全文获取类型
收费全文 | 299篇 |
免费 | 28篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 32篇 |
地球物理 | 81篇 |
地质学 | 108篇 |
海洋学 | 33篇 |
天文学 | 42篇 |
综合类 | 1篇 |
自然地理 | 29篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 14篇 |
2019年 | 7篇 |
2018年 | 22篇 |
2017年 | 14篇 |
2016年 | 14篇 |
2015年 | 19篇 |
2014年 | 19篇 |
2013年 | 17篇 |
2012年 | 18篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 26篇 |
2008年 | 15篇 |
2007年 | 11篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有333条查询结果,搜索用时 15 毫秒
81.
Bérénice Preller Julia Affolderbach Christian Schulz Sebastian Fastenrath Boris Braun 《The Professional geographer》2017,69(2):214-224
Knowledge coproduction between practitioners and scientists offers promising opportunities for the emerging research field of the geography of sustainability transitions. Drawing on experiences from an international research project on urban green building transitions, this article explores the potentials and challenges of interactive and collaborative knowledge generation methods in understanding sustainability transitions. Our results show that ongoing engagement with local experts and practitioners through interactive World Café workshops and follow-up exchanges allows for a better understanding of the research context and knowledge exchange to all participants involved in the research process. 相似文献
82.
83.
Meiobenthos in Nha trang bay of the south China sea (Vietnam) 总被引:1,自引:0,他引:1
The distribution of the taxonomical composition and the density of meiobenthos depending on the sediment type has been studied
in bottom sediments of Nha Trang Bay. The maximal population density and the taxonomical diversity were observed in the silted
coarse and heterogeneous sand (1031.4μ419.7 ind. 10 cm-2), whereas the minimal level of density and diversity (588.1μ152.5 ind. 10 cm-2) was in the coarse and heterogeneous sand with shell debris and corals. The correlation between the median diameter of sediment
particles and population density of meiobenthos has been revealed (r=0.82, p<0.05). In bottom sediments of Nha Trang Bay,
twenty six taxonomic groups of meiobenthos were observed. Nematodes dominated in all sediment types. Representatives of four
orders, twenty eight families and ninety seven genera of marine nematodes were identified. The vertical distribution of meiobenthos
in different sediment types was considered. A sediment column (10 cm height) was sectioned by five 2 cm portions. In the last
layer (8-10 cm) the most number of meiobenthic groups was found in sandy sediments. In the lower layers of silt sediments,
only nematodes were found. 相似文献
84.
Julia Uitz Hervé Claustre F. Brian Griffiths Joséphine Ras Nicole Garcia Valérie Sandroni 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(4):541-560
As part of the KErguelen: compared study of the Ocean and the Plateau in Surface water (KEOPS) project in late summer 2005, we examine the phytoplankton community composition and associated primary production in the waters surrounding the Kerguelen Archipelago, with the emphasis on two contrasted environments: (i) the Kerguelen Plateau, where a large bloom occurs annually, and (ii) the high-nutrient low-chlorophyll (HNLC) offshore waters. A biomarker pigment approach was used to assess the community composition in terms of chlorophyll biomass of three phytoplankton size classes, namely micro-, nano-, and picophytoplankton. The second objective was to evaluate a global class-specific approach for estimating the contribution of the three pigment-based size classes to the primary production in the study area. To do so, primary production rates associated with each phytoplankton class were computed from the class-specific chlorophyll biomass coupled to a class-specific primary production model, and compared with in situ measurements of size-fractionated 13C-based primary production. The iron-enriched bloom region was dominated by microphytoplankton (diatoms), which contributed 80–90% to the total primary production (of ≈1 g C m?2 d?1). In the HNLC area, the primary production was about 0.30 g C m?2 d?1, mainly (65%) achieved by small diatoms and nanoflagellates. The model results show a good overall agreement between predicted and measured total primary production rates. In terms of size classes, agreements were higher for the bloom region than for the HNLC waters. Discrepancies in this complex iron-limited area may be explained essentially by the smaller size of diatoms, or a different set of photophysiological properties. 相似文献
85.
The Chan Hol cave near Tulum (Quintana Roo,Mexico): evidence for long‐lasting human presence during the early to middle Holocene 下载免费PDF全文
86.
