全文获取类型
收费全文 | 73922篇 |
免费 | 1526篇 |
国内免费 | 619篇 |
专业分类
测绘学 | 1806篇 |
大气科学 | 5577篇 |
地球物理 | 15094篇 |
地质学 | 24983篇 |
海洋学 | 6901篇 |
天文学 | 16353篇 |
综合类 | 192篇 |
自然地理 | 5161篇 |
出版年
2022年 | 947篇 |
2021年 | 1425篇 |
2020年 | 1486篇 |
2019年 | 1580篇 |
2018年 | 1366篇 |
2017年 | 1177篇 |
2016年 | 1443篇 |
2015年 | 1101篇 |
2014年 | 1454篇 |
2013年 | 3342篇 |
2012年 | 1566篇 |
2011年 | 2476篇 |
2010年 | 2129篇 |
2009年 | 3156篇 |
2008年 | 2764篇 |
2007年 | 2511篇 |
2006年 | 2570篇 |
2005年 | 2220篇 |
2004年 | 2471篇 |
2003年 | 2363篇 |
2002年 | 2268篇 |
2001年 | 2014篇 |
2000年 | 1797篇 |
1999年 | 1548篇 |
1998年 | 1588篇 |
1997年 | 1570篇 |
1996年 | 1195篇 |
1995年 | 1234篇 |
1994年 | 1127篇 |
1993年 | 1010篇 |
1992年 | 979篇 |
1991年 | 848篇 |
1990年 | 1031篇 |
1989年 | 885篇 |
1988年 | 796篇 |
1987年 | 943篇 |
1986年 | 883篇 |
1985年 | 1038篇 |
1984年 | 1217篇 |
1983年 | 1169篇 |
1982年 | 1020篇 |
1981年 | 1004篇 |
1980年 | 849篇 |
1979年 | 824篇 |
1978年 | 879篇 |
1977年 | 802篇 |
1976年 | 747篇 |
1975年 | 703篇 |
1974年 | 757篇 |
1973年 | 747篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Water Resources - The article presents the results of summer dry-season areal surveys of subsoil water chemistry in the drainage basin of the Ivankovo Reservoir in the Volga segment from Tver City... 相似文献
82.
Colin P. R. McCarter Stephen D. Sebestyen Susan L. Eggert Randall K. Kolka Carl P. J. Mitchell 《水文研究》2020,34(26):5354-5369
Sustainable fuels legislation and volatility in energy prices have put additional pressures on the forestry sector to intensify the harvesting of biomass for “advanced biofuel” production. To better understand how residual biomass removal after harvest affects forest hydrology in relatively low slope terrain, a Before-After-Control-Impact (BACI) study was conducted in the USDA Forest Service's Marcell Experimental Forest, Minnesota, USA. Hydrological measurements were made from 2010–2013 on a forested hillslope that was divided into three treatment blocks, where one block was harvested and residual biomass removed (Biomass Removed), the second was harvested and residual biomass left (Biomass Left), and the last block was left as an Unharvested Control. The pre-harvest period (2 years) was 2010–11 and post-harvest (2 years) was 2012–13. Water table elevation at the upslope and downslope position, subsurface runoff, and soil moisture were measured between May–November. Mixed effect statistical models were used to compare both the before-after and “control” treatment ratios (ratios between harvested hillslopes and the Unharvested Control hillslope). Subsurface runoff significantly increased (p < .05) at both harvested hillslopes but to a greater degree on the Biomass Left hillslope. Greater subsurface runoff volumes at both harvested hillslopes were driven by substantial increases during fall, with additional significant increases during summer on the Biomass Left hillslope. The hydrological connectivity, inferred from event runoff ratios, increased due to harvesting at both hillslopes but only significantly on the Biomass Left hillslope. The winter harvest minimized soil disturbance, resulting in no change to the effective hydraulic conductivity distribution with depth. Thus, the observed hydrological changes were driven by increased effective precipitation and decreased evapotranspiration, increasing the duration that both harvested hillslopes were hydrologically active. The harvesting of residual biomass appears to lessen hydrological connectivity relative to leaving residual biomass on the hillslope, potentially decreasing downstream hydrological impacts of similar forestry operations. 相似文献
83.
Slyuta E. N. Vysochkin V. V. Ivanov V. V. Makovchuk V. Yu. Nazarov A. I. Pogonin V. I. Roskina E. A. Safronov V. V. Tatsiy L. P. 《Solar System Research》2021,55(5):437-445
Solar System Research - The ionization-type cosmic dust detector METEOR-L is being developed for the lunar orbiter Luna-26 and is designed to study the distribution of meteoric bodies in space by... 相似文献
84.
Astronomy Letters - The sensitivity of future far-infrared telescopes, such as Millimetron, will be limited by the confusion noise produced by distant galaxies. We have constructed a model of the... 相似文献
85.
Bondur V. G. Vorobyev V. E. Murynin A. B. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(9):887-897
Izvestiya, Atmospheric and Oceanic Physics - A method for retrieving sea wave spectra from space images of high spatial resolution has been developed for various conditions of wave generation based... 相似文献
86.
Garetsky R. G. Gribik Ya. G. Litvinovskaya R. P. Savchuk A. L. Mardosevich M. A. Khripach V. A. 《Doklady Earth Sciences》2020,494(1):688-690
Doklady Earth Sciences - The content of plant hormones (brassinosteroids) in oil samples from a number of oilfields in Belarus is determined using an enzyme immunoassay method. Brassinosteroids of... 相似文献
87.
Nemirovskaya I. A. Zavyalov P. O. Konovalov B. V. Khramtsova A. V. 《Doklady Earth Sciences》2020,492(1):387-391
Doklady Earth Sciences - The results of studying the content and composition of aliphatic hydrocarbons (AHCs) and polycyclic aromatic hydrocarbons (PAHs) in the suspended particulate matter of the... 相似文献
88.
Doklady Earth Sciences - Based on investigation of Proterozoic mafic dike swarms of the Siberian Craton, we inferred how the geochemical and isotopic characteristics of dike swarms of dolerites of... 相似文献
89.
Fayman P. A. Prants S. V. Budyansky M. V. Uleysky M. Yu. 《Izvestiya Atmospheric and Oceanic Physics》2020,56(6):618-631
Izvestiya, Atmospheric and Oceanic Physics - Using the eddy-permitting model, circulation in the Okhotsk Sea and in an adjacent area of the Pacific Ocean is retrospectively simulated from 1991 to... 相似文献
90.
Doklady Earth Sciences - For the first time, a detailed density 3D model of the lithosphere of the Sikhote-Alin orogenic belt to a depth of 130 km has been created. Two extended submeridional... 相似文献