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1.
Sedimentology is the study of naturally occurring particulate matter with special emphasis on understanding the factors controlling the creation, distribution and accumulation of that matter. Consequently, sedimentology can, and does, embrace geomorphology and climatology, transport mechanisms, depositional environments and lithifaction processes. Its significance lies in the ability of practitioners of the subject—sedimentologists—to determine each and all of the foregoing through the study of samples of sediments and sedimentary rocks. It is, therefore, a basic discipline for the study of past and present environments on Earth, its satellite and its planetary neighbours. The long-standing contributions of two of the nineteenth century founders of the subject, Henry Clifton Sorby (1826–1908) and Johannes Walther (1860–1937), are discussed here. 相似文献
2.
Concern for natural hazard-triggered technological disasters (Natech disasters) in densely populated and industrialized areas
is growing. Residents living in urban areas subject to high natural hazard risk are often unaware of the potential for secondary
disasters such as hazardous materials releases from neighboring industrial facilities, chemical storage warehouses or other
establishments housing hazardous materials. Lessons from previous disasters, such as the Natech disaster during the Kocaeli
earthquake in Turkey in 1999 call for the need to manage low frequency/high consequence events, particularly in today’s densely
populated areas. However, there is little guidance available on how local governments and communities can assess Natech risk.
To add to the problem, local governments often do not have the human or economic resources or expertise to carry out detailed
risk assessments. In this article, we propose a methodology for preliminary assessment of Natech risk in urban areas. The
proposed methodology is intended for use by local government officials in consultation with the public. The methodology considers
possible interactions between the various systems in the urban environment: the physical infrastructure (e.g., industrial
plants, lifeline systems, critical facilities), the community (e.g., population exposed), the natural environment (e.g., delicate
ecosystems, river basins), and the risk and emergency management systems (e.g., structural and nonstructural measures). Factors
related to vulnerability and hazard are analyzed and qualitative measures are recommended. Data from hazardous materials releases
during the Kocaeli, Turkey earthquake of August 17, 1999 are used as a case study to demonstrate the applicability of the
methodology. Limitations of the proposed methodology are discussed as well as future research needs.
相似文献
Norio OkadaEmail: |
3.
The study of the Kuroshio in the East China Sea and the currents east of the Ryukyu Islands 总被引:3,自引:0,他引:3
In this study, the inverse method is used to compute the Kuroshio in the East China Sea and southeast of Kyushu and the currents east of the Ryukyu Islands, on the basis of hydrographic data obtained during September-October, 1987 by R/V Chofu Maru. The results show that: (1)A part of the Taiwan Warm Current has a tendency to converge to the shelf break; (2) the Kuroshio flows across the section C3 (PN) with a reduced current width, and the velocity of the Kuroshio at the section C3 increases and its maximum current speed is about 158 cm/s, and its volume transport here is about 26×106m3/s; (3) the Kuroshio has two current cores at the sections C3 (PN) and B2 (at the Tokara Strait); (4) the currents east of the Ryukyu Islands are found to flow northward over the Ryukyu Trench during September-October, 1987. The velocities of the currents are not strong throughout the depths. At the section C2 east of the Ryukyu Islands, the maximum current speed is at the 699 m levei and its magnitude is 25 cm/s, and i 相似文献
4.
Joji Ishizaka Yasuhisa Kitaura Yasuharu Touke Hiroaki Sasaki Akihiko Tanaka Hiroshi Murakami Toshikazu Suzuki Kazumi Matsuoka Hideaki Nakata 《Journal of Oceanography》2006,62(1):37-45
High resolution SeaWiFS data was used to detect red tide events that occurred in the Ariake Sound, Japan, a small embayment
known as one of the most productive areas in Japan. SeaWiFS chlorophyll data clearly showed that a large red tide event, which
damaged seaweed (Nori) cultures, started early in December 2000 in Isahaya Bay, expanded to the whole sound and persisted
to the end of February 2001. The monthly average of SeaWiFS data from May 1998 to December 2001 indicated that the chlorophyll
peaks appeared twice a year, in early summer and in fall, after the peaks of rain and river discharge. The SeaWiFS data showed
that the red tide event during 2000–2001 winter was part of the fall bloom; however, it started later and continued significantly
longer than other years. Satellite ocean color data is useful to detect the red tide; however the algorithms require improvement
to accurately estimate chlorophyll in highly turbid water and in red tide areas. 相似文献
5.
