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   147306篇
  免费   10891篇
  国内免费   5143篇
电工技术   7379篇
技术理论   15篇
综合类   8145篇
化学工业   25220篇
金属工艺   7334篇
机械仪表   8379篇
建筑科学   10282篇
矿业工程   3836篇
能源动力   4354篇
轻工业   8894篇
水利工程   2172篇
石油天然气   7165篇
武器工业   843篇
无线电   19589篇
一般工业技术   19448篇
冶金工业   8640篇
原子能技术   1638篇
自动化技术   20007篇
  2024年   466篇
  2023年   2150篇
  2022年   3702篇
  2021年   5081篇
  2020年   3884篇
  2019年   3391篇
  2018年   3888篇
  2017年   4318篇
  2016年   3805篇
  2015年   4938篇
  2014年   6367篇
  2013年   8500篇
  2012年   8654篇
  2011年   9557篇
  2010年   8152篇
  2009年   8080篇
  2008年   8127篇
  2007年   7551篇
  2006年   7681篇
  2005年   6687篇
  2004年   4832篇
  2003年   4416篇
  2002年   4275篇
  2001年   3950篇
  2000年   3717篇
  1999年   4110篇
  1998年   3943篇
  1997年   3279篇
  1996年   2904篇
  1995年   2402篇
  1994年   1964篇
  1993年   1571篇
  1992年   1229篇
  1991年   971篇
  1990年   844篇
  1989年   715篇
  1988年   562篇
  1987年   451篇
  1986年   328篇
  1985年   310篇
  1984年   219篇
  1983年   155篇
  1982年   160篇
  1981年   122篇
  1980年   130篇
  1979年   85篇
  1978年   90篇
  1977年   90篇
  1976年   123篇
  1975年   60篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
132.
133.
134.
User Modeling and User-Adapted Interaction - Personality plays a pivotal role at work. Many scholars have investigated the association between personality and language usage habits in the English...  相似文献   
135.
Microsystem Technologies - Recently, nonlinear system identification has received increasingly more attention due to its promising applications in engineering fields. It has become a challenging...  相似文献   
136.
Sustainable biocomposites have gained considerable interest as an alternative to conventional composites in recent years due to their cost-effectiveness and environmental friendliness. The aim of this study was to investigate the performance and durability behavior of biocomposites from sustainable biocarbon (BC) as compared to conventional established fillers. The poly(butylene terephthalate) (PBT) and its composites reinforced with BC, talc, and glass fiber (GF) were prepared and the durability performances was investigated. The study showed that BC/PBT biocomposites provided a lighter weight alternative to traditionally used fillers. After undergoes thermo-oxidative aging, the mechanical properties of BC/PBT biocomposite were deteriorated. The GF/PBT showed the most stable in retaining its mechanical properties in comparison to the talc/PBT and BC/PBT. The aging behavior and mechanism of the PBT composites were discussed. This study provides further insight on the durability-related properties progression of biocomposites as compared to traditional used fillers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47722.  相似文献   
137.
The Caputo and Caputo–Fabrizio derivative are applied to study a second‐grade nanofluid over a vertical plate. A comparative analysis is presented to study the unsteady free convection of a second‐grade nanofluid with a new time–space fractional heat conduction. The governing equations with mixed time–space fractional derivatives are non‐dimensionalized and solved numerically, and a comparison between the Caputo and the Caputo–Fabrizio models is made. It is found that the temperature is higher for the Caputo–Fabrizio fractional model than the Caputo model, but the higher velocity only exists near the vertical plate for the Caputo–Fabrizio model than the Caputo model. Moreover, the velocity for the Caputo model will exceed the Caputo–Fabrizio model as y evolves.  相似文献   
138.
Abstract

The reabsorption characteristics of the lignite treated by low and high temperature drying process were addressed in the paper. The information about the moisture form, functional groups, effective water-filled porosities and equilibrium moisture content of the lignite before and after the drying process was investigated using Differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and a self-made reabsorption device, respectively. The results show that the low drying temperature (140, 190, 230?°C, 10?min, N2) has little impact on the effective water-filled porosities of the resulted samples, whereas it has a great influence on the main oxygen-containing functional groups, which amount firstly decreases and then increases with the drying temperature increasing. In the case of the lignite samples dried under high-temperature (600, 700, 800?°C, 30?s, N2), the amount of the effective water-filled porosity of the sample decreases and the amount of oxygen-containing functional groups increases as the temperature increasing. The reabsorption capability of the high temperature dried sample is much lower than that of the sample treated under low drying temperature. The reabsorption characteristics of the low-temperature dried samples are affected by the amount of the oxygen-containing functional groups, while the effective water-filled porosity is main factor for the lignite samples derived from high temperature drying process. Moreover, the work gives a good evidence that the high-temperature drying process is an effective choose for lignite upgrading.  相似文献   
139.
With the continuous development of the Internet of Things technology and the proposal of “Made in China 2025”, the construction of IoT applicat  相似文献   
140.
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