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161.
162.
Low-flow indices have been determined from long-term daily streamflow data for 13 catchments in Dongjiang Basin in southern China. The Brutsaert-Nieber method was applied to estimate catchment-scale effective groundwater parameters; representative values were 4.5?×?10?4 m2 s?1 for the hydraulic diffusivity; 3.19?×?10?5 m2 s?1/2 for the hydraulic desorptivity; 2.27?×?10?4 m s?1 for the hydraulic conductivity; and 0.2617 for the drainable porosity. The response constants correlate well with the total stream length and catchment area. Solutions of the linearised Boussinesq equation were used to guide the development of regional multivariate regression models for estimating low-flow indices from the catchment-scale effective parameters. Results showed that these catchments exhibit similar low-flow characteristics. The 7-day lowest average streamflows with return periods of 10 and 2 years (7Q10 and 7Q2) are highly correlated with the catchment-scale response constants. The low-flow ratio Q95/Q50 (ratio of daily streamflow exceeded 95 and 50% of the time, respectively) varied between 0.3 and 0.5, indicating a high proportion of groundwater in the streamflow. The advantage of the regional regression model is its conceptual basis and use of the catchment-scale effective parameters. The method has the potential to be applied to ungauged catchments for estimating low-flow statistics from stream length and catchment area. 相似文献
163.
The effects of persistent organic pollutants on the aquatic environment still can hardly be assessed. Therefore, ready biodegradability is a desired key characteristic of chemicals. Accordingly, biodegradation testing is of utmost importance and is a vital part within the risk assessment for organic chemicals. In the closed bottle test (CBT; OECD 301D) the degree of biological degradation of a chemical is assessed by monitoring the oxygen consumption so far with a Clark electrode as standard method. However, this method is time‐consuming, laborious and led to frequent fluctuations of the test results, which limited their validity. Due to these shortcomings, an optical system that enables contact‐free measuring of the oxygen concentration in a closed bottle, based on dynamic luminescence quenching, was examined. The test results were compared to those obtained with the “classical” electrochemical technique (Clark electrode). At first, a basic standard for the handling of the new instrument in the laboratory was developed. Then possible influencing factors, reliability, comparability, and reproducibility of the test results were investigated by running the CBTs in parallel with the electrode and optode method. The findings proved the new optode method to be unambiguously superior to the electrode technique. The frequency of fluctuations of the test results and time and effort necessary for the test run could considerably be reduced. The degradation kinetics of the test substances could be followed easily in the CBT by increasing the measuring points without much additional effort. 相似文献
164.
Waleed M. M. Mahmoud Nareman D. H. Khaleel Ghada M. Hadad Randa A. Abdel‐Salam Annette Haiß Klaus Kümmerer 《洁净——土壤、空气、水》2013,41(9):907-916
Sulfonamides (SAs) are one of the most frequently used antibiotics. SAs have been found in various environmental compartments. If SAs are not degraded in the environment, they can affect bacteria by their antibiotic properties and contribute to bacterial antibiotic resistance. Therefore, the biodegradability of 11 SAs (sulfanilamide, sulfaguanidine monohydrate, sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethoxypyridazine, sulfachloropyridazine, sulfamethazine, sulfamethoxazole, and sulfadimethoxine) was studied. For this purpose, the Closed Bottle Test (CBT, OECD 301D) was performed, which includes a toxicity control. In order to monitor the environmental fate of the parent compound and to check for transformation products, a simple, efficient, and reliable HPLC–UV method for the simultaneous determination of these SAs has been developed. Acetonitrile and water (with 0.1% formic acid) were used as mobile phase solvents for gradient elution. The method was validated in terms of precision, detection and quantitation limits, selectivity, and analytical solution stability. In the CBT, none of these SAs was readily biodegradable. The HPLC–UV analysis confirmed that no degradation of any SA took place. In the toxicity control, these SAs showed no toxic effect in the used concentration of environmental bacteria applied in the test. 相似文献
165.
Rockfall Hazard Analysis From Discrete Fracture Network Modelling with Finite Persistence Discontinuities 总被引:2,自引:1,他引:1
Cédric Lambert Klaus Thoeni Anna Giacomini Davide Casagrande Scott Sloan 《Rock Mechanics and Rock Engineering》2012,45(5):871-884
Developing an accurate representation of the rock mass fabric is a key element in rock fall hazard analysis. The orientation, persistence and density of fractures control the volume and shape of unstable blocks or compartments. In this study, the discrete fracture modelling technique and digital photogrammetry were used to accurately depict the fabric. A volume distribution of unstable blocks was derived combining polyhedral modelling and kinematic analyses. For each block size, probabilities of failure and probabilities of propagation were calculated. A complete energy distribution was obtained by considering, for each block size, its occurrence in the rock mass, its probability of falling, its probability to reach a given location, and the resulting distribution of energies at each location. This distribution was then used with an energy–frequency diagram to assess the hazard. 相似文献
166.
