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排序方式: 共有379条查询结果,搜索用时 15 毫秒
161.
Tetsuya Nishikawa Yutaka Hori Satoshi Nagai Kazutaka Miyahara Yukinobu Nakamura Kazuhiro Harada Minoru Tanda Takehiko Manabe Kuninao Tada 《Estuaries and Coasts》2010,33(2):417-427
Long-term monitoring of water quality and phytoplankton was conducted at 19 sampling stations in Harima-Nada, eastern Seto Inland Sea, Japan for 35 years from 1973 to 2007. There were two significant long-term changes, an increase in winter water temperatures of 0.042°C year?1, and a decrease in dissolved inorganic nitrogen (DIN) from about 10 μM in the 1970s to ~5 μM in the late 1990s due to the reduction in nutrient inputs. DIN concentrations and total phytoplankton cell density were both higher during the 1970s to the early 1980s and then exhibited a significant decrease in the mid 1980s and remained relatively constant thereafter. Diatoms were the dominant phytoplankton group (>90%) over the 35-year period, and there was a dramatic shift from Skeletonema dominance (~70%) to Chaetoceros in the mid 1980s. This shift in diatom species may be attributed to differences in the life cycle of Skeletonema and Chaetoceros and the response to the decrease in DIN concentration. 相似文献
162.
Akiko Murakami-Kitase Takamoto Okudaira Jun Inoue 《Environmental Earth Sciences》2010,59(8):1723-1729
Spheroidal carbonaceous particles (SCPs) are produced by the high-temperature combustion of fossil fuels and are emitted to
the atmosphere. Previous studies are divided regarding whether SCPs derived from the combustion of various fossil fuels can
be identified based on their surface morphologies and chemical compositions. In this study, we examined the surface morphology
and chemical composition of SCPs in sediment core samples collected from Osaka Bay, Japan, with the aim of evaluating the
usefulness of SCPs morphology in identifying their origin. Scanning electron microscope (SEM) observations reveal three distinct
surface morphologies: (1) smooth, (2) rough and irregular, and (3) convoluted and layered. According to a morphological classification
scheme proposed previously, the former two morphologies correspond to coal-derived carbon particles, whereas the latter corresponds
to oil-derived carbon particles. In terms of the chemical compositions of the particles with different morphologies, as analyzed
by energy-dispersive spectroscopy, linear discriminant analysis reveals that the two fuel types can be distinguished. An overall
success rate of >90% of reference of morphologically classified material correctly assigned to two groups that are chemically
different each other, indicating a relationship between surface morphology and chemical composition. This result suggests
that morphological characterization based on conventional SEM observations is useful in identifying the source fuel of SCPs. 相似文献
163.
Ayumi Asai Takaaki Yokoyama Masumi Shimojo Satoshi Masuda Kazunari Shibata 《Journal of Astrophysics and Astronomy》2006,27(2-3):167-173
We report a detailed examination about the relationship between the evolution of the Hα flare ribbons and the released magnetic
energy during the April 10 2001 flare. In the Hα images, several bright kernels are observed in the flare ribbons. We identified
the conjugated foot-points, by analyzing the lightcurves at each Hα kernels, and showed their connectivities during the flare.
Then, based on the magnetic reconnection model, we calculated quantitatively the released energy by using the photospheric
magnetic field strengths and separation speeds of the Hα flare ribbons. Finally, we examined the downward motions which are
observed at the Hα kernels. We found that the stronger the red-asymmetry tends to be associated with the brighter the Hα kernel. 相似文献
164.
Eri Hirakawa Akiko Murakami-Kitase Takamoto Okudaira Jun Inoue Hideo Yamazaki Shusaku Yoshikawa 《Environmental Earth Sciences》2011,64(3):833-840
Spheroidal carbonaceous particles (SCPs) are produced by the high-temperature combustion of fossil fuels and emitted in to
the atmosphere. The distribution and concentration of SCPs in sediments have been used as a proxy for the distribution of
pollutants emitted to the atmosphere. However, the effect on the distribution of SCPs due to industrial activity at nearby
industrial cities is yet to be quantified. To clarify the origin of SCPs of ~20 μm in size that are preserved in sediments,
we evaluated the abundance, surface morphology, and chemical composition of SCPs in sediment core samples recovered from industrial
cities in Japan (Tokyo, Osaka, and Nagasaki) and China (Beijing), with the cities being located at least ~500 km away from
each other. Vertical profiles of SCP concentration in sediment cores from the Japanese cities and Beijing are different, reflecting
the contrasting industrial histories of the two countries. The SCPs from different cities show contrasting morphological and
chemical characteristics, suggesting that ~20 μm SCPs in sediments from the industrial cities could represent the local combustion
history in detail, as the influx of local SCPs is dominant at such sites. 相似文献
165.
Strain localization developing inside soft rock specimens is examined through experimental observation and numerical simulation. In the experimental study, soft rock specimens are sheared at different strain rates under plane strain conditions and deformation and strain localization characteristics are analysed. Transition of localization mode from highly localized mode for higher strain rate to distributed and diffused mode of strain localization for lower strain rates was observed. In the numerical study, simulations of plane strain compression tests are carried out at different strain rates by using an overstressed‐type elasto‐viscoplastic model in finite element computations. The role of strain rates on setting gradients of strain fields across shear band is clarified. The probable mechanism for transition of localization mode is discussed. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
166.
167.
Y. Ueda K. Yamaoka J.E. Grove M. McCollough P. Durouchoux J. Rodriguez F. Mirabel J. Swank M. Feroci P. Casella A.J. Castro-Tirado C. Sánchez-Fernández S. Chaty H. Castaneda K. Kohno V. Dhawan S.A. Trushkin K. Ebisawa T. Kotani H. Inoue 《Astrophysics and Space Science》2001,276(1):25-28
We report results from multiwavelength observations of the microquasarGRS 1915+105 performed during the 2000 April campaign. This is one ofthe biggest campaigns ever made for this source covering the broadband from radio to γ-rays. Multiwavelength light curves compiledfrom all the data reduced up to date and broad band spectra obtainedwith ASCA and RXTE are presented. 相似文献
168.
Satoshi Hinata 《Solar physics》1987,109(2):321-333
As the electrical conductivity along the magnetic field in solar atmosphere is large, parallel electric fields have been neglected in most investigations. We will first demonstrate their importance for post-flare loops, and then introduce a model for them which takes into account the effect of parallel electric fields. The electric field calculated from the model is consistent with the electric field observed by Foukal et al. (1983). 相似文献
169.
170.
Terrigenous loading into enclosed water bodies has been blamed for eutrophic conditions marked by massive algal growth and subsequent hypoxia due to decomposition of dead algal cells. This study aims to describe the eutrophication and hypoxia processes in a semi-enclosed water body lying near a big metropolis. Phosphorus mass balance in a small inlet, Ohko Inlet, located at the head of Hiroshima Bay, Japan, was quantified using a numerical model. Dissolved inorganic phosphorous inflow from Kaita Bay next to the inlet was five times higher than that from terrigenous load, which may cause an enhancement of primary production. Therefore, it was concluded that not only the reduction of material load from the land and the suppression of benthic flux are needed, but also reducing the inflow of high phosphorus and oxygen depleted water from Kaita Bay will form a collective alternative measure to remediate the environmental condition of the inlet. 相似文献