全文获取类型
收费全文 | 100161篇 |
免费 | 10014篇 |
国内免费 | 4998篇 |
专业分类
电工技术 | 7332篇 |
技术理论 | 10篇 |
综合类 | 7274篇 |
化学工业 | 15762篇 |
金属工艺 | 6037篇 |
机械仪表 | 6189篇 |
建筑科学 | 8020篇 |
矿业工程 | 3371篇 |
能源动力 | 2887篇 |
轻工业 | 6124篇 |
水利工程 | 2116篇 |
石油天然气 | 5838篇 |
武器工业 | 1019篇 |
无线电 | 11834篇 |
一般工业技术 | 11413篇 |
冶金工业 | 4348篇 |
原子能技术 | 1327篇 |
自动化技术 | 14272篇 |
出版年
2024年 | 524篇 |
2023年 | 1870篇 |
2022年 | 3679篇 |
2021年 | 4930篇 |
2020年 | 3722篇 |
2019年 | 2902篇 |
2018年 | 3377篇 |
2017年 | 3700篇 |
2016年 | 3291篇 |
2015年 | 4533篇 |
2014年 | 5545篇 |
2013年 | 6628篇 |
2012年 | 7245篇 |
2011年 | 7793篇 |
2010年 | 6639篇 |
2009年 | 6144篇 |
2008年 | 5946篇 |
2007年 | 5437篇 |
2006年 | 5366篇 |
2005年 | 4571篇 |
2004年 | 3080篇 |
2003年 | 2364篇 |
2002年 | 2167篇 |
2001年 | 1789篇 |
2000年 | 1851篇 |
1999年 | 1917篇 |
1998年 | 1468篇 |
1997年 | 1251篇 |
1996年 | 1245篇 |
1995年 | 952篇 |
1994年 | 789篇 |
1993年 | 583篇 |
1992年 | 467篇 |
1991年 | 312篇 |
1990年 | 251篇 |
1989年 | 206篇 |
1988年 | 185篇 |
1987年 | 112篇 |
1986年 | 83篇 |
1985年 | 52篇 |
1984年 | 32篇 |
1983年 | 30篇 |
1982年 | 44篇 |
1981年 | 24篇 |
1980年 | 21篇 |
1979年 | 9篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1959年 | 9篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
BACKGROUND: The enterococci have become important nosocomial pathogens. They can cause multiple site infections and enterococcal bacteremia becomes more frequently associated with a high mortality rate. Previous studies of enterococcal bacteremia showed a variety of results. To establish the significance and importance of enterococci as nosocomial pathogens in this hospital, to characterize their clinical pictures and to search for the risk factors for mortality, this retrospective study was performed. METHODS: There were 208 cases of enterococcal bacteremia which occurred from 1988 to 1992. Twenty-seven cases had no medical charts, dismissing possibility of evaluation. Finally, 181 cases of enterococcal bacteremia were analysed. RESULTS: One hundred and eighteen episodes were nosocomial infections. Polymicrobial bacteremia occurred in 68.5% of the patients and the most common co-isolate was Pseudomonas aeruginosa. Those patients (78.5%) with underlying diseases and malignancies were the most common underlying problems. The portal of entry could be found in 69.6 percent of patients, with the gastrointestinal tract the most common sources. Antimicrobial susceptibility testing showed high gentamicin resistance rate (89.5%), and ampicillin still had about 80 percent sensitivity rate. The group who received specific antibiotic therapy for enterococcus showed lower mortality (36.4% versus 47.6%). Only one case had infective endocarditis. Forty-nine patients suffered from septic shock, the cause of 30 deaths. Totally 75 patients died during hospitalization. Besides sepsis, another major cause of death was their underlying diseases itself. CONCLUSIONS: Enterococci have no doubt become important nosocomial pathogens and enterococcal bacteremia were associated with high mortality, especially in elderly patients with underlying diseases such as malignancy or diabetes. When clinically dealing with sepsis from the gastrointestinal or biliary tract, especially when previous cephalosporins therapy showed no response, the possibility of enterococcal bacteremia should always be considered. 相似文献
32.
33.
