全文获取类型
收费全文 | 1076篇 |
免费 | 81篇 |
国内免费 | 68篇 |
专业分类
电工技术 | 27篇 |
综合类 | 113篇 |
化学工业 | 124篇 |
金属工艺 | 27篇 |
机械仪表 | 23篇 |
建筑科学 | 175篇 |
矿业工程 | 24篇 |
能源动力 | 163篇 |
轻工业 | 67篇 |
水利工程 | 59篇 |
石油天然气 | 40篇 |
武器工业 | 1篇 |
无线电 | 21篇 |
一般工业技术 | 146篇 |
冶金工业 | 59篇 |
原子能技术 | 17篇 |
自动化技术 | 139篇 |
出版年
2023年 | 12篇 |
2022年 | 35篇 |
2021年 | 40篇 |
2020年 | 37篇 |
2019年 | 41篇 |
2018年 | 32篇 |
2017年 | 45篇 |
2016年 | 41篇 |
2015年 | 40篇 |
2014年 | 61篇 |
2013年 | 55篇 |
2012年 | 70篇 |
2011年 | 81篇 |
2010年 | 76篇 |
2009年 | 75篇 |
2008年 | 68篇 |
2007年 | 61篇 |
2006年 | 53篇 |
2005年 | 34篇 |
2004年 | 30篇 |
2003年 | 28篇 |
2002年 | 34篇 |
2001年 | 25篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 19篇 |
1997年 | 7篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1225条查询结果,搜索用时 15 毫秒
1.
Yinjuan Cao Shunzhong He Qunli Yu Ling Han Wei Zhang Xiaohong Zou 《International Journal of Food Science & Technology》2022,57(5):3001-3011
This study investigated the effect of 5 freeze–thaw cycles (freezing at −18°C for 12 h and then thawing at 4°C for approximately 12 h) on the meat quality, proximate composition, water distribution and microstructure of bovine rumen smooth muscle (BSM). As the number of freeze–thaw cycles increased, BSM pH, shear force, water content and protein content decreased by 3.06%, 35.50%, 14.49% and 21.11%, respectively, whereas BSM thawing loss, cooking loss, pressing loss, total aerobic count (TAC), ash content and fat content increased by 108.12%, 47.75%, 78.33%, 90.99%, 105% and 35.20%, respectively. The freeze–thaw cycles resulted in greater protein and lipid oxidation, as evidenced by a 36.46% reduction in the sulfhydryl content and a 209.06% and 338.46% increase in the carbonyl and malondialdehyde contents, respectively. Ice crystal formation disrupted the structural integrity of the muscle tissue. Low-field nuclear magnetic resonance results showed that the freeze–thaw cycles prolonged the relaxation times (T2b, T21 and T22), indicating that immobile water shifted to free water, and consequently, free water mobility increased. After 3 freeze–thaw cycles, the decline in shear force slowed, the increase in thawing loss became accelerated, and the TAC approached the domain value (6 log colony-forming units/g). Therefore, the number of freeze–thaw cycles of smooth muscle during transport, storage and distribution should be controlled to 3 or fewer. The current results provide a theoretical basis and data support for the further utilisation and culinary processing of smooth muscle. 相似文献
2.
Nonchanok Ngoenthong Vut Tongnan Thana Sornchamni Nuchanart Siri-nguan N. Laosiripojana Unalome Wetwatana Hartley 《International Journal of Hydrogen Energy》2021,46(48):24581-24590
A stainless steel micro-channel reactor was tailor-made to an in house-design for process intensification propose. The reactor was used for a two-step thermochemical cycles of H2O and CO2 co-splitting reaction, in the presence of La0.3Sr0.7Co0.7Fe0.3O3 (LSCF). LSCF was coated inside the reactor using wash-coat technique. Oxygen storage capacity of LSCF was determined at 4465 μmol/g, using H2-TPR technique. H2O-TPSR and CO2-TPSR results suggested that a formation of surface hydroxyl group was the cause of H2O splitting favorable behavior of LSCF. Optimal operating reduction/oxidation temperature was found at 700 °C, giving 2266 μmol/g of H2, 705 μmol/g of CO, and 67% of solid conversion, when the H2O and CO2 ratio was 1 to 1, and WSHV was 186,000 mL/g.h. Activation energy of H2O spitting and CO2 splitting was estimated at 87.33 kJ/mol, and 102.85 kJ/mol The pre-exponential factor of H2O splitting and CO2 splitting was 595.24 s?1 and 698.79 s?1, respectively. 相似文献
3.
