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ZHAO YuLong * LIU ZhiFei COLIN Christophe XIE Xin & WU Qiong State Key Laboratory of Marine Geology Tongji University Shanghai China Laboratoire des Interactions et Dynamique des Environnements de Surface UMR CNRS-Université Paris-Sud Orsay France 《科学通报(英文版)》2011,56(33):3558-3565
High-resolution grain size and major element geochemical measurements were performed on the marine sediments of Core MD05-2895 to help understand the formation of turbidite sequences. Grain-size results show that these turbidite sediments contain more coarse sediment grains than normal marls. The coarse sediment grains are mostly derived from relict sediments on the Sunda Shelf. Relict sediments are composed mainly of quartz, feldspar, tephra and a few titaniferous or ferruginous heavy minerals. Corresponding to the concentration of these minerals, increases in Si/Al, K/Al, Ti/Al and Fe/Al ratios are observed in the turbidite layers. As all the observed turbidite sequences were deposited during the last glacial, the occurrence of these turbidity events is implied to be closely related to instabilities in sea-level-induced sediment supply. We suggest that deposition of sediment particles from a single turbidity current is usually controlled by a counterbalance between gravity and buoyancy, with the interaction of individual grains being of minor importance. 相似文献
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Governments worldwide rightly regard universities as fundamental to the achievement of many national priorities. But it is the paper’s contention that many misunderstand their true benefit to society. Investments in universities are increasingly based on the belief that the science labs in particular of research-intensive universities can be the source of a continuous stream of people and ideas that will spawn innovative and fast growing companies to form the nexus of the knowledge-based economy. This belief is a source of misconceived policies that offer only ultimate disillusion. It is the totality of the university enterprise that is important, as the only place where that totality of ourselves and our world is brought together, and which makes it the strongest provider of the rational explanation and meaning that societies need. In research, universities create new possibilities; in teaching, they shape new people. Its graduates learn to seek the true meaning of things: to distinguish between the true and the merely seemingly true, to verify for themselves what is stable in that very unstable compound that often passes for knowledge. It is the complex, interacting whole of the university that is the source of the separate economic, social, cultural and utilitarian benefits valued by society. It needs to be understood, valued and managed as a whole. These perceptions are a direct challenge to not only to governments but to university administrators who have been either cowed or seduced into the slipshod thinking that is leading to demands that universities cannot satisfy, whilst obscuring their most important contributions. The challenge to both is to permit autonomy without oppressive accountability, and to give staff and students the freedom to think, speculate and research. These are the very conditions of the personal and collective creativity that are the sources of a university’s deepest benefits to its society. 相似文献