全文获取类型
收费全文 | 615篇 |
免费 | 18篇 |
国内免费 | 3篇 |
专业分类
化学 | 302篇 |
晶体学 | 10篇 |
力学 | 8篇 |
数学 | 38篇 |
物理学 | 278篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 16篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 15篇 |
2015年 | 10篇 |
2014年 | 20篇 |
2013年 | 53篇 |
2012年 | 28篇 |
2011年 | 44篇 |
2010年 | 18篇 |
2009年 | 29篇 |
2008年 | 26篇 |
2007年 | 28篇 |
2006年 | 26篇 |
2005年 | 25篇 |
2004年 | 13篇 |
2003年 | 9篇 |
2002年 | 18篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 17篇 |
1995年 | 17篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 13篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 15篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 7篇 |
1978年 | 8篇 |
1977年 | 2篇 |
1975年 | 4篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1938年 | 2篇 |
排序方式: 共有636条查询结果,搜索用时 15 毫秒
111.
Effects of Hall current on a steady hydromagnetic (MHD) fully developed flow in a rotating environment within a parallel plate
channel in the presence of an inclined magnetic field is studied. From an extension of literature [13] subject to a forced
oscillation it is observed that the present paper is methodically more correct to work first in the steady state where forced
oscillation becomes insignificant and then new results are expected for an unsteady MHD flow under the influence of a pulse-oscillator.
Exact solutions of the governing equations are obtained in a closed form. The graphical representation for the velocity and
the induced magnetic field are depicted graphically and the heat transfer at both the plates are presented in tables. 相似文献
112.
Growth of Ag islands under ultrahigh vacuum condition on air-exposed Si(0 0 1)-(2 × 1) surfaces has been investigated by in-situ reflection high energy electron diffraction (RHEED). A thin oxide is formed on Si via exposure of the clean Si(0 0 1)-(2 × 1) surface to air. Deposition of Ag on this oxidized surface was carried out at different substrate temperatures. Deposition at room temperature leads to the growth of randomly oriented Ag islands while well-oriented Ag islands, with (0 0 1)Ag||(0 0 1)Si, [1 1 0]Ag||[1 1 0]Si, have been found to grow at substrate temperatures of ≥350 °C in spite of the presence of the oxide layer between Ag islands and Si. The RHEED patterns show similarities with the case of Ag deposition on H-passivated Si(0 0 1) surfaces. 相似文献
113.
Srinivasa Rao Karumuri Nirmal Kumar Sarkar Ramendu Bhattacharjee 《Journal of Molecular Spectroscopy》2009,255(2):183-104
In this paper the highly excited stretching and bending vibrational energy levels of some Nickel Metalloporphyrin molecules are studied by U (2) algebraic model. Its application to Nickel Octaethyl Porphyrin, Nickel Tetra Phenyl Porphyrin and Nickel Porphyrin are presented with fewer algebraic fitting parameters. The highly excited stretching and bending vibrational energy levels of these molecules are showing the energy clustering spectrum. 相似文献
114.
Conductivities of some tetraalkylammonium halides, viz. tetrabutylammonium bromide (Bu4NBr), tetrapentylammonium bromide (Pen4NBr), tetrahexylammonium bromide (Hex4NBr) and tetraheptylammonium bromide (Hep4NBr) were measured at 298.15 K in THF + C6H6 mixtures with 10, 20, 30 and 40 mass% of C6H6. A minimum in the conductance values was observed as concentration increases, which dependent both on the salt and the solvent. The observed molar conductivities were explained by the formation of ion-pairs (M+ + X− ↔ MX, KP) and triple-ions (2 M+ + X− ↔ M2X+; M+ + 2X− ↔ MX2−, KT). A linear relationship between the triple-ion formation constants [log(KT/KP)] and the salt concentrations at the minimum conductivity (log Cmin) was given for all salts in C6H6 + THF mixtures. The formation of triple-ions might be attributed to the ion sizes in solutions in which coulombic interactions and covalent bonding forces act as the main forces between the ions (R4N+ X−). 相似文献
115.
Rashid H Bhattacharjee RR Kotal A Mandal TK 《Langmuir : the ACS journal of surfaces and colloids》2006,22(17):7141-7143
A simple and easier chemical method for preparing spongy gold nanocrystals has been developed on the basis of a modified-citrate reduction technique of the corresponding gold salt at 25 degrees C in the absence of template. These nanocrystals possessed autocatalytic behavior and exhibited pronounced catalytic activity in the borohydride reduction of 4-nitrophenol due to their unique spongy morphology. 相似文献
116.
