全文获取类型
收费全文 | 292570篇 |
免费 | 32589篇 |
国内免费 | 10012篇 |
专业分类
电工技术 | 14846篇 |
技术理论 | 10篇 |
综合类 | 14353篇 |
化学工业 | 57244篇 |
金属工艺 | 15356篇 |
机械仪表 | 16145篇 |
建筑科学 | 18029篇 |
矿业工程 | 5726篇 |
能源动力 | 7235篇 |
轻工业 | 23230篇 |
水利工程 | 5205篇 |
石油天然气 | 13258篇 |
武器工业 | 1712篇 |
无线电 | 35651篇 |
一般工业技术 | 48608篇 |
冶金工业 | 16583篇 |
原子能技术 | 5880篇 |
自动化技术 | 36100篇 |
出版年
2024年 | 1073篇 |
2023年 | 3698篇 |
2022年 | 7194篇 |
2021年 | 9996篇 |
2020年 | 8373篇 |
2019年 | 8735篇 |
2018年 | 10111篇 |
2017年 | 11349篇 |
2016年 | 11028篇 |
2015年 | 12459篇 |
2014年 | 15225篇 |
2013年 | 19005篇 |
2012年 | 18153篇 |
2011年 | 19460篇 |
2010年 | 17117篇 |
2009年 | 16615篇 |
2008年 | 15945篇 |
2007年 | 15081篇 |
2006年 | 13989篇 |
2005年 | 11743篇 |
2004年 | 8933篇 |
2003年 | 8351篇 |
2002年 | 8324篇 |
2001年 | 7402篇 |
2000年 | 6676篇 |
1999年 | 5710篇 |
1998年 | 4654篇 |
1997年 | 3880篇 |
1996年 | 3442篇 |
1995年 | 2933篇 |
1994年 | 2432篇 |
1993年 | 2036篇 |
1992年 | 1845篇 |
1991年 | 1550篇 |
1990年 | 1497篇 |
1989年 | 1323篇 |
1988年 | 1162篇 |
1987年 | 1032篇 |
1986年 | 932篇 |
1985年 | 860篇 |
1984年 | 812篇 |
1983年 | 736篇 |
1982年 | 733篇 |
1981年 | 732篇 |
1979年 | 775篇 |
1978年 | 808篇 |
1977年 | 779篇 |
1976年 | 816篇 |
1974年 | 743篇 |
1973年 | 749篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Yu. V. Balaban-Irmenin N. G. Fokina 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(5):306-312
The effect of internal-corrosion inhibitors on heating-system pipelines is investigated. Tests were conducted on a testing
device for polarization measurements under conditions corresponding to the Rostov Heat-Supply System. The concentration of
OEDP-zinc, which provides a high degree of protection from general corrosion, is determined. The reagent has been successfully
incorporated into the Rostov No. 2 TPP.
__________
Translated from élektricheskie Stantsii, No. 7, July 2007, pp. 37–43. 相似文献
992.
Yu. V. Balaban-Irmenin N. G. Fokina 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(4):228-232
The reliability of heat-supply systems is determined primarily by internal corrosion of the pipelines. The concentration of
oxygen in the water exerts a major influence on the corrosion. In systems with a standard oxygen content, OéDF-Zn is a highly
effective corrosion inhibitor. However, there are systems in which the quality of deaeration of the make-up water of the heat-supply
system is low (or deaeration is nonexistent), and the concentration of oxygen is considerably above the standard value. Classed
among these systems, for example, are the HWS systems, which are incorporated into closed heat-supply systems. The oxygen
concentration in these systems is analyzed to assess the situation.
__________
Translated from élektricheskie Stantsii, No. 6, June 2007, pp. 35–39. 相似文献
993.
V. A. Borodulya Yu. S. Teplitskii Yu. G. Epanov I. I. Markevich 《Journal of Engineering Physics and Thermophysics》1987,53(6):1393-1396
Experimental data was obtained on external heat transfer in infiltrated granular beds of coarse particles. It was determined that calcualtions with the proposed model agree satisfactorily with the experimental results.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 6, pp. 919–923, December, 1988. 相似文献
994.
Robustness analysis of responses of vibration control structures with uncertain parameters using interval algorithm 总被引:1,自引:0,他引:1
Variations in system parameters due to uncertainties may result in system performance deterioration. Uncertainties in modeling of structures are often considered to ensure that control system is robust with respect to response errors. Hence, the uncertain concept plays an important role in vibration control of the engineering structures. The paper discusses the robustness of responses of vibration control systems with the uncertain parameters. The vibration control problem of an uncertain system is approximated by a deterministic one. The uncertain parameters are described by interval variables. The uncertain state matrix is constructed directly using system physical parameters and avoided to use bounds in Euclidean norm. The feedback gain matrix is determined based on the deterministic systems, and then it is applied to the actual uncertain systems. A method to calculate the upper and lower bounds of responses of the closed-loop system with uncertain parameters is presented. The upper bounds of responses can be used to estimate the robustness of responses of the controlled system with uncertain parameters. Two numerical examples are given to illustrate the applications of the present approach. 相似文献
995.
作者对5个盆地18个轻质油样品作了C_1—C_7轻烃分析,检测出29种单体轻烃。通过轻烃组成特征研究,认识到石蜡指数(PI_1)和庚烷值(PI_2)作为成熟度的指标,不受沉积盆地类型影响;C_6,C_7烃类族组分受母质类型影响较大。陆相(含煤地层)有机质生成轻质芳烃(苯)的含量比海相有机质要高。新疆塔里木盆地沙参2井原油的轻烃分析资料表明,该井油源岩为海相沉积。 相似文献
996.
QRS feature extraction using linear prediction 总被引:10,自引:0,他引:10
This communication proposes a method called linear prediction (a high performant technique in digital speech processing) for analyzing digital ECG signals. There are several significant properties indicating that ECG signals have an important feature in the residual error signal obtained after processing by Durbin's linear prediction algorithm. This communication also indicates that the prediction order need not be more than two for fast arrhythmia detection. The ECG signal classification puts an emphasis on the residual error signal. For each ECG's QRS complex, the feature for recognition is obtained from a nonlinear transformation which transforms every residual error signal to a set of three states pulse-code train relative to the original ECG signal. The pulse-code train has the advantage of easy implementation in digital hardware circuits to achieve automated ECG diagnosis. The algorithm performs very well in feature extraction in arrhythmia detection. Using this method, our studies indicate that the PVC (premature ventricular contraction) detection has at least a 92 percent sensitivity for MIT/BIH arrhythmia database. 相似文献
997.
998.
The Uniform Covering by Probabilistic Rejection (UCPR) algorithm was used, in conjunction with the Soil and Water Assessment Tool (SWAT) model, to identify P loads from point source and nonpoint source polluters in the upper Etowah River basin (UERB) in Georgia. The key findings of the research are as follows. The mean absolute error was preferred over the root mean square error as a search criterion for the UCPR algorithm when water quality observations are scarce. The undocumented P load from point sources in the UERB was consistently estimated as about 43 kg/d by the proposed method; but the method was not able to identify the broiler litter application rate to the poultry/beef operation pastures. Point sources (both documented and undocumented), poultry/beef operation pastures, and forests are the three major contributors of P. During 1992-1996, on average they accounted for 36.4, 31.7, and 17.2% of P load from the UERB, respectively. 相似文献
999.
药物预防HIV传播是人类战胜HIV的重要手段。现将预防HIV感染药的研发现状,抗HIV药在预防母婴传播,暴露前后预防的研发和应用动态作一综述。 相似文献
1000.