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   691347篇
  免费   9962篇
  国内免费   1805篇
电工技术   12571篇
综合类   754篇
化学工业   106363篇
金属工艺   26221篇
机械仪表   20277篇
建筑科学   16646篇
矿业工程   3369篇
能源动力   17972篇
轻工业   63303篇
水利工程   6978篇
石油天然气   12629篇
武器工业   68篇
无线电   76307篇
一般工业技术   131579篇
冶金工业   136614篇
原子能技术   14367篇
自动化技术   57096篇
  2021年   6249篇
  2020年   4489篇
  2019年   5843篇
  2018年   9909篇
  2017年   9693篇
  2016年   10282篇
  2015年   6999篇
  2014年   11659篇
  2013年   31218篇
  2012年   18515篇
  2011年   25400篇
  2010年   20058篇
  2009年   22425篇
  2008年   22979篇
  2007年   22824篇
  2006年   20065篇
  2005年   18224篇
  2004年   17495篇
  2003年   17155篇
  2002年   16461篇
  2001年   16431篇
  2000年   15412篇
  1999年   16143篇
  1998年   41393篇
  1997年   28964篇
  1996年   22193篇
  1995年   16762篇
  1994年   14636篇
  1993年   14295篇
  1992年   10462篇
  1991年   9742篇
  1990年   9831篇
  1989年   9500篇
  1988年   8900篇
  1987年   7922篇
  1986年   7835篇
  1985年   8820篇
  1984年   8286篇
  1983年   7376篇
  1982年   6972篇
  1981年   7084篇
  1980年   6770篇
  1979年   6556篇
  1978年   6430篇
  1977年   7576篇
  1976年   9927篇
  1975年   5612篇
  1974年   5273篇
  1973年   5441篇
  1972年   4497篇
排序方式: 共有10000条查询结果,搜索用时 187 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.
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   
43.
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   
44.
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   
45.
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   
46.
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   
47.
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   
48.
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   
49.
Journal of Materials Science - For transformers and inductors to meet the world’s growing demand for electrical power, more efficient soft magnetic materials with high saturation magnetic...  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