全文获取类型
收费全文 | 250篇 |
免费 | 18篇 |
专业分类
化学 | 163篇 |
晶体学 | 10篇 |
力学 | 10篇 |
数学 | 36篇 |
物理学 | 49篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 18篇 |
2015年 | 11篇 |
2014年 | 10篇 |
2013年 | 26篇 |
2012年 | 26篇 |
2011年 | 23篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 17篇 |
2007年 | 10篇 |
2006年 | 13篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有268条查询结果,搜索用时 46 毫秒
101.
Didjour Albert Kambiré Jean Brice Boti Jean-Jacques Filippi Zanahi Félix Tonzibo 《Natural product research》2019,33(14):2109-2112
The leaf essential oil of Laggera pterodonta (DC.) Sch. Bip. ex Oliv. (Asteraceae) collected in the Eastern Côte d’Ivoire was investigated using a combination of chromatographic (GC-RI, CC, pc-GC) and spectroscopic (GC-MS, 13C NMR) techniques. Eighty-three components accounting for 98.0% of the whole composition were identified with 2,5-dimethoxy-p-cymene (43.3%), sabinene (14.1%), α-humulene (9.8%), (E)-β-caryophyllene (7.2%) and germacrene D (5.2%) as major compounds. This study led to the structural elucidation of a new natural compound, (3αH,4βH,6αH,1αMe)-1,6-epoxy-3-hydroxycarvotanacetone, angelic acid ester from the leaf oil by 1D and 2D NMR spectroscopy. 相似文献
102.
M. B. Gordon J. R. Iglesias V. Semeshenko J. P. Nadal 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(1):133-144
Crime is an economically relevant activity. It may represent a mechanism of wealth distribution but also a social and economic
burden because of the interference with regular legal activities and the cost of the law enforcement system. Sometimes it
may be less costly for the society to allow for some level of criminality. However, a drawback of such a policy is that it
may lead to a high increase of criminal activity, that may become hard to reduce later on. Here we investigate the level of
law enforcement required to keep crime within acceptable limits. A sharp phase transition is observed as a function of the
probability of punishment. We also analyze other consequences of criminality as the growth of the economy, the inequality
in the wealth distribution (the Gini coefficient) and other relevant quantities under different scenarios of criminal activity
and probabilities of apprehension. 相似文献
103.
Brice Lecampion 《Journal of the mechanics and physics of solids》2010,58(10):1701-1715
A non-hydrostatic stress field affects the orientation of crystals growing in the pore network of an elastic porous medium. The hypothesis of a hydrostatic state of stress within the crystal has been implicitly made in the recent extension of poromechanics to in-pore crystalization (Coussy, 2006). This underlying hypothesis is revisited on a small-scale conceptual model based on Eshelby's problem and shows that chemo-mechanical equilibrium requires that the crystal adapts its shape and orientation to the far-field stress, therefore resulting at equilibrium in a hydrostatic state of stress within the crystal. The optimum crystal shape as a function of the far-field stress is consistently investigated, highlighting limiting cases. The small scale model allows to understand the macroscopic effects associated with deviatoric stresses in the poromechanics of in-pore crystallization. Moreover, it provides the building block for an up-scaling of the macroscopic tangent poroelastic properties, which depend on both the current crystal saturation and the state of stress. A dilute micromechanical scheme illustrates the variation of the macroscopic Biot's coefficient tensor as a function of deviatoric stresses. A simple configuration akin to a potential laboratory experiment finally illustrates the strong induced anisotropy of the crystallization induced macroscopic strain when deviatoric stresses are applied to the material prior to crystallization. 相似文献
104.
Didjour Albert Kambir Jean Brice Boti Ahmont Claude Landry Kablan Daouda Ballo Mathieu Paoli Virginie Brunini Flix Tomi 《Molecules (Basel, Switzerland)》2021,26(20)
The chemical variability and the in vitro anti-inflammatory activity of the leaf essential oil from Ivorian Isolona dewevrei were investigated for the first time. Forty-seven oil samples were analyzed using a combination of CC, GC(RI), GC-MS and 13C-NMR, thus leading to the identification of 113 constituents (90.8–98.9%). As the main components varied drastically from sample to sample, the 47 oil compositions were submitted to hierarchical cluster and principal components analyses. Three distinct groups, each divided into two subgroups, were evidenced. Subgroup I−A was dominated by (Z)-β-ocimene, β-eudesmol, germacrene D and (E)-β-ocimene, while (10βH)-1β,8β-oxido-cadina-4-ene, santalenone, trans-α-bergamotene and trans-β-bergamotene were the main compounds of Subgroup I−B. The prevalent constituents of Subgroup II−A were germacrene B, (E)-β-caryophyllene, (5αH,10βMe)-6,12-oxido-elema-1,3,6,11(12)-tetraene and γ-elemene. Subgroup II−B displayed germacrene B, germacrene D and (Z)-β-ocimene as the majority compounds. Germacrene D was the most abundant constituent of Group III, followed in Subgroup III−A by (E)-β-caryophyllene, (10βH)-1β,8β-oxido-cadina-4-ene, germacrene D-8-one, and then in Subgroup III−B by (Z)-β-ocimene and (E)-β-ocimene. The observed qualitative and quantitative chemical variability was probably due to combined factors, mostly phenology and season, then harvest site to a lesser extent. The lipoxygenase inhibition by a leaf oil sample was also evaluated. The oil IC50 (0.020 ± 0.005 mg/mL) was slightly higher than the non-competitive lipoxygenase inhibitor NDGA IC50 (0.013 ± 0.003 mg/mL), suggesting a significant in vitro anti-inflammatory potential. 相似文献
105.
