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   62288篇
  免费   3359篇
  国内免费   190篇
电工技术   940篇
综合类   89篇
化学工业   12861篇
金属工艺   2515篇
机械仪表   4037篇
建筑科学   1403篇
矿业工程   30篇
能源动力   2569篇
轻工业   4765篇
水利工程   342篇
石油天然气   118篇
武器工业   2篇
无线电   10335篇
一般工业技术   13059篇
冶金工业   4964篇
原子能技术   801篇
自动化技术   7007篇
  2024年   30篇
  2023年   628篇
  2022年   799篇
  2021年   1751篇
  2020年   1275篇
  2019年   1408篇
  2018年   1743篇
  2017年   1689篇
  2016年   2115篇
  2015年   1604篇
  2014年   2605篇
  2013年   3905篇
  2012年   3997篇
  2011年   4765篇
  2010年   3471篇
  2009年   3684篇
  2008年   3486篇
  2007年   2783篇
  2006年   2596篇
  2005年   2209篇
  2004年   2027篇
  2003年   1923篇
  2002年   1798篇
  2001年   1478篇
  2000年   1322篇
  1999年   1236篇
  1998年   2057篇
  1997年   1304篇
  1996年   1059篇
  1995年   766篇
  1994年   645篇
  1993年   579篇
  1992年   395篇
  1991年   380篇
  1990年   355篇
  1989年   339篇
  1988年   263篇
  1987年   239篇
  1986年   172篇
  1985年   168篇
  1984年   134篇
  1983年   88篇
  1982年   60篇
  1981年   70篇
  1980年   48篇
  1979年   42篇
  1978年   48篇
  1977年   55篇
  1976年   87篇
  1973年   32篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
51.
Food Science and Biotechnology - Buah merah oil and red palm oil are red colored and unrefined edible oils. Because of this color characteristic, measuring acid value by titration method can be...  相似文献   
52.
This study presents a back-analysis of geotechnical parameters on prefabricated vertical drain improved ground at a site in the Mekong Delta. Various time?settlement behaviors that reflected different clay thicknesses and loading patterns were observed. The total surface settlement behavior at several monitoring locations was simulated using an updated exponential method that considered staged construction. The analyzed results were validated by substituting the values into a theoretical solution for radial consolidation. The estimated theoretical behaviors were comparable with the monitored behaviors. The geotechnical parameters were back-analyzed by applying the previously analyzed results to various theoretical and empirical formulas. However, the use of extensometer data that were installed at large intervals produced different values of the geotechnical properties. Furthermore, finite element analysis supported the back-analyzed total settlement behaviors and nearly disregarded the application of the geotechnical properties that were obtained using either surface or subsurface settlement data. However, settlements and excess pore pressures in the sublayers were not successfully predicted even when the geotechnical properties were adjusted. Thus, subsurface instruments that can be installed closely in thick clay deposits are required to reliably reevaluate the variations in geotechnical properties along a certain depth.  相似文献   
53.
To modify the glycan part of glycosides, the gene encoding β‐glycosidase was cloned from Bacteroides thetaiotaomicron VPI‐5482. The cloned gene, bt_1780, was expressed in Escherichia coli MC1061 and the expressed enzyme was purified using Ni‐NTA affinity chromatography. The purified enzyme, BTBG, showed optimal activity at 50 °C and pH 5.5. Interestingly, this enzyme did not have any hydrolysing activity on ordinary β‐linkage–containing substrates such as xylobiose, lactose and cello‐oligosaccharide, but specifically hydrolysed isoflavone glycosides such as daidzin, genistin and glycitin. Compared to a commercial beta glucosidase, BTBG selectively hydrolysed isoflavone glycosides in soybean extract mixture solution. These results suggest that BTBG may be a specialized enzyme for the hydrolysis of glycosides and that the substrate specificity of BTBG is applicable for the bioconversion of isoflavone glycosides in the food industry.  相似文献   
54.
Peer-to-Peer Networking and Applications - Recently, as the P2P service environment repeats evolution, its usage in mobile is rapidly increasing. Applications are being developed in various mobile...  相似文献   
55.
56.
57.
58.
Recent studies have shown that lotus (Nelumbo nucifera) leaf has various pharmacological effects. However, there have been no scientific investigations into these leaves as a fermented crude liquid. This study compared the in vitro antioxidant capacity of lotus leaf‐fermented broth (LLFB) with that of 57° Brix sugar broth (SB) as a control over a period of 6 months based on 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity, ferric ion reducing power, superoxide dismutase‐like activity, tyrosinase inhibition and nitrite scavenging activity. The dominant species during fermentation process were Leuconostoc lactis and Saccharomyces cerevisiae for LLFB. A total of thirty‐six metabolites such as alkaloids, fatty acids, organic acids, phenolics, sugar and sugar derivatives, ethyl esters and monoterpenoids differed between SB and LLFB using gas chromatography–mass spectrometry. Meanwhile, nine volatile compounds in LLFB contributed pleasant, slightly sweetish and fruity odour of condiment and sensory evaluation score of 4.06 ± 1.52 in the proportion of 1:9 LLFB/water.  相似文献   
59.
60.
Many e-commerce companies collect users’ personal data for marketing purposes despite privacy concerns. Information-collecting companies often offer a monetary reward to users to alleviate privacy concerns and ease the collection of personal information. This study focused on the negative effects of monetary rewards on both information privacy concerns (IPC) and information disclosure. A survey approach was used to collect data and 370 final responses were analysed using a two-way analysis of variance and a binomial logistic regression model. The results show that monetary rewards increase IPC when an information-collecting company requires sensitive information. Additional results indicate that building trust is a more effective way of collecting personal data. This study identifies how organisations can best execute information-collection activities and contributes additional insights for academia and practitioners.  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