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   5091篇
  免费   179篇
  国内免费   29篇
电工技术   76篇
综合类   8篇
化学工业   986篇
金属工艺   156篇
机械仪表   121篇
建筑科学   55篇
矿业工程   16篇
能源动力   313篇
轻工业   232篇
水利工程   36篇
石油天然气   20篇
无线电   663篇
一般工业技术   1164篇
冶金工业   725篇
原子能技术   34篇
自动化技术   694篇
  2023年   73篇
  2022年   106篇
  2021年   179篇
  2020年   150篇
  2019年   131篇
  2018年   176篇
  2017年   161篇
  2016年   189篇
  2015年   110篇
  2014年   194篇
  2013年   420篇
  2012年   225篇
  2011年   240篇
  2010年   204篇
  2009年   273篇
  2008年   183篇
  2007年   131篇
  2006年   130篇
  2005年   114篇
  2004年   99篇
  2003年   109篇
  2002年   89篇
  2001年   69篇
  2000年   67篇
  1999年   72篇
  1998年   146篇
  1997年   110篇
  1996年   121篇
  1995年   86篇
  1994年   84篇
  1993年   82篇
  1992年   61篇
  1991年   71篇
  1990年   69篇
  1989年   47篇
  1988年   46篇
  1987年   46篇
  1986年   43篇
  1985年   47篇
  1984年   31篇
  1983年   25篇
  1982年   26篇
  1981年   35篇
  1980年   20篇
  1979年   30篇
  1978年   30篇
  1977年   27篇
  1976年   33篇
  1975年   15篇
  1973年   13篇
排序方式: 共有5299条查询结果,搜索用时 15 毫秒
991.
The use of textile-grade fiber extracted from the Indian pineapple leaf is an unexplored area. Pineapple leaf fiber (PALF) is fine, soft, and moderately strong and is much acceptable for fashion garment. An attempt has been made to extract and soften Indian PALF from the pineapple leaves by decortication and subsequent water retting. Decorticated cum retted fiber has shown better physicomechanical and surface appearance properties than decorticated fiber. Fine yarn (38 tex) was spun in a suitable spinning system, and the property performance was found to be suitable to make eco-sustainable novelty fabric. Fabric was developed by using cotton as warp yarn and PALF-based yarn as weft in a handloom. The developed fabric shows very good physical and mechanical properties, desired for apparels. This inferred that Indian PALF may be successfully used to make eco-niche apparel quality fabric as well as novelty textiles.  相似文献   
992.
An in situ hydrogen generation and storage technique is demonstrated during the electrodeposition of hexagonal closed pack (HCP) nickel from NiCl2-1-ethyl-3-methylimidazolium chloride (NiCl2-EmimCl) and NiCl2·6H2O-1-ethyl-3-methylimidazolium chloride (NiCl2·6H2O-EmimCl) melts. During electrolysis, the dissolution of hydrogen in nickel takes place due to the electrolysis of water. This results in the production of HCP nickel. The hydrogen content of the electrodeposited nickel from NiCl2-EmimCl was found to be 1.2 wt.%. Thermal analysis showed that the phase transformation from HCP nickel to FCC occurred at 462 °C, releasing hydrogen in the process.  相似文献   
993.
The nano size zinc oxide (ZnO) was successfully synthesized at low temperature solution method. The structural characterization, size and distribution of synthesized ZnO particles were performed using X-ray diffraction (XRD) and neutron scattering technique. The hybrid polymer-metal oxide bulk heterojunction solar cell has been fabricated by blending of ZnO and regioregular poly(3-hexylthiophene) (P3HT) through solution process and flow coating on the flexible substrate. The decrease in the photoluminescence (PL) emission intensity more than 79% for ZnO:P3HT composites film indicates high charge generation efficiency. The cell shows the Voc and Isc of 0.33 V and 6.5 mA/cm2, respectively. The performance and stability of cell were investigated using UV illumination of white light.  相似文献   
994.
995.
