全文获取类型
收费全文 | 57336篇 |
免费 | 7861篇 |
国内免费 | 3947篇 |
专业分类
电工技术 | 10960篇 |
技术理论 | 1篇 |
综合类 | 6043篇 |
化学工业 | 6435篇 |
金属工艺 | 3063篇 |
机械仪表 | 3400篇 |
建筑科学 | 7201篇 |
矿业工程 | 1866篇 |
能源动力 | 2202篇 |
轻工业 | 1639篇 |
水利工程 | 2360篇 |
石油天然气 | 3326篇 |
武器工业 | 615篇 |
无线电 | 4999篇 |
一般工业技术 | 4958篇 |
冶金工业 | 2039篇 |
原子能技术 | 1035篇 |
自动化技术 | 7002篇 |
出版年
2024年 | 236篇 |
2023年 | 851篇 |
2022年 | 1690篇 |
2021年 | 2081篇 |
2020年 | 2243篇 |
2019年 | 2008篇 |
2018年 | 1877篇 |
2017年 | 2325篇 |
2016年 | 2382篇 |
2015年 | 2544篇 |
2014年 | 3739篇 |
2013年 | 3976篇 |
2012年 | 4245篇 |
2011年 | 4455篇 |
2010年 | 3217篇 |
2009年 | 3386篇 |
2008年 | 3191篇 |
2007年 | 3728篇 |
2006年 | 3415篇 |
2005年 | 2811篇 |
2004年 | 2464篇 |
2003年 | 2136篇 |
2002年 | 1721篇 |
2001年 | 1433篇 |
2000年 | 1246篇 |
1999年 | 1057篇 |
1998年 | 853篇 |
1997年 | 666篇 |
1996年 | 544篇 |
1995年 | 492篇 |
1994年 | 475篇 |
1993年 | 322篇 |
1992年 | 252篇 |
1991年 | 220篇 |
1990年 | 191篇 |
1989年 | 167篇 |
1988年 | 119篇 |
1987年 | 81篇 |
1986年 | 65篇 |
1985年 | 52篇 |
1984年 | 38篇 |
1983年 | 24篇 |
1982年 | 31篇 |
1981年 | 11篇 |
1980年 | 21篇 |
1979年 | 11篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1959年 | 8篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The results are given of numerical solution of the Boltzmann equation in a binomial approximation in view of elastic and inelastic electron collisions in Xe+CH4 mixtures and in pure methane. The electron energy distribution functions obtained are used to calculate the electron transport coefficients for E/N values of up to several Townsends, i.e., the drift velocity, mobility, average and characteristic energies, diffusion coefficient. The results of calculation for pure methane fit the available experimental data. A similarity rule is found for the electron transport coefficients in a Xe+CH4 mixture with different concentrations of methane molecules, which enables one to determine the values of transport coefficients in a mixture with a minor (less than 30 percents) methane content. 相似文献
102.
103.
Stepanov G. V. Kharchenko V. V. Babutskii A. I. Romanov S. V. Feofentov N. A. Kravchenko I. V. 《Strength of Materials》2004,36(3):321-326
The procedure for calculating the life of header – steam generator connector weld joints is proposed. It allows for running out the material plasticity reserve upon static cyclic elastoplastic loading as well as operating conditions, local stress concentrations, and residual stresses after welding. 相似文献
104.
We study the stressed state of an inhomogeneous welded joint containing an interlayer of a more high-strength material under the action of tensile loads. It is assumed that the contact boundary has a cracklike defect. We deduce analytic dependences of the fracture load on the mechanical inhomogeneity of the joint, thickness of the interlayer, and depth of the defect. The maximum depth of the defect to which the joint is insensitive is established. The proposed theoretical results are innovative and agree with the experimental data obtained for specimens cut out from a pipe of 14KhGS steel. 相似文献
105.
106.
向浩萍 《石油化工管理干部学院学报》2003,(2):26-29
在明确中国石化集团公司收入分配制度改革的目标模式下,从健全和完善企业激励机制的角度,对炼化企业职工收入分配制度中工资和奖金的分配设计提出改进措施和建议。 相似文献
107.
连铸钢坯质量的原位统计分布分析研究 总被引:14,自引:0,他引:14
采用原位统计分布分析技术得到与样品原位置相对应的数以万计原始信号并对其进行系统解析,实现不同质量连铸钢坯试样的疏松度、均匀度以及夹杂物含量的定量表征。准确计算了连铸钢坯试样疏松度、碳元素的最大偏析度。提出铸坯各原位置成分含量的权重比率方法用以表征材料的均匀度,并提供了统计分布允许差范围内(C0±R)所占权重比率以及权重比率为95%置信度时,中位值置信扩展率(K)等2种判断模式。该方法以测量信息的原始性、原位性及统计性为特征,反映了连铸钢坯较大尺度范围内各化学组成及其形态的定量统计分布规律。采用上述方法可以 相似文献
108.
The purpose of this study is to clarify damage process of “Type IV cracking” in weldment of a 2.25Cr-1Mo steel and to propose a micro damage prediction method. From continuous observation under a creep-fatigue test, it was found that spherical shape voids initiated and grew on grain boundaries in fine grain region and these voids grow continuously by changing their shape to crack-like. Both spherical and crack-like void growth rate equations were derived from the proposed void growth model. It was indicated that measured void growth rate under the creep-fatigue loading was well predicted by the growth rate equations. 相似文献
109.
R. Boroch J. Wiaranowski R. Mueller-Fiedler M. Ebert J. Bagdahn 《Fatigue & Fracture of Engineering Materials & Structures》2007,30(1):2-12
The aim of this work is to characterize the strength properties of polycrystalline silicon (polysilicon) with the use of tensile and bending test specimens. The strength of thin polysilicon films with different geometry, size and stress concentrations has been measured and correlated with the effective size of the specimen and its stress distribution. The test results are evaluated using a probabilistic strength approach based on the weakest link theory with the use of STAU software. The use of statistic methods of strength prediction of polysilicon test structures with a complex geometry and loading based on test values for standard material tests specimen has been evaluated. 相似文献
110.
Discussed in this paper is the Cartesian stiffness matrix, which recently has received special attention within the robotics
research community. Stiffness is a fundamental concept in mechanics; its representation in mechanical systems whose potential
energy is describable by a finite set of generalized coordinates takes the form of a square matrix that is known to be, moreover,
symmetric and positive-definite or, at least, semi-definite. We attempt to elucidate in this paper the notion of “asymmetric
stiffness matrices”. In doing so, we show that to qualify for a stiffness matrix, the matrix should be symmetric and either
positive semi-definite or positive-definite. We derive the conditions under which a matrix mapping small-amplitude displacement
screws into elastic wrenches fails to be symmetric. From the discussion, it should be apparent that the asymmetric matrix
thus derived cannot be, properly speaking, a stiffness matrix. The concept is illustrated with an example. 相似文献