全文获取类型
收费全文 | 1685篇 |
免费 | 47篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 283篇 |
金属工艺 | 44篇 |
机械仪表 | 91篇 |
建筑科学 | 49篇 |
矿业工程 | 4篇 |
能源动力 | 60篇 |
轻工业 | 64篇 |
水利工程 | 5篇 |
石油天然气 | 9篇 |
无线电 | 215篇 |
一般工业技术 | 393篇 |
冶金工业 | 236篇 |
原子能技术 | 60篇 |
自动化技术 | 210篇 |
出版年
2023年 | 18篇 |
2022年 | 31篇 |
2021年 | 37篇 |
2020年 | 34篇 |
2019年 | 29篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 35篇 |
2015年 | 23篇 |
2014年 | 48篇 |
2013年 | 104篇 |
2012年 | 60篇 |
2011年 | 92篇 |
2010年 | 88篇 |
2009年 | 70篇 |
2008年 | 73篇 |
2007年 | 63篇 |
2006年 | 59篇 |
2005年 | 34篇 |
2004年 | 37篇 |
2003年 | 41篇 |
2002年 | 34篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 21篇 |
1998年 | 39篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 32篇 |
1994年 | 29篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 29篇 |
1990年 | 31篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 26篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 30篇 |
1975年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有1742条查询结果,搜索用时 15 毫秒
81.
82.
Our continuing research on the preparation, characterization, materials properties, and biodegradability of polylactide (PLA)/organically modified layered silicate (OMLS) nanocomposites has yielded results on PLA/montmorillonite nanocomposites. Montmorillonite (mmt) modified with dimethyldioctadecylammonium cation was used as an OMLS for nanocomposite preparation. The internal structure of nanocomposites on the nanometer scale was established with the use of wide-angle X-ray diffraction patterns and transmission electron micrographic observation. All nanocomposites exhibited significant improvement in crystallization behavior, mechanical properties, flexural properties, heat distortion temperature, and O2 gas permeability when compared with pure PLA. 相似文献
83.
Permeation enhancers for transdermal drug delivery 总被引:7,自引:0,他引:7
The transdermal route has been recognized as one of the highly potential routes of systemic drug delivery and provides the advantage of avoidance of the first-pass effect, ease of use and withdrawal (in case of side effects), and better patient compliance. However, the major limitation of this route is the difficulty of permeation of drug through the skin. Studies have been carried out to find safe and suitable permeation enhancers to promote the percutaneous absorption of a number of drugs. The present review includes the classification of permeation enhancers and their mechanism of action; thus, it will help in the selection of a suitable enhancer(s) for improving the transdermal permeation of poorly absorbed drugs. 相似文献
84.
This cross-cultural research study aimed to explore the relationship of stress and coping with psychological illness or symptoms among university students in Canada and India. The predictor variables were stress (hassles and life experience), 8 ways of coping (Folkman & Lazarus, 1988), and selected personal-social variables, namely, locus of control, self-esteem, and social support. The criterion variables were 9 psychological symptoms of the Brief Symptom Inventory (BSI; Derogatis & Spencer, 1982). The results revealed that the Indian students reported more psychological symptoms compared to the Canadian students. Stepwise multiple-regression analyses also revealed considerable differences between the 2 samples with respect to the contribution of predictor variables in accounting for variance in the BSI scales. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
Metalloids normally get transferred at the interface of metal droplets passing through the slag system in the dropping zone and at the slag‐metal interface in the hearth zone in the lower region of a blast furnace. In these high temperature processes, the mass transport being the rate‐controlling factor, the viscosity of the slag system determines the kinetics of the refining reactions accompanied by mass and heat transfer at the metal droplets and slag interface. Slag systems generally possess random network structures comprising internal regions of weak ordering. The presence of these regions may result in non‐Newtonian behaviour of the slag. The rheological characteristics of a fluid relating to its network structure is expressed in terms of the indices consistency (k') and flow behaviour (n'). The extent of metalloids presence in hot metal is subjected to their residence time at the slag‐metal interface. The metal droplet descent through a surrounding fluid system has been studied and a co‐relation between drag Reynolds number and modified Reynolds number has been obtained. This correlation has been used to determine the drag velocity of a metal droplet falling through a slag system and the residence time distribution (RTD) of the metalloids at the slag‐metal interface in the lower region of the blast furnace. 相似文献
86.
