全文获取类型
收费全文 | 61013篇 |
免费 | 837篇 |
国内免费 | 415篇 |
专业分类
测绘学 | 1281篇 |
大气科学 | 4000篇 |
地球物理 | 11899篇 |
地质学 | 21894篇 |
海洋学 | 5768篇 |
天文学 | 14002篇 |
综合类 | 130篇 |
自然地理 | 3291篇 |
出版年
2022年 | 395篇 |
2021年 | 743篇 |
2020年 | 760篇 |
2019年 | 837篇 |
2018年 | 1699篇 |
2017年 | 1543篇 |
2016年 | 1823篇 |
2015年 | 930篇 |
2014年 | 1654篇 |
2013年 | 3160篇 |
2012年 | 1902篇 |
2011年 | 2544篇 |
2010年 | 2333篇 |
2009年 | 3004篇 |
2008年 | 2537篇 |
2007年 | 2744篇 |
2006年 | 2472篇 |
2005年 | 1770篇 |
2004年 | 1719篇 |
2003年 | 1677篇 |
2002年 | 1656篇 |
2001年 | 1484篇 |
2000年 | 1335篇 |
1999年 | 1092篇 |
1998年 | 1098篇 |
1997年 | 1114篇 |
1996年 | 894篇 |
1995年 | 883篇 |
1994年 | 819篇 |
1993年 | 726篇 |
1992年 | 713篇 |
1991年 | 659篇 |
1990年 | 679篇 |
1989年 | 683篇 |
1988年 | 624篇 |
1987年 | 726篇 |
1986年 | 649篇 |
1985年 | 793篇 |
1984年 | 836篇 |
1983年 | 771篇 |
1982年 | 691篇 |
1981年 | 732篇 |
1980年 | 620篇 |
1979年 | 622篇 |
1978年 | 587篇 |
1977年 | 564篇 |
1976年 | 502篇 |
1975年 | 504篇 |
1974年 | 494篇 |
1973年 | 536篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Adam C. Landon Maarten H. Jacobs Craig A. Miller Jerry J. Vaske Brent D. Williams 《社会与自然资源》2020,33(5):574-593
AbstractIncreasing wolf populations are a concern for wildlife managers in the Midwestern U.S. Understanding the psychological mechanisms that contribute to public perceptions of risk will enable development of strategies that seek to mitigate these risks, and suggest where outreach efforts may facilitate acceptance of wolves. We examined the psychological factors that influence Illinois residents’ perceived risks from wolves. We hypothesized that individuals’ perceived risks from wolves were a function of their attitudes toward wolves, negative affect toward wolves, and basic beliefs about wildlife. Data were obtained from a survey of the Illinois public (n?=?784). Negative affect and attitudes toward wolves were direct predictors of perceived risks. Basic beliefs predicted attitudes and negative affect toward wolves. Negative affect predicted attitudes. Basic beliefs had direct and indirect effects on perceived risks. 相似文献
2.
S. P. Villacorta K. G. Evans K. Nakatani I. Villanueva 《Australian Journal of Earth Sciences》2020,67(3):425-436
AbstractLarge debris flows in steep-sloped ravines debouching to the Rimac River, in metropolitan Lima (Peruvian capital), have resulted in considerable loss of life and property adversely impacting communities in the region. Temporal, spatial and volumetric features of debris flows are difficult to predict, and it is of utmost importance that achievable management solutions are found to reduce the impact of these catastrophic events. The emotional and economic toll of these debris flows on this increasingly densely populated capital city in South America is devastating where communities must live in such inadequate and dangerous conditions. To address this problem, the application of advanced Japanese technology, Sustainable Actions Basin Orientation (SABO), has been investigated using a geomorphological modelling to develop an implementation plan. Rayos de Sol stream basin in Chosica, was selected as a pilot to develop the proposal, as it is considered high risk due to the presence of ancient debris flows and recent flows in 2012, 2015 and 2017. The recurrence of debris flows in this location has resulted in numerous deaths and catastrophic property losses. This study combines geologic and geomorphic mapping and hydraulic and landform evolution numerical modelling. The implementation of a SABO Master Plan based on the multidisciplinary assessment hazard scenarios, will allow the implementation of feasible mitigation actions. The SABO technology has been applied successfully in Japan and other countries in areas with steep short slopes, similar to the conditions surrounding the Peruvian capital. Results from this study will be presented to the Peruvian Government as part of an action plan to manage debris-flow impact.
- KEY POINTS
High-risk mass slope failure is linked to poor urban planning in urban developing regions of Lima the capital of Peru.
A multidisciplinary study including geotechnical and hydrological analysis, engineering design, and socio-economic research is required to implement a SABO Master Plan, and this basin is pilot study basin.
At the present time, a maintenance programme for existing hydraulic structures should be implemented, and a flood risk management plan developed may propose the relocation of some communities and infrastructure.
3.
Maslov A. V. Nemirovskaya I. A. Shevchenko V. P. 《Lithology and Mineral Resources》2022,57(3):181-198
Lithology and Mineral Resources - The main geochemical characteristics of gray silts of the Volga Reservoir cascade are discussed. Together with sandy varieties, they occupy more than 60% of the... 相似文献
4.
Acta Geotechnica - Numerous applications of hydraulic conductivity of porous media (e.g., soils, clay liners, rocks, concrete, ceramic filters, etc.) in their unsaturated state are well established... 相似文献
5.
Doklady Earth Sciences - The first results of studies of vertical particle fluxes in a hydrothermal sedimentary system of a subpolar area of the Mid-Atlantic Ridge under the influence of... 相似文献
6.
7.
8.
Zircon crystals precipitated from granitoid magmas contain a robust record of the age and chemistry of continental magmatism spanning some 4.375 Ga of Earth history, a record that charts initiation of plate tectonics. However, constraining when exactly plate tectonics began to dominate crustal growth processes is challenging as the geochemical signatures of individual rocks may reflect local subduction processes rather than global plate tectonics. Here we apply counting statistics to a global database of coupled U–Pb and Hf isotope analyses on magmatic zircon grains from continental igneous and sedimentary rocks to quantify changes in the compositions of their source rocks. The analysis reveals a globally significant change in the sources of granitoid magmas between 3.2 and 2.7 Ga. These secular changes in zircon chemistry are driven by a coupling of the deep (depleted mantle) and shallow (crustal) Earth reservoirs, consistent with a geodynamic regime dominated by Wilson cycle style plate tectonics. 相似文献
9.
V. V. Avdonin N. I. Eremin E. A. Zhegallo N. E. Segreeva 《Doklady Earth Sciences》2018,481(1):839-841
As exemplified by cobalt–bearing Fe–Mn crusts (ferromanganese stromatolite) of the Magellan Seamounts (Clarion–Clipperton Province), the main stages of the structural evolution of bacterial communities have been recognized. It has been demonstrated that the change of the stages is caused by the effect of major tectonic, volcanic, and other geological events. 相似文献
10.