全文获取类型
收费全文 | 3619篇 |
免费 | 105篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 45篇 |
综合类 | 1篇 |
化学工业 | 777篇 |
金属工艺 | 133篇 |
机械仪表 | 57篇 |
建筑科学 | 149篇 |
矿业工程 | 27篇 |
能源动力 | 64篇 |
轻工业 | 329篇 |
水利工程 | 27篇 |
石油天然气 | 14篇 |
无线电 | 211篇 |
一般工业技术 | 607篇 |
冶金工业 | 792篇 |
原子能技术 | 64篇 |
自动化技术 | 429篇 |
出版年
2021年 | 36篇 |
2020年 | 30篇 |
2019年 | 37篇 |
2018年 | 40篇 |
2017年 | 43篇 |
2016年 | 48篇 |
2015年 | 55篇 |
2014年 | 82篇 |
2013年 | 226篇 |
2012年 | 122篇 |
2011年 | 155篇 |
2010年 | 135篇 |
2009年 | 112篇 |
2008年 | 137篇 |
2007年 | 127篇 |
2006年 | 132篇 |
2005年 | 106篇 |
2004年 | 125篇 |
2003年 | 117篇 |
2002年 | 87篇 |
2001年 | 61篇 |
2000年 | 68篇 |
1999年 | 70篇 |
1998年 | 140篇 |
1997年 | 96篇 |
1996年 | 78篇 |
1995年 | 50篇 |
1994年 | 68篇 |
1993年 | 69篇 |
1992年 | 49篇 |
1991年 | 44篇 |
1990年 | 44篇 |
1989年 | 39篇 |
1988年 | 42篇 |
1987年 | 39篇 |
1986年 | 44篇 |
1985年 | 59篇 |
1984年 | 49篇 |
1983年 | 31篇 |
1982年 | 33篇 |
1981年 | 46篇 |
1980年 | 23篇 |
1979年 | 32篇 |
1978年 | 33篇 |
1977年 | 47篇 |
1976年 | 43篇 |
1975年 | 26篇 |
1974年 | 40篇 |
1973年 | 27篇 |
1972年 | 26篇 |
排序方式: 共有3726条查询结果,搜索用时 15 毫秒
111.
This Special Issue “Biodegradable Materials” features research and review papers concerning recent advances on the development, synthesis, testing and characterisation of biomaterials. These biomaterials, derived from natural and renewable sources, offer a potential alternative to existing non-biodegradable materials with application to the food and biomedical industries amongst many others. In this Special Issue, the work is expanded to include the combined use of fillers that can enhance the properties of biomaterials prepared as films. The future application of these biomaterials could have an impact not only at the economic level, but also for the improvement of the environment. 相似文献
112.
Benjamin D. Fallen Katy Rainey Carl E. Sams Dean A. Kopsell Vincent R. Pantalone 《Journal of the American Oil Chemists' Society》2012,89(7):1333-1343
Increasing oleic acid, a monounsaturated fatty acid, is reported to strike the best balance between cold flow properties and oxidative stability in soybean seed oil to enhance biodiesel and produce a better burning fuel. In addition, it is important that elevated oleic acid soybeans have the agronomic traits of local cultivars and maintain oleic acid stability across environments. Research was conducted in 2007–2008 to evaluate six Roundup Ready® soybean recombinant inbred lines exhibiting enhanced levels of oleic acid. The six elevated oleic lines averaged a 55% increase in oleic acid and a 43% decrease in linolenic acid over the two commercial cultivars (AG3906 and AG4103). Some elevated oleic acid genotypes fulfilled the linear regression definition of a stable genotype. TN03-93RR was the best genotype because of its oleic acid content (397 g kg?1) and desirable regression estimates for stability. Iodine value (IV), peroxide value (PV), and induction period (IP) were used to evaluate the fuel properties of the two lines with the highest oleic acid content and the two commercial cultivars. The elevated oleic acid lines had significantly better IP, PV and IV for better biodiesel properties and oxidative stability than the two commercial cultivars. 相似文献
113.
