全文获取类型
收费全文 | 901篇 |
免费 | 29篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 37篇 |
综合类 | 2篇 |
化学工业 | 334篇 |
金属工艺 | 24篇 |
机械仪表 | 10篇 |
建筑科学 | 32篇 |
能源动力 | 43篇 |
轻工业 | 85篇 |
水利工程 | 3篇 |
无线电 | 33篇 |
一般工业技术 | 170篇 |
冶金工业 | 65篇 |
原子能技术 | 19篇 |
自动化技术 | 76篇 |
出版年
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 17篇 |
2018年 | 11篇 |
2017年 | 15篇 |
2016年 | 30篇 |
2015年 | 8篇 |
2014年 | 19篇 |
2013年 | 48篇 |
2012年 | 33篇 |
2011年 | 57篇 |
2010年 | 37篇 |
2009年 | 50篇 |
2008年 | 46篇 |
2007年 | 41篇 |
2006年 | 44篇 |
2005年 | 30篇 |
2004年 | 29篇 |
2003年 | 34篇 |
2002年 | 27篇 |
2001年 | 14篇 |
2000年 | 22篇 |
1999年 | 22篇 |
1998年 | 32篇 |
1997年 | 23篇 |
1996年 | 22篇 |
1995年 | 20篇 |
1994年 | 17篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 11篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1977年 | 11篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有933条查询结果,搜索用时 781 毫秒
41.
Toshihiro Takaine Mutsumi Tashiro Takahiko Shiina Toshihiro Noda Akira Asaoka 《Soils and Foundations》2010,50(2):245-260
The continuous behaviour of a ground-embankment system from the stage of deformation up to failure was predicted with respect to an actual test embankment that had been constructed in stages on a soft ground made up of peat and calcareous soil. The behaviour prediction was carried out by employing soil-water coupled finite deformation analysis, which also included simulation of the embankment construction process. The information used in the analysis was limited to such things as the results of soil tests on soil materials (peat and calcareous soil) sampled from the ground, including their sensitivity ratios, and the embankment's construction history. The SYS Cam-clay model was used in the constitutive equations of the soils to determine the material constants of the soils and the initial conditions of the ground, and the computations were performed under plane strain conditions. As a result, the computed profiles of W-type ground settlement and of slip surfaces running through the embankment were found to be in good overall agreement with the actual profiles measured at the site. Furthermore, we found that this slippage is attributable to the undrained shear response of the soil elements in the calcareous soil layer, where slippage begins to occur during embankment loading. In other words, the slippage is caused by the rapid softening behaviour caused by the degradation of structure after the effective stress ratio reaches the vicinity of the critical state line. 相似文献
42.
Takuya Orihashi Toshihiro Nakamura Sadao Adachi 《Journal of the American Ceramic Society》2016,99(9):3039-3046
The europium titania materials, pyrochlore Eu2Ti2O7 and orthorhombic Eu2TiO5, were synthesized from a mixture of Eu2O3 and TiO2 using the solid‐state reaction method. The structural and optical properties of these titania materials were investigated using X‐ray diffraction analysis, photoluminescence (PL) analysis, PL excitation (PLE) spectroscopy, and diffuse reflectance spectroscopy. Temperature dependence of the PL intensity was measured between T = 20 and 450 K and analyzed on the basis of various theoretical models. A remarkable increase in the PL intensity with increasing T was observed in these titania materials at higher temperatures, above ~140 K, and well explained by a trap/reservoir model. Interestingly, a dramatic decrease in the electric‐dipole emission component relative to the magnetic‐dipole one was observed in Eu2Ti2O7 above T ~ 140 K. The schematic energy‐level diagram for Eu3+ in the Eu2Ti2O7 host was proposed for the sake of a better understanding of the PL and PLE processes in this type of phosphorescent material. 相似文献
43.
Yugo Kato Satoshi Kimura Toshihiro Kogure Michio Suzuki 《International journal of molecular sciences》2022,23(5)
Specialist bacteria can synthesize nanoparticles from various metal ions in solution. Metal recovery with high efficiency can be achieved by metal-tolerant microorganisms that proliferate in a concentrated metal solution. In this study, we isolated bacteria (Pseudomonas sp. strain KKY-29) from a bacterial library collected from water near an abandoned mine in Komatsu City, Ishikawa Prefecture, Japan. KKY-29 was maintained in nutrient medium with lead acetate and synthesized hydrocerussite and pyromorphite nanoparticles inside the cell; KKY-29 also survived nanoparticle synthesis. Quantitative PCR analysis of genes related to phosphate metabolism showed that KKY-29 decomposed organic phosphorus to synthesize lead phosphate. KKY-29 also deposited various metal ions and synthesized metal nanoparticles when incubated in various metal salt solutions other than lead. The present study considers the development of biotechnology to recover lead as an economically valuable material. 相似文献
44.
