全文获取类型
收费全文 | 2574篇 |
免费 | 384篇 |
国内免费 | 340篇 |
专业分类
测绘学 | 304篇 |
大气科学 | 298篇 |
地球物理 | 747篇 |
地质学 | 864篇 |
海洋学 | 279篇 |
天文学 | 13篇 |
综合类 | 245篇 |
自然地理 | 548篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 91篇 |
2021年 | 82篇 |
2020年 | 95篇 |
2019年 | 103篇 |
2018年 | 78篇 |
2017年 | 104篇 |
2016年 | 126篇 |
2015年 | 109篇 |
2014年 | 132篇 |
2013年 | 157篇 |
2012年 | 159篇 |
2011年 | 158篇 |
2010年 | 135篇 |
2009年 | 133篇 |
2008年 | 149篇 |
2007年 | 162篇 |
2006年 | 138篇 |
2005年 | 124篇 |
2004年 | 122篇 |
2003年 | 120篇 |
2002年 | 109篇 |
2001年 | 69篇 |
2000年 | 79篇 |
1999年 | 73篇 |
1998年 | 63篇 |
1997年 | 73篇 |
1996年 | 62篇 |
1995年 | 32篇 |
1994年 | 53篇 |
1993年 | 50篇 |
1992年 | 33篇 |
1991年 | 39篇 |
1990年 | 23篇 |
1989年 | 11篇 |
1988年 | 14篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1984年 | 3篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有3298条查询结果,搜索用时 15 毫秒
71.
With the enhanced warming and acidification of global ocean, whether and to what extent the naturally-weathered fluvial sediment into the sea can release elements and thus influence the geochemical pro... 相似文献
72.
《Marine Policy》2015
While the economic and environmental benefits of fisheries management are well accepted, the costs of effective management in low value fisheries, including the research necessary to underpin such management, may be considerable relative to the total economic benefits they may generate. Co-management is often seen as a panacea in low value fisheries. Increasing fisher participation increases legitimacy of management decision in the absence of detailed scientific input. However, where only a small number of operators exist, the potential benefits of co-management are negated by the high transaction cost to the individual fishers engaging in the management process. From an economic perspective, sole ownership has been identified as the management structure which can best achieve biological and economic sustainability. Moving low value fisheries with a small number of participants to a corporate-cooperative management model may come close to achieving these sole ownership benefits, with lower transaction costs. In this paper we look at the applicability of different management models with industry involvement to low value fisheries with a small number of participants. We provide an illustration as to how a fishery could be transitioned to a corporate-cooperative management model that captures the key benefits of sole management at a low cost and is consistent with societal objectives. 相似文献
73.
《Marine Policy》2015
Maritime safety has become a major concern in Korea. As an alternative to improve maritime safety, the Korean government is considering enhancing infrastructure associated with maritime safety, in the form of a vessel traffic service (VTS) facility for high density waterways. This study estimates the public value of a VTS facility construction project using the contingent valuation (CV) method. A CV survey using person-to-person interviews was administered to 400 randomly selected households to elicit their willingness to pay (WTP) for the project. Overall, the respondents accepted the contingent market, and on average, Korean households were willing to pay a significant amount toward the project. The mean WTP for the project is estimated to be approximately KRW 4149.5 (USD 3.7) per year per household, which is statistically significant. The estimate of the fiduciary benefit to Korean households is approximately KRW 11.07 billion (USD 9.91 million) per year for five years. The results are expected to be useful for policy-makers in determining the economic feasibility of a VTS. 相似文献
74.
