全文获取类型
收费全文 | 98260篇 |
免费 | 11998篇 |
国内免费 | 7657篇 |
专业分类
电工技术 | 8557篇 |
技术理论 | 2篇 |
综合类 | 9266篇 |
化学工业 | 12658篇 |
金属工艺 | 6114篇 |
机械仪表 | 6889篇 |
建筑科学 | 7757篇 |
矿业工程 | 3997篇 |
能源动力 | 2844篇 |
轻工业 | 9355篇 |
水利工程 | 2961篇 |
石油天然气 | 4200篇 |
武器工业 | 1497篇 |
无线电 | 12096篇 |
一般工业技术 | 8840篇 |
冶金工业 | 3829篇 |
原子能技术 | 1514篇 |
自动化技术 | 15539篇 |
出版年
2024年 | 617篇 |
2023年 | 1683篇 |
2022年 | 3800篇 |
2021年 | 5059篇 |
2020年 | 3580篇 |
2019年 | 2636篇 |
2018年 | 2933篇 |
2017年 | 3342篇 |
2016年 | 3072篇 |
2015年 | 4740篇 |
2014年 | 5898篇 |
2013年 | 6878篇 |
2012年 | 8458篇 |
2011年 | 8608篇 |
2010年 | 8029篇 |
2009年 | 7528篇 |
2008年 | 7549篇 |
2007年 | 7096篇 |
2006年 | 6384篇 |
2005年 | 5023篇 |
2004年 | 3683篇 |
2003年 | 2499篇 |
2002年 | 2320篇 |
2001年 | 1995篇 |
2000年 | 1547篇 |
1999年 | 826篇 |
1998年 | 401篇 |
1997年 | 314篇 |
1996年 | 293篇 |
1995年 | 248篇 |
1994年 | 162篇 |
1993年 | 107篇 |
1992年 | 109篇 |
1991年 | 70篇 |
1990年 | 66篇 |
1989年 | 50篇 |
1988年 | 28篇 |
1987年 | 29篇 |
1986年 | 33篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 24篇 |
1980年 | 23篇 |
1979年 | 24篇 |
1977年 | 9篇 |
1976年 | 18篇 |
1959年 | 15篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
目的观察迪银片治疗银屑病的临床疗效。方法30例银屑病患者,口服迪银片8周,采用PASI评分法评价治疗前后效果,并观察有无不良反应发生。结果患者痊愈率56.7%,显效率36.7%,总有效率93.3%,无明显的不良反应。结论迪银片是临床治疗银屑病的有效药物之一。 相似文献
42.
用己二酸二酰肼(ADH)对透明质酸(HA)进行化学修饰,制备交联透明质酸(HA-ADH)薄膜。粘度法测试表明HA-ADH是一种可降解的生物材料,并且与HA相比,HA.ADH的降解速率减慢。在此基础上,研究了以疏水性的替硝唑(TDZ)和亲水性的头孢唑啉钠(CEZ)为模拟药物的HA-ADH药物载体薄膜的释药性能。紫外-可见(UV-Vis)吸收光谱检测表明,HA-ADH是一种疏水性药物TDZ的优良缓释制荆,这是由于TDZ的疏水性和HA-ADH薄膜的缓慢溶胀和降解性能的结合而得到的,药物的释放主要受扩散机制控制。 相似文献
43.
软交换技术的发展及其应用 总被引:1,自引:0,他引:1
软交换是下一代网络NGN的核心技术,本文从软交换的概念入手,介绍了软交换的基本功能及其优点.软交换的网络系统结构、软交换的对外接口等内容,并探讨了软交换技术的应用。 相似文献
44.
介绍了钻孔灌注桩成孔质量的影响因素 ,详细叙述了钢筋笼的制作和吊放处理步骤 ,阐述了断桩发生的原因 ,提出了具体的防治措施 ,经实践效果良好 相似文献
45.
