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   9244篇
  免费   974篇
  国内免费   530篇
电工技术   491篇
综合类   548篇
化学工业   1451篇
金属工艺   476篇
机械仪表   581篇
建筑科学   566篇
矿业工程   168篇
能源动力   310篇
轻工业   689篇
水利工程   244篇
石油天然气   328篇
武器工业   82篇
无线电   1494篇
一般工业技术   1293篇
冶金工业   366篇
原子能技术   165篇
自动化技术   1496篇
  2024年   29篇
  2023年   124篇
  2022年   254篇
  2021年   442篇
  2020年   308篇
  2019年   307篇
  2018年   382篇
  2017年   376篇
  2016年   359篇
  2015年   417篇
  2014年   568篇
  2013年   696篇
  2012年   697篇
  2011年   708篇
  2010年   582篇
  2009年   565篇
  2008年   524篇
  2007年   482篇
  2006年   398篇
  2005年   354篇
  2004年   277篇
  2003年   343篇
  2002年   359篇
  2001年   346篇
  2000年   218篇
  1999年   155篇
  1998年   117篇
  1997年   70篇
  1996年   48篇
  1995年   52篇
  1994年   32篇
  1993年   39篇
  1992年   17篇
  1991年   7篇
  1990年   13篇
  1989年   10篇
  1988年   7篇
  1987年   5篇
  1986年   6篇
  1985年   10篇
  1984年   3篇
  1983年   5篇
  1982年   2篇
  1981年   6篇
  1980年   8篇
  1979年   4篇
  1976年   7篇
  1973年   2篇
  1967年   2篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
基于B/S架构的组件式PACS系统设计   总被引:3,自引:1,他引:2  
传统的PACS系统(医学影像存档与传输系统)几乎全都是采用C/S架构,该设计模式对软件发布后系统的部署、升级、维护都造成了极大的困难,而对于PACS这一类客户需求灵活多变的特殊软件系统,矛盾显得更为突出.针对该问题提出了一套完整的基于B/S架构的PACS系统解决方案,然后简要地分析了系统的各个功能模块,在此基础之上结合国内PACS的发展现状,又介绍了一种组件式PACS系统的设计方法,将这两者结合运用将给PACS系统的开发带来极大的方便.  相似文献   
62.
本文在起停式飞剪的电控系统改造中,采用基于T400工艺模块的分级分布式计算机控制系统,建立了控制系统的数学模型,并针对该控制系统进行了MATLAB仿真。仿真结果表明,该控制系统设计合理,调节系统的动、静态特性较好。  相似文献   
63.
在分析了几种现有的典型RFID安全协议的特点和缺陷的基础上,提出了一种轻量级的RFID安全协议,该协议将一次性密码本与询问一应答机制相结合,实现了安全高效的读取访问控制,最后建立该协议的理想化模型,利用BAN逻辑对该协议进行了形式化分析,在理论上证明其安全性.  相似文献   
64.
The growth and metastasis of solid tumors is dependent on angiogenesis. The vascular endothelial growth factor (VEGF) and its cell surface receptor in human KDR (kinase domain containing receptor or VEGFR-2) have particular interest because of their importance in angiogenesis. The development of novel inhibitors of VEGFR-2 would be helpful to check the growth of tumors. Quantitative structure activity relationship (QSAR) analyses used to understand the structural factors affecting inhibitory potency of thiazole-substituted pyrazolone derivatives. Several pharmacophore-based models indicated the importance of steric, hydrophobic and hydrogen bond acceptor groups to inhibitory activity. The comparative molecular field analyses (CoMFA) and comparative molecular similarity indices analyses (CoMSIA) based 3D-QSAR models were derived using pharmacophore-based alignment. Both CoMFA (q2 = 0.70, r2 = 0.97 and ) and CoMSIA (q2 = 0.54, r2 = 0.82 and ) gave reasonable results. The molecular docking (receptor-guided technique) with a recently reported receptor structure (PDB = 1YWN) were performed. The docked alignment was subsequently used for 3D-QSAR (CoMFA; q2 = 0.56, r2 = 0.97, , CoMSIA; q2 = 0.58 r2 = 0.91, ). The overall both studies were indicated, steric, electrostatic and hydrogen bond acceptor effects contribute to the inhibitory activity. CoMFA and CoMSIA models suggested that a positive bulk with hydrophobic effect is desirable around position 4 and 5 and hydrogen bond acceptor groups around pyrazolones ring will be helpful.  相似文献   
65.
