全文获取类型
收费全文 | 736篇 |
免费 | 155篇 |
国内免费 | 224篇 |
专业分类
测绘学 | 57篇 |
大气科学 | 184篇 |
地球物理 | 206篇 |
地质学 | 426篇 |
海洋学 | 95篇 |
天文学 | 36篇 |
综合类 | 65篇 |
自然地理 | 46篇 |
出版年
2024年 | 5篇 |
2023年 | 16篇 |
2022年 | 33篇 |
2021年 | 36篇 |
2020年 | 44篇 |
2019年 | 37篇 |
2018年 | 38篇 |
2017年 | 33篇 |
2016年 | 50篇 |
2015年 | 46篇 |
2014年 | 34篇 |
2013年 | 46篇 |
2012年 | 45篇 |
2011年 | 40篇 |
2010年 | 41篇 |
2009年 | 41篇 |
2008年 | 28篇 |
2007年 | 48篇 |
2006年 | 27篇 |
2005年 | 30篇 |
2004年 | 25篇 |
2003年 | 21篇 |
2002年 | 20篇 |
2001年 | 18篇 |
2000年 | 35篇 |
1999年 | 52篇 |
1998年 | 38篇 |
1997年 | 35篇 |
1996年 | 25篇 |
1995年 | 21篇 |
1994年 | 16篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1958年 | 4篇 |
排序方式: 共有1115条查询结果,搜索用时 31 毫秒
131.
山西临汾奥陶纪马家沟组顶底与上覆和下伏地层呈平行不整合,是一套沉积于广阔陆表海浅水台地上的碳酸盐、蒸发岩潮坪层序。泥晶石灰岩、白云岩、蒸发岩等岩石类型和沉积构造如鸟眼、干裂、石膏、石盐假晶、叠层石等反映出来的旋回性清晰明显。在野外共划分出了84个旋回层,用Fischer图解对马家沟组的旋回层序进行了分析,共划分出3个三级旋回,12个四级旋回。84个旋回层可能是因地球偏心率变化而引起的米兰柯维奇旋回 相似文献
132.
Cong Chen Xiangtao Zhang Guangrong Peng Zulie Long Baojun Liu Xudong Wang Puqiang Zhai Bo Zhang 《海洋学报(英文版)》2023,42(3):189-200
The eastern main sub-sag (E-MSS) of the Baiyun Sag was the main zone for gas exploration in the deep-water area of the Zhujiang River (Pearl River) Mouth Basin at its early exploration stage, but the main goal of searching gas in this area was broken through by the successful exploration of the W3-2 and H34B volatile oil reservoirs, which provides a new insight for exploration of the Paleogene oil reservoirs in the E-MSS. Nevertheless, it is not clear on the distribution of “gas accumulated in the upper layer, oil accumulated in the lower layer” (Gasupper-Oillower) under the high heat flow, different source-rock beds, multi-stages of oil and gas charge, and multi-fluid phases, and not yet a definite understanding of the genetic relationship and formation mechanism among volatile oil, light oil and condensate gas reservoirs, and the migration and sequential charge model of oil and gas. These puzzles directly lead to the lack of a clear direction for oil exploration and drilling zone in this area. In this work, the PVT fluid phase, the origin of crude oil and condensate, the secondary alteration of oil and gas reservoirs, the evolution sequence of oil and gas formation, the phase state of oil and gas migration, and the configuration of fault activity were analyzed, which established the migration and accumulation model of Gasupper-Oillower co-controlled by source and heat, and fractionation controlled by facies in the E-MSS. Meanwhile, the fractionation evolution model among common black reservoirs, volatile reservoirs, condensate reservoirs and gas reservoirs is discussed, which proposed that the distribution pattern of Gasupper-Oillower in the E-MSS is controlled by the generation attribute of oil and gas from source rocks, the difference of thermal evolution, and the fractionation controlled by phases after mixing the oil and gas. Overall, we suggest that residual oil reservoirs should be found in the lower strata of the discovered gas reservoirs in the oil-source fault and diapir-developed areas, while volatile oil reservoirs should be found in the deeper strata near the sag with no oil-source fault area. 相似文献
133.