Nazemifard N Masliyah JH Bhattacharjee S 《Langmuir : the ACS journal of surfaces and colloids》2006,22(24):9879-9893
The role of surface charge heterogeneity of planar collectors on particle deposition and distribution was investigated in the vicinity of a heterogeneous surface for a radial impinging jet flow geometry. The charge heterogeneity was modeled as concentric circular stripes bearing different surface charges. Particle deposition was studied employing the Eulerian approach (convection-diffusion-migration equation). It was observed that when the collector was completely unfavorable, the presence of small amounts of charge heterogeneity in the form of a small fraction of favorably charged stripes enhanced the deposition rate substantially. In contrast, when the collector was completely favorable, the presence of small amounts of charge heterogeneity in the form of a small fraction of unfavorably charged stripes did not affect the particle deposition rate significantly. 相似文献
117.
Plaban Jyoti Sarma Debojyoti Bhattacharjee Bhupesh Kumar Mishra 《Molecular physics》2017,115(8):962-970
Dual level of quantum mechanical calculations have been carried out for hydrogen abstraction from Piperazine [HN(CH2CH2)2NH] initiated by OH radical. Geometry optimisation and frequency calculations of all species involved in the titled reaction have been performed at M06-2X/6-31+G(d,p) level of theory. For the accuracy in the thermochemistry and kinetics data, single-point energy calculations have been further carried out at coupled cluster CCSD(T) method along with 6-311G(d,p) basis set. An energy profile diagram for the reaction has been plotted along with pre-reactive and post-reactive complexes at entrance and exit channels. Intrinsic reaction coordinates (IRCs) calculations have been performed for identification of real transition states that connect it via reactant to product. Our result shows that the H-atom abstraction takes place from the C–H position of Piperazine. The rate constant is calculated using canonical transition state theory (CTST) is found to be 2.86 × 10?10 cm3 molecule?1 s?1 which is in good agreement with the reported experimental rate constant (2.38 ± 0.28) × 10?10 cm3 molecule?1 s?1 at 298 K. We have also reported rate constant for the temperature range 300–500 K. Using group-balance isodesmic reaction, the standard enthalpies of formation for Piperazine and product radicals generated by hydrogen abstraction are reported. The branching ratios for both reaction channel (i.e. H-abstraction from –CH2 and –NH position of Piperazine) are found to be 93% and 7%, respectively. The calculated atmospheric life time of Piperazine is found to be 0.97 hour. 相似文献
118.
This paper deals with the application of Huygens’ wave theory of light for the derivation of the generalized vectorial laws of reflection and refraction discovered by the author in 2005. The long-running literature falls short of such a theoretical proof of the generalized vectorial laws of reflection and refraction on the basis of wave theory. As such the present work is novel and original. At the same time it also enhances the theoretical foundation of the discovery of the generalized vectorial laws of reflection and refraction there by proving the efficiency and increasing the range of applicability of the wave theory of light as well. 相似文献
119.
120.
Bhattacharjee S Dong J Ma Y Hovde S Geiger JH Baker GL Bruening ML 《Langmuir : the ACS journal of surfaces and colloids》2012,28(17):6885-6892
Layer-by-layer polyelectrolyte adsorption is a simple, convenient method for introducing ion-exchange sites in porous membranes. This study demonstrates that adsorption of poly(acrylic acid) (PAA)-containing films at pH 3 rather than pH 5 increases the protein-binding capacity of such polyelectrolyte-modified membranes 3-6-fold. The low adsorption pH generates a high density of -COOH groups that function as either ion-exchange sites or points for covalent immobilization of metal-ion complexes that selectively bind tagged proteins. When functionalized with nitrilotriacetate (NTA)-Ni(2+) complexes, membranes containing PAA/polyethylenimine (PEI)/PAA films bind 93 mg of histidine(6)-tagged (His-tagged) ubiquitin per cm(3) of membrane. Additionally these membranes isolate His-tagged COP9 signalosome complex subunit 8 from cell extracts and show >90% recovery of His-tagged ubiquitin. Although modification with polyelectrolyte films occurs by simply passing polyelectrolyte solutions through the membrane for as little as 5 min, with low-pH deposition the protein binding capacities of such membranes are as high as for membranes modified with polymer brushes and 2-3-fold higher than for commercially available immobilized metal affinity chromatography (IMAC) resins. Moreover, the buffer permeabilities of polyelectrolyte-modified membranes that bind His-tagged protein are ~30% of the corresponding permeabilities of unmodified membranes, so protein capture can occur rapidly with low-pressure drops. Even at a solution linear velocity of 570 cm/h, membranes modified with PAA/PEI/PAA exhibit a lysozyme dynamic binding capacity (capacity at 10% breakthrough) of ~40 mg/cm(3). Preliminary studies suggest that these membranes are stable under depyrogenation conditions (1 M NaOH). 相似文献