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   448874篇
  免费   32195篇
  国内免费   9390篇
电工技术   23779篇
技术理论   94篇
综合类   23737篇
化学工业   80437篇
金属工艺   22677篇
机械仪表   26000篇
建筑科学   31766篇
矿业工程   12769篇
能源动力   12858篇
轻工业   31544篇
水利工程   6892篇
石油天然气   25480篇
武器工业   3111篇
无线电   51855篇
一般工业技术   58044篇
冶金工业   20896篇
原子能技术   4477篇
自动化技术   54043篇
  2025年   959篇
  2024年   8628篇
  2023年   8000篇
  2022年   11391篇
  2021年   16168篇
  2020年   15519篇
  2019年   14946篇
  2018年   14021篇
  2017年   15521篇
  2016年   15432篇
  2015年   18420篇
  2014年   22635篇
  2013年   26992篇
  2012年   26182篇
  2011年   28301篇
  2010年   24750篇
  2009年   23425篇
  2008年   22701篇
  2007年   21833篇
  2006年   22185篇
  2005年   19383篇
  2004年   12880篇
  2003年   11380篇
  2002年   10255篇
  2001年   9339篇
  2000年   9845篇
  1999年   10769篇
  1998年   8742篇
  1997年   7261篇
  1996年   6805篇
  1995年   5682篇
  1994年   4715篇
  1993年   3324篇
  1992年   2713篇
  1991年   2117篇
  1990年   1614篇
  1989年   1350篇
  1988年   1086篇
  1987年   761篇
  1986年   595篇
  1985年   383篇
  1984年   294篇
  1983年   230篇
  1982年   225篇
  1981年   151篇
  1980年   162篇
  1979年   73篇
  1978年   35篇
  1977年   40篇
  1976年   56篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology.  相似文献   
5.
6.
A central event in the life of a cellular system is the interaction between the exterior and the interior compartments. Biochemical signals arrive at the cellular surface, bind to their membrane bound receptor followed by a conformational change triggering the release of an internal chemical or electrical signal.This basic principle is followed by all our perceptive abilities like sense of smell or taste, but also by different signal transduction pathways involved in nerve conductivity, vision, sense of touch or hearing. To follow and mimic this principle of parallel registration is one of the aims of modern nanobiotechnology. If we are able to specifically biofunctionalize small arrays of a solid surface, which could be an electrode or a semiconductor, this approach will enable us to build up devices called “biochips” or “biosensors” that allow the determination of bioactive molecules with high specificity at lowest concentrations. Potential pharmacological active substrates might be screened as well as new receptors may be determined. Applications in genomics as well as proteomics are realistic. The major prerequisite for such a broad spectrum of applications is the fabrication of receptive surfaces. Biomolecules have to be surface‐adsorbed in a highly reproducible, oriented and well organised fashion, a task which in biology is taken by the cellular membranes as external or internal receptive surfaces. The physical principles like hydrogen bonds, electrostatic or hydrophobic interactions that lead to such an organized surface are well known. To synthesize molecular building blocks and to position them onto an otherwise unspecific surface is one of the challenges of nanobiotechnology combining biological knowledge and chemical skills with biophysical techniques that allow to handle or analyze even single molecules.  相似文献   
7.
对在实际组网中选择合理的ASON架构和保护方式作了相应分析,并为搭建可向ASON平滑演进的传统网络时需注意的问题提供了参考意见,  相似文献   
8.
We propose and evaluate a medium-access control (MAC) protocol for synchronous cellular packet direct-sequence code-division multiple-access (DS/CDMA). The protocol is designed for handling a variety of multimedia traffic types in an integrated wireless-access network (IWAN). For instance, the protocol is suited for carrying multiple traffic types of different priorities. An analytical model for the equilibrium state has been developed for the proposed protocol. A comparative evaluation of the protocol is done for three different radio frequency bandwidths currently under consideration for personal communication services (PCS), i.e., 1.25 MHz, 5 MHz, and 10 MHz. Our results demonstrate that the proposed protocol is both robust and flexible for the intended IWAN applications. It offers a significant multiplexing gain as the bandwidth increases  相似文献   
9.
通过对相变增韧陶瓷及一种可切削玻璃-陶瓷动态疲劳(恒应力速率)试验中高应力速率区断裂应力下降现象的理论分析,发现这种现象与材料的阻力特性(R-curve)密切相关。确立的σ_f-σ理论关系能够很好地描述整个应力速率区间内的动态疲劳试验结果。高应力速率区σ_f-σ在双对数坐标下为负斜率直线,直线斜率为(m为阻力曲线KR=k(△a)~m的指数),断裂主要由材料阻力行为控制;低应力速率区,σ_f-σ在双对数坐标下为正斜率直线,直线斜率为 (n为应力腐蚀指数),断裂主要由材料应力腐蚀行为控制。建立了测定材料阻力特性的一种新方法,分别用这种方法及压痕/弯曲方法对一种可切削玻璃-陶瓷的阻力特性进行了实验测定,两种方法所得结果有很好的一致性。  相似文献   
10.
Introduction   Owing to long-time running, more facilities including stations, pipelines, vessels have become corrosive and aged ,some process has grown old, it has exert more burden for the maintenance and repair.Simultaneously, the fluid production rate, oil production rate and water injection rate has changed greatly so that the inflicts and problems from the established surface systems will become more obvious. Energy cost of production and running has increasing continuously. Capacity has been unbalance in systems and areas.   ……  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