Minjie Cao Jing Wang Ailing Cao David Shiuan Rongfa Guan Luyun Cai Yanbo Wang 《International Journal of Food Science & Technology》2019,54(5):1642-1650
Recrystallisation often occurs in the freeze-thaw cycles and results in poor food quality. This study was undertaken to analyse the effects of recrystallisation on the changes of protein conformation and moisture migration within red seabream fillets after the freeze-thaw cycles. The UV second-derivative spectroscopy, intrinsic fluorescence measurement and Raman spectroscopy were employed to evaluate the protein conformational changes. The Low-field NMR spectra analysis was used to evaluate moisture migration. The results indicated that the freeze-thaw cycles altered the secondary and tertiary structure of proteins. It was noticed that interactions between water and protein molecules were decreased gradually and eventually induced the thermal instability of the myosin molecules. The immobilised water content declined and the free water content increased. There were significant destructions in fillet muscle microstructure. These observations unambiguously reflect how the recrystallisations affect the protein conformation and moisture migration patterns of red seabream fillets during freeze-thaw cycles. 相似文献
4.
Calcite has a highly anisotropic thermal expansion coefficient, and repeated heating and cooling cycles can potentially destabilize chalks by breaking cement bonds between neighboring particles. Based on tensile strength measurements, we investigated how temperature cycles induce weakening of chalk. Tensile strength tests were performed on chalk specimens sampled from Kansas (USA) and Mons (Belgium), each with differing amounts of contact cement. Samples of the two chalk types were tested in dry and water-saturated states, and then exposed to 0, 15, and 30 temperature cycles in order to find out under what circumstances thermally induced tensile strength reduction occurs. The testing results show that the dry samples were not influenced by temperature cycling in either of the chalk types. However, in the water-saturated state, tensile strength is increasingly reduced with progressive numbers of temperature cycles for both chalk samples, especially for the more cemented Kansas chalk. The Kansas chalk demonstrated higher initial tensile strength compared to the less cemented Mons chalk, but the strength of both chalks was reduced by the same relative proportion when undergoing thermal cycles in the water-saturated state. 相似文献
5.
Ionela-Dorina Dumbrava Calin-Cristian Cormos 《International Journal of Hydrogen Energy》2021,46(45):23149-23163
Hydrogen production by biogas conversion represent a promising solution for reduction of fossil CO2 emissions. In this work, a detailed techno-economic analysis was performed for decarbonized hydrogen production based on biogas conversion using calcium and chemical looping cycles. All evaluated concepts generate 100,000 Nm3/h high purity hydrogen. As reference cases, the biogas steam reforming design without decarbonization and with CO2 capture by gas-liquid chemical absorption were also considered. The results show that iron-based chemical looping design has higher energy efficiency compared with the gas-liquid absorption case by 2.3 net percentage points as well as a superior carbon capture rate (99% vs. 65%). The calcium looping case shows a lower efficiency than chemical scrubbing, with about 2.5 net percentage points, but the carbon capture rate is higher (95% vs. 65%). The hydrogen production cost increases with decarbonization, the calcium looping shows the most favourable situation (37.14 €/MWh) compared to the non-capture steam reforming case (33 €/MWh) and MDEA and iron looping cases (about 42 €/MWh). The calcium looping case has the lowest CO2 avoidance cost (10 €/t) followed by iron looping (20 €/t) and MDEA (31 €/t) cases. 相似文献
6.
