全文获取类型
收费全文 | 249篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 175篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 8篇 |
物理学 | 66篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 12篇 |
2018年 | 2篇 |
2017年 | 8篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 11篇 |
2013年 | 26篇 |
2012年 | 14篇 |
2011年 | 23篇 |
2010年 | 14篇 |
2009年 | 11篇 |
2008年 | 19篇 |
2007年 | 7篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 11篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1998年 | 1篇 |
1993年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有255条查询结果,搜索用时 15 毫秒
81.
S Chopra N S Pawar M P Singh Rakesh Kumar J Prasad V P Patel Raj Pal B Kumar S Ojha K Devarani T Nandi M Sota P Barua S Gargari R Joshi D Kanjilal SK Datta 《Pramana》2002,59(5):753-759
The 15 UD pelletron at NSC has been operational and performed well during the last 11 years. There have been major modifications
performed for upgradation of pelletron system over this period. Major upgradations which have been implemented are new resistor
network system for voltage gradient, doublet to singlet unit conversion for accelerator units, turbopump based gas stripper
system etc. In addition accelerator mass spectroscopy program has also been started. A new multi-cathode source, Wien filter
etc. have been procured and will be added soon in the system. An overview of the most significant upgradations undertaken
and other activities for the system are being reported in the present paper. 相似文献
82.
The dielectric relaxation parameters, viz., static dielectric constant, ɛ, and relaxation times, τ, have been determined for chlorobenzene-methanol (CB-MET), 1,2 dichloro ethanemethanol (DE-MET) and dimethylene chloride-methanol
(DC-MET) mixtures with thirteen different concentrations at three temperatures, viz., 15, 25 and 45°C. The experimental technique
used for this work was the time domain reflectometry (TDR) in the frequency range of 10 MHz to 20 GHz using the Hewlett Packard
HP 54750 sampling oscilloscope. The information regarding hydrogen bonding structural behavior in MET due to CB, DE and DC
are obtained by using the theoretical models based on the excess properties. The data suggest that CB and DE are not influenced
by hydrogen bonding in MET whereas DC is influenced by the hydrogen bonding mechanism in MET. It appears that the behavior
of DC on MET is different from CB and DE in MET. 相似文献
83.
The concept of `adjunct' operation of two lattices with respect to a pair of elements is introduced. A structure theorem namely,
`A finite lattice is dismantlable if and only if it is an adjunct of chains' is obtained. Further it is established that for
any adjunct representation of a dismantlable lattice the number of chains as well as the number of times a pair of elements
occurs remains the same. If a dismantlable lattice L has n elements and n+k edges then it is proved that the number of irreducible elements of L lies between n-2k-2 and n-2. These results are used to enumerate the class of lattices with exactly two reducible elements, the class of lattices with
n elements and upto n+1 edges, and their subclasses of distributive lattices and modular lattices.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
84.
Aluminium doped and undoped CdS films are deposited on the glass substrates by chemical bath deposition technique. Their optical and transport properties are studied and the effect of dopant concentration on these properties is discussed at length. 相似文献
85.
Tai CL Hung MS Pawar VD Tseng SL Song JS Hsieh WP Chiu HH Wu HC Hsieh MT Kuo CW Hsieh CC Tsao JP Chao YS Shia KS 《Organic & biomolecular chemistry》2008,6(3):447-450
A novel class of (5-(pent-1-enyl)thiophen-2-yl)pyrazole antagonists was discovered, many of which exhibited potent CB1 activity and good CB1/2 selectivity, suggesting that along with a 1,3-transposition of the carbonyl of the pyrazole 3-carboxamide, bioisosteric replacement of the conventional pyrazole 5-aryl group with a thienyl ring substituted with an appropriate alkenyl moiety is viable. 相似文献
86.
Synthesis of highly functionalized 2(1H)-pyrazinone 3-carboxamide derivatives is reported. A one-pot, two-step process including the base-mediated reaction of N,N-disubstituted aminoacetonitrile derivatives 18 with 3,5-dihalo-2(1H)-pyrazinones 1 afforded substituted aminoacetonitrile pyrazinone derivative 19, which on subsequent oxidation followed by transamidation of the resulting intermediate with primary or secondary amines gave the corresponding highly functionalized 2(1H)-pyrazinone 3-carboxamide derivatives 21. 相似文献
87.
Sushama S. Kauthale Sunil U. Tekale Kavita M. Jadhav Rajendra P. Pawar 《Molecular diversity》2016,20(3):763-770
An ethylene glycol promoted catalyst-free practically efficient and sustainable approach has been developed for the synthesis of several benzylidene-bis-(4-hydroxycoumarin)s and 4,\(4^{\prime }\)-(arylmethylene)-bis(3-methyl-1-phenyl-1H-pyrazol-5-ol)s by the pseudo three-component reaction of an aldehyde with 4-hydroxycoumarin and 3-methyl-1-phenylpyrazol-5-one, respectively. Inexpensive, non-toxic, and easily available ethylene glycol used as the reaction solvent and promoter renders an efficient protocol in terms of catalyst-free reaction conditions, short reaction time, high yield, practical utility, and green approach. 相似文献
88.
Hoodia gordonii, family Asclepiadaceae, is a succulent plant and is traditionally used in southern Africa for its appetite-suppressant properties. A high-performance liquid chromatographic (HPLC) method with UV detection for analysis of 11 oxypregnane glycosides from H. gordonii has been developed. The simultaneous analysis of 11 oxypregnane glycosides was achieved with a Phenomenex (Torrance, CA) reversed-phase C18 column using gradient mobile phase of water and acetonitrile, both containing 0.025% trifluoroacetic acid. The developed method was applied to the identification of oxypregnane glycosides in 3 different species of Hoodia and 23 related genera. The HPLC profiles of various plant samples were compared for the presence of oxypregnane glycosides. 相似文献
89.
Pawar Rupali R. Suryavanshi Vishal J. Salunkhe Suresh T. Patil Suresh S. Mulik Ganpatrao N. 《Journal of Radioanalytical and Nuclear Chemistry》2017,311(1):419-426
The extraction behavior of thorium(IV) from sulphuric acid medium with N-n-heptylaniline in xylene. Various parameters like reagent concentration, acid concentration, equilibration time, diverse ions and effect of diluents were studied. Thorium(IV) was selectively extracted and separated from many metal ions. The nature of the extracted species was determined. Thorium(IV) was analyzed from monazite ore and gas mantle.
相似文献90.
Diversity in Gold‐Catalyzed Formal Cycloadditions of Ynamides with Azidoalkenes or 2H‐Azirines: [3+2] versus [4+3] Cycloadditions
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Samir Kundlik Pawar Rajkumar Lalji Sahani Prof. Dr. Rai‐Shung Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(30):10843-10850
Gold‐catalyzed cycloadditions of ynamides with azidoalkenes or 2H‐azirines give [3+2] or [4+3] formal cycloadducts of three classes. Cycloadditions of ynamides with 2H‐azirine species afford pyrrole products with two regioselectivities when the Cβ‐substituted 2H‐azirine is replaced from an alkyl (or hydrogen) with an ester group. For ynamides substituted with an electron‐rich phenyl group, their reactions with azidoalkenes proceed through novel [4+3] cycloadditions to deliver 1H‐benzo[d]azepine products instead. 相似文献