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   2126篇
  免费   142篇
  国内免费   4篇
电工技术   28篇
综合类   2篇
化学工业   465篇
金属工艺   42篇
机械仪表   75篇
建筑科学   109篇
能源动力   164篇
轻工业   375篇
水利工程   14篇
石油天然气   10篇
无线电   125篇
一般工业技术   428篇
冶金工业   73篇
原子能技术   13篇
自动化技术   349篇
  2024年   8篇
  2023年   23篇
  2022年   53篇
  2021年   93篇
  2020年   87篇
  2019年   92篇
  2018年   103篇
  2017年   90篇
  2016年   121篇
  2015年   70篇
  2014年   100篇
  2013年   195篇
  2012年   127篇
  2011年   173篇
  2010年   117篇
  2009年   151篇
  2008年   133篇
  2007年   110篇
  2006年   76篇
  2005年   62篇
  2004年   55篇
  2003年   40篇
  2002年   40篇
  2001年   12篇
  2000年   13篇
  1999年   24篇
  1998年   23篇
  1997年   11篇
  1996年   19篇
  1995年   6篇
  1994年   2篇
  1993年   2篇
  1992年   5篇
  1991年   6篇
  1990年   3篇
  1989年   2篇
  1988年   4篇
  1987年   4篇
  1986年   4篇
  1985年   3篇
  1984年   4篇
  1982年   1篇
  1981年   1篇
  1976年   1篇
  1974年   1篇
  1972年   1篇
  1970年   1篇
排序方式: 共有2272条查询结果,搜索用时 0 毫秒
1.
Uzun  İlhan  Orak  İkram  Yağmur  Hatice Karaer  Karakaplan  Mehmet  Yalman  Murat 《SILICON》2021,13(12):4703-4713
Silicon - 5-(2,4-dichlorophenyl)-2-furoic acid and anthraquinone-2-carboxylic acid were reacted separately with chitin. The synthesized products were characterized by various spectroscopic methods...  相似文献   
2.
3.
4.
Journal of Communications Technology and Electronics - This paper implements mathematically rigorous extended trial function algorithm to address cubic–quartic optical solitons in...  相似文献   
5.
6.
In order to observe the transport ability of peritoneum to small molecular substances, peritoneal equilibration test (PET) was performed in 52 CAPD patients. By analysing the relationship between peritoneal transport function and dialysis adequacy, we found the average urea KT/V and Cr were significantly lower in high and low transport groups (n = 6 and n = 2) than in high average and low average groups (n = 35 and n = 9). According to the results of PET, we adjusted the dialysis program of 11 patients and the dialysis adequacy was markedly improved. We concluded that PET was helpful for selecting and adjusting CAPD program, and discussed some questions which should be payed more attention in PET operation.  相似文献   
7.
8.
Predictions of the discharge and the associated sediment concentration are very useful ingredients in any water resources reservoir design, planning, maintenance, and operation. Although there are many empirical relationships between the discharge and sediment concentration amounts, they need estimation of model parameters. Generally, parameter estimations are achieved through the regression method (RM), which has several restrictive assumptions. Such models are locally valid and their structures and parameter values are questionable from region to others. This paper proposes a new approach for sediment concentration prediction provided that there are measurements of discharge and sediment concentration. The basis of the methodology is a dynamic transitional model between successive time instances based on two variables, namely, discharge and sediment concentration measurements. The transition matrix elements are estimated from the measurements through a special form of the artificial neural networks as perceptrons. The sediment concentration predictions from discharge measurements are achieved through a perceptron Kalman filtering (PKF) technique. In the meantime, this technique also provides temporal predictions. A certain portion of the measurement sequence is employed for the model parameter estimations through training and the remaining part is used for the model verification. Detailed comparisons between RM and PKF approaches are presented and, finally, it is shown that the latter model works dynamically by simulating the observation scatter diagram in the best possible manner with smaller prediction errors. The application of the methodology is performed for the discharge and sediment concentration measurements obtained from the Mississippi River basin at St. Louis, Missouri. It is found that the PKF methodology has smaller average relative, root-mean-square, and absolute errors than RM. Furthermore, graphical representation, such as the scatter and frequency diagrams, indicated that the PKF approach has superiority over the RM.  相似文献   
9.
Since the introduction of warranty provisions in federal highway jobs, more and more state departments of transportation (DOTs) have considered the use of such provisions to protect their initial investment. This paper describes the pros and cons of warranty contracting in highway construction based on a survey of warranty practices in the United States. In particular, the need for state DOTs to buy a warranty for a well-built project is questioned. As an alternative, this paper introduces the warranty option, which gives the DOT the right to buy a warranty only if it becomes necessary at the end of construction. This option is exercised if the performance on site warrants it. This paper describes the mechanics of the warranty option and its advantages over the conventional warranty. A bid evaluation model is also developed for the warranty option approach.  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