全文获取类型
收费全文 | 11932篇 |
免费 | 1568篇 |
国内免费 | 636篇 |
专业分类
电工技术 | 645篇 |
综合类 | 658篇 |
化学工业 | 3551篇 |
金属工艺 | 695篇 |
机械仪表 | 264篇 |
建筑科学 | 510篇 |
矿业工程 | 314篇 |
能源动力 | 527篇 |
轻工业 | 1227篇 |
水利工程 | 211篇 |
石油天然气 | 537篇 |
武器工业 | 49篇 |
无线电 | 922篇 |
一般工业技术 | 2015篇 |
冶金工业 | 1468篇 |
原子能技术 | 174篇 |
自动化技术 | 369篇 |
出版年
2024年 | 31篇 |
2023年 | 463篇 |
2022年 | 323篇 |
2021年 | 612篇 |
2020年 | 546篇 |
2019年 | 477篇 |
2018年 | 417篇 |
2017年 | 527篇 |
2016年 | 529篇 |
2015年 | 445篇 |
2014年 | 683篇 |
2013年 | 757篇 |
2012年 | 793篇 |
2011年 | 826篇 |
2010年 | 544篇 |
2009年 | 575篇 |
2008年 | 478篇 |
2007年 | 613篇 |
2006年 | 643篇 |
2005年 | 542篇 |
2004年 | 471篇 |
2003年 | 423篇 |
2002年 | 339篇 |
2001年 | 313篇 |
2000年 | 256篇 |
1999年 | 221篇 |
1998年 | 199篇 |
1997年 | 160篇 |
1996年 | 138篇 |
1995年 | 130篇 |
1994年 | 105篇 |
1993年 | 93篇 |
1992年 | 98篇 |
1991年 | 73篇 |
1990年 | 46篇 |
1989年 | 36篇 |
1988年 | 37篇 |
1987年 | 15篇 |
1986年 | 26篇 |
1985年 | 25篇 |
1984年 | 30篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1973年 | 3篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
991.
Motomu Nishioka Yoshihiro Ojima Yuki TsushimaMasahiro Matsumoto Masahito Taya 《Journal of Bioscience and Bioengineering》2010,109(4):392-394
In photoautotrophic cultures of pak-bung hairy roots, strong light irradiation (22 W/m2) increased the content of reactive oxygen species (ROS) in the cells, resulting in chlorophyll (Chl) degradation and DNA injury. The Chl degradation rate, RD, can be used as a parameter to measure the cellular damage caused by photo-induced stress. The presence of the antioxidants ascorbic acid, chlorogenic acid or catechin reduced the RD, while lowering the content of ROS and moderating the DNA injury. 相似文献
992.
通过与传统热力除氧器相比较,分析了LHY-Ⅱ型催化除氧设备在节能降耗方面的重要功效,希望该除氧设备能迅速得到普及,从而达到节能及环保的双重目的。 相似文献
993.
Oxygen potentials of oxide nuclear fuels are important thermodynamic data in development of nuclear fuel technologies. Minor actinide bearing MOX (mixed oxide) fuels have been developed as sodium cooled fast reactor fuels. Content of Am which is one of the minor actinide elements causes oxygen potentialto increase. The effects of the oxygen potential increase on the irradiation behavior were evaluated. Profiles of temperature and O/M (oxygen-to-metal) ratio in the pellets were evaluated to better understand the irradiation behavior. From these data, local oxygen potential in the radial direction of the pellets was calculated, and was compared with free energy of compounds composed of fission products. Based on this comparison, it was concluded that Cs2MoO4 was likely formed at pellet periphery of (U07Pu03)O1.98 and (U0.66Pu03Amoo16Npo.016)Ol.976 The extent of cladding tube inner surface oxidation was predicted by using the calculated oxygen potential. No significant difference between irradiation behaviors of (Uo.7Puo3)O2_x and (U0.66PUo 3Amo.016Npo.016)O2.x pellets was confirmed. 相似文献
994.
An electrochemical deoxidation using a ZrO2 based solid electrolyte was investigated to control the interfacial oxygen concentration between the molten steel and ZrO2. The electrochemical deoxidation cell consisted of an MgO stabilized ZrO2 and an external power supply. In a previous study with constant external DC voltage, the oxygen concentration at the interface between the solid electrolyte and the molten steel was decreased to 2.2 ppm, which was the limit caused by the cathodic over‐potential when a constant external DC voltage was applied. In the present study, a novel process of using a periodic or cyclic voltage for the electrochemical deoxidation cell was developed, to surpass this limitation caused by the over‐optential of the electrochemical cell and thus decreasing the oxygen concentration to sub‐ppm levels at the interface between the molten Fe and the solid electrolyte. 相似文献
995.
996.
Antonio De León‐Rodríguez Enrique Galindo Octavio T. Ramírez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2010,85(7):950-956
BACKGROUND: A laboratory scale one‐compartment scale‐down system (1‐CSDS), used to generate dissolved oxygen tension (DOT) gradients was designed and characterized. The system consists of a 1.5‐L stirred‐tank bioreactor coupled to an automatic DOT controller that changes the oxygen partial pressure in the inlet gas through a feedback proportional–integral–derivative algorithm, while maintaining the hydrodynamic conditions constant. Oscillatory control of DOT was achieved by employing time‐dependent square wave or sinusoidal setpoints. RESULTS: The 1‐CSDS can be modeled as a first‐order dynamic system, but showing a permanent lag between the system response and the setpoint. The 1‐CSDS had a faster response rate for generating oscillating DOT when a square wave setpoint was used rather than a sinusoidal setpoint. The 1‐CSDS generated symmetric DOT oscillations at periods above of 100 s. CONCLUSION: The 1‐CSDS is suited to investigate the responses of microorganisms and cells, of biotechnological importance, to oscillatory DOT conditions. It was found that the response of the 1‐CSDS was limited by the kLa. Copyright © 2010 Society of Chemical Industry 相似文献
997.
Lilioara Surdu Ovidiu Iordache Elena Manaila Gabriela Craciun Laurentia Alexandrescu 《纺织学会志》2013,104(11):1426-1433
This paper presents the improvement of the resistance to fungi of some cotton textile materials by treating in the manufacturing process with oxygen plasma and chitosan. Thus, after the weaving and preliminary finishing, the fabrics were cleaned in oxygen plasma atmosphere and after dyeing, have been treated with chitosan solution with concentrations of 1 or 5 g/l, in order to confer them antimicrobial properties. The antimicrobial tests were performed with two fungi: Candida albicans and Tricophyton interdigitale. The obtained antimicrobial effect was considerably higher compared to that of the raw fabrics. The colour resistance of dyed fabrics was not significantly influenced by applying the treatment-based chitosan. 相似文献
998.
Paolo Sarti Maria Chiara Magnifico Fabio Altieri Daniela Mastronicola Marzia Arese 《International journal of molecular sciences》2013,14(6):11259-11276
Extending our previous observations, we have shown on HaCat cells that melatonin, at ~10−9 M concentration, transiently raises not only the expression of the neuronal nitric oxide synthase (nNOS) mRNA, but also the nNOS protein synthesis and the nitric oxide oxidation products, nitrite and nitrate. Interestingly, from the cell bioenergetic point of view, the activated NO-related chemistry induces a mild decrease of the oxidative phosphorylation (OXPHOS) efficiency, paralleled by a depression of the mitochondrial membrane potential. The OXPHOS depression is apparently balanced by glycolysis. The mitochondrial effects described have been detected only at nanomolar concentration of melatonin and within a time window of a few hours’ incubation; both findings compatible with the melatonin circadian cycle. 相似文献
999.
1000.