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   1248篇
  免费   60篇
  国内免费   4篇
化学   908篇
晶体学   7篇
力学   27篇
数学   76篇
物理学   294篇
  2023年   11篇
  2022年   5篇
  2021年   19篇
  2020年   17篇
  2019年   17篇
  2018年   13篇
  2017年   9篇
  2016年   34篇
  2015年   29篇
  2014年   38篇
  2013年   63篇
  2012年   84篇
  2011年   101篇
  2010年   63篇
  2009年   57篇
  2008年   78篇
  2007年   80篇
  2006年   84篇
  2005年   66篇
  2004年   55篇
  2003年   50篇
  2002年   42篇
  2001年   23篇
  2000年   27篇
  1999年   18篇
  1998年   11篇
  1997年   9篇
  1996年   21篇
  1995年   8篇
  1994年   16篇
  1993年   14篇
  1992年   17篇
  1991年   10篇
  1990年   8篇
  1989年   10篇
  1987年   5篇
  1986年   9篇
  1985年   15篇
  1984年   7篇
  1983年   7篇
  1982年   10篇
  1981年   8篇
  1980年   7篇
  1979年   2篇
  1978年   3篇
  1977年   8篇
  1976年   8篇
  1975年   5篇
  1974年   2篇
  1973年   4篇
排序方式: 共有1312条查询结果,搜索用时 15 毫秒
61.
We reported the characteristics of p‐type tin‐oxide (SnO) thin film transistors (TFTs) upon illumination with visible light. Our p‐type TFT device using the SnO film as the active channel layer exhibits high sensitivity toward the blue‐light with a high light/dark read current ratio (Ilight/Idark) of 8.2 × 103 at a very low driven voltage of <3 V. Since sensing of blue‐light radiation is very critical to our eyes, the proposed p‐type SnO TFTs with high sensitivity toward the blue‐light show great potential for future blue‐light detection applications.

  相似文献   

62.
Differential measurements of elliptic flow (v2) for Au+Au and Cu+Cu collisions at sqrt[sNN]=200 GeV are used to test and validate predictions from perfect fluid hydrodynamics for scaling of v2 with eccentricity, system size, and transverse kinetic energy (KE T). For KE T identical with mT-m up to approximately 1 GeV the scaling is compatible with hydrodynamic expansion of a thermalized fluid. For large values of KE T mesons and baryons scale separately. Quark number scaling reveals a universal scaling of v2 for both mesons and baryons over the full KE T range for Au+Au. For Au+Au and Cu+Cu the scaling is more pronounced in terms of KE T, rather than transverse momentum.  相似文献   
63.
During the last 20 years, beamline BL08B has been upgraded step by step from a photon beam‐position monitor (BPM) to a testing beamline and a single‐grating beamline that enables experiments to record X‐ray photo‐emission spectra (XPS) and X‐ray absorption spectra (XAS) for research in solar physics, organic semiconductor materials and spinel oxides, with soft X‐ray photon energies in the range 300–1000 eV. Demands for photon energy to extend to the extreme ultraviolet region for applications in nano‐fabrication and topological thin films are increasing. The basic spherical‐grating monochromator beamline was again upgraded by adding a second grating that delivers photons of energy from 80 to 420 eV. Four end‐stations were designed for experiments with XPS, XAS, interstellar photoprocess systems (IPS) and extreme‐ultraviolet lithography (EUVL) in the scheduled beam time. The data from these experiments show a large count rate in core levels probed and excellent statistics on background normalization in the L‐edge adsorption spectrum.  相似文献   
64.
The rapid development of the petrochemical industry of Taiwan over the past four decades has resulted in a booming economy in Taiwan that drives derived industries to develop progressively. However, it has also caused many runaway reaction accidents, such as toxic gas release, fire, and explosion. It is crucial to eliminate those potential hazard factors which can induce consequent runaway reaction accidents during the life span of the manufacturing process. In response to this crucial issue, we performed a thermokinetic parameter analysis for 1,1-bis-(tert-butylperoxy)-3,3,5-trimethylcyclohexane at isothermal conditions to conduct a thermal safety assessment of chemical materials. The five isothermal temperatures, 90, 100, 110, 120, 130, and 140 °C, measured by DSC, were adopted in this study to calculate process safety parameters, including TMRad, T NR, and SADT, which can be employed in process safety parameters for the manufacturing process. A novel, green kinetic approach accompanied with non-isothermal DSC results is used to derive thermokinetic parameters in safety protocol in this study.  相似文献   
65.
