全文获取类型
收费全文 | 10550篇 |
免费 | 573篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 164篇 |
综合类 | 13篇 |
化学工业 | 2283篇 |
金属工艺 | 338篇 |
机械仪表 | 583篇 |
建筑科学 | 222篇 |
矿业工程 | 3篇 |
能源动力 | 477篇 |
轻工业 | 960篇 |
水利工程 | 33篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 1841篇 |
一般工业技术 | 2156篇 |
冶金工业 | 711篇 |
原子能技术 | 99篇 |
自动化技术 | 1249篇 |
出版年
2024年 | 11篇 |
2023年 | 127篇 |
2022年 | 178篇 |
2021年 | 309篇 |
2020年 | 237篇 |
2019年 | 252篇 |
2018年 | 299篇 |
2017年 | 307篇 |
2016年 | 367篇 |
2015年 | 315篇 |
2014年 | 494篇 |
2013年 | 707篇 |
2012年 | 688篇 |
2011年 | 805篇 |
2010年 | 593篇 |
2009年 | 629篇 |
2008年 | 602篇 |
2007年 | 473篇 |
2006年 | 420篇 |
2005年 | 374篇 |
2004年 | 337篇 |
2003年 | 294篇 |
2002年 | 258篇 |
2001年 | 220篇 |
2000年 | 202篇 |
1999年 | 173篇 |
1998年 | 333篇 |
1997年 | 216篇 |
1996年 | 185篇 |
1995年 | 118篇 |
1994年 | 92篇 |
1993年 | 81篇 |
1992年 | 51篇 |
1991年 | 47篇 |
1990年 | 36篇 |
1989年 | 34篇 |
1988年 | 31篇 |
1987年 | 30篇 |
1986年 | 15篇 |
1985年 | 31篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1981年 | 15篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1976年 | 16篇 |
1974年 | 10篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
S J Chung S Balaji M Matheswaran T Ramesh I S Moon 《Water science and technology》2007,55(1-2):261-266
This study investigates the hybrid mediated electrochemical oxidation (HMEO) technology, which is a newly developed non thermal electrochemical oxidation process for organic destruction. A combination of ozone and ultrasonication processes to the mediated electrochemical oxidation (MEO) process is termed as hybrid mediated electrochemical oxidation. The electrochemical cell was developed in this laboratory. In the present study, several organic compounds, such as phenol, benzoquinone and ethylenediaminetetraacetic acid (EDTA), were chosen as the model organic pollutants to be destructed by the hybrid process. The organic destruction was monitored based on the CO2 generation and total organic carbon (TOC) reduction. The HMEO process was found to be extremely effective in the destruction of all the target organics chosen in this study. The information obtained from this study will provide an insight in adopting this technique for dealing with more recalcitrant organics (POPs). 相似文献
22.
An adaptable die is one that not only produces the correct geometrical shape, but also is designed through an adaptable method to impart other desirable properties to the product or process. In this first part of a series of papers, six kinematically admissible velocity fields are developed for use in upper bound models for axisymmetric extrusion through various dies, including extrusion through adaptable dies. Three base velocity fields are presented:
- (1) assuming proportional angles in the deformation zone,
- (2) assuming proportional areas in the deformation zone, or
- (3) assuming proportional distances from the centerline in the deformation zone.
23.
Material structure for attaining pure Poisson-shearing 总被引:1,自引:0,他引:1
Teik-Cheng Lim 《Journal of Materials Science Letters》2002,21(20):1595-1597
24.
Public participation is essential in each step of the nuclear-related decision-making process. Recently, the electronic systems using the Internet have become quite popular, and have emerged as a good medium for communicating with the public. In this study, a comprehensive utilization of electronic public participation was used to analyze public opinion on a given nuclear-related decision-making process. The degree of deliberation and meditation of the public participating in an electronic poll survey was evaluated, and the decision-making factors representing the personal characteristics of the poll respondents such as age, income, education, residence, degree of knowledge and concern were carefully incorporated when preparing the poll-survey questionnaire for its evaluation. Fuzzy analysis was used to assess and aggregate the responses to each decision-making factor. As a case study, this procedure was used to analyzing public opinion on the location of a low-level radioactive waste disposal facility on the campus of Seoul National University. The results show that there is a tendency of respondents who are on the negative side of the argument to be more deliberate and meditative in their decision-making process than those on the positive side. Knowledge and residence were found to be important decision-making factors. 相似文献
25.
