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   1580篇
  免费   38篇
  国内免费   9篇
电工技术   132篇
化学工业   413篇
金属工艺   57篇
机械仪表   49篇
建筑科学   45篇
能源动力   67篇
轻工业   153篇
水利工程   3篇
石油天然气   3篇
无线电   97篇
一般工业技术   247篇
冶金工业   157篇
原子能技术   49篇
自动化技术   155篇
  2023年   11篇
  2022年   17篇
  2021年   25篇
  2020年   9篇
  2019年   15篇
  2018年   25篇
  2017年   22篇
  2016年   26篇
  2015年   24篇
  2014年   35篇
  2013年   92篇
  2012年   61篇
  2011年   94篇
  2010年   59篇
  2009年   91篇
  2008年   98篇
  2007年   59篇
  2006年   59篇
  2005年   51篇
  2004年   53篇
  2003年   59篇
  2002年   43篇
  2001年   28篇
  2000年   25篇
  1999年   34篇
  1998年   83篇
  1997年   57篇
  1996年   45篇
  1995年   30篇
  1994年   29篇
  1993年   24篇
  1992年   18篇
  1991年   23篇
  1990年   10篇
  1989年   18篇
  1988年   17篇
  1987年   11篇
  1986年   11篇
  1985年   13篇
  1984年   12篇
  1983年   13篇
  1982年   15篇
  1981年   6篇
  1980年   6篇
  1979年   19篇
  1978年   9篇
  1977年   5篇
  1976年   8篇
  1975年   6篇
  1970年   5篇
排序方式: 共有1627条查询结果,搜索用时 15 毫秒
161.
This study examined the behavioral mechanisms that support transfer of food from adults to infants in tufted capuchins (Cebus apella). Two captive groups of capuchins were presented with abundant quantities of unshelled pecans or commercial pellets. Five of 11 infant subjects could not open the nuts. A variety of tolerated interactions were initiated by infants toward adults, and food was frequently transferred. All such interactions were more frequent with nuts (a preferred food) than with pellets. Adult capuchins were equally tolerant of infant capuchins that could open nuts and those that could not. Tolerated interactions during feeding could result in acquisition of dietary information by young capuchins or to important, if intermittent, nutritional support.  相似文献   
162.
Transformation behaviour with thermal cycling in NiTi alloys   总被引:2,自引:0,他引:2  
The transformation behaviour of NiTi alloys were investigated by differential scanning calorimetry in order to reveal the effects of thermal cycles with the repetition of the transformation. The thermal cycles tend to lower the transformation temperature between the high and low temperature phases and to stabilize the intermediate phase during cooling to result in a two-stage transformation, while the reverse transformation during heating remains a one-stage transformation. Because these effects of the thermal cycles depend on the composition and the deformation, it is thought that defects play an intrinsic role in the complicated behaviour of NiTi alloys.  相似文献   
163.
Effects of residual pores and optical birefringence on transmission through translucent polycrystalline alumina have been studied with the Mie scattering theory. The in-line and total forward transmissions of the translucent polycrystalline alumina were simulated as a function of porosity, pore radius, and grain size. The model revealed that porosity has a significant effect on both the total forward scattering and the in-line transmission, whereas grain size affects only in-line transmission. The calculated transmittance is in good agreement with the experimental values. The in-line transmission gradually increased with a decrease in grain size, and the effect of birefringence on the total forward transmission is negligible in the visible spectrum. The total forward transmission in the visible spectrum is mainly governed by residual pores.  相似文献   
164.
A process of homoepitaxial growth of diamond (111) films by microwave plasma-enhanced chemical vapor deposition has been investigated characterizing areas by ex-situ atomic force microscopy. The evolution of surface morphology during a lateral growth of (111) diamond was visualized utilizing a mesa structure as a marker. Lateral growth forms atomically flat surfaces, which show atomically flat terraces over several hundred nm widths and single bilayer steps of (111) diamond.  相似文献   
165.
166.
167.
A method for evaluating and predicting the performance of a newly developed plate‐type heat exchanger as an evaporator for water‐refrigerant systems such as chillers has been developed. The main component of the developed heat exchanger consists of plates packed together in a casing with winding tubes connected to both sides of the plates. Refrigerant flows inside the tubes, and water flows in the space between the plates. A herringbone‐like pattern is formed in this space by the cross sections of the winding tubes. The newly developed method estimates evaporation performance of the developed heat exchanger using new empirical correlations. There are correlations for heat transfer and pressure drop in winding‐tube banks on the water side, and correlation for the pressure drop on the refrigerant side. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 245–257, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20009  相似文献   
168.
This paper proposes a new advanced fabrication technology for a low-cost integrated-type a-Si solar cell. Integrated-type cells provide many advantages and have been industrialized with a laser patterning method. However, a higher throughput and more efficient patterning method was required for applying a-Si solar cells to a power generating system. Plasma CVM (Chemical Vaporization Machining) was first applied to advanced patterning because of its advantages of high speed and selectivity. In this method, a plasma generated under high pressure localizes near the wire electrode and concentrates reactive radicals. As a result, we achieved an etching rate of more than 1 μm/s and selective patterning of a 200 μm-wide a-Si layer in 1 s multiline patterning was also developed for large-area modules.  相似文献   
169.
Murata T  Ishizawa H  Tanaka A 《Applied optics》2011,50(9):C403-C407
Ghosts and flares are well-known problems that are caused by reflections from lens surfaces when we take photographs. It is more difficult to prevent such stray light in a digital camera than in a film camera because of high reflectance from the low-pass filter and diffraction from the image sensor. To prevent such stray light, we introduce an ultralow refractive index layer into the antireflective (AR) coatings. We used the solgel method to form porous fluoride layers with ultralow refractive indices, and we succeeded in developing a unique process to form AR coatings with superior performance.  相似文献   
170.
Artemisia princeps is commonly used as a food ingredient and in traditional Asian medicine. In this study, we examined the effects of long-term administration of an ethanol extract of A. princeps (APE) on body weight, white adipose tissue, blood glucose, insulin, plasma and hepatic lipids, and adipocytokines in C57BL/6 mice fed a high-fat diet. Daily feeding of a 1% APE diet for 14 weeks normalized elevated body weight, white adipose tissue, and plasma glucose and insulin levels, and delayed impaired glucose tolerance in mice a fed high-fat diet. These events were not observed in mice fed a control diet containing 1% APE. Liver triglyceride and cholesterol levels were similar in mice fed a 1% APE-diet and those fed a control diet. In the high-fat diet groups, APE inhibited hepatic fatty acid synthase (FAS) and suppressed the elevation of plasma leptin, but had no effect on adiponectin levels. These findings suggest that the regulation of leptin secretion by APE may inhibit FAS activity with subsequent suppression of triglyceride accumulation in the liver and adipose tissues. Inhibition of lipid accumulation can, in turn, lead to improvements in impaired glucose tolerance.  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