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   468篇
  免费   51篇
  国内免费   4篇
电工技术   5篇
化学工业   164篇
金属工艺   5篇
机械仪表   11篇
建筑科学   9篇
矿业工程   2篇
能源动力   30篇
轻工业   55篇
水利工程   1篇
石油天然气   10篇
无线电   92篇
一般工业技术   53篇
冶金工业   10篇
原子能技术   3篇
自动化技术   73篇
  2024年   2篇
  2023年   5篇
  2022年   12篇
  2021年   22篇
  2020年   28篇
  2019年   44篇
  2018年   53篇
  2017年   50篇
  2016年   27篇
  2015年   15篇
  2014年   28篇
  2013年   28篇
  2012年   20篇
  2011年   19篇
  2010年   23篇
  2009年   15篇
  2008年   14篇
  2007年   8篇
  2006年   10篇
  2005年   9篇
  2004年   7篇
  2003年   9篇
  2002年   4篇
  2001年   8篇
  2000年   9篇
  1999年   7篇
  1998年   4篇
  1997年   4篇
  1996年   4篇
  1995年   3篇
  1994年   3篇
  1993年   2篇
  1992年   6篇
  1991年   2篇
  1990年   1篇
  1989年   2篇
  1988年   3篇
  1987年   3篇
  1985年   2篇
  1984年   3篇
  1982年   3篇
  1981年   1篇
  1974年   1篇
排序方式: 共有523条查询结果,搜索用时 15 毫秒
101.
102.
103.
Whole heated soybean oils and their polar fractions were analyzed for nonvolatile components by high-performance size-exclusion chromatography (HPSEC) with evaporative light scattering detection (ELSD). High molecular-weight (MW) polymer compounds with MW ≥ trimer were efficiently separated with new 3-μm mixed-bed styrene/divinylbenzene copolymer columns. Peaks of high MW polymer components in the new column system appeared to be sharper and more symmetrical than those obtained with other columns. In the model systems studied, continuous addition of water to partially simulate frying conditions resulted in a significant increase (up to 30%) in the polar lipid content of the heated oils evaluated. Due to relatively high concentrations of monomeric triglycerides (84.6–93.5%) present in the whole unfractionated oils, small but erratic variations in the compositional distribution of components were observed in oils containing different amounts of added water. On the other hand, HPSEC-ELSD analyses of the polar fractions (monomeric triglycerides, 25.4–62.6%) showed significant changes in the content and composition of nonvolatile components with the amount of water added. In general, prolonged heating with increasing amounts of water accelerated hydrolysis and polymerization of heated soybean oils. Discrepancies in total polymerization of heated soybean oils. Discrepancies in total polymeric materials obtained from HPSEC composition data for whole oils and polar fractions are discussed in terms of nonuniformity in sample matrices, detection limitations for minor components, and a nonlinear ELSD response rationale.  相似文献   
104.
Many radio-frequency circuits use differential topologies, whereas the instruments to evaluate them are inevitably single ended. Taking into account noise correlations, this work extends Friis' well-known equation for the noise figure of a cascade of two-ports to the case of three-ports, such as baluns, which surround a differential amplifier during measurements. The amplifier gain and noise figure may be accurately de-embedded with single-ended measurements on the cascade and on the baluns. The new formulas are experimentally validated  相似文献   
105.
Rare diseases (RDs) concern a broad range of disorders and can result from various origins. For a long time, the scientific community was unaware of RDs. Impressive progress has already been made for certain RDs; however, due to the lack of sufficient knowledge, many patients are not diagnosed. Nowadays, the advances in high-throughput sequencing technologies such as whole genome sequencing, single-cell and others, have boosted the understanding of RDs. To extract biological meaning using the data generated by these methods, different analysis techniques have been proposed, including machine learning algorithms. These methods have recently proven to be valuable in the medical field. Among such approaches, unsupervised learning methods via neural networks including autoencoders (AEs) or variational autoencoders (VAEs) have shown promising performances with applications on various type of data and in different contexts, from cancer to healthy patient tissues. In this review, we discuss how AEs and VAEs have been used in biomedical settings. Specifically, we discuss their current applications and the improvements achieved in diagnostic and survival of patients. We focus on the applications in the field of RDs, and we discuss how the employment of AEs and VAEs would enhance RD understanding and diagnosis.  相似文献   
106.
The objective of this study was to determine the inhibitory effect of royal jelly (RJ) and propolis on growth, aflatoxin production and aflR gene expression in Aspergillus parasiticus. Inhibitory effect of RJ and propolis against a standard strain of A. parasiticus(ATCC 15517) was determined alone and in combination in accordance with the CLSI M38-A2 and checkerboard methods, respectively. The aflatoxin concentrations in the control and treated media were determined by HPLC. Also, the quantitative changes in the aflR gene expression were analyzed. The minimum inhibitory concentrations (MIC) of RJ and propolis alone were 3,200 and 100μg/ml, respectively. Also, the MICs of RJ and propolis in combination were 200 and 25μg/ml, respectively. When combined, a synergistic interaction was observed with a FICI of 0.312. Total levels of aflatoxin decreased from 386.1ppm to 8.72, 3.01 and 1.75ppm at 1,600μg/ml of RJ, 50μg/ml of propolis and 100+12.5μg/ml of RJ and propolis, respectively. In addition, the level of afIR gene expression was significantly decreased after treatment with RJ and propolis extracts alone and with their combination. The findings reveal that RJ and propolis extracts, either alone or in combination, have a significant inhibitory effect on aflR gene expression in aflatoxin production.  相似文献   
107.
