全文获取类型
收费全文 | 2398篇 |
免费 | 79篇 |
国内免费 | 24篇 |
专业分类
化学 | 1465篇 |
晶体学 | 7篇 |
力学 | 42篇 |
数学 | 428篇 |
物理学 | 559篇 |
出版年
2023年 | 9篇 |
2022年 | 27篇 |
2021年 | 28篇 |
2020年 | 38篇 |
2019年 | 32篇 |
2018年 | 31篇 |
2017年 | 41篇 |
2016年 | 61篇 |
2015年 | 59篇 |
2014年 | 61篇 |
2013年 | 129篇 |
2012年 | 187篇 |
2011年 | 176篇 |
2010年 | 123篇 |
2009年 | 111篇 |
2008年 | 160篇 |
2007年 | 167篇 |
2006年 | 168篇 |
2005年 | 204篇 |
2004年 | 140篇 |
2003年 | 125篇 |
2002年 | 115篇 |
2001年 | 19篇 |
2000年 | 23篇 |
1999年 | 15篇 |
1998年 | 15篇 |
1997年 | 15篇 |
1996年 | 33篇 |
1995年 | 17篇 |
1994年 | 17篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 5篇 |
1972年 | 3篇 |
1970年 | 2篇 |
排序方式: 共有2501条查询结果,搜索用时 15 毫秒
81.
Luis M. Fidalgo Graeme Whyte Dr. Brandon T. Ruotolo Dr. Justin L. P. Benesch Dr. Florian Stengel Chris Abell Prof. Carol V. Robinson Prof. Wilhelm T. S. Huck Prof. 《Angewandte Chemie (International ed. in English)》2009,48(20):3665-3668
Fully integrated : Mass spectrometry has been integrated into a detection scheme for microdroplets that are created within microfluidic channels (see picture, scale bar 200 μm). This technique allows droplets to be identified based on the compounds they contain, and combines fluorescence screening with MS analysis. These experiments indicate how similar approaches can be applied to the ambitious goals of on‐chip protein evolution and chemical synthesis.
82.
We report a method of coupled CE-LIF detection with flow cytometry for high-throughput determination and quantitation of fluorophores in single intact K562/S (KS) cells. The membrane properties of KS cell including fluophore transport rate and apparent permeability coefficient were further quantitatively characterized. The method has advantages for accurate quantitation and unique capacity of high-throughput analysis. The strategy will be useful for the quantitation of fluorophores in the intact cells, such as measurement of multidrug resistance, quantitation of specific protein expression, and quantitative characterization of protein and enzyme functions. 相似文献
83.
Ya?ar Dürüst Muhammet Y?ld?r?m Chris F. Fronczek Frank R. Fronczek 《Monatshefte für Chemie / Chemical Monthly》2012,38(2):127-138
Abstract
Eleven novel dihydropyrrolo[3,4-c]pyrazole derivatives were obtained by the reaction of chiral (1R)-N-(1-phenylethyl)maleimide and C,N-aryl-substituted nitrilimines. The reaction afforded the cycloadducts as a regioisomeric mixture which can be separable in some cases. The structure and stereochemistry of cycloadducts were assigned on the basis of infrared (IR), 1H and 13C nuclear magnetic resonance (NMR), mass and X-ray spectra, optical rotation measurements, and CHN analyses. 相似文献84.
高效液相色谱/氢化物发生/原子荧光快速检测尿砷形态 总被引:15,自引:0,他引:15
本文对砷形态分析方法进行了评述。提出了人尿中As(Ⅲ)、As(Ⅴ)、一甲基砷(MMA)和二甲基砷(DMA)的快速、灵敏的形态分析方法。方法基于在15cm长、3μm粒径的HPLC柱上快速分离不同形态的砷后以灵敏的氢化物发生/原子荧光检测。常见砷的四种形态的分析只须4min即可完成,检出限在μg/L级。标准样品尿中砷的形态分析结果与标准值吻合很好。本法已应用于摄取砷糖前、后所采集的尿样中砷的形态分析研 相似文献
85.
Chris Roberts Roy L. Johnston Nicholas T. Wilson 《Theoretical chemistry accounts》2000,104(2):123-130
This article describes the application of a genetic algorithm for the structural optimization of 19–50-atom clusters bound
by medium-range and short-range Morse pair potentials. The GA is found to be efficient and reliable for finding the geometries
corresponding to the previously published global minima [Doye JPK, Wales DJ (1997) J Chem Soc Faraday Trans 93: 4233]. Using the genetic algorithm, only a relatively small number of energy evaluations and minimizations are required
to find the global minima. By contrast, a simple random search algorithm often cannot find the global minima of the larger
clusters, even after many thousands of searches.
