全文获取类型
收费全文 | 31855篇 |
免费 | 2419篇 |
国内免费 | 782篇 |
专业分类
电工技术 | 886篇 |
技术理论 | 1篇 |
综合类 | 2408篇 |
化学工业 | 7903篇 |
金属工艺 | 1090篇 |
机械仪表 | 1102篇 |
建筑科学 | 2264篇 |
矿业工程 | 1190篇 |
能源动力 | 489篇 |
轻工业 | 3923篇 |
水利工程 | 346篇 |
石油天然气 | 902篇 |
武器工业 | 181篇 |
无线电 | 1131篇 |
一般工业技术 | 4679篇 |
冶金工业 | 1797篇 |
原子能技术 | 244篇 |
自动化技术 | 4520篇 |
出版年
2025年 | 26篇 |
2024年 | 463篇 |
2023年 | 423篇 |
2022年 | 611篇 |
2021年 | 772篇 |
2020年 | 837篇 |
2019年 | 805篇 |
2018年 | 693篇 |
2017年 | 855篇 |
2016年 | 964篇 |
2015年 | 966篇 |
2014年 | 1656篇 |
2013年 | 1701篇 |
2012年 | 2332篇 |
2011年 | 2409篇 |
2010年 | 1813篇 |
2009年 | 1863篇 |
2008年 | 1529篇 |
2007年 | 2078篇 |
2006年 | 1838篇 |
2005年 | 1593篇 |
2004年 | 1376篇 |
2003年 | 1265篇 |
2002年 | 1078篇 |
2001年 | 838篇 |
2000年 | 686篇 |
1999年 | 597篇 |
1998年 | 489篇 |
1997年 | 380篇 |
1996年 | 293篇 |
1995年 | 285篇 |
1994年 | 199篇 |
1993年 | 169篇 |
1992年 | 136篇 |
1991年 | 96篇 |
1990年 | 80篇 |
1989年 | 101篇 |
1988年 | 94篇 |
1987年 | 60篇 |
1986年 | 50篇 |
1985年 | 70篇 |
1984年 | 86篇 |
1983年 | 93篇 |
1982年 | 98篇 |
1981年 | 34篇 |
1980年 | 32篇 |
1979年 | 23篇 |
1978年 | 20篇 |
1977年 | 17篇 |
1955年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
61.
电力负荷的不断增长是电网发展的根据,正确地预测电力负荷,既是为了保证国民经济发展及人民生活对电力的需求,也是电网自身发展的需求。电力负荷预测工作是电网规划工作的重要组成部分,也是电网规划的基础工作。在掌握铜陵地区经济、电网历史实绩的前提下,探讨了在电网规划中运用中长期常规负荷预测的几种方法,得出铜陵地区中长期负荷预测结果,以便为铜陵地区电网发展提供与此相适应的负荷保证。 相似文献
62.
科学评估电力失负荷价值可为我国在制定电力规划、电力市场经济运行、电力需求侧管理与电力产业政策决策等方面提供科学的依据.随着"低碳经济"概念的提出,碳减排责任已逐渐成为各个国家、地区或产业部门关注的焦点之一.本文基于投入产出方法,研究了我国产业部门的电力失负荷价值与碳减排责任,并予以了实证分析. 相似文献
63.
64.
In this work we proposed a novel preparation-adsorption desulfurization method for dibenzothiophene over sawdust-derived nickel/activated carbon prepared by 400°C one step carbonization-activation-modified process. The adsorbent was characterized by X-ray Diffraction (XRD), Boehm titration method, Scanning Electron Microscope (SEM) and N2 adsorption-desorption technology. The result show that 30% HNO3 aqueous solution and calcination 2 h for the 30%-NiO/AC adsorbent trend to better desulfurization performance with NiO active adsorption sites and surface oxygen-containing functional groups. After high temperature adsorption desulfurization, the sawdust-derived nickel/activated carbon occurred activation and reaming again, both the specific surface and the microspore volume have been great changed. 相似文献
65.
We propose a low-cost method for testing logic circuits, termed balance testing, which is particularly suited to built-in self testing. Conceptually related to ones counting and syndrome testing, it detects faults by checking the difference between the number of ones and the number of zeros in the test response sequence. A key advantage of balance testing is that the testability of various fault types can be easily analyzed. We present a novel analysis technique which leads to necessary and sufficient conditions for the balance testability of the standard single stuck-line (SSL) faults. This analysis can be easily extended to multiple stuck-line and bridging faults. Balance testing also forms the basis for design for balance testability (DFBT), a systematic DFT technique that achieves full coverage of SSL faults. It places the unit under test in a low-cost framework circuit that guarantees complete balance testability. Unlike most existing DFT techniques, DFBT requires only one additional control input and no redesign of the underlying circuit is necessary. We present experimental results on applying balance testing to the ISCAS 85 benchmark circuits, which show that very high fault coverage is obtained for large circuits even with reduced deterministic test sets. This coverage can always be made 100% either by adding tests or applying DFBT.This research was supported by the National Science Foundation under Grant No. MIP-9200526. Parts of this paper were published in preliminary form in Proc. 23rd Symp. Fault-Tolerant Computing, Toulouse, June 1993, and in Proc. 31st Design Automation Conf, San Diego, June 1994. 相似文献
66.
A. Barletta 《International Journal of Heat and Mass Transfer》2005,48(10):2042-2049
The necessary condition for the occurrence of parallel mixed convection flow in an inclined duct is determined by employing the Boussinesq approximation. A sample case involving an inclined infinitely-wide plane channel is discussed to illustrate this condition. It is shown that, according to the necessary condition, parallel flow cannot occur in this case. Indeed, the investigated flow is the superposition of a parallel streamwise flow and a secondary flow. An exponential equation of state for the fluid is assumed and the balance equations are solved analytically to determine the dimensionless velocity distribution, as well as the conditions for the occurrence of flow reversal. 相似文献
67.
电子设备热分析技术研究 总被引:1,自引:0,他引:1
加强对电子设备热分析技术的研究,能够实现对设备的有效热控制,从而保障其使用性能和寿命。文中论述了热分析技术的两种方法,即解析法和数值法的解题思路和步骤,并对热分析软件在电子设备设计中的运用进行了研究探索,结合设备级热分析结果进行了验证,达到了较高的精度,满足工程需求。 相似文献
68.
69.
Harinder P S Makkar Michael Blümmel Norbert K Borowy Klaus Becker 《Journal of the science of food and agriculture》1993,61(2):161-165
Abstract. A method for gravimetric determination of tannins based on binding with insoluble polyvinylpyrrolidone (PVP) is presented. The gravimetric method gives the absolute amount of tannins and avoids problems of standards associated with spectrophotometric methods. The method was applied to nine browse and tree leaves. The values obtained correlate significantly with tannins determined spectrophotometrically, protein precipitation capacities and protein precipitable phenotics. This method together with other tannin assays will be useful in nutritional studies. The present study also demonstrates the different behaviour of tannic acids from different commercial sources towards PVP suggesting the presence of different moieties in tannic acids from different commercial sources and even among batches from the same source thereby affecting the results obtained using the spectrophotometric methods. Use of well-defined tannic acid as a standard in spectrophotometric methods is suggested which will allow meaningful comparison of values obtained from different laboratories. 相似文献
70.
磁性流体制备技术的现状与展望 总被引:11,自引:0,他引:11
对国内外各种磁性流体制备技术进行了分类,并介绍了各种方法的原理和优缺点,同时对今后磁性流体制备技术的发展方向提出了展望。 相似文献