全文获取类型
收费全文 | 225693篇 |
免费 | 6690篇 |
国内免费 | 4035篇 |
专业分类
化学 | 102411篇 |
晶体学 | 3170篇 |
力学 | 13638篇 |
综合类 | 250篇 |
数学 | 37066篇 |
物理学 | 79883篇 |
出版年
2023年 | 897篇 |
2022年 | 1268篇 |
2021年 | 1935篇 |
2020年 | 2126篇 |
2019年 | 1989篇 |
2018年 | 11336篇 |
2017年 | 12099篇 |
2016年 | 7254篇 |
2015年 | 3423篇 |
2014年 | 3591篇 |
2013年 | 6418篇 |
2012年 | 10962篇 |
2011年 | 20315篇 |
2010年 | 12721篇 |
2009年 | 12729篇 |
2008年 | 17011篇 |
2007年 | 20279篇 |
2006年 | 5492篇 |
2005年 | 11786篇 |
2004年 | 7784篇 |
2003年 | 7025篇 |
2002年 | 4765篇 |
2001年 | 4853篇 |
2000年 | 3830篇 |
1999年 | 2985篇 |
1998年 | 2279篇 |
1997年 | 2120篇 |
1996年 | 2047篇 |
1995年 | 1857篇 |
1994年 | 1700篇 |
1993年 | 1481篇 |
1992年 | 1828篇 |
1991年 | 1756篇 |
1990年 | 1605篇 |
1989年 | 1414篇 |
1988年 | 1426篇 |
1987年 | 1455篇 |
1986年 | 1212篇 |
1985年 | 1527篇 |
1984年 | 1500篇 |
1983年 | 1088篇 |
1982年 | 1096篇 |
1981年 | 1037篇 |
1980年 | 938篇 |
1979年 | 1151篇 |
1978年 | 1154篇 |
1977年 | 1090篇 |
1976年 | 1045篇 |
1975年 | 897篇 |
1974年 | 902篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
91.
92.
The stable phase equilibria of quaternary systems LiBr-NaBr-MgBr2-H2O and LiBr-KBr-MgBr2-H2O at 298.15 K were studied by both experimental measurement(isothermal solution saturation method) and theoretical prediction(Pitzer model). The solubilities of the saturated solution have been determined experimentally and two stable phase diagrams and relevant water diagrams of the two quaternary systems were obtained. Results show that quaternary system LiBr-NaBr-MgBr2-H2O is hydrate II type as NaBr and NaBr·2H2O coexistence. Its phase diagram consists of only one invariant point, four univariant curves, and five crystallization fields. The quaternary system LiBr-KBr-MgBr2-H2O is a complex type as the double salt KBr·MgBr2·6H2O formed. In addition to this double salt, the three single salts LiBr·2H2O, KBr and MgBr2·6H2O also crystallize. In this paper, the solubilities of phase equilibria in above quaternary systems were also calculated by the Pitzer's electrolyte solution model. All the needed parameters can be obtained from the literature or be fitted by experimental data. On the Basis of the experimental and calculated results, the phase diagram of the quaternary system was plotted for comparison. It shows that the calculation results are consistent with the experimental ones. 相似文献
93.
Turyanskiy A. G. Vorob’ev N. S. Gizha S. S. Makushina V. A. Mikhal’kov Yu. M. Smirnov A. V. Pirshin I. V. Senkov V. M. Shashkov E. V. Fishman R. I. Ziyatdinova M. Z. Komel’kov A. S. 《JETP Letters》2020,112(11):734-738
JETP Letters - The possibility of stable generation of intense characteristic Cs radiation upon electronic excitation of a Mo anode target heat treated in Cs and O2 vapors is demonstrated. The... 相似文献
94.
Experimental Mechanics - There have been relatively few studies on mechanical properties of nanomaterials under high strain rates, mainly due to the lack of capable nanomechanical testing devices.... 相似文献
95.
Sh. M. Khaliullin V. D. Zhuravlev V. G. Bamburov L. V. Ermakova 《Physics of Atomic Nuclei》2015,78(12):1382-1388
Submicron CaZrO3 powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO3 powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics. 相似文献
96.
Susana Estopiñá-Durán Liam J. Donnelly Euan B. Mclean Bryony M. Hockin Prof. Alexandra M. Z. Slawin Dr. James E. Taylor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(15):3950-3956
A combination of pentafluorophenylboronic acid and oxalic acid catalyses the dehydrative substitution of benzylic alcohols with a second alcohol to form new C−O bonds. This method has been applied to the intermolecular substitution of benzylic alcohols to form symmetrical ethers, intramolecular cyclisations of diols to form aryl-substituted tetrahydrofuran and tetrahydropyran derivatives, and intermolecular crossed-etherification reactions between two different alcohols. Mechanistic control experiments have identified a potential catalytic intermediate formed between the aryl boronic acid and oxalic acid. 相似文献
97.
Shi-Chun Mao Zhaohui Zhang Jiansen Gao Zhen-Sen Wu 《Waves in Random and Complex Media》2019,29(1):54-62
A solution to the problem of Gaussian beam scattering by an anisotropically coated circular cylinder is presented. The incident Gaussian beam source is expanded as an approximate expression in the simple form with a Tayor’s series. The transmitted field in the anisotropically coated region is expressed as a infinite summation of eigen plane waves with different polar angles. The unknown coefficients of the scattered fields are obtained with the aid of the boundary conditions. The infinite series can be truncated under the prerequisite of achieving the solution convergence. Only the case of transverse-electric polarization is discussed. The similar formulation of transverse-magnetic polarization can be obtained by adopting the similar method. Some numerical results are presented and discussed. The result is in agreement with that available as expected when the Gaussian beam degenerates to a plane wave incidence case. 相似文献
98.
Nonlinear Dynamics - We generalize previously obtained solutions to the generalized nonlinear Schrödinger equation (NLSE) with cubic-quintic nonlinearity and distributed coefficients to obtain... 相似文献
99.
Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon(NAOS)method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition(PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate.The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×1015 cm-3. When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA. 相似文献
100.