全文获取类型
收费全文 | 2920篇 |
免费 | 172篇 |
国内免费 | 303篇 |
专业分类
电工技术 | 129篇 |
综合类 | 163篇 |
化学工业 | 359篇 |
金属工艺 | 333篇 |
机械仪表 | 128篇 |
建筑科学 | 239篇 |
矿业工程 | 115篇 |
能源动力 | 177篇 |
轻工业 | 171篇 |
水利工程 | 49篇 |
石油天然气 | 93篇 |
武器工业 | 31篇 |
无线电 | 188篇 |
一般工业技术 | 234篇 |
冶金工业 | 213篇 |
原子能技术 | 440篇 |
自动化技术 | 333篇 |
出版年
2024年 | 14篇 |
2023年 | 39篇 |
2022年 | 85篇 |
2021年 | 78篇 |
2020年 | 76篇 |
2019年 | 84篇 |
2018年 | 70篇 |
2017年 | 81篇 |
2016年 | 91篇 |
2015年 | 94篇 |
2014年 | 167篇 |
2013年 | 174篇 |
2012年 | 174篇 |
2011年 | 250篇 |
2010年 | 190篇 |
2009年 | 140篇 |
2008年 | 153篇 |
2007年 | 184篇 |
2006年 | 166篇 |
2005年 | 128篇 |
2004年 | 118篇 |
2003年 | 113篇 |
2002年 | 102篇 |
2001年 | 79篇 |
2000年 | 67篇 |
1999年 | 46篇 |
1998年 | 45篇 |
1997年 | 34篇 |
1996年 | 30篇 |
1995年 | 24篇 |
1994年 | 17篇 |
1993年 | 24篇 |
1992年 | 13篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 72篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1973年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有3395条查询结果,搜索用时 0 毫秒
11.
将信道传输容量动态分配技术应用于数字用户环路复用设备中,可用效地解决复用设备线路复用率和话音传输质量之间的矛盾,从而使复用设备具有最佳的传输效果。本文介绍了一种性能优良的统计复用信道的数字用户环路复用设备。 相似文献
12.
U(Ⅳ)-U(Ⅵ)同位素交换反应动力学研究 Ⅰ.Fe~(2+)对U(Ⅳ)-U(Ⅵ)同位素交换反应的催化作用 总被引:1,自引:0,他引:1
一、前言由于U(IV)-U(VI)同位素交换体系具有相当大的同位素效应和很好的稳定性,并且容易实现两相回流,这对于分离U同位素的工业应用都是十分有利的。但是,U(IV)-U(VI)同位素交换反应速度非常慢,常温下H~+浓度为1.0—4.0 mol/l时,速度常数为1.0×10~(-4)l~2/mol·s。因此要用U(IV)-U(VI)交换体系浓缩铀同位素,必须研究U(IV)-U(VI)交换反应动力学,找到加快交换反应的方法。 相似文献
13.
翁佩德 《等离子体科学和技术》2002,4(6):1579-1584
HT-7U is a superconducting tokamak. which is being constructed in Institute of Plasma Physics, Chinese Academy of Sciences. The mission of the HT-7U project is to develop a scientific and engineering basis of the steady state operation of advanced tokamak.The engineering design of the device has been optimized. The R&D program is going on. Short samples of the conductor and a CS model coil were tested. All the TF and PF coils will be manufactured and tested in Institute of Plasma Physics. Therefore, a 600-meter long jacketing line for cable-in-conduit conductors along with two winding machines, a set of VPI equipment and a test facility for the TF and PF coils are ready in ASIPP now. In this paper, the recent progress of the HT-7U is described. 相似文献
14.
EFFECTOFTHERATIOTh/UONTLDATINGACCURACY¥P.L.Leung(梁宝鎏);MichaelJ.Stokes(DepartmentofPhysicsandMaterialsScience,CityPolytechnico... 相似文献
15.
A bright electroless Ni-P deposition on AM50 magnesium alloy in a sulfate plating bath was proposed by using direct plating process with non-chromate pretreatment. The electroless Ni-P plating on AM50 magnesium alloy has an admirable appearance and good adhesion. The results indicate that the electroless Ni-P deposition with non-chromate pretreatment has better adhesion than that of zinc immersion coating. Anodic polarization curves indicate that the electroless Ni-P deposition obtained from the sulfate bath has similar corrosion-resistance to that obtained from basic nickel carbonate bath. The deposition process generates less pollutant by a non-chromate plating bath and is suitable for the magnesium alloys manufacture because of its low cost. The hardness of the electroless Ni-P plated AM50 is about HV 720.6 and HV 969.7 after heat treatments at 180℃ for 2 h. The wear resistance of Ni-P plated magnesium alloy specimens is about 5 to 9 times as high as that of bare magnesium alloys. 相似文献
16.
17.
In this paper we propose a new method to estimate parameters of a dynamical system from observation data on the basis of a neural network collocation method. We construct an object function consisting of squared residuals of dynamical model equations at collocation points and squared deviations of the observations from their corresponding computed values. The neural network is then trained by optimizing the object function.The proposed method is demonstrated by performing several numerical experiments for the optimal estimates of parameters for two different nonlinear systems. Firstly, we consider the weakly and highly nonlinear cases of the Lorenz model and apply the method to estimate the optimum values of parameters for the two cases under various conditions. Then we apply it to estimate the parameters of one-dimensional oscillator with nonlinear damping and restoring terms representing the nonlinear ship roll motion under various conditions. Satisfactory results have been obtained for both the problems. 相似文献
18.
19.
论文主要介绍了电机的调速方法、变频器的工作原理以及日本FRNIC500G7型变频器在桥式抓斗吊车上的应用,并分析了使用绕线式电机调速与鼠笼式电机变频调速之间的优缺点。 相似文献
20.
H. Hoedlmoser M. Moll J. Haerkoenen M. Kronberger J. Trummer P. Rodeghiero 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2007,580(3):1243-1249
Epitaxial (EPI) silicon has recently been investigated for the development of radiation tolerant detectors for future high-luminosity HEP experiments. A study of thick EPI silicon diodes irradiated with protons up to a fluence of has been performed by means of Charge Collection Efficiency (CCE) measurements, investigations with the Transient Current Technique (TCT) and standard CV/IV characterizations. The aim of the work was to investigate the impact of radiation damage as well as the influence of the wafer processing on the material performance by comparing diodes from different manufacturers. The changes of CCE, full depletion voltage and leakage current as a function of fluence are reported. While the generation of leakage current due to irradiation is similar in all investigated series of detectors, a difference in the effective doping concentration can be observed after irradiation. In the CCE measurements an anomalous drop in performance was found even for diodes exposed to very low fluences in all measured series. This result was confirmed for one series of diodes in TCT measurements with an infrared laser. TCT measurements with a red laser showed no type inversion up to fluences of for n-type devices whereas p-type diodes undergo type inversion from p- to n-type for fluences higher than . 相似文献