全文获取类型
收费全文 | 14023篇 |
免费 | 1567篇 |
国内免费 | 1190篇 |
专业分类
电工技术 | 446篇 |
综合类 | 1524篇 |
化学工业 | 1666篇 |
金属工艺 | 1004篇 |
机械仪表 | 901篇 |
建筑科学 | 3387篇 |
矿业工程 | 701篇 |
能源动力 | 376篇 |
轻工业 | 262篇 |
水利工程 | 412篇 |
石油天然气 | 451篇 |
武器工业 | 219篇 |
无线电 | 1008篇 |
一般工业技术 | 2571篇 |
冶金工业 | 388篇 |
原子能技术 | 143篇 |
自动化技术 | 1321篇 |
出版年
2024年 | 72篇 |
2023年 | 226篇 |
2022年 | 379篇 |
2021年 | 489篇 |
2020年 | 530篇 |
2019年 | 488篇 |
2018年 | 469篇 |
2017年 | 616篇 |
2016年 | 598篇 |
2015年 | 599篇 |
2014年 | 823篇 |
2013年 | 937篇 |
2012年 | 1056篇 |
2011年 | 1171篇 |
2010年 | 872篇 |
2009年 | 887篇 |
2008年 | 828篇 |
2007年 | 890篇 |
2006年 | 826篇 |
2005年 | 691篇 |
2004年 | 514篇 |
2003年 | 445篇 |
2002年 | 403篇 |
2001年 | 311篇 |
2000年 | 255篇 |
1999年 | 221篇 |
1998年 | 230篇 |
1997年 | 163篇 |
1996年 | 145篇 |
1995年 | 114篇 |
1994年 | 110篇 |
1993年 | 70篇 |
1992年 | 52篇 |
1991年 | 45篇 |
1990年 | 45篇 |
1989年 | 32篇 |
1988年 | 31篇 |
1987年 | 17篇 |
1986年 | 20篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1959年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
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
2.
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
3.
4.
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
5.
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
6.
预处理工艺对硬质合金与金刚石膜间粘结力的影响 总被引:1,自引:0,他引:1
在两种经不同预处理的硬质合金YG8基底上,采用微波等离子体化学气相沉积法,在微波功率2kW,压强4.0kPa和6.5kPa,CH4和H2流量分别为1.6cm/s和100.0cm/s的条件下生长金刚石薄膜。利用X射线衍射检测了金刚石薄膜是否存在,用拉曼光谱分析了薄膜的质量,用金相显微镜观察了薄膜的洛氏硬度压痕,标定并比较了不同预处理工艺膜与基底的结合力。实验结果表明,不同的预处理方法对于粘结力的影响不大,最主要的因素是钴含量的多少。 相似文献
7.
The aim of this study was to investigate the drug‐loading effects on release and mechanical properties of a scleroglucan gel, with the intention of considering them in delivery systems formulations. The rheological and kinetic properties of a 2 % w/w scleroglucan gel matrix loaded with 0, 0.02, 0.04, 0.06, 0.2 and 0.4 % w/w of theophylline (Th, used as a model drug) were investigated. Rheological measurements were performed in a controlled‐stress rotational‐shear rheometer under isothermal conditions. For theophylline release from the gel a flat Franz cell was used and the kinetic parameters were derived applying a semi‐empirical power law. The influence of scleroglucan molar weight on kinetic and rheological behaviour was also studied. Results suggest two possible effects of drug loading on the gel network: in the 0.04–0.06 % w/w Th range a plasticizing effect and in the 0.2–0.4 % w/w Th range a rigidization effect. In the first range mentioned, the changes in the gel structural properties tested by means of rheological measurements are coincident with changes in drug‐release kinetics. Copyright © 2005 Society of Chemical Industry 相似文献
8.
Reinforced concrete slabs are among the most common structural elements. In spite of the large number of slabs designed and built, the effect of their details on their behavior under impact loads are not always appreciated or properly taken into account. This experimental study was aimed at understanding the dynamic behavior of structural concrete slabs under impact loading to improve the state of the art of protective design. This study investigated the effects of different types of slab reinforcements and the applied impact loads on the dynamic response and behavior of reinforced concrete slabs. 相似文献
9.
The present study is an investigation on the behaviors of concrete-filled thin-walled steel tubular members subjected to combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. ABAQUS software is used in this paper for the finite element analysis (FEA). A comparison of results calculated using this modeling shows generally good agreement with test results. The FEA modeling is then used to investigate the influence of important parameters that determine the ultimate strength of the composite members under combined loading, such as compression and torsion, bending and torsion, compression, bending and torsion. The parametric studies provide information for the development of formulae for calculating the ultimate strength of the composite members subjected to combined loading. 相似文献
10.
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