全文获取类型
收费全文 | 9898篇 |
免费 | 739篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 188篇 |
综合类 | 5篇 |
化学工业 | 2315篇 |
金属工艺 | 391篇 |
机械仪表 | 620篇 |
建筑科学 | 165篇 |
矿业工程 | 4篇 |
能源动力 | 473篇 |
轻工业 | 854篇 |
水利工程 | 50篇 |
石油天然气 | 30篇 |
武器工业 | 2篇 |
无线电 | 1648篇 |
一般工业技术 | 2352篇 |
冶金工业 | 536篇 |
原子能技术 | 127篇 |
自动化技术 | 906篇 |
出版年
2024年 | 8篇 |
2023年 | 105篇 |
2022年 | 158篇 |
2021年 | 270篇 |
2020年 | 258篇 |
2019年 | 286篇 |
2018年 | 353篇 |
2017年 | 368篇 |
2016年 | 400篇 |
2015年 | 283篇 |
2014年 | 519篇 |
2013年 | 677篇 |
2012年 | 749篇 |
2011年 | 859篇 |
2010年 | 601篇 |
2009年 | 647篇 |
2008年 | 608篇 |
2007年 | 484篇 |
2006年 | 383篇 |
2005年 | 347篇 |
2004年 | 288篇 |
2003年 | 260篇 |
2002年 | 246篇 |
2001年 | 197篇 |
2000年 | 218篇 |
1999年 | 183篇 |
1998年 | 194篇 |
1997年 | 156篇 |
1996年 | 109篇 |
1995年 | 82篇 |
1994年 | 61篇 |
1993年 | 62篇 |
1992年 | 38篇 |
1991年 | 24篇 |
1990年 | 27篇 |
1989年 | 27篇 |
1988年 | 22篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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
42.
Photocatalytic degradation of methyl orange using heteropolytungstic acid-encapsulated TiSBA-15 总被引:1,自引:0,他引:1
Heteropolyphosphotungstic acid (H3PW12O40) (HPA)-encapsulated titanium-supported SBA15 nanoporous materials (HPA-TiSBA-15) were synthesized as a new photocatalyst, and they were characterized by FT-IR and 31P NMR MAS spectroscopic methods. Their photocatalytic effects on degradation of methyl orange in water were investigated under natural conditions, and it was found that a 4-fold increase in the photodegradation rate is observed in the presence of HPA-TiSBA-15 as compared to the rate observed in the presence of titanium-supported SBA15 nanoporous materials (TiSBA-15) without HPA. 相似文献
43.
Yoon Carolyn; Feinberg Fred; Hu Ping; Gutchess Angela Hall; Hedden Trey; Chen Hiu-Ying Mary; Jing Qicheng; Cui Yao; Park Denise C. 《Canadian Metallurgical Quarterly》2004,19(3):379
Understanding how aging influences cognition across different cultures has been hindered by a lack of standardized, cross-referenced verbal stimuli. This study introduces a database of such item-level stimuli for both younger and older adults, in China and the United States, and makes 3 distinct contributions. First, the authors specify which item categories generalize across age and/or cultural groups, rigorously quantifying differences among them. Second, they introduce novel, powerful methods to measure between-group differences in freely generated ranked data, the rank-ordered logit model and Hellinger Affinity. Finally, a broad archive of tested, cross-linguistic stimuli is now freely available to researchers: data, similarity measures, and all stimulus materials for 105 categories and 4 culture-by-age groups, comprising over 10,000 fully translated unique item responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
In this paper, we propose an efficient design method for area optimization in a digital filter. The conventional methods to reduce the number of adders in a filter have the problem of a long critical path delay caused by the deep logic depth of the filter due to adder sharing. Furthermore, there is such a disadvantage that they use the transposed direct form (TDF) filter which needs more registers than those of the direct form (DF) filter. In this paper, we present a hybrid structure of a TDF and DF based on the flattened coefficients method so that it can reduce the number of flip‐flops and full‐adders without additional critical path delay. We also propose a resource sharing method and sharing‐pattern searching algorithm to reduce the number of adders without deepening the logic depth. Simulation results show that the proposed structure can save the number of adders and registers by 22 and 26%, respectively, compared to the best one used in the past. 相似文献
45.
