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   436121篇
  免费   6456篇
  国内免费   1368篇
电工技术   8038篇
综合类   364篇
化学工业   63926篇
金属工艺   16827篇
机械仪表   12907篇
建筑科学   10996篇
矿业工程   2150篇
能源动力   11796篇
轻工业   36952篇
水利工程   4315篇
石油天然气   6722篇
武器工业   23篇
无线电   54251篇
一般工业技术   87034篇
冶金工业   82177篇
原子能技术   9398篇
自动化技术   36069篇
  2021年   3795篇
  2020年   2835篇
  2019年   3503篇
  2018年   5933篇
  2017年   6069篇
  2016年   6301篇
  2015年   4269篇
  2014年   7071篇
  2013年   20244篇
  2012年   11114篇
  2011年   15207篇
  2010年   12321篇
  2009年   13849篇
  2008年   14521篇
  2007年   14436篇
  2006年   12522篇
  2005年   11260篇
  2004年   10835篇
  2003年   10956篇
  2002年   10135篇
  2001年   10606篇
  2000年   10007篇
  1999年   10539篇
  1998年   26517篇
  1997年   18644篇
  1996年   14478篇
  1995年   10715篇
  1994年   9641篇
  1993年   9455篇
  1992年   6931篇
  1991年   6657篇
  1990年   6368篇
  1989年   6231篇
  1988年   6040篇
  1987年   5103篇
  1986年   4970篇
  1985年   5650篇
  1984年   5202篇
  1983年   4953篇
  1982年   4521篇
  1981年   4566篇
  1980年   4322篇
  1979年   4230篇
  1978年   4032篇
  1977年   4770篇
  1976年   6495篇
  1975年   3474篇
  1974年   3347篇
  1973年   3305篇
  1972年   2774篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
The germline carrier of the BRCA1 pathogenic mutation has been well proven to confer an increased risk of breast and ovarian cancer. Despite BRCA1 biallelic pathogenic mutations being extremely rare, they have been reported to be embryonically lethal or to cause Fanconi anemia (FA). Here we describe a patient who was a 48-year-old female identified with biallelic pathogenic mutations of the BRCA1 gene, with no or very subtle FA-features. She was diagnosed with ovarian cancer and breast cancer at the ages of 43 and 44 and had a strong family history of breast and gynecological cancers.  相似文献   
43.
Jori  Popat K.  Jadhav  Vrushali H. 《Catalysis Letters》2022,152(6):1703-1710
Catalysis Letters - A new zirconium based carbonaceous solid acid catalyst Zr@CC-PA with both Lewis and Bronsted acidic sites was prepared by simultaneous carbonization and phosphonation of glucose...  相似文献   
44.
Fischer-Tropsch synthesis of the CO2 in biogas aims at producing light hydrocarbons and increasing its calorific value for feeding into the grid. Fe catalysts with Mn and K as promoters are supposed to yield high amounts of light hydrocarbons. Using a Fe-Mn-K/MgO catalyst, a parameter screening and long-term experiments were carried out. The catalyst shows, within the examined range, the highest selectivity to C2–C4 hydrocarbons at 450 °C, 8 bar(a), and a gas hourly space velocity of 350 h−1. Calcination of the catalyst resulted in a significant drop of activity and an almost complete loss of selectivity to hydrocarbons. Admixture of steam to the reactant gas lowers the tendency to carbon deposition but also promotes the water-gas shift reaction and results in lower yields of hydrocarbons.  相似文献   
45.
Journal of Machinery Manufacture and Reliability - The problem of calculating the reliability and fatigue life of machine parts by the fatigue failure under random changes in the actual and limit...  相似文献   
46.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations.  相似文献   
47.
Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food...  相似文献   
48.
ABSTRACT

Bacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.  相似文献   
49.
50.
Topics in Catalysis - In this work, a simple thermal-catalytic system was used to valorize peanut shells (Arachis hypogaea), the residual biomass from the peanut industry. To accomplish this...  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