全文获取类型
收费全文 | 754篇 |
免费 | 29篇 |
国内免费 | 28篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 80篇 |
地球物理 | 185篇 |
地质学 | 208篇 |
海洋学 | 219篇 |
天文学 | 61篇 |
综合类 | 22篇 |
自然地理 | 28篇 |
出版年
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2018年 | 17篇 |
2017年 | 33篇 |
2016年 | 51篇 |
2015年 | 34篇 |
2014年 | 46篇 |
2013年 | 57篇 |
2012年 | 47篇 |
2011年 | 47篇 |
2010年 | 68篇 |
2009年 | 54篇 |
2008年 | 45篇 |
2007年 | 38篇 |
2006年 | 21篇 |
2005年 | 21篇 |
2004年 | 22篇 |
2003年 | 29篇 |
2002年 | 16篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1962年 | 2篇 |
1960年 | 1篇 |
1954年 | 3篇 |
1949年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有811条查询结果,搜索用时 15 毫秒
801.
Kalashnikov I. Yu. Dodin A. V. Il’ichev I. V. Krauz V. I. Chechetkin V. M. 《Astronomy Reports》2021,65(6):477-487
Astronomy Reports - The use of Z-pinch facilities makes it possible to carry out well-controlled and diagnosable laboratory experiments to study laboratory jets with scaling parameters close to... 相似文献
802.
Gontcharov G. A. Mosenkov A. V. Savchenko S. S. Il’in V. B. Marchuk A. A. Smirnov A. A. Usachev P. A. Polyakov D. M. Hebdon N. 《Astronomy Letters》2022,48(10):578-600
Astronomy Letters - We present a new version of our analytical model of the spatial interstellar extinction variations within the nearest kiloparsec from the Sun. This model treats the... 相似文献
803.
The effects of future temperature and hence evapotranspiration increases on drought risk over North America, based on ten current (1970–1999) and ten corresponding future (2040–2069) Regional Climate Model (RCM) simulations from the North American Regional Climate Change Assessment Program, are presented in this study. The ten pairs of simulations considered in this study are based on six RCMs and four driving Atmosphere Ocean Coupled Global Climate Models. The effects of temperature and evapotranspiration on drought risks are assessed by comparing characteristics of drought events identified on the basis of Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspration Index (SPEI). The former index uses only precipitation, while the latter uses the difference (DIF) between precipitation and potential evapotranspiration (PET) as input variables. As short- and long-term droughts impact various sectors differently, multi-scale (ranging from 1- to 12-month) drought events are considered. The projected increase in mean temperature by more than 2 °C in the future period compared to the current period for most parts of North America results in large increases in PET and decreases in DIF for the future period, especially for low latitude regions of North America. These changes result in large increases in future drought risks for most parts of the USA and southern Canada. Though similar results are obtained with SPI, the projected increases in the drought characteristics such as severity and duration and the spatial extent of regions susceptible to drought risks in the future are considerably larger in the case of SPEI-based analysis. Both approaches suggest that long-term and extreme drought events are affected more by the future increases in temperature and PET than short-term and moderate drought events, particularly over the high drought risk regions of North America. 相似文献
804.
Dongseon Kim Eun-Jin Yang Seung Ho Baek Kyung-Hee Kim Jin-Hyun Jeong Young-Ok Kim 《Ocean Science Journal》2014,49(3):223-230
Dissolved inorganic carbon (DIC) and alkalinity were precisely measured for surface and bottom waters in Gwangyang Bay, Korea, during the four seasons to assess seasonal variations of aragonite saturation state (Ωarag). Both the surface and bottom waters were undersaturated with respect to aragonite during summer but were supersaturated during the other seasons. The summertime undersaturation of the surface waters with respect to aragonite may have been a result of the dilution effect caused by higher seasonal river runoff. In the bottom waters, the average DIC concentration increased by 40.6 μmol kg?1 from spring to summer, while the average alkalinity decreased by 74.7 μeq kg?1. As a result, the alkalinity/DIC ratio decreased from 1.07 in spring to 1.01 in summer and pH also decreased from 7.91 to 7.48, which resulted in the summertime undersaturation of the bottom waters. 相似文献
805.
