全文获取类型
收费全文 | 718篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 92篇 |
金属工艺 | 18篇 |
机械仪表 | 6篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 53篇 |
轻工业 | 19篇 |
水利工程 | 15篇 |
石油天然气 | 3篇 |
无线电 | 78篇 |
一般工业技术 | 155篇 |
冶金工业 | 198篇 |
自动化技术 | 75篇 |
出版年
2022年 | 13篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 5篇 |
2018年 | 21篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 18篇 |
2013年 | 40篇 |
2012年 | 15篇 |
2011年 | 28篇 |
2010年 | 22篇 |
2009年 | 44篇 |
2008年 | 24篇 |
2007年 | 29篇 |
2006年 | 22篇 |
2005年 | 12篇 |
2004年 | 12篇 |
2003年 | 16篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 19篇 |
1997年 | 12篇 |
1996年 | 20篇 |
1995年 | 17篇 |
1994年 | 17篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 28篇 |
1988年 | 20篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 6篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 4篇 |
排序方式: 共有732条查询结果,搜索用时 15 毫秒
661.
K. Balachandar V. Subramanya Sarma Bhanu Pant G. Phanikumar 《Metallurgical and Materials Transactions A》2009,40(11):2685-2693
Microstructure and mechanical properties of gas-tungsten-arc (GTA)–welded Ti-15V-3Cr-3Sn-3Al alloy in direct current electrode
negative mode are characterized. The thermal profile was measured during welding with continuous current (CC) and pulsed current
(PC) at different frequencies. A single-step postweld aging of the welded samples at subtransus temperature was attempted
to study precipitation of alpha phase. Two different morphologies of alpha phase are observed along with a partitioning of
alloying elements into the two phases. Processing conditions for higher strength are identified and correlated with the thermal
profile. Microstructure changes due to postweld heat treatment were characterized. 相似文献
662.
The electric power systems of US Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. Circuit breakers (CBs) and fuses are provided at different locations for isolation of faulted loads, generators or distribution system from unfaulted portions of the system. These faults could be due to widespread system fault resulting from battle damage or material casualties of individual loads or cables. After the faults and subsequent isolation of the faults, there will be unfaulted sections that are left without supply. Fast restoration of supply to these unfaulted sections of the SPS is necessary for system survivability, This paper presents a new method to reconfigure the network to restore service to unfaulted sections of the system. The problem is formulated as a variation of fixed charge network flow problem. The method is illustrated using various case studies on a small power system with similar topology to a shipboard power system 相似文献
663.
Zachary K. Sweeney Dr. Joshua J. Kennedy‐Smith Dr. Jeffrey Wu Nidhi Arora J. Roland Billedeau James P. Davidson Dr. Jennifer Fretland Dr. Julie Q. Hang Dr. Gabrielle M. Heilek Dr. Seth F. Harris Dr. Donald Hirschfeld Petra Inbar Hassan Javanbakht Dr. Jesper A. Jernelius Dr. Qingwu Jin Yu Li Weiling Liang Ralf Roetz Keshab Sarma Dr. Mark Smith Dr. Dimitrio Stefanidis Dr. Guoping Su Dr. Judy M. Suh Armando G. Villaseñor Michael Welch Fang‐Jie Zhang Dr. Klaus Klumpp Dr. 《ChemMedChem》2009,4(1):88-99
664.
Preface to the focus theme section: ‘Internet of things’ 总被引:1,自引:0,他引:1
665.
Angshuman Nag Sameer Sapra Subhra Sen Gupta Ankita Prakash Ajit Ghangrekar N. Periasamy D. D. Sarma 《Bulletin of Materials Science》2008,31(3):561-568
We have synthesized Mn-doped CdS nanocrystals (NCs) with size ranging from 1.8–3 nm. Photoluminescence (PL) spectra of the
doped NCs differ from that of the undoped NCs with an additional peak due to Mn d-d transitions. Electron paramagnetic resonance spectra along with X-ray absorption spectroscopy and PL spectra confirm the
incorporation of Mn in the CdS lattice. The fact that emissions from surface states and the Mn d levels occur at two different energies, allowed us to study the PL lifetime decay behaviour of both kinds of emissions. 相似文献
666.
The solution of carrier diffusion equations typically associated with semiconductor optical devices has been achieved by combining a function expansion scheme, using the Hermite-Gauss functions as the basis set, with the collocation numerical procedure. Results for a wide range of cases obtained by this new scheme compare very favorably with those calculated with other methods. Not only is the present process computationally fast and efficient, but it has the added attraction of providing the basis for conveniently solving also the nonlinear electromagnetic wave equation for the self-consistent modeling of such devices 相似文献
667.
