全文获取类型
收费全文 | 104960篇 |
免费 | 1646篇 |
国内免费 | 1552篇 |
专业分类
测绘学 | 3256篇 |
大气科学 | 7670篇 |
地球物理 | 20299篇 |
地质学 | 40837篇 |
海洋学 | 8235篇 |
天文学 | 19993篇 |
综合类 | 2348篇 |
自然地理 | 5520篇 |
出版年
2022年 | 399篇 |
2021年 | 695篇 |
2020年 | 789篇 |
2019年 | 849篇 |
2018年 | 7584篇 |
2017年 | 6847篇 |
2016年 | 5349篇 |
2015年 | 1610篇 |
2014年 | 2302篇 |
2013年 | 3858篇 |
2012年 | 3765篇 |
2011年 | 7036篇 |
2010年 | 5937篇 |
2009年 | 7045篇 |
2008年 | 6044篇 |
2007年 | 6693篇 |
2006年 | 3007篇 |
2005年 | 2917篇 |
2004年 | 2901篇 |
2003年 | 2749篇 |
2002年 | 2304篇 |
2001年 | 1852篇 |
2000年 | 1721篇 |
1999年 | 1298篇 |
1998年 | 1407篇 |
1997年 | 1299篇 |
1996年 | 1007篇 |
1995年 | 1137篇 |
1994年 | 955篇 |
1993年 | 865篇 |
1992年 | 842篇 |
1991年 | 758篇 |
1990年 | 836篇 |
1989年 | 706篇 |
1988年 | 638篇 |
1987年 | 799篇 |
1986年 | 648篇 |
1985年 | 848篇 |
1984年 | 911篇 |
1983年 | 861篇 |
1982年 | 822篇 |
1981年 | 728篇 |
1980年 | 676篇 |
1979年 | 603篇 |
1978年 | 609篇 |
1977年 | 552篇 |
1976年 | 543篇 |
1975年 | 502篇 |
1974年 | 510篇 |
1973年 | 469篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
91.
Interaction between water flow and ridge bedforms has been studied. The results of experimental studies of velocity distribution over ridge bedforms in a hydraulic laboratory flume are given. The distribution of pressure along the contour of a rigid model ridge, determined in an aerodynamic canal, is also given. 相似文献
92.
An experiment in mesocosms installed in a fish-rearing pond was used to adequately simulate the character of self-purification, migration, and the redistribution of cadmium and its chemical forms in major components of a freshwater ecosystem, into which this chemical is imported in concentrations far in excess of its MAC. The major portion of the imported cadmium was found to be removed from the water mass within a few days, mostly, as a component of particulate matter settling onto the bed, including dead plankton remains, as ion-exchange cadmium forms adsorbed by suspension (37%), and as forms associated with ferromanganese oxides (41%). The rate of cadmium removal from the water mass is determined both by the amount of particulate matter settling onto the bed and the efficiency of cadmium sorption by it, depending on the acid–alkaline and redox conditions in the water body. 相似文献
93.
The processes of formation and distribution of the resources of fresh groundwater and surface water in the territory of Crimea Peninsula are considered. Water availability in the natural–historic and administrative regions of the republic is characterized. The proportions between different categories of groundwater resources are shown with their role in water supply to Crimea taken into account. The presentday development of groundwater resources is analyzed and the possible increase in water consumption meeting geoecological requirements is substantiated. 相似文献
94.
M. M. Pevzner M. L. Tolstykh A. D. Babansky 《Journal of Volcanology and Seismology》2018,12(4):242-251
It is shown that Shiveluch, which consists of several volcanic edifices that stand in one area and in part overlie each other, is a long-lived volcanic massif with a complex structure. The available data on the morphology of the edifice, age, rock compositions, primary melts, and types of eruptive activity were used to identify structurally-temporal units (STUs) in the Shiveluch volcanic massif. It was found that the generation of different-age STUs was due to the activity of at least four magma chambers with different parameters. The durations of the individual chambers were determined. The activities of these chambers were initiated and came to an end nearly instantaneously because of major collapse episodes in the edifice of the massif due to high-magnitude earthquakes. 相似文献
95.
