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   264222篇
  免费   17239篇
  国内免费   9060篇
电工技术   12714篇
技术理论   13篇
综合类   14001篇
化学工业   41040篇
金属工艺   14744篇
机械仪表   14457篇
建筑科学   16252篇
矿业工程   6117篇
能源动力   6488篇
轻工业   16245篇
水利工程   4694篇
石油天然气   11371篇
武器工业   1459篇
无线电   30829篇
一般工业技术   37427篇
冶金工业   11408篇
原子能技术   2214篇
自动化技术   49048篇
  2024年   950篇
  2023年   3559篇
  2022年   6639篇
  2021年   8867篇
  2020年   6668篇
  2019年   5260篇
  2018年   19531篇
  2017年   19325篇
  2016年   15392篇
  2015年   8473篇
  2014年   9977篇
  2013年   11793篇
  2012年   15609篇
  2011年   22299篇
  2010年   19181篇
  2009年   15924篇
  2008年   16657篇
  2007年   16866篇
  2006年   9675篇
  2005年   9319篇
  2004年   6510篇
  2003年   5705篇
  2002年   4619篇
  2001年   3793篇
  2000年   3783篇
  1999年   4277篇
  1998年   3561篇
  1997年   3013篇
  1996年   2827篇
  1995年   2243篇
  1994年   1841篇
  1993年   1315篇
  1992年   1062篇
  1991年   813篇
  1990年   574篇
  1989年   471篇
  1988年   376篇
  1987年   254篇
  1986年   211篇
  1985年   131篇
  1984年   116篇
  1983年   86篇
  1982年   86篇
  1981年   68篇
  1980年   67篇
  1968年   43篇
  1966年   42篇
  1965年   45篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
杨文光 《辐射防护》1995,15(1):59-63,41
本文介绍一种新型高压直流电源,它的输出高压的提升、下降均自动、无级、缓慢地变化,无突变现象,尤其在电网供电突然中断时,也能使用高压自动、缓慢地下降到0。它用于半导体放射性射线探测器,可以避免由于操作的粗心或电网供电突然中继引起高压快速变化或而产生的对该类昂贵探测器及其附件的损害,使探测器的优良性能得以保持。  相似文献   
102.
PC/ABS合金的研制及其在汽车上的应用   总被引:6,自引:0,他引:6  
对PC/ABS合金开发和研制及其在汽车上的应用作了评述。介绍了上海杰事公司在该领域的进展。  相似文献   
103.
Stiffness of subchondral proximal tibial trabecular bone is a factor in the stability of prostheses implanted into that bone. The stiffness of trabecular bone in osteoarthritis (OA) has been documented. Trabecular bone in rheumatoid arthritis (RA) is osteopenic in numerous sites and morphologically abnormal in the proximal tibia. Reliable data on proximal tibial bone in RA are lacking, although 1 study failed to identify abnormalities. The purposes of this study were (1) to document the stiffness of the proximal tibial cancellous bone in patients with RA, (2) to determine the effect of angular deformity on bone stiffness in rheumatoid patients, and (3) to compare RA stiffness values with those in published reports for OA. Fifteen tibial plateau were obtained from patients with RA during surgery. Each plateau was horizontally seated in a mold and covered with cement. The plateau was divided into 6 regions, which were used to facilitate comparison between specimens and the existing literature. Indentation tests were conducted with a 4-mm-diameter cylindrical indentor controlled by an MTS machine. The indentor descended at a rate of 2 mm/min to a maximum depth of 1.0 mm; load and displacement data were digitally recorded. Stiffness was calculated from the slope of the linear region of the curve using best-fit linear regression. Where varus deformity was present, stiffness in the medial plateau was higher overall than for the other compartment; whereas in the case of valgus deformity, stiffness of the lateral side was significantly higher (P < .05 for each observation). In comparison to older normal specimens, both the medial compartment of the varus RA specimens (P < .01) and the posterolateral compartment of the valgus RA specimens (P < .01) had significantly lower stiffness. Comparison with OA specimens showed that in varus RA, the posteromedial region had significantly lower stiffness than in varus OA at the same site (P < .01). In valgus RA, the lateral region had significantly lower stiffness than in valgus OA at the same site (P < .01). The mean stiffness ratio of the valgus RA was significantly (P < .01) altered from normal, and for the varus RA, it was significantly (P < .01) different from normal posteriorly. The stiffness ratios for the varus RA were significantly (P < .01) different from those for varus OA; there was no difference between valgus RA and valgus OA. It is concluded that RA affected bone has significantly lower stiffness than normal and osteoarthritic bone. The loaded plateau is stiffer than the unloaded plateau in angular deformity, but is still less stiff than normal bone and osteoarthritic plateaus with corresponding deformities.  相似文献   
104.
