全文获取类型
收费全文 | 294篇 |
免费 | 7篇 |
国内免费 | 2篇 |
专业分类
化学 | 240篇 |
力学 | 2篇 |
数学 | 31篇 |
物理学 | 30篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2014年 | 11篇 |
2013年 | 16篇 |
2012年 | 18篇 |
2011年 | 25篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 21篇 |
2007年 | 29篇 |
2006年 | 20篇 |
2005年 | 24篇 |
2004年 | 19篇 |
2003年 | 18篇 |
2002年 | 14篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有303条查询结果,搜索用时 0 毫秒
91.
Using the technique of liquid crystal templating a rotating disc electrode (RDE) was modified with a high surface area mesoporous platinum film. The surface area of the electrode was characterised by acid voltammetry, and found to be very high (ca. 86 cm(2)). Acid characterisation of the electrode produced distorted voltammograms was interpreted as being due to the extremely large surface area which produced a combination of effects such as localised pH change within the pore environment and also ohmic drop effects. Acid voltammetry in the presence of two different types of surfactant, namely Tween 20 and Triton X-100, suggested antifouling properties associated with the mesoporous deposit. Further analysis of the modified electrode using a redox couple in solution showed typical RDE behaviour although extra capacitive currents were observed due to the large surface area of the electrode. The phenomenon of underpotential deposition was exploited for the purpose of anodic stripping voltammetry and results were compared with data collected for microelectrodes. Underpotential deposition of metal ions at the mesoporous RDE was found to be similar to that at conventional platinum electrodes and mesoporous microelectrodes although the rate of surface coverage was found to be slower at a mesoporous RDE. It was found that a mesoporous RDE forms a suitable system for quantification of silver ions in solution. 相似文献
92.
We present a model for coherent optical spectrum analysis that relates the key parameters of frequency resolution, power uncertainty, and sweep speed. The theoretical model is compared with experimental results obtained from spectral measurements of an external-cavity laser. 相似文献
93.
Inorganic chemistry and IONiC: an online community bringing cutting-edge research into the classroom
Jamieson ER Eppley HJ Geselbracht MJ Johnson AR Reisner BA Smith SR Stewart JL Watson LA Williams BS 《Inorganic chemistry》2011,50(13):5849-5854
This Viewpoint highlights creative ways that members of the Interactive Online Network of Inorganic Chemists (IONiC) are using journal articles from Inorganic Chemistry to engage undergraduate students in the classroom. We provide information about specific educational materials and networking features available free of charge to the inorganic community on IONiC's web home, the Virtual Inorganic Pedagogical Electronic Resource (VIPEr, www.ionicviper.org ) and describe the benefits of joining this community. 相似文献
94.
Brouwer N Liu Q Harrington D Kohen J Vemulpad S Jamie J Randall M Randall D 《Molecules (Basel, Switzerland)》2005,10(10):1252-1262
The Australian Aboriginal people have used plants as medicine and food for thousands of years, however, this traditional knowledge is documented only to a limited extent, and is in danger of being lost. The Indigenous Bioresources Research Group (IBRG) aims to help Australian Aboriginal communities to preserve their customary medicinal knowledge, and to provide information that can be used for their cultural or educational purposes, as well as for scientific advancement. This work is undertaken in close collaboration with Australian Aboriginal communities in New South Wales. The project is multidisciplinary, combining an ethnobotanical and an ethnopharmacological approach, which includes biological and chemical investigations, as well as developing best practices for protecting traditional knowledge. This paper describes the general strategy of the project as well as methods used in the ethnopharmacological study. Ethnobotanical databases are set up for each participating community. Plant material is collected, extracted, and active compounds are isolated using a bioassay-guided fractionation approach. All extracts and compounds are tested for biological activity in antimicrobial assays (disc diffusion, resazurin, fluorescein diacetate), neurological assays or anti-inflammatory assays, depending on their traditional use. 相似文献
95.
