全文获取类型
收费全文 | 86546篇 |
免费 | 10098篇 |
国内免费 | 7181篇 |
专业分类
电工技术 | 7687篇 |
综合类 | 8365篇 |
化学工业 | 10323篇 |
金属工艺 | 5942篇 |
机械仪表 | 6127篇 |
建筑科学 | 6155篇 |
矿业工程 | 3067篇 |
能源动力 | 2218篇 |
轻工业 | 9292篇 |
水利工程 | 3131篇 |
石油天然气 | 3016篇 |
武器工业 | 1154篇 |
无线电 | 10065篇 |
一般工业技术 | 8013篇 |
冶金工业 | 4860篇 |
原子能技术 | 1710篇 |
自动化技术 | 12700篇 |
出版年
2024年 | 543篇 |
2023年 | 1373篇 |
2022年 | 3326篇 |
2021年 | 4246篇 |
2020年 | 3005篇 |
2019年 | 2168篇 |
2018年 | 2311篇 |
2017年 | 2689篇 |
2016年 | 2411篇 |
2015年 | 3714篇 |
2014年 | 4697篇 |
2013年 | 5754篇 |
2012年 | 7006篇 |
2011年 | 7387篇 |
2010年 | 7146篇 |
2009年 | 6634篇 |
2008年 | 6931篇 |
2007年 | 6612篇 |
2006年 | 5732篇 |
2005年 | 4646篇 |
2004年 | 3328篇 |
2003年 | 2315篇 |
2002年 | 2262篇 |
2001年 | 1986篇 |
2000年 | 1575篇 |
1999年 | 695篇 |
1998年 | 750篇 |
1997年 | 433篇 |
1996年 | 322篇 |
1995年 | 248篇 |
1994年 | 203篇 |
1993年 | 213篇 |
1992年 | 114篇 |
1991年 | 117篇 |
1990年 | 107篇 |
1989年 | 127篇 |
1988年 | 68篇 |
1987年 | 68篇 |
1986年 | 63篇 |
1985年 | 48篇 |
1984年 | 34篇 |
1983年 | 28篇 |
1982年 | 25篇 |
1981年 | 44篇 |
1980年 | 44篇 |
1979年 | 26篇 |
1978年 | 17篇 |
1977年 | 57篇 |
1976年 | 102篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Private information retrieval(PIR) is an important privacy protection issue of secure multi-party computation, but the PIR protocols based on classical cryptography are vulnerable because of new technologies,such as quantum computing and cloud computing. The quantum private queries(QPQ) protocols available, however, has a high complexity and is inefficient in the face of large database. This paper, based on the QKD technology which is mature now, proposes a novel QPQ protocol utilizing the key dilution and auxiliary parameter. Only N quits are required to be sent in the quantum channel to generate the raw key, then the straight k bits in the raw key are added bitwise to dilute the raw key, and a final key is consequently obtained to encrypt the database. By flexible adjusting of auxiliary parameters θ and k, privacy is secured and the query success ratio is improved. Feasibility and performance analyses indicate that the protocol has a high success ratio in first-trial query and is easy to implement, and that the communication complexity of O(N) is achieved. 相似文献
2.
Peer-to-Peer Networking and Applications - P2P-TV is a TV system that receives content through a peer-to-peer network. Content is stored in the distributed manner then to be serviced to users, and... 相似文献
3.
4.
根据我国煤炭样品制备技术现状和国内外发展趋势,研究开发了自动化控制无人值守煤炭联合制样系统,并从系统制样程序设计、系统整体结构设计、各单元模块设计、系统性能试验等方面对该系统的主要功能及软硬件结构进行介绍,并从称重单元、输送单元、破碎单元、缩分单元、干燥单元、粉碎单元、样品接收包装单元、除尘清洗单元等重点阐述了各单元模块设计,可实现煤样制备全过程无人化、信息化及样品的安全可追溯,其性能试验符合国标GB 474—2008中的相应要求。 相似文献
5.
The identification rate of UHF RFID system was restricted by multipath propagation effects.The system identification performance was studied considering the correlation coefficient between forward and reverse channels.Based on the generalized Rician fading channel model,the analytical expression of identification rate was derived under independent,full correlation and correlation cases.Compared with the existing analysis,the proposed uniform calculation formula of identification rate was for any correlation coefficient and kinds of channel conditions.The numerical computation and Monte-carlo simulations show that the influences of different correlation coefficients,channel conditions,sensitivity and distance on the identification rate. 相似文献
6.
This study presents a back-analysis of geotechnical parameters on prefabricated vertical drain improved ground at a site in the Mekong Delta. Various time?settlement behaviors that reflected different clay thicknesses and loading patterns were observed. The total surface settlement behavior at several monitoring locations was simulated using an updated exponential method that considered staged construction. The analyzed results were validated by substituting the values into a theoretical solution for radial consolidation. The estimated theoretical behaviors were comparable with the monitored behaviors. The geotechnical parameters were back-analyzed by applying the previously analyzed results to various theoretical and empirical formulas. However, the use of extensometer data that were installed at large intervals produced different values of the geotechnical properties. Furthermore, finite element analysis supported the back-analyzed total settlement behaviors and nearly disregarded the application of the geotechnical properties that were obtained using either surface or subsurface settlement data. However, settlements and excess pore pressures in the sublayers were not successfully predicted even when the geotechnical properties were adjusted. Thus, subsurface instruments that can be installed closely in thick clay deposits are required to reliably reevaluate the variations in geotechnical properties along a certain depth. 相似文献
7.
Multifunctional 3D Patternable Drug‐Embedded Nanocarrier‐Based Interfaces to Enhance Signal Recording and Reduce Neuron Degeneration in Neural Implantation 下载免费PDF全文
8.
9.
目的: 探讨自身免疫性溶血性贫血(AIHA)患者外周血中调节性B细胞(Bregs)的表达及其在该病发病中的意义。方法:选择16例自身免疫性溶血性贫血患者和14例健康志愿者为研究对象,用流式细胞术分析外周血CD19+IL-10+调节性B细胞及CD19+CD24hiCD27+调节性B细胞的表达;ELISA方法检测培养上清液中IL-10的水平。结果:自身免疫性溶血性贫血患者外周血中CD19+IL-10+调节性B细胞、CD19+CD24hiCD27+调节性B细胞的表达分别为(1.27±0.39)%、(9.85±2.18)%,健康志愿者组分别为(2.92±0.71)%、(26.47±4.31)%,两组比较差异有统计学意义(P<0.05);自身免疫性溶血性贫血患者细胞培养上清中IL-10的水平低于健康志愿者组(P<0.05)。结论:自身免疫性溶血性贫血患者外周血中CD19+IL-10+调节性B细胞及CD19+CD24hiCD27+调节性B细胞比例降低,提示调节性B细胞可能参与自身免疫性溶血性贫血的发病过程。 相似文献
10.