全文获取类型
收费全文 | 6185篇 |
免费 | 185篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 83篇 |
综合类 | 8篇 |
化学工业 | 1206篇 |
金属工艺 | 195篇 |
机械仪表 | 182篇 |
建筑科学 | 134篇 |
矿业工程 | 7篇 |
能源动力 | 448篇 |
轻工业 | 547篇 |
水利工程 | 73篇 |
石油天然气 | 88篇 |
武器工业 | 2篇 |
无线电 | 680篇 |
一般工业技术 | 1314篇 |
冶金工业 | 776篇 |
原子能技术 | 61篇 |
自动化技术 | 589篇 |
出版年
2023年 | 103篇 |
2022年 | 203篇 |
2021年 | 238篇 |
2020年 | 212篇 |
2019年 | 187篇 |
2018年 | 278篇 |
2017年 | 240篇 |
2016年 | 226篇 |
2015年 | 152篇 |
2014年 | 221篇 |
2013年 | 460篇 |
2012年 | 241篇 |
2011年 | 304篇 |
2010年 | 228篇 |
2009年 | 231篇 |
2008年 | 229篇 |
2007年 | 172篇 |
2006年 | 162篇 |
2005年 | 102篇 |
2004年 | 88篇 |
2003年 | 91篇 |
2002年 | 76篇 |
2001年 | 56篇 |
2000年 | 72篇 |
1999年 | 86篇 |
1998年 | 218篇 |
1997年 | 145篇 |
1996年 | 127篇 |
1995年 | 96篇 |
1994年 | 81篇 |
1993年 | 83篇 |
1992年 | 62篇 |
1991年 | 61篇 |
1990年 | 49篇 |
1989年 | 60篇 |
1988年 | 46篇 |
1987年 | 43篇 |
1986年 | 52篇 |
1985年 | 66篇 |
1984年 | 48篇 |
1983年 | 56篇 |
1982年 | 57篇 |
1981年 | 56篇 |
1980年 | 50篇 |
1979年 | 44篇 |
1978年 | 26篇 |
1977年 | 39篇 |
1976年 | 46篇 |
1974年 | 28篇 |
1973年 | 23篇 |
排序方式: 共有6393条查询结果,搜索用时 0 毫秒
11.
M. E. Ladhabhoy M. M. Sharma 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1970,20(9):274-280
The kinetics of absorption of oxygen by 2-ethylhexaldehyde dissolved in 2-ethylhexanoic acid at concentrations up to 1.38 × 10?3 mole/cm3 (20 wt.-%), in the presence of manganese acetate, was studied in a stirred cell and in bubble and packed bubble columns. Diffusion of oxygen was found to play a major role. The reaction was first order in oxygen and second order with respect to the aldehyde, and the overall third-order rate constant was found to be 2.98 × 107 cm6 mole?2 sec?1 at 30°. The effect of cobaltous acetate on the specific rate of absorption of oxygen was also studied and manganese acetate was found to be the better catalyst. 相似文献
12.
The aim of this project was to investigate the potential of reducing number of mixers in the biological treatment process and thereby achieve energy and economical savings and contribute to cleaner environment. The project was carried out at Avedoere wastewater treatment plant and a full scale investigation was conducted to study the effect of reduced mixing on flow velocity, suspended solid sedimentation, concentration gradients of oxygen and SS with depth and treatment efficiency. The only negative effect observed was on flow velocity; however the velocity was above the critical velocity. The plant has been operating with 50% of its designed number of mixers since September 2007 and long term results also confirm that reduced mixing did not have any negative effect on treatment efficiency. The estimated yearly electricity saving is 0.75 GWh/year. 相似文献
13.