Katherine M. Phillips Wayne R. Wolf Kristine Y. Patterson Katherine E. Sharpless Karen R. Amanna Joanne M. Holden 《Accreditation and quality assurance》2007,12(3-4):126-133
Certified reference materials (CRMs) play a critical role in validating the accuracy of nutrient data for food samples. A
number of available food CRMs of differing matrix composition have assigned concentrations for various nutrients, along with
associated uncertainty intervals (UIs) for those values. These CRMs have been used extensively in the United States Department
of Agriculture’s (USDA) ongoing National Food and Nutrient Analysis Program (NFNAP) to monitor the accuracy of assays of key
foods and nutrients consumed in the United States. A total of 690 assigned values for individual nutrients, including proximates,
vitamins, macroelements, microelements, fatty acids, amino acids, and selected phytochemicals (e.g., carotenoids), were compiled
from the certificates of analysis for 63 CRMs, and the specified UI in each case was expressed as a percentage of the assigned
certified or reference concentration. Across all nutrients, 63.5% of the UIs were less than 10% of the assigned value, 25.5%
were 10–20%, and 11% were greater than 20% of the assigned value. The UIs for proximates, minerals, and trace elements were
most consistently less than 10% of the assigned value. The relative uncertainties were significantly higher for vitamins,
suggesting greater challenges in measuring and certifying these components. These high UIs (greater than 10% assigned value)
in the best available reference materials are likely to be indicative of the precision and accuracy that can be obtained by
current measurement systems for these components. These data suggest that care must be taken in choosing CRMs to monitor food
composition analysis, including evaluating what levels of uncertainty are required in assigned values and which analytical
measurement systems for food components need closer examination and improvement.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Presented at ‘BERM-10’, April 2006, Charleston, SC, USA. 相似文献
96.
My Hang V. Huynh Jennifer Smyth Modi Wetzler Brendan Mort Paul K. Gong Laura M. Witham Donald L. Jameson David K. Geiger Joanne M. Lasker Mina Charepoo Michelle Gornikiewicz Jose M. Cintron Gretchen Imahori Roberto R. Sanchez Amy C. Marschilok Lynn M. Krajkowski David G. Churchill Melvyn Rowen Churchill Kenneth J. Takeuchi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2001,113(23):4601-4605
97.
Localized Mixed‐Valence and Redox Activity within a Triazole‐Bridged Dinucleating Ligand upon Coordination to Palladium 下载免费PDF全文
Daniël L. J. Broere Raoul Plessius Dr. Joanne Tory Dr. Serhiy Demeshko Prof. Dr. Bas de Bruin Dr. Maxime A. Siegler Prof. Dr. Frantisek Hartl Dr. Jarl Ivar van der Vlugt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13965-13975
The new dinucleating redox‐active ligand ( LH4 ), bearing two redox‐active NNO‐binding pockets linked by a 1,2,3‐triazole unit, is synthetically readily accessible. Coordination to two equivalents of PdII resulted in the formation of paramagnetic (S= ) dinuclear Pd complexes with a κ2‐N,N′‐bridging triazole and a single bridging chlorido or azido ligand. A combined spectroscopic, spectroelectrochemical, and computational study confirmed Robin–Day Class II mixed‐valence within the redox‐active ligand, with little influence of the secondary bridging anionic ligand. Intervalence charge transfer was observed between the two ligand binding pockets. Selective one‐electron oxidation allowed for isolation of the corresponding cationic ligand‐based diradical species. SQUID (super‐conducting quantum interference device) measurements of these compounds revealed weak anti‐ferromagnetic spin coupling between the two ligand‐centered radicals and an overall singlet ground state in the solid state, which is supported by DFT calculations. The rigid and conjugated dinucleating redox‐active ligand framework thus allows for efficient electronic communication between the two binding pockets. 相似文献
98.
99.
Alan G. Osborne Richard J. Cremlyn Joanne F. Warmsley 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1995,51(14)
13C Chemical shifts and JCH coupling constants are reported for xanthene and for some dimedone adducts containing a xanthene ring. A revised correlation pattern for the carbocyclic ring 3JCH meta-couplings in fused oxygen heterocycles is proposed in which the magnitude of the interactions alternate around the ring. 相似文献
100.