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   474篇
  免费   10篇
电工技术   18篇
综合类   2篇
化学工业   192篇
金属工艺   18篇
机械仪表   9篇
建筑科学   4篇
矿业工程   1篇
能源动力   12篇
轻工业   83篇
石油天然气   1篇
无线电   19篇
一般工业技术   70篇
冶金工业   22篇
原子能技术   7篇
自动化技术   26篇
  2023年   3篇
  2022年   14篇
  2021年   12篇
  2020年   8篇
  2019年   8篇
  2018年   6篇
  2017年   5篇
  2016年   8篇
  2015年   11篇
  2014年   16篇
  2013年   31篇
  2012年   24篇
  2011年   35篇
  2010年   17篇
  2009年   24篇
  2008年   28篇
  2007年   25篇
  2006年   28篇
  2005年   12篇
  2004年   12篇
  2003年   18篇
  2002年   14篇
  2001年   9篇
  2000年   11篇
  1999年   12篇
  1998年   7篇
  1997年   12篇
  1996年   4篇
  1995年   4篇
  1994年   4篇
  1993年   3篇
  1992年   4篇
  1991年   6篇
  1990年   4篇
  1988年   1篇
  1987年   1篇
  1986年   5篇
  1985年   4篇
  1984年   6篇
  1983年   2篇
  1982年   3篇
  1980年   2篇
  1979年   4篇
  1978年   2篇
  1977年   4篇
  1976年   5篇
  1975年   2篇
  1974年   1篇
  1971年   1篇
  1969年   1篇
排序方式: 共有484条查询结果,搜索用时 0 毫秒
471.
During the course of our studies to develop new uses for the Noni (Morinda citrifolia) root, 10 anthraquinones, rubiadin (1), rubiadin 1-methyl ether (2), lucidin (3), damnacanthol (4), 1,3-dihydroxy-2-methoxymethylanthraquinone (5), 3-hydroxy-1-methoxy-2-methoxymethylanthraquinone (6), nordamnacanthal (7), damnacanthal (8), sorandidiol (9) and morindone (10), were isolated. Compounds 5, 6, 7, 8 and 10 exhibited remarkable inhibition against the activities of animal pols, and compound 10 was the strongest inhibitor in the anthraquinones investigated. Among mammalian pols, compound 10 inhibited the pol activities of A- (pol γ), B- (pols α, δ and ε) and Y- (pols η, ι and κ) families, but did not influence the activities of X-family pols (pols β, λ and terminal deoxynucleotidyl transferase). The tendency of pol inhibition showed a positive correlation with the suppression of human colon cancer cell HCT116 growth. These results suggested that the Noni root containing anthraquinones may be used as an anticancer functional food.  相似文献   
472.
Journal of Materials Science - The effects of aging on the mechanical properties of a heavily cold-rolled ferrite–austenite duplex stainless steel were systematically investigated. The...  相似文献   
473.
We report on the open‐circuit voltage recovery in GaSb quantum ring (QR) solar cells under high solar concentration up to 2500 suns. The detailed behaviour of type II GaSb/GaAs QR solar cells under solar concentration, using different temperatures and light illumination conditions, is analysed through optical and electrical measurements. Although enhancement of the short‐circuit current was observed because of sub‐bandgap photon absorption in the QR, the thermionic emission rate of holes was found to be insufficient for ideal operation. The direct excitation of electron–hole pairs into QRs has revealed that the accumulation of holes is one of the causes of the open‐circuit voltage (VOC) degradation. However, using concentrated light up to 2500 suns, the GaSb QR cell showed much quicker VOC recovery rate than a GaAs control cell. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
474.
Thiabendazole (TBZ), a pesticide with antifungal activity, was detected in toasted and seasoned laver which had been reported as tasting unpleasant by consumers in March 2008. From a survey of the manufacturing process, it was concluded that the TBZ contamination had originated from a sponge-roller which was used to paste seasoned liquid onto the toasted laver. At that time it was found that TBZ is widely used to prevent fungal contamination of sponge-rollers. For further survey of TBZ contamination in the laver, we developed a more sensitive detection method using LC-MS/MS. With our new method, six commercial products harvested in March 2008 and July 2009, respectively, were tested. Five out of six samples harvested in 2008 were positive for TBZ, with values in the range from 0.014 to 1.736 μg/g. Only one sample harvested in 2009 contained a detectable level of TBZ. The data obtained here contributed to the improvement of the manufacturing process.  相似文献   
475.
Imura K  Ueno K  Misawa H  Okamoto H 《Nano letters》2011,11(3):960-965
We report an anomalous light transmission phenomenon for a nanoaperture on an opaque screen when the aperture is covered with an opaque cap. In conventional optics, light transmission must decrease when the aperture is capped. However, we found that light transmission is enhanced when the nanodisk is in close proximity to the aperture at a wavelength close to the plasmon resonance. This effect even occurs when the disk is larger than the aperture.  相似文献   
476.