Around the world, long-term changes in the timing and magnitude of streamflow are testing the ability of large managed water resource systems constructed in the 20th century to continue to meet objectives in the 21st century. Streamflow records for unregulated rivers upstream of reservoirs can be combined with records downstream of reservoirs using a paired-watershed framework and concepts of water resource system performance to assess how reservoir management has responded to long-term change. Using publicly available data, this study quantified how the intra-annual timing of inflows and outflows of 25 major reservoirs has shifted, how management has responded, and how this has influenced reliability and vulnerability of the water resource system in the 668,000 km2 Columbia River basin from 1950 to 2012. Reservoir inflows increased slightly in early spring and declined in late spring to early fall, but reservoir outflows increased in late summer from 1950 to 2012. Average inflows to reservoirs in the low flow period exceeded outflows in the1950s, but inflows are now less than outflows. Reservoirs have increased hedging, that is, they have stored more water during the spring, in order to meet the widening gap between inflows and outflows during the summer low flow period. For a given level of reliability (the fraction of time flow targets were met), vulnerability (the maximum departure from the flow target) was greater during periods with lower than average inflows. Thus, the water management system in this large river basin has adjusted to multi-decade trends of declining inflows, but vulnerability, that is, the potential for excess releases in spring and shortfalls in summer, has increased. This study demonstrates the value of combining publicly available historical data on streamflow with concepts from paired-watershed analyses and metrics of water resource performance to detect, evaluate, and manage water resource systems in large river basins. 相似文献
87.
88.
Merrifield Mark A. Johnson Mele Guza R. T. Fiedler Julia W. Young Adam P. Henderson Cassandra S. Lange Athina M. Z. O’Reilly William C. Ludka Bonnie C. Okihiro Michele Gallien Timu Pappas Kyle Engeman Laura Behrens James Terrill Eric 《Natural Hazards》2021,108(3):2591-2612
Natural Hazards - Waves overtop berms and seawalls along the shoreline of Imperial Beach (IB), CA when energetic winter swell and high tide coincide. These intermittent, few-hour long events flood... 相似文献
89.
Stefanie Brachfeld Deepa Shah Emily First Julia Hammer Julie Bowles 《Meteoritics & planetary science》2015,50(10):1703-1717
We evaluate the relationship between the intensity of remanent magnetization and fO2 in natural and synthetic Mars meteorites. The olivine‐phyric shergottite meteorite Yamato 980459 (Y‐980459) and a sulfur‐free synthetic analog (Y‐98*) of identical major element composition were analyzed to explore the rock magnetic and remanence properties of a basalt crystallized from a primitive melt, and to explore the role of magmatic and alteration environment fO2 on Mars crustal anomalies. The reducing conditions under which Y‐980459 is estimated to have formed (QFM‐2.5; Shearer et al. 2006) were replicated during the synthesis of Y‐98*. Y‐980459 contains pyrrhotite and chromite. Chromite is the only magnetic phase in Y‐98*. The remanence‐carrying capacity of Y‐980459 is comparable to other shergottites that formed in the fO2 range of QFM‐3 to QFM‐1. The remanence‐carrying capacity of these low fO2 basalts is 1–2 orders of magnitude too weak to account for the intense crustal anomalies observed in Mars's southern cratered highlands. Moderately oxidizing conditions of >QFM‐1, which are more commonly observed in nakhlites and Noachian breccias, are key to generating either a primary igneous assemblage or secondary alteration assemblage capable of acquiring an intense remanent magnetization, regardless of the basalt character or thermal history. This suggests that if igneous rocks are responsible for the intensely magnetized crust, these oxidizing conditions must have existed in the magmatic plumbing systems of early Mars or must have existed in the crust during secondary processes that led to acquisition of a chemical remanent magnetization. 相似文献
90.
Menone ML Miglioranza KS Botto F Iribarne O Aizpún de Moreno JE Moreno VJ 《Marine pollution bulletin》2006,52(12):1717-1724
The influence of intertidal crab beds on the concentrations of organochlorine (OC) pesticides in sediment was studied in two different coastal environments in Argentina. Samples of male burrowing crabs (Chasmagnathus granulatus) were collected for this study. Our field data showed lower bioaccumulation of OC pesticides in crabs from sediments with a higher total organic carbon (TOC) and higher clay content. Thus, concentrations in crabs depend on the physico-chemical characteristics of the sediment where they live more than on the OC pesticide concentrations in the environment. The distribution patterns in sediment from inside and outside crab burrows were similar for both coastal areas being HCHs γ-chlordane > p,p′-DDE for San Antonio Bay (SAO), and HCHs > p,p′-DDE γ-chlordane for Mar Chiquita (MCh) coastal lagoon. OC pesticide concentrations in sediment were significantly lower inside than outside crab burrows, irrespective of the sediment physico-chemical characteristics due to the bioturbation activity of C. granulatus. 相似文献