LiNi0.5Mn1.5O4 powder was synthesized via sol-gel method and coated with ZnO in order to test the electrochemical cyclability of the material as a cathode for the secondary Li battery in the 5 V range at 55 °C. The ZnO-coated LiNi0.5Mn1.5O4 powder nearly maintained its initial capacity of 137 mA h g−1 after 50 cycles whereas the uncoated powder was able to retain no more than 10% of the initial capacity after 30 cycles. TEM analysis of the cycled cathodes suggests that the formation of the graphitic surface phase, hindering the Li migration, may be responsible for the rapid capacity loss of the uncoated material while no such phase was observed on the surface of the ZnO coated LiNi0.5Mn1.5O4 powder. 相似文献
46.
J. C. Clark G. G. Ihas M. Reghu C. O. Yoon A. J. Heeger Y. Cao 《Journal of Low Temperature Physics》1995,101(3-4):605-610
Advances in the synthesis of organic conducting polymer systems has increased the electrical conductivity of these systems by several orders of magnitude in the last decade. Several practical applications are envisioned for such systems, but a thorough understanding of the conduction mechanisms and identification of the charge carriers is lacking, making design and implementation for bulk synthesis difficult. In order to clarify our understanding of the electrical properties of these systems, the resistivity and magnetoresistivity of various polymers doped near the metal - insulator transition, such as polyaniline protonated by camphor sulfonic acid (PANi-CSA) and polypyrrole doped with PF6 (PPy-PF6), have been studied down to 25 mK in magnetic fields up to 16 T. 相似文献
47.
The semicontinuous separation/concentration of two solutes with different molecular size by the size exclusion cyclic separation
method is based on the opposite swelling responses of two gels to a temperature change. Experimental results of separation
and concentration of solutes are verified qualitatively by the theoretical models based on the local equilibrium assumption.
Separation of two solutes is shown by the breakthrough curves in coupled gel columns. In closed coupled columns, the volumetric
space for the large molecules which are totally excluded from the gels becomes smaller, creating a concentrating effect as
the gels swell when temperature changes. A mechanistic model is suggested to predict the large molecule concentration to increase
to its solubility limit as cycle repeats. 相似文献
48.
49.
Occlusion of large atrial septal defects with a centering buttoned device: early clinical experience
EB Sideris M Leung JH Yoon CR Chen R Lochan AM Worms C Rey B Meier 《Canadian Metallurgical Quarterly》1996,131(2):356-359
A feasibility clinical study was conducted for the transcatheter occlusion of large ostium secundum atrial septal defects with the centering buttoned device. The centering buttoned device is a modification of the regular buttoned device in which a centering counter-occluder is sutured at the central 40% portion of the occluder. During centering it is stretched, forming a parachute-shaped structure and pulling the occluder over the center of the defect. During buttoning, the counter-occluder forms a double figure eight, opposing the right atrial side of the atrial septum. Occlusion was performed in 12 patients aged 6 to 56 years. All had been rejected for transcatheter occlusion by the regular buttoned device, because of either their defect size or the lack of adequate septal rim. The defect size varied between 23 and 31 mm, and the device size varied between 45 and 60 mm. Nine had immediate effective occlusions of their defects and three residual shunts. One patient with unbuttoning had hemolysis at 2 weeks and underwent surgery. Early results of the transcatheter occlusion of large atrial septal defects are promising, and larger clinical trials are justified. 相似文献
50.
Yeong Joo Lee 《International Journal of Fracture》1992,57(1):25-46
The two-dimensional problem of an edge crack in a half space or plate is considered. The body is loaded by a suddenly applied, spatially uniform normal velocity imposed on the plane boundary of the body on one side of the edge crack. Otherwise, the boundary of the body, including the crack faces, is traction free. Both cases of an initially sharp crack tip and a narrow notch with small but nonzero notch root radius are considered. The material is modeled as elastic viscoplastic, including strain hardening, rate sensitivity and thermal softening. The applied loading produces predominantly mode II loading in the crack tip region. Under these conditions it is possible to nucleate an adiabatic shear band at the crack tip as a precursor to a mode II fracture. On the other hand, because of the rate sensitivity of the material and the high rate of loading, it may be possible under certain conditions to generate tensile stresses in the crack tip region sufficiently large to nucleate brittle tensile fracture. The problem is solved numerically by means of the finite element method in order to investigate the competition between these two possible fracture initiation mechanisms. The magnitude of the impact velocity imposed on the edge of the plate and the notch tip acuity have an effect on processes near the crack tip. For given material, the inception of crack growth is determined by the competition between a stress-based brittle fracture condition, associated with rate sensitivity and strain hardening, and a strain based criterion, associated with high strain rate and thermal softening. 相似文献