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   563665篇
  免费   7220篇
  国内免费   996篇
电工技术   10470篇
综合类   468篇
化学工业   88008篇
金属工艺   23370篇
机械仪表   18486篇
建筑科学   12526篇
矿业工程   4312篇
能源动力   14512篇
轻工业   45359篇
水利工程   6958篇
石油天然气   14917篇
武器工业   39篇
无线电   60277篇
一般工业技术   116355篇
冶金工业   95576篇
原子能技术   14695篇
自动化技术   45553篇
  2021年   5564篇
  2020年   4129篇
  2019年   5414篇
  2018年   9368篇
  2017年   9562篇
  2016年   9984篇
  2015年   6102篇
  2014年   10382篇
  2013年   26286篇
  2012年   15890篇
  2011年   21196篇
  2010年   17043篇
  2009年   18872篇
  2008年   19093篇
  2007年   18778篇
  2006年   16298篇
  2005年   14748篇
  2004年   14013篇
  2003年   13693篇
  2002年   13247篇
  2001年   12850篇
  2000年   12330篇
  1999年   12010篇
  1998年   27648篇
  1997年   19978篇
  1996年   14980篇
  1995年   11911篇
  1994年   10750篇
  1993年   10506篇
  1992年   8237篇
  1991年   8019篇
  1990年   7937篇
  1989年   7672篇
  1988年   7386篇
  1987年   6658篇
  1986年   6458篇
  1985年   7328篇
  1984年   6640篇
  1983年   6358篇
  1982年   5716篇
  1981年   5845篇
  1980年   5587篇
  1979年   5689篇
  1978年   5634篇
  1977年   6149篇
  1976年   7654篇
  1975年   5070篇
  1974年   4868篇
  1973年   4943篇
  1972年   4256篇
排序方式: 共有10000条查询结果,搜索用时 922 毫秒
81.
Abstract

An eco-friendly catalyst system was synthesized using three step reaction. The Cu nanoparticles bridged aminoclay catalyst was analyzed using various analytical techniques. The structure of the catalyst was confirmed by FTIR and XRD. The synthesized catalyst system was used for the reduction of p-nitrophenol (NP), Cr(VI), and fluorescein (Flur) dye individually, as well as in their mixture forms. The kapp value was computed to access the efficiency of the catalyst. The results indicated that the kapp value of the individual system is higher than that of the mixture systems due to the absence of the complex formation reaction. The catalytic performance of the catalyst was also tested for the Schiff base (SB) formation between poly(ethyleneglycol) (PEG) and aniline (ANI) in an oxygen atmosphere. The 1H-NMR spectroscopy result indicates that the present catalyst system produced 86% yield.  相似文献   
82.
In the future, hydrogen will be an important energy carrier and industrial raw material. Catalytic steam reforming of bio-oils is a promising and economically viable technology for hydrogen production. However, during the reforming process, the catalysts are rapidly deactivated due to coke formation and sintering. Thus, maintaining the activity and stability of catalysts is the key issue in this process. Optimized operation conditions could extend the catalyst lifetime by affecting the coke morphology or promoting coke gasification. This article summarizes the recent developments in the field of catalytic steam reforming of bio-oils, focusing on the operation conditions, the properties of the catalysts, and the effects of the catalyst supports. The expected insights into the catalytic steam reforming of bio-oils will provide further guidance for hydrogen production from bio-oils.  相似文献   
83.
Theoretical Foundations of Chemical Engineering - The development of a thermostable hydrophobic platinum catalyst is an important scientific and practical problem. The purpose of this work is to...  相似文献   
84.
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with...  相似文献   
85.
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   
86.
The bromodomain and extra terminal (BET) family of bromodomain-containing proteins (BCPs) have been the subject of extensive research over the past decade, resulting in a plethora of high-quality chemical probes for their tandem bromodomains. In turn, these chemical probes have helped reveal the profound biological role of the BET bromodomains and their role in disease, ultimately leading to a number of molecules in active clinical development. However, the BET subfamily represents just 8/61 of the known human bromodomains, and attention has now expanded to the biological role of the remaining 53 non-BET bromodomains. Rapid growth of this research area has been accompanied by a greater understanding of the requirements for an effective bromodomain chemical probe and has led to a number of new non-BET bromodomain chemical probes being developed. Advances since December 2015 are discussed, highlighting the strengths/caveats of each molecule, and the value they add toward validating the non-BET bromodomains as tractable therapeutic targets.  相似文献   
87.
Metal Science and Heat Treatment - The structure, the strength characteristics and the impact toughness at different temperatures up to –100°C of tubular billets from steel 35 are...  相似文献   
88.
Traditionally, in supervised machine learning, (a significant) part of the available data (usually 50%-80%) is used for training and the rest—for validation. In many problems, however, the data are highly imbalanced in regard to different classes or does not have good coverage of the feasible data space which, in turn, creates problems in validation and usage phase. In this paper, we propose a technique for synthesizing feasible and likely data to help balance the classes as well as to boost the performance in terms of confusion matrix as well as overall. The idea, in a nutshell, is to synthesize data samples in close vicinity to the actual data samples specifically for the less represented (minority) classes. This has also implications to the so-called fairness of machine learning. In this paper, we propose a specific method for synthesizing data in a way to balance the classes and boost the performance, especially of the minority classes. It is generic and can be applied to different base algorithms, for example, support vector machines, k-nearest neighbour classifiers deep neural, rule-based classifiers, decision trees, and so forth. The results demonstrated that (a) a significantly more balanced (and fair) classification results can be achieved and (b) that the overall performance as well as the performance per class measured by confusion matrix can be boosted. In addition, this approach can be very valuable for the cases when the number of actual available labelled data is small which itself is one of the problems of the contemporary machine learning.  相似文献   
89.
Russian Journal of Non-Ferrous Metals - Rolling bearing rings comprise a large reserve for expanding powder metallurgy production. This reserve is being incompletely implemented. The hot forging of...  相似文献   
90.
Journal of Communications Technology and Electronics - Abstract—The two-dimensional diffraction problem of a plane polarized TM-wave on two identical solid silver nanocylinders is considered....  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