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   597081篇
  免费   7603篇
  国内免费   1061篇
电工技术   10831篇
综合类   495篇
化学工业   95847篇
金属工艺   23956篇
机械仪表   19137篇
建筑科学   14285篇
矿业工程   4418篇
能源动力   15332篇
轻工业   48196篇
水利工程   7300篇
石油天然气   15061篇
武器工业   42篇
无线电   62376篇
一般工业技术   121222篇
冶金工业   100890篇
原子能技术   14903篇
自动化技术   51454篇
  2021年   6030篇
  2020年   4409篇
  2019年   5814篇
  2018年   9856篇
  2017年   10004篇
  2016年   10548篇
  2015年   6662篇
  2014年   11111篇
  2013年   28199篇
  2012年   17187篇
  2011年   22776篇
  2010年   18351篇
  2009年   20123篇
  2008年   20558篇
  2007年   20247篇
  2006年   17577篇
  2005年   15907篇
  2004年   14994篇
  2003年   14615篇
  2002年   14117篇
  2001年   13427篇
  2000年   12771篇
  1999年   12515篇
  1998年   28204篇
  1997年   20559篇
  1996年   16099篇
  1995年   12486篇
  1994年   11288篇
  1993年   11046篇
  1992年   8723篇
  1991年   8346篇
  1990年   8317篇
  1989年   8082篇
  1988年   7740篇
  1987年   7053篇
  1986年   6797篇
  1985年   7756篇
  1984年   7043篇
  1983年   6697篇
  1982年   6029篇
  1981年   6140篇
  1980年   5852篇
  1979年   5961篇
  1978年   5885篇
  1977年   6376篇
  1976年   7881篇
  1975年   5284篇
  1974年   5066篇
  1973年   5126篇
  1972年   4382篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
The authors have developed a procedure and a test bench for studying evolution of various nature physical fields in modeling geomedium fracture by fluids. The test bench performs synchronous recording of macro- and micro-deformation, heat and acoustic emission induced in physical models of geomedium under loading to discontinuity. The experimental procedure has been trialed. The analysis of the synchronized test data allows a conclusion on the existence of time–space relationship between different nature physical fields induced during failure of solids.  相似文献   
73.
74.
75.
76.
77.
The purpose of present study was to develop and evaluate methods to assess stimulation responses of the lumbar extensors, as part of a longer‐term goal of detecting fatigue during prolonged sitting. Three stimulation frequencies (2, 5, and 8 Hz) were tested in separate stages, which include 3 stimulation trains and 4 sampling blocks. Repeated measures analyses of variance were used to determine whether any significant differences in mean stimulation responses occurred with respect to stimulation frequency, sampling block, and stimulation train. Reliability of measured stimulation responses was assessed within and between sampling blocks using intraclass correlation coefficients. Stimulation frequencies significantly affected the stimulation responses and time‐to‐potentiation differed between the 3 stimulation frequencies; it was highest for 2 Hz stimulation. All 3 stimulation frequencies resulted in excellent reliability within and between sampling blocks. Use of the current protocol at 2 Hz is recommended as appropriate to measure the lumbar extensors status during prolonged sitting.  相似文献   
78.
A technology for slag formation in the ladle–furnace unit is considered; the slag is based on the CaO–SiO2–MgO–Al2O3–B2O3 system. This technology permits both microalloying of the steel with boron (reduced from the oxide phase) and desulfurization of the steel. The resulting boron content in the steel is 0.001–0.008%; the sulfur content in low-alloy steel and pipe steel is low (0.004–0.010%); and the consumption of manganese ferroalloys is reduced to 0.5 kg/t for 08кп steel and 1.4 kg/t for 09Г2C steel. In addition, the proposed technology increases the strength of the rolled steel, without loss in its plasticity; and reduces the environmental impact thanks to the replacement of fluorspar by colemanite.  相似文献   
79.
80.
This study evaluated several physical and sensory parameters of different types of cheese available in the Polish market. The measurements of textural properties were conducted in an Instron universal testing machine, while the colour properties of cheeses were measured using a Minolta chromameter. The chemical composition was determined by means of the near‐infrared spectroscopy (NIRs). Moreover, a trained sensory panel was invited to assess the cheese texture‐related properties. Generally, cheeses with reduced fat content were characterised by higher hardness, adhesiveness, cohesiveness and elasticity. Texture‐related parameters of cheese with canola oil were comparable to that of most of full‐fat cheeses. The correlation analysis between physical and sensory attributes related to cheese textural properties indicated the potential applications of TPA, shear and penetration tests (= 0.766, = 0.75 and = 0.765, respectively) for the evaluation of sensory properties related to the hardness. Meanwhile, the elasticity of cheese obtained from sensory evaluation was strongly correlated with the elasticity determined from the shear test (= 0.722) and moderately correlated with the elasticity from penetration test (= 0.588), indicating a need to refine the method of penetration test. In addition, cheeses exhibited higher meltability during convection heating at 230 °C than microwave heating. The values of meltability for cheese with reduced fat content were lower than those of full‐fat cheese.  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