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   866篇
  免费   21篇
  国内免费   8篇
电工技术   50篇
综合类   4篇
化学工业   256篇
金属工艺   33篇
机械仪表   27篇
建筑科学   20篇
矿业工程   1篇
能源动力   45篇
轻工业   69篇
无线电   51篇
一般工业技术   159篇
冶金工业   30篇
原子能技术   52篇
自动化技术   98篇
  2022年   4篇
  2021年   9篇
  2019年   10篇
  2018年   16篇
  2017年   10篇
  2016年   14篇
  2015年   15篇
  2014年   13篇
  2013年   46篇
  2012年   40篇
  2011年   61篇
  2010年   29篇
  2009年   33篇
  2008年   41篇
  2007年   35篇
  2006年   42篇
  2005年   40篇
  2004年   28篇
  2003年   29篇
  2002年   25篇
  2001年   18篇
  2000年   18篇
  1999年   29篇
  1998年   14篇
  1997年   18篇
  1996年   16篇
  1995年   12篇
  1994年   17篇
  1993年   12篇
  1992年   7篇
  1991年   19篇
  1990年   9篇
  1989年   9篇
  1988年   4篇
  1987年   11篇
  1986年   17篇
  1985年   13篇
  1984年   18篇
  1983年   11篇
  1982年   11篇
  1981年   11篇
  1980年   6篇
  1979年   15篇
  1978年   13篇
  1977年   8篇
  1976年   7篇
  1974年   2篇
  1973年   2篇
  1963年   1篇
  1957年   1篇
排序方式: 共有895条查询结果,搜索用时 15 毫秒
101.
Water-insoluble powder is often dispersed in shells of commercial soft capsules for various reasons, but little reports have been published about the effect of powder addition on the physical properties of the gelatin gel. Glass powder, titanium oxide, calcium carbonate and γ-orizanol were used as model of powder. Changes of Young modulus obtained from the tensile test showed that any powder addition to the gelatin sheet made the gelatin sheet hard not by the surface effect of powder but by the volumetric effect of it. In this test, any powders had no effect on the tensile strength of the gelatin sheet because there was little interaction between each powder and the gelatin gel in the break point. The limiting strain was decreased a little up to the specific amount of each powder and then beyond the specific amount that decreased steeply in the case of glass powder and γ-orizanol. There might be a suitable range of the amount of powder for the gelatin sheet to keep the plastic flow similar to the gelatin sheet containing no powder. In this work, it was shown that the physical properties of the gelatin shell would be regulated by powder addition to the gelatin sheet.  相似文献   
102.
Plastic magnets were prepared using commercial polyamide (Nylon 12), polystyrene and ethylene-vinylacetate copolymer, and three kinds of ferrite magnetic powders with different concentration levels (20, 35 and 50 vol%). Their magnetic properties and thermal stability are discussed comparing viscoelasticity and thermal properties of the polymers and plastic magnets. Magnetic properties of the anisotropic plastic magnets were largely dependent on the concentration of the magnetic powder and its degree of orientation in the matrix. The degree of the orientation was mainly affected by the interaction between polymer matrix and magnetic powder, and viscoelastic property of the matrix polymer. It was also affected to some extent by the shape of the magnetic particles. The order of the interaction of the polymers to the magnetic powders was as follows: PA > EVA copolymer > PS, and PA-bonded magnets gave the highest magnetic properties among the matrices examined. The decrease in magnetic properties due to the change in the orientation of magnetic powder rarely occurred during thermal treatment.  相似文献   
103.
A new annealing method which drastically reduces the coercivity of GaGe-garnet films grown by LPE has been developed. The as-grown films of (YSmLuCa)3(FeGe)5O12 and (YEuTmCa)3(FeGe)5 O12 are sealed with Y2O3 and metal Ca in an evacuated tube having three chambers. When heated, the tube is filled with Ca and O2 gases which are supplied from the metal Ca and Y2O3, respectively. Ca and oxygen are believed to be incorporated into the film occupying the dodecahedral cation vacancies and oxygen vacancies, respectively. By this annealing, coercivities higher than 5.0 Oe are drastically reduced to less than 0.5 Oe. At the same time, the 4πMs and lattice constant af are decreased, while the Curie temperature Tc is increased. A point defect structure model containing c-site vacancies, oxygen vacancies and a-site Ge2+ ions is proposed. The origin of the coercivity is believed to be the oxygen vacancies.  相似文献   
104.