Received: 27 October 1999 / Accepted: 7 December 1999 / Published online: 19 April 2000 相似文献
86.
Kate J. Graham Chris P. Schaller Brian J. Johnson John B. Klassen 《The Chemical Educator》2002,7(6):376-378
The incorporation of research projects into undergraduate chemistry courses provides a perspective that is fundamentally unavailable in most laboratory experiences. While independent, multistep synthesis projects in organic chemistry have been reported previously, most efforts have been directed at relatively restricted, closely guided research plans with modest student participation in the experimental design. We have implemented a more open-ended synthesis project, limited principally by cost, safety and availability of materials. In the second semester of the sophomore organic sequence, students develop multiple drafts of a plan for a three-to-four-step synthesis. Subsequently, students obtain their own literature protocols for the individual steps. The synthesis is performed over three four-hour laboratory periods. The students conclude this project with a poster presentation of the results at the end of the semester. Evaluation of the students work focuses not only on the successful synthesis of the target but also on planning, troubleshooting, purification, and spectral analysis. 相似文献
87.
Louis P. Lee Daniel J. Cole Mike C. Payne Chris‐Kriton Skylaris 《Journal of computational chemistry》2013,34(6):429-444
First principles electronic structure calculations are typically performed in terms of molecular orbitals (or bands), providing a straightforward theoretical avenue for approximations of increasing sophistication, but do not usually provide any qualitative chemical information about the system. We can derive such information via post‐processing using natural bond orbital (NBO) analysis, which produces a chemical picture of bonding in terms of localized Lewis‐type bond and lone pair orbitals that we can use to understand molecular structure and interactions. We present NBO analysis of large‐scale calculations with the ONETEP linear‐scaling density functional theory package, which we have interfaced with the NBO 5 analysis program. In ONETEP calculations involving thousands of atoms, one is typically interested in particular regions of a nanosystem whilst accounting for long‐range electronic effects from the entire system. We show that by transforming the Non‐orthogonal Generalized Wannier Functions of ONETEP to natural atomic orbitals, NBO analysis can be performed within a localized region in such a way that ensures the results are identical to an analysis on the full system. We demonstrate the capabilities of this approach by performing illustrative studies of large proteins—namely, investigating changes in charge transfer between the heme group of myoglobin and its ligands with increasing system size and between a protein and its explicit solvent, estimating the contribution of electronic delocalization to the stabilization of hydrogen bonds in the binding pocket of a drug‐receptor complex, and observing, in situ, the n → π* hyperconjugative interactions between carbonyl groups that stabilize protein backbones. © 2012 Wiley Periodicals, Inc. 相似文献
88.
The introduction of electron rich and sterically hindered ligands has made otherwise inert aryl chlorides and hetero aryl chlorides viable coupling partners in palladium-catalyzed Suzuki-Miyaura, Sonogashira, Stille and other types of cross-coupling reactions. This review gives highlights of cross-coupling of aryl chlorides employing in situ generated palladium catalytic systems. 相似文献
89.
Andrea Ventrella Raffaella Verrone Francesco Longobardi Angela Agostiano Vincenzo Lippolis Michelangelo Pascale Chris M. Maragos Michael Appell Lucia Catucci 《Journal of inclusion phenomena and macrocyclic chemistry》2013,75(3-4):285-292
T-2 and HT-2 toxins are mycotoxins produced by several Fusarium species that are commonly found in various cereal grains, including oats, barley, wheat and maize. Intake estimates indicate that the presence of these mycotoxins in the diet can be of concern for public health. In this work, the inclusion processes occurring between fluorescent anthracene-derivatives of T-2 and HT-2 toxins and different cyclodextrin (CD) molecules were investigated in aqueous solutions by means of UV–Vis absorption, fluorescence emission and dynamic light scattering. Binding constant values and chemico-physical parameters were calculated. It was found that β-CDs give stronger inclusion reactions with both T-2 and HT-2 derivatives, as stated by important emission intensity increments. Such interactions were found to be fundamentally enthalpy-driven. Among β-CDs, the effect of the methylation at hydroxyl groups was tested: as a result, the di-methyl form of β-CD was found to induce the best fluorescence intensity enhancements. 相似文献
90.
Xiao-jun Wang Li Zhang Yibo Xu Dhileepkumar Krishnamurthy Chris H. Senanayake 《Tetrahedron letters》2004,45(38):7167-7170
A practical protocol for synthesis of 2-(N-substituted)-aminobenzimidazoles was developed. N-(2-Aminoaryl)thioureas undergo a CuCl-promoted intramolecular cyclization to give the corresponding 2-(N-substituted amino)benzimidazoles in good to excellent isolated yields. 相似文献