Tatiya Khamhangdatepon Vut Tongnan Matthew Hartley Thana Sornchamni Nuchanart Siri-Nguan Navadol Laosiripojana Kang Li Unalome Wetwatana Hartley 《International Journal of Hydrogen Energy》2021,46(48):24666-24675
La0·3Sr0·7Co0·7Fe0·3O3 (LSCF3773) was chosen as an oxygen carrier material for synthesis gas production and synthesized using ethylene-diamine-tetra-acetic acid (EDTA) citrate-complexing method. LSCF exhibited a pure cubic structure where 110 and 100 plane diffractions were active for CO2 splitting, while 111 was more favored by H2O splitting. Overall oxygen storage capacity (OSC) of LSCF was 4072 μmol/gcat. During the reduction process, regular cations (Co4+, Fe4+), polaron cations (Co3+, Fe3+) and localized cations (Co2+, Fe2+) were achieved when the LSCF was reduced at 500, 700 and 900 °C, respectively. The strength of the active sites depended on reduction temperatures. An increase in oxidation temperature enhanced H2 production at temperature ranging from 500 °C to 700 °C while effected CO production at 900 °C. H2O and CO2 was competitively split during the oxidation step, especially at 700 °C. The activation energy of each reaction was ordered as; CO2 splitting > H2O splitting > CO2 adsorption, supporting the above evidence where H2 and CO production were found to increase when the operating temperature was increased. 相似文献
7.
This paper examines two needle-punched geosynthetic clay liners' water retention behaviour at high suction ranges using the vapour equilibrium technique where super-saturated salt solutions controlled the relative humidity. This study shows that the bentonite form and its mineralogy affect the absorption/desorption of GCLs and their corresponding water retention curves. In particular, a granular bentonite-based GCL was found to absorb more and release less water than a powdered bentonite-based GCL due to its higher montmorillonite content and larger pores. The water retention curves of both GCLs exhibited very little hysteretic behaviour at high suction. Repeated wetting-drying cycles shifted the WRCs of both GCLs slightly downward with minimal impact on their degree of hysteresis. 相似文献
8.
9.
《International Journal of Hydrogen Energy》2019,44(56):29743-29751
Operational rules and control strategies of the chemically recuperated gas turbine (CRGT) in the marine propulsion are investigated in this paper. The Minimization of Gibbs free energy method is used to calculate the diesel-steam reforming reaction which products synthetic hydrogen rich fuels, and a universal model of the chemical regenerator which is easily applied to different application environments is created. The hydrogen production and hydrogen molar fraction are investigated to verify that the CRGT improve the combustion performances under low working conditions. Off-design calculations are performed to derive proper operational rules, and transient calculations are performed to investigate the best control strategies for the systems. The modelling approach of the chemical regenerator can be generally used in the chemically recuperated gas turbine. The elaborate operational rules can greatly improve the thermal efficiencies under every working condition. The system using synchronous control strategies have better regulation speed and operation stability than that using asynchronous control strategies. 相似文献
10.
Zefu Wang Zhifei He Dong Zhang Xiaosi Chen Hongjun Li 《International Journal of Food Science & Technology》2021,56(6):3004-3015
Frozen storage is chosen to be the preferred method in meat preservation. However, multiple freeze-thaw (F-T) cycles will occur during the transfers or distribution processes under poor cold-chain conditions. This study investigated the effects of multiple freeze-thaw (F-T) cycles on water mobility, microstructure damage, protein oxidation and lipid oxidation in rabbit meat during seven F-T cycles through 56 days. Scanning electron microscopy results indicated that the increase of F-T cycles induced the rupture of endomysia and the increase of gaps between fibres. Low-field nuclear magnetic resonance (LF-NMR) results showed that the peak area of T21 and T22 decreased with increasing number of repeated F-T cycles, indicating that immobile water shifted to free water, and free water mobility increased. During repeated freeze-thaw process, the peroxide value, thiobarbituric acid-reactive substances, non-haem iron content and carbonyl groups of rabbit meat gradually increased, whereas haem content, haem iron content and sulfhydryl content of rabbit meat gradually decreased. In addition, the results of Fourier transform infrared, sodium dodecyl sulphate polyacrylamide gel electrophoresis, and intrinsic fluorescence spectroscopy indirectly proved that multiple F-T cycles could cause α-helix structure disruption, protein aggregation and degradation, and tryptophan oxidation of rabbit meat myofibrillar protein (MP). Overall, multiple repeated F-T cycles changed moisture migration, damaged microstructure and promoted lipid and protein oxidation of rabbit meat. 相似文献