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991.
M. Chandra Singh P. Kundal R. A. S. Kushwaha 《Journal of the Geological Society of India》2010,76(6):573-586
Oligocene-Miocene deposits of Bhuban and Boka Bil Formations, Surma Group, Manipur Western Hill consist of well preserved
ichnofossil assemblages. These formations are represented by eight lithofacies such as Massive sandstone (Sm), Rippled marked
argillaceous sandstone (Sr), Wavy laminated sandstone-siltstone-silty shale (Sw), Laminated shale (Fl), Massive mudstone (Fm),
Trough cross-bedded sandstone (St), Lenticular laminated sandstonesiltstonesilty shale (Sll) and Laminated to massive sandstone-siltstone
(Ssc). Fifteen ichnospecies were identified, which further categories into Skolithos, Cruziana, and Skolithos/Cruziana ichnofacies. Overall distribution pattern and behavioural nature of the ichnoassemblage and sedimentological attributes suggests
that the sediments of Bhuban and Boka Bil Formations were deposited under frequent fluctuating sea level, moderate to strong
energy condition, subtidal to lower intertidal environment, rich in organic nutrients. 相似文献
992.
Long-term soil moisture dynamics derived from GNSS interferometric reflectometry: a case study for Sutherland,South Africa 总被引:3,自引:0,他引:3
Sibylle Vey Andreas Güntner Jens Wickert Theresa Blume Markus Ramatschi 《GPS Solutions》2016,20(4):641-654
Soil moisture is a geophysical key observable for predicting floods and droughts, modeling weather and climate and optimizing agricultural management. Currently available in situ observations are limited to small sampling volumes and restricted number of sites, whereas measurements from satellites lack spatial resolution. Global navigation satellite system (GNSS) receivers can be used to estimate soil moisture time series at an intermediate scale of about 1000 m2. In this study, GNSS signal-to-noise ratio (SNR) data at the station Sutherland, South Africa, are used to estimate soil moisture variations during 2008–2014. The results capture the wetting and drying cycles in response to rainfall. The GNSS Volumetric Water Content (VWC) is highly correlated (r 2 = 0.8) with in situ observations by time-domain reflectometry sensors and is accurate to 0.05 m3/m3. The soil moisture estimates derived from the SNR of the L1 and L2P signals compared to the L2C show small differences with a RMSE of 0.03 m3/m3. A reduction in the SNR sampling rate from 1 to 30 s has very little impact on the accuracy of the soil moisture estimates (RMSE of the VWC difference 1–30 s is 0.01 m3/m3). The results show that the existing data of the global tracking network with continuous observations of the L1 and L2P signals with a 30-s sampling rate over the last two decades can provide valuable complementary soil moisture observations worldwide. 相似文献
993.
The three-dimensional ionospheric tomography (3DCIT) algorithm based on Global Navigation Satellite System (GNSS) observations have been developed into an effective tool for ionospheric monitoring in recent years. However, because the rays that come into or come out from the side of the inversion region cannot be used, the distribution of the rays in the edge and bottom part of the inversion region is scarce and the electron density cannot be effectively improved in the inversion process. We present a three-dimensional tomography algorithm with side rays (3DCIT-SR) applying the side rays to the inversion. The partial slant total electron content (STEC) of side rays in the inversion region is obtained based on the NeQuick2 model and GNSS-STEC. The simulation experiment results show that the algorithm can effectively improve the distribution of GNSS rays in the inversion region. Meanwhile, the iteration accuracy has also been significantly improved. After the same number of iterations, the iterative results of 3DCIT-SR are closer to the truth than 3DCIT, in particular, the inversion of the edge regions is improved noticeably. The GNSS data of the International GNSS Service (IGS) stations in Europe are used to perform real data experiments, and the inversion results show that the electron density profiles of 3DCIT-SR are closer to the ionosonde measurements. The accuracy improvement of 3DCIT-SR is up to 56.3% while the improvement is more obvious during the magnetic storm compared to the case of a calm ionospheric state . 相似文献
994.
