全文获取类型
收费全文 | 520篇 |
免费 | 17篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 18篇 |
大气科学 | 57篇 |
地球物理 | 93篇 |
地质学 | 165篇 |
海洋学 | 67篇 |
天文学 | 70篇 |
综合类 | 1篇 |
自然地理 | 70篇 |
出版年
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 11篇 |
2014年 | 19篇 |
2013年 | 48篇 |
2012年 | 18篇 |
2011年 | 25篇 |
2010年 | 23篇 |
2009年 | 28篇 |
2008年 | 23篇 |
2007年 | 15篇 |
2006年 | 26篇 |
2005年 | 9篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 11篇 |
1999年 | 17篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1920年 | 1篇 |
排序方式: 共有541条查询结果,搜索用时 31 毫秒
511.
Structural damage in the cities of Reggiolo and Carpi after the earthquake on May 2012 in Emilia Romagna 总被引:2,自引:2,他引:0
Marco Andreini Anna De Falco Linda Giresini Mauro Sassu 《Bulletin of Earthquake Engineering》2014,12(5):2445-2480
This paper addresses the structural damage to the main buildings of the cities of Reggiolo and Carpi after the primary earthquake shocks on May 20th and 29th, 2012, in Emilia Romagna. The damage survey, performed via form-based methods, highlights the different seismic behaviour of several types of buildings, especially those having historical features, and the consequences of the damage in terms of costs. Moreover, an analysis of some failure mechanisms activated in Reggiolo enables the evaluation of the local peak ground acceleration, due to the soil amplification. 相似文献
512.
L.?S.?CampbellEmail author A.?Dyer C.?Williams P.?R.?Lythgoe 《Mineralium Deposita》2012,47(4):371-382
Rapid and progressive reaction of alkaline–carbonatitic tuffs with magmatic and crustal fluids disguises their initial character
and origin. This is collectively indicated from (a) the extensive literature on zeolite formation from volcanic glass precursors
and alkaline fluids, (b) mineralogical characteristics of specific zeolite species, (c) a comparative review of global distributions
of alkaline–carbonatite suites and of zeolite minerals, and (d) new trace element data from zeolite samples. A unifying conceptual
model based on tectonic and geological settings, hydrological regime and mineralogy is presented that helps to explain the
global distributions and current understanding of occurrences. The model will assist in resource exploration by contributing
deeper understanding of the economically important bedded zeolite deposits and further, serve as a guide to the discovery
of new alkaline–carbonatitic suites, potentially of economic significance (metallic ores and rare earth elements). It follows
that future testing of the hypothesis will impact on models of natural carbon cycling as volcanic contributions of CO2 are reviewed. 相似文献
513.
Vector management is the primary method for reducing and preventing nonindigenous species (NIS) invasions and their ecological and economic consequences. This study was the first to examine the efficacy of in-water scrubbing using a submersible cleaning and maintenance platform (SCAMP) to prevent invertebrate species transfers from a heavily fouled obsolete vessel. Initially, prior to treatment, 37 species were recorded in a biofouling matrix that reached 30cm depth in some locations. The bryozoan Conopeum chesapeakensis, and bivalves Mytilopsis leucophaeata and Ischadium recurvum, were dominant sessile species that created structure, supporting mobile biota that included crabs and the associated parasitic barnacle Loxothylacus panopae. Scrubbing had the effect of significantly reducing organism extent and the number of species per sample, but a substantial and diverse (30 species) residual fouling community remained across the entire vessel. Further assessments of management options are needed to prevent potentially damaging NIS transfers. Additional measures taken within an integrated vector management (IVM) strategy may further improve invasion prevention measures. 相似文献
514.
Influence of rural land use on streamwater nutrients and their ecological significance 总被引:1,自引:0,他引:1
Helen P. Jarvie Paul J.A. Withers Robin Hodgkinson Adam Bates Margaret Neal Heather D. Wickham Sarah A. Harman Linda Armstrong 《Journal of Hydrology》2008,350(3-4):166-186
Concentrations and loads of N and P fractions were examined for lowland rivers, the Wye and Avon, draining a range of representative agricultural land-use types in two major UK river basins. Data collected over a 2-year period demonstrated important diffuse agricultural source contributions to N and P loads in these rivers. Ground water provided a major source of total dissolved nitrogen (TDN) loads, whereas near-surface sources provided a major contribution to total phosphorus (TP) loads. In terms of aquatic ecology, concentrations of nutrients, at times of eutrophication risk (spring and summer low flows) were of key environmental and management significance. Agricultural diffuse sources provided the major source of long-term P loads across the two basins. However, the results demonstrated the dominance of point-source contributions to TP and SRP concentrations at times of ecological risk. Point sources typically ‘tip the balance’ of dissolved inorganic P (soluble reactive P, SRP) above the 100 μg l−1 guideline value indicative of eutrophication risk. The significance of point sources for TP and SRP concentrations was shown by (a) the strong correlations between TP, SRP and B concentrations, using B as a tracer of sewage effluent, (b) the dominant contribution of SRP to TP concentrations and (c) the predominant pattern of dilution of SRP and B with flow. The clean Chalk streams draining low intensity grassland in areas of the Avon with sparse human settlement were oligotrophic and P limited with low SRP concentrations under spring and summer baseflows attributable to groundwater sources. The data provide important insights into the ecological functioning of different lowland stream systems. There was evidence of greater SRP losses and N-limitation in a stream which drains a pond system, demonstrating the importance of longer water residence times for biological nutrient uptake. 相似文献
515.
