全文获取类型
收费全文 | 589篇 |
免费 | 23篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 17篇 |
地球物理 | 127篇 |
地质学 | 146篇 |
海洋学 | 139篇 |
天文学 | 135篇 |
综合类 | 9篇 |
自然地理 | 43篇 |
出版年
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 13篇 |
2018年 | 7篇 |
2017年 | 21篇 |
2016年 | 11篇 |
2015年 | 9篇 |
2014年 | 27篇 |
2013年 | 23篇 |
2012年 | 13篇 |
2011年 | 23篇 |
2010年 | 19篇 |
2009年 | 24篇 |
2008年 | 24篇 |
2007年 | 33篇 |
2006年 | 31篇 |
2005年 | 27篇 |
2004年 | 39篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 27篇 |
2000年 | 20篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 12篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1971年 | 3篇 |
排序方式: 共有619条查询结果,搜索用时 828 毫秒
111.
To determine the existence of p-nitrophenol (PNP)-lowering bacteria in intestine of Japanese coastal fish, the gastro-intestinal contents were incubated in Brain Heart Infusion (BHI) broth and minimal medium (MM) broths containing 1 mmol/L PNP at 30 °C for 7 days. Among 26 samples of 19 fish species, 17 samples showed a decrease in PNP of 0.5-0.8 mmol/L in BHI broth, but no decrease was shown in MM broth. Eighteen PNP-lowering bacterial strains were isolated from four fishes. All of the strains were identified as Lactococcus lactis subsp. lactis. Three L. lactis strains JS1-3 isolated from Japanese seabass Lateolabrax japonicus showed the highest PNP-lowering activity (0.44 mmol/L). Optimum temperature and pH for the growth and PNP decreasing corresponded with the marine environment. These results suggested that marine fishes have PNP decreasing bacteria in their intestine. These bacteria might protect host fish from toxicities of PNP and PNP related compounds. 相似文献
112.
This study is intended to evaluate the influence of dynamic bridge-train interaction (BTI) on the seismic response of the
Shinkansen system in Japan under moderate earthquakes. An analytical approach to simulate the seismic response of the BTI
system is developed. In this approach, the behavior of the bridge structure is assumed to be within the elastic range under
moderate ground motions. A bullet train car model idealized as a sprung-mass system is established. The viaduct is modeled
with 3D finite elements. The BTI analysis algorithm is verified by comparing the analytical and experimental results. The
seismic analysis is validated through comparison with a general program. Then, the seismic responses of the BTI system are
simulated and evaluated. Some useful conclusions are drawn, indicating the importance of a proper consideration of the dynamic
BTI in seismic design. 相似文献
113.
H.T.B.M. Petrus Tsuyoshi Hirajima Yuji Oosako Moriyasu Nonaka Keiko Sasaki Takashi Ando 《International Journal of Mineral Processing》2011,98(1-2):15-23
Cenospheres recovery is one of the coal fly ash beneficiations, providing economic as well as environmental benefits. Current techniques, such as lagoon or other wet-separation processes, consume large amounts of water and add to water pollution due to leaching of toxic materials from fly ash. The other possible disadvantage is the need for a wide operational area, which is unsuitable for densely populated countries. As wet-separation processes have some disadvantages, an improved and/or sustainable alternative recovery technique is required. An air classifier is one of the alternative techniques. In this study, two types of air classifiers, namely a closed-type pneumatic separator and a micron separator, have been investigated. In terms of separation efficiency, it was found that the micron separator has the potential to be applied in cenospheres recovery from coal fly ash, giving a Newton's efficiency of 0.44, as compared to a value of about 0.26 for the closed-type pneumatic separator. The cenospheres recoveries of both pieces of equipment at their optimum Newton's efficiencies were similar at over 60 wt.%. The separation performance was further assessed from the particle distributions of the overflow and underflow products obtained from both pieces of equipment, as well as from SEM images. It was found that the lower Newton's efficiency of the closed-type pneumatic separator was due to the re-concentration of fine particles in the underflow product at air-flow rates higher than 2.2 m/s (the underflow product yield was about 55 wt.%).In order to further confirm the applicability of this technique, the micron separator, which had provided higher separation efficiency and cenospheres recovery, was deployed in a cenospheres recovery unit prior to the use of a wet-separation process (float and sink tank). About 80% of the cenospheres was recovered, with an 87.8% reduction in the total mass of fly ash to be separated in the float and sink tank. Consequently, much less water was needed for the process of cenospheres recovery. Moreover, it was also confirmed that the micron separator could yield higher quality fly ashes, that is, fly ash types I and II, from lower feed quality of fly ash type IV, which is the lowest category in commercial classification of fly ash according to JIS A6201. 相似文献
114.
