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   474045篇
  免费   50600篇
  国内免费   37627篇
电工技术   34520篇
技术理论   37篇
综合类   40150篇
化学工业   81905篇
金属工艺   23177篇
机械仪表   27422篇
建筑科学   40341篇
矿业工程   16610篇
能源动力   15404篇
轻工业   33286篇
水利工程   13908篇
石油天然气   18249篇
武器工业   5722篇
无线电   52258篇
一般工业技术   48925篇
冶金工业   17838篇
原子能技术   5712篇
自动化技术   86808篇
  2024年   1530篇
  2023年   7025篇
  2022年   11796篇
  2021年   16824篇
  2020年   15637篇
  2019年   13230篇
  2018年   12099篇
  2017年   15655篇
  2016年   18109篇
  2015年   20231篇
  2014年   28053篇
  2013年   29465篇
  2012年   34508篇
  2011年   39573篇
  2010年   29095篇
  2009年   29783篇
  2008年   29058篇
  2007年   33663篇
  2006年   30820篇
  2005年   26707篇
  2004年   22407篇
  2003年   18826篇
  2002年   15098篇
  2001年   11625篇
  2000年   9940篇
  1999年   8050篇
  1998年   6198篇
  1997年   5145篇
  1996年   4269篇
  1995年   3480篇
  1994年   3049篇
  1993年   2252篇
  1992年   1798篇
  1991年   1349篇
  1990年   1131篇
  1989年   947篇
  1988年   616篇
  1987年   445篇
  1986年   421篇
  1985年   453篇
  1984年   356篇
  1983年   295篇
  1982年   303篇
  1981年   199篇
  1980年   210篇
  1979年   95篇
  1978年   48篇
  1977年   67篇
  1976年   40篇
  1959年   47篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
991.
Human facial gestures often exhibit such natural stochastic variations as how often the eyes blink, how often the eyebrows and the nose twitch, and how the head moves while speaking. The stochastic movements of facial features are key ingredients for generating convincing facial expressions. Although such small variations have been simulated using noise functions in many graphics applications, modulating noise functions to match natural variations induced from the affective states and the personality of characters is difficult and not intuitive. We present a technique for generating subtle expressive facial gestures (facial expressions and head motion) semi‐automatically from motion capture data. Our approach is based on Markov random fields that are simulated in two levels. In the lower level, the coordinated movements of facial features are captured, parameterized, and transferred to synthetic faces using basis shapes. The upper level represents independent stochastic behavior of facial features. The experimental results show that our system generates expressive facial gestures synchronized with input speech.  相似文献   
992.
CaCu3Ti4O12 electroceramic was prepared by a microwave assisted solid-state reaction technique from CaCO3, CuO and TiO2 powders. Processing involved the preparation of raw material, mixing and milling, calcination, pellet forming and sintering processes. Conventional furnace and microwave assisted sintering processes were employed in order to improve phase structures, morphology and dielectric properties of CaCu3Ti4O12 ceramics. Surface and fracture FESEM analysis showed that the microwave assisted sintered CaCu3Ti4O12 produced better densification and more uniform grain size compared to the conventional sintered sample.  相似文献   
993.
The potential of the vibro-milling technique as a simple method to obtain usable quantities of single-phase electroceramic powders with nanosized particles was examined. A detailed study considering the role of both milling time and firing condition on phase formation and particle size of the final product was performed. The calcination temperature for the formation of the desired phase was lower when longer milling times have been applied. More importantly, by employing an appropriate choice of the milling time and calcination condition, high purity electroceramic nanopowders have been successfully prepared with a simple solid-state reaction method.  相似文献   
994.
Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca3Al2O6 (C3A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C3A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density.  相似文献   
995.
Some approximate solutions for predicting the stress intensity factor of a short crack penetrating an inclusion of arbitrary shape have been developed under mode I and mode II loading conditions. The derivation of the fundamental formula is based on the transformation toughening theory. The transformation strains in the inclusion are induced by the crack-tip field and remotely applied stresses, and approximately evaluated by the Eshelby equivalent inclusion theory. As validated by detailed finite element (FE) analyses, the developed solutions have good accuracy for different inclusion shape and for a wide range of modulus ratio between inclusion and matrix material.  相似文献   
996.
基于MAPINFO和VB的自来水管网信息系统的建立   总被引:2,自引:0,他引:2  
叶巧云 《地矿测绘》2003,19(1):25-26,30
介绍基于MapInfo平台,利用VB语言进行二次开发,建立自来水管网地理信息系统的关键技术及其注意的问题。  相似文献   
997.
面块切片是一种新的三维数据显示、解释方法,将它应用于安棚油田地震资料解释中和BBT油田识别小断层中。与常规解释方法相比,不仅大大提高了地震资料的解释效率,而且在识别小断层和小构造方面效果明显。  相似文献   
998.
胡平 《南方金属》2003,(2):9-12
通过对飞剪剪切长度,精度,剪刃间隙和压板机构等参数的优化,来提高钢板的剪切质量。  相似文献   
999.
The current study prospectively followed girls with attention-deficit/hyperactivity disorder (ADHD), along with a matched comparison sample, 5 years after childhood neuropsychological assessments. Follow-up neuropsychological measures emphasized attentional skills, executive functions, and language abilities. Paralleling childhood findings, the childhood-diagnosed ADHD group displayed moderate to large deficits in executive/attentional performance as well as in rapid naming relative to the comparison group at follow up (Mage 14.2 years). ADHD-inattentive versus ADHD-combined contrasts were nonsignificant and of negligible effect size, even when a refined, sluggish cognitive tempo subgroup of the inattentive type was examined. Although ADHD versus comparison group differences largely withstood statistical control of baseline demographics and comorbidities, control of childhood IQ reduced executive function differences to nonsignificance. Yet when the subset of girls meeting diagnostic criteria for ADHD in adolescence was compared with the remainder of the participants, neuropsychological deficits emerged even with full statistical control. Overall, childhood ADHD in girls portends neuropsychological and executive deficits that persist for at least 5 years. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
1000.
MIMO (Multiple-Input Multiple-Output)的显著优点就是在不增加带宽的情况下,能够成倍地提高通信系统容量和频谱利用率,是未来移动通信与个人通信系统实现高速率数据传输,提高高传输质量的重要途径,也是未来移动通信系统广泛采用的关键技术.文中简要介绍了MIMO系统及其一种新的MIMO系统中的应用技术,即PARC(Per-antenna Rate Control)技术.  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