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   141篇
  免费   3篇
化学工业   53篇
金属工艺   2篇
机械仪表   1篇
建筑科学   5篇
能源动力   5篇
轻工业   9篇
无线电   5篇
一般工业技术   23篇
冶金工业   27篇
原子能技术   1篇
自动化技术   13篇
  2023年   2篇
  2022年   9篇
  2021年   15篇
  2020年   5篇
  2019年   2篇
  2018年   3篇
  2017年   7篇
  2016年   3篇
  2015年   3篇
  2014年   5篇
  2013年   12篇
  2012年   4篇
  2011年   4篇
  2010年   4篇
  2009年   3篇
  2008年   3篇
  2007年   4篇
  2006年   3篇
  2005年   6篇
  2004年   3篇
  2003年   6篇
  2001年   2篇
  1999年   1篇
  1998年   5篇
  1997年   5篇
  1996年   6篇
  1993年   1篇
  1992年   1篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1982年   1篇
  1980年   1篇
  1975年   2篇
  1974年   1篇
  1969年   1篇
  1968年   2篇
排序方式: 共有144条查询结果,搜索用时 31 毫秒
111.
112.
Non-alcoholic fatty liver disease (NAFLD) is a spectrum of metabolic abnormalities ranging from simple triglyceride accumulation in the hepatocytes to hepatic steatosis with inflammation, ballooning and fibrosis. It has been demonstrated that the pathogenesis of NAFLD involves increased oxidative stress, with consumption of the major cellular antioxidant, glutathione (GSH). Liver has a fundamental role in sulfur compound metabolism, although the data reported on plasma thiols status in NAFLD are conflicting. We recruited 63 NAFLD patients, and we analyzed all plasma thiols, such as homocysteine (Hcy), cysteine (Cys), cysteinylglycine (CysGly) and GSH, by high-performance liquid chromatography (HPLC) with fluorescence detection. Hcy, Cys and CysGly plasma levels increased in NAFLD patients (p < 0.0001); whereas GSH levels were decreased in NAFLD patients when compared to controls (p < 0.0001). On the contrary, patients with steatohepatitis exhibited lower levels of Hcy and Cys than subjects without. Furthermore, a positive correlation was found between Hcy and Cys and the presence of fibrosis in children with NAFLD. Taken together, these data demonstrated a defective hepatic sulfur metabolism in children with NAFLD, and that high levels of Hcy and Cys probably correlates with a pattern of more severe histological liver damage, due to mechanisms that require further studies.  相似文献   
113.
The precipitation of P in the emitter region of H3PO4 spray doped silicon for solar cell applications has been investigated by electron microscopy, X-ray microanalysis and electrical measurements after annealing for two different times. P, Si and O concentration profiles show that the composition of the phosphorous silicate glass (PSG) is in agreement with a solid solution of P2O5 in SiO2 and that P concentration is peaked at the PSG/Si interface. TEM observations have shown for the shorter annealing the formation of a 20 nm thick defect layer at the silicon surface; this layer evolves into a network of large rod-like monoclinic (or orthorhombic) SiP precipitates, which extend in depth up to about 100 nm for the longer treatment. The SiP crystal structure and the habit planes are the same as previously reported in literature. No deeper defect that could interact with the junction located at about 300 nm has been detected. Although the SiP precipitation takes place entirely at the Si surface, it is not significantly affected by the orientation of the crystals and by the texturing process. The amounts of both electrically active and inactive P obtained by the H3PO4 spray technique have been compared with the ones obtained by the conventional POCl3 technique. The former process presents a larger amount of inactive dopant, a finding that is in keeping with the microstructural and microanalytical observations. Instead the amount of active P is similar in the two cases, a result attributed to the precipitation and clustering phenomena of the excess dopant.  相似文献   
114.
The development of multifunctional 3D printing materials from sustainable natural resources is a high priority in additive manufacturing. Using an eco-friendly method to transform hard pollen grains into stimulus-responsive microgel particles, we engineered a pollen-derived microgel suspension that can serve as a functional reinforcement for composite hydrogel inks and as a supporting matrix for versatile freeform 3D printing systems. The pollen microgel particles enabled the printing of composite inks and improved the mechanical and physiological stabilities of alginate and hyaluronic acid hydrogel scaffolds for 3D cell culture applications. Moreover, the particles endowed the inks with stimulus-responsive controlled release properties. The suitability of the pollen microgel suspension as a supporting matrix for freeform 3D printing of alginate and silicone rubber inks was demonstrated and optimized by tuning the rheological properties of the microgel. Compared with other classes of natural materials, pollen grains have several compelling features, including natural abundance, renewability, affordability, processing ease, monodispersity, and tunable rheological features, which make them attractive candidates to engineer advanced materials for 3D printing applications.  相似文献   
115.
