全文获取类型
收费全文 | 27272篇 |
免费 | 5846篇 |
国内免费 | 3670篇 |
专业分类
化学 | 11283篇 |
晶体学 | 350篇 |
力学 | 1956篇 |
综合类 | 303篇 |
数学 | 3289篇 |
物理学 | 19607篇 |
出版年
2024年 | 39篇 |
2023年 | 277篇 |
2022年 | 512篇 |
2021年 | 714篇 |
2020年 | 881篇 |
2019年 | 690篇 |
2018年 | 698篇 |
2017年 | 924篇 |
2016年 | 1094篇 |
2015年 | 1084篇 |
2014年 | 1593篇 |
2013年 | 2157篇 |
2012年 | 1792篇 |
2011年 | 1930篇 |
2010年 | 1734篇 |
2009年 | 1869篇 |
2008年 | 2031篇 |
2007年 | 1969篇 |
2006年 | 1812篇 |
2005年 | 1630篇 |
2004年 | 1500篇 |
2003年 | 1370篇 |
2002年 | 1220篇 |
2001年 | 1013篇 |
2000年 | 949篇 |
1999年 | 859篇 |
1998年 | 703篇 |
1997年 | 605篇 |
1996年 | 514篇 |
1995年 | 410篇 |
1994年 | 385篇 |
1993年 | 270篇 |
1992年 | 253篇 |
1991年 | 204篇 |
1990年 | 158篇 |
1989年 | 187篇 |
1988年 | 121篇 |
1987年 | 102篇 |
1986年 | 84篇 |
1985年 | 96篇 |
1984年 | 59篇 |
1983年 | 30篇 |
1982年 | 62篇 |
1981年 | 42篇 |
1980年 | 27篇 |
1979年 | 28篇 |
1978年 | 18篇 |
1977年 | 15篇 |
1976年 | 17篇 |
1973年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
131.
132.
133.
关于体上分块矩阵的群逆 总被引:1,自引:0,他引:1
本文利用分块矩阵方法.研究了体上两个矩阵乘积的群逆的存在性及表示形式,给出了体上两个矩阵乘积群逆存在的充分必要条件和表示形式.并且在一定条件下.给出了体上分块矩阵的群逆存在性及表示形式. 相似文献
134.
MAIO Hong GAO Chong-Shou ZHUANG Peng-Fei 《理论物理通讯》2006,46(12)
Bound states, such as qq and q(q), may exist in quark-gluon plasma. As the system is at high density,the volume of the bound states may evoke a reduction in the phase space. We introduce an extended bag model to investigate qualitatively the volume effect on the properties of the system. We find a limit temperature where the bound states start to be completely melted. 相似文献
135.
Based on the effective-field theory with self-spin correlations and the differential operator technique,physical properties of the spin-2 system with biaxial crystal field on the simple cubic, body-centered cubic, as well as faced-centered lattice have been studied. The influences of the external longitudinal magnetic field on the magnetization,internal energy, specific heat, and susceptibility have been discussed in detail. The phenomenon that the magnetization in the ground state shows quantum effects produced by the biaxial transverse crystal field has been found. 相似文献
136.
采用固相反应合成了四羟基苯基卟啉与与Fe^2+,Co^2+金属离子的配合物,在室温下,将其与分子O2作用,提纯后得到两种固态氧合配合物.通过元素分析、红外光谱(IR)、核磁共振氢谱(^1HNMR)、电导、热分析(TG/DTA)、紫外光谱(UV)等测试手段确定了氧合配合物的组成为[Co·THPP·O2](NO3)2·2H2O、[Fe·THPP·O2]Cl2·2H2O],可知1mol配合物吸收了1molO2,采用失重法测定了氧合配合物中的配位氧,确定1mol金属配合物吸收1molO2形成超氧配合物. 相似文献
137.
The knowledge of hydrocarbon/water phase equilibria is important in the design and operation of equipment for petroleum transport and refining and petrochemical plants. The presence of water in a hydrocarbon mixture can affect the product quality and damage the operation equipment due to corrosion and formation of gas hydrates. Tracing the concentration of hydrocarbons in aqueous media is also important for technical purposes like preventing oil spills and for ecological concerns such as predicting the fate of these organic pollutants in the environment. 相似文献
138.
Wilson A. Cañas-Marín Julián D. Ortiz-Arango Uriel E. Guerrero-Aconcha Claudia P. Soto-Tavera 《Fluid Phase Equilibria》2007
The ability of Soave–Redlich–Kwong cubic equation of state (SRK EoS) to predict densities and thermodynamic derivative properties such as thermal expansivity, isothermal compressibility, calorific capacity, and Joule–Thompson coefficients, for two gas condensates over a wide range of pressures (up to 110 MPa) was studied. The predictions of the EoS were compared to Monte Carlo simulation data obtained by Lagache et al. [M.H. Lagache, P. Ungerer, A. Boutin, Fluid Phase Equilibr. 220 (2004) 221]. Two completely different alpha functions for the SRK EoS attractive term were used and their respective effects on the predictions of such properties were analyzed. Also, two different forms of the crossed terms of the attractive parameter, aij, and three expressions of the crossed terms of the repulsive parameter, bij, were combined in different ways, and predictions were carried out. Little sensitivity of the properties on the chosen alpha function, except for the calorific capacities, was found in the systems studied. The most commonly used combination rules to model phase behavior of reservoir fluids, i.e. geometric and arithmetic forms of aij and bij, respectively, predicted very deficient results for these fluids at extreme conditions, specially for density calculations. 相似文献
139.
Khaled A. Aamer Gregory N. Tew 《Journal of polymer science. Part A, Polymer chemistry》2007,45(6):1109-1121
Supramolecular block‐random copolymers containing [Ir(terpy)2]3+ in the side chain were synthesized via postfunctionalization of a P(S‐b‐ACterpy) block copolymer. Absorbance and emission spectra compared to a model compound show that the polymer backbone has a minor effect on the polymer absorbance but produces a larger shift for the phosphorescence signals to higher wavelength. Dynamic light scattering of the metal complex containing copolymer studied in various solvents showed monomodal aggregation with decreasing aggregate size as the solvent dielectric constant increased. The copolymer precursor P(S‐b‐ACterpy) shows multimodal aggregation in different solvents with the major population consisting of single chains. This difference in behavior between the two polymers is attributed to the electrolytic nature of the complex and the amphiphilicity induced by the charged metal complex. Supramolecular copolymers like these will continue to have interesting self‐organizational properties and may find applications in multicomponent systems for photoinduced charge separation processes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1109–1121, 2007 相似文献
140.
认为物质的质量(能量)存在形式可分为两部分,一部分是以纯物质形式存在的,另一部分是以纯重力场形式存在的.物质质量(能量)这两种形式各自对应着相应的能量 动量张量,物质总的能量-动量张量可表示为Tμν=T(Ⅰ)μν+T(Ⅱ)μν,这里,T(Ⅰ)μν,T(Ⅱ)μν分别代表物质纯物质部分和纯重力场部分的能量-动量张量.通过类比电磁理论,定义:ωμ≡-c2gμ0/g00,并引入一个反对称张量Dμν=ωμ/xν-ων/xμ,则物质纯重力场部分的能量-动量张量为T(Ⅱ)μν=(DμρDρν-gμνDαβDαβ/4
关键词:
能量-动量张量
纯重力场
重力场方程
标量重力势
矢量重力势 相似文献