A measurement method for an unsteady temperature field by using a Mach-Zehnder interferometer and image processing technique is presented. In this study, the results measured by this method were compared with the calculated results under Reynolds numbers (Re = UL/v) ranging to less than 350 in the steady-state. The unsteady characteristics of the local Nusselt numbers (Nux = αxL/λ) around an elastically vibrating plate were investigated under the conditions that the reduced frequency (N = 1/Ro) ranged from 4.8 to 8.6 and the amplitude of vibration was kept small relative to the plate length. In this study it was clarified that the distributions of the Local Nusselt numbers were observed flutteringly, and that the phase of the time-averaged Nusselt number is delayed compared to the phase of the velocity at the trailing edge. These results indicate that the enhancement of the time-averaged heat transfer coefficient around the vibrating plate depended on the Rossby number. © 1997 Scripta Technica. Inc. Heat Trans Jpn Res. 25 (2): 88–102, 1996 相似文献
45.
Experimental study of impingement cooling by heat sinks with thin longitudinal fins for LSI packages
This paper reports on the impingement cooling characteristics of a heat sink with thin longitudinal fins of 0.2 mm thickness, which are spaced with a fin-pitch in the range 0.5 mm to 2.0 mm. The air cooling of the heat sink comes from a slot-shaped orifice positioned above the heat-sink center. The breadth of the gap between the fin tops and the inlet orifice is in the range 0 mm to 10 mm. The thermal resistance of the thin longitudinal fins used is about 50% to 57% that of the thick longitudinal fins now in commercial use. The cooling performance of the thin-plate fins is almost the same as that of optimally arranged pin-fins with the same total surface area. A maximum value of six times the heat transfer rate of a single flat plate having the same base area was observed for the thin-plate fins. A comparison of cooling performance between impingement and channel flow systems was conducted. The performance of impingement cooling systems is almost unaffected by the breadth of the gap between the fin tops and the inlet orifice (or, for channel cooling, the upper wall). On the other hand, the performance of channel-cooling systems decreases significantly as the gap widens. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(7): 449–459, 1996 相似文献
46.
Yasumasa?Minemoto Shuji?AdachiEmail author Yuji?Shimada Toshihiro?Nagao Toshio?Iwata Yoshie?Yamauchi-Sato Takaya?Yamamoto Tadashi?Kometani Ryuichi?Matsuno 《Journal of the American Oil Chemists' Society》2003,80(7):675-678
The autoxidation processes of the cis-9,trans-11 (c9,t11) and trans-10,cis-12 (t10,c12) isomers of CLA were separately observed at ca. 0% RH and different temperatures. The t10,c12 CLA oxidized faster than the c9,t11 isomer at all tested temperatures. The first half of the oxidation process of t10,c12 CLA obeyed an autocatalytic-type rate expression, but the latter half followed first-order kinetics. On the other hand,
the entire oxidation process of c9,t11 CLA could be expressed by the autocatalytic-type rate expression. The apparent activation energies and frequency factors
for the autoxidation of the isomers were estimated from the rate constants obtained at various temperatures based on the Arrhenius
equation. The apparent activation energies for the CLA isomers were greater than those for the nonconjugated n−6 and n−3 PUFA
or their esters. However, the enthalpyentropy compensation held during the autoxidation of both the CLA and PUFA. This suggested
that the autoxidation mechanisms for the CLA and PUFA were essentially the same. 相似文献
47.
Regiospecific analysis by ethanolysis of oil with immobilized <Emphasis Type="Italic">Candida antarctica</Emphasis> lipase 总被引:1,自引:1,他引:1
Shimada Y Ogawa J Watanabe Y Nagao T Kawashima A Kobayashi T Shimizu S 《Lipids》2003,38(12):1281-1286
A mixture of oil/ethanol (1∶3, w/w) was shaken at 30°C with 4% immobilized Candida antarctica lipase by weight of the reaction mixture. The reaction regiospecifically converted FA at the 1- and 3-positions to FA ethyl
esters, and the lipase acted on C14−C24 FA to a similar degree. The content of 2-MAG reached a maximum after 4 h; the content was 28–29 mol% based on the total amount
of FA in the reaction mixture at 59–69% ethanolysis. Only 2-MAG were present in the reaction mixture during the first 4 h,
and 1(3)-MAG were detected after 7 h. After removal of ethanol from the 4-h reaction mixture by evaporation, 2-MAG were fractionated
by silica gel column chromatography. The contents of FA in the 2-MAG obtained by ethanolysis of several oils coincided well
with FA compositions at the 2-position, which was analyzed by Grignard degradation. It was shown that ethanolysis of oil with
C. antarctica lipase can be applied to analysis of FA composition at the 2-position in TAG. 相似文献
48.