In recent years, constructing a virtual backbone by nodes in a connected dominating set (CDS) has been proposed to improve the performance of ad hoc wireless networks. In general, a dominating set satisfies that every vertex in the graph is either in the set or adjacent to a vertex in the set. A CDS is a dominating set that also induces a connected sub‐graph. However, finding the minimum connected dominating set (MCDS) is a well‐known NP‐hard problem in graph theory. Approximation algorithms for MCDS have been proposed in the literature. Most of these algorithms suffer from a poor approximation ratio, and from high time complexity and message complexity. In this paper, we present a new distributed approximation algorithm that constructs a MCDS for wireless ad hoc networks based on a maximal independent set (MIS). Our algorithm, which is fully localized, has a constant approximation ratio, and O(n) time and O(n) message complexity. In this algorithm, each node only requires the knowledge of its one‐hop neighbours and there is only one shortest path connecting two dominators that are at most three hops away. We not only give theoretical performance analysis for our algorithm, but also conduct extensive simulation to compare our algorithm with other algorithms in the literature. Simulation results and theoretical analysis show that our algorithm has better efficiency and performance than others. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
46.
Effects of surfactant/silica and silica/cerium ratios on the characteristics of mesoporous Ce-MCM-41
Se Ho Park Bo Yune Song Tai Gyu Lee 《Journal of Industrial and Engineering Chemistry》2008,14(2):261-264
Using the surfactant CTMABr (cetyltrimethyl ammonium bromide) and cerium(IV) sulfate, mesoporous Ce-MCM-41 molecular sieves were produced under a hydrothermal condition with various surfactant/silica (surfactant/Si) and silica/cerium (Si/Ce) ratios. Changes to the structural traits caused by changing the molar ratios of both surfactant/Si and Si/Ce were investigated. XRD (X-ray diffraction), FT-IR (fourier transform infrared spectroscopy), and SEM (scanning electro microscopy) were used for the characterization of prepared mesoporous samples. Among the tested molar ratios, surfactant/Si ratio of 0.5 and 0.2 showed highest values of d1 0 0 and intensity, respectively, for the Si-MCM-41. XRD analysis also identified a quintessential hexagonal structure of Ce-MCM-41 for the Si/Ce molar ratio higher than 40 (maintaining the surfactant/Si ratio at 0.2). When cerium content was increased to have the Si/Ce molar ratio of 20, the hexagonal structure of Ce-MCM-41 was collapsed due to the structural stress of substituted cerium. FT-IR results confirmed calcination of Ce-MCM-41 and the incorporation of Ce4+ ions of cerium sulfate into the silica surface with proper removal of the surfactant. Rod-like shape with rounded edges of the prepared Ce-MCM-41 samples was identified by SEM. These results suggest surfactant/Si ratio of 0.2 and Si/Ce ratio of 40 for the production of Ce-MCM-41 with the highest level of crystallinity. 相似文献
47.
冯博 《西安邮电学院学报》2008,13(3):33-36
讨论了几种微蜂窝路径损耗模式,并用我国某城市测量的微蜂窝传播数据对COST231WI,修正COST231WI和Xia模式进行了检验,结果表明修正COST231模式的误差最小,Xia模式次之,COST231WI模式最差。从而得到修正COST231模式比较符合我国实际的微蜂窝传播预测模式。 相似文献
48.
49.
50.
GAO Qinglu~ WU Bo~ GUO Guang~ .School of Management Wuhan University of Technology Wuhan China .School of Mechanical Engineering Huazhong University of Science Technology Wuhan China 《武汉理工大学学报》2006,28(Z2)
This article puts forward a scheduling method for nonlinear process plan shop floor.Task allocation and load bal- ance are realized by bidding mechanism.Though the agent interaction process,the execution of tasks is determined and the coherence of manufacturing decision is verified.The employment of heuristic index can help to optimize the system performance. 相似文献