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   1555793篇
  免费   26020篇
  国内免费   7047篇
电工技术   35175篇
综合类   6444篇
化学工业   275094篇
金属工艺   65885篇
机械仪表   45629篇
建筑科学   47226篇
矿业工程   11832篇
能源动力   50400篇
轻工业   118155篇
水利工程   15832篇
石油天然气   38358篇
武器工业   147篇
无线电   199206篇
一般工业技术   294368篇
冶金工业   178266篇
原子能技术   34622篇
自动化技术   172221篇
  2021年   15560篇
  2020年   11870篇
  2019年   14652篇
  2018年   18496篇
  2017年   18293篇
  2016年   22631篇
  2015年   17513篇
  2014年   28640篇
  2013年   87914篇
  2012年   37203篇
  2011年   51884篇
  2010年   45340篇
  2009年   53323篇
  2008年   47730篇
  2007年   45590篇
  2006年   45783篇
  2005年   41624篇
  2004年   42933篇
  2003年   42622篇
  2002年   41424篇
  2001年   37968篇
  2000年   36334篇
  1999年   35448篇
  1998年   49173篇
  1997年   41940篇
  1996年   37005篇
  1995年   31750篇
  1994年   29571篇
  1993年   29407篇
  1992年   26442篇
  1991年   23604篇
  1990年   23952篇
  1989年   23040篇
  1988年   21543篇
  1987年   19791篇
  1986年   19150篇
  1985年   22499篇
  1984年   22488篇
  1983年   20481篇
  1982年   19386篇
  1981年   19458篇
  1980年   18097篇
  1979年   18610篇
  1978年   17840篇
  1977年   17798篇
  1976年   18961篇
  1975年   16091篇
  1974年   15567篇
  1973年   15682篇
  1972年   13147篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
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   
13.
14.
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   
15.
16.
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   
17.
18.
At the hydroelectric unit No. 11 of the Nizhnekamsk hydroelectric power plant, the filling wedges of a rotor were investigated by ultrasound in the free st  相似文献   
19.
Abstract

Lung deposited surface area (LDSA) is a relatively new metric that has been argued to be more accurate at predicting health effects from aerosol exposure. For typical atmospheric aerosol, the LDSA concentration depends mainly on the concentration of ultrafine particles (e.g. vehicular exhaust emissions and residential wood combustion) and therefore optical methods cannot be used to measure and quantify it. The objective of this study was to investigate and describe typical characteristics of LDSA under different urban environments and evaluate how a diffusion charging-based Pegasor AQ Urban sensor (Pegasor Ltd., Finland) can be used as an alternative to optical sensors when assessing local combustion emissions and respective LDSA concentrations. Long-term (12?months) sensor measurements of LDSA were carried out at three distinctly different measurement sites (four sensor nodes) in the Helsinki metropolitan area, Finland. The sites were affected mainly by vehicular exhaust emission (street canyon and urban background stations) and by residential wood combustion (two detached housing area stations). The results showed that the accuracy of the AQ Urban was good (R2 = 0.90) for the measurement of LDSA when compared to differential mobility particle sizer. The mean concentrations of LDSA were more than twice as high at the street canyon (mean 22 µm2 cm?3) site when compared to the urban background site (mean 9.4 µm2 cm?3). In the detached housing area, the mean concentrations were 12 µm2 cm?3, and wood combustion typically caused high LDSA peaks in the evenings. High correlations and similar diurnal cycles were observed for the LDSA and black carbon at street canyon and urban background stations. The utilization of a small-scale sensor network (four nodes) showed that the cross-station variability in hourly LDSA concentrations was significant in every site, even within the same detached housing area (distance between the two sites ~670?m).  相似文献   
20.
Journal of Communications Technology and Electronics - Abstract—The article presents a rigorous numerical solution, using the Wiener–Hopf method, to the problem of plane wave...  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