全文获取类型
收费全文 | 556篇 |
免费 | 117篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 52篇 |
综合类 | 29篇 |
化学工业 | 83篇 |
金属工艺 | 26篇 |
机械仪表 | 23篇 |
建筑科学 | 43篇 |
矿业工程 | 15篇 |
能源动力 | 21篇 |
轻工业 | 68篇 |
水利工程 | 31篇 |
石油天然气 | 23篇 |
武器工业 | 5篇 |
无线电 | 127篇 |
一般工业技术 | 66篇 |
冶金工业 | 13篇 |
原子能技术 | 8篇 |
自动化技术 | 63篇 |
出版年
2024年 | 8篇 |
2023年 | 37篇 |
2022年 | 57篇 |
2021年 | 37篇 |
2020年 | 42篇 |
2019年 | 32篇 |
2018年 | 28篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 30篇 |
2014年 | 27篇 |
2013年 | 47篇 |
2012年 | 37篇 |
2011年 | 35篇 |
2010年 | 21篇 |
2009年 | 26篇 |
2008年 | 31篇 |
2007年 | 22篇 |
2006年 | 12篇 |
2005年 | 21篇 |
2004年 | 4篇 |
2003年 | 16篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 11篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1980年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1967年 | 3篇 |
排序方式: 共有696条查询结果,搜索用时 15 毫秒
1.
Abdolhosseinzadeh Simin Derakhshanfard Nahideh 《Wireless Personal Communications》2020,110(3):1271-1282
Wireless Personal Communications - Mobile social network is a kind of social networks through which the nodes have some social features such as: gender, job, friendship relations, centrality, and... 相似文献
2.
3.
禹思敏 《电气电子教学学报》2002,24(2):29-32
对数字通信中MPSK系统的调制与解调问题进行了较为的分析,并以8PSK和循环码16PSK系统为例,阐述其调制器电路的逻辑设计方法。在此基础上给出了8PSK系统调制与解调的一种方案,讨论了循环码和自然二进制码16PSK系统的调制器的具体设计过程,该设计方法可应用于一般MPSK系统的逻辑设计。 相似文献
4.
Shivakumar Raman Ph.D. Assistant Professor Kaushal Panchal Graduate Research Assistant P.Simin Pulat Ph.D. Assistant Professor 《Computers & Industrial Engineering》1991,21(1-4):67-71
Tolerances are basic to the production of every part. This is because perfect parts cannot be produced with existing processes and machines. The determination of tolerances for the individual parts of a functional assembly is critical, but not trivial. Numerous approaches are suggested in past literature for (analytical) tolerance allocation. With the advent of total automation, more attempts are being made to computerize manual design tasks. Tolerance design, assignment and allocation can also be fully automated if the assembly function can be estimated by the computer.
In the present paper, an attempt is made to computerize tolerance assignment. A simple example of a two piece assembly, viz., a fit, is used to demonstrate the developed methodology. A feature extraction is first performed from both detail and assembly drawings. Then, probable assembly interfaces are determined using a rule based procedure. Consequently, tolerances are assigned to the basic dimensions of each feature and to the assembly interfaces using a tolerance database and user interaction. More complex analysis for tolerance allocation is also under study. 相似文献
5.
ATM技术能否在数据通信网中广泛采用取决于其是否能高效地支持现有业务,其中主要为非连接业务。本文介绍了几种基于ATM 的非连接业务支持方式和协议体系结构,对其进行了评述并对IP分组到ATM信元的封装效率进行了分析。 相似文献
6.
Koudymov A. Xuhong Hu Simin K. Simin G. Ali M. Yang J. Asif Khan M. 《Electron Device Letters, IEEE》2002,23(8):449-451
We demonstrate a novel RF switch based on a multifinger AlGaN/GaN MOSHFET. Record high saturation current and breakdown voltage, extremely low gate leakage current and low gate capacitance of the III-N MOSHFETs make them excellent active elements for RF switching. Using a single element test circuit with 1-mm wide multifinger MOSHFET we achieved 0.27 dB insertion loss and more than 40 dB isolation. These parameters can be further improved by impedance matching and by using submicron gate devices. The maximum switching power extrapolated from the results for 1A/mm 100 /spl mu/m wide device exceeds 40 W for a 1-mm wide 2-A/mm MOSHFET. 相似文献
7.
8.
9.
Akbar Eslami Simin Nasseri Bahram Yadollahi Alireza Mesdaghinia Foroogh Vaezi Ramin Nabizadeh Shahrokh Nazmara 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(11):1447-1453
BACKGROUND: Over the past several decades methyl tert‐butyl ether (MTBE) as additive to gasoline, intended to either boost ratings of fuel or to reduce air pollution, has been accepted worldwide. Since MTBE has high water solubility, the occurrence of fuel spills or leaks from underground storage tanks or transferring pipeline has led to the contamination of natural waters. In this study the degradation of aqueous MTBE at relatively high concentrations was investigated by a UV‐visible/ZnO/H2O2 photocatalytic process. The effects of important operational parameters such as pH, amount of H2O2, catalyst loading and irradiation time were also investigated. Concentration of MTBE and intermediates such as tert‐butyl formate and tert‐butyl alcohol were measured. RESULTS: Time required for complete degradation increased from 20 to 150 min when the initial concentration was increased from 10 to 500 mg L?1. The first‐order rate constants for degradation of MTBE were estimated to be 0.183–0.022 min?1 as the concentration increased from 10 to 500 mg L?1. Study of the overall mineralization monitored by total organic carbon analysis showed that at an initial concentration of 100 mg L?1 MTBE complete mineralization was obtained after 100 min under UV‐visible/ZnO/H2O2 photocatalysis. CONCLUSION: The data presented in this paper clearly indicated that UV‐visible/ZnO/O2 as an advanced oxidation process provides an efficient treatment alternative for the remediation of MTBE‐contaminated waters. Copyright © 2008 Society of Chemical Industry 相似文献
10.
本文将单一水库预泄能力约束法,推广到梯级水库汛期水位动态控制中,并建立了梯级水库汛期水位联合运用和动态控制模型,假定预报信息准确,在不降低下游保护对象的防洪标准的前提下,最大限度发挥梯级水库的兴利效益。以苗家坝、碧口水库为对象进行了实时调度模拟,其结果相比于原设计汛限水位动态控制方案,减少了弃水,且保证最大出库流量均在可控范围内,达到在不降低防洪标准的前提下提高梯级水库兴利效益的目的,大大提高了洪水资源利用率。 相似文献