全文获取类型
收费全文 | 4185篇 |
免费 | 109篇 |
国内免费 | 10篇 |
专业分类
化学 | 3281篇 |
晶体学 | 116篇 |
力学 | 176篇 |
数学 | 208篇 |
物理学 | 523篇 |
出版年
2023年 | 25篇 |
2022年 | 49篇 |
2021年 | 56篇 |
2020年 | 73篇 |
2019年 | 94篇 |
2018年 | 98篇 |
2017年 | 76篇 |
2016年 | 128篇 |
2015年 | 91篇 |
2014年 | 174篇 |
2013年 | 443篇 |
2012年 | 269篇 |
2011年 | 246篇 |
2010年 | 151篇 |
2009年 | 143篇 |
2008年 | 234篇 |
2007年 | 218篇 |
2006年 | 162篇 |
2005年 | 160篇 |
2004年 | 150篇 |
2003年 | 138篇 |
2002年 | 112篇 |
2001年 | 42篇 |
2000年 | 47篇 |
1999年 | 35篇 |
1998年 | 23篇 |
1997年 | 28篇 |
1996年 | 42篇 |
1995年 | 25篇 |
1994年 | 32篇 |
1993年 | 31篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 40篇 |
1989年 | 31篇 |
1988年 | 29篇 |
1987年 | 34篇 |
1986年 | 31篇 |
1985年 | 40篇 |
1984年 | 47篇 |
1983年 | 38篇 |
1982年 | 29篇 |
1981年 | 31篇 |
1980年 | 32篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 27篇 |
1976年 | 20篇 |
1975年 | 21篇 |
1974年 | 21篇 |
排序方式: 共有4304条查询结果,搜索用时 0 毫秒
71.
Ch.V. Subba Reddy Edwin H. Walker Jr. S.A. Wicker Sr. Quinton L. Williams Rajamohan R. Kalluru 《Current Applied Physics》2009,9(6):1195-1198
Vanadium dioxide nanorods were synthesized through a hydrothermal reaction from V2O5 xerogel, poly(vinyl pyrrolidone) (PVP) and lithium perchlorate (LiClO4). The prepared samples were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical discharge–charge cycling in lithium battery. SEM images reveal the nanorods to have dimensions on the order of 1–3 μm in length and 10–50 nm in diameter. The measured initial discharge capacity of the lithium battery with a cathode made of VO2 (B) nanorods was 152 mA h/g. 相似文献
72.
T. V. M. Sreekanth S. Ramanaiah Kap Duk Lee K. S. Reddy 《Journal of Macromolecular Science: Physics》2013,52(6):1256-1266
The Flory–Huggins interaction parameters, for a solute with pure nonvolatile solvents and with binary mixtures of nonvolatile solvents were evaluated using Inverse Gas Chromatography (IGC) data at 403.15 K. The five solvents used have similar structure and nearly the same molar volume and their mixtures form regular solutions. The values were used to evaluate the Hansen solubility parameters (HSP) for the pure solvents and mixed solvent systems. The HSP are plotted as a function of composition of the polar solvent. The dispersion component, , and the polar component, , exhibited negative deviation whereas the hydrogen bonding component, , showed positive deviation in the four mixtures. However, the total solubility parameter was found to be almost linear with composition in the four binary systems. Further the total solubility parameter, , was used to calculate the molar excess heat of vaporization for the solvents (C78 + POH, C78 + PCN, C78 + TTF, and C78 + TMO) that was found to be negative for C78 (19,24-dioctadecyldotetracontane) + POH(18,23-dioctadecylhentetracontan-1-ol) and C78 + PCN(1-cyano-18,23-dioctadecylhentetracontane) systems and positive for C78 + TTF [19,24-bis(18,18,18-trifluorooctadecyl)-1,1,1,42,42,42-hexafluorodotetracontane), and C78 + TMO(17,22-bis-(16-methoxyhexadecyl)-1,38-dimethoxyoctatriacontane] and the other systems. 相似文献
73.
T.G.V.M. RaoA. Rupesh Kumar Ch. Kalyan ChakravarthiM. Rami Reddy N. Veeraiah 《Physica B: Condensed Matter》2012,407(4):593-597
Homogeneous 40.0 MgO-(10-x) PbF2-50.0 SiO2: x CuO glasses were prepared using melt-quenching technique under controlled conditions. Spectroscopic studies (UV-vis absorption, ESR, FT-IR) are carried out for these glasses. One broad characteristic visible absorption band is observed around 700-850 nm in these glasses, the optical band gap decreases as the content of the CuO increases in the glass network up to 0.7 mol % then reversal trend is observed. ESR spectra of all these glasses show resonance peaks characteristic of Cu2+ ions and hyperfine splitting is resolved with increasing the CuO content in the glass network. From the observed ESR spectra, the spin-Hamiltonian parameters have been evaluated and indicate that Cu2+ ions have octahedral coordination with a strong tetragonal distortion in these glasses. By correlating ESR and optical absorption data, the molecular orbital coefficients have been evaluated. FT-IR spectra give important information about the nature of bonds in the glass matrix. The density of the glasses is also measured and is found to decrease with the increase CuO contents in the glass matrix. The physical parameters along with spectroscopic parameters are measured. 相似文献
74.
