全文获取类型
收费全文 | 6904篇 |
免费 | 339篇 |
国内免费 | 22篇 |
专业分类
电工技术 | 84篇 |
综合类 | 15篇 |
化学工业 | 1283篇 |
金属工艺 | 245篇 |
机械仪表 | 328篇 |
建筑科学 | 134篇 |
矿业工程 | 10篇 |
能源动力 | 283篇 |
轻工业 | 540篇 |
水利工程 | 24篇 |
石油天然气 | 15篇 |
无线电 | 1409篇 |
一般工业技术 | 1323篇 |
冶金工业 | 640篇 |
原子能技术 | 92篇 |
自动化技术 | 840篇 |
出版年
2023年 | 73篇 |
2022年 | 105篇 |
2021年 | 164篇 |
2020年 | 95篇 |
2019年 | 134篇 |
2018年 | 173篇 |
2017年 | 157篇 |
2016年 | 209篇 |
2015年 | 168篇 |
2014年 | 250篇 |
2013年 | 482篇 |
2012年 | 396篇 |
2011年 | 493篇 |
2010年 | 340篇 |
2009年 | 408篇 |
2008年 | 342篇 |
2007年 | 298篇 |
2006年 | 251篇 |
2005年 | 263篇 |
2004年 | 191篇 |
2003年 | 199篇 |
2002年 | 180篇 |
2001年 | 142篇 |
2000年 | 140篇 |
1999年 | 122篇 |
1998年 | 262篇 |
1997年 | 145篇 |
1996年 | 140篇 |
1995年 | 125篇 |
1994年 | 92篇 |
1993年 | 93篇 |
1992年 | 67篇 |
1991年 | 59篇 |
1990年 | 53篇 |
1989年 | 48篇 |
1988年 | 37篇 |
1987年 | 36篇 |
1986年 | 36篇 |
1985年 | 31篇 |
1984年 | 27篇 |
1983年 | 30篇 |
1982年 | 32篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 13篇 |
1976年 | 22篇 |
1975年 | 11篇 |
1974年 | 10篇 |
排序方式: 共有7265条查询结果,搜索用时 0 毫秒
991.
Crude protease originating from kiwifruit (Actinidia deliciosa) was extracted for organic processed food uses. The protease included in the kiwifruit can be utilized for organic uses instead of current commercial enzymes from microbial origin, which are not suitable for organic processed food. Crude protease extracted by physical treatment rather than any biochemical purification methods was appropriate for the organic processed food uses. However, crude protease extract has been found to be unstable for processing and storage usage, which has to be modified to be stable by appropriate methods suitable for organic processed food uses. The proteolytic activity of the protease extracted from kiwifruit was measured using casein as a substrate. The decreased inactivation rate constant of crude protease treated with guar gum and locust bean gum within the temperature range of 30–50°C implied the enhanced stability of crude enzymes by treatment with hydrocolloid. The half-times of crude proteases treated with guar gum and locust bean gum were higher than the half-time of native crude protease at 40°C (optimum temperature of the native crude protease), with values of 55.45 min for the guar gum-treated sample, 50.23 min for the locust bean gum-treated sample and 23.26 min for the native sample, demonstrating the quantitative evidence of the enzyme stability. The relatively stable maintenance of the proteolytic activity has helped to realize hydrocolloid-treated enzyme to be used for hydrolytic function in organic processed food applications. 相似文献
992.
993.
Fucosterol inhibits adipogenesis through the activation of AMPK and Wnt/β-catenin signaling pathways
Food Science and Biotechnology - Fucosterol is a sterol constituent primarily derived from brown algae. Recently, the antiadipogenic effect of fucosterol has been reported; however, its molecular... 相似文献
994.
