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排序方式: 共有124条查询结果,搜索用时 15 毫秒
81.
C. PIZARRO N. PÉREZ‐DEL‐NOTARIO C. SÁENZ‐GONZÁLEZ S. RODRÍGUEZ‐TECEDOR J. M. GONZÁLEZ‐SÁIZ 《Archaeometry》2012,54(1):101-113
The transfer of advances in chemometrics into archaeometric research opens up a wide range of new application possibilities in this rapidly developing field. Neutron activation analysis (NAA) of ceramic samples from the Banda Traditional Area (west‐central Ghana) combined with chemometrics allowed us to establish a link between current and ancient systems of ceramics production in the historic settlements of Kuulo Kataa and Makala Kataa. Principal component analysis (PCA) and the soft independent modelling of class analogy (SIMCA) method were applied to the Das Dores Cruz data set in order to unequivocally determine the geographical origin of the diverse archaeological samples. After global autoscaling pretreatment, PCA analysis showed a clear difference between samples from different locations. The classification models obtained by SIMCA showed a classification ability of 100% and a prediction ability of 97.7%, with a mean sensitivity of 84% and a specificity of 100% for the three categories. The application of SIMCA showed that some NAA variables (elements) were more important than others in terms of geographical classification. With the class models that we obtained, we were able to determine the origin of the ancient remains. SIMCA has proved to be a powerful technique for the class modelling of archaeological data. 相似文献
82.
Éric Bordas 《Modern & Contemporary France》2013,21(2):241-254
Maxence, J.‐L., Les Écrivains sacrifiés des années sida (Bayard, 1997), 139 pp., 100F, ISBN 2 227 304 02 2 Thomé‐Renault, A., Le Traumatisme de la mort annoncée. Psychosomatique et sida (Dunod, 1996), 196 pp., 158F, ISBN 2 10 002488 4 相似文献
83.
Heat treatment of lithic raw material is known from the Middle Stone Age to the Neolithic. These findings require archaeometric techniques and methods for detecting the heat‐induced effects within lithic artefacts. However, the existing methods are often cost‐intensive and time‐consuming, and most of them are destructive. Here, we present a new method using the infrared spectroscopic measurement of the strength of H‐bonds formed between surface silanole groups (SiOH) and H2O molecules held in open pores of the samples. The reduction of H‐bond strength in chalcedony is shown to be strongly correlated with the loss of open pores induced by heat treatment. Hence, the method is based on measuring one of the transformations aimed for by the instigators of the heat treatment: the reduction of porosity that modifies the rock's mechanical properties. A first application to heat‐treated material from the Neolithic Chassey culture (southern France) shows that flint was heated to temperatures between 200°C and 250°C in this period. This has important implications for the study of the procedures used and the heating environments. Our new method is non‐destructive, rapid, cost‐effective and allows for detection of the used annealing temperatures. 相似文献
84.
Étienne Klein 《Revue de synthèse / Centre international de synthèse》2013,134(1):9-27
Since his mysterious disappearance in 1938, there have been many biographical accounts of Ettore Majorana’s short life. Yet, his scientific work and his influence on the development of physics are often left in the background. The thrust of this article is precisely to shed light on them. In fact, some of Majorana’s articles were only understood after World War II. Notably, this was the case of his last article. Written in 1937, it represents the best long-lasting contribution of Ettore Majorana to particle physics. He envisages, thanks to a new formalism, that neutrinos could be identical to their own antiparticles. The answer to this question posed by Majorana more than half a century ago may be found thanks to several experiments now carried out. It could give a lightning on the nature of dark matter and an explanation to the dominance of matter over antimatter in our universe. 相似文献
85.
86.
CATHERINE BERGE-THIERRY FABRICE COTTON† OONA SCOTTI DAPHNÉ-ANNE GRIOT-POMMERA YOSHIMITSU FUKUSHIMA 《Journal of Earthquake Engineering》2013,17(2):193-222
This paper presents response spectral attenuation laws used in the new French Safety Rule, which is the reference for nuclear safety studies in France. Attenuation laws were derived from 965 horizontal and 485 vertical components from a two-step inversion method and accounts for geometrical spreading, anelastic attenuation and geological site condition. The datasets are mainly constituted of European strong motion records (83%) recently collected and homogeneously processed. In order to complete the distribution data beyond magnitude 6, a few American records were added, representing 17% of the datasets. The magnitude type and source-to-site distance definitions chosen to derive the laws are tested with respect to other definitions. These parametric tests induce a conservative law, for some magnitude and distance ranges of interest. The residual values between observed and predicted spectral accelerations are studied and do not exhibit any bias. The inferred laws are in good agreement with classical strong motion attenuation laws. 相似文献
87.
Éric Montpetit 《政策研究杂志》2011,39(3):513-533
One of the original objectives of the advocacy coalition framework (ACF) was to shed light on the role of science in policymaking. The ACF depicts subsystem scientists as political actors just like any other. Unfortunately, science has never become a major theme of research within the framework and, as a consequence, its role in policymaking remains under‐theorized, leaving ample room for interpretation. This article seeks to explore the validity of three propositions about the role of science in policy. The first two are derived from the ACF: (i) the capacity of scientists to provide credible advice is affected by the harshness of the political debates dividing the policy subsystem; and (ii) agreement among scientists is just as common as among other groupings of policy actors. The third is derived from an “error costs” argument: (iii) Disagreements among scientists are even more pronounced than disagreements among other policy actors. Using the results of a survey of policy actors in 17 biotechnology subsystems, this article finds support for the first and third propositions. Indeed, scientists' participation in political divisions might even be underestimated by the ACF. The article concludes with attempts to clarify the role of scientists within the ACF, including discussions of ambiguity regarding the role of professional forums and of scientists in between‐coalition learning within policy subsystems. 相似文献
88.
89.
Microthermometry and volumetric analysis are now widely used techniques in petroleum geology, which allow the reconstitution of the composition and P‐T trapping conditions of petroleum inclusions. However, these methods require efficient thermodynamic modeling tools of the PVT properties, coupled with compositional models for petroleum. Two methods presently available are reviewed here. The first one, called the α–β method, uses a compositional model describing the full spectrum (C1–C500) of natural hydrocarbons with two adjustable parameters α and β. The second technique is based on a so‐called fluid model, i.e., a priori knowledge of the composition and the physical properties of the C7+ cut of the trapped petroleum. Up to now, no critical appraisal has been undertaken for these two methods. From an extensive compilation of literature data (201 points), we here show that both techniques are able to describe the composition of crude oils and to predict satisfactorily their saturation pressures. However, the predictive capabilities of fluid models are highly dependent on the correlations used for describing heavy cuts, and we indicate those which give the best results. Finally, we emphasize the key control of the bulk methane mole fraction (x1) on the saturation pressure: this result allows us to build simplified versions of α–β and fluid models, applicable to the majority of crude oils, and whose formulation depends advantageously on x1 only. 相似文献
90.