The deactivation characteristics of Pd/SiO2 in the selective hydrogenation of acetylene were correlated with changes in the amount of the C4 species produced. The amounts of butenes produced changed in parallel with the catalyst activity, indicating that the rate limiting step for butene production was the same as that for acetylene hydrogenation. On the other hand, the amount of 1,3-butadiene produced changed, showing a maximum with catalyst deactivation because 1,3-butadiene is an intermediate in the sequential reaction process which involves both the production and consumption of 1,3-butadiene. This was verified by a simultaneous TG/reaction experiment showing that 1,3-butadiene was a precursor of green oil. The catalyst showed a self-regenerative behavior in its activity and the amounts of C4 species produced during the early stage of deactivation because two opposite factors, which contributed to either the lowering or the promotion of activity, were involved in the process. A specific type of polymer species, produced during the initial period of deactivation, is proposed to be responsible for the promotion of catalyst activity. 相似文献
26.
For multi-step heterogeneous consecutive reactions affected entirely by interphase diffusion under isothermal condition, the
equations for the effectiveness factors, the surface concentrations and the point yields were derived in terms of the Damkoehler
numbers or the measurables from the mass balances set up on the assumption that the mass-transfer rate balances the surface-reaction
rate at steady state.
From the analyses of the equations derived, the effectiveness factors for the intermediate steps and the surface concentrations
of intermediates were understood to be enhanced by the measurables inclusive of the concentrations and the mass-transfer coefficients.
Then the effect of the concentrations was concluded to be most significant. The effects of these measurables to the effectiveness
factors and the surface concentrations were qualitatively discussed for simple consecutive reactions and also for additive
consecutive reactions. Especially, as for two-step additive consecutive reactions, the effects of measurables η Da and the
concentrations to the effectiveness factors were examined with graphical presentations.
Finally, the brief discussion of the dependency of the Damkoehler number upon reaction time and the effect of the Renolds
number and diffusivity to the extent of the mass-transfer resistance were presented. 相似文献
27.
28.
Dongho Chae O. Yu. Imanuvilov Sang Moon Kim 《Journal of Dynamical and Control Systems》1996,2(4):449-483
This paper studies the problem of exact boundary controllability of second-order semilinear parabolic equations when the control is under Neumann's boundary conditions. For a nonlinear term with a sublinear growth we prove the global null-controllability and for the superlinear growth case we prove the local exact controllability of the equations. 相似文献
29.
Thirteen scenarios were used to measure and compare the perceptions of elder abuse and help-seeking behaviors of African-American, Caucasian American, and Korean-American elderly women. Significant group differences existed in their perceptions of elder abuse with regard to six scenarios, and the Korean-American women were substantially less likely to perceive a given situation as abusive than the other groups. The three groups also showed significant differences in their intended use of formal and informal sources of help in the case of elder abuse. 相似文献
30.
Kyutae Lim Sang Seol Lee 《Antennas and Propagation, IEEE Transactions on》1995,43(11):1325-1328
An exact analytic solution of a plane electromagnetic (EM) wave scattered by an eccentric multilayered sphere (EMS) is obtained. It is assumed that the layers are perfect dielectrics and that the innermost core is a perfectly conducting sphere. Each center of a layer is translated along the incident axis. All fields are expanded in terms of the spherical vector wave functions with unknown expansion coefficients. The addition theorem for spherical wave functions is used prior to applying the boundary conditions. The unknown coefficients are determined by solving a system of linear equations derived from the boundary conditions. Numerical results of the scattering cross sections are presented on the plane of φ=0 degrees and φ=90 degrees. The convergence of modal solutions and the characteristics of patterns are examined with various geometries and permittivity distributions 相似文献