全文获取类型
收费全文 | 905篇 |
免费 | 26篇 |
国内免费 | 15篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 63篇 |
地球物理 | 189篇 |
地质学 | 227篇 |
海洋学 | 179篇 |
天文学 | 179篇 |
综合类 | 8篇 |
自然地理 | 85篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 14篇 |
2019年 | 20篇 |
2018年 | 26篇 |
2017年 | 19篇 |
2016年 | 21篇 |
2015年 | 19篇 |
2014年 | 27篇 |
2013年 | 53篇 |
2012年 | 33篇 |
2011年 | 33篇 |
2010年 | 38篇 |
2009年 | 38篇 |
2008年 | 42篇 |
2007年 | 44篇 |
2006年 | 35篇 |
2005年 | 23篇 |
2004年 | 23篇 |
2003年 | 20篇 |
2002年 | 26篇 |
2001年 | 15篇 |
2000年 | 27篇 |
1999年 | 24篇 |
1998年 | 13篇 |
1997年 | 14篇 |
1996年 | 8篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 9篇 |
1915年 | 6篇 |
1907年 | 7篇 |
排序方式: 共有946条查询结果,搜索用时 15 毫秒
841.
Yan Li Il-Chan Kim Young Ja Kim Moon Kyoo Kim Yong-Dal Yoon Yong-Sung Lee Jae-Seong Lee 《Marine environmental research》2004,58(2-5):681
We have cloned the proto-oncogene c-fos from a self-fertilizing fish Rivulus marmoratus (Cyprinodontiformes, Rivulidae) after screening of R. marmoratus λGEM-11 genomic DNA library, and sequenced over 12 kb including all exons, introns and the promoter region. The R. marmoratus c-fos gene consisted of one noncoding exon and four exons with high similarity to those of fugu and mammals. We sequenced ≈7 kb of the R. marmoratus c-fos gene promoter region to gain a better understanding of the molecular anatomy of the immediate response of this gene upon cellular damage. In the promoter region, R. marmoratus c-fos gene has seven xenobiotic response elements (XREs) and eight metal response elements (MREs) as well as two estradiol (E2), 4 NFκB, 2 CarG, 2 prolactin (PRL) motifs and one pit1 site, while the 3′-UTR of this gene contains the estrogen response element (ERE). The seven XRE and eight MRE motifs raise the possibility of its regulation by exposure to environmental pollutants. In this paper, we discuss the gene structure of R. marmoratus c-fos gene and compare its promoter region with those of other organisms' c-fos genes. We propose its potential use in ecotoxicology. 相似文献
842.
Jo Hyun Kyoung Sa Young Hong Jang Whan Kim Kwang June Bai 《Ocean Engineering》2005,32(17-18):2020-2039
A nonlinear sloshing problem is numerically simulated. During excessive sloshing, the sloshing-induced impact load can cause a critical damage on the tank structure. Recently the problem becomes an important research topic in LNG (Liquefied Natural Gas) Tanker and FPSO (Floating Production Storage Offloading) design. In this study, the wave impact load on the structure is obtained numerically by imposing the exact nonlinear free surface conditions and compared with that predicted by Morison's formula. As a theoretical model, a three-dimensional free surface flow in a tank is formulated in the scope of potential flow theory with the exact nonlinear free-surface conditions. A finite-element method based on Hamilton's principle is employed as a numerical method. The problem is treated as an initial-value problem. The nonlinear problem is numerically solved through an iterative scheme at each time step. 相似文献
843.
Jeong?Hwan?LeeEmail author Young?Soon?Baek Byong?Jae?Ryu Michael?Riedel Roy?D.?Hyndman 《Marine Geophysical Researches》2005,26(1):51-59
Recently, several countries have conducted projects to explore and develop natural gas hydrate, which is one of the new alternative
energy resources for the future. In Korea, a five-year national research project was initiated in 2000. As part of this project,
a seismic survey was performed in the East Sea of Korea to quantify the potential magnitude and distribution of natural gas
hydrates. Multi-channel seismic data and core samples have been acquired and recovered in the survey area. Analysis of seismic
data show clear bottom simulating reflectors (BSRs), seismic blank zones (or wipe-out zones) with velocity pull-up structure,
and pock-marks. In this study, we present the results of seismic surveys which indicate the existence of natural gas hydrates
in Korean offshore areas. These results will be applied to select areas for coring (or drilling) and detailed exploration
such as 2D seismic survey with long offset or 3D seismic in the future. 相似文献
844.
