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101.
Koji Matsuki Katsuya Nakatani Takashi Arai Kazuo Ohmura Ryuji Takeuchi Yasushi Arai Shinji Takeuchi 《Journal of Hydrology》2008,360(1-4):217-229
By modifying a previous method with constant elements, we developed a quadratic element method for more accurately estimating groundwater flow by the inversion of tilt data. In this method: (1) a region of groundwater flow is divided into quadratic elements in which the change in groundwater volume per unit volume of rock (Δv) and the Skempton coefficient (B) vary in a quadratic manner with the coordinates, (2) the values of Δv are set to zero at the boundaries of the region of groundwater flow and (3) the sum of the squared second derivatives of Δv is adopted as a constraining condition that is weighted and added to the sum of the squared errors in tilt. First, analyses were performed for a flow model to determine the accuracy of this method for estimating groundwater flow and also to clarify the effect of the assumed size of a region of groundwater flow. These analyses showed that the quadratic element method proposed in this study gives a much better estimation of Δv than the constant element method and that a large region of groundwater flow should be assumed, rather than a small region, since the values of Δv at points outside of the actual region of groundwater flow are estimated to be nearly zero when a large region is assumed while these values are greatly overestimated when an excessively small region is assumed. Finally, the quadratic element method was applied to the site of the Mizunami Underground Research Laboratory in the Tono area, Japan. Inverse analyses were performed for tilt data measured by four tiltmeters with a resolution of 10−9 radians during the excavation of two shafts under the assumption that the rock mass is an isotropic and homogeneous half- space. The results showed that the method proposed in this study reproduced the tilt data very accurately. Thus, the distribution of Δv was estimated without sacrificing the reproducibility of the tilt data. The contour maps of B(1 + ν)Δv (ν: Poisson’s ratio) showed that the heterogeneous flow of groundwater occurred at the site and that groundwater volume decreased mainly in the area surrounded by two faults. The latter result is consistent with the finding obtained by previous investigations that these faults have low permeability in the direction perpendicular to the strike and may act as a flow barrier. 相似文献
102.
Nguyen Phuc Cam Tu Nguyen Ngoc Ha Tokutaka Ikemoto Bui Cach Tuyen Shinsuke Tanabe Ichiro Takeuchi 《Marine pollution bulletin》2008,57(6-12):858
The goal of the present study was to examine the specific bioaccumulation of 22 trace elements in muscle, exoskeleton and hepatopancreas of black tiger shrimp Penaeus monodon from the Mekong River Delta (MRD), and the South Key Economic Zone (SKEZ), South Vietnam. The general tendency in most trace element concentrations among different tissues were hepatopancreas > exoskeleton > muscle. Comparisons of trace element levels in tissues between the two regions showed that concentrations of Se in muscle and As in all three tissues were higher in SKEZ; whereas in MRD, the higher concentrations of most elements such as Mn, Cu, Cd, Ba, Hg, were observed in tissues. These geographical variations in trace element levels may reflect the differences in human activities between the two regions of South Vietnam. The target hazard quotient (THQ) values for trace elements (<1) indicate that local residents are not exposed to potential health risks via the consumption of shrimp. 相似文献
103.
Junichi Takeuchi Naoto Honda Yoshitaka Morikawa Takashi Koike Yutaka Nagata 《Journal of Oceanography》1998,54(1):45-52
Along the southwest coast of the Kii Peninsula, a bifurcation current is regularly observed. By using ADCP data taken on board
the R/V Wakayama of the Wakayama Prefectural Fisheries Experimental Station, characteristics of this bifurcation current are
analyzed. The occurrence frequency of the bifurcation current reaches about 70% in the period from 1988 to 1996. The bifurcation
point appears to be changeable and occurs almost evenly between Cape Ichie and Cape Shionomisaki. The current divergence in
the alongshore direction was also investigated. Positive divergence values dominated in the whole analyzed area, and an onshore
current appears to be dominant along the southwest coast of the Kii Peninsula, except in 1990 when the Kuroshio flowed in
a large meandering path. 相似文献
104.
