首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1309篇
  免费   40篇
  国内免费   4篇
电工技术   56篇
综合类   1篇
化学工业   322篇
金属工艺   25篇
机械仪表   30篇
建筑科学   25篇
能源动力   30篇
轻工业   69篇
水利工程   3篇
石油天然气   1篇
无线电   161篇
一般工业技术   236篇
冶金工业   274篇
原子能技术   33篇
自动化技术   87篇
  2023年   8篇
  2022年   23篇
  2021年   22篇
  2020年   15篇
  2019年   9篇
  2018年   17篇
  2017年   15篇
  2016年   37篇
  2015年   25篇
  2014年   24篇
  2013年   56篇
  2012年   36篇
  2011年   43篇
  2010年   41篇
  2009年   52篇
  2008年   55篇
  2007年   47篇
  2006年   35篇
  2005年   45篇
  2004年   32篇
  2003年   38篇
  2002年   35篇
  2001年   33篇
  2000年   37篇
  1999年   32篇
  1998年   97篇
  1997年   64篇
  1996年   41篇
  1995年   30篇
  1994年   31篇
  1993年   30篇
  1992年   25篇
  1991年   15篇
  1990年   13篇
  1989年   22篇
  1988年   16篇
  1987年   11篇
  1986年   10篇
  1985年   21篇
  1984年   16篇
  1983年   11篇
  1982年   11篇
  1981年   16篇
  1980年   13篇
  1979年   8篇
  1978年   7篇
  1977年   12篇
  1976年   10篇
  1974年   5篇
  1973年   2篇
排序方式: 共有1353条查询结果,搜索用时 15 毫秒
71.
The core structures of 〈c+a〉 dislocations in hexagonal-close-packed (hcp) metals have been investigated by molecular dynamics (MD) simulation using a Lennard-Jones-type pair potential. The 〈c + a〉 edge dislocation has two types of core at 0 K; one is a perfect dislocation (type A), and the other has two 1/2 〈c+a〉 partials (type B). Type A transforms to type B by abruptly increasing temperature from 0 K to 293 K, while type B is stable in temperature range from 0 K to 293 K. In contrast, type A extends parallel to (0001) at 30 K, and this extended core is still stable at 293 K. These results suggest that the 〈c+a〉 edge dislocation glides on the {11 2} as two 1/2 〈c+a〉 partial dislocations and becomes sessile due to changes of the core structure. The 〈c+a〉 screw dislocation spreads over two {10 1} planes at 0 K. The core transforms into a unsymmetrical structure at 293 K, which is spread over {11 2} and {10 1}, and core spreading occurs parallel to {11 2} at 1000 K. A critical strain to move screw dislocations depends on the sense of shear strain. The dependence of the yield stress on the shear direction can be explained in terms of these core structures. This article is based on a presentation made in the symposium entitled “Defect Properties and Mechanical Behavior of HCP Metals and Alloys” at the TMS Annual Meeting, February 11–15, 2001, in New Orleans, Louisiana, under the auspices of the following ASM committees: Materials Science Critical Technology Sector, Structural Materials Division, Electronic, Magnetic & Photonic Materials Division, Chemistry & Physics of Materials Committee, Joint Nuclear Materials Committee, and Titanium Committee.  相似文献   
72.
A noncontact, nonmechanical scanning, wide-field spectral interference microscope is developed for simultaneous measurement of three-dimensional step-height of discontinuous objects and tomographic imaging. A superluminescent diode (SLD) is used as a broadband light source and a liquid-crystal Fabry-Perot interferometer (LC-FPI) as a frequency-scanning device. By means of changing the injection current to the SLD, the spectral profile of the SLD is equalized, and a constant light input to the interferometer is achieved over the entire frequency-scan range. The Fourier-transform technique is used to determine both the amplitude and the phase of spectral fringe signals. Three-dimensional height distribution of a discontinuous object is obtained from the phase information, whereas optically sectioned images of the object are obtained either from the amplitude information alone or from the combination of both the amplitude and phase information. Experimental results with submicrometer resolution are presented for both step-height measurement and tomographic sectioning.  相似文献   
73.
This paper presents calibration of the Vehicle Routing and scheduling Problems with Time Windows-Probabilistic (VRPTW-P) model which takes into account the uncertainty of travel times. Probe vehicle data of travel times were obtained from usual operation of pickup-delivery trucks in South Osaka area. The optimal solution of the VRPTW-P model resulted in reducing total cost, running times and CO2, NOx and Particle Materials (PM) emissions compared with the usual operation. This is attributed to better routing of VRPTW-P to choose more reliable roads. Therefore, VRPTW-P can contribute to establish efficient and environmentally friendly delivery systems in urban area.  相似文献   
74.
A compiler-compiler for visual languages is presented. It has been designed as a framework for building visual programming environments that translate schemas into textual representation as well as into programs representing the deep meaning of schemas. The deep semantics is implemented by applying attribute grammars to schema languages; attribute dependencies are implemented as methods of Java classes. Unlike compiler-compilers of textual languages, a large part of the framework is needed for support of interactive usage of a visual language.  相似文献   
75.
