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   29210篇
  免费   3044篇
  国内免费   1428篇
电工技术   1911篇
综合类   2041篇
化学工业   4475篇
金属工艺   1605篇
机械仪表   1929篇
建筑科学   2337篇
矿业工程   989篇
能源动力   920篇
轻工业   2213篇
水利工程   602篇
石油天然气   1603篇
武器工业   267篇
无线电   3483篇
一般工业技术   3565篇
冶金工业   1253篇
原子能技术   366篇
自动化技术   4123篇
  2024年   168篇
  2023年   653篇
  2022年   1233篇
  2021年   1710篇
  2020年   1314篇
  2019年   1089篇
  2018年   1117篇
  2017年   1187篇
  2016年   1078篇
  2015年   1558篇
  2014年   1783篇
  2013年   2036篇
  2012年   2125篇
  2011年   2062篇
  2010年   1760篇
  2009年   1705篇
  2008年   1641篇
  2007年   1485篇
  2006年   1423篇
  2005年   1184篇
  2004年   831篇
  2003年   607篇
  2002年   583篇
  2001年   453篇
  2000年   447篇
  1999年   483篇
  1998年   374篇
  1997年   313篇
  1996年   286篇
  1995年   235篇
  1994年   204篇
  1993年   115篇
  1992年   96篇
  1991年   80篇
  1990年   58篇
  1989年   51篇
  1988年   34篇
  1987年   31篇
  1986年   28篇
  1985年   7篇
  1984年   9篇
  1983年   6篇
  1982年   8篇
  1981年   10篇
  1980年   7篇
  1976年   2篇
  1973年   1篇
  1972年   1篇
  1959年   3篇
  1951年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
A CuAlCl4 doped metal organic framework, CuAlCl4@MIL-101, was prepared by introducing CuAlCl4 into the pores of MIL-101 for the selective adsorption of CO over N2. The CuAlCl4 molecules were evenly distributed into various pores sizes and did not change the intrinsic structure of the MIL-101. Isotherms for CO and N2 adsorption at 298 K showed that the CO capacity on CuAlCl4@MIL-101 was much higher than that on virgin MIL-101, whereas the N2 capacity decreased. The selectivity for CO over N2 improved from 4.64 to 31.5 at 298 K and 1 bar. The CuAlCl4@MIL-101 adsorbent displayed outstanding CO adsorption stability and the adsorbent could be regenerated by applying a simple vacuum of 4 mmHg.  相似文献   
962.
结合园林水景多变的状态、多变的感官感受、多变的意境特征,对排比、通感、夸张、引用、比拟五种修辞手法在水景营造中的应用技巧进行了探讨,指出在水景的营造中适宜地运用修辞手法可使水景设计更加合理、动人,从而提高景观品质。  相似文献   
963.
研究并详细讨论了涂料样品制备与样品前处理过程中,各个因素对可溶性Pb、Cr含量测定结果的影响。结果表明:漆膜的厚度、粒径、提取液的酸度、温度等因素对结果的测定有较大的影响,应当对这些因素予以控制以提高实验室间结果一致性。  相似文献   
964.
Novel precipitant prepared through carbonation with MgCl2 wastewater generated from rare earth extraction separation process and low-price dolomite as raw materials was studied in this paper. The purification methods of novel precipitant by adding appropriate oxidizing agent were studied. It was found that optimal purification result could be achieved with sodium hypochlorite as iron removal reagent and the iron removal rate could reach up to 90% when the adding amount was 0.1 vol.%. During the preparation, the particle size and distribution of ceria-based polishing powder were affected obviously by the parameters such as concentration, reaction temperature and feeding rate. The results showed that ceria-based polishing powder with D50 =2.5-3.5 μm and the particle size distribution of 0.65-0.75 μm could be prepared when the concentration of CeCl3 was 0.6 mol/L, the reaction temperature was maintained at 50 °C and the feeding speed was controlled at 25 ml/min. Compared with commercial powder, the self-made polishing powder had roughly the same cutting amount, but the surface finish of polished glass was better than that of commercial polishing powder.  相似文献   
965.
An important issue in low-altitude wind-shear detection is to estimate the wind speed of wind field. In this paper, a novel method for wind speed estimation with airborne phased array radar is proposed by combining space time adaptive processing and compressive sensing. The proposed method is able to achieve accurate wind speed estimate in the condition of limited number of sampling pulses, as demonstrated by numerical examples.  相似文献   
966.
967.
Bioactive glass is considered an ideal material for haemostasis as it releases Ca2+ ions upon hydration, which is required to support thrombosis. In this study the effects of the presence of nanoscaled bioactive glass (n‐BG) in poly(3‐hydroxybutyrate) (P(3HB)) microsphere films on the structural properties, thermal properties and biocompatibility of the films were studied. The n‐BG with a high surface area was also tested for its in vitro haemostatic efficacy and was found to be able to successfully reduce clot detection time. In an effort to study the effect of the roughness induced by the formation of hydroxyapatite on cellular functions such as cell adhesion, cell mobility and cell differentiation, the composite films were immersed in simulated body fluid for periods of 1, 3 and 7 days. From scanning electron microscopy images, the surface of the P(3HB)/n‐BG composite microsphere films appeared fairly uniform and smooth on day 1; however on day 3 and day 7 a rough and uneven surface was observed. The presence of hydroxyapatite on the composite microsphere films on day 3 and day 7 influenced the surface roughness of the films. However, when the P(3HB)/n‐BG composite microsphere films with enhanced surface roughness were tested for biocompatibility, reduced amounts of protein adsorption and cell adhesion were observed. This study thus revealed that there is an optimal surface roughness for the P(3HB) microsphere films for increased cell adhesion, beyond which it could be deleterious for cell adhesion and differentiation. © 2016 Society of Chemical Industry  相似文献   
968.
The interactions of biomass components (hemicellulose, cellulose, and lignin) during co-pyrolysis were investigated in a thermogravimetric analyzer (TGA) as well as a self-designed Macro-TGA with higher heating rate and larger amount of sample. The overlap ratio (OR) was used to evaluate the interaction of biomass components quantitatively. In TGA, the pyrolysis of xylan was not significantly affected by cellulose, whereas the pyrolysis of cellulose was markedly influenced by xylan. The interactions between xylan and lignin were weak with an overlap ratio of 0.9869, whereas co-pyrolysis of cellulose and lignin was strongly inhibited by interactions with the overlap ratio of 0.9737. In Macro-TGA, interactions between components were stronger than that in TGA due to more considerable heat and mass transfer effect.  相似文献   
969.
介绍了爆炸事故的简要经过和设备概况,为分析事故的原因对互感器进行了解体检查,结合解体检查结果,分析互感器设计制造工艺中存在的问题,分析事故原因和事故发展过程,并提出几点建议和预控措施。  相似文献   
970.
杨莉  李猛  季男 《热加工工艺》2012,41(17):196-198
为设计一种ZGMn13堆焊焊条,提出了一种基于RBF神经网络的FeO-MnO渣系焊条配方优化设计方法.利用试验采集的数据对网络进行训练,以加工硬化后的硬度为优化目标,得到最优的焊条配方.试验结果表明:优化后熔敷金属的动载加工硬化性能和静载加工硬化性能良好.  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