改进的BTOPMC模型及其在水文模拟中的应用 总被引:2,自引:0,他引:2
In this paper, a grid-based distributed hydrological model BTOPMC (Block-wise use of TOPMODEL) is introduced, which was developed from the original TOPMODEL. In order to broaden the model's application to arid regions, improvement methodology is also implemented. The canopy interception and soil infiltration processes were incorporated into the original BTOPMC to model event-based runoff simulation in large arid regions. One designed infiltration model with application of time compression approximation method is emphasized and validated for improving model's performance for event hydrological simulations with a case study of Lushi River basin. 相似文献
105.
The Permian Akiyoshi Belt, which is the oldest unmetamorphosed accretionary complex in Southwest Japan, plays an important role in understanding the origin of the Japanese Islands; however, its tectonic affinity is still not well constrained. Herein, we present the first Hf isotopic data for U–Pb dated detrital zircons of the Late Permian sandstones in the Akiyoshi Belt. Almost all the late Palaeozoic detrital zircons yielded highly positive ?Hf (t) values compatible with a juvenile source, suggesting that the major provenance of the trench sediments was from the South China block and not from the Bureya‐Jiamusi‐Khanka massif. We propose that in the late Palaeozoic, a block of juvenile lower crust existed outboard of the South China block, and it was being melted during the westward subduction of the Palaeo‐Pacific oceanic plate to produce voluminous volcanic and plutonic rocks with positive ?Hf (t) values. 相似文献
106.
107.
AbstractThis study modified the BTOPMC (Block-wise TOPMODEL with the Muskingum-Cunge routing method) distributed hydrological model to make it applicable to semi-arid regions by introducing an adjustment coefficient for infiltration capacity of the soil surface, and then applied it to two catchments above the dams in the Karun River basin, located in semi-arid mountain ranges in Iran. The application results indicated that the introduced modification improved the model performance for simulating flood peaks generated by infiltration excess overland runoff at a daily time scale. The modified BTOPMC was found to fulfil the need to reproduce important signatures of basin hydrology for water resource development, such as annual runoff, seasonal runoff, low flows and flood flows. However, it was also very clear that effective model use was significantly constrained by the scarcity of ground-gauged precipitation data. Considerable efforts to improve the precipitation data acquisition should precede water resource development planning.Editor D. Koutsoyiannis 相似文献
108.
109.
Abstract International negotiation on the additionality issue of the CDM (Clean Development Mechanism) seems to be proceeding without sufficient information or understanding. Especially apparent is a lack of recognition that the non-additional CERs (certified emission reductions) generated by relaxing the additionality criteria may lead to economic losses for developing countries. This article quantitatively reconfirms the effects of non-additional CERs on the international community, while clarifying that the generation of non-additional CERs in excess of a certain number will eventually lead to negative consequences for developing countries, even if these countries were able to acquire all the non-additional CERs. Furthermore, the Discussion section demonstrates that future system design would significantly affect the benefits of developing countries as well as the overall environmental integrity of the Kyoto mechanisms. 相似文献
110.
T. Miyasaka T. OkuroH. Zhao X. ZhaoX. Zuo K. Takeuchi 《Journal of Arid Environments》2011,75(11):1155-1163
We examined changes in soil properties, crop biomass, and weed communities in the Horqin Sandy Land of China to elucidate cropland degradation. We studied three local cropland types having periods of cultivation of up to 20 years: maize cropland on lowlands without irrigation (nonirrigated lowland), maize cropland on flat sandy lands with irrigation (irrigated flatland), and bean-centered cropland on sand dunes without irrigation (nonirrigated dunes). Soil properties and crop biomass were more degraded in nonirrigated lowland and nonirrigated dunes than in irrigated flatland. Weed communities in the nonirrigated croplands were the type that become established in drier conditions, whereas wetland weeds were more abundant on irrigated flatland. Trends of change in each indicator did not always occur in parallel and differed statistically among the cropland types. Monitoring these indicators within the context of local land-use systems can provide scientific evidence on which to base local management practices or recommendations for change. 相似文献