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排序方式: 共有188条查询结果,搜索用时 15 毫秒
41.
Nicholas A. Barnes Stephen M. Godfrey Ruth T.A. Halton Imrana Mushtaq Simon Parsons Robin G. Pritchard Mark Sadler 《Polyhedron》2007
Structural and spectroscopic data on the series of compounds “PhSeX”, where X = Cl, CN or SCN, are reported and compared with previously reported data on “PhSeX” systems (X = Br and I). The chloro-compound displays a “square” motif, Ph4Se4Cl4, in the solid state, linked by long Se–Se bonds [2.993(3)–3.035(3) Å], and forms a loosely held network of Se4 and Cl4 squares in its extended structure. In contrast, the pseudohalogen derivatives, PhSeCN and PhSeSCN, consist of essentially monomeric units, which form chains held together by weak Se?N interactions in the solid state. These Se?N interactions are much shorter in PhSeCN, 3.023(3)–3.065(4) Å, than in PhSeSCN, 3.348(4) Å. Weaker Se?N contacts are also present between the chains. The structure of PhSeSCN described here is the first reported crystallographic study of a selenium thiocyanate compound. Spectroscopic studies suggest that all three compounds exist as monomers in solution. The results reported herein illustrate the subtle differences in the solid-state structures of PhSeX compounds. 相似文献
42.
43.
Mushtaq A. Dar Sang H. Nam Youn S. Kim Won Bae Kim 《Journal of Solid State Electrochemistry》2010,14(9):1719-1726
A simple hydrothermal process was used to synthesize the assembled leaf-like copper oxide (CuO) from copper hydroxide and
urea in aqueous solution. The field emission scanning electron microscopy revealed that the individual CuO leaf-like nanostructure
has a dimension of about 0.5–1.5 μm in length, 50–70 nm in thickness, and 80–110 nm in width, respectively. These CuO nanostructures
were structurally characterized by X-ray diffraction and Raman spectroscopy, which showed that the CuO nanostructures prepared
from the hydrothermal process have high crystalline properties with a monoclinic structure. X-ray photoelectron spectroscopy
studies confirmed that the as-prepared sample is composed of CuO, which is consistent with X-ray diffraction patterns. The
CuO nanostructures were used as electrode materials for lithium-ion batteries, demonstrating electrochemical properties of
a high initial discharge capacity of approximately 1,028 mAh/g along with good cycle stability. 相似文献
44.
Mahmood Z Azam M Mushtaq A Kausar R Kausar S Gilani SR 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,65(2):445-452
The infrared spectra of pure Mn(CO)(5)X in the region 4000-400 cm(-1) has been obtained in the vapour phase. The observed spectrum has been analyzed to distinguish the fundamental frequencies, the rotational-vibrational and structure, and overtone and combination frequencies. The assignment of the observed vapour phase frequencies to the fundamental modes of vibration has been made on C(4V) symmetry. The weak peaks due to XMn(CO)(4)((13)CO) molecules have been measured and assigned for all molecules. This study provides a comprehensive comparison of these compounds, with all of these data the assignment of frequencies is reviewed and a set of quite unambiguous assignments made. The significant finding in this regards are that, it is not necessary to assume lower than C(4V) symmetry for XMn(CO)(5) as has been done in previous consideration of some infrared spectrum of these compounds. 相似文献
45.
Tanveer Hussain Bokhari A. Mushtaq Islam Ullah Khan 《Journal of Radioanalytical and Nuclear Chemistry》2010,285(2):389-398
In this work, sorption of Ni(II) from aqueous solution to goethite as a function of various water quality parameters and temperature
was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic sorption well. The sorption
of Ni(II) to goethite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on Ni(II) sorption was found
at pH < 8.0, whereas a negative effect was observed at pH > 8.0. The Langmuir, Freundlich, and D-R models were applied to
simulate the sorption isotherms at three different temperatures of 293.15 K, 313.15 K and 333.15 K. The thermodynamic parameters
(ΔH
0, ΔS
0 and ΔG
0) were calculated from the temperature dependent sorption, and the results indicated that the sorption was endothermic and
spontaneous. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange with Na+/H+ on goethite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. 相似文献
46.
The kinetics of thermal dehydration of bis-(4-aminosalicylato)-diaquo complexes of VO(II), Cu(II), Ni(II), Co(II), Fe(II) and Mn(II), were studied. The activation energies and other kinetic parameters have been evaluated. The observed kinetic parameters indicate a first-order reaction. The activation energy of the thermal dehydration decreases in the order: VO(II) > Cu(II) > Co(II) > Ni(II) > Fe(II) > Mn(II), which is also the order for the covalency in the MO bonds. 相似文献
47.
48.
Structural determination of spin label immobilization and orientation: a Monte Carlo minimization approach 总被引:3,自引:0,他引:3
Sale K Sár C Sharp KA Hideg K Fajer PG 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2002,156(1):104-112
Electron paramagnetic resonance (EPR) is often used in the study of the orientation and dynamics of proteins. However, there are two major obstacles in the interpretation of EPR signals: (a) most spin labels are not fully immobilized by the protein, hence it is difficult to distinguish the mobility of the label with respect to the protein from the reorientation of the protein itself; (b) even in cases where the label is fully immobilized its orientation with respect to the protein is not known, which prevents interpretation of probe reorientation in terms of protein reorientation. We have developed a computational strategy for determining whether or not a spin label is immobilized and, if immobilized, predicting its conformation within the protein. The method uses a Monte Carlo minimization algorithm to search the conformational space of labels within known atomic level structures of proteins. To validate the method a series of spin labels of varying size and geometry were docked to sites on the myosin head catalytic and regulatory domains. The predicted immobilization and conformation compared well with the experimentally determined mobility and orientation of the label. Thus, probes can now be targeted to report on various modes of molecular dynamics: immobilized probes to report on protein backbone and domain dynamics or floppy probes to report on the extent of steric restriction experienced by the side chain. 相似文献
49.
A. Mushtaq Sh. Pervez I. Haider M. S. Mansur M. Jehangir 《Journal of Radioanalytical and Nuclear Chemistry》2000,243(3):827-829
99mTc pentavalent dimercaptosuccinic acid [99mTc(V) DMSA], a useful agent for imaging thyroid medullary carcinoma and other tumors can be reliably prepared by addition of Na99mTcO4 to a freeze-dried mixture of DMSA and Sn (2:1 molar ratio). The radiochemical purity, stability and animal bio-distribution behaviour is similar to that of the agent made by addition of NaHCO3 to DMSA (III) renal imaging freeze-dried kit. 相似文献