全文获取类型
收费全文 | 544篇 |
免费 | 19篇 |
国内免费 | 4篇 |
学科分类
数理化 | 567篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 7篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 12篇 |
2017年 | 16篇 |
2016年 | 23篇 |
2015年 | 16篇 |
2014年 | 21篇 |
2013年 | 42篇 |
2012年 | 39篇 |
2011年 | 48篇 |
2010年 | 21篇 |
2009年 | 25篇 |
2008年 | 31篇 |
2007年 | 35篇 |
2006年 | 17篇 |
2005年 | 24篇 |
2004年 | 21篇 |
2003年 | 9篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 13篇 |
1998年 | 5篇 |
1997年 | 10篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1957年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有567条查询结果,搜索用时 328 毫秒
101.
102.
Vineeta Gautam Anchal Srivastava Karan Pratap Singh Vijay Laxmi Yadav 《Polymer Science Series A》2016,58(2):206-219
In this paper, we present a comparative study of polyaniline/polysaccharide composites (starch, carboxymethyl cellulose, cellulose acetate, and chitosan) by FTIR, UV-visible, SEM and electrochemical analysis. We propose that simultaneously three different phenomena happen while formation of composite system that may be listed as degradation of polysaccharide, polymerization of aniline, formation of polyaniline- polysaccharide composite. Effects of hydrochloric acid and oxidizing agent (ammonium peroxydisulphate) on the structure of polysaccharides were also investigated. We obtained dissimilar product yield and variable polyaniline and polysaccharide ratio in the composite system even though experimental conditions were same. The possible reasons responsible for the observed differences as well as characteristics and morphology of protonated and deprotonated composite materials are discussed. 相似文献
103.
This Technical Note presents the direct surface modification of a glass/PTFE hybrid microfluidic chip, via radio frequency glow discharge plasma polymerisation of tetraethlylene glycol dimethylether (tetraglyme), to produce hydrophilic, non-fouling, PEO-like surfaces. We use several techniques including X-ray photoelectron spectroscopy (XPS), direct enzyme-linked immunosorbent assays (ELISA) and immunofluorescent imaging to investigate the channel coatings. Our results indicate the successful deposition of a PEO-like coating onto microchannel surfaces that has both solution and shelf stability (>3 months) and is capable of preventing fibrinogen adsorption to the microchannel surfaces. 相似文献
104.
Sulekh?ChandraEmail author Archana?Gautam Monika?Tyagi 《Transition Metal Chemistry》2007,32(8):1079-1084
Cobalt(II), nickel(II) and copper(II) complexes are synthesized with 1,3,7,9-tetraaza- 4,6,10,12-tetraphenyl-2,8-dithiacyclododecane,
a tetradentate ligand (L) and characterized by elemental analysis, molar conductance measurements, magnetic susceptibitity
measurements, mass, i.r., electronic and e.p.r. spectral studies. All the complexes are non-electrolytes so they may be formulated
as [M(L)X2] [where, M = Co(II), Ni(II) and Cu(II) and X = Cl− and NO
3
−
]. All the complexes are of high spin type. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry
has been assigned for Co(II) and Ni(II) complexes and tetragonal geometry for Cu(II) complexes. The antimicrobial activities
of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against two different species of bacteria and plant pathogenic fungi. 相似文献
105.
Fang X Bando Y Ye C Shen G Gautam UK Tang C Golberg D 《Chemical communications (Cambridge, England)》2007,(40):4093-4095
Silicon nanowires assembled in micro-sized semispheres were synthesized through simple thermal evaporation without using any templates and metal particle catalysts; electron microscopy revealed that the nanowires within semisphere ensembles are well-aligned and evenly distributed; a typical nanowire array density was of approximately 4 x 10(9) cm(-2); field-emitting characteristics of the arrays were analyzed. 相似文献
106.
The diversity-oriented organic synthesis of enantiomerically pure benzannulated oxazepine, diazepine, thiazepine, oxazocine, and diazocine scaffolds is described from easily accessible naturally occurring S-amino acids as chiral synthons. Inter- and intramolecular Mitsunobu reactions for the formation of carbon-nitrogen, carbon-oxygen, and carbon-sulfur bonds have been used as key transformations to construct these biologically important privileged heterocycles. This is the first example where the Mitsunobu approach has been utilized for the construction of S-amino acid based seven- and eight-membered ring systems. 相似文献
107.
Delayed bifurcations and negative hysteresis in semiconductor lasers: the role of initial conditions
Seung-Ho Choi Erich White Donald M. Wood Tommy Dodson K. V. Vasavada Gautam Vemuri 《Optics Communications》1999,160(4-6):261-267
The dynamical intensity response of a semiconductor laser under the influence of injection current modulation, and the resulting hysteresis behavior, is investigated experimentally and theoretically. We report the first experimental observation, in a semiconductor laser, of the transition from a negative to a positive hysteresis as the modulation frequency of the injection current is varied. The theoretical work isolates the initial conditions on the intrinsic laser parameters as the sole determinant in influencing the kind of hysteresis one observes. 相似文献
108.
This report summarises the work done in the ‘Beyond the Standard Model’ working group of the Sixth Workshop on High Energy
Physics Phenomenology (WHEPP-6) held at the Institute of Mathematical Sciences, Chennai, Jan 3–15, 2000. The participants
in this working group were: R Adhikari, B Ananthanarayan, K P S Balaji, Gour Bhattacharya, Gautam Bhattacharyya, Chao-Hsi
Chang (Zhang). D Choudhury, Amitava Datta, Anindya Datta, Asesh K Datta, A Dighe, N Gaur, D Ghosh, A Goyal, K Kar, S F King,
Anirban Kundu, U Mahanta, R N Mohapatra, B Mukhopadhyaya, S Pakvasa, P N Pandita, M K Parida, P Poulose, G Raffelt, G Rajasekaran,
S Rakshit, Asim K Ray, A Raychaudhuri, S Raychaudhuri, D P Roy, P Roy, S Roy, K Sridhar and S Vempati. 相似文献
109.
Manjeet Singh Gautam 《理论物理通讯》2015,64(6):710-718
The present article highlights the inconsistency of static Woods-Saxon potential and the applicability of energy dependentWoods-Saxon potential to explore the fusion dynamics of 2248Ti+2858,60,64Ni, 2246Ti+2864Ni, 2250Ti+2860Ni, and 919F+4193Nb reactions leading to formation of different Sn-isotopes via different entrance channels. Theoretical calculations based upon one-dimensional Wong formula obtained by using static Woods-Saxon potential unable to provide proper explanation for sub-barrier fusion enhancement of these projectile-target combinations. However, the predictions of one- dimensional Wong formula based upon energy dependent Woods-Saxon potential model (EDWSP model) accurately describe the observed fusion dynamics of these systems wherein the significantly larger value of diffuseness parameter ranging from a = 0.85 fm to a = 0.97 fm is required to address the experimental data in whole range of energy. Therefore, the energy dependence in nucleus-nucleus potential simulates the influence of the nuclear structure degrees of freedom of the colliding pairs. 相似文献
110.
Gautam Bhattacharyya 《Pramana》2009,72(1):37-54
In this talk, I shall first discuss the Standard Model Higgs mechanism and then highlight some of its deficiencies making
a case for the need to go beyond the Standard Model (BSM). The BSM tour will be guided by symmetry arguments. I shall pick
up four specific BSM scenarios, namely, supersymmetry, little Higgs, gauge-Higgs unification, and the Higgsless approach.
The discussion will be confined mainly on their electroweak symmetry breaking aspects.
相似文献