全文获取类型
收费全文 | 1632篇 |
免费 | 51篇 |
国内免费 | 3篇 |
专业分类
化学 | 1190篇 |
晶体学 | 28篇 |
力学 | 70篇 |
数学 | 103篇 |
物理学 | 295篇 |
出版年
2023年 | 10篇 |
2022年 | 13篇 |
2021年 | 32篇 |
2020年 | 46篇 |
2019年 | 58篇 |
2018年 | 42篇 |
2017年 | 37篇 |
2016年 | 48篇 |
2015年 | 53篇 |
2014年 | 63篇 |
2013年 | 120篇 |
2012年 | 130篇 |
2011年 | 135篇 |
2010年 | 75篇 |
2009年 | 65篇 |
2008年 | 113篇 |
2007年 | 74篇 |
2006年 | 90篇 |
2005年 | 68篇 |
2004年 | 49篇 |
2003年 | 38篇 |
2002年 | 37篇 |
2001年 | 20篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 14篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1964年 | 3篇 |
排序方式: 共有1686条查询结果,搜索用时 265 毫秒
101.
D. Ramana A. K. Capoor R. B. Sashidhar Ramesh V. Bhat 《Fresenius' Journal of Analytical Chemistry》1995,352(1-2):43-48
Horseradish peroxidase (HRPO) was used as a probe to quantitate aflatoxin B1 by a homogeneous immunoassay. The conjugation of AFB1 to HRPO resulted in 54% loss of enyzme activity. In the presence of AFB1 specific antibodies, the HRPO-AFB1 conjugate showed reversal of its lost enzyme activity by 12%. This positive modulatory effect of antibody on the enzyme activity was used as an analytical tool to quantitate AFB1. The homogeneous assay carried out with free AFB1 and HRPO-AFB1 conjugate in the presence of antibodies indicated poor linearity as compared to the heterogeneous assay. It was observed that the number of HRPO-lysine residues involved in AFB1 conjugation were 6–8. The low level of modulation of enzyme activity by antibody with respect to HRPO-AFB1 conjugate, could possibly be attributed to the limited number of lysine residues in the HRPO molecule and its proximity to the active site of the enzyme. Thus, HRPO was found to be limiting as an enzyme with respect to the homogeneous enzyme immunoassay for AFB1 analysis. The antibodies raised were specific for AFB1, and showed excellent linearity even at high dilution for the detection of AFB1 by ELISA indicating that antibodies per se were not the limiting factor. 相似文献
102.
The complexes [(η5-C5H5)M(CO)nPbPh3] (M = Fe, Cr, Mo, W) have been studied with respect to their thermal and photochemical stability and their reactivity with respect to SO2. The iron complex is the only complex that exhibits the ability to decompose via a 1,2-phenyl migration to the transition metal under thermal conditions, but photochemically the tungsten complex also exhibits this behaviour. All complexes react readily with SO2 to yield the corresponding sulphinatophenyl complexes, LMSO2Ph, in high yield. 相似文献
103.
Summary Binuclear iron(III) derivatives, Fe2Cl(anth)5, Fe2Cl(salH)5, Fe2Cl(acac)5 and Fe2Cl(quin)5 · quinH have been prepared by reacting Fe2Cl(OH)2(AcO)3 · 2AcOH with anthranilic acid (anthH), salicylic acid (salH2), acetylacetone (acacH) and 8-hydroxyquinoline (quinH), respectively. These compounds have been characterised by molecular weight, conductance, i.r. spectral, magnetic susceptibility and Mössbauer measurements. 相似文献
104.
Harry L. Yale James A. Bristol Ramesh B. Petigara 《Journal of heterocyclic chemistry》1975,12(3):489-492
Procedures for the isolation of 1,2-dihydro-4-(trifluoromethyl)-3H,8H-quino[1,8-ab][4,1]-benzoxazepine, 3 , from reaction mixtures containing 3 as the minor component, and the isomer, 1,2-dihydro-11-(trifluoromethyl)-3H,7H-quino[8,1-cd][1,5]benzoxazepin-3-one, 2 , as the major component, are described. The reactivity of 3 toward hydroxylamine and aromatic aldehydes has been investigated and the preparation of derivatives with those reactants is described. 相似文献
105.
