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   340篇
  免费   12篇
  国内免费   3篇
电工技术   2篇
化学工业   75篇
金属工艺   5篇
机械仪表   11篇
建筑科学   10篇
能源动力   12篇
轻工业   34篇
水利工程   1篇
石油天然气   1篇
无线电   39篇
一般工业技术   84篇
冶金工业   12篇
原子能技术   5篇
自动化技术   64篇
  2024年   1篇
  2023年   11篇
  2022年   18篇
  2021年   37篇
  2020年   21篇
  2019年   38篇
  2018年   32篇
  2017年   14篇
  2016年   11篇
  2015年   7篇
  2014年   13篇
  2013年   34篇
  2012年   14篇
  2011年   15篇
  2010年   7篇
  2009年   3篇
  2008年   6篇
  2007年   6篇
  2006年   3篇
  2005年   2篇
  2004年   5篇
  2003年   3篇
  2002年   2篇
  2001年   1篇
  2000年   1篇
  1999年   5篇
  1998年   8篇
  1997年   3篇
  1996年   5篇
  1995年   2篇
  1993年   1篇
  1992年   7篇
  1991年   3篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
排序方式: 共有355条查询结果,搜索用时 15 毫秒
71.
72.
Herein we report the micellization and cloud point of an amitriptyline hydrochloride (AMT) under the influence of cationic, anionic and nonionic hydrotropes. Anionic hydrotropes were employed to know the micellar and surface behaviors, besides studying the clouding behavior of AMT drug with cationic, anionic and nonionic hydrotropes. Tensiometric study has been performed and the properties studied include the critical micelle concentration (cmc), maximum surface excess at the air/water interface (Γmax), the minimum area per of amphiphilic molecule at air/water interface (Amin), and the different thermodynamic parameters, besides clouding phenomenon. Interaction parameters of micelles (βm) and monolayer (βσ) indicate that drug-hydrotrope systems show better interaction at the interface than in micelles.  相似文献   
73.
Chemical oxidative polymerization of aniline (AN) and o-toluidine (OT) for the synthesis of copolymer, Poly(AN-co-OT) and its composite with TiO2 nanoparticles, Poly(AN-co-OT)/TiO2 employing ammonium persulfate as an oxidant and HCl as an external dopant were carried out. The homopolymers, Polyaniline and Poly(o-toluidine) were also prepared by following similar method. The synthesized polymers were characterized with FTIR spectroscopy, XRD/SEM/TEM analysis. The anticorrosive coatings were synthesized in dimethyl sulfoxide solution by dissolving synthesized polymers, and then were applied on low-carbon steel (LCS) samples using epoxy binder. The anticorrosive potential of the polymer coatings containing copolymer, copolymer-nanocomposite and homopolymers on LCS was evaluated in 3.5% NaCl at a temperature of 30?°C by open circuit potential, electrochemical impedance spectroscopy and potentiodynamic polarization measurements. It was observed that the nanocomposite coating increases the protection efficacy by providing better barrier properties against corrosion as compared with neat copolymer and homopolymers coatings. The morphology of the coatings before and after 60 days LCS immersion in 3.5% NaCl solution was determined using SEM.  相似文献   
74.
In this work, Fe3O4@SiO2 nanoparticles were coated with mesoporous silica shell by SN+I pathway by using anionic surfactant (S) and co-structure directing agent (N+). The role of co-structure directing agent (CSDA) is to assist the electrostatic interaction between negatively charged silica layers and the negatively charged surfactant molecules. Prior to the mesoporous shell formation step, magnetic cores were coated with a dense silica layer to prevent iron oxide cores from leaching into the mother system under any acidic circumstances. However, it was found that both dense and mesoporous coating parameters affect the textural properties of the produced mesoporous silica shell (i.e., surface area, pore volume and shell thickness). The synthesized Fe3O4@SiO2@m-SiO2 (MCMSS) nanoparticles have been characterized by low-angle X-ray diffraction, transmission electron microscopy (TEM), and N2 adsorption-desorption analysis, and magnetic properties. The synthesized particles had dense and mesoporous silica shells of 8–37 nm and 26–50 nm, respectively. Furthermore, MCMSS possessed surface area of ca. 259–621 m2·g−1, and pore volume of ca. 0.216–0.443 cc·g−1. MCMSS showed docetaxcel cancer drug storage capacity of 25–33 w/w% and possessed control release from their mesochannels which suggest them as proper nanocarriers for docetaxcel molecules.  相似文献   
75.