The Mahu lake, the third deepest lake in China, is located on the west bank of the Jinsha River in Leibo county, Sichuan Province. It is a dammed lake created by an old landslide on the ancient Huanglang river, a tributary on the west bank of the Jinsha River. Previous studies (Wang and Lu in J Mt Res S1:44–47, 2000) suggested that this landslide was caused by an earthquake approximately 372 ka (Middle Pleistocene), during which a few hundreds of million cubic meters of debris were deposited between 1177 and 900 m a.s.l. (above sea level), covering an area of around 15 km2. Our further investigations, including geodetic survey, borehole drilling, and field reconnaissance, combining with five chronological data, have made some new discoveries at this site. First, the toe of the landslide extends from 900 m a.s.l. down to 320 m a.s.l., i.e., the local bed elevation of the contemporary Jinsha River. Second, the area of the landslide deposits is 17.3 km2 with a volume of 2.38 km3, much larger than the previous estimation. Thus, it should be one of the largest known landslides in China. And the lower elevation of the landslide’s toe also rules out the possibility that it is a hanging valley on the ancient Huanglang river. Our work suggests that this landslide was created by five events according to the overlapping characteristics of the deposits and five chronological data, which are old than 52,600 years, old than 16,000 years, old than 15,500 years, 5800 years, and old than 4200 years, respectively. 相似文献
995.
Saverio Romeo Lucio Di Matteo Laura Melelli Corrado Cencetti Walter Dragoni Andrea Fredduzzi 《Landslides》2017,14(4):1457-1465
On October 30, 2016, a seismic event and its aftershocks produced diffuse landslides along the SP 209 road in the Nera River Gorge (Central Italy). Due to the steep slopes and the outcropping of highly fractured and bedded limestone, several rockfalls were triggered, of which the main event occurred on the slope of Mount Sasso Pizzuto. The seismic shock acted on a rock wedge that, after an initial slide, developed into a rockfall. The debris accumulation blocked the SP 209 road and dammed the Nera River, forming a small lake. The river discharge was around 3.6 m3/s; the water overtopped the dam and flooded the road. By a preliminary topographic survey, we estimated that the debris accumulation covers an area of about 16,500 m2, while the volume is around 70,000 m3. The maximum volume occupied by the pre-existing talus mobilized by the rockfall is about 20% of the total volume. Besides blocking the road, the rockfall damaged a bridge severely, while, downstream of the dam, the water flow caused erosion of a road embankment. A rockfall protection gallery, a few hundred meters downstream of the dam, was damaged during the event. Other elastic nets and rigid barriers were not sufficient to protect the road from single-block rockfalls, with volumes around 1–2 m3. Considering the geological and geomorphological conditions, as well as the high seismicity and the socioeconomic importance of the area, a review of the entire rockfall protection systems is required to ensure protection of critical infrastructure and local communities. 相似文献
996.
Growth of trees at their altitudinal and latitudinal range limits is expected to increase as climate warms, but trees often exhibit unexplained spatial and temporal variation in climate-growth responses, particularly in alpine regions. Until this variability is explained, predictions of future tree growth are unlikely to be accurate. We sampled Picea glauca (white spruce) growing at forest and tree line on north and south aspects in two mountain ranges of southwest Yukon to determine how and why ring-width patterns vary between topographic settings, and over time. We used multivariate statistical analysis to characterize variation in ring-width patterns between topographic factors and time periods, and calculated correlations between ring-width indices and climate variables to explain this variation. Ring-width patterns varied more between mountain ranges than elevations or aspects, particularly in recent decades when ring-widths increased in one mountain range but not the other. Growth responses to summer temperature were notably weaker during warmer time periods, but growth was not positively correlated to summer precipitation, suggesting trees may not be suffering from temperature-induced drought stress. Rather, ring-width indices began responding positively to spring snow depth after 1976. We conclude that tree growth is unlikely to increase in synchrony with rising air temperatures across subarctic tree lines in southwest Yukon. Instead, they may decline in areas that are prone to thin snowpacks or rapid spring runoff due to the negative influence warming springs will have on snow depth and, consequently, early growing season soil moisture. 相似文献
997.
ARGO hydrographic profiles, two hydrographic transects and satellite measurements of air–sea exchange parameters were used
to characterize the properties and seasonal heat budget variations of the Surface Mixed Layer (SML) south of Africa. The analysis
distinguishes the Subtropical domain (STZ) and the Subantarctic Zone (SAZ), Polar Frontal Zone (PFZ) and Antarctic Zone (AZ)
of the Antarctic Circumpolar Current. While no Subantarctic Mode Water forms in that region, occurrences of deep SML (up to
∼450 m) are observed in the SAZ in anticyclones detached from the Agulhas Current retroflection or Agulhas Return Current.
