全文获取类型
收费全文 | 57989篇 |
免费 | 1168篇 |
国内免费 | 523篇 |
专业分类
测绘学 | 1592篇 |
大气科学 | 4356篇 |
地球物理 | 11129篇 |
地质学 | 21112篇 |
海洋学 | 5207篇 |
天文学 | 13305篇 |
综合类 | 210篇 |
自然地理 | 2769篇 |
出版年
2022年 | 393篇 |
2021年 | 720篇 |
2020年 | 770篇 |
2019年 | 801篇 |
2018年 | 1842篇 |
2017年 | 1778篇 |
2016年 | 2191篇 |
2015年 | 1204篇 |
2014年 | 2024篇 |
2013年 | 3286篇 |
2012年 | 2155篇 |
2011年 | 2650篇 |
2010年 | 2339篇 |
2009年 | 2956篇 |
2008年 | 2465篇 |
2007年 | 2500篇 |
2006年 | 2326篇 |
2005年 | 1731篇 |
2004年 | 1749篇 |
2003年 | 1646篇 |
2002年 | 1577篇 |
2001年 | 1376篇 |
2000年 | 1243篇 |
1999年 | 985篇 |
1998年 | 1039篇 |
1997年 | 963篇 |
1996年 | 786篇 |
1995年 | 839篇 |
1994年 | 728篇 |
1993年 | 636篇 |
1992年 | 606篇 |
1991年 | 614篇 |
1990年 | 662篇 |
1989年 | 502篇 |
1988年 | 510篇 |
1987年 | 554篇 |
1986年 | 500篇 |
1985年 | 634篇 |
1984年 | 703篇 |
1983年 | 613篇 |
1982年 | 583篇 |
1981年 | 531篇 |
1980年 | 485篇 |
1979年 | 491篇 |
1978年 | 476篇 |
1977年 | 389篇 |
1976年 | 353篇 |
1975年 | 371篇 |
1974年 | 316篇 |
1973年 | 363篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Water Resources - Based on 1965–2020 series we have shown relationships between the features of the water runoff of the spring flood in mouths of large rivers of North-Eastern Europe and the... 相似文献
2.
Marine ferromanganese nodules and crusts containing Mn, Cu, Ni and Co in the most promising resource-grade concentrations and quantities, together with Fe and Zn (all elements of biogeochemical importance) are found far from land on the deep seafloor of the Pacific Ocean. The biogeochemical, chemical and physical mechanisms contributing to their formation, distribution, abundance and – for these six elements – variability in their concentrations in these deposits, are the main focus of the present review. The mechanisms addressed include biological productivity, sedimentation types and rates, bottom water characteristics, the Calcium Carbonate Compensation Depth, the depth and intensity of the oxygen minimum zone, and biogeochemical characteristics of the six focal elements. Particular attention is given to comparisons between the deposits found in the north and the south Pacific, in order to present an overarching view of our current understanding of the mechanisms that apply to both nodules and crusts in both oceanic hemispheres, including examination of the possible existence of a marine ferromanganese oxide continuum. The renewed interest in the commercial exploitation of these deposits has stimulated a welcome increase in scientific research that is essential to informing the public discourse on seabed mining. We briefly reflect on the work addressed in this review in that context. 相似文献
3.
Roy R. Kuttippurath J. Lefèvre F. Raj S. Kumar P. 《Theoretical and Applied Climatology》2022,149(1-2):119-130
Theoretical and Applied Climatology - Sudden stratospheric warmings (SSWs) are associated with rapid rise in temperature in a short period of time in the polar vortex and reversal of the zonal... 相似文献
4.
Khegai V. V. Legenka A. D. Abunin A. A. Abunina M. A. Belov A. V. Gaidash S. P. 《Geomagnetism and Aeronomy》2022,61(1):S36-S47
Geomagnetism and Aeronomy - A comparative analysis of the correlation between the number of strong (magnitude M ≥ 5.0), crustal (hypocenter depth 0 ≤ h ≤ 60 km) earthquakes per... 相似文献
5.
