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   625092篇
  免费   23024篇
  国内免费   10188篇
电工技术   19864篇
技术理论   24篇
综合类   14430篇
化学工业   97918篇
金属工艺   29029篇
机械仪表   27858篇
建筑科学   25610篇
矿业工程   9556篇
能源动力   17797篇
轻工业   41646篇
水利工程   7786篇
石油天然气   24262篇
武器工业   1664篇
无线电   73306篇
一般工业技术   108732篇
冶金工业   87036篇
原子能技术   11383篇
自动化技术   60403篇
  2023年   4311篇
  2022年   8775篇
  2021年   12718篇
  2020年   9765篇
  2019年   9581篇
  2018年   12937篇
  2017年   13777篇
  2016年   13448篇
  2015年   13022篇
  2014年   18184篇
  2013年   32974篇
  2012年   25409篇
  2011年   30453篇
  2010年   25357篇
  2009年   26133篇
  2008年   26162篇
  2007年   25387篇
  2006年   24523篇
  2005年   21676篇
  2004年   17577篇
  2003年   16463篇
  2002年   15135篇
  2001年   14483篇
  2000年   14446篇
  1999年   15829篇
  1998年   29534篇
  1997年   21001篇
  1996年   16853篇
  1995年   12896篇
  1994年   11078篇
  1993年   10257篇
  1992年   7538篇
  1991年   6847篇
  1990年   6560篇
  1989年   6015篇
  1988年   5552篇
  1987年   4736篇
  1986年   4560篇
  1985年   4992篇
  1984年   4544篇
  1983年   4081篇
  1982年   3766篇
  1981年   3818篇
  1980年   3491篇
  1979年   3361篇
  1978年   3355篇
  1977年   3766篇
  1976年   4875篇
  1975年   2857篇
  1973年   2737篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
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   
72.
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   
73.

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   
74.
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   
75.
In this study, C/SiOC and C/SiO2 composites were prepared by using carbonaceous microspheres with different surface functional groups. Carbonaceous microspheres based on hydrothermal reaction of glucose contains hydroxyl group, while the surface carboxyl group increases after NaOH etching. The hydroxyl group increases the oxygen-enriched structural units of SiOC ceramics, and the C spheres are closely enwrapped in SiOC matrix after pyrolysis at 900 °C. However, the interfacial reaction of surface carboxyl with Si–OH results in the formation of cristobalite SiO2, and C spheres are not only encased inside the SiOC matrix, but also dispersed outside of SiOC ceramics. After removal of C via calcination at 500 °C for 5 h, C/SiOC and C/SiO2 composites are transformed into amorphous SiO2 and cristobalite SiO2, respectively. The thermogravimetric analysis indicates the oxidation resistance of SiOC is superior to that of C and SiO2.  相似文献   
76.
Nowadays, oil pollution has become more serious, which causes great threats both to the ecological environment and human life. In this study, a novel type of multifunctional deacetylated cellulose acetate/polyurethane (d-MCA:MTPU) composite nanofiber membranes for oil/water separation are successfully fabricated by electrospinning, which show super-amphiphilicity in air, super-hydrophilicity in oil, and oleophobicity in water. All the d-MCA:MTPU composite nanofiber membranes with different mass ratios can be used as water-removing, oil-removing, and emulsion separation substance only by gravity driving force. The highest separation flux for water and oil reaches up to 37 000 and 74 000 L m−2 h−1, respectively, and all the separation efficiencies are more than 99%. They have outstanding comprehensive mechanics performance, which can be controlled by simply adjusting the mass ratios. They show excellent antifouling and self-cleaning ability, endowing powerful cyclic stability and reusability. Those results show that d-MCA:MTPU composite nanofiber membranes have great application prospects in oil/water separation.  相似文献   
77.
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   
78.
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   
79.
Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of...  相似文献   
80.
Crosslinking of polyolefin elastomer (POE, ENGAGE™ 8480) with Dicumyl Peroxide (DCP) can have effects on its crystallization dynamics, crystal structure, and properties. The POE crosslinked uniformly has significantly lower crystalline ability than the one with only amorphous phase crosslinked, which, in turn, has weaker crystalline ability than neat POE. The crystallinity and melting point depend on how the POE is crosslinked. The neat POE and POE crosslinked in amorphous phase only, are investigated with DSC and in-situ tensile/synchrotron radiation (WAXD/SAXS). In situ tensile/synchrotron X-ray during a uniaxial stretching process indicates that severe crystal fragmentation is observed at a strain around 45%, and with further increase in strain. The stress in the crosslinked POE is significantly larger than neat POE. For both samples, crystal orientation increases sharply within the strain range up to 88% where orientation-induced new crystals aligned in stretching direction are observed. The long period increases more in stretching direction for the crosslinked POE, consistent with larger stress in this sample, and the stress difference is more pronounced at large strains (27.3 vs. 10.9 MPa at a strain 435%). Permanent set of the crosslinked POE is smaller, consistent with less oriented crystals observed after the test for permanent set.  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