105.
Integral-skin foams of rigid polyurethane are sandwich structures consisting of a core layer of closed cells enclosed in rigid surface layers on both sides. We examined the layer composition of integral-skin foam with the objective of maximum flexural strength, and then studied possibilities of reconciling the strength and thermal insulating properties in housings for evaporators in car air conditioners; i.e., unit cases. This examination showed that the most practical density range (250 ≦ ρpall ≦ 500 kg/m3) provides vibratile resistance and thermal insulating properties. In actual car-running tests, a maximum 0.1 MPa stress was generated on unit cases with overall densities of 350 kg/m3, We found this to be 0.4% of the flexural strength of an integral-skin foam and 2% of the fatigue strength. In the forcible vibratile test, a stress of 0.5 to 1.0 MPa was generated at the resonance point of a unit case with 250 to 500 kg/m3 overall density. We found that these values are 2 to 5% of integral-skin foam's flexural strength and 10 to 25% of its fatigue strength. These values are of the same level as the conventional unit case made of polypropylene blended with talc. An integral-skin foam with an overall density of 250 kg/m3, nearly equal to half the weight of polypropylene, has the same level of resistance to vibration.  相似文献   
106.
The additivity of flicker responses produced by two different wavelengths λ1 and λ2 was investigated for five adapting levels of 560 nm by the summation-index method. A summation-index value of σ of 0.30 was obtained for all conditions employed, confirming the linear property of the achromatic channel. The additivity of unique chromatic responses, red, yellow, green, and blue, was also investigated with the same method. In this case the wavelengths λ1 and λ2 were chosen in a spectral region to produce one of the four unique colors and the summation index was measured for the color with the cancellation method. A summation index of 0.30 was found for the green and blue sensations and also for the red sensation if both stimuli were from the same spectral region. A slight additivity failure of the enhancement type was found for pairs λ1 and λ2 λ1 was in the short-wavelength region while λ2 was in the long-wavelength region. An additivity failure of the same type was found for the yellow chromatic sensation when λ2 was 607 nm and λ1 was 570, 550, or 533 nm, the last combination giving a summation index of as much as 0.64. The results imply the existence of two different cones whose responses do not add linearly to yield the yellow sensation.  相似文献   
107.
The mean stress effect on the fatigue properties of two kinds of welded pipes was investigated in cantilever bending. The fatigue strength changed with the mean stress on fillet welded pipes, but did not change on butt welded pipes. The fatigue crack initiated from the toe of weld on the outer surface of fillet welded pipes and from the undercut on the inner surface of butt welded pipes. The measurement of the fatigue crack propagation rate and the residual stress distribution through the thickness of pipe revealed that the difference in the fatigue properties between fillet and butt welded pipes arose from the weld-induced residual stress, tension on the inner surface and compression on the outer surface. It is suggested that the production of compressive residual stress along the inner surface would be an effective means for improving the fatigue strength of butt welded pipes.  相似文献   
108.
109.
110.
Area-based image matching and sub-pixel displacement estimation using similarity measures are common methods that are used in various fields. Sub-pixel estimation using parabola fitting over three points with their similarity measures is also a common method to increase the matching resolution. However, few investigations or studies have explored the characteristics of this estimation.This study analyzed sub-pixel estimation error using two different types of matching model. Our analysis demonstrates that the estimation contains a systematic error depending on image characteristics, the similarity function, and the fitting function. This error causes some inherently problematic phenomena such as the so-called pixel-locking effect, by which the estimated positions tend to be biased toward integer values. We also show that there are good combinations of the similarity functions and fitting functions.In addition, we propose a new algorithm to greatly reduce sub-pixel estimation error. This method is independent of the similarity measure and the fitting function. Moreover, it is quite simple to implement. The advantage of our novel method is confirmed through experiments using different types of images.  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