全文获取类型
收费全文 | 24840篇 |
免费 | 1669篇 |
国内免费 | 1128篇 |
专业分类
电工技术 | 1426篇 |
技术理论 | 1篇 |
综合类 | 2049篇 |
化学工业 | 2410篇 |
金属工艺 | 1258篇 |
机械仪表 | 1325篇 |
建筑科学 | 2956篇 |
矿业工程 | 1037篇 |
能源动力 | 706篇 |
轻工业 | 1510篇 |
水利工程 | 849篇 |
石油天然气 | 1543篇 |
武器工业 | 601篇 |
无线电 | 3978篇 |
一般工业技术 | 2088篇 |
冶金工业 | 1200篇 |
原子能技术 | 301篇 |
自动化技术 | 2399篇 |
出版年
2024年 | 24篇 |
2023年 | 141篇 |
2022年 | 208篇 |
2021年 | 245篇 |
2020年 | 282篇 |
2019年 | 277篇 |
2018年 | 296篇 |
2017年 | 455篇 |
2016年 | 512篇 |
2015年 | 521篇 |
2014年 | 1015篇 |
2013年 | 993篇 |
2012年 | 1486篇 |
2011年 | 1624篇 |
2010年 | 1337篇 |
2009年 | 1408篇 |
2008年 | 1730篇 |
2007年 | 2254篇 |
2006年 | 2054篇 |
2005年 | 1809篇 |
2004年 | 1574篇 |
2003年 | 1351篇 |
2002年 | 1041篇 |
2001年 | 961篇 |
2000年 | 787篇 |
1999年 | 616篇 |
1998年 | 486篇 |
1997年 | 393篇 |
1996年 | 346篇 |
1995年 | 296篇 |
1994年 | 230篇 |
1993年 | 176篇 |
1992年 | 153篇 |
1991年 | 118篇 |
1990年 | 98篇 |
1989年 | 78篇 |
1988年 | 67篇 |
1987年 | 35篇 |
1986年 | 41篇 |
1985年 | 20篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1966年 | 6篇 |
1964年 | 4篇 |
1957年 | 7篇 |
1955年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Novel lamellar mesostructured hydroxyapatites have firstly been synthesized by template-assisted technique. The mild and nontoxic surfactant, phosphoric acid monododecyl ester (MAP), is used to act as a structure-directing template. The structure of sample was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscope and Transmission electron microscopy. The results indicate that the obtained sample is a well-organized lamellar mesostructured hydroxyapatite with a uniform layer spacing of 3.64 nm. 相似文献
12.
A new method of studying the corrosion inhibition mechanism of rare earth metal(REM) on LC4 Al alloy with the spilt cell technique was studied. The principle and experimental method of the spilt cell technique were analyzed. By measuring the change of net-electric current between the two electrodes caused by the change of the amount of oxygen in the solution and the addition of CeCl3, the influence of corrosive performance of CeCl3 on LC4 super-power aluminum alloy in the 0.1 mol·L−1 NaCl solution was investigated. Meanwhile, the conditional changes of pH values, CeCl3 solution, additire and time of performance were also studied. Finally, the features of electrode surface were revealed by using SEM and X-ray energy-dispersive spectrometry (EDS). By combining these with other electric chemical techniques, such as potential-time curve, polarization curve et al. 相似文献
13.
14.
Generalized difference control of parallel streams temperatures 总被引:1,自引:0,他引:1
A furnace with multiple parallel passes and multiple burners is commonly seen in petroleum refineries. In order to maintain the furnace running in a safe, stable, and high-efficiency state it is necessary to control the outlet temperatures of the multiple passes to be the same. Due to the fact that the process of the oil heating in such furnace is nonlinear, multivariable, time varying, has serious coupling among passes, has frequent dynamic changes and a large time delay, traditional control methods have trouble in controlling these temperatures, and some advanced control methods, including predictive control, adaptive control, and robust control, are usually too complex for convenient use. In this paper, a control technique, called differences control technique (DsCT), is proposed to distribute the stream flowrates such that the stream temperatures are as identical as possible. The principle of the proposed technique is explained and demonstrated, and the results of its application to a real-life petroleum refinery furnace are also reported. The DsCT technique has the following advantages: it does not need complicated design procedures, the controller structure is simple, it is easy to apply, and it can be canonically applied to furnaces with different number of passes. 相似文献
15.
This paper presents the mass transfer results from an impinging liquid jet to a rotating disk. The mass transfer coefficients were measured using the electrochemical limiting diffusion current technique (ELDCT). Rotational Reynolds number (Rer) in the range of 3.4 × 104–1.2 × 105, jet Reynolds number (Rej) 1.7 × 104–5.3 × 104 and non-dimensional jet-to-disk spacing (H/d) 2–8 were taken into consideration as parameters. It was found that the jet impingement resulted in a substantial enhancement in the mass transfer compared to the case of the rotating disk without jet. 相似文献
16.
This paper deals with the decomposition analysis of energy-related CO2 emissions in Greece from 1990 to 2002. The Arithmetic Mean Divisia Index (AMDI) and the Logarithmic Mean Divisia Index (LMDI) techniques are applied and changes in CO2 emissions are decomposed into four factors: income effect, energy intensity effect, fuel share effect and population effect. The period-wise and time series analyses show that the biggest contributor to the rise in CO2 emissions in Greece is the income effect; on the contrary, the energy intensity effect is mainly responsible for the decrease in CO2 emissions. A comparison of the results of the two techniques gave an insight in the intricacies of energy decomposition. Finally, conclusions and future areas of research are presented. 相似文献
17.
介绍液态软起动技术在济钢 15000 m3/h制氧机配套的 6000 kW同步电动机上的应用情况,阐述了系统的原理、特点、仿真计算及实际应用后达到的效果. 相似文献
18.
19.
布里奇曼法生长碲镉汞晶体的固液界面形态研究 总被引:2,自引:0,他引:2
文中综述了布里奇曼法及加速坩埚旋转技术的布里奇曼法生工碲镉汞晶体过程中固液界面形态的研究结果,简单讨论了固液界面形态对组分分布的影响,并将两种技术所得的组分分布结果进行了比较,在分析影响固液界面形态因素的基础上,认为加速坩埚旋转技术是目前改善固液界面形态的有效方法。 相似文献
20.
本文介绍红外热象技术在工程热物理研究中某些应用的探索。作为实例,通过热象技术,实验研究了具有水平凸台离散热源的倾斜板的散热,在研究它的自然对流换热部份结合利用激光全息干涉技术。此间着重于分析倾斜角对散热的影响。 相似文献