全文获取类型
收费全文 | 2921篇 |
免费 | 131篇 |
国内免费 | 224篇 |
专业分类
测绘学 | 78篇 |
大气科学 | 55篇 |
地球物理 | 98篇 |
地质学 | 799篇 |
海洋学 | 135篇 |
综合类 | 106篇 |
自然地理 | 2005篇 |
出版年
2024年 | 1篇 |
2023年 | 29篇 |
2022年 | 126篇 |
2021年 | 112篇 |
2020年 | 116篇 |
2019年 | 111篇 |
2018年 | 79篇 |
2017年 | 95篇 |
2016年 | 136篇 |
2015年 | 102篇 |
2014年 | 132篇 |
2013年 | 133篇 |
2012年 | 173篇 |
2011年 | 184篇 |
2010年 | 120篇 |
2009年 | 171篇 |
2008年 | 177篇 |
2007年 | 160篇 |
2006年 | 177篇 |
2005年 | 150篇 |
2004年 | 137篇 |
2003年 | 109篇 |
2002年 | 100篇 |
2001年 | 80篇 |
2000年 | 89篇 |
1999年 | 85篇 |
1998年 | 53篇 |
1997年 | 40篇 |
1996年 | 19篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 9篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有3276条查询结果,搜索用时 828 毫秒
1.
在改进计划行为理论(TPB)模型基础上,引入人口特征和游艇文化变量,构建游艇旅游行为意向的影响机制模型,以实地调研和问卷调查作为数据来源,运用结构方程模型(SEM)实证检验影响旅游者参与游艇旅游行为意向的主要因素及其作用机制。研究表明:当前我国旅游者参与游艇旅游的意向较高;旅游者的行为态度、主观规范、感知行为控制和游艇文化是影响其选择游艇旅游活动的重要因素;旅游者的行为态度、游艇文化2个变量对游艇旅游行为意向具有显著的正向影响;主观规范和感知行为控制均通过行为态度这一中介变量间接影响游艇旅游行为意向。 相似文献
2.
以全球最大的邮轮点评网站——邮轮评论家为数据来源渠道,以编辑(Editor/Expert)的文本点评以及对167艘邮轮10大属性的打分数据为样本,利用词频分析、回归分析、聚类分析和方差分析等方法,对全球21个邮轮品牌的产品属性、总体评价以及品牌定位问题进行了系统研究。结果表明,对于专业型游客来说,餐饮、客房和娱乐是关注度最高的船上属性,服务、性价比和公共空间是满意度最高的船上属性,客房、餐饮、公共空间、性价比和娱乐属性对邮轮总评具有显著影响。方差分析表明,与行业界定下的品牌行为相比,基于专业型游客感知的品牌划分更有效。 相似文献
3.
日常生活环境和旅游目的地环境都可以为个体提供恢复的机会,不同环境的属性特征导致不同程度的恢复。为了探究环境类型与恢复性效应之间的关系及停留时间的调节作用,文章采用问卷调查方式,利用配对样本t检验和混合设计方差分析相结合的方法,探讨游客在不同环境中的恢复性效应,并对这一现象提供心理上的解释。结果表明:1)恢复体验的4个维度(放松体验、心理脱离、掌握体验、控制体验)在旅游目的地环境中的得分均高于日常生活环境。2)掌握和控制体验维度在城市旅游目的地中的变化程度高于乡村旅游目的地,两种类型目的地的放松和心理脱离维度差异较小。3)随着在目的地停留时间的延长,乡村旅游目的地放松体验和心理脱离维度变化程度高于城市旅游目的地,两种类型目的地环境恢复性效应会相互靠近。因此,游客的环境恢复性效应不仅受到环境和目的地类型的影响,同时还与游客的适应程度有关,且受到其停留时间的调节作用。 相似文献
4.
王发君 《中国海洋湖沼学报》1992,10(1):84-91
Based on a puff model . and together with the consideration of convection , dispersion and descent of suspended waste particles in marine environment , a numerical model is presented to predict the initial sedimentation of waste particles discharged from ocean outfalls in coastal waters and to compute the stable sedimentation rate in homogeneous trde current fields with water depth constant . When the time step selected is small enough , the results from this model agree well with that from the semi-analytical solution , and have sufficient precision for evaluating the impact on the environment caused by sedimentation of waste particles discharged from ocean outfalls. A numerical example is given for predicting the sedimentation of waste particles discharged in Heishijiao , Dalian . 相似文献
5.
6.
