全文获取类型
收费全文 | 350篇 |
免费 | 16篇 |
专业分类
化学 | 276篇 |
力学 | 9篇 |
数学 | 35篇 |
物理学 | 46篇 |
出版年
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 17篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 11篇 |
2012年 | 26篇 |
2011年 | 22篇 |
2010年 | 14篇 |
2009年 | 19篇 |
2008年 | 12篇 |
2007年 | 16篇 |
2006年 | 16篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 2篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 13篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1973年 | 5篇 |
1968年 | 1篇 |
1967年 | 4篇 |
1906年 | 2篇 |
1905年 | 2篇 |
1904年 | 2篇 |
1880年 | 2篇 |
1869年 | 2篇 |
排序方式: 共有366条查询结果,搜索用时 312 毫秒
41.
F. Elias I. Drikis A. Cebers C. Flament J.-C. Bacri 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,3(2):203-209
Two-dimensional magnetic fluid foams are cellular structures whose framework is made of magnetic fluid. The features of these
equilibrated patterns are driven by a control parameter: the amplitude of the applied magnetic field. When the latter is rapidly
increased, an instability occurs: the walls between cells undulate. Such an instability has also been observed in other 2D
cellular structures, which exist for instance in Langmuir monolayers or in magnetic garnets thin films. In this paper we give
a theoretical analysis of this instability, the issues of which are shown to be well confirmed by experiments and numerical
simulations.
Received: 13 October 1997 / Received in final form: 28 January 1998 / Accepted: 9 March 1998 相似文献
42.
Esters containing tertiary amine functionalities were successfully synthesized under mild conditions and in good yields, using a three-step process involving the activation of acids into their corresponding cyanomethyl esters, followed by transesterification with the alcohol counterparts, and subsequent scavenging of the excess of alcohol to facilitate purification. 相似文献
43.
Camille Male 《Journal of Functional Analysis》2017,272(1):1-46
A heavy Wigner matrix is defined similarly to a classical Wigner one. It is Hermitian, with independent sub-diagonal entries. The diagonal entries and the non-diagonal entries are identically distributed. Nevertheless, the moments of the entries of tend to infinity with N, as for matrices with truncated heavy tailed entries or adjacency matrices of sparse Erdös–Rényi graphs. Consider a family of independent heavy Wigner matrices and an independent family of arbitrary random matrices with a bound condition and converging in ?-distribution in the sense of free probability. We characterize the possible limiting joint ?-distributions of , giving explicit formulas for joint ?-moments. We find that they depend on more than the ?-distribution of and that in general and are not asymptotically ?-free. We use the traffic distributions and the associated notion of independence [21] to encode the information on and describe the limiting ?-distribution of . We develop this approach for related models and give recurrence relations for the limiting ?-distribution of heavy Wigner and independent diagonal matrices. 相似文献
44.
Sensor networks are emerging as a paradigm for future computing, but pose a number of challenges in the fields of networking and distributed computation. One challenge is to devise a greedy routing protocol—one that routes messages through the network using only information available at a node or its neighbors. Modeling the connectivity graph of a sensor network as a 3-connected planar graph, we describe how to compute on the network in a distributed and local manner a special geometric embedding of the graph. This embedding supports a geometric routing protocol called “greedy routing” based on the “virtual” coordinates of the nodes derived from the embedding. 相似文献
45.
Yoboué A Susset A Tougerti A Gallego D Ramani SV Kalyanikar M Dolzhnikov DS Wubshet SG Wang Y Cristol S Briois V La Fontaine C Gauvin RM Paul JF Berrier E 《Chemical communications (Cambridge, England)》2011,47(14):4285-4287
Heterogeneous Re/SiO(2) catalysts prepared using a one pot sol-gel synthesis were found to display high activity in the direct, selective methanol conversion to methylal, which is correlated to an unprecedented rhenium oxide structure. 相似文献
46.
Nicolas Sbirrazzuoli Alice Mititelu-Mija Luc Vincent Camille Alzina 《Thermochimica Acta》2006,447(2):167-177
The curing reaction of stoichiometric and off-stoichiometric diglycidyl ether of bisphenol A (DGEBA) and 1,3-phenylene diamine (m-PDA) mixtures was studied by differential scanning calorimetry, thermogravimetric analysis and rheological measurements. In order to highlight the side reactions such as etherification and homopolymerization, the neat DGEBA and DGEBA/DMBA (N,N-dimethylbenzylamine) mixture were examined. The classical model-fitting and the advanced isoconversional methods were used to determine the activation energy of the different reactions. The advanced isoconversional method leads to a good agreement between isothermal, nonisothermal and rheological results. The effective activation energies of primary amine epoxy reaction, etherification and homopolymerization were estimated to about 55-60, 104 and 170 kJ mol−1, respectively. 相似文献
47.
Recently, clinicians have observed an increase in the incidence of laryngeal papilloma coincident with the rising incidence of venereal warts. The lesions occur in young adults of professional singing age. Different types of human papillomavirus (HPV) are presented. Gynecologic exam revealed cervical tumors, involving 18 HPV in benign and malignant lesions. Thirty patients with the following pathologic conditions were studied: 10 papillomas, 10 severe dysplasias, and 10 invasive cancers. All the lesions were located on the free edge of the vocal folds or the anterior commissure involving the epithelium. The results are as follows: 11 patients (33%) had virus infection, of which four had HPV 6 or HPV 11 on laryngeal papilloma, three had HPV 16 or HPV 18 on severe dysplasia, four had HPV 16 or HPV 18 on carcinoma; and 19 (66%) had no virus infection. Gynecologic research in this field is more advanced. However, this preliminary report raises interesting research questions in laryngology. 相似文献
48.
Contracted atomic basis sets have been constructed from ANOs in order to describe the ground and excited states of C and N and their anions. Application is given with the MCSCF calculation of the vibration frequency of CN− and of other spectroscopic constants. A procedure is proposed to do MCSCF calculations when some problems of convergence arise. 相似文献
49.
Identification of alkyl-5H-6,7-dihydrococyclopenta[b]pyrazines in roasted meat flavor. Model reaction used as basis for natural product formation and new synthesis. Seven alkyl-5H-6,7-dihydrocyclopenta[b]pyrazines have been identified in a roasted meat aroma obtained by thermolysis of the hydrosoluble flavor precursors of raw meat. Formation of these heterocyclics by condensation of hydroxycyclopentenones with aliphatic α-dicarbonyl compounds in the presence of ammonia has been confirmed by a model reaction. Alkyl-5H-cyclopenta[b]pyrazines and dicyclopenta [b,e]pyrazines are also obtained from this reaction, but have not yet been identified in roasted flavors. Preparation of the intermediates of the model reaction enabled development of an economical synthesis of 2,3,5-trimethyl-5H-6,7-dihydrocyclopenta[b]pyrazine. 相似文献
50.