全文获取类型
收费全文 | 2618篇 |
免费 | 106篇 |
国内免费 | 11篇 |
专业分类
测绘学 | 78篇 |
大气科学 | 279篇 |
地球物理 | 799篇 |
地质学 | 962篇 |
海洋学 | 79篇 |
天文学 | 400篇 |
综合类 | 4篇 |
自然地理 | 134篇 |
出版年
2021年 | 42篇 |
2020年 | 36篇 |
2019年 | 26篇 |
2018年 | 105篇 |
2017年 | 85篇 |
2016年 | 129篇 |
2015年 | 97篇 |
2014年 | 111篇 |
2013年 | 185篇 |
2012年 | 78篇 |
2011年 | 102篇 |
2010年 | 113篇 |
2009年 | 109篇 |
2008年 | 76篇 |
2007年 | 81篇 |
2006年 | 77篇 |
2005年 | 63篇 |
2004年 | 37篇 |
2003年 | 48篇 |
2002年 | 51篇 |
2001年 | 46篇 |
2000年 | 47篇 |
1999年 | 28篇 |
1998年 | 25篇 |
1997年 | 36篇 |
1996年 | 29篇 |
1995年 | 36篇 |
1994年 | 39篇 |
1993年 | 32篇 |
1992年 | 25篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1986年 | 28篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 36篇 |
1982年 | 25篇 |
1981年 | 22篇 |
1980年 | 22篇 |
1979年 | 31篇 |
1978年 | 27篇 |
1977年 | 31篇 |
1976年 | 25篇 |
1975年 | 21篇 |
1974年 | 28篇 |
1973年 | 30篇 |
1971年 | 22篇 |
1968年 | 23篇 |
排序方式: 共有2735条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
D. M. Cocârţă S. Neamţu A. M. Reşetar Deac 《International Journal of Environmental Science and Technology》2016,13(8):2025-2036
Human activities have progressively increased in recent years. Consequently, significant environment deterioration resulted. Soils have a particularly varied vulnerability to heavy metal pollution, especially in the vicinity of industrial areas. Heavy metal contamination of soil may induce risks and hazards to humans and the ecosystem, while toxic metals in soil can severely inhibit the biodegradation of organic contaminants. This paper is focused on human health risk assessment from extremely contaminated soil with heavy metals, mainly with carcinogenic elements. The study refers to an agricultural area in the vicinity of an old metallurgical processing industrial facility. The contaminants evaluated in the present paper are beryllium (Be), cadmium (Cd), chromium (Cr), nickel (Ni) and lead (Pb). Contamination level is pointed out through laboratory analysis results of soil samples taken from 0–0.2 m, 0.2–0.4 m soil layers and up to 2.1 m soil depth. Some heavy metal concentrations (Cd, Cr and Pb) exceed the intervention thresholds for sensitive areas, as they are stipulated in the national regulation in Romania. The identified average concentration levels of Cd, CrVI and Pb in the first layer of the investigated land are 23.83, 7.71 and 704.22 mg/kgd.w, respectively. The results show that the potential risk of human health is relevant (higher than the acceptable one after World Health Organization) and a possible solution for the remediation should become a major concern for the investigated area. 相似文献
95.
96.
97.
Höhn Stefan Koglin Nikola Klopf Lisa Schüssler Ulrich Tragelehn Harald Frimmel Hartwig E. Zeh Armin Brätz Helene 《International Journal of Earth Sciences》2018,107(1):359-377
International Journal of Earth Sciences - Stratigraphically well-defined volcanic rocks in Palaeozoic volcano-sedimentary units of the Frankenwald area (Saxothuringian Zone, Variscan Orogen) were... 相似文献
98.
Estuaries act as an organic matter and nutrient filter in the transition between the land, rivers and the ocean. In the past, high nutrient and organic carbon load and low oxygen concentration made the Elbe River estuary (NW Europe) a sink for dissolved inorganic nitrogen. A recent reduction in loads and subsequent recovery of the estuary changed its biogeochemical function, so that nitrate is no longer removed on its transition towards the coastal North Sea. Nowadays in the estuary, nitrification appears to be a significant nitrate source. To quantify nitrification and determine actively nitrifying regions in the estuary, we measured the concentrations of ammonium, nitrite and nitrate, the dual stable isotopes of nitrate and net nitrification rates in the estuary on five cruises from August 2012 to August 2013. The nitrate concentration increased markedly downstream of the port of Hamburg in summer and spring, accompanied by a decrease of nitrate isotope values that was clearest in summer exactly at the location where nitrate concentration started to increase. Ammonium and nitrite peaked in the Hamburg port region (up to 18 and 8 μmol L?1, respectively), and nitrification rates in this region were up to 7 μmol L?1 day?1. Our data show that coupled re-mineralization and nitrification are significant internal nitrate sources that almost double the estuary’s summer nitrate concentration. Furthermore, we find that the port of Hamburg is a hot spot of nitrification, whereas the maximum turbidity zone (MTZ) only plays a subordinate role in turnover of nitrate. 相似文献
99.
Patrizia Köpfli Lorenz M. Grämiger Jeffrey R. Moore Christof Vockenhuber Susan Ivy-Ochs 《Swiss Journal of Geoscience》2018,111(1-2):205-219
Landslide deposits dam Lake Oeschinen (Oeschinensee), located above Kandersteg, Switzerland. However, past confusion differentiating deposits of multiple landslide events has confounded efforts to quantify the volume, age, and failure dynamics of the Oeschinensee rock avalanche. Here we combine field and remote mapping, topographic reconstruction, cosmogenic surface exposure dating, and numerical runout modeling to quantify salient parameters of the event. Differences in boulder lithology and deposit morphology reveal that the landslide body damming Oeschinensee consists of debris from both an older rock avalanche, possibly Kandertal, as well as the Oeschinensee rock avalanche. We distinguish a source volume for the Oeschinensee event of 37 Mm3, resulting in an estimated deposit volume of 46 Mm3, smaller than previous estimates that included portions of the Kandertal mass. Runout modeling revealed peak and average rock avalanche velocities of 65 and 45 m/s, respectively, and support a single-event failure scenario. 36Cl surface exposure dating of deposited boulders indicates a mean age for the rock avalanche of 2.3 ± 0.2 kyr. This age coincides with the timing of a paleo-seismic event identified from lacustrine sediments in Swiss lakes, suggesting an earthquake trigger. Our results help clarify the hazard and geomorphic effects of rare, large rock avalanches in alpine settings. 相似文献
100.
Natural Hazards - The deltaic coast of Myanmar was severely hit by tropical cyclone Nargis in May 2008. In the present study, a top-down numerical simulation approach using the Weather Research and... 相似文献