Year-to-year variation of bottom cold waters around the Korea Strait was investigated based on bottom temperatures measured
by submarine telephone cable between Pusan, Korea and Hamada, Japan from 1982 to 1992. The characteristics of bottom temperatures
could be divided into three different groups: the Korean side, the middle, and the Japanese side. Temperature drops in summer
appeared in all the three regions implying the intrusion of cold waters into the Korea Strait. Significant decreases in the
Korean side were observed in 1983, 1986, 1990, 1991, and 1992 when bottom temperatures were high in the middle. In contrast,
bottom temperatures significantly decreased in the middle in 1985, 1988, and 1989 when the temperature drops in the Korean
side were relatively small. This tendency for a negative relationship was also shown in the second mode of an EOF analysis.
In the years when bottom temperatures significantly decreased in the Korean side, the cold water along the east coast of Korea
expanded offshore and its temperature was low. On the contrary, cold water in the southern region of the Ulleung Basin developed
in the years when bottom temperatures decreased considerably in the middle. 相似文献
845.
Dae Choul Kim Gwang Hoon Lee Young Kyo Seo Gil Young Kim Seok Yun Kim Jeong Chang Kim Soo Chul Park Roy Wilkens 《Marine Georesources & Geotechnology》2004,22(1):21-31
Shallow gas in the Korea Strait shelf mud (KSSM) off SE Korea, revealed by high-resolution subbottom profiles, is associated with acoustic blanking, acoustic turbidity, seepages with plumes in the water column, and seafloor depressions. The acoustic blanking, characterized by strong, consistent top reflection and wipeout below, is most dominant. The seaward edge of the acoustic blanking zone generally coincides with the 100-m water-depth contour, suggesting that the water depth (the pressure) may control the distribution of shallow gas. The acoustic turbidity, characterized by diffuse top reflection, is a dark smear, partially blanking the data below. The seepages with plumes, characterized by vertical smearing and disturbed seafloor, are seen only along the shallowest, landward edge of the acoustic blanking zone. This may suggest that the decreased gas solubility at shallow water depths, caused by the lowered pressure, increases the volume of free gas in the sediments, facilitating the gas escape. The seafloor depressions, interpreted as pockmarks, are accompanied by cone-shaped acoustic masking, which is probably the reflection from a narrow vent of gas. The gas-related acoustic anomalies appear to occur mostly in the upper, recent mud of the KSSM. Neither permeable beds nor faults, which can act as vertical migration pathways for deep thermogenic gas, are evident in the recent mud. We interpret that the bacterial degradation of organic matter in situ is the main source for the gas in the KSSM. The upwelling off SE Korea may be an important source for the increased organic matter in the area. 相似文献
846.
847.
Gil Young Kim Buyanbat Narantsetseg Dong Geun Yoo 《Marine Georesources & Geotechnology》2021,39(1):34-43
AbstractGeophysical evidence indicating the presence of gas hydrate has been found in the Ulleung Basin, which lies off the east coast of the Korean Peninsula; however, hydrate distribution in the basin is not well understood. Logging-while-drilling data for 13 sites in the Ulleung Basin, East Sea, were obtained to investigate the distribution pattern of gas hydrate. Most of the sites yielded log data indicating the presence of gas hydrate. Prominent fractures (both resistive and conductive fractures) were clearly identified on the resistivity borehole images, particularly at seismic chimney sites. Resistive fractures, which contain large amounts of gas hydrate, are prominent in the seismic chimney sites. The strike and dip of each fracture was calculated and displayed on a stereographic plot and rosette diagram. From the fracture orientations on the stereographic plots, the maximum horizontal stress is NW–SE, reflecting the regional stress regime around the Ulleung Basin, although the fracture orientations are broadly distributed, indicating that the fracture pattern is not well-ordered on the rosette diagram. The fracture dips are between 36.46° and 63.66°; the range of dip azimuths is 0.94°–359°, and exhibit little change with depth. The dip azimuths are generally westerly to southwesterly. 相似文献
848.
