全文获取类型
收费全文 | 183篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 134篇 |
力学 | 4篇 |
数学 | 24篇 |
物理学 | 28篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 7篇 |
2008年 | 9篇 |
2007年 | 14篇 |
2006年 | 12篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 5篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有190条查询结果,搜索用时 15 毫秒
111.
Dr. Ivana Miletto Dr. Marta Meazza Dr. Geo Paul Prof. Maurizio Cossi Prof. Enrica Gianotti Prof. Leonardo Marchese Dr. Ramon Rios Prof. Marc Pera-Titus Prof. Robert Raja 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(72):e202202771
A designed N-heterocyclic carbene (NHC) catalyst was covalently anchored on a range of mesoporous and hierarchical supports, to study the influence of pore size in the benzoin condensation of furfural. The structural and spectroscopic characteristics of the anchored catalysts were investigated, also with the help of molecular dynamics simulations, in order to rationalize the degree of stability and recyclability of the heterogenized organocatalysts. Quantitative yields (99 %) and complete recyclability were maintained after several cycles, vindicating the design rationale. 相似文献
112.
Mannu Alberto Di Pietro Maria Enrica Priola Emanuele Baldino Salvatore Sacchetti Alessandro Mele Andrea 《Research on Chemical Intermediates》2021,47(4):1663-1674
Research on Chemical Intermediates - The selective formation of the heterocyclic salt ((1,4-dioxane-2,5-diyl)-bis-(methylene))-bis-(triphenylphosphonium) chloride was observed when epichlorohydrin... 相似文献
113.
Emilia Mezzetti Dario Portelli 《Abhandlungen aus dem Mathematischen Seminar der Universit?t Hamburg》2000,70(1):211-238
A classification theorem is given of projective threefolds that are covered by the lines of a two-dimensional family, but
not by a higher dimensional family. Precisely, ifX is such a threefold, let Σ denote the Fano scheme of lines onX and μ the number of lines contained inX and passing through a general point ofX. Assume that Σ is generically reduced. Then μ ≤ 6. Moreover,X is birationally a scroll over a surface (μ = 1), orX is a quadric bundle, orX belongs to a finite list of threefolds of degree at most 6. The smooth varieties of the third type are precisely the Fano
threefolds with −K
X
= 2H
X
.
This work has been done in the framework of the activities of EAGER. Both authors have been supported by funds of MURST, Progetto
Geometria Algebrica, Algebra Commutativa e Aspetti Computazionali.
The paper has been widely improved while the second author was guest at the University of Oslo. The financial support from
both the University of Oslo and the Norwegian Research Council is gratefully aknowledged. 相似文献
114.
115.
116.
Dr. Thomas Scattolin Enrica Bortolamiol Prof. Dr. Fabiano Visentin Dr. Stefano Palazzolo Dr. Isabella Caligiuri Dr. Tiziana Perin Prof. Dr. Vincenzo Canzonieri Dr. Nicola Demitri Prof. Dr. Flavio Rizzolio Prof. Dr. Antonio Togni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11868-11876
The first palladium organometallic compounds bearing N-trifluoromethyl N-heterocyclic carbenes have been synthesized. These η3-allyl complexes are potent antiproliferative agents against different cancer lines (for the most part, IC50 values fall in the range 0.02–0.5 μm ). By choosing 1,3,5-triaza-7-phosphaadamantane (PTA) as co-ligand, we can improve the selectivity toward tumor cells, whereas the introduction of 2-methyl substituents generally reduces the antitumor activity slightly. A series of biochemical assays, aimed at defining the cellular targets of these palladium complexes, has shown that mitochondria are damaged before DNA, thus revealing a behavior substantially different from that of cisplatin and its derivatives. We assume that the specific mechanism of action of these organometallic compounds involves nucleophilic attack on the η3-allyl fragment. The effectiveness of a representative complex, 4 c , was verified on ovarian cancer tumoroids derived from patients. The results are promising: unlike carboplatin, our compound turned out to be very active and showed a low toxicity toward normal liver organoids. 相似文献
117.
Stephanie Chapman Dr. Alexander J. O'Malley Dr. Ivana Miletto Dr. Marina Carravetta Dr. Paul Cox Prof. Enrica Gianotti Leonardo Marchese Dr. Stewart F. Parker Prof. Robert Raja 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(42):9938-9947
Soft templating with siliceous surfactant is an established protocol for the synthesis of hierarchically porous silicoaluminophosphates (HP SAPOs) with improved mass transport properties. Motivated by the enhanced performance of HP SAPOs in the Beckmann rearrangement of cyclohexanone oxime to the nylon 6 precursor ϵ-caprolactam, an integrated theoretical and empirical study was carried out to investigate the catalytic potential of the siliceous mesopore network. Inelastic neutron scattering (INS) studies, in particular, provided unique insight into the substrate-framework interactions in HP (Si)AlPOs and allowed reactive species to be studied independent of the catalyst matrix. The spectroscopic (INS, FTIR spectroscopy, MAS NMR spectroscopy) and computational analyses revealed that in the organosilane-templated SAPO, the interconnectivity of micro- and mesopores permits cooperativity between their respective silanol and Brønsted acid sites that facilitates the protonation of cyclohexanone oxime in a physical mixture at ambient temperature. 相似文献
118.
119.
We present a new method to study 4-dimensional linear spaces of skew-symmetric matrices of constant co-rank 2, based on rank 2 vector bundles on P3 and derived category tools. The method allows one to prove the existence of new examples of size 10×10 and 14×14 via instanton bundles of charge 2 and 4 respectively, and it provides an explanation for what used to be the only known example (Westwick 1996 [25]). We also give an algorithm to construct explicitly a matrix of size 14 of this type. 相似文献
120.
A permutominide is a set of cells in the plane satisfying special connectivity constraints and uniquely defined by a pair of permutations.
It naturally generalizes the concept of permutomino, recently investigated by several authors and from different points of view [1, 2, 4, 6, 7]. In this paper, using bijective
methods, we determine the enumeration of various classes of convex permutominides, including, parallelogram, directed convex,
convex, and row convex permutominides. As a corollary we have a bijective proof for the number of convex permutominoes, which
was still an open problem. 相似文献