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排序方式: 共有514条查询结果,搜索用时 265 毫秒
161.
Daniel Kaiser Dr. Aurélien de la Torre Saad Shaaban Prof. Dr. Nuno Maulide 《Angewandte Chemie (International ed. in English)》2017,56(21):5921-5925
Much contemporary organic synthesis relies on transformations that are driven by the intrinsic, so-called “natural”, polarity of chemical bonds and reactive centers. The design of unconventionally polarized synthons is a highly desirable strategy, as it generally enables unprecedented retrosynthetic disconnections for the synthesis of complex substances. Whereas the umpolung of carbonyl centers is a well-known strategy, polarity reversal at the α-position of a carbonyl group is much rarer. Herein, we report the design of a novel electrophilic enolonium species and its application in efficient and chemoselective, metal-free oxidative C−C coupling. 相似文献
162.
163.
Total Syntheses and In Vivo Quantitation of Novel Neurofuran and Dihomo‐isofuran Derived from Docosahexaenoic Acid and Adrenic Acid
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Aurélien de la Torre Yiu Yiu Lee Attilio Mazzoni Dr. Alexandre Guy Dr. Valérie Bultel‐Poncé Dr. Thierry Durand Dr. Camille Oger Dr. Jetty Chung‐Yung Lee Dr. Jean‐Marie Galano 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2442-2446
Neurofurans (NeuroFs) and dihomo‐isofurans (dihomo‐IsoFs) are produced in vivo by non‐enzymatic free‐radical pathways from docosahexaenoic and adrenic acids, respectively. As these metabolites are produced in minute amounts, their analyses in biological samples remain challenging. Syntheses of neurofuran and dihomo‐isofurans described are based on a pivotal strategy, thanks to an enantiomerically enriched intermediate, which allowed, for the first time, access to both families: the alkenyl and enediol. Owing to this formation, quantitation of specific NeuroF and dihomo‐IsoFs in biological samples was attainable. 相似文献
164.
Andrea Salvo Giovanna Loredana La Torre Rossella Vadalà Antonio Francesco Mottese Emanuele Saija 《Natural product research》2016,30(13):1517-1525
Considering that the determination of authenticity and of the geographical origin of food is a very challenging issue, in this study we studied by means of histological and histochemical analyses the famous Sicilian lemon known as ‘Interdonato Lemon of Messina PGI’. Since the protected geographical indication Interdonato lemon of Messina possesses high organoleptic properties, the composition of the hexane extract of lemon peel was determined by HRGC and HRGC–MS analyses and compared with that of lemon of different cultivars. The results obtained are informative of the oil’s quality and explain the variation of the lemon essential oil composition. Given the fundamental economic implications of any fraud, the aim of this study was to determine a fingerprint able to evaluate the authentication of the geographic origin in such way to prevent frauds in national and international markets. 相似文献
165.
166.
R. Lapovok F.H. Dalla Torre C.H.J. Davies P.F. Thomson 《Journal of the mechanics and physics of solids》2005,53(4):729-747
A further development of the mechanism-based strain gradient plasticity model well established in literature is reported. The major new element is the inclusion of the cell size effect in dislocation cell forming materials. It is based on a ‘phase mixture’ approach in which the dislocation cell interiors and dislocation cell walls are treated as separate ‘phases’. The model was applied to indentation testing of copper severely pre-strained by equal channel angular pressing. The deformation behaviour and the intrinsic length scale parameter of the gradient plasticity model were related to the micro-structural characteristics, notably the dislocation cell size, resulting from the deformation history of the material. 相似文献
167.
Since Markowitz (1952) formulated the portfolio selection problem, many researchers have developed models aggregating simultaneously several conflicting attributes such as: the return on investment, risk and liquidity. The portfolio manager generally seeks the best combination of stocks/assets that meets his/her investment objectives. The Goal Programming (GP) model is widely applied to finance and portfolio management. The aim of this paper is to present the different variants of the GP model that have been applied to the financial portfolio selection problem from the 1970s to nowadays. 相似文献
168.
Diego R. Alcoba Alicia Torre Luis Lain Ofelia B. Oña Josep M. Oliva 《International journal of quantum chemistry》2014,114(14):952-958
This work studies the ability of the two‐center local spin quantities, provided by the partitioning of the expectation value of the spin‐squared operator corresponding to N‐electron systems, for determining spin‐exchange coupling constants within the Heisenberg spin Hamiltonian model. The spin‐exchange parameters, which characterize this Hamiltonian for a determined system, have been evaluated in the HeH2 aggregate and in several clusters (n = 2, 3, 4) with different geometrical arrangements, using internuclear distances larger than the equilibrium ones (beyond the bonding regions). The results found have been analyzed and compared with those arising from other approaches, showing the feasibility of our methodology. © 2014 Wiley Periodicals, Inc. 相似文献
169.
Aurlien deLaTorre Yiu Yiu Lee Camille Oger Per Torp Sangild Thierry Durand Jetty Chung‐Yung Lee Jean‐Marie Galano 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(24):6363-6366
The growing importance of lipidomics, and the interest of non‐enzymatic metabolites of polyunsaturated fatty acids (PUFAs) prompted us to initiate the synthesis of novel dihomo‐IsoF compounds. Such metabolites of adrenic acid, the main PUFA in white matter, were synthesized using a divergent approach based on an orthoester cyclization. LC‐MS/MS investigation on pig brains showed the potential of this novel biomarker for the first time, as a powerful new tool for brain lipid peroxidation assessment. 相似文献
170.
Dr. Kaizheng Zhu Dr. Ramón Pamies Dr. Nodar Al-Manasir Dr. José Ginés Hernández Cifre Prof. José García de la Torre Prof. Bo Nyström Prof. Anna-Lena Kjøniksen 《Chemphyschem》2020,21(12):1258-1271
The thermoresponsive nature of aqueous solutions of poly(N-isopropylacrylamide) (PNIPAAM) star polymers containing 2, 3, 4, and 6 arms has been investigated by turbidity, dynamic light scattering, rheology, and rheo-SALS. Simulations of the thermosensitive nature of the single star polymers have also been conducted. Some of the samples form aggregates even at temperatures significantly below the lower critical solution temperature (LCST) of PNIPAAM. Increasing concentration and number of arms promotes associations at low temperatures. When the temperature is raised, there is a competition between size increase due to enhanced aggregation and a size reduction caused by contraction. Monte Carlo simulations show that the single stars contract with increasing temperature, and that this contraction is more pronounced when the number of arms is increased. Some samples exhibit a minimum in the turbidity data after the initial increase at the cloud point. The combined rheology and rheo-SALS data suggest that this is due to a fragmentation of the aggregates followed by re-aggregation at even higher temperatures. Although the 6-arm star polymer aggregates more than the other stars at low temperatures, the more compact structure renders it less prone to aggregation at temperatures above the cloud point. 相似文献