Temperature-dependent (57)Fe M?ssbauer spectroscopy (5-723?K) and neutron diffraction (2-290?K) measurements are carried out on polycrystalline magnetoelectric GaFeO(3). From the neutron diffraction data, evidence for the magnetostriction and increased disorder at Fe sites close to the ferrimagnetic Curie transition temperature (T(C)) is observed. From the M?ssbauer data, it is observed that the Lamb-M?ssbauer factor as a function of temperature f(T), which is related to the integral over the first Brillouin zone of the phonon spectrum, shows a unequivocal variation at the T(C). The observations are discussed in terms of spin-phonon coupling. The observed average hyperfine fields from (57)Fe M?ssbauer spectra match with the bulk magnetization data. A critical exponent (β) of 0.38?±?0.02 and a Debye temperature (θ(D)) of ~350?K is estimated from the (57)Fe M?ssbauer data. 相似文献
75.
G. Murali D. Amaranatha Reddy B. PoornaPrakash R.P. Vijayalakshmi B.K. Reddy R. Venugopal 《Physica B: Condensed Matter》2012,407(12):2084-2088
Undoped and Fe doped CdS nanocrystals with Fe content of 2–5 at% of average crystallite size 1.2–2 nm have been obtained using chemical co-precipitation method with 2-mercaptoethonal as capping agent at 80 °C. X-ray diffraction (XRD) results showed that the undoped CdS nanocrystals were in mixed phase of cubic and hexagonal, where as the doped CdS nanocrystals were in hexagonal phase. Room-temperature ferromagnetism has been observed in Fe-doped CdS nanocrystals. Magnetic studies indicated diamagnetism in undoped, ferromagnetism in lightly doped (2 and 3 at%) and paramagnetism in samples of higher Fe content (4 and 5 at%). The substitutional incorporation of Fe3+ ion in Cd2+ sites was reflected in structural and electron paramagnetic resonance (EPR) measurements. Isolated as well as interacting Fe3+ ions are observed in EPR. 相似文献
76.
K. Premchand B. Seetharami Reddy B. Mallikarjuna Rao K. Parthasaradhi M. V. R. Murti K. S. Rao 《Il Nuovo Cimento D》1993,15(1):73-76
Summary An attempt is made to study theK
α
L
1 satellite multiplet structure of chlorine atoms in different compounds by photon excitation. A comparison of the averageK
α
L
1 group energy shift from the diagram line with those based on Dirac-Fock evaluations with different number ofM-shell electrons shows a reasonable agreement. The
intensity ratios are found to be higher than those studied in Mg compounds in general. 相似文献
77.
78.
Subba Reddy ChV Jin AP Zhu QY Mai LQ Chen W 《The European physical journal. E, Soft matter》2006,19(4):471-476
A sodium ion-conducting polymer electrolyte based on polyvinyl pyrrolidone (PVP) complexed with NaClO4 was prepared using the solution-cast technique. The cathode film of V2O5 xerogel modified with polyvinyl pyrrolidone was prepared using the sol-gel method. Investigations were conducted using X-ray
diffractometry (XRD), Fourier transformation infrared (FT-IR) spectroscopy. The ionic conductivity and transference number
measurements were performed to characterize the polymer electrolyte for battery applications. The transference number data
indicated that the conducting species in these electrolytes are the anions. Using the electrolyte, electrochemical cells with
a configuration Na/(PVP + NaClO4)/V2O5 modified by (PVP) were fabricated and their discharge profiles studied. 相似文献
79.
M. Srinivasa Reddy 《Journal of Physics and Chemistry of Solids》2006,67(4):789-795
ZnO-Sb2O3-B2O3 glasses containing different concentrations of MnO ranging from 0 to 1.0 mol% were prepared. A number of studies, viz. optical absorption, infrared and ESR spectra and magnetic susceptibility, were carried out as a function of manganese ion concentration. The analysis of the results indicate that manganese ions mostly exist in Mn2+ state in these glasses when the concentration of MnO≤0.6 mol% and above this concentration, these ions seem to exist in Mn3+ state in the glass network. 相似文献
80.
Renata Monteiro-Maia Maria B Ortigão-de-Sampaio Rosa T Pinho Luiz RR Castello-Branco 《Journal of immune based therapies and vaccines》2006,4(1):1-6
We hypothesize that the energy strategy of a cell is a key factor for determining how, or if, the immune system interacts
with that cell. Cells have a limited number of metabolic states, in part, depending on the type of fuels the cell consumes.
Cellular fuels include glucose (carbohydrates), lipids (fats), and proteins. We propose that the cell's ability to switch
to, and efficiently use, fat for fuel confers immune privilege. Additionally, because uncoupling proteins are involved in
the fat burning process and reportedly in protection from free radicals, we hypothesize that uncoupling proteins play an important
role in immune privilege. Thus, changes in metabolism (caused by oxidative stresses, fuel availability, age, hormones, radiation,
or drugs) will dictate and initiate changes in immune recognition and in the nature of the immune response. This has profound
implications for controlling the symptoms of autoimmune diseases, for preventing graft rejection, and for targeting tumor
cells for destruction. 相似文献