全文获取类型
收费全文 | 13192篇 |
免费 | 3753篇 |
国内免费 | 2397篇 |
专业分类
测绘学 | 991篇 |
大气科学 | 2903篇 |
地球物理 | 3285篇 |
地质学 | 6877篇 |
海洋学 | 1719篇 |
天文学 | 760篇 |
综合类 | 1259篇 |
自然地理 | 1548篇 |
出版年
2025年 | 13篇 |
2024年 | 322篇 |
2023年 | 385篇 |
2022年 | 697篇 |
2021年 | 762篇 |
2020年 | 677篇 |
2019年 | 748篇 |
2018年 | 688篇 |
2017年 | 689篇 |
2016年 | 785篇 |
2015年 | 636篇 |
2014年 | 800篇 |
2013年 | 752篇 |
2012年 | 709篇 |
2011年 | 685篇 |
2010年 | 775篇 |
2009年 | 669篇 |
2008年 | 634篇 |
2007年 | 613篇 |
2006年 | 499篇 |
2005年 | 476篇 |
2004年 | 358篇 |
2003年 | 377篇 |
2002年 | 368篇 |
2001年 | 391篇 |
2000年 | 392篇 |
1999年 | 597篇 |
1998年 | 503篇 |
1997年 | 454篇 |
1996年 | 473篇 |
1995年 | 400篇 |
1994年 | 346篇 |
1993年 | 322篇 |
1992年 | 268篇 |
1991年 | 205篇 |
1990年 | 172篇 |
1989年 | 136篇 |
1988年 | 136篇 |
1987年 | 73篇 |
1986年 | 63篇 |
1985年 | 52篇 |
1984年 | 38篇 |
1983年 | 29篇 |
1982年 | 37篇 |
1981年 | 32篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 7篇 |
1976年 | 9篇 |
1958年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
从分析区内水文地质特征入手,根据武平县悦洋银多金属矿区、上杭县古石背铀矿床、上杭县紫金山铜金矿区西北矿段铜矿床等水文地质特征,提出该区矿床水文地质勘探,应查明构造断裂带的特征,采用多种勘探方法相结合,加强地下水长期观测,正确地查明矿床水文地质条件和主要充水因素.准确预测矿坑涌水量。 相似文献
32.
获取了22景IW模式的Sentinel-1A/B数据,分别采用PS-InSAR和SBAS-InSAR两种时序技术得到了沧州地区2015年11月至2016年11月期间地表平均沉降速率及累计沉降量。经分析,两种时序监测结果具有较高的一致性,其结果表明:献县、沧县、沧州市区地面表现为回升趋势;青县、沧县东部、南皮县西部、东光县等地区地面沉降量较大,其中东光县何庄村累计下沉量达47 mm,而引起这些区域地面沉降的主要原因为农业生产等带来的地下水开采。本文对基于Sentinel-1A/B SAR数据的时序分析方法在城市沉降监测方面的应用进行了探讨,为有关部门提供了重要的参考数据。 相似文献
33.
对塔中低凸起地层水化学特征与不整合之间关系的研究结果表明,地层水化学特征对不整合具有很好的响应。在遭受强烈抬升和剥蚀、之间形成不整合的奥陶系和志留系,以及紧靠不整合面附近的石炭系CⅢ油组,其地层水具有矿化度、Cl-含量、K Na 含量和r(Cl-Na)/rMg值相对较小,而HCO3-含量、rNa/rCl值和rSO42-×100/rCl值相对较大的特点,反映出地质历史时期大气降水的影响。在志留系与石炭系之间以及志留系与奥陶系之间的不整合面附近,地层水的矿化度、r(Cl-Na)/rMg值和B3 含量变小,而rNa/rCl值和rSO24-×100/rCl值变大,具有典型的遭受大气淋滤的地层水化学基本特征。 相似文献
34.
For a Hamiltonian that can be separated into N+1(N\geq 2) integrable parts, four algorithms can be built for a symplectic integrator. This research compares these algorithms for the
first and second order integrators. We found that they have similar local truncation errors represented by error Hamiltonian
but rather different numerical stability. When the computation of the main part of the Hamiltonian, H
0, is not expensive, we recommend to use S
* type algorithm, which cuts the calculation of the H
0 system into several small time steps as Malhotra(1991) did. As to the order of the N+1 parts in one step calculation, we found that from the large to small would get a slower error accumulation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
35.
36.
The debris flow, which was triggered in the Wenjia Gully on August 13, 2010, is an extreme example of mass movement events, which occurred after the Wenchuan earthquake of May 12, 2008. This Earthquake triggered in the Wenjia Gully the second largest co-seismic landslide, which can be classified as a rockslide-debris avalanche. A lot of loose sediments was deposited in the basin. In the main so called Deposition Area II of this landslide, with a volume of 30?×?106?m3, flash floods can easily trigger debris flows because of the steep bottom slope and the relative small grain sizes of the sediments. The largest debris flow of August 13, 2010 destroyed the most downstream dam in the catchment during a heavy rain storm. The debris flow with a peak discharge of 1,530?m3/s and a total volume of 3.1?×?106?m3 caused the death of 7 persons, 5 persons were missing, 39 persons were injured and 479 houses buried. After three rainy seasons, only 16?% of the landslide-debris deposition was taken away by 5 large-scale debris flow events. Since the threshold for rainfall triggered debris flows in the Wenjia Gully and other catchments drastically decreased after the Wenchuan Earthquake, new catastrophic events are expected in the future during the rainy season. 相似文献
37.
38.
Crustal structure beneath the Songpan—Garze orogenic belt 总被引:2,自引:0,他引:2
The Benzilan-Tangke deepseismic sounding profile in the western Sichuan region passes through the Song-pan-Garze orogenic belt with trend of NNE.Based on the travel times and the related amplitudes of phases in the record sections,the 2-D P-wave crustal structure was ascertained in this paper.The velocity structure has quite strong lateral variation along the profile.The crust is divided into 5layers,where the first,second and third layer belong to the upper crust,the forth and fifth layer belong to the lower crust.The low velocity anomaly zone gener-ally exists in the central part of the upper crust on the profile,and it integrates into the overlying low velocity basement in the area to the north of Ma‘erkang.The crustal structure in the section can be divided into 4parts:in the south of Garze-litang fault,between Garze-Litang fault and Xianshuihe fault,between Xianshuihe fault and Longriba fault and in the north of Longriba fault,which are basically coincided with the regional tectonics division.The crustal thickness decreases from southwest to northeast along the profile,that is ,from62km in the region of the Jinshajiang River to 52km in the region of the Yellow River.The Moho discontinuity does not obviously change across the Xianshuihe fault basesd on the PmP phase analysis.The crustal average velocity along the profile is lower,about 6.30 km/s.The Benzilan-Tangke profile reveals that the crust in the study area is orogenic.The Xianshuihe fault belt is located in the central part of the profile,and the velocity is positive anomaly on the upper crust,and negative anomaly on the lower crust and upper mantle.It is considered as a deep tectonhic setting in favor of strong earthquake‘s accumulation and occurrence. 相似文献
39.
???????????????????????У?????????????б?????У???λ??У??????10 nm?? 相似文献
40.