全文获取类型
收费全文 | 395篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 284篇 |
晶体学 | 7篇 |
力学 | 11篇 |
数学 | 13篇 |
物理学 | 87篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 8篇 |
2013年 | 20篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 18篇 |
2009年 | 13篇 |
2008年 | 23篇 |
2007年 | 19篇 |
2006年 | 15篇 |
2005年 | 18篇 |
2004年 | 15篇 |
2003年 | 23篇 |
2002年 | 21篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有402条查询结果,搜索用时 15 毫秒
311.
E. Kuzmann Z. Klencsár Z. Homonnay A Vértes G. Braga A. C. De Oliveira V. K. Garg M. Bódogh I. Kotsis A. Nath 《Journal of Radioanalytical and Nuclear Chemistry》2000,246(2):313-316
57Fe and 151Eu Mössbauer spectroscopy as well as RF susceptibility measurements were applied to study the effects of Pr substitution either into the rare earth or into the Ba site in Eu1–x
Pr
x
Ba2Cu3O7– and EuBa2–x
Pr
x
Cu3O7–, respectively. Site mixing of Pr between the rare earth and Ba sites could be excluded by the utilization of 57Fe Mössbauer spectroscopy. It was found that there exists a correlation between the 151Eu isomer shift and the onset temperature of the superconducting transition independent of the location of Pr. RF susceptibility measurements provide an evidence for a difference in the magnetic moment of Pr substituted for the Eu or Ba sites. The obtained results can be explained by hole filling as the dominant effect of Pr substitution. 相似文献
312.
Zeni G Alves D Pena JM Braga AL Stefani HA Nogueira CW 《Organic & biomolecular chemistry》2004,2(6):803-805
E-Vinylic tellurides undergo a direct cross-coupling reaction with terminal alkynes in the presence of palladium(II)/CuI in Et(3)N at room temperature to give E-enynes in good yields. The methodology represents a general and efficient protocol for carrying out the synthesis of E-enynes under mild conditions with complete retention of configuration. 相似文献
313.
Braga D Cojazzi G Emiliani D Maini L Grepioni F 《Chemical communications (Cambridge, England)》2001,(21):2272-2273
Exposure of the solid zwitterion [CoIII(eta 5-C5H4CO2H)(eta 5-C5H4CO2)] to hydrated vapours of volatile acids (HCl, CF3CO2H, HBF4) or bases (NH3, NMe3, NH2Me) quantitatively produces the corresponding salts; the heterogeneous reactions are fully reversible, as the acid or base molecules can be removed by thermal treatment, regenerating the starting material. 相似文献
314.
315.
316.
A.M. Pereira C. Magen M.E. Braga R.P. Pinto R. Fermento P.A. Algarabel L. Morellon M.R. Ibarra J.P. Araújo J.B. Sousa 《Journal of Non》2008,354(47-51):5298-5300
We report high resolution measurements of the electrical resistivity (ρ, dρ/dT) and thermopower (S, dS/dT) measurements near the magnetic and structural transition of the layered Tb5Si2Ge2 compound, which are fairly close but not fully coupled. The analysis of the transport properties confirms a split magneto/structural transition, with TS ~ 97 K and TS ~ 107 K for the structural transition (on cooling and heating respectively; 1st-order transition). The magnetic transition occurs only at TC ~ 112 K and without hysteresis (2nd-order transition). The magnetic critical behavior of resistivity is analyzed, obtaining an almost classical mean field exponent (α ~ 0.59) for T > TC. For the structural phase, and below TS, we obtain a rather different exponent (α ~ 1.06). 相似文献
317.
ABSTRACT A method for the optimization of plane cable trusses with loads distributed along the cables according to any arbitrary law, as well as a suitable finite element model for the individual cable section, is presented. The optimization method is divided into two steps. In the first, the structure is optimized through the use of a simplified model in which the two main cables are considered continuously connected by an infinite number of vertical inex-tensible wires. In the second step the optimal solution obtained for the simplified model serves as the point of departure for the optimization of the real structure, using Powell's method of conjugate directions. Suitable external penalty functions guarantee that the solution is feasible. A numerical example is also given. 相似文献
318.
Carlos J. Braga Barros Josiney A. Souza 《Journal of Dynamics and Differential Equations》2010,22(4):723-740
Let ${\mathcal{S}}$ be a semigroup acting on a topological space M. We define attractors for the action of ${\mathcal{S}}$ on M. This concept depends on a family ${\mathcal{F}}$ of subsets of ${\mathcal{S}}$ . For certain semigroups and families it recovers the concept of attractors for flows or semiflows. We define and study the complementary repeller of an attractor. We also characterize the set of chain recurrent points in terms of attractors. 相似文献
319.
The dynamic speckle analysis has been done because speckle interference began to be evaluated as an important source of information, especially those related to biological samples under laser beam. The time history speckle pattern, a THSP image, is an approach to analyze, which allows a summary to represent the activity monitored. THSP adoption has compelled the research to evaluate the information and the reliability of its inner pattern. This study presents a statistical approach to analyze the data using white noise tests and cross-spectrum analysis. The data analyzed was a set of THSP from animal sperm samples. The evaluation of white noise among lines was conducted using the Fischer test over eight THSP and the cross-spectral approach has been conducted by comparing the information in each THSP. The results presented that the THSP of the sperm did not behave as a white noise in a global evaluation, and specifically in the Gaussian white noise test over 4096 lines; only six lines presented the behavior of a white noise pattern. The strong rejection of white noise test confirms that the THSP pattern allows reliable information. The results obtained with the cross-spectral analysis presented differences between lines within the same THSP, showing that the information of an inner pattern varies in relation to space, which is against the findings in literature. 相似文献
320.
Dario Braga Lucia Maini Fabrizia Grepioni 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1998,110(16):2365-2366