全文获取类型
收费全文 | 1279篇 |
免费 | 58篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 386篇 |
金属工艺 | 20篇 |
机械仪表 | 26篇 |
建筑科学 | 57篇 |
矿业工程 | 3篇 |
能源动力 | 41篇 |
轻工业 | 107篇 |
水利工程 | 2篇 |
石油天然气 | 7篇 |
无线电 | 74篇 |
一般工业技术 | 203篇 |
冶金工业 | 191篇 |
原子能技术 | 14篇 |
自动化技术 | 189篇 |
出版年
2023年 | 15篇 |
2022年 | 17篇 |
2021年 | 57篇 |
2020年 | 23篇 |
2019年 | 28篇 |
2018年 | 28篇 |
2017年 | 32篇 |
2016年 | 32篇 |
2015年 | 29篇 |
2014年 | 41篇 |
2013年 | 92篇 |
2012年 | 47篇 |
2011年 | 71篇 |
2010年 | 51篇 |
2009年 | 47篇 |
2008年 | 69篇 |
2007年 | 54篇 |
2006年 | 40篇 |
2005年 | 35篇 |
2004年 | 33篇 |
2003年 | 30篇 |
2002年 | 30篇 |
2001年 | 23篇 |
2000年 | 19篇 |
1999年 | 22篇 |
1998年 | 46篇 |
1997年 | 24篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1977年 | 7篇 |
1976年 | 14篇 |
1975年 | 7篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1970年 | 6篇 |
1966年 | 6篇 |
排序方式: 共有1339条查询结果,搜索用时 15 毫秒
81.
Z. Y. Xie C. H. Wei S. F. Chen S. Y. Jiang J. H. Edgar 《Journal of Electronic Materials》2000,29(4):411-417
The correlation between surface morphological properties of the GaN epilayers and the surface conditions of 6H-SiC (0001)
substrates etched in H2, C2H4/H2, and HCl/H2 was studied. Etching 6H-SiC in H2 produced a high quality surface with steps and terraces, while etching in HCl/H2 produced either a rough surface with many pits and hillocks or a smooth surface similar to that etched in H2, depending on the HCl concentration and temperature. The GaN epilayers were subsequently deposited on these etched substrates
using either a low temperature GaN or a high temperature AlN buffer layer via MOCVD. The substrate surface defects increased
the density and size of the “giant” pinholes (2–4 μm) on GaN epilayers grown on a LT-GaN buffer layer. Small pinholes (<100
nm) were frequently observed on the samples grown on a HT-AlN buffer layer, and their density decreased with the improved
surface quality. The non-uniform GaN nucleation caused by substrate surface defects and the slow growth rate of
planes of the islands were responsible for the formation of “giant” pinholes, while the small pinholes were believed to be
caused by misfit dislocations. 相似文献
82.
Edgar Dutra Zanotto 《Scientometrics》2006,69(1):175-181
Summary In this short paper I propose a combination of qualitative and quantitative criteria to classify the quality, talent and creative
thinking of the scientists of the “hard”, medical and biological sciences. The rationale for the proposed classification is
to focus on the impact and overall achievements of each individual scientist and on how he is perceived by his own community.
This new method is probably more complete than any other form of traditional judgment of a scientist's achievements and reputation,
and may be useful for funding agencies, editors of scientific journals, science academies, universities, and research laboratories. 相似文献
83.
On the matrix cracking stress and the redistribution of internal stresses in brittle-matrix composites 总被引:2,自引:0,他引:2
A concept is proposed to increase the matrix cracking stress of some brittle-matrix composites by taking advantage of the redistribution of internal stresses that occurs when a composite with phases that have dissimilar creep behavior is subjected to thermomechanical loading. The concept is elaborated through the stress analysis of a model unidirectional composite with constituents that exhibit linear viscoelastic behavior. It is shown that if a composite with a matrix that is less creep resistant than the fibers is subjected to a treatment involving both thermal and mechanical loading (e.g. creep test), stresses can be transferred from the matrix to the fibers, resulting in the stress–relaxation of the matrix. Furthermore, it is also shown that by the elastic recovery of the fibers, the matrix can be subjected to large compressive residual stresses at the end of the treatment. The conditions for the viability of this concept and the implications of fiber overloading and potential loss of composite-like behavior are discussed. 相似文献
84.
85.
86.
Adult male Ithomiinae feed at plants containing pyrrolizidine alkaloids. Certain species secrete on hairs of the costal fringe, a specialized organ on their hindwings, a novel -lactone structurally related to the unusual branched-chain acids that are unique to these alkaloids. 相似文献
87.
88.
Albert Kochendoerfer Kunihiko Kobayashi Horst Dieter Schulze Karl Edgar Hagedorn Ulrich Ruediger 《Engineering Fracture Mechanics》1976,8(4):737-741
The flow and fracture stresses, σyg and σfg (δ = crack tip displacement), of sharply notched bending specimens of a structural steel U St 37-1 are measured in the temperature range from full scale to small scale yielding. The best adaption of the experimental results for σfg is obtained by a curve which exhibits an intermediate transition, i.e. which follows in a temperature range between an upper, TtM1 and a lower, Ttl1, transition temperature to the curve σyg(T) for the flow stress with a constant δ = δ1. This transition corresponds to that of the slip to the twin nucleated fracture. Two analyses [3,5] according to the local fracture stress, σf*, concept show that the amount and the temperature dependence of σf* are somewhat different for both methods, but that both exhibit an increase of σf* in the transition range. It is concluded that each transition in the nucleation mode of the fracture is connected with such a transition in the fracture stress. It may, however, become indistinct or even be covered by the scatter of the experimental points. 相似文献
89.
Johnson Edgar M. Cavanagh Raymond C. Spooner Ronald L. Samet Michael G. 《Reliability, IEEE Transactions on》1973,(3):176-183
A normative 2-stage model for incorporating reliability measurements of data-reporting sources in a Bayesian inference system is presented. An experiment required human subjects to make intuitive inferences about two hypotheses on the basis of sample data which were reported with a given reliability. When compared with the optimal model, subjects exhibited systematic errors in estimating the diagnostic impact of less than perfectly reliable data. Their responses reflected the use of specific nonoptimal heuristic strategies to process the information. A utility function was added to the normative model to illustrate how a best choice might be made from among potential data-gathering experiments whose costs increase with their reliabilities. Recommendations for using computer aids to enhance efficiency in inference systems are made 相似文献
90.
The linear-quadratic control problem (LQP) assumes central importance in control theory, and therefore it has been extensively studied in the past decade. This review examines the recent developments related to the LQP, providing a comprehensive coverage for both the lumped and distributed parameter LQP's. The existing theory and practice of the lumped LQP are presented in detail, while the distributed case is considered from a different viewpoint, since its applications and solution techniques are still in a stage of development. The generalized treatment of this subject should prove useful not only to the systems engineer but also the engineer who specializes in other areas of chemical engineering. 相似文献