The increasing use of nanomaterials has raised concerns about their potential risks to human health. Recent studies have shown that nanoparticles can cross the placenta barrier in pregnant mice and cause neurotoxicity in their offspring, but a more detailed understanding of the effects of nanoparticles on pregnant animals remains elusive. Here, we show that silica and titanium dioxide nanoparticles with diameters of 70 nm and 35 nm, respectively, can cause pregnancy complications when injected intravenously into pregnant mice. The silica and titanium dioxide nanoparticles were found in the placenta, fetal liver and fetal brain. Mice treated with these nanoparticles had smaller uteri and smaller fetuses than untreated controls. Fullerene molecules and larger (300 and 1,000 nm) silica particles did not induce these complications. These detrimental effects are linked to structural and functional abnormalities in the placenta on the maternal side, and are abolished when the surfaces of the silica nanoparticles are modified with carboxyl and amine groups.  相似文献   
477.
BACKGROUND: The fatty acid distribution of triacylglycerols (TAG) and major phospholipids (PL) obtained from four varieties of peas (Pisum sativum) was investigated. The total lipids extracted from the peas were separated by thin layer chromatography into seven fractions. RESULTS: The major lipid components were PL (52.2–61.3%) and TAG (31.2–40.3%), while hydrocarbons, steryl esters, free fatty acids and diacylglycerols (sn‐1,3 and sn‐1,2) were also present in minor proportions (5.6–9.2%). The main PL components isolated from the four varieties were phosphatidylcholine (42.3–49.2%), phosphatidylinositol (23.3–25.2%) and phosphatidylethanolamine (17.7–20.5%). Significant differences (P < 0.05) in fatty acid distribution were found for different pea varieties. Phosphatidylinositol was unique in that it had the highest saturated fatty acid content among the three PL. However, the principal characteristics of the fatty acid distribution in the TAG and three PL were evident among the four varieties: unsaturated fatty acids were predominantly located in the sn‐2 position while saturated fatty acids primarily occupied the sn‐1 or sn‐3 position in the oils of the peas. CONCLUSION: These results should be useful to both producers and consumers for the manufacture of pea foods in Japan. Copyright © 2007 Society of Chemical Industry  相似文献   
478.
城市轨道交通梯形轨枕轨道高架桥梁试验研究   总被引:2,自引:0,他引:2  
作为一种新型的减振轨道,梯形轨枕轨道已在国内的城市轨道交通中有所应用.该文介绍了在北京地铁五号线高架桥梯形轨枕轨道试验段进行的一系列现场试验,以及为验证其减振特性进行的室内试验.通过对轨道不平顺进行测量,并测试了当列车分别运行在梯形轨枕轨道和普通无碴板式轨道上时钢轨、轨枕和桥面的振动响应,该文对测试数据在时域和频域进行...  相似文献   
479.
Infectious complications and subsequent sepsis in severely burned patients lead to high morbidity and mortality in response to uncontrolled innate immune responses mediated by macrophages. Peroxisome proliferator-activated receptor gamma (PPARγ) has anti-inflammatory activity and acts as a master regulator of macrophage polarization. In this study, we investigated whether the administration of a PPARγ agonist could modulate the Kupffer cell phenotype and thereby ameliorate the dysregulated innate response during post-burn bacterial infection. C57BL/6 mice were subjected to severe burns and randomized to receive either the PPARγ agonist, pioglitazone, or the vehicle control five days after injury, followed by the subsequent analysis of hepatic macrophages. Survival from the bacterial infection was monitored for seven days. Pioglitazone protected burned mice against bacterial infection. A single treatment with pioglitazone significantly enhanced phagocytosis, phagosome acidification, bacterial clearance, and reduction in inflammatory mediators in Kupffer cells. In conclusion, PPARγ activation by pioglitazone prevents clinical deterioration due to post-burn bacterial infection and improves survival. Our findings suggest that pioglitazone may be an effective therapeutic candidate for post-burn infectious complications.  相似文献   
480.
Aspergillus westerdijkiae is a new species of fungus that was recently dismembered from Aspergillus ochraceus taxon. Most isolates of A. westerdijkiae are able to produce large amounts of a mycotoxin called ochratoxin A (OA). OA has been found in food and beverages, such as coffee. A. westerdijkiae is very similar to A. ochraceus, and several isolates previously identified as A. ochraceus are now identified as A. westerdijkiae. By using sequences of the beta-tubulin gene, we analyzed several isolates from Brazilian coffee bean samples, previously identified as A. ochraceus, to compare with those of A. westerdijkiae. In fact, most (84%) were identified as A. westerdijkiae. Since this species consistently produces large amounts of OA, we developed a specific primer-pair for detecting and quantifying it in coffee beans by using real-time PCR. The primers Bt2Aw-F 5'TGATACCTTGGCGCTTGTGACG and Bt2Aw-R 5'CGGAAGCCTAAAAAATGAAGAG provided an amplicon of 347 bp in all A. westerdijkiae isolates, and no cross-reaction was observed using DNA from A. ochraceus. The sensitivity of real-time PCR was more than 100 times higher than the cfu technique.  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