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   314821篇
  免费   6034篇
  国内免费   2226篇
电工技术   6769篇
技术理论   1篇
综合类   2147篇
化学工业   50016篇
金属工艺   13330篇
机械仪表   10380篇
建筑科学   9009篇
矿业工程   2745篇
能源动力   7490篇
轻工业   28378篇
水利工程   3729篇
石油天然气   8842篇
武器工业   222篇
无线电   34221篇
一般工业技术   59837篇
冶金工业   52653篇
原子能技术   7851篇
自动化技术   25461篇
  2021年   3285篇
  2019年   2687篇
  2018年   4507篇
  2017年   4552篇
  2016年   4726篇
  2015年   3569篇
  2014年   5703篇
  2013年   13798篇
  2012年   8684篇
  2011年   11338篇
  2010年   9384篇
  2009年   10392篇
  2008年   10704篇
  2007年   10413篇
  2006年   9353篇
  2005年   8684篇
  2004年   7712篇
  2003年   7308篇
  2002年   7337篇
  2001年   7118篇
  2000年   6787篇
  1999年   6799篇
  1998年   15189篇
  1997年   11437篇
  1996年   8903篇
  1995年   6799篇
  1994年   6165篇
  1993年   5954篇
  1992年   4623篇
  1991年   4522篇
  1990年   4348篇
  1989年   4337篇
  1988年   4302篇
  1987年   3626篇
  1986年   3610篇
  1985年   4168篇
  1984年   3978篇
  1983年   3628篇
  1982年   3430篇
  1981年   3565篇
  1980年   3428篇
  1979年   3367篇
  1978年   3445篇
  1977年   3923篇
  1976年   5037篇
  1975年   3158篇
  1974年   3007篇
  1973年   3024篇
  1972年   2651篇
  1971年   2473篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical...  相似文献   
92.
Journal of Communications Technology and Electronics - Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice...  相似文献   
93.
Power Technology and Engineering - The monitoring of hydraulic structures as high-risk facilities is discussed. Monitoring should ensure the reliability and functioning of a hydraulic structure...  相似文献   
94.
Atomic Energy - The results of calculations and experimental determination of the neutronics characteristics of the IRT-T research reactor are presented. The IRT-T reactor is a pool reactor with...  相似文献   
95.
We deal with the mathematical model of the incremental degradation of the internal coating (e.g. a polymeric material) of a metallic pipe in which a fluid flows relatively fast. The fluid drags solid impurities so that longitudinal scratches, inaccessible to any direct inspection procedure, are produced on the coating. Time evolution of this kind of defects can be reconstructed from the knowledge of a sequence of temperature maps of the external surface. The time-varying orthogonal section of this damaged interface is determined as a function of time and polar angle through the identification of a suitable effective heat transfer coefficient by means of Thin Plate Approximation.  相似文献   
96.
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to...  相似文献   
97.
98.
With excellent specific capacity, superior cycle stability, safety and strong practical, Nb2O5 has been considered as one of the prospective anode materials for lithium-ion batteries (LIBs). However, current study suggests that Nb2O5 electrode materials for LIBs still face the vital issues of low electrical conductivity and poor rate performance. Therefore, carbon-coated TT-Nb2O5 materials are designed and synthesized through solid state method in this work, which present high specific capacity (228 mA h g?1 at 0.2C), satisfactory rate properties (107 mA h g?1 at 20 C). The outstanding electrochemical property can not only give the credit to the pseudocapacitance effect of TT-Nb2O5, but also attribute to introduction of carbon. The homogeneous carbon-coated materials enhance the electrical conductivity, increase the electron transmission speed and alleviate particle crushing. This research not only offers a new method for preparing excellent electrode materials, but also provides a kind of excellent anode material with prospective application for LIBs.  相似文献   
99.
The failure of frontline antibiotics in the clinic is one of the most serious threats to human health and requires a multitude of novel therapeutics and innovative approaches to treatment so as to curtail the growing crisis. In addition to traditional resistance mechanisms resulting in the lack of efficacy of many antibiotics, most chronic and recurring infections are further made tolerant to antibiotic action by the presence of biofilms. Herein, we report an expanded set of 5-benzylidene-4-oxazolidinones that are able to inhibit the formation of Staphylococcus aureus biofilms, disperse preformed biofilms, and, in combination with common antibiotics, are able to significantly reduce the bacterial load in a robust collagen-matrix model of biofilm infection.  相似文献   
100.
Stunting adversely affects physical and mental outcomes of children. It has not been examined whether household air pollution from solid fuel combustion is a risk factor for stunting in children. In a total of 41,439 children aged 6-17 across China, height was measured using a unified protocol. Multivariable linear regression models and logistic regression models were used to assess the associations of solid fuel use for cooking/heating with stunting in children. Adjusted for covariates, cooking/heating with solid fuel was significantly associated with a lower z-score for height for age and sex (β = −0.21 [−0.32 to −0.09] and −0.17 [−0.31 to −0.03], respectively) and an increased risk of stunting with an estimated ORs of 1.34 [1.07~1.68] and 1.37 [1.02~1.83], respectively. The risk of stunting associated with solid fuel use was statistically significant in high-age children. And the effect was greater on girls than on boys, though the difference was not statistically significant. Our study suggested that Chinese children living in households using solid fuel had a significantly higher risk of stunting than those living in households using cleaner fuel.  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