本文依据Google Earth近2年的遥感影像以及2013年的资源3号卫星影像数据,并结合他人前期研究资料,对山东省滨海湿地的分布和类型进行了研究,使用ArcGIS软件测算出滨海湿地总面积约为5 124km2,其中自然湿地占35.23%,人工湿地占64.77%。根据山东省湿地实际状况,以及湿地的地理位置、成因、水文、生物等要素的差异,将山东省滨海湿地划分为十种类型,并在此基础上,针对滨海湿地不同的生态服务功能类型,采取了不同的方法进行初步价值评估。结果表明,山东省滨海湿地生态服务总价值约3 303亿元,约占山东省2013年GDP的6.04%。其中物质生产价值约占总价值的50.70%,其次为环境调节价值,约占48.24%,社会服务价值只占1.06%。这表明,山东省滨海湿地蕴含较高的经济和生态潜力,能带来较高的经济效益和生态效益,但是社会服务功能价值量相对偏低,有待于进一步重视和开发。 相似文献
75.
76.
使用数学形态学的"膨胀算子"对影像进行预处理,提出了一种改进的基于高斯拉普拉斯算子的面状特征提取和细化方法,并利用边界代数快速标注边界封闭的面状特征。在提取面状特征的基础上,利用奇异值分解算法,实现了基于面状质心的遥感影像匹配,进而完成精确配准。实验结果表明,与传统方法相比,此方法在速度与准确度上具有明显优势。 相似文献
77.
房地产计税价格批量评估实证研究 总被引:3,自引:0,他引:3
结合批量评估的技术思路,以深圳市二手住宅计税价格批量评估为例,构建了以长期趋势法,成本法为基本原理,结合地理信息技术(GIS)的批量评估模型,并提出研究结论与未来发展设想. 相似文献
78.
An empirical atmospheric model(EAM) based on the singular value decomposition(SVD) method is evaluated using the composite El Ni(?)o/Southern Oscillation(ENSO) patterns of sea surface temperature (SST) and wind anomalies as the target scenario.Two versions of the SVD-based EAM were presented for comparisons.The first version estimates the wind anomalies in response to SST variations based on modes that were calculated from a pair of global wind and SST fields(i.e.,conventional EAM or CEAM).The second version utilizes the same model design but is based on modes that were calculated in a region-wise manner by separating the tropical domain from the remaining extratropical regions(i.e.,region-wise EAM or REAM). Our study shows that,while CEAM has shown successful model performance over some tropical areas, such as the equatorial eastern Pacific(EEP),the western North Pacific(WNP),and the tropical Indian Ocean(TIO),its performance over the North Pacific(NP) seems poor.When REAM is used to estimate the wind anomalies instead of CEAM,a marked improvement over NP readily emerges.Analyses of coupled modes indicate that such an improvement can be attributed to a much stronger coupled variability captured by the first region-wise SVD mode at higher latitudes compared with that captured by the conventional one. The newly proposed way of constructing the EAM(i.e.,REAM) can be very useful in the coupled studies because it gives the model a wider application beyond the commonly accepted tropical domain. 相似文献
79.
根据最新地质考察和历史地震考证结果,西秦岭北缘断裂带从东到西可划分为宝鸡、天水、武山、漳县、黄香沟和锅麻滩共6个次级断裂段。上述断裂既具有单段破裂,又具有多段组合破裂的特征。利用时间相依的地震潜势概率评估方法,对这6个单段分别进行地震危险性概率评估,其中黄香沟段和漳县段发生单段破裂的可能性最大,天水段发生单段破裂的概率次之。若发生组合破裂,黄香沟段和漳县段组合破裂可能性大。同时,根据沿断裂带的b值扫描图像分析结果显示,黄香沟段和天水附近应力积累较高,这两个地区应是未来发生强震的主要段落,值得关注。 相似文献
80.
平武地震台数字地震仪记录近震震级及定位偏差 总被引:2,自引:0,他引:2
以《四川省地震台网地震目录》作为地震定位参考标准,对平武地震台数字地震仪记录的近震,尤其是汶川"5·12"地震序列定位参数进行了对比。结果表明,平武单台数字地震仪记录得到的测定结果与《四川省地震台网地震目录》间存在一定程度的差异。这里给出了台站可以简单应用的偏差评估值和处理方法。 相似文献