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   636856篇
  免费   8918篇
  国内免费   1577篇
电工技术   11257篇
综合类   608篇
化学工业   96149篇
金属工艺   26315篇
机械仪表   19068篇
建筑科学   14784篇
矿业工程   3676篇
能源动力   16242篇
轻工业   52449篇
水利工程   7162篇
石油天然气   14938篇
武器工业   43篇
无线电   69237篇
一般工业技术   127314篇
冶金工业   122320篇
原子能技术   14894篇
自动化技术   50895篇
  2021年   5846篇
  2020年   4271篇
  2019年   5525篇
  2018年   9635篇
  2017年   9499篇
  2016年   9997篇
  2015年   6628篇
  2014年   11102篇
  2013年   28307篇
  2012年   17293篇
  2011年   23555篇
  2010年   18612篇
  2009年   20878篇
  2008年   21244篇
  2007年   20905篇
  2006年   18181篇
  2005年   16707篇
  2004年   16033篇
  2003年   15735篇
  2002年   14984篇
  2001年   15165篇
  2000年   14147篇
  1999年   14702篇
  1998年   37430篇
  1997年   26275篇
  1996年   20020篇
  1995年   15017篇
  1994年   13079篇
  1993年   12860篇
  1992年   9418篇
  1991年   8962篇
  1990年   8910篇
  1989年   8592篇
  1988年   8069篇
  1987年   7267篇
  1986年   7175篇
  1985年   7822篇
  1984年   7387篇
  1983年   6637篇
  1982年   6274篇
  1981年   6458篇
  1980年   6151篇
  1979年   6157篇
  1978年   6108篇
  1977年   7011篇
  1976年   9189篇
  1975年   5398篇
  1974年   5165篇
  1973年   5300篇
  1972年   4488篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
Journal of Materials Science: Materials in Electronics - Nano Mn0.95M0.05S (M ≡ Cu, Mg) samples were produced using molten salt solid state reaction method. Rietveld analysis of X-ray...  相似文献   
42.
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   
43.
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   
44.
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   
45.
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   
46.
Russian Engineering Research - The modernization of manufacturing by the comprehensive application of digital technology—in both production and management—is considered. Principles are...  相似文献   
47.
Russian Engineering Research - The stability of robot-mower motion in a specific direction is considered. The direction is regulated by means of an angular sensor and a programmable controller...  相似文献   
48.
Revin  A. A.  Mikhaylova  A. M.  Konakov  A. A.  Tsyplenkov  V. V.  Shastin  V. N. 《Semiconductors》2021,55(12):879-884
Semiconductors - The wave functions of electrons localized at P, As, and Sb shallow donors in Ge are calculated in the envelope function approximation taking into account valley–orbit...  相似文献   
49.
This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging.  相似文献   
50.
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   
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