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   305篇
  免费   9篇
电工技术   2篇
综合类   3篇
化学工业   85篇
金属工艺   3篇
机械仪表   2篇
建筑科学   20篇
能源动力   10篇
轻工业   78篇
水利工程   2篇
无线电   9篇
一般工业技术   44篇
冶金工业   11篇
自动化技术   45篇
  2023年   3篇
  2022年   10篇
  2021年   17篇
  2020年   8篇
  2019年   5篇
  2018年   8篇
  2017年   3篇
  2016年   3篇
  2015年   9篇
  2014年   17篇
  2013年   15篇
  2012年   13篇
  2011年   20篇
  2010年   17篇
  2009年   17篇
  2008年   19篇
  2007年   15篇
  2006年   11篇
  2005年   7篇
  2004年   12篇
  2003年   4篇
  2002年   7篇
  2001年   9篇
  2000年   2篇
  1999年   1篇
  1998年   6篇
  1997年   5篇
  1996年   3篇
  1995年   1篇
  1994年   4篇
  1993年   3篇
  1992年   1篇
  1991年   6篇
  1990年   1篇
  1989年   4篇
  1988年   1篇
  1986年   1篇
  1985年   3篇
  1983年   1篇
  1982年   5篇
  1981年   1篇
  1979年   2篇
  1978年   2篇
  1977年   2篇
  1975年   2篇
  1974年   3篇
  1973年   5篇
排序方式: 共有314条查询结果,搜索用时 31 毫秒
301.
302.
303.
A series of poly(ferrocenylsilane)s containing chloroalkyl side chains of increasing length is reported. By reacting fcLi2· tmeda with Cl2SiMeR, the corresponding [1]ferrocenophanes were prepared (2a, R=CH2Cl; 2b, R=CH2CH2Cl; and 2c, R=CH2CH2CH2Cl). Transition metal-catalyzed or thermal ring-opening polymerization (ROP) of these monomers yielded the polyferrocenes 3a, 3b, and 3c. The chlorine substituents of polymers 3a and 3b were unreactive toward nucleophilic substitution. In contast, polymer 3c could be reacted with 4-dimethylaminopyridine in DMF to afford the water-soluble poly(ferrocenylsilane) 4. This represents a new method for the preparation of water-soluble polyferrocenes.  相似文献   
304.
Governments and corporations are increasingly adopting circular economy strategies to meet the need of decoupling growth from resource consumption. However, the world economy is far from being circular, with some of the reasons including lack of transparency, standardization, and data sharing. Digitalization can help overcome these challenges, thus making it a key enabler of the circular economy. This review looks at the concept of a digital product passport as a tool for implementing and scaling the circular economy. It discusses opportunities and challenges related to further development and adoption of digital product passports. Finally, it examines the battery passport, drafted in the EU Battery regulation, as one of the first examples of a digital product passport required by law.  相似文献   
305.
杨莉莉 《门窗》2007,(1):51-54
木窗,包括纯木窗,铝包木窗和木铝复合窗,作为一种相对新兴的窗型,近些年在国内发展迅速.而作为一种成熟产品,木窗在欧洲已经存在完整的生产和安装标准.我们可以借鉴国外的成熟技术加速自身完善.  相似文献   
306.
The sn position of fatty acids in seed oil lipids affects physiological function in pharmaceutical and dietary applications. In this study the composition of acyl-chain substituents in the sn positions of glycerol backbones in triacylglycerols (TAG) have been compared. TAG from native and transgenic medium-chain fatty acid-enriched rape seed oil were analyzed by reversed-phase high performance liquid chromatography coupled with online atmospheric-pressure chemical ionization ion-trap mass spectrometry. The transformation of summer rape with thioesterase and 3-ketoacyl-[ACP]-synthase genes of Cuphea lanceolata led to increased expression of 1.5% (w/w) caprylic acid (8:0), 6.7% (w/w) capric acid (10:0), 0.9% (w/w) lauric acid (12:0), and 0.2% (w/w) myristic acid (14:0). In contrast, linoleic (18:2n6) and alpha-linolenic acid (18:3n3) levels decreased compared with the original seed oil. The TAG sn position distribution of fatty acids was also modified. The original oil included eleven unique TAG species whereas the transgenic oil contained sixty. Twenty species were common to both oils. The transgenic oil included trioctadecenoyl-glycerol (18:1/18:1/18:1) and trioctadecatrienoyl-glycerol (18:3/18:3/18:3) whereas the native oil included only the latter. The transgenic TAG were dominated by combinations of caprylic, capric, lauric, myrisitic, palmitic (16:0), stearic (18:0), oleic (18:1n9), linoleic, arachidic (20:0), behenic (22:0), and lignoceric acids (24:0), which accounted for 52% of the total fat. In the original TAG palmitic, stearic, oleic, and linoleic acids accounted for 50% of the total fat. Medium-chain triacylglycerols with capric and lauric acids combined with stearic, oleic, linoleic, alpha-linolenic, arachidic, and gondoic acids (20:1n9) accounted for 25% of the transgenic oil. The medium-chain fatty acids were mainly integrated into the sn-1/3 position combined with the essential linoleic and alpha-linolenic acids at the sn-2 position. Eight species contained caprylic, capric, and lauric acids in the sn-2 position. The appearance of new TAG in the transgenic oil illustrates the extensive effect of genetic modification on fat metabolism by transformed plants and offers interesting possibilities for improved enteral applications.  相似文献   
307.
Total and individual glucosinolate contents of broccoli cv Marathon were assessed at ambient CO2 (430–480 ppm) and elevated atmospheric CO2 (685–820 ppm) to determine the ecological relationship between changing atmospheric CO2 concentrations and phytochemicals. Elevated atmospheric CO2 concentration had a differing effect on individual glucosinolates and glucosinolate groups. Total glucosinolate content increased at elevated atmospheric CO2 concentration as a result of a strong increase in both methylsulfinylalkyl glucosinolates glucoraphanin and glucoiberin. In contrast, indole glucosinolates simultaneously decreased, predominantly because of a reduction of glucobrassicin and 4-methoxy-glucobrassicin contents. We conclude that changes in N content and N/S ratios as well as alterations in photochemical processes at elevated atmospheric CO2 concentration can influence total and individual glucosinolates contents of Brassicaceae, as demonstrated in the greenhouse, for broccoli.  相似文献   
308.
309.
A single-chip electrochemical method based on impedance measurements in resonance mode has been employed to study lipid monolayer and bilayer formation on hydrophobic alkanethiolate and SiO(2) substrates, respectively. The processes were monitored by temporally resolving changes in interfacial capacitance and resistance, revealing information about the rate of formation, coverage, and defect density (quality) of the layers at saturation. The resonance-based impedance measurements were shown to reveal significant differences in the layer formation process of bilayers made from (i) positively charged lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-ethylphosphocholine (POEPC), (ii) neutral lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) on SiO(2), and (iii) monolayers made from POEPC on hydrophobic alkanethiolate substrates. The observed responses were represented with an equivalent circuit, suggesting that the differences primarily originate from the presence of a conductive aqueous layer between the lipid bilayers and the SiO(2). In addition, by adding the ion channel gramicidin D to bilayers supported on SiO(2), channel-mediated charge transport could be measured with high sensitivity (resolution around 1 pA).  相似文献   
310.

