全文获取类型
收费全文 | 360973篇 |
免费 | 29995篇 |
国内免费 | 21815篇 |
专业分类
电工技术 | 57827篇 |
技术理论 | 28篇 |
综合类 | 38058篇 |
化学工业 | 18380篇 |
金属工艺 | 12610篇 |
机械仪表 | 30856篇 |
建筑科学 | 32174篇 |
矿业工程 | 14576篇 |
能源动力 | 11979篇 |
轻工业 | 8746篇 |
水利工程 | 11100篇 |
石油天然气 | 11511篇 |
武器工业 | 5717篇 |
无线电 | 32780篇 |
一般工业技术 | 18855篇 |
冶金工业 | 13425篇 |
原子能技术 | 3252篇 |
自动化技术 | 90909篇 |
出版年
2024年 | 1341篇 |
2023年 | 3596篇 |
2022年 | 6544篇 |
2021年 | 8218篇 |
2020年 | 9261篇 |
2019年 | 7017篇 |
2018年 | 6324篇 |
2017年 | 9170篇 |
2016年 | 10567篇 |
2015年 | 12146篇 |
2014年 | 23303篇 |
2013年 | 19920篇 |
2012年 | 26373篇 |
2011年 | 28315篇 |
2010年 | 21388篇 |
2009年 | 21649篇 |
2008年 | 21985篇 |
2007年 | 27510篇 |
2006年 | 24629篇 |
2005年 | 21814篇 |
2004年 | 17996篇 |
2003年 | 16142篇 |
2002年 | 12598篇 |
2001年 | 10471篇 |
2000年 | 8807篇 |
1999年 | 7089篇 |
1998年 | 5362篇 |
1997年 | 4586篇 |
1996年 | 3877篇 |
1995年 | 3226篇 |
1994年 | 2688篇 |
1993年 | 1867篇 |
1992年 | 1554篇 |
1991年 | 1149篇 |
1990年 | 911篇 |
1989年 | 774篇 |
1988年 | 558篇 |
1987年 | 333篇 |
1986年 | 212篇 |
1985年 | 223篇 |
1984年 | 240篇 |
1983年 | 198篇 |
1982年 | 171篇 |
1981年 | 125篇 |
1980年 | 93篇 |
1979年 | 91篇 |
1978年 | 70篇 |
1977年 | 66篇 |
1976年 | 29篇 |
1959年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
本文阐述了在WINDOWS环境下开发电脑,电视、电话信息查询系统系统的基本思想、硬软件环境和具体实施方法,并介绍了软件流程。 相似文献
72.
Air cleaning as a means of mitigating the risks arising from exposure to indoor radon progeny has been evaluated in a single-family house in the north eastem US. using an automated, semi-continuous activity-weighted size distribution measurement system. The measurements included radon concentration, condensation nuclei count, and activity-weighted size distribution of radon decay products. Measurements were made in the house with and without an operating air filtration system and with various particle sources common to normal indoor activities operating. Aerosols were generated by running water in a shower, candle burning, cigarette smoking, vacuuming, opening doors, and cooking. Using a room model, the changes in attachment rates, average attachment diameters, and deposition rates of the unattached fraction with and without the air cleaning system were calculated. In the presence of active aerosol sources, the air filtration unit typically reduced the concentration of particles within the hour following the end of particle generation. After candle burning, cigarette smoking, and vacuuming in the bedroom, the reductions of PAEC by air filtration are about 60% with the air filtration system operating in the bedroom. During cooking in the kitchen, the reductions of PAEC in the bedroom with the air filtration system were about 40%. However, for all cases the dose reductions were smaller than the particle and PAEC reductions. For those particles that were generated within the bedroom, there was a 20% to 50% reduction in dose. In the case of cooking where the door was open and particles infiltrated from the rest of the house, the dose reduction was only 5% on average and appears to be insignificant. Thus, the dose reductions were h e r than the reductions in activity concentration, but there were no cases where the estimated dose actually increased. 相似文献
73.
针对双组分等温平行反应体系,分析讨论了以提高催化剂活性和选择性为目标时催化剂活性组分的最优分布形式(为δ-函数分布),并给出了确定这种反应体系的催化剂的最佳活性层位置的计算方法。结果表明:以提高选择性为目标的最佳活性层位置比以提高活性为目标的要更靠近催化剂核心,实用的最优位置应介于二者之间。最后,本文还研究了反应动力学级数、本性选择性以及内扩散模数(Thiele 模数)等因素对最佳活性层位置的影响。 相似文献
74.
75.
The paper addresses the design of two-level power system stabilizers using an optimal reduced order model whose state variables are torque angles and speeds. The reduced order model retains their physical meaning and is used to design a two-level linear feedback controller that takes into account the realities and constraints of electrical power systems. The two-level control strategy is used, and a global control signal is generated from the output variables to minimize the effect of interactions. The effectiveness of this controller is evaluated and a multimachine system is given as an example to illustrate the advantages of the proposed method. Responses of the system with a two-level scheme and an optimal reduced order scheme are included for comparative analysis. 相似文献
76.
化工企业环境因素的评价 总被引:1,自引:0,他引:1
化工企业环境因素评价是建立环境管理体系的核心任务,化工企业生产过程的特点决定了其环境因素数量多、环境影响大、识别评价难、控制难度大。本文介绍了化工企业环境因素评价的技术方法和过程,可以为提高环境因素评价的科学性、客观性和充分性提供参考。 相似文献
77.
探讨了影响煤矿矿井水检测质量的主要因素,按照全过程、全要素控制的理念提出了检测前、检测中和检测后的控制措施。 相似文献
78.
79.
我们于1985年对我院1984年开展肝单光子发射计算机断层以来的52例肝病人进行了分析总结。结果表明,肝单光子发射断层在诊断肝内占位性病变方面比普通肝静态γ照相有许多优点。需要指出的是,肝单光予发射断层的若干优点及诊断的准确性是与物理条件的正确选择和应用密切相关的。本文根据至今积累的近100例断层经验,从技术方面介绍了影响单 相似文献
80.
Katsuhiko Fuwa Tatsuo Narikiyo Yasuyuki Funahashi 《Electrical Engineering in Japan》2002,138(4):50-60
A well‐known control system which can reduce the adverse effects of disturbances is a disturbance observer. However, in many cases of mechanical systems, system disturbances which do not satisfy the matching condition may be imposed. Therefore, it may be difficult to reduce the adverse effects of the disturbances by the traditional disturbance observer. In this paper, a method of control system synthesis for disturbance rejection using a dual observer is proposed. This method is based on the zeroing induced by the disturbance localization problem. This problem may be solved by dividing the state space into observable subspace and unobservable subspace. As compared with an H∞ controller based on perfect observation, the usefulness of the proposed control system for disturbance rejection is demonstrated by numerical simulations for a two‐mass spring system. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 50–60, 2002; DOI 10.1002/eej.1138 相似文献