全文获取类型
收费全文 | 210篇 |
免费 | 2篇 |
专业分类
化学 | 118篇 |
力学 | 6篇 |
数学 | 18篇 |
物理学 | 70篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2016年 | 3篇 |
2014年 | 3篇 |
2013年 | 15篇 |
2012年 | 10篇 |
2011年 | 13篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 14篇 |
2007年 | 8篇 |
2006年 | 17篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1967年 | 1篇 |
1963年 | 1篇 |
1960年 | 3篇 |
1958年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有212条查询结果,搜索用时 15 毫秒
11.
Devdutt Chaturvedi Nisha Mishra Amit K. Chaturvdi Virendra Mishra 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):550-558
A quick and efficient, one-pot synthesis of dithiocarbazates was accomplished in high yields by the reaction of various alcoholic tosylates of primary, secondary, and tertiary alcohols, with substituted hydrazines using an Amberlite IRA 400 (basic resin)/CS 2 system. The reaction conditions are mild with simpler work-up procedures than previously reported methods. 相似文献
12.
Venkatesh K. Pandey Kalpana Chaturvedi Ruchi Chandra Om P. Pandey Soumitra K. Sengupta 《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):1401-1408
Abstract A series of biologically active organophosphorus compounds have been synthesized by the reactions of O,O-diethylchlorophosphate with Schiff bases derived from 5-(phenyl/substituted phenyl)-2-hydrazino-1,3,4-oxadiazole and salicylaldehyde/2-hydroxyacetophenone. The compounds have been characterized on the basis of analyses and spectral (IR, 1H, 13C NMR) data. Fungicidal activities of these derivatives against Colletotrichum falcatum, Fusarium oxysporum, and Curvularia pallescence have been evaluated. All compounds showed moderate to significant antifungal activity. 相似文献
13.
A quick, efficient, one-pot synthesis of dithiocarbazates was accomplished in high yields by the reaction of various tosylates of primary, secondary, and tertiary alcohols with a variety of substituted hydrazines using the benzyl–trimethylammonium hydroxide (Triton-B)/CS2 system. The reaction conditions are mild with simpler workup procedures than the reported methods. 相似文献
14.
We present a new approach to Hamilton’s theory of turns for the groups SO(3) and SU(2) which renders their properties, in particular their composition law, nearly trivial and immediately evident upon inspection.
We show that the entire construction can be based on binary rotations rather than mirror reflections. 相似文献
15.
S. Chaturvedi 《Optics and Spectroscopy》2007,103(3):405-410
The Poisson Summation Formula and the sampling theorem for band limited signals, well known in the context of Fourier transformation
theory, are analyzed from the perspective of the Zak basis and coherent state systems associated with the Heisenberg-Weyl
group. In particular, we rephrase the content of the sampling theorem in terms coherent states and show that this in turn
permits extensions, which allow us to make specific statements concerning standard and generalized coherent state systems
on von Neumann or finer lattices.
The text was submitted by the author in English. 相似文献
16.
A series of some new mixed ligand complexes have been synthesized with an objective for evaluation as antimicrobials. Reactions of diorganotin(IV) dichloride with dibenzoyl methane and O‐alkyl trithiophosphates in a 1:1:1 molar ratio in refluxing benzene yield products of the type [PhCOCHCOPh]R2Sn‐[SSH(S)POR'] [where R = Me, Bu, Ph; R' = Me, Et, Pri, Bui, Ph]. The newly synthesized complexes are light yellow colored crystalline solids, non‐volatile, soluble in common organic solvents, monomeric in nature and highly sensitive towards atmospheric moisture. These complexes are characterized by elemental analysis, IR and multinuclear NMR (1H, 31P and 119Sn) spectral studies. Spectral studies of these complexes indicate that dibenzoyl methane and O‐alkyl trithiophosphate moieties are bidentate and the central tin atom is hexacoordinated in nature. A few of these compounds were tested for their antibacterial activity using standard drugs. 相似文献
17.
Jeevan Jaisingh Jack Barron Shailendra Mehta Alok Chaturvedi 《European Journal of Operational Research》2008
The issues we address here are – How should a firm (e.g. Internet service provider (ISP)) that is capable of collecting personal information (browsing information, purchase history, etc.) about consumers, price its service, given that consumers vary in their valuation for privacy, and also vary in terms of the value of their personal information to a third party (firms that need consumer information)? Should the firm have a blanket policy of never collecting, or a policy of always collecting and revealing information? Surprisingly we find that in some cases the collector of information may be no worse off in the asymmetric information case than in the full information case. The paper provides a justification for the strategy of some firms such as ISP’s which never collect information and also for the strategy of other firms, like grocery stores that do. We also find that it is non-optimal for the firm to design contracts where the consumer can choose an intermediate level of privacy. 相似文献
18.
Devdutt Chaturvedi Nisha Mishra Virendra Mishra 《Monatshefte für Chemie / Chemical Monthly》2008,12(2):1033-1036
A quick and efficient, one-pot synthesis of dithiocarbazates was accomplished in high yields by the reaction of various primary,
secondary, and tert. alkyl halides with a variety of substituted hydrazines using the benzyl-trimethylammonium hydroxide (Triton-B)/CS2 system. The reaction conditions are mild with simpler work-up procedures than the reported methods. 相似文献
19.
Ashutosh Tiwari Rajendra Kumar Mani Prabaharan Ravi R. Pandey Premlata Kumari Anurag Chaturvedi A. K. Mishra 《先进技术聚合物》2010,21(9):615-620
A nanofibrous polyaniline (PANI) thin film was fabricated using plasma‐induced polymerization method and explored its application in the fabrication of NO2 gas sensor. The effects of substrate position, pressure, and the number of plasma pulses on the PANI film growth rate were monitored and an optimum condition for the PANI thin film preparation was established. The resulting PANI film was characterized with UV–visible spectrophotometer, FTIR, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The PANI thin film possessed nanofibers with a diameter ranging from 15 to 20 nm. The NO2 gas sensing behavior was studied by measuring the change in electrical conductivity of PANI film with respect to NO2 gas concentration and exposure time. The optimized sensor exhibited a sensitivity factor of 206 with a response time of 23 sec. The NO2 gas sensor using nanofibrous PANI thin film as sensing probe showed a linear current response to the NO2 gas concentration in the range of 10–100 ppm. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
20.
Nalin A. Chaturvedi Taeyoung Lee Melvin Leok N. Harris McClamroch 《Journal of Nonlinear Science》2011,21(1):3-32
A 3D pendulum consists of a rigid body, supported at a fixed pivot, with three rotational degrees of freedom. The pendulum
is acted on by a gravitational force. 3D pendulum dynamics have been much studied in integrable cases that arise when certain
physical symmetry assumptions are made. This paper treats the non-integrable case of the 3D pendulum dynamics when the rigid
body is asymmetric and the center of mass is distinct from the pivot location. 3D pendulum full and reduced models are introduced
and used to study important features of the nonlinear dynamics: conserved quantities, equilibria, relative equilibria, invariant
manifolds, local dynamics, and presence of chaotic motions. The paper provides a unified treatment of the 3D pendulum dynamics
that includes prior results and new results expressed in the framework of geometric mechanics. These results demonstrate the
rich and complex dynamics of the 3D pendulum. 相似文献