全文获取类型
收费全文 | 1013篇 |
免费 | 46篇 |
国内免费 | 8篇 |
专业分类
化学 | 590篇 |
晶体学 | 10篇 |
力学 | 46篇 |
数学 | 247篇 |
物理学 | 174篇 |
出版年
2023年 | 14篇 |
2022年 | 24篇 |
2021年 | 36篇 |
2020年 | 29篇 |
2019年 | 43篇 |
2018年 | 31篇 |
2017年 | 35篇 |
2016年 | 47篇 |
2015年 | 48篇 |
2014年 | 44篇 |
2013年 | 73篇 |
2012年 | 67篇 |
2011年 | 78篇 |
2010年 | 47篇 |
2009年 | 35篇 |
2008年 | 40篇 |
2007年 | 29篇 |
2006年 | 32篇 |
2005年 | 33篇 |
2004年 | 28篇 |
2003年 | 21篇 |
2002年 | 20篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1998年 | 8篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 17篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1970年 | 3篇 |
排序方式: 共有1067条查询结果,搜索用时 15 毫秒
41.
Thanh Duc Mai Benjamin Bomastyk Hong Anh Duong Hung Viet Pham Peter C. Hauser 《Analytica chimica acta》2012
An extension of a capillary electrophoresis instrument coupled to a sequential injection analysis manifold was developed for automated measurements with on-line solid-phase extraction preconcentration. An in-house built capacitively coupled contactless conductivity detector was employed for sensitive detection with narrow capillaries of 25 μm internal diameter. The system was assembled into standardized 19 in. frames and racks for easy transport and mobile deployment. The system can be left running unattendedly without manual intervention with good operation stability. To demonstrate the application of the system, a method for the determination of four drugs, namely ibuprofen, diclofenac, naproxen and bezafibrate, was developed with enrichment factors of up to several hundreds. Detection of the drug residues down to the nM-scale was found possible and the method was found suitable for the detection of ibuprofen in the waste water of a hospital in Hanoi. 相似文献
42.
Oncogenic MicroRNAs Biogenesis as a Drug Target: Structure–Activity Relationship Studies on New Aminoglycoside Conjugates 下载免费PDF全文
43.
Amin Moosaie Anne Le Duc Michael Manhart 《ournal of non Newtonian Fluid Mechanics》2010,165(9-10):551-554
A normalization scheme for the numerical solution of the moment approximation equation in fiber suspension flows is presented. Here, normalization refers to rescaling the trace of the second moment tensor to unity at each time step. The equivalence between the normalization scheme and the quadratic closure model is analytically proved. The performance of the scheme is investigated in simple shear flow with respect to the quadratic and hybrid closures, and a stochastic Monte-Carlo simulator that provides exact solution. The proposed scheme is a computationally efficient alternative to the quadratic closure: it performs equally well and is more efficient regarding computational time. 相似文献
44.
Dr. Tran Quang Hung Dr. Ferial Terki Dr. Souleymane Kamara Mourad Dehbaoui Prof. Salam Charar Brajalal Sinha Prof. CheolGi Kim Dr. Philippe Gandit Il'ya A. Gural'skiy Dr. Gabor Molnar Dr. Lionel Salmon Dr. Helena J. Shepherd Dr. Azzedine Bousseksou 《Angewandte Chemie (International ed. in English)》2013,52(4):1058-1058
45.
Duc Hoai Do Christophe Walgraeve Samuel Fekadu Hayleeyesus Patrick De Wispelaere Jo Dewulf 《International journal of environmental analytical chemistry》2013,93(3):298-314
The effects of urban and indoor air pollution on human health are a major environmental concern for all, but not much has been researched in the developing world. Specifically, quantitative data on the occurrence of volatile organic compounds (VOCs) – main contributors to air pollution – in Asia and Africa are scarce compared to the availability of data in the developed world. This paper presents one of the first studies focusing on the analysis and occurrence of VOCs in Vietnam and Ethiopia, which constitutes part of the novelty of this work. A spectrum of 34 VOCs was measured at eight different urban sites in Ghent (Belgium), Hanoi (Vietnam), Jimma and Addis Ababa (Ethiopia) during three sampling campaigns from September 2008 to September 2010. Sampling was done in an active way by means of sorbent tubes filled with Tenax TA. The analysis was done by TD-GC-MS using internal standard calibration. Data were interpreted and compared in terms of (i) individual, subgroup and total VOCs concentration (TVOCs), (ii) indoor-to-outdoor (I/O) concentration ratios, (iii) source identification by diagnostic ratio and/or correlation coefficients, and (iv) ozone formation potential (OFP) at outdoor sites based on up-to-date maximum incremental reactivity (MIR). I/O concentration ratios varied between 0.2 and 30, with big differences noticed with respect to the type of VOC(s) considered and the type of outdoor sampling location. The highest TVOC concentrations were measured in street samples with maximum values of 54?µg/m3 in Ghent, 507?µg/m3 in Hanoi and 318?µg/m3 in Addis Ababa illustrating the large difference in ambient air quality levels. This is also reflected in the arithmetic mean OFP values (µg/m3) of 82, 1308 and 596 in Ghent, Hanoi and Addis Ababa, respectively. Results of this study could be helpful to support formulation of national policy with regard to ambient air quality. 相似文献
46.