l-(+)-Ascorbic acid (AA) was compartmentalized into a low methoxyl pectin (LMP) film in view of localized antioxidant activity at food interfaces. The AA hydrolysis was specifically studied in the present work in order to determine the ability of the formulated LMP film to stabilize AA. Hence, films were stored at controlled relative humidity (RH) in the absence of air. A commercial LMP characterized by a 40% degree of methylesterification (DM) was used. Since sucrose is normally added for its standardization, films were also made with the dialyzed LMP in order to determine the sucrose effect. Glycerol was used for plasticization. Kinetics of AA loss and subsequent browning development were determined, which are dependent on the RH. Considerable AA retention (t 1/2?=?744, 727, and 185 days) was achieved at 33.3%, 57.7%, or 75.2% RH, respectively, at 25 °C. Browning rate constants decreased in one order of magnitude with respect to kinetic constants determined from films previously developed with high methoxyl pectin (HMP; DM of 73%). Absence of sucrose in the LMP network only affected the browning kinetics at 75.2% RH. The glass transition temperature (T g) decreased with the increment of moisture content of the films and in a similar degree (T g?≈??90 °C) to that observed for the HMP films, indicating the contribution of water to the network plasticization. However, water was more confined in the LMP network as inferred from the water availability determined by the 1H-NMR and DSC. This was attributed to the water interaction at the Ca2+ junction zones. Sucrose seemed to hinder the retention of water molecules by the polymeric network at 75.2% RH.  相似文献   
116.
Two laboratory experiments investigated the hypothesis that threat to male identity would increase the likelihood of gender harassment. In both experiments, using the computer harassment paradigm, male university students (N=80 in Experiment 1, N=90 in Experiment 2) were exposed to different types of identity threat (legitimacy threat and threat to group value in Experiment 1 and distinctiveness threat and prototypicality threat in Experiment 2) or to no threat and were then given the opportunity to send pornographic material to a virtual female interaction partner. Results show that (a) participants harassed the female interaction partner more when they were exposed to a legitimacy, distinctiveness, or prototypicality threat than to no threat; (b) this was mainly true for highly identified males; and (c) harassment enhanced postexperimental gender identification. Results are interpreted as supporting a social identity account of gender harassment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
117.
The results of a test programme of a completely fluorinated organic fluid solar engine at fluid temperatures around 250°C are Engine design characteristics. as deduced using the particular fluid properties are briefly described problems encountered in the preliminary test phase and relating to fluid losses, heat exchangers reduced performance and minor mechanical disturbances are illustrated together with the actions undertaken to improve the original engine behaviour. Detailed engine overall and components performance, as derived from a series of tests, carried out with a fuel fired heat source (simulating the actual solar heating loop) are presented. Engine efficiency, with reference to the net power output at the high speed shaft proved to be around 21%, at 250°C turbine inlet temperature which can be compared with 22.6% design value at the same temperature and with 23.6% original goal at 280°C top cycle temperature. The analysis of the heat transfer coefficients within the various heat exchangers support the suspicion that available information on working fluid transport properties is not sufficiently accurate.  相似文献   
118.
The electrochemical behavior of partially oxidized graphite electrodes coated with 50 Å thick Au, Cu, In, Pb or Sn layers has been studied by slow scan rate cyclic voltammetry and galvanostatic charge–discharge. Electrochemical impedance spectroscopy (EIS) has also been applied to Cu- and Sn-coated electrodes in order to study the effect of the metal coating on the interfacial intercalation/deintercalation kinetics.

The results demonstrate that certain metallic layers produce remarkable improvements of intercalation kinetics of graphite electrodes by reducing the charge-transfer and the solid–electrolyte interface (SEI) resistance making this type of surface modification attractive for the development of high rate anodes for lithium-ion batteries.  相似文献   

119.
The variation in the antioxidant content (lycopene, β-carotene, ascorbic acid and total phenolics) was evaluated on two tomato genotypes during vine and post-harvest ripening. Tomatoes were sampled and analysed at seven ripening stages according to the colour value. The data indicate that ripening conditions affected both the antioxidant accumulation kinetics and the final content, which was higher in post-harvest-ripened fruits. In particular, lycopene mainly accumulated in the very last period of ripening and its content was not linearly related to colour changes. Antioxidant accumulation and other ripening indexes were not significantly different in the two tomato genotypes. © 1999 Society of Chemical Industry  相似文献   
120.
Improvements in microarray-based comparative genomic hybridization technology have allowed for high-resolution detection of genome wide copy number alterations, leading to a better definition of rearrangements and supporting the study of pathogenesis mechanisms. In this study, we focused our attention on chromosome 8p. We report 12 cases of 8p rearrangements, analyzed by molecular karyotype, evidencing a continuum of fragility that involves the entire short arm. The breakpoints seem more concentrated in three intervals: one at the telomeric end, the others at 8p23.1, close to the beta-defensin gene cluster and olfactory receptor low-copy repeats. Hypothetical mechanisms for all cases are described. Our data extend the cohort of published patients with 8p aberrations and highlight the need to pay special attention to these sequences due to the risk of formation of new chromosomal aberrations with pathological effects.  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