全文获取类型
收费全文 | 111篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 13篇 |
地球物理 | 25篇 |
地质学 | 20篇 |
海洋学 | 28篇 |
天文学 | 23篇 |
自然地理 | 7篇 |
出版年
2021年 | 1篇 |
2019年 | 2篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 1篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 4篇 |
2007年 | 5篇 |
2006年 | 5篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有119条查询结果,搜索用时 15 毫秒
91.
92.
Noriyuki Matsunaga Hinako Fukushi Yoshikazu Nakada Toshihiko Tanabé Michael W. Feast John W. Menzies Yoshifusa Ita Shogo Nishiyama Daisuke Baba Takahiro Naoi Hidehiko Nakaya Takahiro Kawadu Akika Ishihara Daisuke Kato 《Monthly notices of the Royal Astronomical Society》2006,370(4):1979-1990
We report the result of our near-infrared observations ( JHK s ) for type II Cepheids (including possible RV Tau stars) in galactic globular clusters. We detected variations of 46 variables in 26 clusters (10 new discoveries in seven clusters) and present their light curves. Their periods range from 1.2 d to over 80 d. They show a well-defined period–luminosity relation at each wavelength. Two type II Cepheids in NGC 6441 also obey the relation if we assume the horizontal branch stars in NGC 6441 are as bright as those in metal-poor globular clusters in spite of the high metallicity of the cluster. This result supports the high luminosity which has been suggested for the RR Lyr variables in this cluster. The period–luminosity relation can be reproduced using the pulsation equation assuming that all the stars have the same mass. Cluster RR Lyr variables were found to lie on an extrapolation of the period–luminosity relation. These results provide important constraints on the parameters of the variable stars.
Using Two Micron All-Sky Survey (2MASS) data, we show that the type II Cepheids in the Large Magellanic Cloud (LMC) fit our period–luminosity relation within the expected scatter at the shorter periods. However, at long periods ( P > 40 d, i.e. in the RV Tau star range) the LMC field variables are brighter by about one magnitude than those of similar periods in galactic globular clusters. The long-period cluster stars also differ from both these LMC stars and galactic field RV Tau stars in a colour–colour diagram. The reasons for these differences are discussed. 相似文献
Using Two Micron All-Sky Survey (2MASS) data, we show that the type II Cepheids in the Large Magellanic Cloud (LMC) fit our period–luminosity relation within the expected scatter at the shorter periods. However, at long periods ( P > 40 d, i.e. in the RV Tau star range) the LMC field variables are brighter by about one magnitude than those of similar periods in galactic globular clusters. The long-period cluster stars also differ from both these LMC stars and galactic field RV Tau stars in a colour–colour diagram. The reasons for these differences are discussed. 相似文献
93.
Yasuhito SEKINE Seiji SUGITA Takafumi SHIDO Takashi YAMAMOTO Yasuhiro IWASAWA Toshihiko KADONO Takafumi MATSUI 《Meteoritics & planetary science》2006,41(5):715-729
Abstract— Fischer‐Tropsch catalysis, by which CO and H2 are converted to CH4 on the surface of transition metals, has been considered to be one of the most important chemical reactions in many planetary processes, such as the formation of the solar and circumplanetary nebulae, the expansion of vapor clouds induced by cometary impacts, and the atmospheric re‐entry of vapor condensate due to asteroidal impacts. However, few quantitative experimental studies have been conducted for the catalytic reaction under conditions relevant to these planetary processes. In this study, we conduct Fischer‐Tropsch catalytic experiments at low pressures (1.3 times 10?4 bar ≤ P ≤ 5.3 times 10?1 bar) over a wide range of H2/CO ratios (0.25–1000) using pure iron, pure nickel, and iron‐nickel alloys. We analyze what gas species are produced and measure the CH4 formation rate. Our results indicate that the CH4 formation rate for iron catalysts strongly depends on both pressure and the H2/CO ratio, and that nickel is a more efficient catalyst at lower pressures and lower H2/CO ratios. This difference in catalytic properties between iron and nickel may come from the reaction steps concerning disproportionation of CO, hydrogenation of surface carbon, and the poisoning of the catalyst. These results suggest that nickel is important in the atmospheric re‐entry of impact condensate, while iron is efficient in circumplanetary subnebulae. Our results also indicate that previous numerical models of iron catalysis based on experimental data at 1 bar considerably overestimate CH4 formation efficiency at lower pressures, such as the solar nebula and the atmospheric re‐entry of impact condensate. 相似文献
94.
