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   1484292篇
  免费   25981篇
  国内免费   6986篇
电工技术   34231篇
综合类   6400篇
化学工业   270883篇
金属工艺   63885篇
机械仪表   41321篇
建筑科学   45590篇
矿业工程   11347篇
能源动力   50344篇
轻工业   108922篇
水利工程   14839篇
石油天然气   37443篇
武器工业   132篇
无线电   195728篇
一般工业技术   279881篇
冶金工业   154489篇
原子能技术   33872篇
自动化技术   167952篇
  2021年   16061篇
  2020年   11930篇
  2019年   14687篇
  2018年   15346篇
  2017年   14603篇
  2016年   21144篇
  2015年   17385篇
  2014年   28779篇
  2013年   88084篇
  2012年   34706篇
  2011年   46626篇
  2010年   41999篇
  2009年   50483篇
  2008年   43734篇
  2007年   40602篇
  2006年   43940篇
  2005年   38354篇
  2004年   40794篇
  2003年   40822篇
  2002年   39866篇
  2001年   36724篇
  2000年   35293篇
  1999年   34331篇
  1998年   42470篇
  1997年   37477篇
  1996年   34197篇
  1995年   30080篇
  1994年   28413篇
  1993年   28231篇
  1992年   25929篇
  1991年   23016篇
  1990年   23339篇
  1989年   22404篇
  1988年   20938篇
  1987年   19218篇
  1986年   18594篇
  1985年   21839篇
  1984年   22174篇
  1983年   20148篇
  1982年   19193篇
  1981年   19300篇
  1980年   17885篇
  1979年   18419篇
  1978年   17639篇
  1977年   17309篇
  1976年   18163篇
  1975年   15937篇
  1974年   15438篇
  1973年   15510篇
  1972年   12975篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal.  相似文献   
2.
3.
In this paper, we present a novel memory access reduction scheme (MARS) for two-dimension fast cosine transform (2-D FCT). It targets programmable DSPs with high memory-access latency. It reduces the number of memory accesses by: 1) reducing the number of weighting factors and 2) combining butterflies in vector-radix 2-D FCT pruning diagram from two stages to one stage with an efficient structure. Hardware platform based on general purpose processor is used to verify the effectiveness of the proposed method for vector-radix 2-D FCT pruning implementation. Experimental results validate the benefits of the proposed method with reduced memory access, less clock cycle and fewer memory space compared with the conventional implementation.  相似文献   
4.
5.

Romanian policy makers have to perceive that human intervention on river basins land cover is influencing rainfall-runoff relation and the used methodology cannot accurately estimate watershed surface flow transformations. Global water cycles and energy fluxes understanding is leading to better predictions of land atmosphere interaction and local hydro-climates evolution. The water transfer time determination from rainfall to runoff needs accurate measurements of river basins hydrological parameters. Here, we analyzed and compared the lag time value results of two different methodologies (curve number and rational methodology) used for 54 Romanian small catchment areas study. The focus of this paper is the lag time evaluation and interpretation for an effective implementation of the best methodology approach in the Romanian geographical space. Our research in small river basins was developed using remote sensing technology maps, GIS and environmental datasets in combination with field work on every drainage basin in order to assess the specific morphological features and validate the land cover typology. We found that Soil Conservation Service - Curve Number (SCS-CN) method is widely used according to USA landscape features classification, but not necessarily applicable to Romanian river basins characteristics. Our results show how the official Romanian rational methodology national standard (RNS) can be improved and the limits of SCS-CN method.

  相似文献   
6.
7.
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   
8.
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   
9.
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   
10.
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