Decentralised water supply systems are becoming increasingly affordable and commonplace in Australia and have the potential to alleviate urban water shortages and reduce pollution into natural receiving marine and freshwater streams. Learning processes are necessary to support the efficient implementation of decentralised systems. These processes reveal the complex socio-technical and institutional factors to be considered when developing an enabling environment supporting decentralised water and wastewater servicing solutions. Critical to the technological transition towards established decentralised systems is the ability to create strategic and adaptive capacity to promote learning and dialogue. Learning processes require institutional mechanisms to ensure the lessons are incorporated into the formulation of policy and regulation, through constructive involvement of key government institutions. Engagement of stakeholders is essential to the enabling environment. Collaborative learning environments using systems analysis with communities (social learning) and adaptive management techniques are useful in refining and applying scientists' and managers' knowledge (knowledge management). 相似文献
14.
This paper settles a question about prudent vacillatory identification of languages. Consider a scenario in which an algorithmic deviceM is presented with all and only the elements of a languageL, andM conjectures a sequence, possibly infinite, of grammars. Three different criteria for success ofM onL have been extensively investigated in formal language learning theory. IfM converges to a single correct grammar forL, then the criterion of success is Gold's seminal notion ofTxtEx-identification. IfM converges to a finite number of correct grammars forL, then the criterion of success is calledTxtFex-identification. Further, ifM, after a finite number of incorrect guesses, outputs only correct grammars forL (possibly infinitely many distinct grammars), then the criterion of success is known asTxtBc-identification. A learning machine is said to beprudent according to a particular criterion of success just in case the only grammars it ever conjectures are for languages that it can learn according to that criterion. This notion was introduced by Osherson, Stob, and Weinstein with a view to investigating certain proposals for characterizing natural languages in linguistic theory. Fulk showed that prudence does not restrictTxtEx-identification, and later Kurtz and Royer showed that prudence does not restrictTxtBc-identification. This paper shows that prudence does not restrictTxtFex-identification. 相似文献
15.
Baranwal Alok Kumar Sharma Shashibhushan Roy Sanjay Dhar Kundu Sumit 《Wireless Personal Communications》2022,124(2):1281-1296
Wireless Personal Communications - This paper proposes and analyses the power allocation coefficient normalization for successive interference cancellation in power-domain non-orthogonal multiple... 相似文献
16.
The present article is concerned with the investigation of disturbances in a homogeneous transversely isotropic thermoelastic rotating medium with two temperatures, in the presence of the combined effects of Hall currents and magnetic field. The formulation is applied to the thermoelasticity theories developed by Green-Naghdi theories of type-II and type-III. Laplace and Fourier transform techniques are applied to solve the problem. The analytical expressions of displacements, stress components, temperature change, and current density components are obtained in the transformed domain. A numerical inversion technique has been applied to obtain the results in the physical domain. Numerical simulated results are depicted graphically to show the effect of Hall current and two temperatures on resulting quantities. Some special cases are also deduced from the present investigation. 相似文献
17.
18.
Chromatic effects of radial gradient-index materials have been analyzed, and several important conclusions have been derived in terms of material dispersion data. The use of Buchdahl dispersion data, both for base glass materials and ion-exchange pairs, provides some simple relationships for chromatic aberration and helps in selecting suitable materials for producing achromatic radial gradient-index lenses. 相似文献
19.
A high-precision method to study the dynamics of two-fluid interfaces using an optical tweezer and a phase-sensitive detection technique are described. The disturbances set up at the interface are studied by analyzing the motion of an optically trapped particle in the bulk of the fluid, i.e., away from the interface. The usefulness of the technique is demonstrated for the well-known problem of a horizontally vibrated sessile liquid drop. The vibrational modes of the liquid drop excited by sinusoidally vibrating the support in a horizontal plane appear as resonances in the motion of the trapped particle. The nature of the resonance is studied in detail by measuring the real part, the imaginary part, and the phase response of the motion of the particle as a function of the "effective" size of the liquid drop. Excellent quantitative agreement with the theoretically predicted values of the eigenfrequencies and damping of the surface modes is obtained. 相似文献
20.