以月潭水库上游面止水铜片修复为例,具体介绍了混凝土重力坝止水铜片缺陷产生的原因、修复方案、质量控制等,修复后达到了良好的效果,其方案可行,质量可靠,可以为其他类似工程提供借鉴。  相似文献   
105.
Yang  Chao  Ding  Yijie  Meng  Qiaozhen  Tang  Jijun  Guo  Fei 《Neural computing & applications》2021,33(17):11387-11399
Neural Computing and Applications - RNA-binding proteins play an important role in the biological process. However, the traditional experiment technology to predict RNA-binding residues is...  相似文献   
106.
107.
Many video service sites headed by YouTube know what content requires copyright protection. However, they lack a copyright protection system that automatically distinguishes whether uploaded videos contain legal or illegal content. Existing protection techniques use content-based retrieval methods that compare the features of video. However, if the video encoding has changed in resolution, bit-rate or codec, these techniques do not perform well. Thus, this paper proposes a novel video matching algorithm even if the type of encoding has changed. We also suggest an intelligent copyright protection system using the proposed algorithm. This can serve to automatically prevent the uploading of illegal content. The proposed method has represented the accuracy of 97% with searching algorithm in video-matching experiments and 98.62% with automation algorithm in copyright-protection experiments. Therefore, this system could form a core technology that identifies illegal content and automatically excludes access to illegal content by many video service sites.  相似文献   
108.
In this paper we have proposed a dynamic pricing scheme for the contributing peers in the Video on Demand (VoD) system. The scheme provides an effective mechanism to maximize the profit through the residual resources of the contributing peers. A utilization function is executed for each contributing peer to estimate the utility factor based on the parameters such as initial setup cost, holding cost, chaining cost and salvage cost. In this paper, we urge an effective dynamic pricing algorithm that efficiently utilizes a range of parameters with a varying degree of complexity. The key findings of the algorithm are (i) each contributing peers are benefitted by the monetary based on its resource contributions to the VoD system and (ii) a high degree of social optimum is established by proficiently aggregating the contributing peer’s resources with the overall resources of the VoD system. We validate our claim by simulating the proposed dynamic pricing scheme with other standard pricing schemes such as altruism, cost model and game theory perspective. The result of our dynamic pricing scheme shows the best utility factor than other standard pricing schemes.  相似文献   
109.
This paper utilizes the adaptive technique to design a class of active synchronizing masterslave large scale systems against imperfect actuators and networked interconnections with bias faults and signal attenuations, respectively. Without the requirement of knowledge of eventual faulty factors of bias-actuators on systems, and attenuation factors of connected networks, an adaptive mechanism is designed to estimate each unknown faulty factor on-line for constructing a class of distributed adaptive controllers. Then based on the adaptive adjustment parameters and Lyapunov stability theory, Lyapunov functions are addressed to prove that the proposed adaptive master-slave large-scale system can be guaranteed to be asymptotic synchronization with the improper actuator and faulty transmitted signals. Finally, a multiple vehicle large-scale system is used to verify the efficiency of the method.  相似文献   
110.
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