Kun RAO Jun KANG Zihua LI Xiujuan LILi WANG Minghong FAN Mingjie 《核工业西南物理研究院年报(英文版)》2004,(1):77-79
in order to study non-indutive plasma current production, the lower hybrid current drive(LHCD) experiment on the HL-2A tokamak is carried out. Simultaneously a microcomputer has been used to control the whole LHCD system. During the experiment this year, we can monitor and protect the LHCD system by use of the microcomputer control system, which will imediately switch off the microwave power to be launched into the tokamak if the plasma is disrupted. All this ensure that the microwave is injected into the equipment correctly. 相似文献
77.
Yu. A. Kumzerov L. S. Parfen’eva I. A. Smirnov H. Misiorek J. Mucha A. Jezowski 《Physics of the Solid State》2003,45(1):57-60
The thermal conductivity of crystalline chrysotile asbestos made up of hollow tubular Mg3Si2O5(OH)4 filaments is measured in the range 5–300 K. The paper discusses the possibility of using this material in studies of the thermal conductivity of thin filaments of metals and semiconductors incorporated into the channels of crystalline chrysotile asbestos tubes. 相似文献
78.
Jihua Zhang Xi WangWeidong Yu Tao FengFumin Zhang Zhihong ZhengQiong Li Xianghuai Liu 《Solid State Communications》2003,127(4):289-293
Effects of ion impinging on the microstructure and field electron emission properties of screen-printed carbon nanotube films were investigated. We observed that the plasma treatment modified the microstructure of CNTs along with the remarkable increase of emission site density. With the prolongation of ion impinging time, the emission current falls down first, and then rises up to higher than that of the untreated films. It is proposed that the change of emission characteristics is due to the different emission mechanisms. After the treatment, electrons are emitted predominantly from the nano-nodes on the tube wall instead from the nanotube tips. 相似文献
79.
The lattice IR reflection spectra of a ZnTe/Zn0.8Cd0.2Te superlattice measured at temperatures of 300 and 10 K are analyzed. The ZnTe/Zn0.8Cd0.2Te superlattice is grown by molecular-beam epitaxy on a GaAs substrate with a ZnTe buffer layer. It is found that the lattice IR reflection spectra of the studied structure exhibit only one reflection band. Dispersion analysis of the experimental spectrum has revealed the presence of one lattice TO mode close in frequency to the mode of pure ZnTe. This result is explained by a shift in the frequency of the lattice modes of the ZnTe and Zn0.8Cd0.2Te layers of the superlattice toward each other. In turn, this shift is caused by internal elastic stresses in the superlattice due to a mismatch between the lattice parameters of the materials of these layers. 相似文献
80.
V. Bradnova M. M. Chernyavsky L. Just S. P. Kharlamov A. D. Kovalenko M. Haiduc K. A. Kotel’nikov V. A. Krasnov V. G. Larionova F. G. Lepekhin A. I. Malakhov G. I. Orlova N. G. Peresadko N. G. Polukhina P. A. Rukoyatkin V. V. Rusakova N. A. Salmanova B. B. Simonov S. Vokal P. I. Zarubin 《Physics of Atomic Nuclei》2003,66(9):1646-1650
A physical program of irradiation of emulsions in beams of relativistic nuclei named the BECQUEREL Project is reviewed. It is destined to study in detail the processes of relativistic fragmentation of light radioactive and stable nuclei. The expected results would make it possible to answer some topical questions concerning the cluster structure of light nuclei. Owing to the best spatial resolution, the nuclear emulsions would enable one to obtain unique and evident results. The most important irradiations will be performed in the secondary beams of He, Be, B, C, and N radioactive nuclei formed on the basis of JINR Nuclotron beams of stable nuclei. We present results on the charged state topology of relativistic fragmentation of the 10B nucleus at low energy-momentum transfers as the first step of the research. 相似文献