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111.
José Augusto Costa Gonçalves Jorge Carvalho de Lena José Fernando Paiva Hermínio Arias Nalini Jr Janice Cardoso Pereira 《Environmental Geology》2007,53(4):785-793
In the city of Ouro Preto (MG), water catchment for public supply originates from superficial drainage, springs, old abandoned
mines and some driven wells. In the rocks of the region, As is originally found in gold-enriched sulphide-bearing mineral
deposits. The weathering process introduces As into the hydrological system by dissolution of this element into the leachate.
Measurement of the As content in the groundwater of some catchments was carried out during 1 year and these measurements demonstrated
high As content—up to 224 μg L−1 of As(V)—during the rainy season (the maximum concentration limit according to World Health Organization is 10 μg L−1). Lower values were observed during the dry season and in some sampling stations, As was not even detected. The As concentration
variability during 1 year shows a strict and direct relationship to seasonal and hydrological conditions. For city authorities,
responsible for public water supply, it is necessary to perform a complete inventory of the water sources used and constantly
monitor the As content in the water. 相似文献
112.
Zeferino Joel Carvalho Maria Rosrio Lopes Ana Rita Jesus Rosrio Afonso Maria Jos Freitas Liliana Carvalho Jos Martins Chamin Helder I. 《Hydrogeology Journal》2021,29(6):2267-2283
Hydrogeology Journal - Nitrate contamination of groundwater is an important public health issue worldwide. For environmental and public health reasons, water should not contain more than... 相似文献
113.
André Andrian Padial Priscilla Carvalho Sidinei Magela Thomaz Solana Meneghel Boschilia Roberta Becker Rodrigues Josilaine Taeco Kobayashi 《Aquatic Sciences - Research Across Boundaries》2009,71(4):389-398
Aquatic macrophytes produce large amounts of organic matter and have an essential structuring role in floodplains. This process highlights the importance of this community to aquatic biodiversity maintenance. We investigated the role of a flood disturbance on the response of macrophyte assemblages in regional and local structuring in the Upper Paraná River floodplain. Plant species were recorded before (November 2006) and after (March 2007) an uncommon increase in water level caused by the El Niño South Oscillation, which is considered a disturbance. Samples were taken in lakes and backwaters located in the floodplain and connected to three distinct rivers (that differentiate three sub-systems). Species richness and the assemblage structure of macrophyte patches underwent significant changes after the flood disturbance, depending on the specific sub-system (rivers) to which the lakes were connected. In addition, flood disturbance had a strong impact on community organization at the local scale. However, regionalization with respect to sub-systems remained significant after the flood disturbance. Our results emphasize the importance of connection to the river on macrophyte community composition and richness, and suggest that flood events in the Upper Paraná River floodplain disrupt community organization only at fine (local) scales. 相似文献
114.
Taha Rabeh Jorge Miguel Miranda Joao Carvalho Andrei Bocin 《Geophysical Prospecting》2009,57(3):447-459
The study area is located in the Sinai Peninsula, which is considered one of the most promising regions for oil resources. Three different tectonic forces affect the area in the triple junction structures associated with the opening of the Gulf of Suez and the strike slip movement along the Gulf of Aqaba. The main goal of this work is to model the structure of the basement rocks in the study area using magnetic methods. To achieve this, a high-resolution land magnetic survey was acquired and the results were combined with existing seismic reflection data. The magnetic interpretation was carried out using the analytical signal, horizontal gradient, Euler and Werner deconvolution and 3D magnetic modelling methods. We concluded that most of the deduced structures are trending in N–S, N35°–N45° west and E–W directions. The Aqaba trend (N15°–N25° east) is barely noticeable. The depth to the basement rocks ranges from 1 km to more than 2 km below sea level and these results are in agreement with the available well log data. In addition, interpretation of seismic reflection sections was carried out and compared with overlapping magnetic profiles interpreted using Euler deconvolution. They show that the sedimentary section was affected by the basement tectonics, with faults extending from the basement upwards through the sedimentary cover. These faults constitute good potential structural traps for oil accumulation. 相似文献
115.