Libin Zhu Carl Olsen Tara McHugh Mendel Friedman Divya Jaroni Sadhana Ravishankar 《Journal of food science》2014,79(1):M61-M66
The objective of this study was to investigate the antimicrobial effects of carvacrol and cinnamaldehyde incorporated into apple, carrot, and hibiscus‐based edible films against Salmonella Newport in bagged organic leafy greens. The leafy greens tested included organic Romaine and Iceberg lettuce, and mature and baby spinach. Each leafy green sample was washed, dip inoculated with S. Newport (107 CFU/mL), and dried. Each sample was put into a Ziploc® bag. Edible films pieces were put into the Ziploc bag and mixed well. The bags were sealed and stored at 4 °C. Samples were taken at days 0, 3, and 7 for enumeration of survivors. On all leafy greens, 3% carvacrol films showed the best bactericidal effects against Salmonella. All 3 types of 3% carvacrol films reduced the Salmonella population by 5 log10 CFU/g at day 0 and 1.5% carvacrol films reduced Salmonella by 1 to 4 log10 CFU/g at day 7. The films with 3% cinnamaldehyde showed 0.5 to 3 log reductions on different leafy greens at day 7. The films with 0.5% and 1.5% cinnamaldehyde and 0.5% carvacrol also showed varied reductions on different types of leafy greens. Edible films were the most effective against Salmonella on Iceberg lettuce. This study demonstrates the potential of edible films incorporated with carvacrol and cinnamaldehyde to inactivate S. Newport on organic leafy greens. 相似文献
114.
<正>即使在北欧人力费用极高的情况下,卡尔·汉森·桑仍以近乎苛刻的标准进行手工制作,并将这份永恒的经典和淡然的精致传递给全世界的使用者。丹麦设计界流传着这样一则故事:1807年,英国轰炸丹麦首都哥本哈根。时任丹麦国王下令从斯德哥尔摩南部到汉堡北部,用一切办法遍植橡树以躲避战争的创伤,并规定:"每棵树都不可被砍掉,除非新种一棵。"结果,战争的炮火并未殃及丹麦,这些橡树幸运存活了下来,年复一年,长成茂密森林。闻着木香,我们来到哥本哈根繁华都市的心脏处——自1780年起就开始引领丹麦设计与工艺时尚的Bredgade大街,百年品牌卡尔·汉森·桑(Carl Hansen&Son)全球旗舰店就坐落于此。 相似文献
115.
IN 2008, a nuclear event occurred at Kr?ko nuclear power plant in Slovenia. Even though it was classified as level 0 on International Nuclear Event Scale, the transparency policy of the Slovenian nuclear safety authorities prompted it to notify the international community. This was the first time that the European Community Urgent Radiological Information Exchange (ECURIE) notification system was used outside the exercise framework. The event was reported in all major European. In this contribution, we report on a content analysis of media articles related to this event. The main research question was if a nuclear emergency generates significant media coverage, even in the case of a minor event and a transparent communication policy. The analysis included more than 200 articles from printed and spoken media in Slovenia and other countries. The analysis revealed a high‐intensity media coverage, emotional reactions and heated political discussion. The main media sources in countries with open political discussions on nuclear energy end up being the politicians, rather than resident experts. 相似文献
116.
ABSTRACT Northwest Arkansas planning policies, like a number of communities across the country, have identified goals working toward more sustainable, livable, and subsequently denser development patterns. However, the understanding of residents’ perceptions of such living arrangements is limited. This study provides a more nuanced understanding of Northwest Arkansas residents’ spatial preferences through a survey of residents’ preferences for private amenities and their trade-off with various spatial densities and patterns in support of sustainability. Results of the survey indicate a preference for, and experience with, single-family residential living arrangements and amenities, with the preponderance (80%) of survey respondents currently living in single-family housing. There is a preference for low-density neighborhoods even if it means sacrificing other amenities. This study is in alignment with previous research suggesting that people may learn to prefer where they live. Additionally, while the majority of survey respondents indicated a preference for communal greenspaces, renters are more likely to prefer communal greenspaces when compared to homeowners. This study indicates that attached, multi-family development and renter development in Northwest Arkansas should consider the provision of communal green spaces, walkable access to transit, and walkable access to services as desired amenities for those residents. 相似文献
117.