Graphene oxide (GO) incorporated ultra-high molecular weight polyethylene (UHMWPE) nanocomposites were prepared by encapsulating GO by UHMWPE in an aqueous media via high-shear mixing, which were subsequently dried and compression molded. Morphological characterizations via scanning electron microscopy revealed the intercalation of UHMWPE chains in the graphitic stacks corresponding to GO. Further, dielectric permittivity of UHMWPE/GO nanocomposite of 1 wt% GO showed a drastic increase (~61) as compared to pure UHMWPE (~2) due to an enhanced interfacial polarization. A significantly higher value of remnant polarization (~10 nC/cm2) and coercive field (~3 kV/cm) was observed in UHMWPE/GO nanocomposite of 1 wt% GO, which showed a strong hysteresis loop of polarization versus electric field plot as compared to pure UHMWPE, which displayed a very weak hysteresis loop. The piezoelectric coefficient (d33) of ~9.5 pm/V was estimated in UHMWPE/GO nanocomposite of 1 wt% GO via piezoresponse force microscopy. Nanocomposite sensor devices were also fabricated and piezoelectric output voltage of ~6 V was recorded in UHMWPE/GO nanocomposite of 1 wt% of GO. We report here for the first time the unique ferroelectric and piezoelectric properties displayed by UHMWPE/GO nanocomposites.  相似文献   
76.
Polyaniline (PANI) is a well‐studied material and is the pre‐eminent electrically conducting organic polymer with the potential for a variety of applications such as in batteries, microelectronics displays, antistatic coatings, electromagnetic shielding materials, sensors and actuators. Its good environmental as well as thermal stability and electrical conductivity tunable by appropriate doping make PANI an ideal active material for several applications. In this paper, we report the synthesis of water‐dispersible colloidal PANI/iron oxide composite nanoparticles using an in situ chemical oxidation polymerization method in a micellar medium of sodium dodecylsulfate, where the cores (iron oxide) are embedded in a PANI matrix layer. Transmission electron micrographs showed evidence of the formation of an iron oxide core/PANI shell composite with a thin layer of PANI over the iron oxide cores. The results of thermogravimetric, Fourier transform infrared and UV‐visible analysis indicated that the iron oxide nanoparticles could improve the composite thermal stability possibly due to the interaction between iron oxide particles and PANI backbone. We believe that the synthetic route described can also be adapted for the assembly of hierarchical structures of other metal oxides or hydroxides onto various cores. Copyright © 2010 Society of Chemical Industry  相似文献   
77.
