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   1449788篇
  免费   31731篇
  国内免费   9504篇
电工技术   37481篇
技术理论   3篇
综合类   10106篇
化学工业   271654篇
金属工艺   65562篇
机械仪表   42256篇
建筑科学   47838篇
矿业工程   12686篇
能源动力   51313篇
轻工业   103357篇
水利工程   14919篇
石油天然气   39832篇
武器工业   694篇
无线电   198668篇
一般工业技术   271134篇
冶金工业   118431篇
原子能技术   34491篇
自动化技术   170598篇
  2021年   17841篇
  2020年   13521篇
  2019年   15843篇
  2018年   15247篇
  2017年   14541篇
  2016年   21690篇
  2015年   19137篇
  2014年   31000篇
  2013年   90190篇
  2012年   35794篇
  2011年   46514篇
  2010年   43234篇
  2009年   52135篇
  2008年   43827篇
  2007年   40305篇
  2006年   44977篇
  2005年   38735篇
  2004年   40692篇
  2003年   40695篇
  2002年   40168篇
  2001年   36269篇
  2000年   34904篇
  1999年   32999篇
  1998年   30438篇
  1997年   30687篇
  1996年   29932篇
  1995年   27590篇
  1994年   26322篇
  1993年   26166篇
  1992年   25463篇
  1991年   22291篇
  1990年   22720篇
  1989年   21790篇
  1988年   20213篇
  1987年   18608篇
  1986年   17884篇
  1985年   21233篇
  1984年   21837篇
  1983年   19807篇
  1982年   18945篇
  1981年   19001篇
  1980年   17561篇
  1979年   18185篇
  1978年   17432篇
  1977年   16533篇
  1976年   16377篇
  1975年   15758篇
  1974年   15304篇
  1973年   15362篇
  1972年   12846篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
121.
Vieira  Elizabeth S. 《Scientometrics》2022,127(5):2747-2772

It is widely recognised that science in Africa will benefit from international research collaboration (IRC), and therefore studies have been done on IRC in Africa (hereafter: Africa-related IRC research). However, there is no information on the development of Africa-related IRC research, the geographical location of the scientists interested in the topic, the visibility of the literature and the themes researched. This information makes it possible to understand relevant aspects in the context of IRC in Africa, which are useful for identifying IRC strengths, weaknesses and opportunities. It also allows paving the way for future research on this topic. Using discipline–specific terms, bibliometric, and thematic analysis, I collected the literature on Africa-related IRC research indexed in the Web of Science Core Collection (WoS). The results showed that the number of publications on the topic has increased, few African countries have researched the topic, a third of the publications were written exclusively by African scientists, and the topic has high visibility. The panoply of publications revealed that patterns, driving factors, effects, networks, asymmetries, and policies concerning IRC were the main themes researched.

  相似文献   
122.
Marrone  Mauricio  Lemke  Sascha  Kolbe  Lutz M. 《Scientometrics》2022,127(7):3857-3878
Scientometrics - Computer-assisted methods and tools can help researchers automate the coding process of literature reviews and accelerate the literature review process. However, existing...  相似文献   
123.
Chemical and Petroleum Engineering - The hydrodynamics of oxidation towers used for bitumen production were studied using a model tower having transparent walls. Experiments were carried out in two...  相似文献   
124.
Journal of Engineering Physics and Thermophysics - A numerical investigation has been made into the interaction of slender (5–20 calibers) steel cylinder strikers with orthotropic compost...  相似文献   
125.
Journal of Engineering Physics and Thermophysics - Results of investigation into the influence of a corrosion process on thermotechnical characteristics of heat pipes of low-temperature range are...  相似文献   
126.
Deshmukh  P.  Sar  S. K.  Smječanin  N.  Nuhanović  M.  Lalwani  R. 《Radiochemistry》2022,64(4):532-542
Radiochemistry - Magnetically modified waste bark of the Aegle marmelos tree was prepared by using green synthesis method and was used in a batch system for U(VI) removal from aqueous solution. The...  相似文献   
127.
Kamar  M. S.  Shalan  A. S.  Youssef  W. M.  Hussein  A. E. M.  Khawassek  Y. M.  Taha  M. H. 《Radiochemistry》2022,64(2):244-256
Radiochemistry - Ferrugination, sericitization, desulfitization, chloritization, and kaolinitization of hydrothermal origin are the main wall rock alterations occurring within the NNW shear zones...  相似文献   
128.

Modern metrics for evaluating agreement coefficients between the experimental results and expert opinion are compared, and the possibility of using these metrics in experimental research in automatic text processing by machine learning methods is assessed. The choice of Cohen’s kappa coefficient as a measure of expert opinion agreement in the NLP and Text Mining problems is justified. An example of using Cohen’s kappa coefficient for evaluating the level of agreement between the opinion of an expert and the results of ML classification and the measure of agreement of expert opinions in the alignment of sentences of the Kazakh-Russian parallel corpus is given. Based on this analysis, it is proved that Cohen’s kappa coefficient is one of the best statistical methods for determining the level of agreement in experimental studies due to its ease of use, computing simplicity, and high accuracy of the results.

  相似文献   
129.
Bioactive glasses and glass-ceramics (GCs) effectively regenerate bone tissue, however most GCs show improved mechanical properties. In this work, we developed and tested a rarely studied bioactive glass composition (24.4K2O-26.9CaO-46.1SiO2-2.6P2O5 mol%, identified as 45S5-K) with different particle sizes and heating rates to obtain a sintered GC that combines good fracture strength, low elastic modulus, and bioactivity. We analyzed the influence of the sintering processing conditions in the elastic modulus, Vickers microhardness, density, and crystal phase formation in the GC. The best GC shows improved properties compared with its parent glass. This glass achieves a good densification degree with a two-step viscous flow sintering approach and the resulting GC shows as high bioactivity as that of the standard 45S5 Bioglass®. Furthermore, the GC elastic modulus (56 GPa) is relatively low, minimizing stress shielding. Therefore, we unveiled the glass sintering behavior with concurrent crystallization of this complex bioactive glass composition and developed a potential GC for bone regeneration.  相似文献   
130.
This paper reports an investigation on the structure-properties correlation of trivalent metal oxide (Al2O3)-doped V2O5 ceramics synthesized by the melt-quench technique. XRD patterns confirmed a single orthorhombic V2O5 phase formation with increasing strain on the doping of Al2O3 in place of V2O5 in the samples estimated by Williamson-Hall analysis. FTIR and Raman investigations revealed a structural change as [VO5] polyhedra converts into [VO4] polyhedra on the doping of Al2O3 into V2O5. The optical band gap was found in a wide semiconductor range as confirmed by UV–visible spectroscopy analysis. The thermal and conductivity behavior of the prepared samples were studied using thermal gravimetric analysis (TGA) and impedance analyzer, respectively. All the prepared ceramics exhibit good DC conductivity (0.22–0.36 Sm-1) at 400 ?C. These materials can be considered for intermediate temperature solid oxide fuel cell (IT-SOFC)/battery applications due to their good conductivity and good thermal stability.  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