全文获取类型
收费全文 | 770篇 |
免费 | 26篇 |
国内免费 | 25篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 106篇 |
地球物理 | 190篇 |
地质学 | 220篇 |
海洋学 | 221篇 |
天文学 | 38篇 |
综合类 | 17篇 |
自然地理 | 16篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 14篇 |
2019年 | 12篇 |
2018年 | 36篇 |
2017年 | 38篇 |
2016年 | 52篇 |
2015年 | 52篇 |
2014年 | 49篇 |
2013年 | 49篇 |
2012年 | 42篇 |
2011年 | 68篇 |
2010年 | 60篇 |
2009年 | 50篇 |
2008年 | 33篇 |
2007年 | 33篇 |
2006年 | 44篇 |
2005年 | 35篇 |
2004年 | 24篇 |
2003年 | 24篇 |
2002年 | 11篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 13篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有821条查询结果,搜索用时 15 毫秒
31.
Hwan-Sung Ji Kangseok Hwang Jung Hwa Choi Hyung-Kee Cha Jin-Koo Kim 《Ocean Science Journal》2017,52(2):293-299
Pre-metamorphic leptocephali of Pisodonophis sangjuensis (n = 91, 10.4?90.2 mm in total length, TL) were collected in the East China Sea for the first time. Pre-metamorphic leptocephali of P. sangjuensis, which were identified using mitochondrial DNA cytochrome c oxidase subunit I gene (mtDNA COI), are characterized by various combinations of morphological characters: 8 moderate to pronounced gut loops with the kidney terminating on the 6-7th loops; and 8 subcutaneous pigment patches on the tail just ventral to the notochord. Pisodonophis sangjuensis leptocephali were more numerously collected offshore than inshore around Jeju Island. The smallest leptocephali (< 15.0 mm TL) were collected from the south far from Jeju Island, and the largest leptocephali (> 100.0 mm TL) were collected from around Jeju Island and the southern coast of Korea. Our findings indicate that P. sangjuensis spawns offshore south of Jeju Island that is an area associated with high water temperature, and then the hatched leptocephali are transported to Jeju Island or the southern coast of Korea by the Tsushima Warm Current. 相似文献
32.
Hyun-Sung Yang Do-Hyung Kang Heung-Sik Park Kwang-Sik Choi 《Ocean Science Journal》2017,52(4):519-526
Widely distributed from the northern coast of Vietnam to the northern Japan, the limpet Cellana grata (Gould, 1859) occurs commonly on the south and east coasts of Korea. Despite their wide distribution range, few studies have investigated the annual gametogenesis and reproductive effort of C. grata. In an attempt to understand the reproductive physiology of the limpet, we investigated the annual gametogenesis and reproductive effort of C. grata from Ulleungdo Island off the east coast of Korea. Histology revealed that the gonial mitosis commenced in January, as the female exhibited small oogonia (10–40 μm) in the follicle. From March to June, the oocyte size increased dramatically, and fully mature eggs (110–170 μm in diameter) appeared in early summer. First spawning males and females were observed in July, as the surface seawater temperature (SST) reached 22.1°C. The spawning male and females could be observed until the end of December. Gonad somatic index (GSI), a ratio of gonad mass to the total tissue weight, of the male ranged from 0.6 (April) to 17.9 (July), while the female GSI varied from 1.0 (February) to 18.3 (July). GSI of male and female declined rapidly from July to August, suggesting that the major purse of the spawning at the study site was between July and August. Our study suggested that the commercial catch of C. grata during July and August must be suspended at Ulleungdo Island, in order to protect the spawning limpets, which enhances C. grata recruitment and the population. 相似文献
33.
To understand the temporal and spatial variation of the prokaryotic community in the East Sea, their composition was determined by polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE)-sequencing techniques. The investigations were conducted twice annually in 2007 and 2009 in coastal and offshore stations. Prokaryotic abundance (PA), leucine incorporation rate, and other environmental parameters were also measured. By using the DGGE approach, we obtained 283 bacterial sequences and 160 archaeal sequences. The most frequently detected bacterial phylotypes during the investigations belonged to Alphaproteobacteria, Gammaproteobacteria, and Bacteroidetes. However, their relative compositions differed in time and space. Although Alphaproteobacteria and Bacteroidetes were the dominant groups in the surface water in May 2007 and in May and October 2007, Gammaproteobacteria was dominant in mesopelagic samples. However, Gammaproteobacteria was overwhelmingly dominant in most samples in August 2009. Although Deltaproteobacteria was rarely found as a dominant bacterial group, it occupied the highest fraction in a mesopelagic sample in October 2007. Epsilonproteobacteria also showed a similar trend, although its maximal dominance was found in a mesopelagic sample in August 2009. The archaeal community was dominated overwhelmingly by members of the Euryarchaeota in most of the investigations. However, Nitrosopumilales was dominant in aphotic samples in August 2009. Further, their spatiotemporal composition at the family level changed more dynamically in the East Sea. These temporal and spatial distributions of the prokaryotic community were influenced mainly by seawater temperature and depth in the East Sea. 相似文献
34.