There has been a quick development in construction activities during the last couple of decades attributable to a general improvement in all features of humankind. Because of innovative progressions and regularly expanding human progress, there is a diligent requirement of power. Close by the ordinary energy sources, renewable energy sources have likewise lead significantly to the rising power requirement. All over the world in the past, a number of small hydropower plants (SHPPs) have been developed, as a renewable energy source. Generally, these SHPPs are being manufactured and worked by the private designers consenting to the administration rules. So as to help a designer in choosing the most productive and doable SHPP for development and consequent activity, the concept of the intuitionistic cubic fuzzy set (ICFS) theory is established and a few important operations for ICFSs are characterized, and also a strategy dependent on intuitionistic cubic fuzzy Hamacher hybrid averaging (ICFHHA) operator, intuitionistic cubic fuzzy Hamacher order weighted averaging (ICFHOWA) operator, and intuitionistic cubic fuzzy Hamacher weighted averaging (ICFHWA) operators is utilized in the present paper. The financial criteria and technobusiness, as assumed for examining the practicality of the candidate SHPPs, are presented qualitatively utilizing intuitionistic cubic fuzzy numbers (ICFNs). Further study their fundamental properties and the relationship among these aggregation operators. Developed group decision-making (DM) algorithm under intuitionistic cubic fuzzy (ICF) environment. An interpretative case for the analysis of SHPP for construction is given to demonstrate the feasibility and practicality of the mentioned new techniques. Further validate its effectiveness and benefits via a comparative analysis with pre-existing aggregation operators, and the outcomes demonstrate that the proposed SHPP determination model has some special favorable circumstances, which is progressively practical and adaptable for SHPP choice under a complex and uncertain environment.  相似文献   
78.

In recent years, Botnets have been adopted as a popular method to carry and spread many malicious codes on the Internet. These malicious codes pave the way to execute many fraudulent activities including spam mail, distributed denial-of-service attacks and click fraud. While many Botnets are set up using centralized communication architecture, the peer-to-peer (P2P) Botnets can adopt a decentralized architecture using an overlay network for exchanging command and control data making their detection even more difficult. This work presents a method of P2P Bot detection based on an adaptive multilayer feed-forward neural network in cooperation with decision trees. A classification and regression tree is applied as a feature selection technique to select relevant features. With these features, a multilayer feed-forward neural network training model is created using a resilient back-propagation learning algorithm. A comparison of feature set selection based on the decision tree, principal component analysis and the ReliefF algorithm indicated that the neural network model with features selection based on decision tree has a better identification accuracy along with lower rates of false positives. The usefulness of the proposed approach is demonstrated by conducting experiments on real network traffic datasets. In these experiments, an average detection rate of 99.08 % with false positive rate of 0.75 % was observed.

  相似文献   
79.
Phishing is an instance of social engineering techniques used to deceive users into giving their sensitive information using an illegitimate website that looks and feels exactly like the target organization website. Most phishing detection approaches utilizes Uniform Resource Locator (URL) blacklists or phishing website features combined with machine learning techniques to combat phishing. Despite the existing approaches that utilize URL blacklists, they cannot generalize well with new phishing attacks due to human weakness in verifying blacklists, while the existing feature-based methods suffer high false positive rates and insufficient phishing features. As a result, this leads to an inadequacy in the online transactions. To solve this problem robustly, the proposed study introduces new inputs (Legitimate site rules, User-behavior profile, PhishTank, User-specific sites, Pop-Ups from emails) which were not considered previously in a single protection platform. The idea is to utilize a Neuro-Fuzzy Scheme with 5 inputs to detect phishing sites with high accuracy in real-time. In this study, 2-Fold cross-validation is applied for training and testing the proposed model. A total of 288 features with 5 inputs were used and has so far achieved the best performance as compared to all previously reported results in the field.  相似文献   
80.
There are a multitude of applications using modern tablet computers for vision testing that are accessible to ophthalmology patients. While these may be of potential future benefit, they are often unsupported by scientific assessment. This report investigates the pertinent physical characteristics behind one of the most common highest specification tablet computers with regard to its capacity for vision testing. We demonstrate through plotting of a gamma curve that it is feasible to produce a precise programmable range of central luminance levels on the device, even with varying background luminance levels. It may not be possible to display very low levels of contrast, but carefully using the gamma curve information allows a reasonable range of contrast sensitivity to be tested. When the screen is first powered on, it may require up to 15 min for the luminance values to stabilize. Finally, luminance of objects varies towards the edge of the screen and when viewed at an angle. However, the resulting effective contrast of objects is less variable. Details of our assessments are important to developers, users and prescribers of tablet clinical vision tests. Without awareness of such findings, these tests may never reach satisfactory levels of clinical validity and reliability.  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