806.
G. G. Matishov G. V. Il’in N. E. Kasatkina I. S. Usyagina E. V. Pavel’skaya 《Doklady Earth Sciences》2012,446(2):1185-1189
In March–April 2011, isotopes typical for the Fukushima-1 nuclear power plant (NPP) were found in high-latitude areas of Europe (Svalbard and Kola Peninsula). The background characteristics of the spectrum and activity of radionuclides in the components of the marine environment and the Barents Sea biota were studied for the rest of 2011. It has been shown that these characteristics are within the limits of the stable background formed by the global circulation of radionuclides. Radionuclides that can reliably indicate a trace from the Fukushima-1 NPP have not been found. It is concluded that the probable humid and dry precipitation of isotopes into the land water-catchment area and the marine basin had no effect on the radioecological situation in the coastal zones and in the open-sea parts of the western Arctic. 相似文献
807.
808.
Stable backfill materials for the heat sensitive structures of buried power cables, hot water pipes, and gas pipelines are suggested to have low permeability and high heat transfer characteristics. The hydraulic and thermal conductivities of backfill materials or clay liners are important parameters in proper design and construction of geotechnical structures involved with heat transfers. In this study, to investigate the optimal natural backfill or liner materials, thermal and hydraulic conductivities of kaolin–silica mixtures examined based on the results from laboratory tests under different consolidation conditions. From the experiment results, the thermal conductivity increases while hydraulic conductivity decreases with increasing density during consolidation process. As a result, back-fill materials with high kaolin content under low consolidation stress were desirable materials for burial of heat sensitive structures. 相似文献
809.
Unconfined and triaxial compression tests were carried out to examine the behavior of light-weighted soils (LWS) consisting of expanded polystyrene (EPS), dredged soils, and cement with respect to initial water content. The stress-strain behavior of LWS are analyzed with varying initial water content and silt contents of dredged soils, cement ratio, and confined stress. As initial water contents increase, the compressibility index increases and the preconsolidation pressure was vice versa. As initial water contents increase, the slope of stress-strain curve in elastic zone increases and strain rate at failure decreases and the strain rate at failure was not changed by the being of foams. As initial water contents increase, a compressive strength of LWS decreases. The decrement ratio of compressive strength of LWS with foams increases as cement content increases and initial water contents decreases. The compressive strength increases as silt contents increases. 相似文献
810.
Eko Setyobudi Chan-Hyeok Jeon Kwangho Choi Sung Il Lee Chung Il Lee Jeong-Ho Kim 《Ocean Science Journal》2013,48(2):197-205
The occurrence of Genus Anisakis nematode larvae in marine fishes and cephalopods is epidemiologically important because Anisakis simplex larval stage can cause a clinical disease in humans when infected hosts are consumed raw. Common squid (Todarodes pacificus) from Korean waters were investigated for anisakid nematodes infection during 2009~2011. In total, 1,556 larvae were collected from 615 common squids and 732 of them were subsequently identified by PCR-RFLP analysis of ITS rDNA. Depending on the sampling locations, the nematode larvae from common squid showed different prevalence, intensity and species distribution. A high prevalence (P) and mean intensity (MI) of infection were observed in the Yellow Sea (n = 250, P = 86.0%, MI = 5.99 larvae/host) and the southern sea of Korea (n = 126, P = 57.1%, MI = 3.36 larvae/host). Anisakis pegreffii was dominantly found in common squid from the southern sea (127/ 140, 90.7%) and the Yellow Sea (561/565, 98.9%). In contrast, the P and MI of infection were relatively low in the East Sea (n = 239, P = 8.37%, MI = 1.25 larvae/host). A. pegreffii was not found from the East Sea and 52.0% (13/25) of the nematodes were identified as A. simplex. Most of them were found in the body cavity or digestive tract of common squid, which are rarely consumed raw by humans. Considering the differenences in anisakid nematode species distribution and their microhabitat in common squid, it remains unclear whether common squid plays an important role in the epidemiology of human anisakis infection in Korea. Further extensive identification of anisakid nematodes in common squid, with geographical and seasonal information will be necessary. 相似文献