全文获取类型
收费全文 | 85篇 |
免费 | 14篇 |
国内免费 | 24篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 38篇 |
地球物理 | 3篇 |
地质学 | 22篇 |
海洋学 | 9篇 |
天文学 | 7篇 |
综合类 | 15篇 |
自然地理 | 6篇 |
出版年
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 4篇 |
2013年 | 5篇 |
2012年 | 6篇 |
2011年 | 9篇 |
2010年 | 10篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 9篇 |
2006年 | 13篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
排序方式: 共有123条查询结果,搜索用时 15 毫秒
91.
Commercial afforestation in South Africa dates back to the 1870s and started as an alternative to the fast disappearing indigenous
timber resource. It involves the planting of exotic timber species and has impacts on water resources, soil biodiversity,
landscapes, etc. Commercial afforestation of land has been subjected to regulation through the Afforestation Permit System
(APS) since 1972, primarily to protect the national water resource. Since the APS no longer adequately dealt with afforestation
regulation, it was replaced in 1999 with a procedure that was supposed to integrate the requirements of relevant legislation
and general environmental management principles. This paper is a theoretical review of the background and development of the new South African Streamflow Reduction Activities licensing procedure, as well as
whether it complies with the requirements of an environmental management system such as ISO 14001. The main conclusion is
that the new procedure, although an improvement on the previous procedure, still has shortcomings especially with regard to
the operational and decommissioning phases of forestry in South Africa. It is recommended that these aspects be addressed
in order to mitigate the impact of forestry on water sustainability in South Africa.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
92.
Kok-Kwang Phoon 《Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards》2017,11(1):4-21
ABSTRACTThis paper adds to the ongoing discussion on the role of reliability calculations in geotechnical design. It situates design calculations, be it verified by a global factor of safety, partial factors, or reliability-based design (RBD), in a larger context of quality management over the life cycle of the structure. It clarifies that uncertainties amenable to probabilistic treatment typically fall under the category of “known unknowns” where some measured data and/or past experience exist for limited site-specific data to be supplemented by both objective regional data and subjective judgement derived from comparable sites elsewhere. Within this category, reliability is very useful in handling complex real-world information (multivariate correlated data) and information imperfections (scarcity of information or incomplete information). It is also very useful in handling real-world design aspects such as spatial variability that cannot be easily treated using deterministic means. Examples are presented to illustrate how reliability calculations could relieve engineering judgement from the unsuitable task of performance verification in the presence of uncertainties so that the engineer can focus on setting up the right lines of scientific investigation, selecting the appropriate models and parameters for calculations, and verifying the reasonableness of the results. 相似文献
93.
本文阐述了国家海洋局海洋技术研究所在ISO9001质量体系认证工作中的做法和经验。 相似文献
94.
We describe how the ISO-SWS (Infrared Space Observatory – Short Wavelength Spectrometer) software packages detect various glitch events i.e. high energy particle hits effecting the SWS detectors. A rough classification of glitch types is given. The events cause an instantaneous change in the slope of the SWS detector read outs followed by a distortion of the further samples, so called glitch tails. As a consequence the S/N ratio and photometric accuracy are reduced.Different strategies, how to remove the resulting distortion of the detectorread-out-ramp after a hit, are presented. The methods of the basic SWS software packages, the Pipeline and Interactive Analysis, will be discussed. The Pipeline has to treat glitch effects automatically. The Interactive Analysis system provides the user with a comfortable Graphical User Interface (GUI) for Trend Analysis, detailed analysis of certain glitches and the testing of new algorithms. 相似文献
95.
渔用高强度聚乙烯和普通聚乙烯绞捻网片的拉伸力学性能比较研究 总被引:6,自引:0,他引:6
为给深水网箱设计与渔用材料的合理选配提供依据,应用ISO1806等对渔用高强度聚乙烯绞捻网片(以下简称HSPE绞捻网片)和普通聚乙烯绞捻网片(以下简称PE绞捻网片)的拉伸力学性能进行了比较研究。结果表明,(1)在同等条件下,36股HSPE绞捻网片的网目连接点断裂强力和网片单线断裂强力分别比52股PE绞捻网片增加了3.1%,3.7%;而前者的目脚直径和网片阻力可较后者减少19.6%。(2)对网片强力进行了再现性研究,36股HSPE和52股PE绞捻网片网目连接点断裂强力的标准偏差分别为35.93N,25.61N,再现性标准偏差分别为31.07N,36.93N;网片单线断裂强力的标准偏差分别为19.91N,13.49N,再现性标准偏差分别为20.48N,15.49N;网片强力测试数据的变异系数均小于4%;表示测试结果的分散性较小。(3)36股HSPE绞捻网片成本可较52股PE绞捻网片减少38.9%,其在渔业生产中进行推广应用具有可行性。(4)GB/T4925作为一个标准,对绞捻网片来说,存在不足,建议对GB/T4925进行修订。 相似文献
96.
97.
在分析地学数据特点和共享需求的基础上,阐述数据分类对于人们认识地球以及地学研究的重要性,并综述和评价了目前地学领域已有的各种分类研究。这些分类研究大致可归纳为探索型、应用型和综合型3种。由于地学数据应用的多学科交叉、多源异构等特性,分类系统很难满足系统性、一致性、易扩展性等原则。本文从数据发生的角度,探索新的数据分类方案,将地学数据分为器测数据、调查数据和过程数据三大类。从数据本质特征对其进行描述,学科应用仅作为数据的元数据对其标志,从而很好地消除了上述问题。此外,本文基于ISO19115地理信息核心元数据扩展模型,将地理信息元数据标准拓展到整个地学领域的数据描述,构建适应该地学数据分类方案的元数据体系。 相似文献
98.
观测资料的分析极为清楚地表明,江淮流域的夏季降水有着极为明显的低频变化,周期为30-60d和近20d的振荡是其最基本的特征,尤其是在多雨的年份.对应江淮夏季多雨(涝)年和少雨(旱)年,大气环流的分析表明其大气季节内振荡(IS0)的形势有着显著的差异.例如在多雨(少雨)年,在长江以南的850hPa上为一个低频(IS0)反气旋(气旋)性环流控制,而中国北部和日本一带为气旋(反气旋)性环流,从而在江淮流域形成较强的低频辐合(辐散)气流;在200hPa的青藏高原上却为一个低频气旋(反气旋)性环流所控制.分析还表明,对应多雨年,在江淮流域有明显的由中高讳度向南传播和由低玮度向北传播的大气低频振荡的汇合情况;而对应于少雨年,由中高纬度向南传播的低频系统较不明显,在江淮流域低频系统的汇合也较为不清楚. 相似文献
99.
ISO9000系列标准是国际公认的质量管理和质量保证统一标准,具有科学性、有效性、通用性的特点。贯彻ISO9000系列标准,是深化和发展单位管理规范、建立和完善质量体系的需要。通过贯标取得认证,可以提高测绘单位的知名度,取得用户的信任,在市场竞争中立于不败之地。 相似文献
100.