全文获取类型
收费全文 | 340篇 |
免费 | 10篇 |
国内免费 | 4篇 |
专业分类
化学 | 254篇 |
晶体学 | 1篇 |
力学 | 13篇 |
数学 | 12篇 |
物理学 | 74篇 |
出版年
2024年 | 1篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 11篇 |
2013年 | 9篇 |
2012年 | 24篇 |
2011年 | 21篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 24篇 |
2007年 | 31篇 |
2006年 | 33篇 |
2005年 | 25篇 |
2004年 | 14篇 |
2003年 | 27篇 |
2002年 | 13篇 |
2001年 | 20篇 |
2000年 | 16篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有354条查询结果,搜索用时 972 毫秒
21.
The π‐Back‐Bonding Modulation and Its Impact in the Electronic Properties of CuII Antineoplastic Compounds: An Experimental and Theoretical Study 下载免费PDF全文
Juan Carlos García‐Ramos Dr. Rodrigo Galindo‐Murillo Araceli Tovar‐Tovar Ana Luisa Alonso‐Saenz Virginia Gómez‐Vidales Dr. Marcos Flores‐Álamo Dr. Luis Ortiz‐Frade Dr. Fernando Cortes‐Guzmán Dr. Rafael Moreno‐Esparza Prof. Antonio Campero Prof. Lena Ruiz‐Azuara 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(42):13730-13741
22.
23.
Ederley Vélez Jairo Quijano Rafael Notario Elizabeth Pabón Juliana Murillo Julieth Leal Edilma Zapata Gustavo Alarcón 《Journal of Physical Organic Chemistry》2009,22(10):971-977
This paper reports a theoretical study, at the B3LYP/6–31 + G(d,p) and M05‐2X/6–31G + (d,p) levels, on the thermal decomposition of menthyl benzoate (2‐isopropyl‐5‐methylcyclohexyl benzoate). It undergoes a unimolecular first‐order elimination to give 3‐menthene (1‐isopropyl‐4‐methylcyclohexene), 2‐menthene (3‐isopropyl‐6‐methylcyclohexene), and benzoic acid. We studied two possible mechanisms trying to explain the formation of 2‐ and 3‐menthene, via six‐membered or four‐membered cyclic transition states. Rate constants were calculated at two temperatures, 587.1 and 598.6 K, and they agree well with the experimentally determined values. We verify that 3‐menthene is the product mainly formed at both temperatures. The progress of the reactions has been followed by means of the Wiberg bond indices. Intrinsic reaction coordinate (IRC) calculations have been carried out to verify that the localized transition state structures connect with the reactants and products and also to verify that the parent compound, menthyl benzoate, is taking the cis‐configuration needed in the reaction. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
24.
The use of optic microscopy and scanning electron microscopy propitiated the comparative examination of the structure of the proventriculus bulb of Cephalotes atratus, Cephalotes clypeatus and Cephalotes pusillus. This portion of the digestive tract possesses highly sclerotized projections which act in the selection of victuals. This structure is of importance to phylogeny studies and thus was compared with others known species of ants in a dendrogram adapted from Eisner (1957). We did not detect differences among the three studied species in the nature of histochemistry and ultra morphology. 相似文献
25.
We consider the deterministic generation of entangled multiqubit states by the sequential coupling of an ancillary system to initially uncorrelated qubits. We characterize all achievable states in terms of classes of matrix-product states and give a recipe for the generation on demand of any multiqubit state. The proposed methods are suitable for any sequential generation scheme, though we focus on streams of single-photon time-bin qubits emitted by an atom coupled to an optical cavity. We show, in particular, how to generate familiar quantum information states such as W, Greenberger-Horne-Zeilinger, and cluster states within such a framework. 相似文献
26.
Cotton FA Liu CY Murillo CA Villagrán D Wang X 《Journal of the American Chemical Society》2004,126(45):14822-14831
Very strong electronic communication, manifested in a K(C) value of ca. 10(9), has been found in a system of three compounds separated by one electron oxidation where each compound contains two metal-metal bonded Mo(2)(n+) units linked by a dimethyloxamidate anion, CH(3)N(O)C-C(O)NCH(3)(2)(-). The Mo-Mo distances increase as the oxidation state increases and the bond order decreases, while the diamagnetic, doubly oxidized species becomes essentially planar and resembles a naphthalene molecule. Calculations at the DFT level indicate that a strong transition in the near-IR region, shown by the singly oxidized and paramagnetic species, is best described as a HOMO-1 --> SOMO transition. 相似文献
27.
Use of an ionic liquid in a two-phase system to improve an alcohol dehydrogenase catalysed reduction 总被引:5,自引:0,他引:5
Eckstein M Villela Filho M Liese A Kragl U 《Chemical communications (Cambridge, England)》2004,(9):1084-1085
Due to favourable partition coefficients the highly enantioselective reduction of 2-octanone, catalysed by an alcohol dehydrogenase from Lactobacillus brevis, is faster in a biphasic system containing buffer and the ionic liquid [BMIM][(CF(3)SO(2))(2)N] compared to the reduction in a biphasic system containing buffer and methyl tert-butyl ether. 相似文献
28.
Pichini S Pellegrini M Pacifici R Marchei E Murillo J Puig C Vall O García-Algar O 《Rapid communications in mass spectrometry : RCM》2003,17(17):1958-1964
A high-performance liquid chromatography (HPLC) method with mass spectrometric detection is described for determination of arecoline in newborn meconium, urine and cord serum, using pilocarpine as internal standard. The analytes were extracted from neonatal biological matrices with chloroform/isopropanol (95:5, v/v) at alkaline pH. Extracts were analyzed by HPLC coupled to an electrospray (ESI) interface and a quadrupole mass spectrometer. Chromatography was performed on a C(8) reversed-phase column using 10 mM ammonium acetate (pH 4.3)/acetonitrile (90:10, v/v) as mobile phase. The mass spectrometer was operated in selected ion monitoring mode. The method was validated over the concentration range 0.005-1.00 micro g/g meconium, 0.004-1.00 micro g/mL cord serum and 0.001-1.00 micro /mL urine. Mean recoveries ranged between 86.5 and 90.7% for arecoline in the different biological matrices, with precision always better than 10%. The quantification limits of arecoline were 0.005 micro g/g meconium, 0.004 micro g/mL cord serum, and 0.001 micro g/mL urine. The method was applied to the analysis of neonatal biological matrices to assess eventual fetal exposition to arecoline. Two newborns from Asian mothers who declared areca nut consumption presented arecoline in meconium with concentrations in the range 0.006-0.008 micro g/g; also the urine from one neonate tested positive for the drug. 相似文献
29.
30.
We propose a scheme for producing large Fock states in cavity QED via the implementation of a highly selective atom-field interaction. It is based on Raman excitation of a three-level atom by a classical field and a quantized field mode. Selectivity appears when one tunes to resonance a specific transition inside a chosen atom-field subspace, while other transitions remain dispersive, as a consequence of the field dependent electronic energy shifts. We show that this scheme can be also employed for reconstructing, in a new and efficient way, the Wigner function of the cavity field state. 相似文献