全文获取类型
收费全文 | 807篇 |
免费 | 30篇 |
国内免费 | 1篇 |
专业分类
化学 | 500篇 |
晶体学 | 7篇 |
力学 | 14篇 |
数学 | 80篇 |
物理学 | 237篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 23篇 |
2019年 | 16篇 |
2018年 | 16篇 |
2017年 | 11篇 |
2016年 | 35篇 |
2015年 | 20篇 |
2014年 | 34篇 |
2013年 | 54篇 |
2012年 | 54篇 |
2011年 | 44篇 |
2010年 | 48篇 |
2009年 | 30篇 |
2008年 | 49篇 |
2007年 | 38篇 |
2006年 | 44篇 |
2005年 | 34篇 |
2004年 | 26篇 |
2003年 | 23篇 |
2002年 | 30篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有838条查询结果,搜索用时 46 毫秒
31.
32.
Campos LM Dang H Ng D Yang Z Martinez HL Garcia-Garibay MA 《The Journal of organic chemistry》2002,67(11):3749-3754
A detailed thermochemical analysis of the alpha-cleavage and decarbonylation reactions of acetone and several ketodiesters was carried out with the B3LYP/6-31G* density functional method. The heats of formation of several ground-state ketones and radicals were calculated at 298 K to determine bond dissociation energies (BDE) and radical stabilization energies (RSE) as a function of substituents. Results show that the radical-stabilizing abilities of the ketone substituents play a very important role on the thermodynamics of the alpha-cleavage and decarbonylation steps. An excellent correlation between calculated values and previous experimental observations suggests that photochemical alpha-cleavage and decarbonylation in crystals should be predictable from knowledge of excitation energies and the RSE of the substituent. 相似文献
33.
Complete 1H and 13C NMR assignments of aurasperone A and fonsecinone A, two bis-naphthopyrones produced by Aspergillus aculeatus 总被引:1,自引:0,他引:1
Campos FR Barison A Daolio C Ferreira AG Rodrigues-Fo E 《Magnetic resonance in chemistry : MRC》2005,43(11):962-965
Complete assignments of 1H and 13C NMR chemical shifts of the polyketides aurasperone A and fonsecinone A were made by means of nuclear Overhauser enhancement and heteronuclear NMR correlation experiments. These compounds were isolated for the first time from Aspergillus aculeatus, an endophytic fungus obtained from leaves of Melia azedarach(Meliaceae). 相似文献
34.
35.
Jamilson R. Campos 《Linear and Multilinear Algebra》2013,61(3):322-346
Considering the successful theory of multiple summing multilinear operators as a prototype, we introduce the classes of multiple Cohen strongly p-summing multilinear operators and polynomials. The adequacy of these classes under the viewpoint of the theory of multilinear and polynomial ideals and holomorphy types is discussed in detail. 相似文献
36.
37.
I. Campos E. Fernández-del-Castillo S. Heinemeyer A. Lopez-Garcia F. Pahlen G. Borges 《The European Physical Journal C - Particles and Fields》2013,73(4):1-17
We present a new environment for computations in particle physics phenomenology employing recent developments in cloud computing. On this environment users can create and manage “virtual” machines on which the phenomenology codes/tools can be deployed easily in an automated way. We analyze the performance of this environment based on “virtual” machines versus the utilization of physical hardware. In this way we provide a qualitative result for the influence of the host operating system on the performance of a representative set of applications for phenomenology calculations. 相似文献
38.
Pedro Marcos Frugeri Camila Marchioni Ayla Campos do Lago Célio Wisniewski 《Analytical letters》2018,51(10):1492-1504
This work proposes a flow injection analysis system for sulfaguanidine determination in pharmaceutical and food samples. The method was based on the reaction of sulfaguanidine with nitronium ion to produce a colored complex whose absorbance was measured at 545?nm. The flow injection analysis system’s significant parameters were checked by a fractional factorial design 27–2 and optimization by a Doehlert matrix. The flow injection analysis system shows optimum values at 0.28, 2.00, and 0.11% (w/v) for N-naphtil ethylenediamine, ammonium sulfamate, and sodium nitrite concentrations, respectively. The possible interferents present in pharmaceutical and food samples were assessed by a multivariate technique and depicted on probability charts, indicating no significant interferences at the 95% level of confidence interval. The method showed detection and quantification limits of 0.012 and 0.039?mg?L?1, an analytical frequency of 30 readings h?1 and precision always lower than 5.0% expressed as the relative standard deviation. The obtained results were in accordance with those obtained by high-performance liquid chromatography. 相似文献
39.
In the context of symmetric-definite generalized eigenvalue problems, it is often required to compute all eigenvalues contained
in a prescribed interval. For large-scale problems, the method of choice is the so-called spectrum slicing technique: a shift-and-invert
Lanczos method combined with a dynamic shift selection that sweeps the interval in a smart way. This kind of strategies were
proposed initially in the context of unrestarted Lanczos methods, back in the 1990’s. We propose variations that try to incorporate
recent developments in the field of Krylov methods, including thick restarting in the Lanczos solver and a rational Krylov
update when moving from one shift to the next. We discuss a parallel implementation in the SLEPc library and provide performance
results. 相似文献
40.
de Oliveira Elcio Cruz de Santana Maia Lúcio Abdala da Costa Lívio Garcia Lourenço Túlio Campos 《Accreditation and quality assurance》2018,23(6):365-369
Accreditation and Quality Assurance - In any commercial transaction, the presence of tolerances from specification limits is essential to ensure that the true value of the property of interest is... 相似文献