全文获取类型
收费全文 | 418篇 |
免费 | 22篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 32篇 |
地球物理 | 85篇 |
地质学 | 165篇 |
海洋学 | 55篇 |
天文学 | 48篇 |
综合类 | 1篇 |
自然地理 | 44篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 15篇 |
2015年 | 4篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 24篇 |
2011年 | 24篇 |
2010年 | 17篇 |
2009年 | 22篇 |
2008年 | 22篇 |
2007年 | 22篇 |
2006年 | 15篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 7篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1956年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有446条查询结果,搜索用时 31 毫秒
171.
James R. C. Garry Inge Loes ten Kate Zita Martins Per Nrnberg Pascale Ehrenfreund 《Meteoritics & planetary science》2006,41(3):391-405
Abstract— We have investigated the native amino acid composition of two analogs of Martian soil, JSC Mars‐1 and Salten Skov. A Mars simulation chamber has been built and used to expose samples of these analogs to temperature and lighting conditions similar to those found at low latitudes on the Martian surface. The effects of the simulated conditions have been examined using high‐performance liquid chromatography (HPLC). Exposure to energetic ultraviolet (UV) light in vacuum appears to cause a modest increase in the concentration of certain amino acids within the materials, which is interpreted as resulting from the degradation of microorganisms. The influence of low temperatures shows that the accretion of condensed water on the soils leads to the destruction of amino acids, supporting the idea that reactive chemical processes involving H2O are at work within the Martian soil. We discuss the influence of UV radiation, low temperatures, and gaseous CO2 on the intrinsic amino acid composition of Martian soil analogs and describe, with the help of a simple model, how these studies fit within the framework of life detection on Mars and the practical tasks of choosing and using Martian regolith analogs in planetary research. 相似文献
172.
173.
174.
175.
Jakob Abermann Kirsty Langley Sille M. Myreng Kerstin Rasmussen Dorthe Petersen 《水文研究》2021,35(11):e14413
The majority of freshwater input from Greenland to the global ocean stems from the Greenland Ice Sheet. Currently, almost a quarter of the freshwater flowing from Greenland is derived from catchments that are disconnected from the Greenland Ice Sheet. Despite their importance to the total freshwater flux and influence on fjord geochemistry, there is relatively little monitoring data available for those catchments and therefore the drivers of regional differences in export are largely unknown. We present a dataset of 12 years of discharge of four catchments less than 15 km apart, that are different in size (between 7 and 32 km2), local glacier coverage (4%–11%) and lake cover (0%–5%). They all drain into Kobbefjord, a well-studied fjord in West Greenland, near Greenland's capital Nuuk. Between catchments, the magnitude of discharge varies at annual, seasonal and sub-daily timescales, due to differences in physical catchment properties as well as local climate variability. We find that annual specific discharges vary greatly (between 1.2 and 1.9 m/year on a 12-year average) due to a longitudinal precipitation gradient from West to East caused by different amount of orographic precipitation shading. The seasonal cycle of discharge (amplitude, timing and minimum flow) differs among the sites mainly due to different exposure to solar radiation as a driver for major snowmelt; the small ice coverage in the catchments plays only a minor role in discharge variability. Dry years generally increase the relative differences in annual specific discharge and no significant temporal trends have been found in the studied catchments. On a sub-daily timescale, the difference in timing of maximum discharge during fair-weather days (>80% maximum solar radiation and no precipitation) ranged between 7 and 12 h, which is attributed to differences between the presence and elevation of lakes among the catchments. The response of discharge to major precipitation events is discussed, where a delay of between 5 and 7 h is found for the catchments that do not contain lakes near the gauge. 相似文献
176.
F.M. Zerbi H. Dekker I. Guinouard R. Navarro P.K. Rasmussen 《Astronomische Nachrichten》2011,332(3):218-221
One year of operations demonstrated the high level of scientific performance of the X‐shooter spectrograph. The excellent science opened by this instrument is described in various papers within this volume. The purpose of this contribution is to briefly describe the novel technical solution adopted in the design and construction phase of X‐shooter that made it a successful instrument and the aforementioned science possible (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
177.
Abstract An experiment was designed to compare ground‐based methods of nitrogen (N) stress detection with N stress detection using remote sensing. The study area, located in Minidoka, Idaho, is a 64 ha center pivot with a crop of Penawawa spring white wheat. Nitrogen was varied on four transects approximately 40 m wide and 805 m long. The N application rates chosen for the research were 0%, 40%, 100%, and 130% of normal. Nitrogen deficiency was quantified from tissue sampling, which was used as the response variable. Nitrogen was then measured or estimated at key stages in the wheat growth cycle using visual observation, a chlorophyll meter, and remotely‐sensed data. Visual observation was the normally‐employed method for area farmers. These methods of N stress detection were compared for accuracy, timeliness, usefulness, and cost. Remote sensing was comparable to the chlorophyll meter in accuracy. The chlorophyll meter was the timeliest method for obtaining a quantitative measurement. 相似文献
178.
Using an empirical study of a political protest, this paper examines a set of interdependent contracts symbolizing both the nodes of scalar interaction and the hegemonic nodes of resistance. The study focuses on a contentious political campaign aimed at the City of Cincinnati, a recycling facility, and a day labor temp agency initiated by contracted day laborers who hand-sorted garbage from recycling materials and suffered from adverse working conditions and alleged wage violations. A discussion of the rise of contingent labor through implementation of neoliberal deregulation policies is integrated with Jürgen Habermas' concepts of the lifeworld and the system providing an explanatory framework for understanding lifeworld colonization through flexible labor practices and the subsequent impetus behind the contentious political campaign. Using survey data, the shared lifeworld of day laborers is described. The study also examines how the position of protest participants affected the tactics and outcomes of the contestation. [Key words: day labor, contingent labor, living wage ordinances, Habermas.] 相似文献
179.
180.
Frode Georgsen Per R?e Anne Randi Syversveen Oddvar Lia 《Computational Geosciences》2012,16(2):247-259
In history matching and sensitivity analysis, flexibility in the structural modelling is of great importance. The ability
to easily generate multiple realizations of the model will have impact both on the updating workflow in history matching and
uncertainty studies based on Monte Carlo simulations. The main contribution to fault modelling by the work presented in this
paper is a new algorithm for calculating a 3D displacement field applicable to a wide range of faults due to a flexible representation.
This gives the possibility to apply this field to change the displacement and thereby moving horizons and fault lines. The
fault is modelled by a parametric format where the fault has a reference plane defined by a centre point, dip and strike angles.
The fault itself is represented as a surface defined by a function z = f(x,y), where x, y and z are coordinates local to the reference plane, with the z-axis being normal to the plane. The displacement associated with the fault outside the fault surface is described by a 3D
vector field. The displacement on the fault surface can be found by identifying the intersection lines between horizons and
the fault surface (fault lines), and using kriging techniques to fill in values at all points on the surface. Away from the
fault surface the displacement field is defined by a monotonic decreasing function which ensures zero displacement at a specified
distance from the fault. An algorithm is developed where the displacement can be increased or decreased according to user-defined
parameters. This means that the whole displacement field is changed and points on horizons around the fault can be moved accordingly
by applying the modified displacement field on them. The interaction between several faults influencing the same points is
taken care of by truncation rules and the ordering of the faults. The method is demonstrated on a realistic synthetic case
based on a real reservoir. 相似文献