全文获取类型
收费全文 | 364篇 |
免费 | 7篇 |
专业分类
化学 | 245篇 |
晶体学 | 2篇 |
力学 | 27篇 |
数学 | 50篇 |
物理学 | 47篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 12篇 |
2015年 | 23篇 |
2014年 | 10篇 |
2013年 | 23篇 |
2012年 | 27篇 |
2011年 | 45篇 |
2010年 | 16篇 |
2009年 | 12篇 |
2008年 | 23篇 |
2007年 | 21篇 |
2006年 | 11篇 |
2005年 | 20篇 |
2004年 | 10篇 |
2003年 | 15篇 |
2002年 | 14篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1963年 | 1篇 |
1955年 | 1篇 |
1944年 | 1篇 |
1943年 | 1篇 |
排序方式: 共有371条查询结果,搜索用时 15 毫秒
131.
Guilherme Tsuguio Tanaka Fabrício de Oliveira Ferreira Carlos Eduardo Ferreira da Silva Danilo Luiz Flumignan Jos Eduardo de Oliveira 《Journal of Chemometrics》2011,25(9):487-495
Samples of commercial gasoline, from the National Program of Fuel Quality Monitoring of the National Petroleum Agency, were collected from gas stations located in the Midwestern state of Sao Paulo, Brazil, and analyzed by several physicochemical standard methods established by ANP Resolution no. 309. Also, important information related to tampering was analyzed with the marker solvent. Statistical analysis and exploratory chemometric were employed to discriminate the presence of markers of solvents in commercial gasoline. The results showed that statistical and chemometric parameters such as atmospheric distillation temperatures T10 and T90, RON, benzene and saturated and aromatic hydrocarbons satisfactorily describe the presence of marker solvent, usually with a probability exceeding 70%. Furthermore, after optimizing the SIMCA algorithm, sensitivity in the training set with cross‐validation leave‐one‐out (83.8%) and the set of prediction (77.1%) were revealed. The proposed method will become indispensable and recommended for discriminating samples of fuels for commercial applications in routine monitoring programs and quality control. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
132.
María D. Gonzalez-Lima Aurelio R. L. Oliveira Danilo E. Oliveira 《Computational Optimization and Applications》2013,56(3):573-597
We introduce an efficient and robust proposal for solving linear systems arising at each iteration of primal-dual interior-point methods for linear programming. Our proposal is based on the stable system presented by Gonzalez-Lima et al. (Comput. Opt. Appl. 44:213–247, 2009). Using similar techniques as those employed in the splitting preconditioner introduced by Oliveira and Sorensen (Linear Algebra Appl. 394:1–24, 2005) we are able to express the stable system matrix in block form such that the diagonal blocks are nonsingular diagonal matrices and the off-diagonal blocks are matrices close to zero when the iterates are close to the solution set of the linear programming problem. For degenerate problems a perturbation of the diagonal is added. We use a low-cost fixed iterative method to solve this system. Numerical experiments have shown that our approach leads to very accurate solutions for the linear programming problem. 相似文献
133.
Danilo D. da Silva 《代数通讯》2013,41(5):2234-2242
We give an alternative proof to the fact that, if the square of the infinite radical of the module category of an Artin algebra is equal to zero, then the algebra is of finite type by making use of the theory of postprojective and preinjective partitions. Further, we use this new approach in order to get a characterization of finite subcategories of Δ-good modules of a quasi-hereditary algebra in terms of depth of morphisms similar to a recently obtained characterization of Artin algebras of finite type. 相似文献
134.
We present dynamic linked graphs for exploratory analysis of spatial marked point processes data and give an introduction to our exploratory graphical analysis tool, called Marked Point Processes Exploratory Analysis (MaPPEA). In particular, we consider point processes with events marked with another spatial event representing origin-destination data types. Using linked windows brushing, MaPPEA provides an illustration of the structure and relationships between marks and locations of point patterns. The main feature is the dynamically changing, spatially localized graphical summary of the mark distribution. Many different graphical summaries are available, and they are updated dynamically as the user moves the mouse on the map showing the events. The methods are illustrated with data on car theft location and the eventual car retrieval location and on trees’ locations and their associated marks. This article has supplementary material online. 相似文献
135.
136.
Danilo P. Sant’Ana 《Tetrahedron letters》2009,50(27):3753-9297
Two 5-deoxypterocarpens, one pterocarpen, and one coumestan were prepared from deoxychromenes, chromenes, and ortho-iodophenols. The key step in the described synthetic approach is an intramolecular Heck reaction leading to the formation of the C-ring present in the structure of these compounds. 相似文献
137.
Generali Tiziana Stefanelli Patrizia Girolimetti Silvana Barbini Danilo Attard 《Accreditation and quality assurance》2019,24(1):13-18
Accreditation and Quality Assurance - The Italian National Reference Laboratory (NRL) for pesticide residues yearly organizes proficiency tests (PTs) on olive oil in cooperation with the... 相似文献
138.
Entropy-based methods have received considerable attention in the quantification of structural complexity of real-world systems. Among numerous empirical entropy algorithms, conditional entropy-based methods such as sample entropy, which are associated with amplitude distance calculation, are quite intuitive to interpret but require excessive data lengths for meaningful evaluation at large scales. To address this issue, we propose the variational embedding multiscale sample entropy (veMSE) method and conclusively demonstrate its ability to operate robustly, even with several times shorter data than the existing conditional entropy-based methods. The analysis reveals that veMSE also exhibits other desirable properties, such as the robustness to the variation in embedding dimension and noise resilience. For rigor, unlike the existing multivariate methods, the proposed veMSE assigns a different embedding dimension to every data channel, which makes its operation independent of channel permutation. The veMSE is tested on both stimulated and real world signals, and its performance is evaluated against the existing multivariate multiscale sample entropy methods. The proposed veMSE is also shown to exhibit computational advantages over the existing amplitude distance-based entropy methods. 相似文献
139.
Calmodulin and related Ca2+ -binding proteins were characterized using different labeling, chromatographic and spectroscopic techniques. Ca2+-binding to members of the so-called “EF-hand”- or “helix-loop-helix”-model protein family induced conformational changes, thereby exposing hydrophobic sites in some of them. These sites were identified using the photoreactive, carbene-generating, radioactive probe 3-(trifluoromethyl)-3-(m-[1251]iodophenyl)diazirine, and characterized using different high performance liquid chromatography techniques. The influence of chemical modification of some of the amino acid residues on the properties of calmodulin were characterized using circular dichroism. A correlation between an increase of oxidized methionine residues of calmodulin and a decrease of Ca2+-induced helical content was observed. 相似文献
140.
Laura Barp Giorgia Purcaro Flavio A. Franchina Mariosimone Zoccali Danilo Sciarrone Peter Q. Tranchida Luigi Mondello 《Analytica chimica acta》2015
Phthalates are a group of synthetic compounds mainly used as plasticizers, which have been classified as endocrine-disrupting chemicals and potential human-cancer causing agents. They can be found in high amounts in foods, deriving mainly from plastic packaging. The analytical determination of these compounds is very challenging since they are ubiquitous. Therefore, minimization of sample manipulation is highly desirable. 相似文献