This paper uses a Lagrangian formulation namely smoothed particle hydrodynamics (SPH) technique for the prediction of conduction heat transfer in irregular geometries. Suitable schemes for the placement of particles inside irregular computational domain have been described. Organization and locations for virtual particles are also discussed for both Dirichlet and Neumann boundary conditions. Three different problems having typical geometries that pose numerical complications in grid based technique, are tackled by SPH efficiently. Conduction shape factor (CSF) for all the problems calculated through SPH shows a good agreement with published results or analytical solutions. Further, the temperature profiles computed by SPH depict close matches with those obtained through numerical software Fluent. The present exercise opens up the possibility of using SPH in varied geometries using different schemes of particle positioning and their judicial combinations.  相似文献   
996.
This paper has analyzed the case of Moushuni Island at Sundarban of 24 Parganas South of West Bengal, India. The proposition is to find out the possibility of grid-connectivity of Isolated Remote Island which is under rural electrification scheme by hybrid renewable energies under Jawaharlal Nehru National Solar Mission of India. In these rural electrification program, grid extension can be the best option if the grid is reliable, the rural community rather big and in proximity to the grid. In many circumstances, a strong case for mini-grids based on hybrid systems can be made. Scattered communities and isolated houses are well served by solar and small hydro (where available) or small wind energy systems. By feeding renewable electricity to the utility grid through the grid-connected hybrid renewable energy system, during time of peak demand, sufficient electrical loads can be shed to prevent turning on a coal or natural gas-fired plant and therefore save CO2 emissions and potentially energy import costs, replacing fossil fuels. The Social, Economic, and Environmental Benefits can be achieved through this proposition. Also, the Grid Interactive Operation of SPV System at Moushuni Island is tested. Malda district of West Bengal, India is a vision towards smart-grid city towards sustainable future, where rural consumers can upgrade their quality of life through solar energy resource.  相似文献   
997.
The standard potentials (E°) of the silver/silver-iodide electrode in aqueous mixtures of ethylene glycol (containing 10, 30, 50, 70 and 90 wt-% glycol) have been determined from emf measurements of the cell Pt, H2(g, 1 atm)/HOAc(m1), NaOAc(m2), Kl(m3), solvent/AgI/Ag at nine temperatures ranging from 5 to 45°C. These E° values have been utilized to compute free energy (Δtt°), entropy (ΔSt°) and enthalpy (ΔHt°) changes accompanying the transfer of HI from water to each of the solvents. These values as well as those for HCl and HBr and obtained earlier have also been utilized to evaluate ΔSt°(i) for individual ions by a method of ‘simultaneous extrapolation,’ which in turn furnished the values of ΔHt°(i) for these ions. These quantities and also the ‘chemical’ contributions for the halide ions as obtained by subtracting the ‘electrostatic’ contribution computed with the Born equation, have been examined in the light of ion—solvent interactions as well as the structural changes of the solvents. The observed results conform with what is expected from the competitive effects of the preferential solvating capacities of water towards halide ions and that of other solvents towards hydrogen ions, and also of the effects arising from the structural changes of the solvents that are likely to occur in the over-all transfer process.  相似文献   
998.
999.
This study describes the capacitor behavior of carbon nanohorn (CNH)/graphene nanoplate (GNP) hybrid (CNGN). The well‐CNH‐decorated GNP‐plate electrode materials show high capacitance value (≈677 F/g) and can be extensively used in new generation for energy storage. In the hybrid (CNGN), two nanofillers jointly affect the capacitance behavior and increase the capacitance value of the CNGN hybrid. Homogeneous coating of CNH over the GNP plate plays an effective role to enhance the capacitance behavior of the composite. Field emission scanning electron microscopy and high‐resolution transmission electron microscopy analysis of the composite confirmed the CNH coating on the GNP plate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42118.  相似文献   
1000.
This work investigates the effect of thermophoresis and chemical reaction on heat and mass transfer in hydromagnetic micropolar fluid flow over an inclined permeable plate with constant heat flux and non-uniform heat source/sink in the presence of thermal radiation. It is assumed that the transverse magnetic field is a function of the distance from the origin. The analysis accounts for both temperature dependent fluid viscosity and thermal conductivity. Using the similarity transformation, the governing system of equations are transformed into non-linear ordinary differential equations and are solved numerically using symbolic software MATHEMATICA. Numerical results for the velocity, microrotation, temperature and species concentration as well as for the skin friction, heat and mass transfer are obtained and displayed graphically for pertinent parameters to show interesting aspects of the solution.  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