Karl?Hans?Wedepohl Klaus?SimonEmail author 《Contributions to Mineralogy and Petrology》2012,164(4):693-696
During the Variscan orogeny in Central Europe, partial melting in the lower continental crust formed granitic magmas, which intruded into the upper crust and left compounds of Ca (plus Eu2+), Mg, etc. in the lower crust. From the late Paleozoic decomposition of the tonalitic upper crust, sedimentary graywackes were produced reflecting the composition of this crust. The repeated reworking of the sedimentary cover caused the formation of sands. Sandstones as their products of consolidation contain increasing fractions of quartz and decreasing feldspar from Carboniferous and Triassic to Cretaceous age. A distinct negative Eu anomaly characterizes the majority of these rocks. The latter is imprinted by the Variscan magmatism. Quartz as used for numerous Medieval wood ash glasses is marked for its Central European origin by a distinct negative Eu anomaly in contrast to many soda glasses produced outside Germany mostly with a small or none Eu anomaly. 相似文献
167.
168.
Paleo- and Neoproterozoic magmatic and tectonometamorphic evolution of the Isla Cristalina de Rivera (Nico Pérez Terrane, Uruguay) 总被引:1,自引:0,他引:1
Pedro Oyhant?abal Martin Wagner-Eimer Klaus Wemmer Bernhard Schulz Robert Frei Siegfried Siegesmund 《International Journal of Earth Sciences》2012,101(7):1745-1762
The Isla Cristalina de Rivera crystalline complex in northeastern Uruguay underwent a multistage magmatic and metamorphic evolution. Based on SHRIMP U–Pb zircon, Th–U–Pb monazite (CHIME-EPMA method) and K–Ar age data from key units several events can be recognized: (1) multistage magmatism at 2,171–2,114?Ma, recorded on zircon of the granulitic orthogneisses and their 2,093–2,077?Ma overgrowths; (2) a distinct amphibolite facies metamorphism at ~1,980?Ma, recorded by monazite; (3) greenschist facies reworking and shearing at ca. 606?Ma (monazite and K–Ar on muscovite) along the Rivera Shear Zone, and finally (4) intrusion of the post-tectonic Sobresaliente and Las Flores granites at around 585?Ma. Lithological similarities, geographic proximity and coeval magmatic and metamorphic events indicate a similar tectonometamorphic evolution for the Isla Cristalina de Rivera, the Valentines Block in Uruguay and the Santa María Chico Granulitic Complex in southern Brazil, since at least 2.1?Ga. 相似文献
169.
Ekaterina Vasyukova Wolfgang Uhl Fuad Braga Claudia Simões Tânia Baylão Klaus Neder 《Environmental Earth Sciences》2012,65(5):1587-1599
Drinking water production at three waterworks was evaluated with respect to variable weather conditions in the Brasília Distrito
Federal. Results of the investigation revealed that seasonal variations in rainfall play an important role in influencing
the quality of the surface water sources used for drinking water production in the district. In most surface sources, particles
and apparent colour are likely to originate from erosion during rain events. This represents the primary challenge facing
waterworks, notably when the raw water qualities of the sources to be treated at one facility differ by one order of magnitude,
as well significantly varying from one season to the next. Treatment efficiencies in terms of turbidity, apparent colour and
dissolved organic carbon (DOC) removal were evaluated. Drinking water quality was found to be significantly influenced by
raw water quality at all considered treatment plants. With regard to DOC removal, treatment was most efficient in waterworks
which treated raw water with high percentages of biopolymers and humics. Most dissolved organics were removed by coagulation.
Finally, conclusions are drawn on how to better cope with challenges facing drinking water production in a tropical climate.
The first of these recommendations is the introduction of online turbidity and dissolved organic matter monitoring in order
to optimise the coagulation process for the removal of these two parameters. A combination of different coagulants could also
be considered for this process. Additional more sophisticated improvements to process stability, such as determination of
floc characteristics, introduction of artificial neural networks or the eventual upgrade of the treatment train using membrane
filtration, are also suggested. 相似文献
170.
Developing coastal adaptation to climate change in the New York City infrastructure-shed: process, approach, tools, and strategies 总被引:1,自引:0,他引:1
Cynthia Rosenzweig William D. Solecki Reginald Blake Malcolm Bowman Craig Faris Vivien Gornitz Radley Horton Klaus Jacob Alice LeBlanc Robin Leichenko Megan Linkin David Major Megan O��Grady Lesley Patrick Edna Sussman Gary Yohe Rae Zimmerman 《Climatic change》2011,106(1):93-127
While current rates of sea level rise and associated coastal flooding in the New York City region appear to be manageable by stakeholders responsible for communications, energy, transportation, and water infrastructure, projections for sea level rise and associated flooding in the future, especially those associated with rapid icemelt of the Greenland and West Antarctic Icesheets, may be outside the range of current capacity because extreme events might cause flooding beyond today??s planning and preparedness regimes. This paper describes the comprehensive process, approach, and tools for adaptation developed by the New York City Panel on Climate Change (NPCC) in conjunction with the region??s stakeholders who manage its critical infrastructure, much of which lies near the coast. It presents the adaptation framework and the sea-level rise and storm projections related to coastal risks developed through the stakeholder process. Climate change adaptation planning in New York City is characterized by a multi-jurisdictional stakeholder?Cscientist process, state-of-the-art scientific projections and mapping, and development of adaptation strategies based on a risk-management approach. 相似文献