Edmo J.D. Campos Swapna Mulkherjee Alberto R. Piola Flavio M.S. de Carvalho 《Continental Shelf Research》2008
Riverine waters bring to seas a variety of suspended materials, which are ultimately deposited on the shelf or exported to the deep ocean. Investigation of the mineralogical contents of these continental-borne constituents on seafloors may reveal valuable information about the environmental conditions in the drainage basin. In this note we report results of X-ray diffraction and other analysis of sediments in bottom samples collected on the continental shelf under influence of the Plata River and the Patos Lagoon, in South America. The analysis reveals that non-clay materials are mostly concentrated south of 33°S, while clay sediments are relatively more abundant further north. We propose that such distributions are controlled by the circulation pattern and water mass distribution of the lower and upper layers, respectively. 相似文献
116.
P. P. Avelino J. P. M. de Carvalho 《Monthly notices of the Royal Astronomical Society》1999,310(4):1170-1174
We study the growth of linear perturbations induced by a generic causal scaling source as a function of the cosmological parameters h , and . We show that for wavenumbers k ≳0.01 h Mpc−1 the spectrum of density and velocity perturbations scales in a similar way to that found in inflationary models with primordial perturbations. We show that this result is independent of the more-or-less incoherent nature of the source, the small-scale power spectrum of the source and of deviations from scaling that naturally occur at late times if . 相似文献
117.
C. E. V. Carvalho A. R. C. Ovalle C. E. Rezende M. M. Molisani M. S. M. B. Salomão L. D. Lacerda 《Environmental Geology》1999,37(4):297-302
Temporal and spatial variability of particulate metal concentrations (Cu, Cr, Zn, Mn and Fe) were investigated in the lower
drainage basin of the Paraíba do Sul River. The results showed that the spatial variability was not important for all the
studied metals, however, temporal variations seems to be considerable. In general, two distinct behaviors were observed for
particulate heavy metals: (1) metal concentration increase together with water flow (Fe and Cu) and (2) concentration decrease
with increasing water flux (Zn, Cr and Mn). The Fe and Cu behavior is probably due to the strong association of these metals
with surface runoff, although their sources seem to be distinct. Iron probably originates from the regional soils rich in
iron oxides, and Cu is possibly associated to the large-scale use of copper fungicides in the sugar cane plantations. The
opposite trend observed for Zn, Cr and Mn probably reflects the importance of the industrial and urban effluents as a secondary
source of these elements for the system. Their behavior is probably associated with the dilution effect caused by the input
of a suspended matter poor in these metals originated from the surface runoff during the rainy season.
Received: 4 March 1998 · Accepted: 30 June 1998 相似文献
118.
R. Constantino M.B. Gaspar J. Tata-Regala S. Carvalho J. Cúrdia T. Drago R. Taborda C.C. Monteiro 《Marine environmental research》2009,67(2):89-99
This study aimed to assess the potential effects of clam dredging and the subsequent recovery of the benthic environment. Two experimental areas located at 6 and 18 m depth were established in order to analyse whether impacts and recovery of benthic environment are depth-related. Study areas were located within an area closed to dredging and two different plots were established at both depths. One of the plots was subjected to intense clam dredge-fishing, while the other was undisturbed and therefore used as control. Sampling followed a BACI design, with samples for macrobenthic, meiobenthic and sediment particle size analysis being taken by SCUBA divers from both areas before and after fishing stress. For both depths, impacts on the benthic environment were very low resulting in high recovery rates. Nevertheless, at shallower depths communities demonstrated a faster recovery. It was shown that depending on the faunal component used as a bioindicator, different results can be observed. Generally deposit-feeding organisms with scales or chitinous plates and vermiform shape (mainly crustaceans, polychaetes and ophiuroids), without external protection, were the most affected by dredging, while some polychaetes without external protection and with a carnivorous feeding mode seemed to be enhanced by fishing. The low level of perturbations induced by the dredging activities was comparable to the impact of surface waves on the bottom, as experiments were undertaken in wave-dominated environments. The coexistence of storm events during the study period proved to have similar or even more deleterious effects on the benthic environment. It appears that communities from hydrodynamic fishing grounds that are well adapted to natural physical stress are not highly affected by dredging. 相似文献
119.