Wenshuai Li Xiao‐Ming Liu Linda V. Godfrey 《Geostandards and Geoanalytical Research》2019,43(2):261-276
The lithium isotope system can be an important tracer for various geological processes, especially tracing continental weathering. The key to this application is the accurate and precise determination of lithium isotopic composition. However, some of the previously established column separation methods are not well behaved when applied to chemically diverse materials, due to the significant variations in matrix/lithium ratios in some materials. Here, we report a new dual‐column system for lithium purification to achieve accurate and precise analysis of lithium isotopic compositions using a multi‐collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS). Compared with single‐column systems, our dual‐column system yielded a consistent elution range of the lithium‐bearing fraction (7–16 ml) for samples with a large range of lithium loads and matrix compositions, so that column re‐calibration is not required. In addition, this method achieved complete lithium recovery and low matrix interference (e.g., Na/Li ≤ 1) with a short elution time (~ 6 h, excluding evaporation), with the entire procedure completed in 1.5 days. We report high precision Li isotopic compositions in twelve chemically diverse materials including seawater, silicates, carbonates, manganese nodules and clays. New recommended Li isotopic values and associated uncertainties are presented as reference values for quality control and inter‐laboratory calibration for future research and were consistent with previously published data. However, significant lithium isotopic variances (~ 1‰) in BHVO‐2 from different batches suggest Li isotopic heterogeneity in this reference material and that Li isotopic studies using this reference material should be treated with caution. 相似文献
516.
Antonietta Quigg Linda Broach Winston Denton Roger Miranda 《Marine pollution bulletin》2009,58(6):896-904
The Dickinson Bayou watershed (near Houston, Texas, Gulf of Mexico) provides habitat for numerous coastally influenced communities of wildlife, including scores of birds and fish. Encroaching development and impervious surfaces are altering the habitat and degrading water quality. Herein we have defined the current health of the bayou using water quality data collected between 2000 and 2006. Elevated bacteria (fecal coliform, Escherichia coli and Enterococcus) and depressed dissolved oxygen concentrations (often <3 mg l−1) are the two major impairments to this ecosystem. While nutrient ratios indicate primary productivity may be nitrogen limited, concerns of eutrophication persist because the bayou has a low intrinsic flushing rate. Consistent with this is the magnitude of algal blooms (ca. 100 μg chl l−1) which often occur in spring/summer. The findings of this study will assist with the understanding of the influence of urban development on small watersheds. 相似文献
517.
David C. Booth 《Journal of Seismology》2010,14(2):197-207
A method is presented for deriving 1-D velocity depth models from earthquake bulletin data. The models can be used as initial
models for more advanced modelling techniques such as tomographic inversion. The method is useful when there is little or
no refraction and long-range reflection survey data. The bulletin travel times are subjected to an analysis of variance, where
they are separated into source, distance, and receiving station terms. The distance terms describe the variation of travel
time with distance, and the associated trend lines allow 1-D velocity models for the crustal layers to be determined. The
velocity models provide an average crustal model for the region derived from local data. This does not include superficial
layers which are necessarily poorly determined. Earthquake bulletin P-wave data from propagation paths across three different
regions of the UK are employed to illustrate the use of the technique. 相似文献
518.
Coakley L 《Irish geography : bulletin of the Geographical Society of Ireland》2010,43(2):105-117
Since 2004, Polish food has become firmly embedded in the Irish foodscape as Polish shops opened up in cities and towns across Ireland. The aim of this article is to develop an understanding of the significance and meaning of these Polish shops within the Irish foodscape. In order to achieve this I will take a more-than-representational approach focusing on the practices, sensory reactions and material interactions Poles have within these stores and with their food products. The article will draw on ethnographic observations and semi-structured interviews with Polish migrants to explore their experiences. Attention to these details reveals how Polish shops become meaningful within the Irish foodscape for providing a sense of home to Polish migrants living in Ireland. 相似文献
519.
520.
The island of Ischia belongs to the active volcanic area of Naples. It is formed from Quaternary volcanic rocks and exhibits intense hydrothermal activity, which is manifested through numerous springs, fumaroles and sporadic geysers. The content of minor and trace elements in groundwater has been analyzed, including some elements that are considered toxic for humans. Mean concentrations of As, B, Fe, Mn, Sb, and Se in samples from 43 aquifer points exceed the WHO recommended values and the limits set by European and Italian legislation (98/83/CE and DM 471, respectively). In general, the spatial distribution of the elements follows a common pattern: it is governed by a marked structural control, which favors hydrochemical processes that liberate the elements into the water. 相似文献