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   1566584篇
  免费   33293篇
  国内免费   9623篇
电工技术   37775篇
技术理论   9篇
综合类   10962篇
化学工业   268128篇
金属工艺   67446篇
机械仪表   46893篇
建筑科学   50804篇
矿业工程   13300篇
能源动力   51902篇
轻工业   118808篇
水利工程   16735篇
石油天然气   40381篇
武器工业   619篇
无线电   203758篇
一般工业技术   293279篇
冶金工业   174424篇
原子能技术   34546篇
自动化技术   179731篇
  2021年   17303篇
  2020年   13955篇
  2019年   16395篇
  2018年   16850篇
  2017年   16345篇
  2016年   23147篇
  2015年   20097篇
  2014年   32475篇
  2013年   92317篇
  2012年   41063篇
  2011年   53487篇
  2010年   46736篇
  2009年   54622篇
  2008年   49380篇
  2007年   46570篇
  2006年   49864篇
  2005年   43648篇
  2004年   44795篇
  2003年   44059篇
  2002年   40967篇
  2001年   37725篇
  2000年   35575篇
  1999年   35310篇
  1998年   46404篇
  1997年   40022篇
  1996年   35326篇
  1995年   32262篇
  1994年   30073篇
  1993年   29293篇
  1992年   26529篇
  1991年   23630篇
  1990年   23821篇
  1989年   22716篇
  1988年   21218篇
  1987年   19419篇
  1986年   18954篇
  1985年   22280篇
  1984年   22398篇
  1983年   20246篇
  1982年   19160篇
  1981年   19189篇
  1980年   17836篇
  1979年   18477篇
  1978年   17681篇
  1977年   17749篇
  1976年   19288篇
  1975年   15886篇
  1974年   15447篇
  1973年   15523篇
  1972年   13087篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
61.
Majumder  Bhaswar  Venkatesh  T. G. 《Wireless Networks》2022,28(7):2967-2982
Wireless Networks - Mobile data offloading is a current-day networking paradigm to channelize certain fraction of the cellular data traffic over unlicensed spectrum of WiFi. In this paper, we...  相似文献   
62.
Maidebura  Y. E.  Malin  T. V.  Zhuravlev  K. S. 《Semiconductors》2022,56(6):340-345
Semiconductors - The transformation of a two-dimensional GaN layer into three-dimensional islands (2D–3D transition) under increasing temperature in a flow of ammonia is investigated...  相似文献   
63.
Journal of Communications Technology and Electronics - A modified resonator method for determining the complex permittivity of materials based on the theory of small perturbations where a resonator...  相似文献   
64.
Journal of Communications Technology and Electronics - In this paper, we develop suboptimal algorithms for receiving and processing binary offset carrier (BOC) signals for use in global navigation...  相似文献   
65.
Wireless Personal Communications - Since the last decade, cloud-based Electronic Health Records (EHRs) have achieved important consideration to facilitate remote access of patient medical records....  相似文献   
66.
Journal of Computer and Systems Sciences International - The replacement of complex technical system elements is optimized using a genetic algorithm. Its various operators are analyzed and modified...  相似文献   
67.
利用水力空化过程产生局部的高温、高压、高射流以及强大的剪切力等极端化学物理条件改质处理沙特重质原油,试验结果表明:沙特重质原油经过水力空化改质后粘度由13.61降低至7.22mm2/s,残碳由7.16%降低至6.48%,实沸点蒸馏后减压渣油降低1个百分点。进一步采用APPI FT-IR MS、XRD、FT-IR、SEM和粒度分布等技术研究了水力空化改质对沙重原油分子组成,沥青质团聚体微晶结构、沥青质胶束粒径分布、沥青质官能团、沥青质形貌等方面的影响,从分子角度阐述空化改质重油的机理。研究结果表明:水力空化改质后沙重原油分子量分布、芳烃类化合物缔合作用变小;沥青质对低DBE化合物吸附性能降低;沥青质团聚体微晶结构更加松散;沥青质胶束粒度分布降低;沥青质分子相互团聚作用力减弱。进一步考察了水力空化改质前后减压渣油延迟焦化性能,改质处理后焦炭产率降低1.85个百分点,液体收率和气体产率分别增加1.52和0.33个百分点,水力空化改质对沥青质性质、结构特点的改善能够有效的提高其加工性能。  相似文献   
68.
The structural diversity of polyphenols and the inherent limitations of current extraction techniques pose a challenge to extract polyphenols using a simple and green method. Hence, in this study, a method was developed to simultaneously fractionate multiple classes of polyphenols by only varying ethanol-water solutions. Honeybush tea, which is rich in polyphenols, was selected as a model for this study. Solvent extraction followed by solid-phase extraction (SPE) was developed to obtain a polyphenol-rich fraction from six honeybush samples. Based on a gradient elution programme (10%, 30%, 50%, 70% and 90% (v/v) ethanol-water solution) of SPE, the Strata X cartridge showed a better recovery of most targeted polyphenols under 0.9 mL of the drying volume and 1 mL min−1 of the dispensing speed. The elution programme for fractionating most polyphenols was as follows: single elution with 50% ethanol, followed by twice elution with 70% ethanol. The antioxidant capacity was used to analyse the differences among the polyphenol-rich fractions from six honeybush samples. Principal component analysis (PCA) revealed that unfermented C. genistoides (GG) has the greatest antioxidant capacity among the honeybush species studied. Additionally, mangiferin, isomangiferin and vicenin-2 were the main contributors to the antioxidant capacity in six honeybush fractions according to the correlation study.  相似文献   
69.
The effects of cellulose microfibres (CMFs, Average size: 100 ± 5 μm) and cellulose nanofibres (CNFs, Average size: 60 ± 3 nm) on the properties of myofibrillar protein (MP) gels from duck breast meat were studied. The results demonstrated that CMFs and CNFs were mostly connected to MP by non-covalent bonds, the diffusion and cross-linking of MP molecules was promoted, and a denser and more complete gel network was formed. With the increases of CMFs and CNFs concentration (0–10%), the hardness was increased by 13.15% and 19.78% for CMFs10% and CNFs10% gels, respectively, and the elasticity was increased by 40% and 80%, respectively. At the same concentration (0–10%), the increase in gel hardness, viscoelasticity and immobilised water content was greater in the CNFs-MP group than in the CMFs-MP group. The CNFs-MP group had a tighter gel network, and CNFs had a better potential to improve the gelation performance of MP.  相似文献   
70.
Traditional West African pearl millet couscous products are popular; however, their preparation is laborious, time-consuming and energy-demanding, involving agglomeration, steaming, drying and sieving steps. In this study, a process was developed to produce millet couscous using a high pressure, high temperature and low-cost single-screw extruder. The innovation was to directly process the cooked low-moisture extrudate to a couscous product by drying and milling to the appropriate particle size (ranging between 1 and 2 mm). Throughput for the traditional process as prepared for commercial sale is 50 kg per day, but with the same amount of labour, the extrusion process yields ~350 kg per day. A consumer sensory study held in Niamey (Niger) showed that the extruded millet couscous was comparable to traditional couscous, though this was dependent on selection of the proper millet variety. This novel extrusion process could stimulate small- to medium-scale manufacturing of couscous and couscous-type products in West Africa.  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