95.
For countries without sufficient fossil fuel resources such as Japan, climate policies in the mid- to long term need to satisfy requirements not only for decarbonisation but also for energy security in the context of limitations on renewable energies and nuclear power. This study assesses the feasibility of decarbonization pathways to 2050 and their effects on energy security, considering the latest energy and climate policies in Japan using the AIM/Enduse model. The analysis illustrates that deep decarbonization by 2050 is technically feasible even without nuclear power based on three elements: energy efficiency improvements, low-carbon electricity and electrification in end-use sectors. These decarbonization pathways, in the long term, could also contribute to enhanced energy security, reducing import dependency to less than a half of the total primary energy and reducing import bills for fossil fuels by around 70% compared with the current level. Notably, renewable energies could play a strategically significant role in satisfying both climate and energy security requirements. In the mid-term (to 2030), however, although GHG emissions are reduced by 14–20% from 1990 levels, import dependency is relatively stable at today's levels, particularly without the restart of nuclear power. Given the limited potential for renewable energies in the mid-term, it is suggested that the availability of nuclear power will have negative impacts on carbon intensity and energy security, and policies to enhance the security of fossil fuels, including diversification of fuel sources and supply routes, will be required for the foreseeable future.Policy relevanceConsidering the scarcity of indigenous fossil fuel resources and the uncertain availability of nuclear power in Japan, renewable energy could play a strategically significant role in replacing unabated fossil fuels, which would contribute to satisfying both climate and energy security requirements in the long term. However, the renewable energy potential is insufficient to eliminate the requirement for fossil fuels by 2030; therefore the unavailability of nuclear power would affect energy security considerably. Thus, policies in the mid-term would still require enhancement of the energy security of fossil fuels, including the diversification of fuel sources and supply routes, as well as alleviation of the impacts of price volatility. 相似文献
96.
97.
Chemical reactions and volatile supply through hypervelocity impacts may have played a key role for the origin and evolution of both planetary and satellite atmospheres. In this study, we evaluate the role of impact-induced N2 production from reduced nitrogen-bearing solids proposed to be contained in Titan’s crust, ammonium sulfate ((NH4)2SO4), for the replenishment of N2 to the atmosphere in Titan’s history. To investigate the conversion of (NH4)2SO4 into N2 by hypervelocity impacts, we measured gases released from (NH4)2SO4 that was exposed to hypervelocity impacts created by a laser gun. The sensitivity and accuracy of the measurements were enhanced by using an isotope labeling technique for the target. We obtained the efficiency of N2 production from (NH4)2SO4 as a function of peak shock pressure ranging from ∼8 to ∼45 GPa. Our results indicate that the initial and complete shock pressures for N2 degassing from (NH4)2SO4 are ∼10 and ∼25 GPa, respectively. These results suggest that cometary impacts on Titan (i.e., impact velocity vi > ∼8 km/s) produce N2 efficiently; whereas satellitesimal impacts during the accretion (i.e., vi < 4 km/s) produce N2 only inefficiently. Even when using the proposed small amount of (NH4)2SO4 content in the crust (∼4 wt.%) (Fortes, A.D. et al., 2007. Icarus 188, 139-153), the total amount of N2 provided through cometary impacts over 4.5 Ga reaches ∼2-6 times the present atmospheric N2 (i.e., ∼7 × 1020-2 × 1021 [mol]) based on the measured production efficiency and results of a hydrodynamic simulation of cometary impacts onto Titan. This implies that cometary impacts onto Titan’s crust have the potential to account for a large part of the present N2 through the atmospheric replenishment after the accretion. 相似文献
98.