66.
Chemical reduction of a hydroxyphenyl‐substituted borane triggers a sequential electron‐ and intramolecular hydrogen‐atom‐transfer process to afford a hydridoborate phenoxide dianion. On the other hand, hydrogen‐atom abstraction of the borane leads to the isolation of a neutral borylated phenoxyl radical, which can be transformed to the corresponding benzoquinone borataalkene derivative by reduction with cobaltocene.  相似文献   
67.
Journal of Computer-Aided Molecular Design - The Drug Design Data Resource (D3R) aims to identify best practice methods for computer aided drug design through blinded ligand pose prediction and...  相似文献   
68.
The components of OLED encapsulation with hermetic sealing and a 1026-day lifetime were measured by PXI-1033. The optimal characteristics were obtained when the thickness of the TPBi layer was 20 nm. This OLED obtained a maximum luminance (Lmax) of 25,849 cd/m2 at a current density of 1242 mA/cm2, an external quantum efficiency (EQE) of 2.28%, a current efficiency (CE) of 7.20 cd/A, and a power efficiency (PE) of 5.28 lm/W. The efficiency was enhanced by Lmax 17.2%/EQE 0.89%/CE 42.1%/PE 41.9%. The CIE coordinates of 0.32, 0.54 were all green OLED elements with wavelengths of 532 nm. The shear strain and leakage test gave results of 16 kgf and 8.92 × 10−9 mbar/s, respectively. The reliability test showed that the standard of MIL-STD-883 was obtained.  相似文献   
69.
Huang HY  Chiu CW  Huang IY  Yeh JM 《Electrophoresis》2004,25(18-19):3237-3246
Five common food preservatives were analyzed by capillary electrochromatography, utilizing a methacrylate ester-based monolithic capillary as separation column. In order to optimize the separation of these preservatives, the effects of the pore size of the polymeric stationary phase, the pH and composition of the mobile phase on separation were examined. For all analytes, it was found that an increase in pore size caused a reduction in retention time. However, separation performances were greatly improved in monolithic columns with smaller pore sizes. The pH of the mobile phase had little influence on separation resolution, but a dramatic effect on the amount of sample that was needed to be electrokinetically injected into the monolithic column. In addition, the retention behaviors of these analytes were strongly influenced by the level of acetonitrile in the mobile phase. An optimal separation of the five preservatives was obtained within 7.0 min with a pH 3.0 mobile phase composed of phosphate buffer and acetonitrile 35:65 v/v. Finally, preservatives in real commercial products, including cold syrup, lotion, wine, and soy sauces, were successfully determined by the methacrylate ester-based polymeric monolithic column under this optimized condition.  相似文献   
70.
Volatile organic compounds (VOCs) were monitored in the different sections of a wastewater treatment plant (WWTP), the outlet of both the WWTP and rainfall water, and the downstream of the WWTP joining the river in the area or vicinity of an industrial science park located in Hsinchu, Taiwan. Levels of VOCs were determined by collecting air samples over several sampling points and analyzed using gas chromatography. Among VOCs identified in the drainage and effluent system in each season, acetone, isopropanol (IPA) and dimethyl sulfide (DMS) were the major emission species and maximum concentrations were 400.4, 22.8 and 641.2 ppbv, respectively. The ambient air and wastewater sample analysis from neighboring wastewater streams identified pollutants being discharged from unaccounted sources other than the industrial park. According to the 24 h semi-continuous monitoring data (27/7/2002-29/7/2002), the total VOC concentration was an average of 93 ppbv (acetone contributed ∼78%) with a dramatic variation during the day and night. The emission rate of measured VOCs estimated using fixed box model projected an average of 2-4 μg m−2 h−1) during the day and 9-17 μg m−2 h−1 during the night. In addition, the isopleth maps show that the acetone and DMS emissions influence adversely the nearby residential area located at less than 100 m downwind from the plant. Eventually, based on this study, an on-line monitoring and alerting system could be built for a long-term performance, and with regular information on the varying pollutants over time construction of a green strategy and creation of a sustainable environment can be achieved.  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