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   657篇
  免费   13篇
  国内免费   4篇
化学   455篇
晶体学   18篇
力学   2篇
数学   35篇
物理学   164篇
  2022年   3篇
  2021年   5篇
  2020年   3篇
  2019年   6篇
  2018年   3篇
  2016年   11篇
  2015年   14篇
  2014年   12篇
  2013年   25篇
  2012年   24篇
  2011年   29篇
  2010年   13篇
  2009年   17篇
  2008年   20篇
  2007年   37篇
  2006年   38篇
  2005年   40篇
  2004年   34篇
  2003年   33篇
  2002年   34篇
  2001年   12篇
  2000年   5篇
  1999年   11篇
  1998年   4篇
  1997年   16篇
  1996年   6篇
  1995年   10篇
  1994年   4篇
  1993年   8篇
  1992年   5篇
  1991年   8篇
  1990年   6篇
  1989年   3篇
  1988年   7篇
  1987年   7篇
  1986年   10篇
  1985年   10篇
  1984年   9篇
  1983年   9篇
  1982年   11篇
  1981年   6篇
  1980年   10篇
  1979年   11篇
  1978年   15篇
  1977年   13篇
  1976年   11篇
  1975年   9篇
  1974年   7篇
  1973年   11篇
  1936年   3篇
排序方式: 共有674条查询结果,搜索用时 15 毫秒
71.
72.
Experimental infrared modulator elements have been fabricated utilizing the transient light scattering effect of ferroelectric liquid crystal with asymmetric waveform voltage drive. The new elements perform 80% modulation degrees at the 632.8nm. We have also achieved 30% modulation degrees in the 4 to 5µ m region where the strongest CO2 absorption bands exist. A new type of analyzer which monitors ambient air quality has been developed. This analyzer uses non-dispersive infrared absorption method and composes of a double-beam, a single detector and a pair of liquid crystal light modulator as the IR chopper. The detection has achieved 10ppm noise equivalent concentration.  相似文献   
73.
In scanning microscopy by total internal reflection with thermal lens spectroscopy, its spatial resolution depends on the distance between the sample and a converging lens, which corresponds to the objective lens in an ordinary optical microscope. It was found that the resolution was best when the signal induced by the thermal lens effect was maximum. The distance was precisely adjusted by monitoring the signal intensity, and the resolution became twice better than that previously reported. Using a shorter focal-length lens, a resolution of 1.9 microm was attained.  相似文献   
74.
Sun H  He F  Zhou Z  Cheng Y  Xu Z  Sugioka K  Midorikawa K 《Optics letters》2007,32(11):1536-1538
We describe the fabrication of microfluidic channel structures on the surface of a borosilicate glass slide by femtosecond laser direct writing for optical waveguide application. Liquid with a variable refractive index is fed into the microchannel, serving as the core of the waveguide. We demonstrate that either a multimode or a single-mode waveguide can be achieved by controlling the refractive index of the liquid.  相似文献   
75.
Lysocin E, a macrocyclic peptide, exhibits potent antibacterial activity against methicillin‐resistant Staphylococcus aureus (MRSA) through a novel mechanism. The first total synthesis of lysocin E was achieved by applying a full solid‐phase strategy. The developed approach also provides rapid access to the enantiomeric, epimeric, and N‐demethylated analogues of lysocin E. Significantly, the antibacterial activity of the unnatural enantiomer was comparable to that of the natural isomer, suggesting the absence of chiral recognition in its mode of action.  相似文献   
76.
77.
An outstanding compression function for materials preparation exhibited by nanospaces of single-walled carbon nanohorns (SWCNHs) was studied using the B1-to-B2 solid phase transition of KI crystals at 1.9 GPa. High-resolution transmission electron microscopy and synchrotron X-ray diffraction examinations provided evidence that KI nanocrystals doped in the nanotube spaces of SWCNHs at pressures below 0.1 MPa had the super-high-pressure B2 phase structure, which is induced at pressures above 1.9 GPa in bulk KI crystals. This finding of the supercompression function of the carbon nanotubular spaces can lead to the development of a new compression-free route to precious materials whose syntheses require the application of high pressure.  相似文献   
78.
In this study, we examined the reaction hazard during the hydrosilylation reaction between trichlorosilane (TCS) and 1,6-divinyl(perfluorohexane) (FDV) in the presence of a butanol solution of chloroplatinic acid (Pt-Cat) as the catalyst. Assuming the three industrial risks of excessive addition of Pt-Cat, contamination by iron rust and mixing with cooling water, we observed the temperature and pressure change of TCS/FDV with an excessive amount of Pt-Cat, TCS/FDV/Pt-Cat with Fe2O3 and TCS/FDV/Pt-Cat with distilled water, using an accelerating rate calorimeter (ARC). The temperature and pressure greatly increased, especially in the sample with Fe2O3. For instance, in TCS/FDV/Pt-Cat with 1.5 wt.% Fe2O3, the heat release rate exceeded 624 K · min?1 and the pressure rose above 25 MPa during the exothermic reaction.  相似文献   
79.
A modified method for the quantitative determination of bepridil hydrochloride in human plasma is described. This method is unrelated to chemical methods currently in use. The mobile phase is 50 mM phosphate buffer (pH3.0)-methanol-acetonitrile-triethylamine (57:3:40:1, v/v), and the samples are fractionated on a C8-3 column (150 × 4.6 mm, 5 μm) using a flow rate of 0.9 mL/min. Bepridil was detected by UV spectroscopy at 254 nm. The retention times of bepridil and 1-naphthol were 12.6 min and 7.5 min, respectively; there was no interference originating from human plasma. We confirmed that the bepridil and 1-naphthol peaks were not influenced by the presence of 32 commercial medicines frequently co-administered with bepridil. Additionally, the concentration of bepridil in the plasma of five patients treated with bepridil for atrial fibrillation was measured. These samples were collected just before each dosage of bepridil. Their rhythm and rate control were well maintained. Trough concentrations ranged from 233.9 to 347.4 ng/mL, similar to previously reported values.  相似文献   
80.
Annals of Operations Research - Answer Set Programming (ASP) is an approach to declarative problem solving, combining a rich yet simple modeling language with high performance solving capacities....  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