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   458604篇
  免费   6100篇
  国内免费   2003篇
电工技术   8605篇
综合类   350篇
化学工业   67794篇
金属工艺   18792篇
机械仪表   15290篇
建筑科学   9838篇
矿业工程   2552篇
能源动力   12882篇
轻工业   33858篇
水利工程   4907篇
石油天然气   9469篇
武器工业   55篇
无线电   54344篇
一般工业技术   94900篇
冶金工业   84354篇
原子能技术   11042篇
自动化技术   37675篇
  2021年   4449篇
  2020年   3389篇
  2019年   4318篇
  2018年   7520篇
  2017年   7561篇
  2016年   8128篇
  2015年   5016篇
  2014年   8250篇
  2013年   22670篇
  2012年   13131篇
  2011年   17331篇
  2010年   13911篇
  2009年   15621篇
  2008年   15970篇
  2007年   15708篇
  2006年   14031篇
  2005年   12577篇
  2004年   11889篇
  2003年   11778篇
  2002年   11131篇
  2001年   11021篇
  2000年   10398篇
  1999年   10705篇
  1998年   27109篇
  1997年   18694篇
  1996年   14305篇
  1995年   10680篇
  1994年   9413篇
  1993年   9413篇
  1992年   6811篇
  1991年   6507篇
  1990年   6486篇
  1989年   6139篇
  1988年   5759篇
  1987年   5105篇
  1986年   4985篇
  1985年   5555篇
  1984年   5027篇
  1983年   4584篇
  1982年   4198篇
  1981年   4277篇
  1980年   3969篇
  1979年   3848篇
  1978年   3825篇
  1977年   4370篇
  1976年   5600篇
  1975年   3312篇
  1974年   3102篇
  1973年   3185篇
  1972年   2675篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
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   
32.
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   
33.
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   
34.
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   
35.
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   
36.

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   
37.
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   
38.
Wireless Personal Communications - Multiple inputs multiple outputs (MIMO) is a reliable technique which can manage the increased wireless data traffic in the future generation of wireless...  相似文献   
39.
Multimedia Tools and Applications - Discovering the relevant web services for specific applications in the dynamically changing business world becomes very critical. Researchers have used many...  相似文献   
40.
Mobile Networks and Applications - 5G/6G communication are first generation high speed wireless communication network which integrates the aerial data, terrestrial data and maritime data via...  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