Marzin Tom Desvages Brice Creppy Adama Lépine Louis Esnault-Filet Annette Auradou Harold 《Transport in Porous Media》2020,132(2):283-297
Transport in Porous Media - Microbial-induced carbonate precipitation (MICP) in porous media is a two-step procedure: First, the suspension of bacteria is injected and some of the bacteria get... 相似文献
106.
Didjour Albert Kambir Ahmont Claude Landry Kablan Thierry Acafou Yapi Sophie Vincenti Jacques Maury Nicolas Baldovini Pierre Tomi Mathieu Paoli Jean Brice Boti Flix Tomi 《Molecules (Basel, Switzerland)》2022,27(12)
The variability of chemical composition of the leaf essential oil (EO) from Neuropeltis acuminata, a climbing liana growing wild in Ivory Coast, was investigated for the first time. The in vitro anti-inflammatory activity was also evaluated. Thirty oil samples were isolated from leaves collected in three forests of the country and analyzed using a combination of Column Chromatography (CC), Gas Chromatography with Retention Indices (GC(FID)), Gas Chromatography-Mass Spectrometry (GC-MS), and 13Carbon-Nuclear Magnetic Resonance (13C-NMR). Fractionation by CC led to the first-time isolation from natural source of δ-cadinen-11-ol, whose structural elucidation by one dimension (1D) and 2D-NMR spectroscopy is reported here. Finally, 103 constituents accounting for 95.7 to 99.6% of the samples’ compositions were identified. As significant variations of the major constituents were observed, the 30 oil compositions were submitted to hierarchical cluster and principal components analyses. Five distinct groups were evidenced: Group I, dominated by (E)-β-caryophyllene, kessane, and δ-cadinene, while the main constituents of Group II were germacrene B, ledol, α-humulene, (E)-γ-bisabolen-12-ol, and γ-elemene. Group III exhibited guaiol, germacrene D, atractylone, (E)-γ-bisabolen-12-ol, δ-cadinene and bulnesol as main compounds. Group IV was dominated by (E)-nerolidol, guaiol, selina-4(15),7(11)-diene and bulnesol, whereas (E)-β-caryophyllene, α-humulene and α-muurolene were the prevalent compounds of Group V. As the harvest took place in the same dry season in the three forests, the observed chemical variability could be related to harvest sites, which includes climatic and pedologic factors, although genetic factors could not be excluded. The leaf oil sample S24 behaved as a high inhibitor of LipOXygenase (LOX) activity (half maximum Inhibitory Concentration, IC50: 0.059 ± 0.001 mg mL−1), suggesting an anti-inflammatory potential. 相似文献
107.
108.
Enrique Nadal Emmanuelle Abisset-Chavanne Elias Cueto Francisco Chinesta 《Comptes Rendus Mecanique》2018,346(7):581-589
Even if the diffusion equation has been widely used in physics and engineering, and its physical content is well understood, some variants of it escape fully physical understanding. In particular, anormal diffusion appears in the so-called fractional diffusion equation, whose main particularity is its non-local behavior, whose physical interpretation represents the main part of the present work. 相似文献
109.
Alexandre Goldsztejn Ferenc Domes Brice Chevalier 《Journal of Global Optimization》2014,58(4):653-672
Three rejection tests for multi-objective optimization problems based on first order optimality conditions are proposed. These tests can certify that a box does not contain any local minimizer, and thus it can be excluded from the search process. They generalize previously proposed rejection tests in several regards: Their scope include inequality and equality constrained smooth or nonsmooth multiple objective problems. Reported experiments show that they allow quite efficiently removing the cluster effect in mono-objective and multi-objective problems, which is one of the key issues in continuous global deterministic optimization. 相似文献
110.
Y. P.?Ma S.?Gon?alves S.?Mignot J.-P.?Nadal M. B.?Gordon 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,71(4):597-610
Basic evidences on non-profit making and other forms of benevolent-based organizations reveal a rough partition of members
between some pure consumers of the public good (free-riders) and benevolent individuals (cooperators). We study the relationship between the community size and the level of cooperation in a simple
model where the utility of joining the community is proportional to its size. We assume an idiosyncratic willingness to join
the community ; cooperation bears a fixed cost while free-riding bears a (moral) idiosyncratic cost proportional to the fraction
of cooperators. We show that the system presents two types of equilibria: fixed points (Nash equilibria) with a mixture of
cooperators and free-riders and cycles where the size of the community, as well as the proportion of cooperators and free-riders,
vary periodically. 相似文献