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   857篇
  免费   49篇
  国内免费   1篇
电工技术   7篇
化学工业   240篇
金属工艺   15篇
机械仪表   20篇
建筑科学   12篇
能源动力   67篇
轻工业   55篇
水利工程   11篇
石油天然气   2篇
无线电   84篇
一般工业技术   192篇
冶金工业   42篇
原子能技术   10篇
自动化技术   150篇
  2024年   4篇
  2023年   13篇
  2022年   30篇
  2021年   49篇
  2020年   38篇
  2019年   42篇
  2018年   41篇
  2017年   37篇
  2016年   34篇
  2015年   27篇
  2014年   46篇
  2013年   70篇
  2012年   56篇
  2011年   59篇
  2010年   48篇
  2009年   38篇
  2008年   47篇
  2007年   42篇
  2006年   24篇
  2005年   16篇
  2004年   15篇
  2003年   12篇
  2002年   9篇
  2001年   10篇
  2000年   11篇
  1999年   3篇
  1998年   13篇
  1997年   10篇
  1996年   5篇
  1995年   4篇
  1994年   7篇
  1993年   7篇
  1992年   1篇
  1991年   3篇
  1990年   2篇
  1989年   4篇
  1988年   5篇
  1986年   1篇
  1985年   2篇
  1984年   2篇
  1983年   3篇
  1982年   5篇
  1981年   7篇
  1980年   2篇
  1978年   1篇
  1975年   1篇
  1967年   1篇
排序方式: 共有907条查询结果,搜索用时 15 毫秒
1.
Wireless Networks - In Wireless Sensor Networks (WSNs), where power consumption is a huge concern, the improvement of the network’s lifetime is an area of constant study and innovation. The...  相似文献   
2.
ZnO rice like nonarchitects are grafted on the graphene carbon core via a rapid microwave synthesis route. The prepared grafted systems are characterized via XRD, SEM, RAMAN, and XPS to examined the structural and morphological parameters. Zinc oxide grafted graphene sheets (ZnO-G) are further doped in β-phase of polyvinylidene fluoride (PVDF) to prepare the polymer nanocomposites (PNCs) via mixed solvent approach (THF/DMF). β-phase confirmation of PVDF PNCs is done by FTIR studies. It is observed that ZnO-G filler enhances the β-phase content in the PNCs. Non-doped PVDF and PNCs are further studied for rheological behavior under the shear rate of 1–100 s−1. Doping of ZnO-G dopant to the PVDF matrix changes its discontinuous shear thickening (DST) behavior to continues shear thickening behavior (CST). Hydrocluster formation and their interaction with the dopant could be the reason for this striking DST to CST behavioral change. Strain amplitude sweep (10−3% -10%) oscillatory test reveals that the PNCs shows extended linear viscoelastic region with high elastic modulus and lower viscous modulus. Effective shear thickening behavior and strong elastic strength of these PNCs present their candidature for various fields including mechanical and soft body armor applications.  相似文献   
3.
Vaccination against tick-borne encephalitis with FSME-Immun vaccine was started in the Department of Infectious Diseases, University Medical School of Bia?ystok, Poland, in 1992. No serious adverse reactions after vaccine administration were observed. Post-vaccine side effects were reported in 242 (11.3%) persons after the first dose (n = 2,135) and only in 14 patients (1.2%) after the second one (n = 1,183). These effects were mild and transitory. No relationship was observed between the frequency of adverse reactions, general or local, and the initial anti-TBE virus antibody titres or the age of the immunized individuals. Post-vaccine side effects were reported significantly more frequently among people not bitten by ticks.  相似文献   
4.
We model the rolling motion of a fluid-driven, particle-filled microcapsule along a heterogeneous, adhesive substrate to determine how the release of the encapsulated nanoparticles can be harnessed to repair damage on the underlying surface. We integrate the lattice Boltzmann model for hydrodynamics and the lattice spring model for the micromechanics of elastic solids to capture the interactions between the elastic shell of the microcapsule and the surrounding fluids. A Brownian dynamics model is used to simulate the release of nanoparticles from the capsule and their diffusion into the surrounding solution. We focus on a substrate that contains a damaged region (e.g. a crack or eroded surface coating), which prevents the otherwise mobile capsule from rolling along the surface. We isolate conditions where nanoparticles released from the arrested capsule can repair the damage and thereby enable the capsules to again move along the substrate. Through these studies, we establish guidelines for designing particle-filled microcapsules that perform a 'repair and go' function and thus, can be utilized to repair damage in microchannels and microfluidic devices.  相似文献   
5.
