全文获取类型
收费全文 | 359篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
化学 | 166篇 |
晶体学 | 2篇 |
力学 | 28篇 |
数学 | 42篇 |
物理学 | 141篇 |
出版年
2023年 | 2篇 |
2022年 | 9篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 17篇 |
2013年 | 23篇 |
2012年 | 15篇 |
2011年 | 19篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 9篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 17篇 |
2003年 | 14篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
排序方式: 共有379条查询结果,搜索用时 406 毫秒
71.
O. A. Chuvenkova E. P. Domashevskaya S. V. Ryabtsev D. V. Vysotskii A. E. Popov Yu. A. Yurakov O. Yu. Vilkov R. Ovsyannikov N. Appathurai S. Yu. Turishchev 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2014,8(1):111-116
Wire-like micro- and nanocrystals of SnO2 are obtained via gas-transport synthesis. The specifics of the atomic and electronic structure of an array of SnO2 wire-like crystals is revealed using near-edge X-ray absorption and X-ray photoelectron spectra. The method of photoemission electron microscopy with high-intensity synchrotron (undulator) radiation is used to study the morphology of SnO2 wire-like crystals for the first time. 相似文献
72.
Marina Petrova Ruslan Muhamadejev Brigita Cekavicus Brigita Vigante Aiva Plotniece Arkadij Sobolev Gunars Duburs Edvards Liepinsh 《Heteroatom Chemistry》2014,25(2):114-126
A reaction of diethyl 2,4,6‐trimethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylate with 1, 2, and more equivalents of N‐bromosuccinimide (NBS) in methanol was investigated by NMR spectroscopy at a temperature interval ranging from 25 to 40°C. The reaction was found to proceed through several steps. The structures of the intermediates diethyl 3‐bromo‐2,4,6‐trimethyl‐3,4‐dihydropyridine‐3,5‐dicarboxylate, diethyl 3‐bromo‐2‐methoxy‐2,4,6‐trimethyl‐1,2,3,4‐tetrahydropyridine‐3,5‐dicarboxylate, and diethyl 3,5‐dibromo‐2‐methoxy‐2,4,6‐trimethyl‐2,3,4,5‐tetrahydropyridine‐3,5‐dicarboxylate were identified by multinuclear (1H, 13C, and 15N) NMR spectral data. The optimal structures of all species participating in the reaction as well as changes in their relative energies along with the proposed pathway of the reaction were analyzed by quantum‐chemical calculations. The mechanism of bromination of diethyl 2,4,6‐trimethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylate with NBS in methanol was found to favor the bromination in the 2,6‐methyl side chains as the only products in full agreement with experimental observations. 相似文献
73.
Dorofeeva VN Kolotilov SV Kiskin MA Polunin RA Dobrokhotova ZV Cador O Golhen S Ouahab L Eremenko IL Novotortsev VM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(16):5006-5012
Trinuclear building block {Fe(2)NiO(Piv)(6)} (Piv = pivalate), which possessed pseudo-D(3h) symmetry, was linked by two ligands, pseudo-D(3h) ligand tris-(4-pyridyl)pyridine (L1) and C(2v) ligand 4-(N,N-dimethylamino)phenyl-2,6-bis(4-pyridyl)pyridine (L2) into two products with different topologies: 2D coordination polymer [Fe(2)NiO(Piv)(6)(L1)](n) (1), and discrete molecule [{Fe(2)NiO(Piv)(6)}(8) {L2}(12)], which had a nanocube structure (2). In compound 1, trinuclear {Fe(2)NiO(Piv)(6)} blocks were linked through ligand L1 into layers with honeycomb topology. In compound 2, eight trinuclear blocks were located in the vertices of the nanocube, with each L2 ligand linked to two {Fe(2)NiO(Piv)(6)} units. In the crystal structure, these nanocubes formed infinite catenated chains. Analysis of possible structures that could be assembled from these building blocks showed that compounds 1 and 2 corresponded to their respective predicted topologies. Compound [1?solvent] possessed a porous structure, in which the voids were filled by solvent molecules (DMF or DMSO). This structure was retained following desolvation, and compound 1 absorbed significant quantities of N(2) and H(2) at 78?K (S(BET) = 730?m(2) g(-1), H(2) sorption capacity: 0.9?% by weight at 865?Torr). Desolvation of [2?solvent] led to disorder of its crystal structure, and compound 2 only adsorbed negligible quantities of N(2) but adsorbed 0.27?% H(2) (by weight) at 855?Torr and 78?K. The magnetic properties of these complexes (temperature dependence of molar magnetic susceptibility) were governed by the magnetic properties of the trinuclear "building block". 相似文献
74.
75.
