首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1541299篇
  免费   29334篇
  国内免费   7195篇
电工技术   34740篇
综合类   6496篇
化学工业   277564篇
金属工艺   65595篇
机械仪表   44239篇
建筑科学   46625篇
矿业工程   11412篇
能源动力   51822篇
轻工业   113183篇
水利工程   15315篇
石油天然气   37547篇
武器工业   147篇
无线电   201985篇
一般工业技术   290348篇
冶金工业   173583篇
原子能技术   34280篇
自动化技术   172947篇
  2021年   16807篇
  2020年   12653篇
  2019年   15424篇
  2018年   16617篇
  2017年   15897篇
  2016年   22484篇
  2015年   18306篇
  2014年   30240篇
  2013年   90403篇
  2012年   37540篇
  2011年   50379篇
  2010年   44445篇
  2009年   52785篇
  2008年   46277篇
  2007年   42761篇
  2006年   45644篇
  2005年   39905篇
  2004年   42099篇
  2003年   41938篇
  2002年   41001篇
  2001年   38053篇
  2000年   36388篇
  1999年   35796篇
  1998年   48900篇
  1997年   41272篇
  1996年   37039篇
  1995年   31767篇
  1994年   29678篇
  1993年   29443篇
  1992年   26293篇
  1991年   23520篇
  1990年   23793篇
  1989年   22853篇
  1988年   21303篇
  1987年   19541篇
  1986年   18933篇
  1985年   22125篇
  1984年   22300篇
  1983年   20269篇
  1982年   19322篇
  1981年   19425篇
  1980年   18005篇
  1979年   18484篇
  1978年   17723篇
  1977年   17544篇
  1976年   18746篇
  1975年   15976篇
  1974年   15463篇
  1973年   15544篇
  1972年   12997篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
Gelatin is one of the most important multifunctional biopolymers and is widely used as an essential ingredient in food, pharmaceutical, and cosmetics. Porcine gelatin is regarded as the leading source of gelatin globally then followed by bovine gelatin. Porcine sources are favored over other sources since they are less expensive. However, porcine gelatin is religiously prohibited to be consumed by Muslims and the Jewish community. It is predicted that the global demand for gelatin will increase significantly in the future. Therefore, a sustainable source of gelatin with efficient production and free of disease transmission must be developed. The highest quality of Bovidae-based gelatin (BG) was acquired through alkaline pretreatment, which displayed excellent physicochemical and rheological properties. The utilization of mammalian- and plant-based enzyme significantly increased the gelatin yield. The emulsifying and foaming properties of BG also showed good stability when incorporated into food and pharmaceutical products. Manipulation of extraction conditions has enabled the development of custom-made gelatin with desired properties. This review highlighted the various modifications of extraction and processing methods to improve the physicochemical and functional properties of Bovidae-based gelatin. An in-depth analysis of the crucial stage of collagen breakdown is also discussed, which involved acid, alkaline, and enzyme pretreatment, respectively. In addition, the unique characteristics and primary qualities of BG including protein content, amphoteric property, gel strength, emulsifying and viscosity properties, and foaming ability were presented. Finally, the applications and prospects of BG as the preferred gelatin source globally were outlined.  相似文献   
14.
15.
16.
17.
18.
Garzan oil field is located at the south east of Turkey. It is a mature oil field and the reservoir is fractured carbonate reservoir. After producing about 1% original oil in place (OOIP) reservoir pressure started to decline. Waterflooding was started in order to support reservoir pressure and also to enhance oil production in 1960. Waterflooding improved the oil recovery but after years of flooding water breakthrough at the production wells was observed. This increased the water/oil ratio at the production wells. In order to enhance oil recovery again different techniques were investigated. Chemical enhanced oil recovery (EOR) methods are gaining attention all over the world for oil recovery. Surfactant injection is an effective way for interfacial tension (IFT) reduction and wettability reversal. In this study, 31 different types of chemicals were studied to specify the effects on oil production. This paper presents solubility of surfactants in brine, IFT and contact angle measurements, imbibition tests, and lastly core flooding experiments. Most of the chemicals were incompatible with Garzan formation water, which has high divalent ion concentration. In this case, the usage of 2-propanol as co-surfactant yielded successful results for stability of the selected chemical solutions. The results of the wettability test indicated that both tested cationic and anionic surfactants altered the wettability of the carbonate rock from oil-wet to intermediate-wet. The maximum oil recovery by imbibition test was reached when core was exposed 1-ethly ionic liquid after imbibition in formation water. Also, after core flooding test, it is concluded that considerable amount of oil can be recovered from Garzan reservoir by waterflooding alone if adverse effects of natural fractures could be eliminated.  相似文献   
19.
Journal of Computer and Systems Sciences International - It is shown that the Lyapunov theorem on the distribution properties of the sum of random variables with different distribution densities...  相似文献   
20.
Multimedia Tools and Applications - Mammograms are the images used by radiologists to diagnose breast cancer. Breast cancer is one of the most common cancers in women. The early detection of breast...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号