全文获取类型
收费全文 | 870篇 |
免费 | 22篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 11篇 |
综合类 | 1篇 |
化学工业 | 279篇 |
金属工艺 | 38篇 |
机械仪表 | 13篇 |
建筑科学 | 21篇 |
矿业工程 | 1篇 |
能源动力 | 24篇 |
轻工业 | 41篇 |
水利工程 | 4篇 |
无线电 | 69篇 |
一般工业技术 | 161篇 |
冶金工业 | 114篇 |
原子能技术 | 6篇 |
自动化技术 | 114篇 |
出版年
2023年 | 3篇 |
2022年 | 21篇 |
2021年 | 29篇 |
2020年 | 23篇 |
2019年 | 14篇 |
2018年 | 21篇 |
2017年 | 12篇 |
2016年 | 39篇 |
2015年 | 14篇 |
2014年 | 30篇 |
2013年 | 42篇 |
2012年 | 27篇 |
2011年 | 42篇 |
2010年 | 32篇 |
2009年 | 47篇 |
2008年 | 37篇 |
2007年 | 32篇 |
2006年 | 32篇 |
2005年 | 27篇 |
2004年 | 15篇 |
2003年 | 24篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 26篇 |
1999年 | 18篇 |
1998年 | 17篇 |
1997年 | 19篇 |
1996年 | 28篇 |
1995年 | 19篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 12篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 12篇 |
1977年 | 2篇 |
1974年 | 5篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有897条查询结果,搜索用时 0 毫秒
11.
The liquidus surface and tie-lines in the iron-cobalt-sulfur ternary system have been determined between 1473 and 1623 K.
The experiments were conducted by equilibrating the liquid sulfide phase with the metallic alloy phase. The liquid sulfide
phase was sampled and chemically analyzed. The alloy phase was analyzed by electron microprobe. Combining the present results
with the available literature data, the thermodynamic properties of this system were calculated. 相似文献
12.
G. V. K. Puvvada R. Sridhar V. I. Lakshmanan 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(8):38-41
This paper examines in detail the thermodynamics and application of chloride metallurgy for the extraction of precious metals,
such as gold and silver, and platinum-group metals. The advantages with regard to the solubilities of metal ion species and
their reduction potentials in chloride media are discussed with examples. The use of chloride media for the extraction of
platinum-group metals from spent autocatalysts and for the production of high-purity pigment-grade TiO2 and titanium metal from ilmenite feed stocks is discussed in the case studies provided.
For more information, contact V.I. Lakshmanan, Process Research Ortech, 2395 Speakman Dr., Mississauga, ON, L5K 1B3 Canada;
(905) 822-4941; fax (905) 822-9537. 相似文献
13.
Seung Beom Cho Sridhar Venigalla James H. Adair † 《Journal of the American Ceramic Society》1996,79(1):88-96
Phase-pure, monodispersed, hexagonal plates of single-crystal α-alumina (∼ 2 μm wide and ∼0.5 μm thick) have been prepared via precipitation by treating an aluminum hydrous oxide precursor in 1,4-butanediol at 300°C under autogenous vapor pressure. Present work shows that KOH is the only reagent that precipitates an aluminum hydrous oxide precursor suitable to synthesize α-alumina in 1,4-butanediol solution. In contrast, the use of NaOH or NH4 OH as the precipitating reagent for the precursor material does not yield the alpha phase. The solution pH at which the precursor materials are precipitated is also a critical factor for the formation of α-Al2 O3 . Phase-pure α-alumina powders were also only synthesized from the aluminum hydrous oxide precursors precipitated in the pH range from 10 to 10.5. The results of X-ray diffraction and scanning electron microscopy indicate that longer reaction times promote the phase transformation from the intermediate boehmite phase to α-alumina. The complete transformation from boehmite to α-alumina requires reaction times of about 12 h. 相似文献
14.
Sridhar Komarneni Bharat L. Newalkar Dongsheng Li Tarun Gheyi Christina L. Lopano Peter J. Heaney Jeffrey E. Post 《Journal of Porous Materials》2003,10(4):243-248
Several nitrate containing anionic clays were synthesized at different temperatures and the kinetics of NO3
– release were determined to test their suitability as slow-release N fertilizers. A sample (Mg:Al = 2:1) synthesized at 60°C with smaller particle size released 75, 86 and 100% of its NO3
– in 1, 3 and 7 days, respectively when equilibrated with a simulated soil solution. On the other hand, the 175°C/2 hrs sample with larger particle size released 65, 77 and 84% of its nitrate in 1, 3 and 7 days, respectively. Another anionic clay (synthesized at 175°C/24 hrs) of higher charge density (Mg:Al = 2:1) containing NO3
– was equilibrated with a 0.012 N NaCl or Na2CO3 to test the role of different anions in releasing the NO3
– anion from the interlayers. The results showed that Cl– released more NO3
– than did CO3
2– from this anionic clay after all the treatment times probably as a result of the CO3
2– anion blocking the release of NO3
– from the interior of the crystals. When a lower charge density (Mg:Al = 3:1) sample (synthesized at 175°C/48 hrs) was equilibrated with 0.02N solution of anions the release of nitrate was as follows: Cl– < F– < SO4
= CO3
2–. These results suggest that the divalent SO4
= and CO3
2– anions are more effective in the release of NO3
– from this lower charge density anionic clay. Time-resolved structural analysis of NO3
– exchange with CO3
2– in the above anionic clay using synchrotron x-ray diffraction showed that ion exchange is rapid because of small crystal size and lower charge density. Thus the release of NO3
– from anionic clays is an interplay among the type of anions present in soil solution, their concentration, pH of soil solution, the charge density and crystal size of anionic clay etc. 相似文献
15.