J.J. Butler Jr S. Knobbe E.C. Reboulet D.O. Whittemore B.B. Wilson G.C. Bohling 《Ground water》2021,59(6):808-818
Many of the world's major aquifers are under severe stress as a result of intensive pumping to support irrigated agriculture and provide drinking water supplies for millions. The question of what the future holds for these aquifers is one of global importance. Without better information about subsurface conditions, it will be difficult to reliably assess an aquifer's response to management actions and climatic stresses. One important but underutilized source of information is the data from monitoring well networks that provide near-continuous records of water levels through time. Most organizations running these networks are, by necessity, primarily focused on network maintenance. The result is that relatively little attention is given to interpretation of the acquired hydrographs. However, embedded in those hydrographs is valuable information about subsurface conditions and aquifer responses to natural and anthropogenic stresses. We demonstrate the range of insights that can be gleaned from such hydrographs using data from the High Plains aquifer index well network of the Kansas Geological Survey. We show how information about an aquifer's hydraulic state and lateral extent, the nature of recharge, the hydraulic connection to the aquifer and nearby pumping wells, and the expected response to conservation-based pumping reductions can be extracted from these hydrographs. The value of this information is dependent on accurate water-level measurements; errors in those measurements can make it difficult to fully exploit the insights that water-well hydrographs can provide. We therefore conclude by presenting measures that can help reduce the potential for such errors. 相似文献
6.
Onishchenko O. G. Pokhotelov O. A. Belyaev V. S. Zagreev B. V. Matafonov A. P. 《Geomagnetism and Aeronomy》2021,61(1):25-28
Geomagnetism and Aeronomy - A new analytical model for the generation of axially symmetric jets (directed jets) in a nondissipative, nonequilibrium stratified plasma has been created in the... 相似文献
7.
Shakirov R. B. Cuong Do Huy Obzhirov A. I. Valitov M. G. Lee N. S. Legkodimov A. A. Kalgin V. Yu. Yeskova A. I. Proshkina Z. N. Telegin Yu. A. Storozhenko A. V. Ivanov M. V. Pletnev S. P. Sedin V. T. Bulanov A.V. Shvalov D. A. Lipinskaya N. A. Bovsun M. A. Makseev D. S. Thanh Nguyen Trung Anh Le Duc Luong Le Duc 《Oceanology》2021,61(1):147-149
Oceanology - Abstract—The paper gives brief results of comprehensive studies in the South China Sea obtained from a joint Russian–Vietnamese expedition in November 2019 (cruise 88 of... 相似文献
8.
Astronomy Letters - The emission from the Crab nebula exhibits a significant gamma-ray variability. In this paper we have analyzed this variability in terms of periodicity. Using the pulsar... 相似文献
9.
Cristián Frêne Juan J. Armesto Freddy Véliz Fernando D. Alfaro Kathleen C. Weathers 《水文研究》2021,35(5):e14175
The variability of rainfall-dependent streamflow at catchment scale modulates many ecosystem processes in wet temperate forests. Runoff in small mountain catchments is characterized by a quick response to rainfall pulses which affects biogeochemical fluxes to all downstream systems. In wet-temperate climates, water erosion is the most important natural factor driving downstream soil and nutrient losses from upland ecosystems. Most hydrochemical studies have focused on water flux measurements at hourly scales, along with weekly or monthly samples for water chemistry. Here, we assessed how water and element flows from broad-leaved, evergreen forested catchments in southwestern South America, are influenced by different successional stages, quantifying runoff, sediment transport and nutrient fluxes during hourly rainfall events of different intensities. Hydrograph comparisons among different successional stages indicated that forested catchments differed in their responses to high intensity rainfall, with greater runoff in areas covered by secondary forests (SF), compared to old-growth forest cover (OG) and dense scrub vegetation (CH). Further, throughfall water was greatly nutrient enriched for all forest types. Suspended sediment loads varied between successional stages. SF catchments exported 455 kg of sediments per ha, followed by OG with 91 kg/ha and CH with 14 kg/ha, corresponding to 11 rainfall events measured from December 2013 to April 2014. Total nitrogen (TN) and phosphorus (TP) concentrations in stream water also varied with rainfall intensity. In seven rainfall events sampled during the study period, CH catchments exported less nutrients (46 kg/ha TN and 7 kg/ha TP) than SF catchments (718 kg/ha TN and 107 kg/ha TP), while OG catchments exported intermediate sediment loads (201 kg/ha TN and 23 kg/ha TP). Further, we found significant effects of successional stage attributes (vegetation structure and soil physical properties) and catchment morphometry on runoff and sediment concentrations, and greater nutrients retention in OG and CH catchments. We conclude that in these southern hemisphere, broad-leaved evergreen temperate forests, hydrological processes are driven by multiple interacting phenomena, including climate, vegetation, soils, topography, and disturbance history. 相似文献
10.
Koronkevich N. I. Barabanova E. A. Georgiadi A. G. Dolgov S. V. Zaitseva I. S. 《Water Resources》2021,48(4):502-511
Water Resources - Different types of transboundary water exchange in Russia are considered, including through state, administrative, and natural boundaries. The presented characteristics refer to... 相似文献