Ruslan Sadykov 《Annals of Operations Research》2012,201(1):423-440
Cross docking terminals allow companies to reduce storage and transportation costs in a supply chain. At these terminals, products of different types from incoming trucks are unloaded, sorted, and loaded to outgoing trucks for delivery. If the designated outgoing truck is not immediately available for some products, they are temporarily stocked in a small storage area available at the terminal. This paper focuses on the operational activities at a cross docking terminal with two doors: one for incoming trucks and another one for outgoing trucks. We consider the truck scheduling problem with the objective to minimize the storage usage during the product transfer inside the terminal. Our interest in this problem is mainly theoretical. We show that it is NP-hard in the strong sense even if there are only two product types. For a special case with fixed subsequences of incoming and outgoing trucks, we propose a dynamic programming algorithm, which is the first polynomial algorithm for this case. The results of numerical tests of the algorithm on randomly generated instances are also presented. 相似文献
76.
A. M. Petrzhik V. V. Demidov G. A. Ovsyannikov I. V. Borisenko A. V. Shadrin 《Journal of Experimental and Theoretical Physics》2012,115(5):876-884
Magnetic bicrystal films and junctions of magnetic La0.67Sr0.33MnO3 (LSMO) and La0.67Ca0.33MnO3 (LCMO) films epitaxially grown on NdGaO3 substrates with the (110) planes of their two parts misoriented (tilted) at angles of 12°, 22°, 28°, and 38° are investigated. For comparison, bicrystal boundaries with a 90° misorientation of the axes of the NdGaO3 (110) planes were fabricated. The directions of the axes and the magnetic anisotropy constants of the films on both sides of the boundary are determined by two independent techniques of magnetic resonance spectroscopy. The magnetic misorientation of the axes in the substrate plane has been found to be much smaller than the crystallographic misorientation for tilted bicrystal boundaries, while the crystallographic and magnetic misorientation angles coincide for boundaries with rotation of the axes. An increase in the magnetoresistance and characteristic resistance of bicrystal junctions with increasing misorientation angle was observed experimentally. The magnetoresistance of bicrystal junctions has been calculated by taking into account the uniaxial anisotropy, which has allowed the contributions from the tunneling and anisotropic magnetoresistances to be separated. The largest tunneling magnetoresistance was observed on LCMO bicrystal junctions, in which the characteristic resistance of the boundary is higher than that in LSMO boundaries. 相似文献
77.
L. F. Atyaksheva I. V. Dobryakova I. I. Ivanova E. E. Knyazeva R. A. Ovsyannikov E. S. Chukhrai 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(3):468-474
The isotherms of hemoglobin adsorption on adsorbents of different nature and porous structure are obtained at different adsorption
times. The maximum adsorption values are determined, and the adsorption’s relationship with the adsorbent pore size is established.
The possibility of using hemoglobin as a test protein to determine the adsorbent surface area available for protein monolayer
formation is demonstrated. 相似文献
78.
The second harmonic in the dependence of a superconducting current on the phase difference of superconducting wave functions of the electrodes was observed experimentally in Nb/Au/(001)YBa2Cu3Ox heterojunctions. Possible reasons for its appearance were discussed within the framework of a mixed (d±s) symmetry order parameter of YBa2Cu3Ox. 相似文献
79.
Ruslan Bikmurzin Rimant Bandzevi
it Arnas Maralka Andrius Maneikis Lilija Kaldien 《Molecules (Basel, Switzerland)》2022,27(14)
β-glucans are known as biological response modifiers. However, different sources can result in structural differences and as a result differences in their biological activity. The hot water extraction method allows to obtain, high molecular weight β-glucans without altering their structure by using strong chemicals, such as alkalis or acids. Analysis of β-glucans by FT-IR and NMR spectroscopy in solid state is superior to analysis in solution as it allows researchers to study the preserved structure of the extracted polysaccharides. FT-IR spectroscopy was used in this study to make side-by-side comparison analysis of hot water extracted β-glucans from different yeast sources. NMR spectroscopy was used to confirm findings made by FT-IR spectroscopy. Extracted β-glucans exhibit characteristic structure of β-1,3/1,6-linked glucans with noticeable levels of proteins, possibly in a form of oligopeptides, chitin and other impurities. β-glucans obtained from C. guilliermondii, P. pastoris and S. pastorianus exhibited higher protein content. Differences in mannan, chitin and α-glucan content were also observed; however, the species-specific structure of obtained β-glucans could not be confirmed without additional studies. Structural analysis of high molecular weight β-glucans in solid state by FT-IR spectroscopy is difficult or limited due to band intensity changes and overlapping originating from different molecules. 相似文献
80.
The photooxidation of amines with triplet nitromethane has been studied using the uB3LYP/6-311g* method. The activation energies for hydrogen atom abstraction from ammonia and the amino group of methylamine or aniline have been found to be 14.1, 4.9, and 6.3 kJ mol?1, respectively. Details of the hydrogen atom transfer mechanism have been studied, the structures of transition complexes have been revealed, and noncovalent interaction energies have been evaluated in terms of the theory of atoms in molecules. 相似文献