Wang J.M. Sukhwani B. Padmanabhan U. Dongsheng Ma Sinha K. 《IEEE transactions on circuits and systems. I, Regular papers》2007,54(6):1293-1304
New nanotechnology-based devices are being researched to replace CMOS devices in order to overcome CMOS technology's scaling limitations. However, many such devices exhibit nonmonotonic I-V characteristics and uncertain properties which lead to the negative differential resistance (NDR) problem and the chaotic performance. This paper proposes two new circuit simulation approaches that can effectively simulate nanotechnology devices with uncertain input sources and negative differential resistance problem. A new tool called NanoSim-RTD is developed based on the proposed new simulation techniques. The experimental results show a speedup of 1.48-37.1 times when compared with existing simulators. Further, this paper demonstrates a new way to design delay-insensitive nanocircuits, and the designs can be verified by using NanoSim-RTD. 相似文献
87.
Dola Sinha Pradip Kumar Sadhu Nitai Pal Nirmal Baran Hui 《Neural computing & applications》2013,22(7-8):1379-1386
The present paper deals with modeling of AC resistance of twisted litz wires used for high-frequency inverter-fed induction cooker. Several traditional approaches are available, most of which have concentrated in deriving the analytical relationships between the AC resistances with the parameters of the wire. However, it is very difficult to get the exact relationship, due to several reasons. An attempt is made in this paper to model the AC resistance using a three-layered feed-forward Neural Network. For this purpose, four inputs (wire type, number of strand, number of spiral turn and operating frequency) and one output as AC resistance have been considered. Since the performance of Neural Network alone might not be optimal; it is optimized using a binary-coded Genetic Algorithm. Performances of the proposed approach were compared with the method of AC resistance computation proposed by Ferreira. Genetic-neural system has given a very close accuracy, and the computational complexity was found to be very low. Thus, it is suitable for online implementations. 相似文献
88.
We have investigated laser action in a binary mixture of dyes, Rh-6G and DCM, resulting in tunable laser emission over an extended frequency region. The two dyes absorb the same pump radiation but fluoresce over frequency ranges that are shifted with respect to each other, thereby resulting in extended tunability. Following a time-dependent analysis of a rate-equation model that describe the operation of such a laser, theoretical estimates for optimum dye concentrations and the corresponding extension of the laser tuning range have been obtained. 相似文献
89.
PEEK, an engineering polymer with many advantages such as lightweight, high thermal stability, high strength coupled with toughness, has often been used as a substitute for metals in applications such as bearings, piston parts, pumps and even biomaterials. However, it shows high coefficient of friction which results in high wear rate when used in tribological applications. This paper seeks to solve tribological problems of high friction and wear for PEEK by applying an ultrathin layer of perfluoropolyether (PFPE) and Multiply-Alkylated Cyclopentane (MAC) lubricants on the surface of PEEK. Results obtained from tribological tests conducted showed that for highly improved tribological performance, there is an optimal initial surface roughness of PEEK surface and lubricant concentration or the thickness of the coatings for both PFPE and MAC lubricant. Also, MAC performs better compared to PFPE for thinner films. 相似文献
90.
Priyanka Kamble Prithwish Sinha Roy Arvind Ananthanarayanan Jayesh G Shah Gopalakrishnan Sugilal 《分离科学与技术》2020,55(9):1603-1610
ABSTRACTA new composite of crystalline silicotitanate (CST) has been synthesized for the sequestration of Cs and Sr from low-level liquid waste generated in the nuclear industry. The product characterization using X-RAY DEFRACTION (XRD) and Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of CST crystals in the composite. Sorption studies carried out under various test conditions showed that the composite has high affinity for both Cs and Sr. Results of structural characterization of Cs and Sr-loaded CST indicated that the overall structural integrity remained intact after substitution of Na+ by Cs+ or Sr2+. The exceedingly good Cs and Sr sorption performance displayed by the CST composite will find applications in the treatment of nuclear waste. 相似文献