Root homogenate from poplar trees (Populus deltoides x nigra DN34, Imperial Carolina) stimulated perchlorate degradation in microcosms of soil and water samples collected at a perchlorate contaminated site, the Longhorn Army Ammunition Plant (LHAAP), located outside Karnack, Texas. Direct use of root products by perchlorate-degrading bacteria was shown for the first time as six pureculture bacteria isolated from LHAAP perchlorate-degrading microcosms degraded perchlorate when given root products as the sole exogenous source of carbon and electron donor. Nonenriched environmental consortia were able to utilize root products for perchlorate degradation, regardless of prior exposure to perchlorate. Microcosms that contained perchlorate-contaminated groundwater (MW-3) or uncontaminated surface water (Harrison Bayou) as inoculum degraded approximately 240 and 160 mg L(-1) perchlorate, respectively, using root products (approximately 440 mg L(-1) as COD) over 38 days. The predominant bacterial species in these aqueous microcosms, identified by DGGE, depended only upon the source inoculum as similar sequences were obtained whether root products or lactate was the electron donor. Sequences from DGGE bands that matched species within Dechloromonas, a genus consisting of many perchlorate degraders, were identified in all perchlorate-degrading microcosms. This study demonstrates the ability of root products to drive perchlorate respiration by bacteria and the potential for successful achievement of perchlorate rhizodegradation using in situ phytoremediation. 相似文献
995.
996.
A diffusive solar cell window was designed and fabricated with uniformly distributed nanocomposite particles in a light diffusive plate that was sandwiched between two glass layers. The entire composite construction transfers light radiation to solar cells at the edge of the windows. It is based on a new combination of existing technologies because of it uses mature, mass-produced components - solar cells - as well as nanocomposite particles that are embedded inside the light-guide plate. They are integrated using an inexpensive and widely used method for making building windows. The result is an inexpensive, strong, stable, view quality-preserving solar energy-harvesting window that has no close competition. The diffusive solar cell window does not suffer from aging, and products that are made using diffusive solar cell window technology will be new entries to the solar power generation window market. 相似文献
997.
998.
Using first principles calculations, we study fundamental mechanism of spontaneous reduction reaction of Eu3+ to Eu2+ in eutectic LiCl‐KCl molten salt. We decouple the reaction Gibbs free energy into enthalpy and entropy contributions by using rigorous thermodynamic formalism. Key structural features of the solvation shell are characterized by the radial distribution function and the coordination number. Compared with Eu2+, the Eu3+ ion has a more rigid framework of the solvation shells, corroborating its stronger electrostatic interaction with neighboring ligands of Cl? ions and a more favorable state on the aspect of enthalpy. Computations on vibrational frequency, however, pose significant contribution of vibrational entropy to the reaction Gibbs free energy for the reduction. Vibration frequency of Eu2+ is smaller than that of Eu3+, driving a more positive change of the entropy in the reduction reaction. Furthermore, an Eu2+ diffuses more quickly than an Eu3+ in the LiCl‐KCl molten salt with switching mechanism of ligand Cl? ions in the solvation shell. Our results propose that the spontaneity of the reduction reaction is driven by the entropic contribution by overcoming the penalty of the reaction enthalpy. 相似文献
999.
Influence of marine oligosaccharides on the response of various biological systems to UV irradiation 总被引:1,自引:0,他引:1
Xiaojia He Rong Li Guiming Huang Huey-min Hwang Xiaolu Jiang 《Journal of Functional Foods》2013,5(2):858-868
Low molecular weight alginate-derived oligosaccharide (ADO) (373–571 Da) and chito-oligosaccharide (COS) (855–1671 Da) were purified from alginate and chitosan, and known as marine oligosaccharides with polyanionic and polycationic properties, respectively. We compared the effects of ADO and COS on cell regulation using several biological models (Candida albicans, Escherichia coli and Bacillus subtilis spore), cellular uptake determination, erythrocytes haemolysis inhibition and antioxidant capacity assay to investigate stress response under UV radiation. Our results further confirmed the anti-UVR potential of ADO and COS and their potential for commercial UVR protector application in the area of functional foods as food ingredients. 相似文献
1000.
Survival and growth of Bacillus cereus group and presumptive Cronobacter in the rehydrated sunsik were investigated to control the pathogens. Five sunsik contaminated naturally by the pathogens were rehydrated with hot
waters of 50, 60, 65, and 70°C and kept for 24 hr at 5 and 25°C. Survival and growth of B. cereus seemed to be influenced not by rehydration water temperature, but by storage temperature and time after rehydration. However,
survival and growth of Cronobacter was influenced by both rehydration temperature and storage conditions. Especially, storage temperature and time seemed to
be more important than the rehydration temperature to limit the growth of Cronobacter. Therefore, it is required to take immediately the sunsik after rehydration with at least 65°C water, otherwise within 6
hr at room temperature for the risk reduction of B. cereus and Cronobacter. 相似文献