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41.
North America's Atlantic Coast has been a focus of human settlement and subsistence for millennia, but sea‐level rise, sedimentation, and other processes pose significant challenges for archaeological research. Radiocarbon dating of 31 shell middens near the Rhode River Estuary, Maryland provides an opportunity to evaluate human land use, settlement, and cultural chronologies on the Chesapeake Bay. Sixty calibrated radiocarbon dates on eastern oyster (Crassostrea virginica) shell and charcoal demonstrate that Native Americans, colonial, and historic peoples harvested oysters and other shellfish from at least 3200 years ago through the 19th century. The number of dated sites increases during the Late Woodland period after about 1000 cal yr B.P., a factor probably related to greater site visibility and preservation, as well as increased human exploitation of the watershed. Accumulation rates for five of the shell middens provide preliminary indications that some of the sites accumulated rapidly suggesting, along with other evidence, that many of the region's shell middens were logistical or perhaps seasonal camps. Our study demonstrates the importance of regional watershed surveys and radiocarbon dating programs to help build and refine cultural chronologies in coastal regions threatened by sea‐level rise and other processes.  相似文献   
42.
The terrigenous fraction of sediments recovered from Walvis Ridge, SE Atlantic Ocean, reveals a history of southwestern African climate of the last 300 kyr. End-member modelling of a data set of grain-size distributions (n=428) results in three end members. The two coarsest end members are interpreted as eolian dust, the third end member as hemipelagic mud. The ratio of the two eolian end members reflects the eolian grain size and is attributed to the intensity of the SE trade winds. Trade winds were intensified during glacials compared to interglacials. Changes in the ratio of the two eolian end members over the hemipelagic one are interpreted as variations in southwestern African aridity. Late Quaternary southwestern African climate was relatively arid during the interglacial stages and relatively humid during the glacial stages, owing to meridional shifts in the atmospheric circulation system. During glacials the polar front shifted equatorward, resulting in a northward displacement of the zone of westerlies, causing increased rainfall in southwestern Africa. The equatorward shift of the polar front is coupled with an increase of the meridional pressure gradient, leading to enhanced atmospheric circulation and increased trade-wind intensity.  相似文献   
43.
Using an empirical study of a political protest, this paper examines a set of interdependent contracts symbolizing both the nodes of scalar interaction and the hegemonic nodes of resistance. The study focuses on a contentious political campaign aimed at the City of Cincinnati, a recycling facility, and a day labor temp agency initiated by contracted day laborers who hand-sorted garbage from recycling materials and suffered from adverse working conditions and alleged wage violations. A discussion of the rise of contingent labor through implementation of neoliberal deregulation policies is integrated with Jürgen Habermas' concepts of the lifeworld and the system providing an explanatory framework for understanding lifeworld colonization through flexible labor practices and the subsequent impetus behind the contentious political campaign. Using survey data, the shared lifeworld of day laborers is described. The study also examines how the position of protest participants affected the tactics and outcomes of the contestation. [Key words: day labor, contingent labor, living wage ordinances, Habermas.]  相似文献   
44.
A preliminary diagnosis is given for Paravireia pistus sp. nov.  相似文献   
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The present study investigated the applicability of integrated polychaete-fish culture for fish waste removal to offset negative impact induced by organic benthic enrichment. A field study demonstrated that deposition rate was significantly higher underneath the fish farm than that in control area. The material settling under the farm was characterized by a high amount of fish feces (45%) and uneaten feed (27%). Both feeding rate (FR) and apparent digestibility rate (ADR) increased with decreasing body weight, as was indicated by significantly a higher rate observed for the groups containing smaller individuals in a lab study. The nutrient in fresh deposited material (De) was higher than that in sediments collected under the farm (Se), resulting in lower feces production but higher apparent digestibility rate for the De group as feeding rate was similar. Consequently, higher nutrient removal efficiency was observed in the De group. A mass balance approach indicated that approximately 400–500 individuals m?2 is required for removing all waste materials deposited underneath the fish farm, whereas abundance can be lower (about 300–350 individuals m?2) when only the fish waste needs to be removed. The results showed that a significant amount of waste had been accumulated in the fish cages in Sanggou Bay. The integration of fish with P. aibuhitensis seems promising for preventing organic pollution in the sediment and therefore is an effective strategy for mitigating negative effect of fish farms. Thus such integration can become a new IMTA (integrated multi-trophic aquaculture) model in Sanggou Bay.  相似文献   
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More than 1000 seismic events in northern Europe at distances of up to 400  km from the detecting network are located using an optimization method in which the global minimum of the traveltime function residuals is searched for using an Interval Arithmetic (IA) method. Epicentres are determined using P waves detected by the Finnish national seismic network: up to 15 stations were used in the analysis. The IA results coincide with locations provided by the University of Helsinki bulletins with a median location bias of 7.6  km.
  A second data set of 59 explosions in the Siilinjärvi mine in central Finland was examined in detail, because the locations of the explosions were known exactly. In this case, the median difference of IA locations was 3.8  km from the average location of mine explosions, while all 59 events were located within 9  km of the 'true' epicentres. The corresponding median error of the University of Helsinki locations was smaller (3.2  km), but some Helsinki locations were well over 10  km from the mine. The convergence towards the global optimum using interval arithmetic was fast when compared with the conventional least-squares approaches for epicentre determinations.  相似文献   
50.
Sample cylinders of two galena ore hand specimens from Braubach, Germany were axially shortened in the strain rate range 5 × 10−5 s−1–5 × 10−7 s−1 at a confining pressure of 200 (300) MPa and at temperatures of 20 °C–600 °C. Neutron diffraction analyses of the crystallographic preferred orientation (texture) were carried out before and after experimental deformation on the same sample cylinder. Up to a deformation temperature of 300 °C and a strain rate of 5 × 10−6 s−1 a more or less complete <110> fiber texture develops, the strength of the fiber texture only depending on strain and the strength of the original preferred orientation. At slower strain rate and higher temperature, there is a distinct decrease of the fiber texture development. Diffusional mass transfer starts to become a significant deformation mechanism. Deformation at 500 °C changes the original texture only slightly, which indicates a rapid increase of importance of diffusional flow processes. The alteration of the accompanying sulfosalts indicates that the temperature is high enough for the movement of atoms. The microstructure only reveals remarkable deformation structures at higher strains and in areas of locally higher stresses. Received: 10 June 1997 / Accepted: 14 May 1998  相似文献   
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