In this paper, a simple one-pot thermal decomposition method was successfully used to synthesize a novel Cs3PW12O40/WO3 composite for the first time. The synthesized composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), FTIR, diffuse reflectance spectroscopy (DRS) and N2 adsorption-desorption techniques. The photocatalytic activity to degrade RhB molecules over Cs3PW12O40/WO3 composite was evaluated under xenon light irradiation. The results indicated the complete degradation of RhB molecules over Cs3PW12O40/WO3 composite after 30?min irradiation. However, the photocatalytic degradation of RhB over WO3 and Cs3PW12O40 after 80?min light irradiation are nearly 52%, and 68%, respectively. The enhanced photocatalytic activity of Cs3PW12O40/WO3 composite compared with WO3, and Cs3PW12O40 was ascribed to the strong interaction between WO3 and Cs3PW12O40, which effectively reduces the recombination of photogenerated electron-hole pairs. Based on experimental results, the possible mechanism of photocatalytic reactions on the Cs3PW12O40/WO3 composite photocatalyst was investigated, and the hydroxyl radical (OH) and superoxide radical (O2?) were determined as the main active species in the photocatalytic degradation of RhB over Cs3PW12O40/WO3 composite.  相似文献   
108.
Sand production is one of the major problems in sandstone reservoirs. Different mechanical and chemical methods have been proposed to control sand production. In this paper, we propose a chemical method based on using polyacrylamide/chromium triacetate hydrogel to investigate sand production in a synthetic sandpack system. To this end, a series of bulk experiments including the bottle test and rheological analysis along with compression tests were conducted. Experimental results indicated that the compressive strength of the sandpack was increased as much as 30 times by injecting 0.5 pore volume of hydrogel. Also, it was found that the increases in cross-linker and polymer concentrations exhibited a positive impact on the compressive strength of the sandpack, mostly by cross-linker concentration(48 psi). Hydrogel with a higher value of cross-linker could retain its viscoelastic properties against the strain which was a maximum of 122% for 0.5 weight ratio of cross-linker/polymer. The presence of salts, in particular divalent cations, has a detrimental effect on the hydrogel stability. The maximum strain value applied on hydrogel in the presence of CaCl_2 was only about 201% as compared to 1010% in the presence of distilled water. Finally, thermogravimetric analysis and its derivative showed that the hydrogel could retain its structure up to 300 °C. The results of this study revealed the potential application of the hydrogel to control sand production.  相似文献   
109.
For detecting malicious bidding activities in e‐auctions, this study develops a chunk‐based incremental learning framework that can operate in real‐world auction settings. The self‐adaptive framework first classifies incoming bidder chunks to counter fraud in each auction and take necessary actions. The fraud classifier is then adjusted with confident bidders' labels validated via bidder verification and one‐class classification. Based on real fraud data produced from commercial auctions, we conduct an extensive experimental study wherein the classifier is adapted incrementally using only relevant bidding data while evaluating the subsequent adjusted models' detection and misclassification rates. We also compare our classifier with static learning and learning without data relevancy.  相似文献   
110.
Modern chemotherapeutic anticancer treatments have come a long way in the fight against breast cancer, thus bringing science closer to a cure. However, the nature of these drugs is to attack both cancerous and non-cancerous cells at the same time. In our studies, we synthesized Magnetic Cyclodextrin-polyurethane based nano-composite (Fe3O4-ECA-PU-CD) which is a drug delivery system using a biocompatible magnetic polymer that directs chemotherapeutic drugs to cancerous regions in the body with an external magnet. This nano-composite was able to facilitate the loading and simultaneous release of the hydrophilic antitumor drug Doxorubicin (DOX) along with the hydrophobic antitumor drug docetaxel. The composite was made using a simple co-precipitation method with magnetic nano-particles (MNPs) followed by a silica coating process and an in situ polymerization process. Verification of synthesis for the drug carrier was carried out using techniques such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and a vibrating sample magnetometer (VSM) to measure magnetic properties. Drug loading and release efficiencies were monitored using an HPLC-UV detector. Finally, an MTT assay was performed in order to evaluate the biocompatibility and toxicity of the synthetic nano-composite on MCF7 cell lines. Our findings present a new biocompatible drug delivery system with a high capacity for loading and directing two different chemotherapeutic drugs simultaneously to cancer sites with little to no toxicity to the surrounding non-cancerous cells. These studies present a viable tool for cancer treatment and research where the cancer is efficiently removed while the patient remains healthy.  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