These are present latitudinally throughout the SAZ, but preferentially at longitudes 10–20° E where, according to previous
results, the Subtropical Front is interrupted. Likely owing to this exchange window and to transfers at the Subantarctic Front
also enhanced by the anticyclones, the SAZ shows a wide range of properties largely encroaching upon those of the neighbouring
domains. Heat budget computations in each zone reveal significant meridional changes of regime. While air–sea heat fluxes
dictate the heat budget seasonal variability everywhere, heat is mostly brought through lateral geostrophic advection by the
Agulhas Current in the STZ, through lateral diffusion in the SAZ and through air–sea fluxes in the PFZ and AZ. The cooling
contributions are by Ekman advection everywhere, lateral diffusion in the STZ (also favoured by the ∼10° breach in the Subtropical
Front) and geostrophic advection in the SAZ. The latter likely reflects an eastward draining of water warmed through mixing
of the subtropical eddies. 相似文献
998.
In order to meet the challenge of climate change while allowing for continued economic development, the world will have to
adopt a net zero carbon energy infrastructure. Due to the world’s large stock of low-cost fossil fuels, there is strong motivation
to explore the opportunities for capturing the CO2 that is produced in the combustion of fossil fuels and keeping it out of the atmosphere. Three distinct sets of technologies
are needed to allow for climate neutral use of fossil fuels: (1) capture of CO2 at concentrated sources like electric power plants, future hydrogen production plants and steel and cement plants; (2) capture
of CO2 from the air; and (3) the safe and permanent storage of CO2 away from the atmosphere. A strong regime of carbon accounting is also necessary to gain the public’s trust in the safety
and permanence of CO2 storage. This paper begins with an extensive overview of carbon capture and storage technologies, and then presents a vision
for the potential implementation of carbon capture and storage, drawing upon new ideas such as air capture technology, leakage
insurance, and monitoring using a radioactive isotope such as C-14. These innovations, which may provide a partial solution
for managing the risks associated with long-term carbon storage, are not well developed in the existing literature and deserve
greater study. 相似文献
999.
Anthropogenic platinum,palladium and rhodium concentrations in road dusts from Hyderabad city,India 总被引:1,自引:0,他引:1
Ramavati Mathur V. Balaram M. Satyanarayanan S. S. Sawant S. L. Ramesh 《Environmental Earth Sciences》2011,62(5):1085-1098
This paper presents the first study of accessing the Pt, Pd and Rh levels in road dusts collected from Hyderabad city, India,
as these metals, emitted from automobile catalytic converters, are accumulating in the environment causing concern about human
health and ecological risks. Samples were analyzed by ICP-MS following preconcentration by NiS-fire assay and Te coprecipitation.
Pt (1.5–43 ng/g), Pd (1.2–58 ng/g) and Rh (0.2–14.2 ng/g) concentrations obtained were above upper crust values, but were
lower when compared with several other cities around the world. Dust samples from road junctions and traffic signals with
heavy and erratic traffic flow showed higher PGE levels than those from roads with low and free flow traffic suggesting that
traffic flow conditions greatly influenced emission of PGE from the catalyst. Significant correlation of Pt, Pd and Rh indicate
a common source for these metals. PGE were also positively correlated with Ce, Zr, Hf and Y. These positive inter-element
correlations identified traffic as the main source of PGE emission to the roadway environment. The results obtained indicate
to an appreciable increase in auto catalyst-derived PGE. In consideration of the adverse effects of PGE, monitoring their
level and transformation paths is of prime importance. 相似文献
1000.
Nitrate pollution of groundwater in Toyserkan,western Iran 总被引:3,自引:2,他引:3
Mohsen Jalali 《Environmental Earth Sciences》2011,62(5):907-913
A total of 95 groundwater samples were collected from Toyserkan, western Iran to assess the chemical composition and nitrate
(NO3
−) status of groundwater. The most prevalent water type is Ca–HCO3 followed by water types Ca–Mg–HCO3. In comparison with the World Health Organization (WHO) drinking water guideline of 50 mg l−1 for NO3
−, a total of nine wells (9.5%) showed higher concentrations. In 36% of samples (34) NO3
− concentration was low (<20 mg l−1), and in 53.7% of samples (51), in the range of 20–50 mg l−1. The samples were classified into four groups based on NO3
− and chloride (Cl−) concentrations. Of the samples, 40% were classified as group 4 and were relatively high in Cl− and NO3
− (Cl− > 47 mg l−1, NO3
− > 27 mg l−1). The high correlation between NO3
− and Cl− (r = 0.86, p < 0.01) is consistent with a manure source, resulting from the practice of adding salt to animal feed. Pollution of groundwaters
appeared to be affected by the application of inorganic fertilizer at greater than agronomic rates, Cl-salt inputs, and irrigation
practice. 相似文献