全文获取类型
收费全文 | 17321篇 |
免费 | 2132篇 |
国内免费 | 1377篇 |
专业分类
电工技术 | 303篇 |
综合类 | 2485篇 |
化学工业 | 2402篇 |
金属工艺 | 1528篇 |
机械仪表 | 638篇 |
建筑科学 | 5838篇 |
矿业工程 | 459篇 |
能源动力 | 282篇 |
轻工业 | 461篇 |
水利工程 | 933篇 |
石油天然气 | 689篇 |
武器工业 | 113篇 |
无线电 | 698篇 |
一般工业技术 | 2812篇 |
冶金工业 | 638篇 |
原子能技术 | 83篇 |
自动化技术 | 468篇 |
出版年
2024年 | 91篇 |
2023年 | 256篇 |
2022年 | 493篇 |
2021年 | 591篇 |
2020年 | 649篇 |
2019年 | 614篇 |
2018年 | 649篇 |
2017年 | 745篇 |
2016年 | 730篇 |
2015年 | 712篇 |
2014年 | 1081篇 |
2013年 | 1264篇 |
2012年 | 1241篇 |
2011年 | 1335篇 |
2010年 | 915篇 |
2009年 | 973篇 |
2008年 | 984篇 |
2007年 | 1028篇 |
2006年 | 1044篇 |
2005年 | 816篇 |
2004年 | 663篇 |
2003年 | 543篇 |
2002年 | 521篇 |
2001年 | 439篇 |
2000年 | 377篇 |
1999年 | 363篇 |
1998年 | 304篇 |
1997年 | 241篇 |
1996年 | 190篇 |
1995年 | 170篇 |
1994年 | 159篇 |
1993年 | 131篇 |
1992年 | 113篇 |
1991年 | 78篇 |
1990年 | 55篇 |
1989年 | 68篇 |
1988年 | 35篇 |
1987年 | 34篇 |
1986年 | 17篇 |
1985年 | 25篇 |
1984年 | 13篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1981年 | 6篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
铝灰渣是铝熔铸过程中产生的废弃物。本文主要介绍了酒钢东兴铝业嘉峪关分公司铝灰渣的产生量、排放、利用情况、化学成分及表面特征,并简要介绍了铝灰渣、铝灰的循环利用途径。 相似文献
2.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method
in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer.
But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results
showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that,
the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic
whereas chloride doped polyaniline films were found to be highly hygroscopic. 相似文献
3.
介绍了循环伏安法的产生背景、原理。应用该技术可以快速、方便地对润滑油中抗氧剂、总酸(碱)值进行测定,并且可以对不同厂家润滑油的抗氧剂包进行区别。该技术还可以有效地评价润滑油的使用寿命和设备工作状况。 相似文献
4.
岩石物理横波速度曲线计算技术 总被引:15,自引:3,他引:12
横波速度是地震勘探中的重要参数。针对实际生产中缺乏横波速度测井曲线资料,利用经验公式计算精确度不高的问题,通过对横波速度计算理论模型的研究分析,选择Blot-Gassman模型法,利用岩石矿物成分、流体成分、孔隙度及密度等测井曲线进行横波速度测井曲线的计算,并对横波速度计算技术和流程进行研究。在实际工区进行了横波速度曲线计算,计算结果与实测横波吻合程度较高,误差小于10%,该技术在储层和流体识别预测的应用中取得了较好效果。 相似文献
5.
试论循环水装置的经济性及其成本分析 总被引:2,自引:1,他引:1
通过对循环水装置的投资和成本分析,阐述了建设该装置的经济性和社会意义。 相似文献
6.
用实验方法研究了Al_2O_3陶瓷缺口试件在循环载荷作用下的疲劳寿命。结果表明,缺口导致的应力集中效应显著降低了循环疲劳寿命;若用缺口根部最大应力为应力水平,则不同缺口半径陶瓷试件具有相同疲劳断裂规律,说明陶瓷材料的疲劳集中系数和理论应力集中系数相同。本文还分析讨论了陶瓷材料的循环疲劳寿命表达式和循环疲劳断裂机理。 相似文献
7.
8.
G. Ranzi M. A. Bradford B. Uy 《International journal for numerical methods in engineering》2004,61(5):657-672
The use of the conventional semi-analytical stiffness method in finite element analysis, in which interpolation polynomials are used to develop the stiffness relationships, leads to problems of curvature locking when beam-type elements are developed for composite members with partial interaction between the materials of which it is comprised. The curvature locking phenomenon that occurs for composite steel–concrete members is quite well reported, and the general approach to minimizing the undesirable ramifications of curvature locking has been to use higher-order polynomials with increasing numbers of internal nodes. This paper presents an alternate formulation based on a direct stiffness approach rather than starting from pre-defined interpolation polynomials, and which does not possess the undesirable locking characteristics. The formulation is based on a more general approach for a bi-material composite flexural member, whose constituent materials are joined by elastic shear connection so as to provide partial interaction. The stiffness relationships are derived, and these are applied to a simply supported and a continuous steel–concrete composite beam to demonstrate the efficacy of the method, and in particular its ability to model accurately both very flexible and very stiff shear connection that causes difficulties when implemented in competitive semi-analytical algorithms. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
9.
Yu. A. Radin I. A. Grishin T. S. Kontorovich O. B. Panshina A. V. Chugin 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2006,40(2):113-119
Problems arising with connecting the second exhaust-heat boiler to the first exhaust-heat boiler under load in the case of
flow circuits of combined-cycle plants of type PGU-450 are considered. Similar problems exist for two-boiler single-turbine
units of type PGU-325 and for two-boiler single-turbine units of traditional steampower plants with an output of 200–300 MW
upon connection of the second furnace of a two-furnace boiler to the operating first furnace. Analysis of the temperature-induced
stressed state and of the cyclic strength of thick-walled elements of the steam-water conduit of PGU-450 and of two-furnace
boilers of two-boiler single-turbine units with an output of 200–300 MW (the check valve, the inlet header of the water economizer)
is used for determining the steam temperature differences in the high-pressure conduits to the steam turbine and the order
of connection of the second exhaust-heat boiler to the operating fist one. Modes of enabling a two-boiler single-turbine unit
of a combined-cycle plant, which are most “rigid” from the standpoint of thermal strength, are determined.
__________
Translated from élektricheskie Stantsii, No. 2, February 2006, pp. 11–17. 相似文献
10.
R. C. Pennefather D. H. Boone 《International Journal of Pressure Vessels and Piping》1996,66(1-3):351-358
Cyclic oxidation tests were performed on a large variety of commercially available overlay coatings. The results of cyclic oxidation tests confirmed that the composition of the coating as well as the processing method of the coating can affect the life of the system. Coating life was determined by the time to coating penetration and initiation of substrate attack. As this work was part of a effort to evaluate the relative protectiveness of available coating systems for Industrial Gas Turbine applications at relatively high temperature, an extensive testing programme was undertaken. The different coatings were tested to visual failure. The results presented in this paper concentrate on the surface instability of the coating. Apart from usual oxidation of the coating an additional degradation mechanism was observed. A mechanical effect caused by the instability of the coating as a result of the difference in the thermal coefficient of expansion and mechanical properties between the substrate and coating. This effect, the so-called “rumpling” effect, resulted in a significant reduction in time to penetration and was in some systems the life controlling factor. 相似文献