张和庆 《广东海洋大学学报》2003,23(5):15-23
介绍了我国海洋倾废的历史、发展过程和管理现状 ,分析了海洋倾倒的现状和面临的困难。文章还提出通过高新技术把疏浚泥迅速转化为再生资源进行利用和污染土无害化处理技术 ,从根本上减少疏浚泥海洋倾倒的数量和缓减海洋倾倒区紧张的状况 ,减少对海洋环境的污染 相似文献
7.
DharmalingamVENUGOPAL 《山地科学学报》2004,1(1):74-80
The Nilgiri Mountains of south India is considered unique by anthropologists, geologists, climatologists, botanists as well as tourists. It has remained a subject of constant study and research over the last two centuries. Man-nature balance had continued undisturbed in the Nilgiris for thousands of years until the early 19th century when it became a British colony attracting, in due course, various developmental activities. Subsequently, the Nilgiris and its popular hill stations emerged as favourite places for the British population in India for rest and recuperation, game and for raising commercial plantations. In the process, the traditional indigenous crops were replaced by “English“ vegetables and the natural forests gave way to commercial plantations of coffee, tea and other exotic species of trees. 相似文献
8.
This work deals with disposal of slurries generated during the cutting and polishing processes of slabs of decorative sedimentary
carbonate rocks in the north western Sicily. At present, they are used as fillers of dismantled quarries near the sawmills
and, as a final step of reclamation, are covered with earth layers. In spite of such inexpensive solution, there is lack of
knowledge about the composition of the waste. In order to assess if there is any threat for the environment and to suggest
indications for alternative solutions, such as recycling or inactivation processes, the slurries were analysed by XR diffraction,
simultaneous thermal analysis, ICP/MS, ionic chromatography, FTIR, UV-Vis, COD and TOC measurements, grain size analysis.
Results indicate that the slurries can threaten the groundwater, because of the high chemical oxygen demand; furthermore they
can modify the mechanism of groundwater recharge, because of their grain size distribution. Some laboratory tests show that,
even in very aggressive conditions, the solid pollutants persist in the waste and slowly release into water the products of
their degradation. The slurry therefore should be subjected to inactivation treatment before disposal or, alternatively, recycled
as secondary raw material for a suitable process. 相似文献
9.
Helmut Kerndorff Stephan Kühn Thomas Minden Dagmar Orlikowski Thomas Struppe 《Environmental Geology》2008,55(2):291-301
The aim of this research project is to identify, characterize and quantify natural attenuation (NA) processes in groundwater
affected by emissions of abandoned waste disposal sites in Berlin-Kladow/Gatow, Germany. It is part of the funding priority
called KORA established by the Federal Ministry for Education and Research (BMBF) to explore the extent to which NA can be
used for remedial purposes for varied forms of soil and groundwater contamination. Information on the emission behaviour of
individual parameters is generated on the basis of hydrogeochemical comparison of 20 years old and new data. Using groundwater-modelling
and CFC-analysis, information on the transport and retention of pollutants in groundwater is compiled. The microbial colonization
of contaminated aquifers is characterized by molecular biological methods [polymerase chain reaction (PCR) and denaturing
gradient gel electrophoresis (DGGE)] to differentiate between contaminated and not contaminated zones. 相似文献
10.
Shear strength characterization of municipal solid waste at the Suzhou landfill, China 总被引:5,自引:0,他引:5
The current practice of slope stability analysis for a municipal solid waste (MSW) landfill usually overlooks the dependence of waste properties on the fill age or embedment depth. Changes in shear strength of MSW as a function of fill age were investigated by performing field and laboratory studies on the Suzhou landfill in China. The field study included sampling from five boreholes advanced to the bottom of the landfill, cone penetration tests and monitoring of pore fluid pressures. Twenty-six borehole samples representative of different fill ages (0 to 13 years) were used to perform drained triaxial compression tests. The field and laboratory study showed that the waste body in the landfill can be sub-divided into several strata corresponding to different ranges of fill age. Each of the waste strata has individual composition and shear strength characteristics. The triaxial test results showed that the MSW samples exhibited a strain-hardening and contractive behavior. As the fill age of the waste increased from 1.7 years to 11 years, the cohesion mobilized at a strain level of 10% was found to decrease from 23.3 kPa to 0 kPa, and the mobilized friction angle at the same strain level increasing from 9.9° to 26°. For a confinement stress level greater than 50 kPa, the shear strength of the recently-placed MSW seemed to be lower than that of the older MSW. This behavior was consistent with the cone penetration test results. The field measurement of pore pressures revealed a perched leachate mound above an intermediate cover of soils and a substantial leachate mound near the bottom of the landfill. The measurements of shear strength properties and pore pressures were utilized to assess the slope stability of the Suzhou landfill. 相似文献