全文获取类型
收费全文 | 712篇 |
免费 | 118篇 |
国内免费 | 63篇 |
专业分类
测绘学 | 55篇 |
大气科学 | 172篇 |
地球物理 | 266篇 |
地质学 | 124篇 |
海洋学 | 135篇 |
天文学 | 78篇 |
综合类 | 26篇 |
自然地理 | 37篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 14篇 |
2020年 | 15篇 |
2019年 | 27篇 |
2018年 | 18篇 |
2017年 | 20篇 |
2016年 | 29篇 |
2015年 | 21篇 |
2014年 | 25篇 |
2013年 | 41篇 |
2012年 | 27篇 |
2011年 | 33篇 |
2010年 | 29篇 |
2009年 | 45篇 |
2008年 | 56篇 |
2007年 | 44篇 |
2006年 | 43篇 |
2005年 | 42篇 |
2004年 | 35篇 |
2003年 | 21篇 |
2002年 | 23篇 |
2001年 | 25篇 |
2000年 | 33篇 |
1999年 | 33篇 |
1998年 | 32篇 |
1997年 | 18篇 |
1996年 | 29篇 |
1995年 | 14篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有893条查询结果,搜索用时 755 毫秒
101.
烃气测量法在锡、金、铜、铅锌等金属矿床找矿中得到了广泛应用,而该技术在花岗岩型铀矿找矿中的应用鲜有报道。本文对桂北376铀矿床已知矿体开展了烃气测量试验,结果显示:相较于其他金属矿,该铀矿区花岗岩和土壤中总烃含量极低,而且花岗岩总烃含量(平均19.42μL/kg)高于上覆土壤(平均6.32μL/kg)。花岗岩中U与多数烃气组分呈负相关,与重烃呈正相关,重烃在U迁移过程中作用强于轻烃;花岗岩烃气标准化配分模式以C1、iC4和C2-正异常为特征;铀矿化程度与iC4/nC4、(C1+iC4+C2-)/(C2+C3+nC4)及C2-/C3-比值呈正相关,与C2+/∑C比值呈负相关等可为寻找铀矿提供依据。3... 相似文献
102.
管鑫 《测绘与空间地理信息》2015,(2):202-203,206
本文从地铁床道测量的意义出发,结合轨道交通八号线二期工程,介绍了轨道交通整体床道测量技术设计、作业方法、数据采集、成果分析,以及在作业过程中的注意事项. 相似文献
103.
Trend and Interannual Variability of Chinese Air Pollution since 2000 in Association with Socioeconomic Development: A brief Overview 下载免费PDF全文
air pollution, trend and variability, socioeconomic development, satellite measurements, bottom-up emission inventories, top-down constraints 相似文献
104.
105.
1 IntroductionThroughoutthegeologicalhistory ,almostallthetectonicplateactivities,suchasearthquakes,volcaniceruption ,andmountainbuilding ,takeplaceatactiveplateboundaries.Forexample,approxi mately 90 percentoftheearthquakesoccuratactiveplateboundaries[1 - 4 ] ,andthehighestmountainsofTibetandAndesresultfromthecontinualcollisionbetweenIndiaandAsia ,NazcaandSouthAmericaplates,respectively .Aplateboundaryisafracturethatseparatesaplatefromanother;theneighboringplatesmoverelativetooneanotherin… 相似文献
106.
This review describes advances in radiative transfer theory since about 1985. We stress fundamental aspects and emphasize
modern methods for the numerical solution of the transfer equation for spatially multidimensional problems, for both unpolarized
and polarized radiation. We restrict the discussion to two-level atoms with noninverted populations for given temperature,
density and velocity fields.
Unfortunately this article was originally published with typesetter's errors: The correct publication date was 25 February
2006, not 3 January 2006. The content was not in the final form. The publishers wish to apologize for this mistake. The online
version of the original version can be found at /10.1007/s00159-005-0025-8. 相似文献
107.
Fast heuristically weighted, or pseudo-Cℓ, estimators are a frequently used method for estimating power spectra in CMB surveys with large numbers of pixels. Recently, Challinor and Chon showed that the E–B mixing in these estimators can become a dominant contaminant at low noise levels, ultimately limiting the gravity wave signal which can be detected on a finite patch of sky. We define a modified version of the estimators which eliminates E–B mixing and is near-optimal at all noise levels. 相似文献
108.
New laboratory and field data are presented on fluid advection into the swash zone. The data illustrate the region of the inner surf zone from which sediment can be directly advected into the swash zone during a single uprush, which is termed the advection length. Experiments were conducted by particle tracking in a Lagrangian reference frame, and were performed for monochromatic breaking waves, solitary bores, non-breaking solitary waves and field conditions. The advection length is normalised by the run-up length to give an advection ratio, A, and different advection ratios are identified on the basis of the experimental data. The data show that fluid enters the swash zone from a region of the inner surf zone that can extend a distance seaward of the bore collapse location that is approximately equal to half of the run-up length. This region is about eight times wider than the region predicted by the classical swash solution of Shen and Meyer [Shen, M.C., Meyer, R.E., 1963. Climb of a bore on a beach. Part 3. Runup. Journal of Fluid Mechanics 16, 113–125], as illustrated by Pritchard and Hogg [Pritchard, D., Hogg, A.J., 2005. On the transport of suspended sediment by a swash event on a plane beach. Coastal Engineering 52, 1–23]. Measured advection ratios for periodic waves show no significant trend with Iribarren number, consistent with self-similarity in typical swash flows. The data are compared to recent characteristic solutions of the non-linear shallow water wave (NLSW) equations and both finite difference and finite volume solutions of the NLSW equations. 相似文献
109.
B.R. Stanton 《Estuarine, Coastal and Shelf Science》1984,19(1):89-104
Four New Zealand fjords were surveyed in March and April 1980. In Milford Sound, unusually low dissolved oxygen levels in Stirling Basin suggests that intermittent stagnation events occur, while in Deep Water Basin the bottom water was virtually anoxic. Near the entrance to Milford Sound aperiodic currents up to 38 cm s?1 were recorded. In Isthmus Sound and Long Sound, in Preservation Inlet, contrasting circulation and mixing regimes were found and tidal currents up to 60 cm s?1 over the entrance sill to Long Sound are important for deep water renewal. 相似文献
110.
The authors identify a management approach to the problem of incidental catch and utilize that approach to evaluate six management options which are being considered to control incidental catch in the US fishery conservation zone of the Bering Sea. The evaluation is in terms of the ability of management to minimize the impact and control costs of incidental catch. The authors conclude that the use of economic disincentives tends to be preferable due to the inefficiencies and extensive information requirements of the alternative options. 相似文献