Mullite formation process has been studied in stoichiometric mullite (3Al2O3·2SiO2) diphasic gel containing large boehmite (1 m) and small silica (10 nm) particles. It has been found that initial mullitization did not take place inside the silica phase (cristobalite), but took place in the defect -alumina phase. -alumina was stabilized by silica when the temperature was below 1350°C. At temperatures above 1350°C, mullite crystallized directly. It was suggested that silica diffused into the pores (<1.8 nm) of -alumina and prevented the collapse of -alumina pore structure. On the other hand, when silica was not present, the pore structure of -alumina collapsed and -alumina crystallized at 1100°C. Porous mullite ceramics were obtained by using special diphasic gels containing large boehmite and small silica particles. 相似文献
16.
Dense blend membranes were prepared by blending hydrophilic polymers poly(vinyl alcohol) (PVA) and poly(ethyleneimine) (PEI), which were then crosslinked by glutaraldehyde (GA) in a mixture of solvents under the catalysis of hydrochloric acid (HCl) for the dehydration of tetrahydrofuran (THF) by pervaporation. The effect of experimental parameters such as feed water concentration, permeate pressure, and membrane thicknesses on permeate parameters, i.e., flux and selectivity were determined with feed water concentration less than 40 wt %. The membranes were found to have good potential for breaking the azeotrope of 94 wt % THF with a flux of 1.072 and 0.376 kg/m2 h for plane PVA/PEI and crosslinked PVA/PEI blend membrane, which exhibited high selectivity of 156 and 579 respectively. Selectivity was found to improve with decreasing feed water concentration and increasing membrane thickness, whereas flux decreased correspondingly. High permeate pressure causes a reduction in both flux and selectivity. These effects were clearly elucidated with the aid of the known relationship among plasticization effect, degree of swelling, permeate pressure, and feed water concentration. These blend membranes were also subjected to sorption studies to evaluate the extent of interaction and degree of swelling in pure as well as binary feed mixtures. Further ion exchange capacity studies were carried out for all the crosslinked and uncrosslinked membranes to determine the total number of interacting groups present in the membranes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1152–1161, 2006 相似文献
17.
Weiping Ma Paul W. Brown Sridhar Komarneni 《Journal of the American Ceramic Society》1996,79(6):1707-1710
Tobermorites were synthesized from oxides and from fly ashes under mild hydrothermal conditions. The bulk compositions of the ash-based formulations were adjusted to give the same [Ca]/[Si + Al] ratio as for the oxides. Selective Cs and Sr exchange with these tobermorites was measured. Compared to those prepared from the oxides and from class C fly ash, the tobermorites obtained from class F fly ash exhibited superior Cs and Sr selective properties. This is apparently a result of more extensive Al incorporation with class F fly ash. For example, tobermorite synthesized from class F fly ash exhibited a cesium K d (mL/g) of 3826 while those prepared from oxides and from class C fly ash showed K d values of 1112 and 796, respectively, under the same conditions. These results suggest that fly ash waste materials can be converted into tobermorite, which can serve as a resource in the separation, immobilization, and disposal of radioactive species such as Cs and Sr. 相似文献
18.
Stabilization of -alumina phase by silica was studied in nanocomposite (diphasic) alumina-silica gels by XRD and BET surface areas measurements. Five wt.% of silica (22 nm particles) increased the crystallization temperature of to -alumina by about 100°C from boehmite (10 nm particles) derived alumina. Stabilization of -alumina was caused by the formation of intimate contact (Al-O-Si) between components by diffusion of silica into the defect alumina structure.Also with the Department of Agronomy. 相似文献
19.
Sridhar Komarneni V C. Menon Q. H. Li Rustum Roy F. Ainger 《Journal of the American Ceramic Society》1996,79(5):1409-1412
Microwave-hydrothermal (M-H) processing was compared with conventional-hydrothermal (C-H) processing in the crystallization of BiFeO3 and CsAl2 PO6 phases. The presence of the microwave field led to accelerated kinetics of the crystallization of both these phases as detected by powder X-ray diffraction. The acceleration of reaction rates under microwave field is expected to lead to energy savings during ceramic processing. 相似文献
20.
A. K. Sahu G. Selvarani S. Pitchumani P. Sridhar A. K. Shukla 《Journal of Applied Electrochemistry》2007,37(8):913-919
Incorporation of silica particles through a sol-gel process into the anode-catalyst layer with a sol-gel modified Nafion-silica
composite membrane renders easy retention of back-diffused water from the cathode to anode through the composite membrane
electrolyte, increases the catalyst-layer wettability and improves the performance of the Polymer Electrolyte Fuel Cell (PEFC)
while operating under relative humidity (RH) values ranging between 18% and 100% with gaseous hydrogen and oxygen reactants
at atmospheric pressure. A peak power density of 300 mW cm−2 is achieved at a load current-density value of 1200 mA cm−2 for the PEFC employing a sol-gel modified Nafion-silica composite membrane and operating at 18% RH. Under similar operating
conditions, the PEFC with a Membrane Electrode Assembly (MEA) comprising Nafion-silica composite membrane with silica in the
anode-catalyst layer delivers a peak power density of 375 mW cm−2. By comparison, the PEFC employing commercial Nafion membrane fails to deliver satisfactory performance at 18% RH due to
the limited availability of water at its anode, acerbated electro-osmotic drag of water from anode to cathode and insufficient
water back diffusion from cathode to anode causing the MEA to dehydrate. 相似文献