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   831篇
  免费   17篇
  国内免费   4篇
化学   362篇
晶体学   9篇
力学   66篇
数学   201篇
物理学   214篇
  2022年   3篇
  2021年   25篇
  2020年   6篇
  2019年   4篇
  2018年   1篇
  2017年   7篇
  2016年   15篇
  2015年   19篇
  2014年   28篇
  2013年   34篇
  2012年   43篇
  2011年   33篇
  2010年   39篇
  2009年   37篇
  2008年   54篇
  2007年   64篇
  2006年   76篇
  2005年   41篇
  2004年   29篇
  2003年   33篇
  2002年   40篇
  2001年   19篇
  2000年   14篇
  1999年   13篇
  1998年   14篇
  1997年   15篇
  1996年   7篇
  1995年   6篇
  1994年   15篇
  1993年   2篇
  1992年   9篇
  1991年   4篇
  1990年   6篇
  1989年   3篇
  1988年   3篇
  1986年   2篇
  1985年   11篇
  1984年   9篇
  1983年   4篇
  1982年   10篇
  1981年   10篇
  1980年   6篇
  1979年   7篇
  1978年   8篇
  1977年   4篇
  1976年   5篇
  1975年   3篇
  1974年   3篇
  1973年   6篇
  1972年   3篇
排序方式: 共有852条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
L. Q. Anh  A. Y. Kruger  N. H. Thao 《TOP》2014,22(1):331-342
We consider parametric equilibrium problems in metric spaces. Sufficient conditions for the Hölder calmness of solutions are established. We also study the Hölder well-posedness for equilibrium problems in metric spaces.  相似文献   
5.
图论、最优化理论显然在蛋白质结构的研究中大有用场. 首先, 调查/回顾了研究蛋白质结构的所有图论模型. 其后, 建立了一个图论模型: 让蛋白质的侧链来作为图的顶点, 应用图论的诸如团、 $k$-团、 社群、 枢纽、聚类等概念来建立图的边. 然后, 应用数学最优化的现代摩登数据挖掘算法/方法来分析水牛普里昂蛋白结构的大数据. 成功与令人耳目一新的数值结果将展示给朋友们.  相似文献   
6.
Flexible dye‐sensitized solar cells (DSSCs) built on plastic substrates have attracted great interest as they are lightweight and can be roll‐to‐roll printed to accelerate production and reduce cost. However, plastic substrates such as PEN and PET are permeable to water, oxygen and volatile electrolyte solvents, which is detrimental to the cell stability. Therefore, to address this problem, in this work, an ionic liquid (IL) electrolyte is used to replace the volatile solvent electrolyte. The initial IL‐based devices only achieved around 50% of the photovoltaic conversion efficiency of the cells using the solvent electrolyte. Current‐voltage and electrochemical impedance spectroscopy (EIS) analysis of the cells in the dark indicated that this lower efficiency mainly originated from (i) a lack of blocking layer to reduce recombination, and (ii) a lower charge collection efficiency. To combat these problems, cells were developed using a 12 nm thick blocking layer, produced by atomic layer deposition, and 1 μm thick P25 TiO2 film sensitized with the hydrophobic MK‐2 dye. These flexible DSSCs utilizing an IL electrolyte exhibit significantly improved efficiencies and a <10% drop in performance after 1000 h aging at 60°C under continuous light illumination.  相似文献   
7.
Monitoring ambient solar UVR levels provides information on how much there is in both real time and historically. Quality assurance of ambient measurements of solar UVR is critical to ensuring accuracy and stability and this can be achieved by regular intercomparisons of spectral measurement systems with those of other organizations. In October and November of 2013 a solar UVR spectroradiometer from Public Health England (PHE) was brought to Melbourne for a campaign of intercomparisons with a new Bentham spectrometer of Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) and one at the Australian Bureau of Meteorology (BOM), supported by New Zealand's National Institute for Water and Atmosphere (NIWA). Given all three spectroradiometers have calibrations that are traceable to various national standards, the intercomparison provides a chance to determine measurement uncertainties and traceability that support UV measurement networks in Australia, New Zealand and the UK. UV Index measurements from all three systems were compared and ratios determined for clear sky conditions when the scans from each instrument were within 2 min of each other. While wavelengths below 305 nm showed substantial differences between the PHE unit and the two other systems, overall the intercomparison results were encouraging, with mean differences in measured UV Index between the BOM/NIWA and those of PHE and ARPANSA of <0.1% and 7.5%, respectively.  相似文献   
8.
Impact loading is an important process in the transport industry as it causes wear and failure of critical components. Conveyor belts are of particular importance as they are used in practically every industry where large quantities of goods are moved over short (<10 m) or long distances (>1 km). To investigate stress levels inside the material during impact loading, a gas gun was utilized to shoot 9 mm spherical steel balls onto the surface of a rubber conveyor belt. A high speed video recording system was employed in order to determine penetration depth and dissipated energy of the steel ball. Maximal penetration depths of up to 3.9 mm and maximal dissipated energies of up to 86.8 % were measured. Additionally, a numerical simulation using smooth particle applied mechanics was conducted and compared to the experimental results obtained with the gas gun. The calculated von Mises stresses affected the conveyor belts up to a maximum depth of 8.8 mm with at least 20 MPa. Maximum von Mises stresses were calculated to reach 60 MPa.  相似文献   
9.
Using the formulation of Hopke and Slattery, upper and lower bounds on the drag coefficient of a sphere moving slowly in Ellis model fluids have been calculated, over wide range of conditions, and compared with the suitable experimental data available in the literature. C D drag coefficient - d diameter of sphere - El Ellis number - Re Reynolds number based on zero-shear viscosity - V terminal falling velocity of a sphere - X drag correction factor - Ellis model parameter - 0 zero-shear viscosity - 1/2 Ellis model parameter  相似文献   
10.
This paper focuses on the parameterisation, validation and implementation of an FTire model of a Michelin LTX A/T2 235/85R16 tyre. This tyre is designed for both on- and off-road use and is commonly used on all wheel drive SUVs. Quasi-static laboratory and dynamic field tests were conducted to acquire parameterisation and validation test data for the FTire model. Quasi-static parameterisation tests include acquiring vertical tyre stiffness over a flat plate and cleats, tyre footprint sizes and shapes, longitudinal, lateral and torsional tyre stiffness for various tyre normal loads, as well as vibrational tyre responses. Dynamic parameterisation tests include dynamic cleat test data. An Adams model of the tyre testing equipment is implemented to simulate the FTire model and validate it against dynamic validation test results. Finally, the model is implemented on a fully nonlinear multi-body dynamics model of a Land Rover Defender. It is found that the FTire model is able to predict the lateral tyre behaviour well on a smooth road surface. The vertical and longitudinal tyre behaviour on a smooth road surface and on a rough surface are predicted accurately.  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