In this study, 36 fish species were collected from three coastal cities in Korea to investigate levels and patterns of six arsenicals (arsenite: As (III), arsenate: As (V), arsenocholine: AsC, arsenobetaine: AsB, monomethylarsonic acid: MMA, and dimethylarsinic acid: DMA). The levels of ∑6 As in the different fish species varied substantially, ranging from 0.02 μg As/g ww (Islaeli carp) to 9.65 μg As/g ww (Skate ray) with a median of 0.40 μg As/g ww. All the arsenicals in marine fishes showed higher levels than those in freshwater fishes due to fish feed living in saline water. Overall, marine carnivorous fishes seem to be more contaminated with arsenic. For all the fish samples, AsB (mean fraction: 90.6%) was dominant among the six arsenicals, indicating biomethylation of inorganic arsenic and accumulation of AsB. Fish species with high water contents showed elevated levels of As (III), but there was no further significant correlations between arsenicals and water/lipid contents. Concentrations of As (V) were significantly lower than those of As (III), which implies that As (V) is reduced during biomethylation of inorganic arsenic. Consequently, we hypothesize that the toxicity of arsenic (mainly derived from As (III)) can be increased by the reduction of As (V), especially for the fish species with higher water contents. 相似文献
35.
Bonggil Hyun Se-Jong Ju Ah-Ra Ko Keun-Hyung Choi Seung Won Jung Pung-Guk Jang Min-Chul Jang Chang Ho Moon Kyoungsoon Shin 《Ocean Science Journal》2016,51(3):333-342
Little is known regarding how harmful algal bloom species respond to different temperatures in terms of fatty acid production. This study examined the effects of temperature on the growth rates, cell volumes, and fatty acid concentrations and compositions of four harmful algal bloom species (HABs), Akashiwo sanguinea, Alexandrium tamarense, Chattonella ovata, and Prorocentrum minimum. The HABs species were cultured at 15, 20, 25, and 30°C in a nutrient-enriched medium. Three of the species maintained optimal growth rates over a wide range of temperatures, but A. tamarense did not. The cell volumes of each species showed little change over the temperature range. The total fatty acid concentrations in A. sanguinea, A. tamarense and C. ovata decreased as the temperature increased, but P. minimum showed no trend in this respect. Polyunsaturated fatty acids (PUFAs), the key biochemical components that maintain cell membrane fluidity and which are associated with toxicity, decreased in both concentration and proportion of total fatty acids as temperature increased, except in A. sanguinea, in which the proportion of PUFAs to the total fatty acids increased. These reductions in PUFA concentration and proportion could reduce cell membrane fluidity and toxicity in HABs; however, enhanced growth and/or ruptured cells, which are considered more toxic than intact cells, could compensate for the reduced per-cell toxicity. This phenomenon might impact on the marine ecosystem and aquaculture industry. 相似文献
36.
This study has evaluated the vertical bearing capacity by conducting static load tests for noise-free and vibration-free screw pretensioned spun high-strength concrete (PHC) piles installed using two different methods (end-squirting shoe and pre-boring methods). Vertical bearing capacity differences seem to occur due to the displacement of soils near the external circumference of a pile, depending on the installation method. A method by which to evaluate the bearing capacity of screw concrete piles is suggested by considering the equations that already have been used to calculate the bearing capacity of piles. Based on static load tests and analysis, the pile installed using the end-squirting shoe method was assumed to be a bored pile and it was reasonable to use the equation proposed by the Japanese Geotechnical Society. At the same time, the pile installed using the pre-boring method was deemed a low soil displacement pile and so it was reasonable to apply the equations proposed for calculating the bearing capacity of the driven pile suggested by the Architectural Institute of Japan. 相似文献
37.
38.
Free spanning analysis of offshore pipelines 总被引:1,自引:0,他引:1
H. S. Choi 《Ocean Engineering》2001,28(10)
A rigorous procedure was established on the free span analysis of offshore pipelines. The closed form solutions of the beam–column equation, considering tension and compressive force, were derived for the various possible boundary conditions. The solutions can be used to find the natural frequencies of the free spans using the energy balance concept. The results can be applied to improve the current design codes. The improved procedure will yield more realistic calculations of the allowable free span lengths of offshore pipelines. Some calculations are included to present the sensitivity of the axial forces on the allowable free spanning lengths. 相似文献
39.
Byung-Hak Cho Dong-Soon Yang Shin-Yeol Park Kyung-Shik Choi Do-Hwan Lee Seung-Hyun Byun Hoon Jung 《Ocean Engineering》2011,38(2-3):436-443
The modeling and control of a variable liquid-column oscillator having a liquid filled U-tube with air chambers at its vertical columns are presented. As an ocean wave energy extracting device, the structure of the variable liquid-column oscillator (VLCO) is analogous to that of the tuned liquid-column damper used to suppress oscillatory motion in large structures like tall buildings and cargo ships. However, owing to an air spring effect caused by the dynamic pressure of air chambers, the amplitude of response of the VLCO becomes significantly amplified for a desired wave period. The governing equations for the motion of VLCO structure under wave excitation and the motion of liquid with an air spring effect caused by an air–liquid interaction are described by a series of nonlinear differential equations. A set of control parameters for extracting maximum power from various wave conditions is determined for the efficient operation of the VLCO. It is found that the effect of the air spring has an important role to play in making the oscillation of the VLCO match with the ocean wave. In this way, the VLCO provides the most effective mode for extracting energy from the ocean wave. 相似文献
40.
Park Sojung Choi Mansik Jang Dongjun Joe Dongjin Park Kyunggue 《Ocean Science Journal》2020,55(1):49-67
Ocean Science Journal - In this study, we investigated the spatial and temporal distribution and sources of dissolved and particulate heavy metals in Masan Bay, an area that for a long time has... 相似文献