A.T. Young 《Icarus》1973,18(4):564-582
Water solutions of sulfuric acid, containing about 75% H2SO4 by weight, have a refractive index within 0.01 of the values deduced from polarimetric observations of the Venus clouds. These solutions remain liquid at the cloud temperature, thus explaining the spherical shape of the cloud particles (droplets). The equilibrium vapor pressure of water above such solutions is 0.01 that of liquid water or ice, which accounts for the observed dryness of the cloud region. Furthermore, H2SO4 solutions of such concentration have spectra very similar to Venus in the 8–13 μm region; in particular, they explain the 11.2 μm band. Cold sulfuric acid solutions also seem consistent with Venus spectra in the 3–4 μm region. The amount of acid required to make the visible clouds is quite small, and is consistent with both the cosmic abundance of sulfur and the degree of out-gassing of the planet indicated by known atmospheric constituents. Sulfuric acid occurs naturally in volcanic gases, along with known constituents of the Venus atmosphere such as CO2, HCl, and HF ; it is produced at high temperature by reactions between these gases and common sulfate rocks. The great stability and low vapor pressure of H2SO4 and its water solutions explain the lack of other sulfur compounds in the atmosphere of Venus—a lack that is otherwise puzzling.Sulfuric acid precipitation may explain some peculiarities in Venera and Mariner data. Because sulfuric acid solutions are in good agreement with the Venus data, and because no other material that has been proposed is even consistent with the polarimetric and spectroscopic data, H2SO4 must be considered the most probable constituent of the Venus clouds. 相似文献
849.
Andrew T. Young 《Icarus》1977,32(1):1-26
A simple radiative-transfer theory that allows for the change in the absorptions of sulfur and carbon dioxide with depth in the atmosphere of Venus can account simultaneously for (1) the spectral reflectance of Venus; (2) the wavelength dependence of contrast in uv cloud features; (3) the CO2 line profile; (4) the change in slope of the curve of growth from the 7820- to the 10488-Å CO2 bands; and (5) the rotational temperature near 246°K found for all CO2 bands. The model cloud consists of 1-μm sulfuric-acid particles, which are well mixed between about 64 km and the 49-km cloud base found by Veneras 9 and 10, plus an overlapping cloud of much larger sulfur particles that extends down to the 35-km cloud base found by Venera 8. The mixing ratios (by number of molecules) below about 64 km are: H2O, 2 × 10?4; H2SO4, 10?5; and sulfur, 10?4. Although the cloud contains an order of magnitude more sulfur than sulfuric acid, the sulfur particles are an order of magnitude larger, and so have only about 1% of the number density of the acid droplets. The “black-white” radiative-transfer model assumes perfectly conservative scattering above the level (which depends on wavelength) where an absorber becomes “black” due to the local temperature and pressure. So-called homogeneous scattering models are inherently self-contradictory, and are inapplicable to planetary atmospheres; the vertical inhomogeneity is an essential feature that must be modeled correctly. The pressure of CO2 line formation is about half the pressure in the region where uv markings occur. 相似文献
850.
Nine plates of the 7820 Å CO2 band were taken in 1971. A curve-of-growth analysis of the CO2 lines indicates a rotational temperature of 241 ± 2°K, with an average slope to the curve of growth of 0.60 ± 0.03. The Venus phase angle ranged from 7.2 to 10.7°. The equivalent widths of the 1971 data fall on a smooth curve fit through the 1969 data for this band; there does not appear to be any discontinuity in the phase curve at small phase angles. 相似文献