Sterols,methylsterols, and triterpene alcohols in threeTheaceae and some other vegetable oils 总被引:4,自引:0,他引:4
The unsaponifiables from threeTheaceae (Camellia japonica L.,Camellia Sasanqua Thunb., andThea sinensis L.) oils and alfalfa, garden balsam, and spinach seed oils and shea fat were separated into four fractions: sterols, 4-methylsterols,
triterpene alcohols, and less polar compounds by thin layer chromatography. While the sterol fraction was the major one for
the unsaponifiables from alfalfa and spinach seed oils, the triterpene alcohol fraction was predominant for the unsaponifiables
from all other oils. The sterol, 4-methylsterol, and triterpene alcohol fractions were analyzed by gas chromatography. All
the sterol fractions were alike in their compositions, consisting exclusively of Δ7-sterols, such as α-spinasterol and Δ7-stigmastenol as predominant components together with Δ7-avenasterol and 24-methylcholest-7-enol. Obtusifoliol, gramisterol (occasionally accompanied with cycloeucalenol), and citrostadienol,
together with several other unidentified components, were found in the 4-methylsterol fractions from all of the oils except
shea fat. The 4-methylsterol fraction from shea fat showed a characteristic composition containing a large proportion of unidentified
components which had relative retention time greater than that of citrostadienol, while no citrostadienol was detected. β-Amyrin,
lupeol, and butyospermol were major components of the triterpene alcohol fractions from most of the oils, but the fraction
from spinach seed oil contained cycloartenol and 24-methylene-cycloartanol as predominant components. There is a close similarity
in the compositions of unsaponifiables (sterols, 4-methylsterols, and triterpene alcohols) of the threeTheaceae oils. Two sterols, α-spinasterol and Δ7-stigmastenol, and five triterpene alcohols were isolated from tea seed oil. Moreover, five unidentified components beside
parkeol, butyrospermol, α-amyrin, and lupeol were isolated from the triterpene alcohol fraction of shea fat. 相似文献
49.
Keiji Sakaki Toshihiro Yokochi Osamu Suzuki Toshikatsu Hakuta 《Journal of the American Oil Chemists' Society》1990,67(9):553-557
The extraction of oil from fungi (Mortierella ramanniana var.angulispora) was studied using carbon dioxide (CO2), nitrous oxide (N2O), trifluoromethane (CHF3) and sulfur hexafluoride (SF6) under supercritical conditions. The oil solubility was highest in SC-N2O followed by SC-CO2, while both SC-CHF3 and SC-SF6 showed poorer solvent power. The recorded oil solubilities at 333 K and 24.5 MPa were 2.3 wt% in N2O, 0.48 wt% in CO2, 0.0099 wt% in CHF3 and 0.0012 wt% in SF6.
The oil solubilities in SC-N2O and SC-CO2 were measured over the pressure range 15.7–29.4 MPa and at temperatures ranging from 313–353 K. N2O always showed greater solvent power than did CO2 at the same temperature and pressure. The solvent power of a supercritical fluid increases with density at a given temperature,
and increases with temperature at constant density.
The change in neutral lipid composition of the extracted oil with the extraction ratio was measured. Free fatty acids or diglycerides
were extracted more easily than triglycerides or sterol esters. The change in fatty acid composition was also measured. The
proportion of γ-linolenic acid in the extract remained constant throughout the extraction. 相似文献
50.
Akiko?Kawashima Toshihiro?NagaoEmail author Yomi?Watanabe Takashi?Kobayashi Ikuo?Ikeda Yoshio?Tominaga Yuji?Shimada 《Journal of the American Oil Chemists' Society》2004,81(11):1013-1020
TAG (MLM) with medium-chain FA (MCFA) at the 1,3-positions and long-chain FA (LCFA) at the 2-position, and TAG (LMM) with
LCFA at the 1(3)-position and MCFA at 2,3(1)-positions are a pair of TAG regioisomers. Large-scale preparation of the two
TAG regioisomers was attempted. A commercially available FFA mixture (FFA-CLA) containing 9-cis, 11-trans (9c, 11t)- and 10t,12c-CLA was selected as LCFA, and caprylic acid (C8FA) was selected as MCFA. The MLM isomer was synthesized by acidolysis of acyglycerols (AG) containing two CLA isomers with
C8FA: A mixture of AG-CLA/C8 FA (1∶10, mol/mol) and 4 wt% immobilized Rhizomucor miehei lipase was agitated at 30°C for 72 h. The ratio of MLM to total AG was 51.1 wt%. Meanwhile, LMM isomer was synthesized by
acidolysis of tricaprylin with FFA-CLA: A mixture of tricaprylin/FFA-CLA (1∶2, mol/mol) and 4 wt% immobilized R. miehei lipase was agitated at 30°C for 24 h. The ratio of LMM to total AG was 51.8 wt%. MLM and LMM were purified from 1,968 and
813 g reaction mixtures by stepwise short-path distillation, respectively. Consequently, MLM was purified to 92.3% with 49.1%
recovery, and LMM was purified to 93.2% with 52.3% recovery. Regiospecific analyses of MLM and LMM indicated that the 2-positions
of MLM and LMM were 95.1 mol% LCFA and 98.3 mol% C8 FA, respectively. The results showed that a process comprising lipase reaction and short-path distillation is effective for
large-scale preparation of high-purity regiospecific TAG isomers. 相似文献