全文获取类型
收费全文 | 9865篇 |
免费 | 936篇 |
国内免费 | 491篇 |
专业分类
电工技术 | 517篇 |
技术理论 | 1篇 |
综合类 | 732篇 |
化学工业 | 1610篇 |
金属工艺 | 712篇 |
机械仪表 | 691篇 |
建筑科学 | 661篇 |
矿业工程 | 321篇 |
能源动力 | 246篇 |
轻工业 | 711篇 |
水利工程 | 196篇 |
石油天然气 | 611篇 |
武器工业 | 97篇 |
无线电 | 1101篇 |
一般工业技术 | 1212篇 |
冶金工业 | 464篇 |
原子能技术 | 108篇 |
自动化技术 | 1301篇 |
出版年
2024年 | 45篇 |
2023年 | 211篇 |
2022年 | 333篇 |
2021年 | 468篇 |
2020年 | 335篇 |
2019年 | 281篇 |
2018年 | 329篇 |
2017年 | 394篇 |
2016年 | 273篇 |
2015年 | 427篇 |
2014年 | 555篇 |
2013年 | 608篇 |
2012年 | 718篇 |
2011年 | 672篇 |
2010年 | 679篇 |
2009年 | 602篇 |
2008年 | 551篇 |
2007年 | 548篇 |
2006年 | 572篇 |
2005年 | 445篇 |
2004年 | 316篇 |
2003年 | 259篇 |
2002年 | 261篇 |
2001年 | 217篇 |
2000年 | 195篇 |
1999年 | 198篇 |
1998年 | 159篇 |
1997年 | 123篇 |
1996年 | 100篇 |
1995年 | 87篇 |
1994年 | 83篇 |
1993年 | 47篇 |
1992年 | 51篇 |
1991年 | 38篇 |
1990年 | 23篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 18篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
In recent years, some Chinese doctors have proposed a new concept, gallstone removal without gallbladder excision, along with transition of the medical model. As there is no specialized endoscope for gallstone removal without gallbladder excision, we designed and produced a new series of gallbladder endoscopes and accessories that have already been given a Chinese invention patent (No. ZL200810199041.2). The design of these gallbladder endoscopes was based on the anatomy and physiology of the gallbladder, characteristics of gallbladder disease, ergonomics, and industrial design. This series of gallbladder endoscopes underwent clinical trials in two hospitals appointed by the State Administration of Traditional Chinese Medicine. The clinical trials showed that surgeries of gallstones, gallbladder polyps, and cystic duct calculus could be smoothly performed with these products. In summary, this series of gallbladder endoscopes is safe, reliable, and effective for gallstone removal without gallbladder excision. This note comprehensively introduces the research and design of this series of gallbladder endoscopes. 相似文献
22.
23.
Pultruded fiber–reinforced plastic (FRP) composite structural shapes (beams and columns) are thin-walled open or closed sections consisting of assemblies of flat plates and commonly made of E-glass fiber and either polyester or vinylester resins. Due to high strength-to-stiffness ratio of composites and thin-walled sectional geometry of FRP shapes, buckling is the most likely mode of failure before material failure. In this paper, explicit analyses of local buckling of rectangular orthotropic composite plates with various unloaded edge boundary conditions (i.e., (1) rotationally restrained along both unloaded edges (RR), and (2) one rotationally restrained and the other free along the unloaded edges (RF)) and subjected to uniform in-plane axial action at simply-supported loaded edges are first presented. A variational formulation of the Ritz method is used to establish an eigenvalue problem, and explicit solutions of plate local buckling coefficients in term of the rotational restraint stiffness (k) are obtained. The two cases of rotationally restrained plates (i.e., the RR and RF plates) are further treated as discrete plates of closed and open sections, and by considering the effect of elastic restraints at the joint connections of flanges and webs, the local buckling of different FRP shapes under uniform axial compression is studied. The approximate expressions of the rotational restraint stiffness (k) for various common FRP sections are provided, and their application to sectional local buckling predictions is illustrated. The explicit local buckling formulas of rotationally restrained plates are validated with the exact transcendental solutions. The analytical predictions for local buckling of various FRP profiles based on the present discrete plate analysis and considering the elastic restraints of the flange–web connections are in excellent agreements with available experimental results and finite element eigenvalue analyses. A design guideline for local buckling prediction and related performance improvement is proposed. The present explicit formulation can be applied effectively to determine the local buckling capacities of composite plates with elastic restraints along the unloaded edges and can be further used to predict the local buckling strength of FRP shapes. 相似文献
24.
本文介绍了如何用分析嵌套选择语句的逻辑关系,主要方法是借助分裂图画出N-S图,最后再根据IF…ELSE…语句配对原理分析出各子句的关系。 相似文献
25.
5月的厦门,白鹭翩翩,春光灿灿。来自全国30个省(区、市)、计划单列市、各信息协作网团体、各专业媒体的代表们从祖国的四面八方汇集到这里,参加’98国家经济信息系统工作会议。与往年的信息系统工作会议不同,今年的会议有太多的背景可资评说。背景之一,本次会... 相似文献
27.
基于矢量合成的平衡机最小可达剩余不平衡度测试方法的研究 总被引:1,自引:0,他引:1
通过对国标规定的平衡机最小可达剩余不平衡度评定方法的分析和研究,指出了该方法在原理和方法上所存在的问题,并且提出了一种全新的评定方法。这种基于矢量分析的新的评定方法能够快速、准确地计算出转子的最小可达剩余不平衡度,提高平衡机测试的准确性和现场测试效率,为更加客观地评价被测平衡机的综合性能提供了依据。 相似文献
28.
Morphology of graphite in hot-compressed nodular iron 总被引:1,自引:0,他引:1
X. Zhao T. F. Jing Y. W. Gao G. Y. Qiao J. F. Zhou W. Wang 《Journal of Materials Science》2004,39(19):6093-6096
29.
Integrated Circuit 卡应用系统安全设计研究 总被引:1,自引:0,他引:1
针对许多IntegratedCircuit(IC)卡应用系统采用的被动存储型IC卡一般不能防止非法复制或篡改,对IC卡应用系统的安全结构进行了分析,基于安全核存在假设和算法安全性假设提出了IC卡应用系统理论安全模型.并以IC卡预付费电表系统为例,对攻击者的破译策略进行了分析,讨论了其安全设计策略. 相似文献
30.
经过分析和反复试验,确定了聚合矿物复合( P M C)材料制造铣床夹具脱模剂,设计了所用浇铸模具、夹具中的预埋件在大量反复试验的基础上,确定了实用的 P M C制造机床夹具的完整工艺过程 相似文献