Dr. Madleen Busse Iman Trinh Prof. Peter C. Junk Assoc. Prof. Richard L. Ferrero Prof. Philip C. Andrews 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(17):5264-5275
The synthesis and characterisation of nine new tris‐substituted bismuth(III) aminoarenesulfonates of the general formula [Bi(O3S‐RN)3] (RN=o‐aminophenyl 1 , m‐aminophenyl 2 , 6‐amino‐3‐methoxyphenyl 3 , p‐aminophenyl 4 , 2‐pyridyl 5 , o‐aminonaphthyl 6 , 5‐aminonaphthyl 7 , 4‐amino‐3‐hydroxynaphthyl 8 and 5‐isoquinolinyl 9 ) is described. Two synthetic strategies, using Ag2O and [Bi(OtBu)3], were explored and compared. The possibility to access heteroleptic bismuth(III) complexes with the new silver(I) metathesis reaction is demonstrated with the synthesis of the heteroleptic bismuth(III) aminoarenesulfonate complexes [PhBi(O3S‐P2)2(dmso)] 10 , [Ph2Bi(O3S‐P2)]∞ 11 and [PhBi(O3S‐P2)2]∞ 12 , of which the solid state structures 10 and 12 are presented (2P‐SO3?=2‐pyridinesulfonate). These complexes offer remarkable in‐vitro activity against three standard laboratory strains of Helicobacter pylori (H. pylori) as demonstrated by their exceptionally low minimum inhibitory concentration (MIC) values of 0.049 μg mL?1 for the strains 251 and B128, which places most MIC values in the nano‐molar region. These results demonstrate the importance of the amino functionality in addition to the sulfonate group on the bactericidal properties against H. pylori. 相似文献
47.
Abdelhouad Oukhrib Laurence Bonnafoux Armen Panossian Sandrine Waifang Duc Hanh Nguyen Martine Urrutigoity Françoise Colobert Maryse Gouygou Frédéric R. Leroux 《Tetrahedron》2014
A new family of non-symmetrical disubstituted dibenzophospholes possessing different steric and electronic effects have been synthesized and characterized. Their preliminary evaluation in rhodium-catalyzed hydroformylation reactions is presented. 相似文献
48.
49.
The radical telomerisation of vinylidene fluoride (VDF) with 2-mercaptoethanol as chain transfer agent (CTA) was studied to synthesise fluorinated telomers which bear a hydroxy end-group, such as H(VDF)nS(CH2)2OH, under thermal (di-tert-butyl peroxide as the initiator) or photochemical initiations. A careful structural study of a typical H-VDF-S(CH2)2OH telomer was performed by 1H and 19F NMR spectroscopy. These analytical methods allowed us to explore the selective addition of the thiyl radical onto the hydrogenated side of VDF, and the telomer containing one VDF unit was obtained selectively. Surprisingly, for higher [VDF]o initial concentrations, a monoadduct telomer was produced as well as PVDF homopolymer. This feature was related to the fast consumption of the CTA. The kinetics of radical telomerisation led to a quite high transfer constant of the CTA (40 at 140 °C) that evidences the formation of a monoadduct as the only telomer formed. 相似文献
50.
Sheida Esmail Tehrani Long Quang Nguyen Giulia Garelli Bettina M. Jensen Tautgirdas Ruzgas Jenny Emnéus Stephan Sylvest Keller 《Electroanalysis》2021,33(12):2516-2528
A highly sensitive amperometric Prussian blue-based hydrogen peroxide sensor was developed using 3D pyrolytic carbon microelectrodes. A 3D printed multielectrode electrochemical cell enabled simultaneous highly reproducible Prussian blue modification on multiple carbon electrodes. The effect of oxygen plasma pre-treatment and deposition time on Prussian blue electrodeposition was studied. The amperometric response of 2D and 3D sensors to the addition of hydrogen peroxide in μM and sub-μM concentrations in phosphate buffer was investigated. A high sensitivity comparable to flow injection systems and a detection limit of 0.16 μM was demonstrated with 3D pyrolytic carbon microelectrodes at stirred batch condition 相似文献