The recent sea-ice reduction in the Arctic Ocean is not spatially uniform, but is disproportionally large around the Northwind
Ridge and Chukchi Plateau compared to elsewhere in the Canada Basin. In the Northwind Ridge region, Pacific Summer Water (PSW)
delivered from the Bering Sea occupies the subsurface layer. The spatial distribution of warm PSW shows a quite similar pattern
to the recent ice retreat, suggesting the influence of PSW on the sea-ice reduction. To understand the regionality of the
recent ice retreat, we examine the dynamics and timing of the delivery of the PSW into this region. Here, we adopt a two-layer
linearized potential vorticity equation to investigate the behavior of Rossby waves in the presence of a topographic discontinuity
in the high latitude ocean. The analytical results show a quite different structure from those of mid-latitude basins due
to the small value of β. Incident barotropic waves excited by the sea-ice motion with large annual variation can be scattered
into both barotropic and baroclinic modes at the discontinuity. Since the scattered baroclinic Rossby wave with annual frequency
cannot propagate freely, a strong baroclinic current near the topographic discontinuity is established. The seasonal variation
of current near the topographic discontinuity would cause a kind of selective switching system for shelf water transport into
the basin. In our simple analytical model, the enhanced northward transport of summer water and reduced northward transport
of winter water are well demonstrated. The present study indicates that these basic dynamics imply that a strengthening of
the surface forcing during winter in the Canada Basin could cause sea-ice reduction in the Western Arctic through the changes
of underlying Pacific Summer Water. 相似文献
6.
Koji Suzuki Akira Hinuma Hiroaki Saito Hiroshi Kiyosawa Hongbin Liu Toshiro Saino Atsushi Tsuda 《Progress in Oceanography》2005,64(2-4):167
To verify the hypothesis that the growth of phytoplankton in the Western Subarctic Gyre (WSG), which is located in the northwest subarctic Pacific, is suppressed by low iron (Fe) availability, an in situ Fe fertilization experiment was carried out in the summer of 2001. Changes over time in the abundance and community structure of phytoplankton were examined inside and outside an Fe patch using phytoplankton pigment markers analyzed by high-performance liquid chromatography (HPLC) and flow cytometry (FCM). In addition, the abundance of heterotrophic bacteria was also investigated by FCM. The chlorophyll a concentration was initially ca. 0.9 μg l−1 in the surface mixed layer where diatoms and chlorophyll b-containing green algae (prasinophytes and chlorophytes) were predominant in the chlorophyll biomass. After the iron enrichment, the chlorophyll a concentration increased up to 9.1 μg l−1 in the upper 10 m inside the Fe patch on Day 13. At the same time, the concentration of fucoxanthin (a diatom marker) increased 45-fold in the Fe patch, and diatoms accounted for a maximum 69% of the chlorophyll biomass. This result was consistent with a microscopic observation showing that the diatom Chaetoceros debilis had bloomed inside the Fe patch. However, chlorophyllide a concentrations also increased in the Fe patch with time, and reached a maximum of 2.2 μg l−1 at 5 m depth on Day 13, suggesting that a marked abundance of senescent algal cells existed at the end of the experiment. The concentration of peridinin (a dinoflagellate marker) also reached a maximum 24-fold, and dinoflagellates had contributed significantly (>15%) to the chlorophyll biomass inside the Fe patch by the end of the experiment. Concentrations of 19′-hexanoyloxyfucoxanthin (a prymnesiophyte marker), 19′-butanoyloxyfucoxanthin (a pelagophyte marker), and alloxanthin (a cryptophyte marker) were only incremented a few-fold increment inside the Fe patch. On the contrary, chlorophyll b concentration reduced to almost half of the initial level in the upper 10 m water column inside the Fe patch at the end of the experiment. A decrease with time in the abundance of eukaryotic ultraphytoplankton (<ca. 5 μm in size), in which chlorophyll b-containing green algae were possibly included was also observed by FCM. Overall, our results indicate that Fe supply can dramatically alter the abundance and community structure of phytoplankton in the WSG. On the other hand, cell density of heterotrophic bacteria inside the Fe patch was maximum at only ca. 1.5-fold higher than that outside the Fe patch. This indicates that heterotrophic bacteria abundance was little respondent to the Fe enrichment. 相似文献
7.