The Ediacaran Doushantuo Formation with well-preserved fossil record in South China provides a rare window for our understanding of biological evolution,global carbon cycle,and oceanic redox states.Prominent negativeδ~(13)C anomalies(i.e.,the Shuram excursion)in Ediacaran successions worldwide fundamentally challenge the traditional models of isotopic mass balance.Additionally,conflicting opinions of both oxic and anoxic conditions have been proposed for the deep waters during this period.Here,we present a detailed study of pyrite morphology and carbonate carbon isotope data documented from drill core samples at Songtao County,northeastern Guizhou.Framboid aggregates are the dominant pyrite form in black shale and they can transfer to euhedral crystals through continuous growth of the constituent microcrystals.A positive correlation between microcrystal sizes(d)and framboid diameters(D)is observed,while the different D/d ratios of framboids in argillaceous dolostone and black shale reflect different substrate availability.Electron microprobe analyses reveal no consistent compositional patterns between framboidal and euhedral pyrites.Framboid size distributions of the investigated drill core,in combination with previously published redox data from the intra-shelf Jiulongwan section,shelf margin Zhongling section,and lower slope Wuhe section,suggest that three episodes of marine euxinia have been established throughout the deposition of the Doushantuo Formation.The time lag between the uppermost euxinic interval and the Shuram excursion may arise from the depression of sulfate reduction maintained by other oxidants. 相似文献
134.
In this paper, the data of earthquake events of magnitude MS6.0 and above produced in Hohhot Seismic Station from 2008 to 2015 and the data of ML ≥ 1.0 seismic events from 2015 to 2016 in Horinger Seismic Station and the surrounding mobile stations in southern Hohhot are selected. Using Splitlab and SAM software, the spin-correlation method, the least-energy method and the cross-correlation coefficient method are used to analyze the teleseismic and near-seismic phases (SKS, S). The results of this study are in good agreement with the results previously obtained by other researchers. The study of teleseismic SKS splitting reflects the characteristics of the anisotropy of the upper mantle beneath Hohhot, that is, the anisotropy of the upper mantle shows NW, which reflects "fossil" Anisotropy, mainly in the continental structure of stable units and preserves the history of mantle deformation information. The crustal anisotropy reflected by the near-earthquake S-wave splitting study is similar to that of the active fault zone, trending NE as a whole and is consistent with the tectonic stress field background of the northeastern margin of Ordos block. 相似文献
135.
2017年6月3日阿拉善左旗5.0级地震震源深度测定 总被引:1,自引:1,他引:0
2017年6月3日18时11分内蒙古阿拉善左旗(37.99° N,103.56° E)发生5.0级地震,利用近震深度震相sPL测定法、CAP波形反演法、sPn与Pn震相走时差法,进行震源深度精确测定。研究结果表明,3种方法测得的该地震震源深度基本一致,分布范围为8.5—11 km,表明该地震发生在上地壳。 相似文献
136.
137.
138.
均匀设计在紫球藻培养基优化中的应用 总被引:3,自引:0,他引:3
将均匀设计的方法应用于紫球藻 ( Porphyridium cruentum) 培养基的优化。在单因素实验的基础上,采用 U12(12 ×6) 均匀设计表对影响紫球藻生长显著的 4 种主要营养因素进行了优化,获得了以海水 3为 基 础 的 优 化 培 养 基 配 方 : NaHCO3: 2.755 g/L , NaNO3: 3.224 g/L , KH2PO : 0.035 g/L , VB12: 42.772 μg/L,VB1: 0.9 mg/L,Fe-EDTA: 0.11 mg/L,有效地提高了紫球藻的生物量产量和生长速率。 相似文献
139.
为厘清季冻土区临水内、外拱护墙结构冻胀平位移冻害机理,测试隔离层防冻害装置的有效性,在20101110-20110531、20131110-20140531、20171110-20180531三个观测年内,以长春某湖泊临水内、外拱护墙结构为研究对象,选择内、外拱护墙结构和设隔离层防冻害装置的试验内拱护墙结构三者相对比,用钢尺量距法观测三者寒期的平位移状态。结果表明:内拱护墙结构出现倾斜、裂缝导致的内向冻胀平位移冻害,其内向平位移曲线随气温均呈"半驼峰型",对应观测年持续降温-持续低温-持续升温-正温时段,内向冻胀平位移呈减小-增大-减小-稳定残余的位移运动,诱因是平冻胀应力的生成-增长-减弱-消失作用;外拱护墙结构出现较小的外向冻胀平位移,外向冻胀平位移曲线均呈"波浪型",无冻害发生,冰凸拱平冻胀应力推动外拱护墙结构压缩冻土凹拱形成外向冻胀平位移,冻土凹拱限制了外向冻胀平位移发展;设隔离层防冻害装置的试验内拱护墙结构未发生平位移冻害,其内向冻胀平位移较自然冻胀的内拱护墙结构减小83.92%,较外拱护墙结构减小51.74%,表明隔离层防冻害装置防治冻胀平位移冻害有效。 相似文献
140.
本文是作者关于“数学形态学与数字地图图像的分析和识别”研究成果的一部分。文章提出了地图图形的集合概念和地图图像形态分析的基元确定原则,证明了结构元素的基元最小分解定理;同时,介绍了基本的形态学变换,统一并扩展了带约束条件的数学形态学变换模型;从而,奠定了数字地图图像分析和识别的数学基础。 相似文献