1 Scope

Wholegrain has been associated with reduced chronic disease mortality, with oat intake particularly notable for lowering blood cholesterol and glycemia. To better understand the complex nutrient profile of oats, we studied urinary excretion of phenolic acids and avenanthramides after ingestion of oat bran in humans.

2 Methods and results

After a 2‐d (poly)phenol‐low diet, seven healthy men provided urine 12 h before and 48 h after consuming 60 g oat bran (7.8 μmol avenanthramides, 139.2 μmol phenolic acids) or a phenolic‐low (traces of phenolics) control in a crossover design. Analysis by ultra‐high performance liquid chromatography (UPLC)–MS/MS showed that oat bran intake resulted in an elevation in urinary excretion of 30 phenolics relative to the control, suggesting that they are oat bran‐derived. Mean excretion levels were elevated between 0–2 and 4–8 h, following oat bran intake, and amounted to a total of 33.7 ± 7.3 μmol total excretion (mean recovery: 22.9 ± 5.0%), relative to control. The predominant metabolites included: vanillic acid, 4‐ and 3‐hydroxyhippuric acids, and sulfate‐conjugates of benzoic and ferulic acids, which accounted collectively for two thirds of total excretion.

3 Conclusion

Oat bran phenolics follow a relatively rapid urinary excretion, with 30 metabolites excreted within 8 h of intake. These levels of excretion suggest that bound phenolics are, in part, rapidly released by the microbiota.  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