全文获取类型
收费全文 | 1221篇 |
免费 | 42篇 |
国内免费 | 6篇 |
专业分类
化学 | 925篇 |
晶体学 | 10篇 |
力学 | 39篇 |
数学 | 51篇 |
物理学 | 244篇 |
出版年
2023年 | 10篇 |
2022年 | 38篇 |
2021年 | 27篇 |
2020年 | 36篇 |
2019年 | 40篇 |
2018年 | 42篇 |
2017年 | 58篇 |
2016年 | 46篇 |
2015年 | 42篇 |
2014年 | 42篇 |
2013年 | 112篇 |
2012年 | 86篇 |
2011年 | 101篇 |
2010年 | 42篇 |
2009年 | 43篇 |
2008年 | 40篇 |
2007年 | 53篇 |
2006年 | 44篇 |
2005年 | 33篇 |
2004年 | 30篇 |
2003年 | 15篇 |
2002年 | 23篇 |
2001年 | 8篇 |
2000年 | 14篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有1269条查询结果,搜索用时 15 毫秒
151.
S. F. Patil R. M. Patil M. Mudaliar 《Journal of Radioanalytical and Nuclear Chemistry》1990,139(2):323-329
The -radiolysis of IO
4
–
in aqueous solution and binary solutions containing iso-propanol has been studied as a function of reactant concentration and absorbed dose. The disappearance of periodate ion in the presence of alcohol is found to be higher as compared to that observed in the pure system. The trend in the G-values determined at various combinations of the reactant concentrations suggests the occurrence of a chain reaction in the radiolytic process. 相似文献
152.
V.S. Patil R.G. Pillay A.K. Grover P.N. Tandon H.G. Devare 《Solid State Communications》1983,48(11):945-947
A ternary system consisting of Ru, Fe and Si is identified in which the hyperfine field at Fe is seen to evolve at a characteristic temperature, T1, far below the magnetic ordering temperature, Tm. It is speculated that the magnetic ordering at Tm is itinerant and T1 corresponds to the localization of the majority spin electrons at the Fe atoms. 相似文献
153.
The repetition rate capability of self-switched transversely excited atmosphere (TEA) CO2 laser was studied for different gas flow configurations. For an optimized gas flow configuration, repetitive operation was
achieved at a much smaller gas replenishment factor between two successive pulses when compared with repetitive systems energized
by conventional pulsers. 相似文献
154.
P.P. Hankare R.P. Patil U.B. Sankpal R. Sasikala I.S. Mulla 《Journal of magnetism and magnetic materials》2010,322(18):2629-9662
Nanocrystalline Li0.5Fe2.5−xCrxO4 (2.5≤x≥0) ferrites were prepared by a sol-gel autocombustion route. X-ray diffraction was employed to confirm the cubic spinel phase formation of the ferrites. The lattice parameter decreases with increase in Cr content. The saturation magnetization, coercivity and remanance were studied as a function of Cr content. The dielectric constant and dielectric loss were measured as a function of frequency in the frequency range 20 Hz-1 MHz. Frequency dependence of dielectric constant shows dielectric dispersion due to the Maxwell-Wagner type of interfacial polarization. In order to understand the conduction mechanism, complex impedance measurements were carried out. The substitution of chromium plays an important role in changing the dielectric and magnetic properties of lithium ferrites. 相似文献
155.
In this work, the evolution of Silicon Nanostructures with progressive annealing has been studied. Hot Wire CVD (HWCVD) process was used to deposit a SixNy/a-Si structure on an n-type 〈100〉 Silicon substrate with the Nitride acting as the buffer layer. The depositions were carried out at a low substrate temperature (250 °C) which is precisely why HWCVD was chosen over other processes for this work. The as-deposited sample was then annealed at 800 °C and 900 °C respectively. AFM studies revealed promising results hinting at the presence of Silicon Nanostructures. With progressive annealing the Nanostructures began to evolve, eventually turning into sharp Nanopillars upon annealing at 900 °C. In this paper, a growth model has been proposed which attempts to validate the experimental results. Though a lot of work is currently underway in this field, study of Silicon Nanostructures grown by HWCVD technique is relatively new. 相似文献
156.