We used the hydrostatic pressure P <1 GPa as a tool to change the c-axis critical current (interlayer coupling) of Bi-2201 and Bi-2212 single crystals. The c-axis critical current drastically increases with pressure (up to 270 % GPa –1 ). The superconducting critical temperature, on the contrary, only slightly increases with a rate of 2-6 % GPa –1 . This implies that the CuO-interlayer coupling has little effect on T c in Bi-compounds.  相似文献   
76.
A full-color twisted-nematic type liquid crystal display (TN-LCD) of 1.4-in diagonal size driven by organic thin-film transistors (TFTs) has been fabricated. This TN-LCD has 80/spl times/80/spl times/3 (RGB) pixel arrays addressed by pentacene TFTs with a channel width of 50 /spl mu/m. The contact resistance between the pentacene film and the source/drain electrodes has been reduced by selecting the exposure condition of the photoresist in patterning the electrodes. In addition, a solution-processed passivation film with a novel structure, consisting of photosensitive polyvinylalcohol and organosiloxane glass resin, has been developed to protect the TFTs against degradation induced by integration with TN-LCD devices. Consequently, it has been confirmed that the organic-TFT-driven TN-LCD fabricated in this paper is capable of displaying full-color moving images at a resolution of 80 pixels per inch.  相似文献   
77.
The biomechanics of medialization laryngoplasty are not well understood. An excised canine larynx model was used to test the effects of various sized silicon implants. The vocal fold length, position, and tension were measured. Medialization laryngoplasty did not affect vocal fold length. At the mid-membranous vocal fold, larger shims resulted in greater medialization and tension. Medialization laryngoplasty neither medialized nor stiffened the vocal process to resist lateralizing forces. We conclude that medialization laryngoplasty provides bulk and support for defects of the membranous region of the vocal fold, but does not appear to close a posterior glottal gap. The selection of a surgical procedure to treat glottal incompetence should take into account the unique biomechanical properties of the anterior (membranous vocal folds) and posterior (cartilaginous portion) glottis.  相似文献   
78.
Chiral tagging reagents, 4-(N,N-dimethylaminosulphonyl)-7-(2-chloroformylpyrrolidin-1 -yl)-2,1,3- benzoxadiazole (R(+)-DBD-Pro-COCl and S(-)-DBD-Pro-COCl), react with mirror image enantiomers of amines to produce corresponding diastereomers in the presence of pyridine as a catalyst. The maximal excitation and emission wavelengths of the resulting diastereomers were ca. 450 nm and 560 nm, respectively. The diastereomers derived from some aliphatic amines were resolved by a reversed-phase chromatography with water-acetonitrile or normal-phase chromatography with n-hexane-ethyl acetate as the eluent. The reactivities of both enantiomers of DBD-Pro-COCl to chiral amines were almost comparable, whereas a slight difference of fluorescence intensity was observed with S(-)-DBD-Pro-COCl. When (S-)-DBD-Pro-COCl was used as the derivatization reagent, amines corresponding to S-configuration were eluted faster than R-configuration. The opposite elution order was obtained with the use of R(+)-DBD-Pro-COCl, instead of S(-)-DBD-Pro-COCl. The Rs values obtained from 1-cyclohexylethylamine (CEA) having aliphatic ring structure was larger than those of amines (1-(1-naphthyl)ethylamine (NEA) and 1-phenylethylamine (PEA)) having aromatic ring structures.  相似文献   
79.
Obese female subjects with binge eating disorder BED; (N = 107) completed the Beck Depression Inventory, Symptom Checklist-90, Inventory of Interpersonal Problems, and Rosenberg Self-Esteem Scale. Subjects were divided into moderate or severe binger on the basis of scores on the Binge Eating Scale, and grouped into moderately or severely obese by performing a median split on their weights. Spearman correlational analyses were performed to determine the relationship between psychopathology and obesity and psychopathology and binge eating. Analyses of variance (ANOVAs) were then performed using scores on the psychological measures with subjects grouped both by severity of obesity and severity of binge eating. The results indicated that in our sample, obesity and scores on the measures of psychiatric symptomatology were unrelated. However, a significant positive relationship was found between binge eating severity and degree of psychiatric symptomatology. We suggest that binge eating may account for the observed relationship between obesity and psychopathology reported in previous studies. We discuss the importance of assessing BED when conducting research with obese individuals.  相似文献   
80.
R 22-DEGDME is chosen as the prime working fluid pair for residential gas-fired absorption heat pumps.The vapour pressures and the heat capacities of mixtures are measured for various concentrations and temperatures and are correlated by a Rankine equation and a polynomial, respectively. The heats of mixing are measured at 10°C, and are correlated by a Redlich-Kister type polynomial.Based on these data, the pressure-temperature-concentration diagram and the enthalpy-concentration diagram are drawn, which make analysis of the absorption cycles possible.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号