Akhil Rao Jennifer S. Curtis Bruno C. Hancock Carl Wassgren 《American Institute of Chemical Engineers》2012,58(5):1381-1396
A numerical study of a dilute turbulent gas‐particle flow with inelastic collisions and turbulence modulation in an Eulerian framework is described. A new interpretation is provided for the interaction/coupling terms, based on a fluctuating energy transfer mechanism. This interpretation provides for a new robust closure model for the interaction terms with the ability to predict the turbulence dampening as well as the turbulence enhancement phenomenon. Further, the model developed herein is investigated along with a variety of other published closure models used for the interaction/coupling terms, particle drag, and solid stress. The models are evaluated against several sets of benchmark experiments for fully‐developed, turbulent gas‐solid flow in a vertical pipe. © 2011 American Institute of Chemical Engineers AIChE J, 2012 相似文献
118.
Juan P. Escobedo Ellen K. Cerreta Daniel T. Martinez Carl P. Trujillo Ricardo A. Lebensohn George T. Gray III 《Metallurgical and Materials Transactions A》2014,45(13):5877-5882
The influence of temperature on the dynamic tensile behavior of Zr has been investigated. Bullet-shaped Zr samples with two different textures were dynamically extruded at room temperature and 523 K (250 °C). A higher ductility was measured for samples deformed at elevated temperature as compared to those extruded at room temperature. This difference in ductility is discussed in terms of zirconium’s ability to accommodate plastic deformation via thermally enhanced slip activity, as evidenced by examination of the deformed microstructures. 相似文献
119.
Edward Vine Michael Sullivan Loren Lutzenhiser Carl Blumstein Bill Miller 《Energy Efficiency》2014,7(4):627-640
The use of experiments— particularly randomized controlled trials (RCTs) where subjects are randomly assigned to treatment and control conditions—has rarely been applied to the process of improving the design of energy efficiency programs and, more fundamentally, to determining the net savings from energy efficiency programs. This paper discusses the use of experimentation in the energy efficiency program field with the hope of explaining how these experiments can be used, and identifying the barriers to their use will cause more experimentation to occur. First, a brief overview of experimental methods is presented. This discussion describes the advantages and disadvantages of conducting experiments in the context of the development and evaluation of energy efficiency programs. It then discusses barriers to the use of experimental methods (including cost and equity issues) and suggests some ways of overcoming these barriers. Finally, recommendations are made for implementing key social experiments, discussing the types of energy efficiency programs and issues that can make use of experimentation and variables that one might use for selecting treatments. 相似文献
120.
J. B. Ferguson Benjamin F. Schultz Pradeep K. Rohatgi Chang-Soo Kim 《Metals and Materials International》2014,20(4):747-755
Understanding the settling behavior of nanoparticles in molten metals/alloys is important as it will aid in achieving uniform dispersions of reinforcement particles in metal matrix nanocomposites. Uniform dispersions are necessary to activate the Orowan strengthening mechanism, which can increase yield strength without significant diminishment of ductility. In this work, an analytical model of particle size effects on settling is described that takes into account both deterministic Stokes’ law and stochastic Brownian motion. The model shows a clear transitional behavior where settling velocity follows Stokes’ law for large particles and then drops to zero for small particles implying that Brownian motion predominates. It indicated that, in the Brownian motion regime, where the discrete nature of the liquid must be considered, the random motion imparted by unbalanced collisions can overwhelm the motions normally imposed by forces such as gravity, viscous drag, and thermal/concentration gradients. 相似文献