Simulation of Formation and Spreading of Salinity Minimum Associated with NPIW Using a High-Resolution Model 总被引:1,自引:2,他引:1
A series of numerical experiments were conducted with a high-resolution (eddy-permitting) North Pacific model to simulate
the formation and spreading of the salinity minimum associated with the North Pacific Intermediate Water (NPIW). It was found
that two factors are required to simulate a realistic configuration of the salinity minimum: a realistic wind stress field
and small-scale disturbances. The NCEP reanalyzed wind stress data lead to better results than the Hellerman and Rosenstein
wind stress data, due to the closer location of the simulated Oyashio and Kuroshio at the western boundary. Small-scale disturbances
formed by relaxing computational diffusivity included in the advection scheme promote the large-scale isopycnal mixing between
the Oyashio and Kuroshio waters, simulating a realistic configuration of the salinity minimum. A detailed analysis of the
Oyashio water transport was carried out on the final three-year data of the experiment with reduced computational diffusivity.
Simulated transport of the Kuroshio Extension in the intermediate layer is generally smaller than the observed value, while
those of the Oyashio and the flow at the subarctic front are comparable to the observed levels. In the Oyashio-Kuroshio interfrontal
zone the zonally integrated southward transport of the Oyashio water (140–155°E) is borne by the eddy activity, though the
time-mean flow reveals the existence of a coastal Oyashio intrusion. In the eastern part (155°E–180°) the zonally integrated
transport of the Oyashio water indicates a southward peak at the southern edge of the Kuroshio Extension, which corresponds
to the branching of the recirculating flow from the Kuroshio Extension.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
9.
There is the natural habitat of polyps of the common jellyfish Aurelia aurita in the Taniyama area, Kagoshima Bay. We examined the attachment substrata, density, colony structure and strobilation of
the polyps. The polyps were observed only on the horizontal undersurface of floating piers. They attached specifically to
Mytilus shells, solitary ascidians, calcareous polychaete tubes, muddy amphipod tubes and the gap space that fouling animals peeled
off the substrata. The polyp colonies were distributed in patches. Spatial distribution patterns of the polyps within their
colonies were uniform. Strobilation occurred during late December to March, when water temperatures were 16–17°C, and a large
number of ephyrae were released. An increase in man-made structures such as floating piers in coastal areas may lead to bloomings
of Aurelia aurita medusae.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
10.
The mineralogy of eight gravity cores recovered between Sierra Leone and 25°W longitude has been examined in an investigation
of the provenance of the recent sediments in the eastern Equatorial Atlantic. X-ray analyses show that the principal mineral
components are calcite, quartz, feldspar, kaolinite, illite and montmorillonite. One core taken from the upper continental
slope off Freetown also contains gibbsite, a product of intense tropical weathering. Biogenic material forms the dominant
component of most sections of the cores but it is clear from the abundance of quartz, kaolinite and freshwater diatoms that
an aeolian supply of continental detritus has been important in the formation of the recent sediment cover. A significant
contribution from volcanic sources can be recognised to the west of the Sierra Leone Rise. The occurrence of calcareous turbidites
in two cores from the St. Paul's Fracture Zone and from the basin west of the Sierra Leone Rise appears to be a reflection
of recent tectonic activity. 相似文献