At the beginning of the 21st century, a series of great earthquakes were recorded in northeastern Tibet, along the periphery of the Bayan Hara lithospheric block. An earthquake with MS = 8.1 occurred within the East Kunlun fault zone in the Kunlun Mountains, which caused an extended surface rupture with left-lateral strike slip. An earthquake with MS = 8 occurred in Wenchuan (China) on May 12, 2008, giving rise to an extended overthrust along the Lunmanshan fault zone. An earthquake with MS = 7.1 occurred in Yushu (China) on April 14, 2010; its epicenter was on the Grazze–Yushu–Funchuoshan fault; a left-lateral strikeslip offset was observed on the surface. An earthquake with MS = 7 occurred in the vicinity of Lushan on April 20, 2013; its epicenter was within the Lunmanshan fault zone, 103 km southwest of the zone of the catastrophic Wenchuan earthquake. An earthquake with MS = 8.2 occurred in Nepal on April 25, 2015. Based on the CSN seismic catalog, the energy of all earthquakes in eastern Tibet at the end of the 20th and beginning of the 21st centuries was estimated. It was found that Tibet was seismically quiet from 1980 to 2000. The beginning of the 21st century has been marked by seismic activation with earthquake sources migrating southward to surround the Bayan Hara lithospheric block from every quarter. Therefore, this block can be regarded as one of the most seismically active regions of China. 相似文献
96.
97.
98.
Jeffery A. Watson M. Bayani Cardenas Stephen B. Ferencz Peter S.K. Knappett Bethany T. Neilson 《水文研究》2018,32(9):1267-1281
The transition area between rivers and their adjacent riparian aquifers, which may comprise the hyporheic zone, hosts important biochemical reactions, which control water quality. The rates of these reactions and metabolic processes are temperature dependent. Yet the thermal dynamics of riparian aquifers, especially during flooding and dynamic groundwater flow conditions, has seldom been studied. Thus, we investigated heat transport in riparian aquifers during 3 flood events of different magnitudes at 2 sites along the same river. River and riparian aquifer temperature and water‐level data along the Lower Colorado River in Central Texas, USA, were monitored across 2‐dimensional vertical sections perpendicular to the bank. At the downstream site, preflood temperature penetration distance into the bank suggested that advective heat transport from lateral hyporheic exchange of river water into the riparian aquifer was occurring during relatively steady low‐flow river conditions. Although a small (20‐cm stage increase) dam‐controlled flood pulse had no observable influence on groundwater temperature, larger floods (40‐cm and >3‐m stage increases) caused lateral movement of distinct heat plumes away from the river during flood stage, which then retreated back towards the river after flood recession. These plumes result from advective heat transport caused by flood waters being forced into the riparian aquifer. These flood‐induced temperature responses were controlled by the size of the flood, river water temperature during the flood, and local factors at the study sites, such as topography and local ambient water table configuration. For the intermediate and large floods, the thermal disturbance in the riparian aquifer lasted days after flood waters receded. Large floods therefore have impacts on the temperature regime of riparian aquifers lasting long beyond the flood's timescale. These persistent thermal disturbances may have a significant impact on biochemical reaction rates, nutrient cycling, and ecological niches in the river corridor. 相似文献
99.
Mojtaba Pakparvar Hossein Hashemi Meisam Rezaei Wim M. Cornelis Gholamali Nekooeian Sayyed Ahang Kowsar 《水文科学杂志》2018,63(8):1183-1202
To assess recharge through floodwater spreading, three wells, approx. 30 m deep, were dug in a 35-year-old basin in southern Iran. Hydraulic parameters of the layers were measured. One well was equipped with pre-calibrated time domain reflectometry (TDR) sensors. The soil moisture was measured continuously before and after events. Rainfall, ponding depth and the duration of the flooding events were also measured. Recharge was assessed by the soil water balance method, and by calibrated (inverse solution) HYDRUS-1D. The results show that the 15 wetting front was interrupted at a layer with fine soil accumulation over a coarse layer at the depth of approx. 4 m. This seemed to occur due to fingering flow. Estimation of recharge by the soil water balance and modelling approaches showed a downward water flux of 55 and 57% of impounded floodwater, respectively. 相似文献
100.
Gubanova D. P. Chkhetiani O. G. Kuderina T. M. Iordanskii M. A. Obvintsev Y. I. Artamonova M. S. 《Izvestiya Atmospheric and Oceanic Physics》2018,54(8):777-793
Izvestiya, Atmospheric and Oceanic Physics - This paper summarizes the results of long-term (2004–2016) comprehensive experimental studies of microphysical parameters and the mass... 相似文献