全文获取类型
收费全文 | 763篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
化学 | 400篇 |
晶体学 | 3篇 |
力学 | 54篇 |
数学 | 70篇 |
物理学 | 250篇 |
出版年
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2018年 | 12篇 |
2017年 | 18篇 |
2016年 | 22篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 64篇 |
2012年 | 35篇 |
2011年 | 26篇 |
2010年 | 35篇 |
2009年 | 25篇 |
2008年 | 28篇 |
2007年 | 35篇 |
2006年 | 32篇 |
2005年 | 29篇 |
2004年 | 26篇 |
2003年 | 8篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 11篇 |
1976年 | 10篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1971年 | 5篇 |
1962年 | 5篇 |
排序方式: 共有777条查询结果,搜索用时 15 毫秒
101.
B.K. Agrawal Savitri Agrawal 《Physica E: Low-dimensional Systems and Nanostructures》2005,30(1-2):7-12
An ab-initio study of the effects of the quantum confinement has been performed for the first time in the ultrathin ZnS films: unpassivated, passivated and the Mn-doped ones. A self-consistent full potential linear muffin tin orbital (FP-LMTO) method has been employed. The studied films have comparatively a large thickness range of 2.7–29.7 Å. The fundamental band gap increases exponentially with decrease in the size of the quantum confinement. The Mn-doped films reveal the localized impurity-induced states within the band gap and also in the conduction band region. The intense optical transitions between the Mn-induced states will appear at about 2.1 eV which is in excellent agreement with the observed peak in the photoluminescence experiments. 相似文献
102.
Conclusions From the study, it is observed that introduction of swirl in the central jet enhances the merger whereas higher swirl in the annulus enhances both mixing and flow development. On qualitative comparison with similar works (Gouldin et al. 1985; Ramos and Sommer 1983) it is seen that imposition of pressure gradient in form of expanded confinement enhances the capability of formation of central recirculation core. Wall static pressure distribution also gives an indication of the wall recirculation size. 相似文献
103.
Govind P. Agrawal 《Optics Communications》1982,42(5):366-370
Phase conjugation through four-wave mixing is considered in a two-photon resonant medium pumped by two distinct-frequency counter-propagating beams. This configuration eliminates the formation of stationary spatial holes. The relative magnitude of the pump intensities plays an important role and the phase-conjugation efficiency is found to be maximum for unequal values of the pump intensities. 相似文献
104.
Ashcroft’s analytic bare ion pseudopotential form factor with a modified Hartree dielectric function has been employed to
represent the temperature dependent interionic potential. This potential includes both direct ion-ion interaction and indirect
ion-electron-ion interaction with and without the effects of ‘d’ bands, in some scantily studied complexbcc metals vizbcc Ti, Zr and Hf. The ab initio radial and tangential force constants extending out to 15th nearest neighbours are computed
for the metals. The said potential is used for predicting the binding energy, elastic constants and phonon dispersion of the
above mentioned metals and the results are satisfactorily compared with the corresponding measured data. 相似文献
105.
Propagation of two-copropagating or counterpropagating beams is considered in a slab of nonlinear dielectric which is in two-photon resonance with respect to the sum of the laser frequencies. The effects of saturated absorption and dispersion of the beam intensities are studied in detail. The slab transmission is shown to be significantly affected by the induced optical Stark-shift. 相似文献
106.
Bal.K. Agrawal 《Solid State Communications》1981,37(3):271-274
A five-atom cluster Bethe lattice method treating the short-range order with proper statistical effects has been proposed for understanding the crystalline and amorphous alloys. Numerical results for Ge1?xSix alloys are in excellent agreement with the experimental data. In the system studied the network is random but the nearest-neighbour coordination should be treated exactly. The long-range coordination is seen to be concentration-dependent in the crystalline alloys but concentration-independent in the amorphous alloys. 相似文献
107.
M. D. Agrawal C. S. Bhandari M. K. Dixit N. C. Sogani 《Monatshefte für Chemie / Chemical Monthly》1976,107(1):75-82
Stability constants of praseodymium chelates of 3,4,5-trihydroxy sodium benzoate are determined by using Bjerrum-Calvin pH titration technique at constant ionic strength 0.1M-sodium perchlorate and at 28±0.1°C. Values calculated by different methods are in good agreement. The study reveals that during complexation only one proton of the ligand molecule is replaced by the metal and oxygen of adjacent phenolic group acts as a coordinating atom. IR and NMR spectral studies of the ligand reveal that one of the OH groups (in meta position to carboxylic group) remains free while two other phenolic groups are involved in intramolecular hydrogen bonding. One water molecule is found attached in crystalline gallic acid.
Mit 2 Abbildungen 相似文献
Mit 2 Abbildungen 相似文献
108.
Condensation of bis(2-furanthiocarboxyhydradatometal(II), M(fth)2; [M (II) = Mn, Fe, Co, Ni, Cu and Zn] with pyridine-2- and -4-carboxaldehydes gave complexes of the formula M(pfth)2 [pfth? = pyridine-2-carboxaldehyde-2-furanthiocarboxyhydrazonato], Ni(Ifth)2, Zn(Ifth)2, Cu(Ifth) and Co(Ifth)3, (Ifth? = pyridine-4-carboxaldehyde-2-furanthiocarboxyhydrazonato). The magnetic and electronic spectral studies coupled with photoacoustic or Mössbauer spectra suggested octahedral geometry for the M(II) complexes with low-spin states for Co(Ifth)3 and Fe(pfth)2. IR and 1H NMR spectral studies of diamagnetic complexes suggested bonding through “azomethine” nitrogen and “thiolo” sulphur. IR spectra also showed the involvement of pyridine ring nitrogen in coordination in all the complexes except Cu(Itfh), Co(Ifth)3, and Zn(Ifth)2. Some of the compounds possessed antimicrobial activity. 相似文献
109.
K. G. Varshney A. Agrawal S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2007,90(3):721-724
Pyridine based thorium(IV) phosphate (PyThP) has been synthesized by drop-wise addition of the thorium(IV) nitrate with constant
stirring into a mixture of pyridine and phosphoric acid. This material has been characterized using X-ray, IR spectra, TG,
DTG and SEM studies in addition to its ion exchange capacity, elution and pH titrations. The material has been found amorphous
and fibrous in nature on the basis of X-ray diffraction and SEM studies. TG has revealed the changes incurred in the material
on thermal treatment and IR spectral studies have shown the presence of various groups in its structure. 相似文献
110.
G. P. Agrawal 《Optics & Laser Technology》1981,13(3):141-144
The atmospheric propagation of a sequence of short, intense laser pulses is considered. The pulses propagate in a self-induced low-density channel, the effectiveness of which depends on a set of three variables. Using a simple model for the laser-atmosphere interaction, the range of successive pulses is determined by numerical solutions to the paraxial wave equation. The dependence of the length, width, and depth of the created channel on the important variables is explored. 相似文献