通过密度测定和DSC热分析,观测了超高分子量聚乙烯的辐射效应。实验结果表明:在吸收剂量0—1.13MGy范围内,密度随吸收剂量的增加而增大,熔化热和熔点也有所增加,特别是在低剂量范围内增加十分明显。以上结果都说明,超高分子量聚乙烯在辐照过程中,结晶在完善或有新的结晶形成 相似文献
34.
超细Fe3O4粒子表面包覆酞菁钴性质研究 总被引:3,自引:1,他引:2
本文研究了合成载氧体的金属有机化学液相淀积法制造工艺,所得产物经TEM、XPS、Moss-bauer谱和B-H仪等手段,研究了它的结构和磁性能。实验表明,酞青钴以薄层形式包覆在Fe_3O_4的表面,封闭了Fe_3O_4的表面孔洞,稳定了Fe_3O_4的物相,增强了磁性能。 相似文献
35.
A distributed problem solving system can be characterized as a group of individual cooperating agents running to solve common problems. As dynamic application domains continue to grow in scale and complexity, it becomes more difficult to control the purposeful behavior of agents, especially when unexpected events may occur. This article presents an information and knowledge exchange framework to support distributed problem solving. From the application viewpoint the article concentrates on the stock trading domain; however, many presented solutions can be extended to other dynamic domains. It addresses two important issues: how individual agents should be interconnected so that their resources are efficiently used and their goals accomplished effectively; and how information and knowledge transfer should take place among the agents to allow them to respond successfully to user requests and unexpected external situations. The article introduces an architecture, the MASST system architecture, which supports dynamic information and knowledge exchange among the cooperating agents. The architecture uses a dynamic blackboard as an interagent communication paradigm to facilitate factual data, business rule, and command exchange between cooperating MASST agents. The critical components of the MASST architecture have been implemented and tested in the stock trading domain, and have proven to be a viable solution for distributed problem solving based on cooperating agents 相似文献
36.
王鹏 《消防技术与产品信息》2002,(11):34-36
“网吧”等互联网上网服务营业场所 (以下简称网吧 )是集上网聊天、上网冲浪、发电子邮件、查寻资料、休闲娱乐于一体的公共娱乐场所 ,普遍受到人们特别是青少年的欢迎。网吧在给人们工作、学习、生活带来便利的同时 ,也带来了一定的火灾危险 ,震惊全国的北京海淀区“6 .16 -蓝极速”特大火灾事故就是一个典型的案例。网吧存在的突出消防安全问题 ,已经引起公安消防机构的重视 ,并纳入消防监督检查视线 ,部署开展了以网吧为重点的消防安全专项整治。网吧的消防安全现状如何 ,究竟有何火灾危险 ,如何防范 ,笔者谈了以下拙见。 一、网吧的… 相似文献
37.
概述了RSView32工控软件的特点和使用方法 ,并通过贵溪冶炼厂的一个液位自动控制系统的人机界面设计说明了如何在控制系统中使用RSView32软件。文章特别介绍了如何用VBA程序设计来扩展其功能 相似文献
38.
一种新的加权最小二乘测距定位方法 总被引:8,自引:0,他引:8
三站二维定位问题是最小定位问题,一般只利用几何关系就能获得定位估计,但由于未利用距离测量的统计信息,定位精度较差。该文先将点到点的距离测量转化为点到线的距离估计,再在此基础上推导出一种新的加权几休定位方法,其中加权的确定利用了距离测量的统计信息。仿真实验表明,在测距误差较小时新方法具有更高的定位精度。 相似文献
39.
This report deals with direct observations of microcrack linkage at the crack tip prior to macroscopic crack initiation. It is shown that this process is directly linked to the inclusion distribution in the material and can be considered in terms of an R curve to describe microcrack development. 相似文献
40.
On the basis of the compensation of errors it is postulated that the most accurate correction may not always give the most accurate result for calorific value, and experimental evidence for this is presented. A new criterion is therefore suggested for judging the best (not necessarily the most accurate) cooling correction. Using this principle the cooling correction formula previously proposed is improved which results in higher accuracy whilst retaining the original simplicity. 相似文献