全文获取类型
收费全文 | 37076篇 |
免费 | 6001篇 |
国内免费 | 8027篇 |
专业分类
测绘学 | 3413篇 |
大气科学 | 4595篇 |
地球物理 | 6425篇 |
地质学 | 20203篇 |
海洋学 | 5042篇 |
天文学 | 3367篇 |
综合类 | 2324篇 |
自然地理 | 5735篇 |
出版年
2024年 | 246篇 |
2023年 | 660篇 |
2022年 | 1335篇 |
2021年 | 1538篇 |
2020年 | 1428篇 |
2019年 | 1758篇 |
2018年 | 1233篇 |
2017年 | 1471篇 |
2016年 | 1516篇 |
2015年 | 1636篇 |
2014年 | 2080篇 |
2013年 | 2076篇 |
2012年 | 2127篇 |
2011年 | 2275篇 |
2010年 | 2029篇 |
2009年 | 2532篇 |
2008年 | 2488篇 |
2007年 | 2520篇 |
2006年 | 2449篇 |
2005年 | 2319篇 |
2004年 | 1993篇 |
2003年 | 1923篇 |
2002年 | 1674篇 |
2001年 | 1462篇 |
2000年 | 1469篇 |
1999年 | 1276篇 |
1998年 | 1112篇 |
1997年 | 785篇 |
1996年 | 680篇 |
1995年 | 589篇 |
1994年 | 547篇 |
1993年 | 460篇 |
1992年 | 326篇 |
1991年 | 294篇 |
1990年 | 203篇 |
1989年 | 155篇 |
1988年 | 130篇 |
1987年 | 77篇 |
1986年 | 45篇 |
1985年 | 36篇 |
1984年 | 26篇 |
1983年 | 23篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 15篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
山东是饮用天然矿泉水资源大省 ,点之多、量之丰居全国前列。到目前为止 ,已鉴定矿泉水 36 1处 ,其中锶型118处 ,偏硅酸型 6 4处 ,锶偏硅酸型 15 1处 ,碘型等其它类型 2 8处。这些矿泉水所赋存的岩石类型多、岩性复杂且受断裂构造控制明显 ;具有达标元素较单一、水化学类型复杂、矿化程度较低、单井允许开采量相差悬殊且地域分布不均等特点。勘查与评价重点是寻找奇缺且又可能存在的锌型、锂型、碳酸型矿泉水。开发好矿泉水资源、实行规模开发、打造本省名牌、加强矿泉水资源的卫生防护与保护 ,对于确保山东矿泉水资源的持续开发与利用具有重要意义。 相似文献
142.
FUZZY COMPREHENSIVE EVALUATION OF CONTAINER TRANSPORTATION MODES ALONG THE CHANGJIANG RIVER MAIN LINE AND ITS DELTA AREA 总被引:1,自引:0,他引:1
ZHANGShi-yu XIAOHan-liang 《中国地理科学(英文版)》2003,13(3):259-261
The Changjiang River (Yangtze) is one of the fastest growth areas of container transportation in Chi-na. Rail, road and water transportation have competed against each other for container transportation in the Chang-jiang River main line and its delta area. It is of significance to assess these different transportation modes scientifi-cally in order to organize container transportation efficiently in this area and make decision for integral plan and construction of transportation system in this area. This paper outlines application of fuzzy comprehensive evaluation to appraise different modes of typical direction of containers. Twelve assessment indexes were decided. Membership functions were formulated. Evaluation results indicated that road transportation was optimal mode in the Changjiang River delta area, however water transportation was the primary way in the Changjiang River main line. 相似文献
143.
144.
Continuous wavelet analyses of hourly time series of air temperature, stream discharge, and precipitation are used to compare the seasonal and inter‐annual variability in hydrological regimes of the two principal streams feeding Bow Lake, Banff National Park, Alberta: the glacial stream draining the Wapta Icefields, and the snowmelt‐fed Bow River. The goal is to understand how water sources and flow routing differ between the two catchments. Wavelet spectra and cross‐wavelet spectra were determined for air temperature and discharge from the two streams for summers (June–September) 1997–2000, and for rainfall and discharge for the summers of 1999 and 2000. The diurnal signal of the glacial runoff was orders of magnitude higher in 1998 than in other years, indicating that significant ice exposure and the development of channelized glacial drainage occurred as a result of the 1997–98 El Niño conditions. Early retreat of the snowpack in 1997 and 1998 led to a significant summer‐long input of melt runoff from a small area of ice cover in the Bow River catchment; but such inputs were not apparent in 1999 and 2000, when snow cover was more extensive. Rainfall had a stronger influence on runoff and followed quicker flow paths in the Bow River catchment than in the glacial catchment. Snowpack thickness and catchment size were the primary controls on the phase relationship between temperature and discharge at diurnal time scales. Wavelet analysis is a fast and effective means to characterize runoff, temperature, and precipitation regimes and their interrelationships and inter‐annual variability. The technique is effective at identifying inter‐annual and seasonal changes in the relative contributions of different water sources to runoff, and changes in the time required for routing of diurnal meltwater pulses through a catchment. However, it is less effective at identifying changes/differences in the type of the flow routing (e.g. overland flow versus through flow) between or within catchments. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
145.
146.
Miguel Cerviño 《Astrophysics and Space Science》2003,284(2):897-900
Evolutionary synthesis models have been used to study the physical properties of unresolved populations in a wide range of
scenarios. Unfortunately, their self-consistency is difficult to test and there are some theoretical open questions without
an answer: (1) The change of the homology relations assumed in the computation of isochrones due to the effect of stellar
winds (or rotation) and the discontinuities in the stellar evolution are not considered. (2) There is no consensus about how
the isochrones must be integrated. (3) The discreteness of the stellar populations (that produce an intrinsic statistical
dispersion) usually are not taken into account, and model results are interpreted in a deterministic way instead of a statistical
one. The objective of this contribution is to present some inconsistencies in the computation and some cautions in the application
of the results of such codes.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
147.
148.
149.
150.