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   239篇
  免费   15篇
  国内免费   1篇
化学   212篇
晶体学   1篇
力学   3篇
数学   3篇
物理学   36篇
  2023年   3篇
  2021年   1篇
  2020年   4篇
  2019年   4篇
  2018年   4篇
  2017年   3篇
  2016年   10篇
  2015年   7篇
  2014年   8篇
  2013年   11篇
  2012年   12篇
  2011年   14篇
  2010年   12篇
  2009年   15篇
  2008年   13篇
  2007年   10篇
  2006年   15篇
  2005年   13篇
  2004年   11篇
  2003年   10篇
  2002年   3篇
  2001年   10篇
  2000年   2篇
  1999年   3篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1987年   2篇
  1986年   3篇
  1985年   3篇
  1984年   3篇
  1983年   1篇
  1982年   2篇
  1981年   3篇
  1980年   5篇
  1977年   3篇
  1976年   4篇
  1974年   4篇
  1973年   3篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
  1967年   2篇
排序方式: 共有255条查询结果,搜索用时 15 毫秒
41.
The spin density of Heusler alloy Co2FeGa, has been studied using the Compton scattering technique with 274 keV circularly polarized synchrotron radiation in the high energy inelastic scattering beamline (BL08W), at SPring-8, Japan. The magnetic Compton profiles along the two principal directions [1 1 0] and [1 1 1] were measured. The spin profiles shows a good agreement with our FLAPW-GGA results, where the theoretical results were based on the ferromagnetic ground state. The 3d spin moment at the Co and the Fe site was found to be in excellent agreement with the earlier reported neutron diffraction measurements.  相似文献   
42.
A bicyclo[2.2.2]octadiene(BCOD)-fused bis(dipyrromethane) derivative was reacted with methylal in the presence of trifluoroacetic acid followed by oxidation with chloranil to give a doubly N-confused phlorin derivative, which did not undergo the retro-Diels–Alder reaction extruding an ethylene molecule on heating. In contrast, a 7-tert-butoxybicyclo[2.2.1]heptadiene(7-BuOBCHD)-fused bis(dipyrromethane) yielded benzene-ring-fused doubly N-confused porphyrins by following similar reaction sequences.  相似文献   
43.
44.
Base treatment of N-propargyl epoxyamide 5 afforded the acetylenic 3-(hydroxyethyl)-2-azetidinone 9a, which was subsequently transformed to phenyl thiolester 2, a versatile intermediate for the carbapenem synthesis.  相似文献   
45.
The urinary level of vanilmandelic acid (VMA) is one marker for diagnosis of neurblastoma in neonates. A large number of samples are needed for mass screening. In order to make a convenient and sophisticated assay, we examined a method based on dry chemistry by using a monoclonal antibody to VMA. The antibody adsorbed on the surface of the well of a microplate was equilibrated with VMA labeled with glucose oxidase (GOD-VMA). Free VMA in a sample competes with GOD-VMA for the binding sites of the antibody. An aliquot containing the excess GOD-VMA was spotted onto a multilayer film consisting of a spreading layer containing glucose and a reaction layer containing peroxidase and a leucodye. Hydrogen peroxide produced with GOD-VMA in the spreading layer penetrated the reaction layer and produced a blue dye. The amount of dye formed was measured by a reflection photometer. From a standard curve, VMA was measurable from 0.1 to 50 μg/ml. The values obtained by the present method were correlated with those by high-performance liquid chromatography and enzyme-linked immunosorbent assay.  相似文献   
46.
The photoetching behavior of poly(methylmethacrylate), poly(dimethylglutarimide) and chlorinated poly(methylstyrene) doped with pyrene and 4-aminobenzoylhydrazide excited by 308 nm excimer-laser pulses has been studied. Some common laser-etching characteristics including the reduction of the threshold fluence for ablation, the enhancement of etching efficiency and the existence of optimal conditions regarding the laser fluence and dopant concentration for generating clean and smooth etching patterns are identified. The photoetching mechanism and the potential application of the doping technique to material processing are discussed.  相似文献   
47.
Towards the synthesis of sterically hindered optically active secondary alcohol 2, yeast strains (Candida floricola IAM 13115 and Trichosporon cutaneum IAM 12206) with si-face hydride attack on isopropyl phenylsulfonylmethyl ketone 1 were developed by screening. Strains with complementary re-facial selectivity (Pichia angusta IAM 12895 and Pichia minuta IAM 12215) were also found. Based on the substrate specificity studies of these four strains, microbial reduction was applied to the synthesis of (3S,5S)-2,6-dimethyl-3,5-heptanediol 12a.  相似文献   
48.
Sodium dodecylsulfate capillary gel electrophoresis (SDS-CGE) was applied to measure the concentration ratios of albumin (Alb) and alpha2-macroglobulin (alphaMG) in the cerebrospinal fluid (CSF) and concurrent serum samples from patients with various neurological disorders. The values of the alphaMG index in individual patients were calculated on the basis of the peak area ratios of Alb and an alphaMG subunit on the CSF and serum electropherograms. The alphaMG index value thus obtained was most prominently raised in patients with inflammatory diseases of the brain and/or meninges, suggesting that the function of the blood-brain barrier (BBB) was disturbed under the pathological conditions in the central nervous system. The measurement of the concentration ratios of Alb and alphaMG in CSF and the concurrent serum samples by the present SDS-CGE system seems to be useful as an aid in the biochemical examination of the BBB function in patients with neurological disorders.  相似文献   
49.
Time-dependent mass spectra of mixture solutions of cytochrome c and cholesterol were measured by probe electrospray ionization (PESI) mass spectrometry and the PESI characteristics for several metal needles were investigated with different tip conditions. For a mixture solution of cytochrome c and cholesterol in 0.1% formic acid methanol/water (1/1) at a motion frequency of 1 Hz, an acupuncture needle with a sharp tip and 0.5-mm-diameter titanium and stainless-steel wire needles gave strong cytochrome c and extremely weak cholesterol ion signals. When the frequency was lowered, and the high-voltage duration increased, the titanium and stainless-steel needles provided both cytochrome c and cholesterol ion signals with high intensities well separated over time.  相似文献   
50.
Optical Review - To evaluate the repeatability of the optical coherence tomography (OCT) retinal shape measurement with and without alignment correction in children and adults. 62 eyes of the 31...  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