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   1455802篇
  免费   25606篇
  国内免费   6960篇
电工技术   34067篇
综合类   6335篇
化学工业   268312篇
金属工艺   63508篇
机械仪表   40635篇
建筑科学   45033篇
矿业工程   11313篇
能源动力   50125篇
轻工业   105753篇
水利工程   14517篇
石油天然气   37384篇
武器工业   128篇
无线电   194531篇
一般工业技术   274735篇
冶金工业   141557篇
原子能技术   33847篇
自动化技术   166588篇
  2021年   15456篇
  2020年   11743篇
  2019年   14503篇
  2018年   14522篇
  2017年   13741篇
  2016年   20646篇
  2015年   17161篇
  2014年   28529篇
  2013年   87510篇
  2012年   33871篇
  2011年   45342篇
  2010年   41178篇
  2009年   49980篇
  2008年   42724篇
  2007年   39665篇
  2006年   43419篇
  2005年   37922篇
  2004年   40341篇
  2003年   40298篇
  2002年   39595篇
  2001年   36022篇
  2000年   34740篇
  1999年   33402篇
  1998年   37900篇
  1997年   34965篇
  1996年   32603篇
  1995年   29130篇
  1994年   27500篇
  1993年   27390篇
  1992年   25681篇
  1991年   22720篇
  1990年   23124篇
  1989年   22184篇
  1988年   20670篇
  1987年   19057篇
  1986年   18308篇
  1985年   21690篇
  1984年   22065篇
  1983年   20044篇
  1982年   19075篇
  1981年   19186篇
  1980年   17789篇
  1979年   18370篇
  1978年   17614篇
  1977年   17128篇
  1976年   17593篇
  1975年   15910篇
  1974年   15428篇
  1973年   15525篇
  1972年   12997篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
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   
33.
34.
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   
35.
Poor aqueous solubility is one of the recurrent drawbacks of many compounds in medicinal chemistry. To overcome this limitation, the dilution of drug candidates from stock solutions of an organic solvent is common practice. However, the precise characterisation of these compounds in aqueous solutions is often neglected, leading to some uncertainties regarding the nature of the actual active species. In this communication, we demonstrate that two ruthenium complexes previously reported by our group for their chemotherapeutic potential against cancer, namely [Ru(DIP)2(sq)](PF6) and [Ru(DIP)2(3-methoxysq)](PF6), where DIP is 4,7-diphenyl-1,10-phenanthroline, sq=semiquinonate and 3-methoxysq=3-methoxysemiquinonate, form colloids in water-DMSO (1 % v/v) mixtures that are invisible to the naked eyes. [Ru(DIP)2(3-methoxysq)](PF6) was found to form a highly stable and monodispersed colloid with nanoaggregates of ∼25 nm. In contrast, [Ru(DIP)2(sq)](PF6) was found to form large reticulates of mostly spherical aggregates which size was found to increase over time. The difference in size and shape distribution of drug candidates is of tremendous significance as the study of their biological activity might be severely affected. Overall, we strongly believe that these observations should be taken into account by the scientific community working on the development of metal-based drugs with poor water solubility.  相似文献   
36.
37.
This study aimed to evaluate the physicochemical characteristics and sensory attributes of beef burgers with the addition of pea fibre as a partial substitute of meat or fat. Three formulations were prepared: control (CON) – similar to the commercial formulation; fibre/less meat (FLM)—5% meat reduction and addition of 1% pea fibre; fibre/less fat (FLF)—7% fat reduction and addition of 1% pea fibre. Non-significant differences were obtained for pH, colour parameters (L* and b*), texture profile, cooking loss and size reduction among formulations. Moreover, sensory analysis with consumers of beef burgers did not indicate differences among the formulations for all the analysed attributes. Therefore, pea fibre is a promising partial replacer for meat and fat in beef burgers due to the preservation of technological parameters and sensory acceptance.  相似文献   
38.
39.
The role of the following factors in the selection of technological bases for manufacturing is considered: the accessibility of the machined surfaces; their parameters and dimensional relationships; their position relative to the forces acting; and the uniformity of the margin distribution.  相似文献   
40.
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