Motoyoshi Oda Shun Chiyonobu Masayuki Torii Takashi Otomo Jumpei Morimoto Yuri Satou Hiroshi Ishikawa Matsuaki Ashikawa Osamu Tominaga 《Journal of Asian Earth Sciences》2011,40(1):84-97
An integrated magnetobiochronology of the Miyazaki Pliocene–Pleistocene succession in the Miyazaki area, southwest Japan, was established using planktic foraminiferal and calcareous nannofossil biostratigraphy together with paleomagnetic data. The upper Miyazaki succession in the northern Miyazaki region can be divided into the Takanabe, Hisamine (redefined), and Higoyashiki (new) Formations, in ascending order. A depositional hiatus between the Hisamine Formation and the Takanabe and/or older formations was also identified based on integrated magnetobiostratigraphy from five sections including the Nagatani River (NGT) section through the uppermost Miyazaki succession. The hiatus, herein called the Hisamine unconformity, is equivalent to the Kurotaki unconformity between the Miura and Kazusa groups of the Boso Peninsula in central Japan. The depositional hiatus recognised in the lower Pleistocene of Pacific coastal areas in southwestern and central Japan may have resulted from tectonic activity associated with a change in the subduction direction of the Philippine Sea plate, which commenced prior to ca. 2.2 Ma. The youngest unit just below the hiatus is the upper part of the Takanabe Formation in the NGT section. The NGT section represents the continuous Late Pliocene to earliest Pleistocene sequence including the Gauss/Matuyama boundary and is here proposed as the type section for the Pliocene/Pleistocene boundary in Japan, which the IUGS ratified as the base of the Gelasian in 2009. 相似文献
115.
Experimental study on prevention of acid mine drainage by silica coating of pyrite waste rocks with amorphous silica solution 总被引:1,自引:1,他引:0
Masahiko Bessho Takaaki Wajima Takuro Ida Takashi Nishiyama 《Environmental Earth Sciences》2011,64(2):311-318
Acid mine drainage (AMD) is a widespread environmental problem associated with working and abandoned mining operations. It
results from the microbial oxidation of pyrite in the presence of water and air, affording an acidic solution that contains
toxic metal ions. Pyrite microencapsulation, utilizing silica coating, is a novel approach for controlling AMD that has been
shown to be very effective in controlling pyrite oxidation. The roles of the solution pH and silica concentration in the formation
mechanism for the AMD-preventing coating were investigated. A silica coating can be formed from silica solution at pH 7, at
which the amount of Fe eluted from pyrite into the solution is small. No coating was formed at other pH values, and the amounts
of eluted Fe were larger than at pH 7, especially at pH 11. The silica coating forms from 2,500 to 5,000 mg/L silica solutions,
but not from 0 or 1,000 mg/L silica solutions. The coating formation rate was slower in the 2,500 mg/L silica solution than
in the 5,000 mg/L silica solution. The formation of silica coating on pyrite surfaces depends on three main steps: formation
of Fe(OH)3 on the surface of pyrite, reaction between Fe(OH)3 and silicate in the solution on the pyrite surface, and growth of the silica layer on the first layer of silica. The best
pH condition to enable these steps was around 7, and the silica coating formation rate can be controlled by the concentration
of silica. 相似文献
116.
117.
118.
Takaaki WAJIMA Shuji OKUDA Youqing CHEN Masahiko BESSHO Takashi NISHIYAMA 《Resource Geology》2000,50(3):191-200
Abstract: Pore spaces and microcracks in representative oil, gas and geothermal reservoir rocks from the Green Tuff region, Japan, were examined using a fluorescent technique. This technique was developed to visualize microscopically pore spaces and microcracks filled with synthetic resin mixed with fluorescent paint under ultraviolet light. Various morphology of pore spaces and microcracks was clearly identified. Spaces in studied reservoir rocks are classified into following three types: pore spaces in matrix, pore spaces in particles, and microcracks. It is observed that valuable oil and gas reservoir rocks relatively include many pore spaces, while microcracks are important for geothermal rocks. Correlation between textural characteristics and porosity or permeability was found in the oil reservoir rocks. Effective permeability depends upon pore spaces in matrix more than upon other components such as pore spaces in particles and microcracks. Looseness in matrix caused by larger grain size of particles is strongly correlated with permeability. Pore spaces play an important role as a reservoir in oil and gas fields, but are less important in geothermal field. Instead, microcracks are important for geothermal reservoir system. 相似文献
119.
Map sheets have been often used as a basic spatial unit for managing spatial data produced from paper maps. This often results
in incompatibility between adjacent map sheets, because spatial objects do not cross the boundaries smoothly and even the
boundaries themselves do not match their neighbors exactly. To solve the problem this paper proposes a computational procedure
for joining separate map sheets to obtain seamless spatial data. Line objects digitized separately in different map sheets
are considered, which are frequently used to represent road networks, gas pipelines, and boundaries of polygon objects. The
procedure consists of three steps: (1) extraction of end nodes, (2) detection of matching nodes, and (3) transformation of
the map sheet. Each step goes interactively so that unexpected errors can be avoided by human observation. To test the validity
of the procedure, map sheets are combined containing the road network data of Tokyo 23-ku area, Japan.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
120.