At the present time the VoIP (Voice over Internet Protocol) service is generally accepted as an alternative for people seeking cheaper means to make a phone call. Users of VoIP service may fall anywhere along a spectrum between types at two extremes: one of which is an ordinary caller who doesn’t use the telephone for commercial purposes, while the other is a person who generates spam calls for commercial purposes. The focus of this paper concerns modeling of spam callers’ behavior to calculate the SPIT (Spam over Internet Telephony) level for management of the quality of service. From the perspective of a VoIP service provider’s view, spam callers are also a type of customer and sometimes they are valuable for increasing revenue. However, if a service provider does not manage spam calls, it can harm their business, because ordinary users might not receive phone calls using the phone numbers of the VoIP service. Thus, there is a trade-off between revenues and usability in managing spam calls in the VoIP service. This work presents a model of spam caller’s behavior using the DEVS (Discrete Event System Specification) formalism. The DEVS formalism is applicable as a model of behavior, by defining the state and state transition of the target of the model. In our model, we use six main parameters to define the states and state transitions. Each state is represented by a number which indicates the SPIT level of a caller. If the value is 1.0 then the caller is more similar to a spam caller. Based on the model definition, we constructed a SPIT level Calculation UI (User Interface) that is used to manage spam calls to improve VoIP service quality.  相似文献   
66.
高速可配置Rijndael算法的设计与实现   总被引:1,自引:0,他引:1  
针对网络通信的安全要求,给出了在集成电路设计中实现Rijndael算法的高吞吐率解决方案。对算法实现进行了优化,具有支持密钥长度和数据长度的可变选择与组合配置,加密和解密工作通道完全独立,全双工安全高速通信等特点。已通过了FPGA的验证与电路实现。通过对比分析综合仿真结果,该实现相对于目前已知的实现方案在性能和速度上具有很大的优势。  相似文献   
67.
李永锋  谷川 《计算机技术与发展》2009,19(12):201-204,208
以网络教育为手段,以学校培养人才的目标、学科建设的方向和学生实际情况为依据,探索和研究网络教学服务平台的结构模型和实现方法。分析了当前网络教学平台存在的不足,在此基础上以学校的应用定位、学科发展的方向和学生实际情况为依据,提出了一个基于Web的学科教学服务平台系统结构。根据该结构设计了一个基于n层结构的.NET实现模型。利用该模型实现了一个基于.NET的《计算机辅助教学》教学服务平台。该平台的建立有效地弥补了我校《计算机辅助教学》网络教学的不足。  相似文献   
68.
Wilson's disease (WD) is characterized by excessive accumulation of intracellular copper in liver and extrahepatic tissues, leading to significant oxidative stress and tissue damage. To date, several diagnostic biomarkers for WD such as serum ceruloplasmin, serum or urine copper levels and copper content in liver have been identified. However, these biomarkers may not be convincing for the diagnosis in some WD patients. To identify additional novel diagnostic biomarkers, we compared the serum protein profiles of asymptomatic childhood WD patients (n=20), without neurologic manifestation or liver cirrhosis, with normal controls (n=13). Fourteen spots, five up‐regulated and nine down‐regulated (>2‐fold), were differentially expressed in WD patients in comparison to normal control on 2‐DE. Among them, three spots were down‐regulated in both male and female WD. MS/MS analysis revealed that the three spots were complement component C3, complement factor B and alpha‐2 macroglobulin. By comparative proteome analysis, complement component C3, complement factor B and alpha‐2 macroglobulin, which are related to oxidative stress and inflammation, turned out to be good candidates for novel diagnostic biomarkers for early stages of WD.  相似文献   
69.
Zhang  Zhe  Xiong  Hui  Xu  Tong  Qin  Chuan  Zhang  Le  Chen  Enhong 《Knowledge and Information Systems》2022,64(9):2435-2456
Knowledge and Information Systems - To assure the development of effective treatment plans, it is crucial for understanding the complication relationships among diseases. In practice, traditional...  相似文献   
70.
Jin  Rong  Zeng  Kai  Jiang  Chuan 《Wireless Networks》2022,28(6):2437-2453
Wireless Networks - Friendly spectrum jamming is a flexible scheme to establish secure communications among heterogeneous wireless devices without the need of encryption. Previous works have...  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