Poly(vinylbenzyltrimethylammonium chloride)‐graft‐cotton cellulose, an anion‐exchange matrix, was synthesized by a mutual radiation‐induced grafting technique with a 60Co γ‐radiation source. The grafted matrix was characterized by grafting yield estimation, elemental analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The grafting yield decreased with the increase in the dose rate. However, the grafting yield and nitrogen content of grafted samples increased almost linearly with an increase in the total irradiation dose. To evaluate the performance of the grafted anion‐exchange matrix, the protein adsorption and elution behavior were investigated in a continuous column process under various experimental conditions, with bovine serum albumin used as a model protein. The binding and elution behavior of the anion‐exchange matrix depended on different experimental parameters, such as the grafting yield, ionic strength, pH of the medium, and amount of protein loaded. From a breakthrough curve, the equilibrium binding capacity and elution percentage of the grafted anion‐exchange matrix were estimated to be 40 mg/g and 94%, respectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5512–5521, 2006  相似文献   
6.
7.
Lakes play a vital role in regulating water storage, flow of river water, and ultimately maintaining a balanced ecosystem. Spatial and temporal variations in physicochemical parameters of water in Harike Wetland, a Ramsar site in the northwestern state of Punjab, India, were studied. This study was conducted on a monthly basis from January to December 2015. The water quality was studied at ten locations from sites 1 to 10 upstream, central and downstream from Harike Lake for ten physicochemical parameters, including temperature, pH, electrical conductivity, turbidity, dissolved oxygen concentration biological oxygen demand, nitrate and phosphate concentrations and salinity. The findings of this study revealed that, except for temperature and pH, all parameters exhibited relatively higher values for the Sutlej River, compared with the Beas River, with sampling sites 5 to site 7 exhibiting intermediate results. The mean seasonal temperature variations ranged from 16.9 to 26.6 °C, the pH from 7.7 to 8.2, electrical conductivity from 223 to 303 μS cm?1 and TDS concentration from 148.7 to 180.4 ppm. Correlation analysis was conducted to assess the relations between the variables. The electrical conductivity exhibited a high positive correlation with salinity and biological oxygen demand, whereas it correlated negatively with the dissolved oxygen concentration. Box and whisker plots were also plotted for the study results to better examine the data distribution.  相似文献   
8.
The Harike Wetland situated in Punjab is a Ramsar site and a wetland of national importance. The present study was undertaken to assess the spatiotemporal dynamics of the wetland on the basis of geospatial technology and ground‐based studies. Landsat images for the years 2002 and 2014 were acquired from the United States Geological Survey and classified digitally to generate landuse/land cover maps involving four classes (water, grassland (including water hyacinth), agriculture, built‐up (settlement), barren land). The total area of the Harike Wetland was found to be 8023.68 ha. Water sampling at eleven sites was carried out and evaluated for physicochemical parameters. The water quality at several sampling points was found to be severely degraded. Change detection analysis revealed the submerged area (area under water) and grassland (including water hyacinth) had decreased over the past 12 years, whereas that area under agriculture and built‐up land has increased, indicating a shrinkage in the total wetland area. The present study also indicated that the near‐infrared band is a good indicator of water quality parameters, as indicated by the significant positive correlation between the near‐infrared band and relevant water parameters. Because the wetland is important from both an ecological perspective and economic perspective, regular monitoring is recommended, for which geospatial technology has proven to be very useful.  相似文献   
9.
A thio sol–gel process for the synthesis of titanium disulfide using titanium alkoxide as the metal source is demonstrated. The alkoxide reacts at room temperature with H2S to form a precipitate which is a precursor to the sulfide. Through infrared spectroscopy and chemical analysis of the powder and gas chromatographic analysis of the liquid byproducts of the reaction, it is shown that a partially sulfidized alkoxide precursor forms through the displacement of alkoxy groups from the alkoxide by sulfur-bearing thiol groups. This thiolysis reaction is very similar to that which occurs in the case of sol–gel reactions to form oxides. The alkoxy–thiol species then undergo condensation–polymerization by the liberation of H2S. When it is heat-treated in H2S, this precursor transforms to TiS2 at ∼700°C. Systematic heat treatments have been performed and the formation of TiS2 has been observed using X-ray diffractometry. The change in the morphology has also been studied using scanning electron microscopy.  相似文献   
10.
We present a critical review on the use of STM as anin situ technique to characterize electrochemical systems based on the work performed in our laboratory. Contributions ofin situ STM studies include: (i) atomic resolution of electrodeposited lead on graphite; (ii) imaging of modifications on metallic electrode surfaces induced by electrochemical oxidation-reduction processes; (iii) imaging of corrosion process on aluminium and Al-Ta alloy electrodes in NaCl solution; (iv) characterization of semiconductor-solution interfaces. These studies allowed: (a) establishment of STM as a technique which, for some systems, yields atomic resolution of metallic surfaces in air and in solution; (b) establishment of a mechanism for the electrochemical growth of oxide films on metal electrodes; (c) establishment of a corresponding mechanism for the reduction of those electrochemically grown oxide films; (d) direct monitoring of corrosion processes on a scale of nm to m; and (e) determination of the presence of surface states and their energy position at the semiconductor-solution interfaces.This paper is dedicated to Professor Brian E. Conway on the occasion of his 65th birthday and in recognition of his outstanding contribution to electrochemistry.  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