Summary Dichlorobis(cyclopentadienyl)titanium(IV), Cp2TiCI2, reacts with bidentate Schiff bases such as salicylideneaniline, salicylidene-o-toluidine, salicylidene-m-toluidine, salicylidene-p-toluidine and 2-hydroxy-l-naphthylReprints of this paper are not available.To whom all correspondence should be addressed. 相似文献
106.
[reaction: see text] A novel C2-symmetric protecting group for amines, the but-2-ynylbisoxycarbonyl (Bbc) group, is developed, which can be deblocked with tetrathiomolybdate under neutral conditions. One equivalent of the bischloroformate, BbcCl, is used for the protection of 2 equiv of the amine. Its application in peptide synthesis is established through the synthesis of a tripeptide, and its orthogonality with Cbz, Fmoc, and Boc groups has been studied. 相似文献
107.
Zhao T Shinde SR Ogale SB Zheng H Venkatesan T Ramesh R Das Sarma S 《Physical review letters》2005,94(12):126601
An external electric field induced reversible modulation of a room temperature magnetic moment and coercive field is achieved in an epitaxial and insulating thin film of dilutely cobalt-doped anatase TiO2. This first demonstration of an electric field effect in any oxide-based diluted ferromagnet is realized in a high quality epitaxial heterostructure of PbZr(0.2)Ti(0.8)O(3)/Co: TiO(2)/SrRuO(3) grown on (001) LaAlO3. The observed effect, which is about 15% in strength in a given heterostructure, can be modulated over several cycles. Possible mechanisms for electric field induced modulation of insulating ferromagnetism are discussed. 相似文献
108.
Ebenezer DD Ravichandran K Ramesh R Padmanabhan C 《The Journal of the Acoustical Society of America》2005,117(6):3645-3656
A method is presented to determine the forced responses of piezoelectric cylinders using weighted sums of only certain exact solutions to the equations of motion and the Gauss electrostatic conditions. One infinite set of solutions is chosen such that each field variable is expressed in terms of Bessel functions that form a complete set in the radial direction. Another infinite set of solutions is chosen such that each field variable is expressed in terms of trigonometric functions that form a complete set in the axial direction. Another solution is used to account for the electric field that can exist even when there is no vibration. The weights are determined by using the orthogonal properties of the functions and are used to satisfy specified, arbitrary, axisymmetric boundary conditions on all the surfaces. Special cases including simultaneous mechanical and electrical excitation of cylinders are presented. All numerical results are in excellent agreement with those obtained using the finite element software ATILA. For example, the five lowest frequencies at which the conductance and susceptance of a stress-free cylinder, of length 10 mm and radius 5 mm, reach a local maximum or minimum differ by less than 0.01% from those computed using ATILA. 相似文献
109.
Coherent backscattering (CBS) of light in random media has been previously investigated by use of coherent light sources. Here we report a novel method of CBS measurement that combines low spatial coherence, broadband illumination, and spectrally resolved detection. We show that low spatial coherence illumination leads to an anomalously broad CBS peak and a dramatic speckle reduction; the latter is further facilitated by low temporal coherence detection. Thus CBS can be observed in biological tissue and other media that previously were beyond the reach of conventional CBS measurements. We also demonstrate, for the first time to our knowledge, spectroscopic analysis of CBS. CBS spectroscopy may find important applications in probing random media such as biological tissue in which depth-selective measurements are crucial. 相似文献
110.
A simple and efficient method has been developed for chemoselective deprotection of phenolic methoxymethyl (MOM) ethers using silica-supported sodium hydrogen sulfate as a heterogeneous catalyst. The conversions occur at room temperature, and the yields of the deprotected phenols are excellent. The method is suitable for deprotection of phenolic MOM ethers of multifunctional bioactive natural products. 相似文献