Yttrium oxide thin films are deposited by microwave electron cyclotron resonance (ECR) plasma assisted metal organic chemical vapour deposition process using an indegeneously developed Y(thd)3 {(2,2,6,6-tetramethyl-3,5-heptanedionate)yttrium} precursor. Depositions were carried out at two different argon gas flow rates keeping precursor and oxygen gas flow rate constant. The deposited coatings are characterized by X-ray photoelectron spectroscopy (XPS), glancing angle X-ray diffraction (GIXRD) and infrared spectroscopy. Optical properties of the films are studied by spectroscopic ellipsometry. Hardness and elastic modulus of the films are measured by load depth sensing nanoindentation technique. Stability of the film and its adhesion with the substrate is inferred from the nanoscratch test.It is shown here that, the change in the argon gas flow rates changes the ionization of the gas in the microwave ECR plasma and imposes a drastic change in the characteristics like composition, structure as well as mechanical properties of the deposited film. 相似文献
157.
Jawali C. Umavathi Hafiz Muhammad Ali Sapnali Limbaraj Patil 《Mathematical Methods in the Applied Sciences》2020,43(15):9223-9244
The motivation of the current article is to explore a numerical investigation on steady triply diffusive convection in a vertical channel. Heat is exchanged from the external fluid with the plates. The reference temperature is taken as equal and also as different for the external fluid. Solutions in the absence of viscous dissipation and buoyancy forces are also obtained as special cases. General solutions including the effects of viscous dissipation and buoyancy forces are obtained analytically using the method of perturbation. The analytical solutions can be used only if the Brinkman number is small. Hence to know the flow properties for all values of Brinkman number, we resort to numerical solutions. The effects of thermal Grashof number, solutal Grashof number, and the chemical reaction parameter on the flow field are evaluated numerically. The obtained results are validated against previously published results for special case of the problems. 相似文献
158.
Identification of energy-dissipation processes at the nanoscale is demonstrated by using amplitude-modulation atomic force microscopy. The variation of the energy dissipated on a surface by a vibrating tip as a function of its oscillation amplitude has a shape that singles out the dissipative process occurring at the surface. The method is illustrated by calculating the energy-dissipation curves for surface energy hysteresis, long-range interfacial interactions and viscoelasticity. The method remains valid with independency of the amount of dissipated energy per cycle, from 0.1 to 50 eV. The agreement obtained between theory and experiments performed on silicon and polystyrene validates the method. 相似文献
159.
Prins P Grozema FC Schins JM Patil S Scherf U Siebbeles LD 《Physical review letters》2006,96(14):146601
We have studied the high-frequency (34 GHz) mobility of positive charge carriers on isolated ladder-type polymer chains in dilute solution. We find that the high-frequency mobility is limited by the chain ends on chains as long as 35 monomers. The intrachain motion of charge carriers can be described by one-dimensional diffusion between infinitely high reflecting barriers, representing the chain ends. Our data indicate that the intrachain mobility for ladder-type polymer chains is close to 600 cm(2)/V s. With this high mobility the ladder-type polymer is a promising candidate for future use as an interconnecting wire in molecular electronics. 相似文献
160.
Laminar Heat Transfer Augmentation through A Square Duct and Circular Tube Fitted with Twisted Tapes
Experimental studies on friction factor and heat transfer characteristics for the laminar flow of ethylene glycol in a square duct fitted with twisted tapes of different twist ratios under nearly uniform wall temperature conditions are reported in this article. The Nusselt numbers were found to be 5.44–7.49 and 2.46–4.87 times that of plain square duct forced convection values based on constant flow rate and constant pumping power criteria, respectively, for y = 2.66. The augmented friction factor and Nusselt number for a square duct is about 1.9 and 2.10 times higher than that for an augmented circular tube. 相似文献