N. H. Mohan L. Ammayappan D. K. Sarma S. Debnath M. K. Tamuli 《Journal of Natural Fibers》2017,14(4):459-465
Hair fiber is a key by-product of humane slaughter of pigs with considerable economic value. In the present study, we investigated the thermal properties of pig hair fiber using Differential Scanning Calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC curve showed a broad endotherm (around 50–80°C) initially, followed by denaturation doublet peaks (229°C and 239°C) and finally a pyrolysis endotherm. The melting enthalpy of pig hair fiber was 9.93 J/g on dry basis. During TGA, distinct phases of initial weight loss due to loss of moisture and later through thermal degradation of protein around 238–240°C were observed. Mean thermal insulation and conductivity values of pig hair fiber were 0.068 ± 0.004 m2K/W and 0.029 ± 0.003 W/m/K, respectively. The thermal characteristics of pig hair fiber were similar to other keratin fibers of animal origin. 相似文献
668.
Different compositions of lithium aluminum phosphate glasses were prepared by melt quenching technique. The best bulk conductivity
achieved by the sample G3, (28 mol% of lithium oxide). Further, the investigation extended by crystallizing the G3 sample at different temperatures, 200 °C (GC200), 300 °C(GC300), 400 °C (GC400), and 500 °C (GC500). The electrical measurements for all the glasses and glass ceramics were carried out in the frequency range of 1–105 Hz and at a temperature range of 393–513 K by the impedance spectroscopy. The variation of conductivity with frequency of
the samples was explained in the light of different valency states of aluminum ions. AC conductivity data are fitted to a
power law equation. Scaled spectra for ac conductivity and modulus data suggested that the present glass samples follow temperature
independent conductivity distribution relaxation mechanism. 相似文献
669.
Acetate and butyrate as substrates for hydrogen production through photo-fermentation: Process optimization and combined performance evaluation 总被引:1,自引:1,他引:0
S. Srikanth S. Venkata Mohan M. Prathima Devi Dinakar Peri P.N. Sarma 《International Journal of Hydrogen Energy》2009,34(17):7513
Organic acids viz., acetate and butyrate were evaluated as primary substrates for the production of biohydrogen (H2) through photo-fermentation process using mixed culture at mesophilic temperature (34 °C). Experiments were performed by varying parameters like operating pH, presence/absence of initiator substrate (glucose) and vitamin solution, type of nitrogen source (mono sodium salt of glutamic acid and amino glutamic acid) and gas (nitrogen/argon) used to create anaerobic microenvironment. Experimental data showed the feasibility of H2 production along with substrate degradation utilizing organic acids as metabolic substrate but was found to be dependent on the process parameters evaluated. Maximum specific H2 production and substrate degradation were observed with acetic acid [3.51 mol/Kg CODR-day; 1.22 Kg CODR/m3-day (92.96%)] compared to butyric acid [3.33 mol/Kg CODR-day; 1.19 Kg CODR/m3-day (88%)]. Higher H2 yield was observed under acidophilic microenvironment in the presence of glucose (co-substrate), mono sodium salt of glutamic acid (nitrogen source) and vitamins. Argon induced microenvironment was observed to be effective compared to nitrogen induced microenvironment. Combined process efficiency viz., H2 production and substrate degradation was evaluated employing data enveloping analysis (DEA) methodology based on the relative efficiency. Integration of dark fermentation with photo-fermentation appears to be an economically viable route for sustainable biohydrogen production if wastewater is used as substrate. 相似文献
670.
H.S. Jayasinghearachchi Sneha Singh Priyangshu M. Sarma Anil Aginihotri Banwari Lal 《International Journal of Hydrogen Energy》2010
The present study investigated hydrogen production potential of novel marine Clostridium amygdalinum strain C9 isolated from oil water mixtures. Batch fermentations were carried out to determine the optimal conditions for the maximum hydrogen production on xylan, xylose, arabinose and starch. Maximum hydrogen production was pH and substrate dependant. The strain C9 favored optimum pH 7.5 (40 mmol H2/g xylan) from xylan, pH 7.5–8.5 from xylose (2.2–2.5 mol H2/mol xylose), pH 8.5 from arabinose (1.78 mol H2/mol arabinose) and pH 7.5 from starch (390 ml H2/g starch). But the strain C9 exhibited mixed type fermentation was exhibited during xylose fermentation. NaCl is required for the growth and hydrogen production. Distribution of volatile fatty acids was initial pH dependant and substrate dependant. Optimum NaCl requirement for maximum hydrogen production is substrate dependant (10 g NaCl/L for xylose and arabinose, and 7.5 g NaCl/L for xylan and starch). 相似文献