Peng K. Hong Seiji Sugita Yasuhito Sekine Naruhisa Takatoh Tetsuharu Fuse Hideyo Kawakita Eliot F. Young Kosuke Kurosawa Junichi Haruyama Toshihiko Kadono Shunichi Kamata Tomohiko Sekiguchi Hirotomo Noda 《Icarus》2011,214(1):21-29
The Lunar Crater Observation and Sensing Satellite (LCROSS) mission was an impact exploration searching for a volatile deposit in a permanently shadowed region (PSR) by excavating near-surface material. We conducted infrared spectral and imaging observations of the LCROSS impacts from 15 min before the first collision through 2 min after the second collision using the Subaru Telescope in order to measure ejecta dust and water. Such a ground-based observation is important because the viewing geometry and wavelength coverage are very different from the LCROSS spacecraft. We used the Echelle spectrograph with spectral resolution λ/Δλ ∼ 10,000 to observe the non-resonant H2O rotational emission lines near 2.9 μm and the slit viewer with a K′ filter for imaging observation of ejecta plumes. Pre-impact calculations using a homogeneous projectile predicted that 2000 kg of ejecta and 10 kg of H2O were excavated and thrown into the analyzed area immediately above the slit within the field of view (FOV) of the K′ imager and the FOV of spectrometer slit, respectively. However, no unambiguous emission line of H2O or dust was detected. The estimated upper limits of the amount of dust and H2O from the main Centaur impact were 800 kg and 40 kg for the 3σ of noise in the analyzed area within the imager FOV and in the slit FOV, respectively. If we take 1σ as detection limit, the upper limits are 300 kg and 14 kg, respectively. Although the upper limit for water mass is comparable to a prediction by a standard theoretical prediction, that for dust mass is significantly smaller than that predicted by a standard impact theory. This discrepancy in ejecta dust mass between a theoretical prediction and our observation result suggests that the cratering process induced by the LCROSS impacts may have been substantially different from the standard cratering theory, possibly because of its hollow projectile structure. 相似文献
99.
Emission scenario dependencies in climate change assessments of the hydrological cycle 总被引:1,自引:1,他引:0
Hideo Shiogama Naota Hanasaki Yuji Masutomi Tatsuya Nagashima Tomoo Ogura Kiyoshi Takahashi Yasuaki Hijioka Toshihiko Takemura Toru Nozawa Seita Emori 《Climatic change》2010,99(1-2):321-329
Anthropogenic global warming will lead to changes in the global hydrological cycle. The uncertainty in precipitation sensitivity per 1 K of global warming across coupled atmosphere-ocean general circulation models (AOGCMs) has been actively examined. On the other hand, the uncertainty in precipitation sensitivity in different emission scenarios of greenhouse gases (GHGs) and aerosols has received little attention. Here we show a robust emission-scenario dependency (ESD); smaller global precipitation sensitivities occur in higher GHG and aerosol emission scenarios. Although previous studies have applied this ESD to the multi-AOGCM mean, our surprising finding is that current AOGCMs all have the common ESD in the same direction. Different aerosol emissions lead to this ESD. The implications of the ESD of precipitation sensitivity extend far beyond climate analyses. As we show, the ESD potentially propagates into considerable biases in impact assessments of the hydrological cycle via a widely used technique, so-called pattern scaling. Since pattern scaling is essential to conducting parallel analyses across climate, impact, adaptation and mitigation scenarios in the next report from the Intergovernmental Panel on Climate Change, more attention should be paid to the ESD of precipitation sensitivity. 相似文献
100.
A set of simultaneous long-term, deep current measurements was taken using a moored array in the mid-ocean of the western North Pacific near 30°N, 146°E. Five current meters at three stations provided good quality records over 84 days. Low-frequency current fluctuations with meridional dominance are clearly seen in the deep layer records. They are consistent with signals of a mesoscale current fluctuation which has a period of about 100 days, an east-west wave length of about 200 km, and a westward phase propagation with a speed of about 2 cm sec–1. Bottom intensification of the east component of low-frequency current fluctuations is also observed. 相似文献