Carvalho PS Kalil Dda C Novelli GA Bainy AC Fraga AP 《Marine environmental research》2008,66(1):205-207
Naphthalene (NAP) and phenanthrene (PHE) effects on Salminus brasiliensis, a carnivorous freshwater fish, were investigated using behavioral tests. Larval stages of S. brasiliensis were exposed to water concentrations of 0, 0.04 mg/l, 0.20mg/l and 0.50mg/l for naphthalene and 0, 0.01 mg/l, 0.05 mg/l and 0.1mg/l for phenanthrene during two developmental phases. The prey fish Prochilodus lineatus were not exposed. Visual acuity was measured at the end of phase 2 in individual S. brasiliensis, which were also tested at the end of each phase for number of attacks on prey, number of prey captured, prey capture efficiency, and distance swam. Vision was impaired by PHE exposure, as acuity angles increased in exposed fish. At Stage I 2.3+/-1.2 prey were captured with 46% efficiency in controls compared to 0.4+/-0.3 prey captured with 13.4% efficiency in fish exposed to 0.05 mg PHEl(-1), the LOEL for both endpoints. At Stage II 4.0+/-1.1 preys were captured in controls compared to 2.5+/-0.9 preys captured in fish exposed to 0.01 mg PHEl(-1), the LOEL. Stage II control fish captured prey with 70% efficiency compared to 30% efficiency at Stage II fish exposed to 0.05 mg PHEl(-1), the LOEL. Distance swam was not affected by either NAP or PHE exposure. The exposure of larval stages of S. brasiliensis to realistic water concentrations of PHE impairs foraging skills and could affect recruitment of the species. 相似文献
120.
Miguel Cortés Sánchez Francisco J. Jiménez Espejo María D. Simón Vallejo Juan F. Gibaja Bao António Faustino Carvalho Francisca Martinez-Ruiz Marta Rodrigo Gamiz José-Abel Flores Adina Paytan José A. López Sáez Leonor Peña-Chocarro José S. Carrión Arturo Morales Muñiz Eufrasia Roselló Izquierdo José A. Riquelme Cantal Rebecca M. Dean Emília Salgueiro Rafael M. Martínez Sánchez Nuno F. Bicho 《Quaternary Research》2012,77(2):221-234
New data and a review of historiographic information from Neolithic sites of the Malaga and Algarve coasts (southern Iberian Peninsula) and from the Maghreb (North Africa) reveal the existence of a Neolithic settlement at least from 7.5 cal ka BP. The agricultural and pastoralist food producing economy of that population rapidly replaced the coastal economies of the Mesolithic populations. The timing of this population and economic turnover coincided with major changes in the continental and marine ecosystems, including upwelling intensity, sea-level changes and increased aridity in the Sahara and along the Iberian coast. These changes likely impacted the subsistence strategies of the Mesolithic populations along the Iberian seascapes and resulted in abandonments manifested as sedimentary hiatuses in some areas during the Mesolithic–Neolithic transition. The rapid expansion and area of dispersal of the early Neolithic traits suggest the use of marine technology. Different evidences for a Maghrebian origin for the first colonists have been summarized. The recognition of an early North-African Neolithic influence in Southern Iberia and the Maghreb is vital for understanding the appearance and development of the Neolithic in Western Europe. Our review suggests links between climate change, resource allocation, and population turnover. 相似文献