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   1519262篇
  免费   25918篇
  国内免费   7080篇
电工技术   35153篇
综合类   6502篇
化学工业   273691篇
金属工艺   66255篇
机械仪表   45020篇
建筑科学   46177篇
矿业工程   11788篇
能源动力   50312篇
轻工业   113476篇
水利工程   15281篇
石油天然气   38383篇
武器工业   162篇
无线电   198524篇
一般工业技术   288810篇
冶金工业   157472篇
原子能技术   34489篇
自动化技术   170765篇
  2021年   15551篇
  2020年   11829篇
  2019年   14608篇
  2018年   18273篇
  2017年   17983篇
  2016年   22391篇
  2015年   17514篇
  2014年   28702篇
  2013年   88003篇
  2012年   36108篇
  2011年   50347篇
  2010年   44925篇
  2009年   53334篇
  2008年   46566篇
  2007年   44426篇
  2006年   44606篇
  2005年   40636篇
  2004年   42068篇
  2003年   41661篇
  2002年   40661篇
  2001年   37019篇
  2000年   35570篇
  1999年   34435篇
  1998年   42363篇
  1997年   37637篇
  1996年   34228篇
  1995年   30098篇
  1994年   28267篇
  1993年   28146篇
  1992年   26101篇
  1991年   23132篇
  1990年   23568篇
  1989年   22651篇
  1988年   21052篇
  1987年   19418篇
  1986年   18786篇
  1985年   22115篇
  1984年   22339篇
  1983年   20285篇
  1982年   19255篇
  1981年   19349篇
  1980年   18005篇
  1979年   18522篇
  1978年   17764篇
  1977年   17590篇
  1976年   18453篇
  1975年   16054篇
  1974年   15581篇
  1973年   15669篇
  1972年   13130篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
A novel dual-rotation bobbin tool friction stir welding (DBT-FSW) was developed, in which the upper shoulder (US) and lower shoulder (LS) have different rotational speeds. This process was tried to weld 3.2 mm thick aluminum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formability. Experimental results show that compared to conventional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process.  相似文献   
262.
Electrospark treatment of OT4-1 titanium alloy was performed sequentially with a STIM-20N hard-alloy electrode (TiC–20% Ni) and carbon-containing material (graphite and carbon-based composite materials). Kinetics of the mass transfer of the hard-alloy electrode was studied. The cathode mass loss during the first minute of the treatment was established. The kinetics results were processed using the methods of mathematical statistics. The erosion resistance of the applied carbon-containing materials was determined. Phase composition and relief of the coatings formed were analyzed. It was found that the application of the carbon-containing material increases the content of refractory phases in the coatings. Increase in the time of the treatment using the carbon-containing materials decreases the roughness of the coatings.  相似文献   
263.
ABSTRACT

In recent times, the applications of multimedia are rising in a greedy mode and hence the amount of video transactions is also increasing exponentially. This has shouted great demands on effective models on video encoding and also for reducing the transmission channel congestion. This research work introduces a managing technique termed weighted encoding for High-Efficiency Video Coding (HEVC). HEVC, also termed as MPEG-H Part 2 and H.265 is a video compression standard that is widely utilized AVC (H.264 or MPEG-4 Part 10). When compared to AVC, HEVC grants double the ratio of data compression at a similar level of quality of the video or considerably enhanced video quality at a similar bit rate. This work intends to optimize the weight that adopted in HEVC for encoding. For this, this paper proposes a new Iterative based propagation update in the water wave Optimization Algorithm (IPU-WWO), which is the improved form of Water wave Optimization (WWO). The performance of proposed IPU-WWO is compared over other conventional methods like Artificial Bee Colony (ABC), Firefly (FF), Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) with respect to Peak Signal to Noise Ratio (PSNR). By doing the encoding process, it minimizes the video size with perceptually better quality video or PSNR.  相似文献   
264.
265.
266.
267.
Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications.  相似文献   
268.
269.
270.
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