全文获取类型
收费全文 | 24931篇 |
免费 | 1876篇 |
国内免费 | 1833篇 |
专业分类
测绘学 | 1504篇 |
大气科学 | 2886篇 |
地球物理 | 5103篇 |
地质学 | 12261篇 |
海洋学 | 1462篇 |
天文学 | 1465篇 |
综合类 | 2308篇 |
自然地理 | 1651篇 |
出版年
2025年 | 7篇 |
2024年 | 106篇 |
2023年 | 169篇 |
2022年 | 269篇 |
2021年 | 314篇 |
2020年 | 274篇 |
2019年 | 303篇 |
2018年 | 4040篇 |
2017年 | 3457篇 |
2016年 | 2372篇 |
2015年 | 466篇 |
2014年 | 395篇 |
2013年 | 345篇 |
2012年 | 1045篇 |
2011年 | 2444篇 |
2010年 | 1835篇 |
2009年 | 2058篇 |
2008年 | 1762篇 |
2007年 | 2131篇 |
2006年 | 221篇 |
2005年 | 345篇 |
2004年 | 493篇 |
2003年 | 542篇 |
2002年 | 444篇 |
2001年 | 301篇 |
2000年 | 307篇 |
1999年 | 315篇 |
1998年 | 287篇 |
1997年 | 228篇 |
1996年 | 194篇 |
1995年 | 198篇 |
1994年 | 174篇 |
1993年 | 156篇 |
1992年 | 129篇 |
1991年 | 92篇 |
1990年 | 83篇 |
1989年 | 59篇 |
1988年 | 51篇 |
1987年 | 35篇 |
1986年 | 32篇 |
1985年 | 24篇 |
1984年 | 14篇 |
1983年 | 25篇 |
1982年 | 13篇 |
1981年 | 32篇 |
1980年 | 24篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1976年 | 6篇 |
1958年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
21.
22.
History matching is still one of the main challenging parts of reservoir study especially in giant brown oil fields with lots of wells. In these cases, history matching with conventional manual technique needs many runs and takes months to get a match. In this work, an innovative approach was suggested for fast history matching in a real brown field. The workflow was employed based on an optimized proxy model for history matching of a field consisting of 14 active wells with multiple responses (which are production rate and pressure data) in the south part of Iran. The main important features of the proposed algorithm were defining a proxy model which is response surface method in which 21 model parameters were incorporated based on cubic centered face method. The proxy model was then optimized by one of the most famous algorithms which is genetic algorithm. Proxy model was successfully performed using 256 samples leading into p- value of 0.531 and R 2 of 0.91 dataset. As a result, the proposed workflow and algorithm showed good and acceptable results for history matching of studied real model. 相似文献
23.
Marianne Holmer Núria Marbà Morgane Lamote Carlos M. Duarte 《Estuaries and Coasts》2009,32(3):456-466
Species of the macroalgae Caulerpa sp. are increasingly being observed in meadows of the endemic Mediterranean seagrass Posidonia oceanica, and in particular Caulerpa taxifolia, has been considered as an invasive species leading to seagrass decline. Studies have so far failed to reveal the underlying
mechanisms of the success of the macroalgae, and here, we examine how biogeochemical changes of the environment associated
to indigenous (Caulerpa prolifera) and non-indigenous (Caulerpa racemosa and C. taxifolia) species affect the habitat of P. oceanica. Two of the species (C. prolifera and C. racemosa) affect the sediment biogeochemical conditions by increasing organic matter pools, microbial activity, and sulfide pools
of the sediments, and limited effects were found for C. taxifolia. Biomass of the macroalgae contributed to the extent of impacts, and high sulfide invasion into the seagrasses and regression
of the meadow were pronounced at the location with the highest Caulerpa biomass. This suggests that Caulerpa invasion contributes to seagrass decline probably because Caulerpa thrives better than the seagrasses in the modified environment. 相似文献
24.
Do diatoms in the Swiss Alps reflect the length of ice-cover? 总被引:11,自引:0,他引:11
25.
目的是探讨肺癌改变要注意观察其支气管改变,全面评价病灶部位,大小,形态及浸润范围。方法采用了螺旋CT薄层扫描(SVCT)后,再做增强CT扫描,然后对68例肺癌气管支气管进行分析研究,结果明确指出了68例病人均进行CT检查,其中54例经手术病理,支气管镜或细胞学检查证实,从而明确了螺旋CT是诊断支气管肺癌的重要方法之一,非常有益于临床方案的选择和设计。 相似文献
26.
27.
Yu Guangyuan Zhang Qiangyong Li Fan Cheng Lei Guo Xin 《Geotechnical and Geological Engineering》2021,39(6):4545-4562
Geotechnical and Geological Engineering - A set of splitting cracks often occur in the high side wall of the deep underground hydropower station due to the excavation-induced unloading during the... 相似文献
28.
The SWOT Mission and Its Capabilities for Land Hydrology 总被引:2,自引:0,他引:2
Sylvain Biancamaria Dennis P. Lettenmaier Tamlin M. Pavelsky 《Surveys in Geophysics》2016,37(2):307-337
29.
遂川—热水走滑断裂带特征及其对丰州盆地铀成矿的控制作用 总被引:1,自引:2,他引:1
本文以322矿田为例,对穿越矿田的遂川-热水走滑断裂带的特征及其对铀成矿的控制予以讨论。论述了矿田内铀矿床的形成、分布与遂川-热水走滑断裂带的关系,揭示了丰州拉分盆地的形成与铀成矿的内在联系,认为遂川-热水走滑断裂系是322矿田的主控条件,走滑断裂的脉动性控制了铀成矿的多期多阶段性。最后简要地分析了322矿田的找矿前景和走滑断裂的找矿意义。 相似文献
30.
Anil Misra Lance A. Roberts Steven M. Levorson 《Geotechnical and Geological Engineering》2007,25(1):65-77
Load displacement analysis of drilled shafts can be accomplished by utilizing the “t-z” method, which models soil resistance
along the length and tip of the drilled shaft as a series of springs. For non-linear soil springs, the governing differential
equation that describes the soil-structure interaction may be discretized into a set of algebraic equations based upon finite
difference methods. This system of algebraic equations may be solved to determine the load–displacement behavior of the drilled
shaft when subjected to compression or pullout. By combining the finite difference method with Monte Carlo simulation techniques, a probabilistic load–displacement analysis can be conducted. The probabilistic analysis is advantageous
compared to standard factor of safety design because uncertainties with the shaft–soil interface and tip properties can be
independently quantified. This paper presents a reliability analysis of drilled shaft behavior by combining the finite difference
technique for analyzing non-linear load–displacement behavior with Monte Carlo simulation method. As a result we develop probabilistic relationships for drilled shaft design for both total stress (undrained)
and effective stress (drained) parameters. The results are presented in the form of factor of safety or resistance factors
suitable for serviceability design of drilled shafts. 相似文献