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   557000篇
  免费   10012篇
  国内免费   1498篇
电工技术   9800篇
综合类   552篇
化学工业   84806篇
金属工艺   20532篇
机械仪表   15810篇
建筑科学   13742篇
矿业工程   2333篇
能源动力   15265篇
轻工业   51495篇
水利工程   5488篇
石油天然气   9442篇
武器工业   41篇
无线电   61930篇
一般工业技术   107300篇
冶金工业   111015篇
原子能技术   10715篇
自动化技术   48244篇
  2022年   3543篇
  2021年   5704篇
  2020年   4175篇
  2019年   5193篇
  2018年   9033篇
  2017年   8879篇
  2016年   9264篇
  2015年   6456篇
  2014年   10403篇
  2013年   26399篇
  2012年   16624篇
  2011年   22015篇
  2010年   17261篇
  2009年   18992篇
  2008年   19594篇
  2007年   19066篇
  2006年   16494篇
  2005年   15035篇
  2004年   14383篇
  2003年   14079篇
  2002年   13211篇
  2001年   13180篇
  2000年   12210篇
  1999年   12998篇
  1998年   35101篇
  1997年   24268篇
  1996年   18355篇
  1995年   13606篇
  1994年   11780篇
  1993年   11430篇
  1992年   8070篇
  1991年   7593篇
  1990年   7436篇
  1989年   7176篇
  1988年   6623篇
  1987年   5893篇
  1986年   5813篇
  1985年   6425篇
  1984年   6034篇
  1983年   5276篇
  1982年   5028篇
  1981年   5093篇
  1980年   4822篇
  1979年   4702篇
  1978年   4492篇
  1977年   5491篇
  1976年   7284篇
  1975年   3870篇
  1974年   3601篇
  1973年   3726篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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   
42.
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   
43.
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   
44.
The present study reports for the first time the performance of silver phosphate (Ag3PO4) microcrystals as photocatalyst (degradation of Rodamine B-RhB) and antifungal agent (against Candida albicansC. albicans) under visible-light irradiation (455 nm). Ag3PO4 microcrystals were synthesized by a simple co-precipitation (CP) method at room temperature. The structural and electronic properties of the as-synthetized Ag3PO4 have been investigated before and after 4 cycles of RhB degradation under visible light using X-ray diffraction (XRD), micro-Raman spectroscopy, UV–Vis spectrophotometer and field emission scanning electron microscopy (FE-SEM) images. The antifungal activity was analyzed in planktonic cells and 48h-biofilm of C. albicans by colony forming units (CFU) counting, confocal laser and FE-SE microscopies. Statistical analysis was carried out using SPSS software. Morphological and structural modifications of Ag3PO4 were observed upon recycling. After 4 recycles, the material maintained its photodegradation property; an eightfold increase in the efficiency of Ag3PO4 was observed in planktonic cells and a two fold increase in biofilm when irradiated under visible light. Thus, higher antifungal effectiveness against C. albicans was obtained when associated with visible-light irradiation.  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.
Multimedia Tools and Applications - The design of robots capable of operating autonomously in changing and unstructured environments, requires using complex software architectures in which,...  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.
With lower alloying cost and higher mechanical properties, lean duplex stainless steels can be an alternative to the more commonly used austenitic stainless steels. However, these alloys are still not the preferred choice, probably due to a lack of field experience. A study was thus initiated in view of defining the limits of use of selected (lean) duplexes for urban wastewater treatment units. The present paper shows the localized corrosion performance of selected lean duplexes in chloride contaminated solutions. The results are compared with austenitic S30403 and S31603 and with the more standard duplexes S82441 and S32205. The effect of welding was also investigated. Exposures in field municipal wastewater plants were conducted for 1 year in low and high chloride content units. The results show that lean duplexes S32101 and S32202 can be used as alternatives to S30403 and S31603 in low chloride electrolytes. At 500 ppm of chloride content, duplex stainless steel S32304 showed better corrosion resistance than S30403 and S31603. For higher chloride contents (1000 ppm and above) the standard duplexes S82441 and S32205 shall be preferred.  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