首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   30篇
  免费   0篇
  国内免费   2篇
测绘学   6篇
大气科学   10篇
地球物理   13篇
地质学   1篇
海洋学   1篇
自然地理   1篇
  2017年   1篇
  2014年   1篇
  2013年   1篇
  2011年   2篇
  2008年   1篇
  2007年   2篇
  2006年   1篇
  2004年   2篇
  2002年   1篇
  1996年   1篇
  1994年   1篇
  1991年   1篇
  1986年   1篇
  1980年   1篇
  1978年   3篇
  1977年   1篇
  1974年   1篇
  1968年   1篇
  1967年   1篇
  1964年   1篇
  1961年   1篇
  1960年   1篇
  1959年   2篇
  1958年   1篇
  1957年   1篇
  1954年   1篇
排序方式: 共有32条查询结果,搜索用时 15 毫秒
11.
The chemical and biological characteristics of surface waters in Jinhae Bay were investigated over four seasons to understand water quality in light of the growing industrialisation occurring within this area. Jinhae Bay includes four smaller bays: Masan; Hangam; Jindong; and Gohyun. The water quality in Jinhae Bay varied spatially and seasonally. The water quality of both Hangam Bay and Masan Bay was highly degraded, demonstrating high concentrations of ammonia, nitrate, chlorophyll a and particulate organic carbon. Contamination from sewage was the dominant cause of the water quality deterioration in these bays. Conversely, the water quality in Jindong Bay and Gohyun Bay was not as severely affected as that of the above two bays. Water quality in Jinhae Bay was particularly poor in summer when nutrient loading was highest due to the run-off associated with high precipitation. Principal component analysis indicated that nitrogen contamination was a major factor influencing the water quality of Jinhae Bay. The effective reduction in high-nitrogen discharges is essential to improve water quality in Jinghae Bay.  相似文献   
12.
13.
Temperature is critical to maintaining seed viability under long-term storage conditions. It has been common practice to use refrigeration systems to maintain required storage temperatures. A seed repository constructed in permafrost in Yakutsk, Russia is the first seed storage facility that relies solely on natural cold. This paper describes the design and performance of the cooling system of the repository. An innovative aspect of the cooling system is that it utilizes the patterns of temperature wave propagation in permafrost. Predicted and measured ground temperatures for the first year of operation are presented and analyzed. Results indicate that convection air cooling systems can be used to control the temperature regime in underground facilities in permafrost.  相似文献   
14.
PIXE is a well established and valuable method for quantitative and qualitative aerosol elemental analysis. Using this method, we have developed a technique to simultaneously analyse the trace-element content in precipitation for elements with Z> 12. Freeze-drying and leaching was used as a nonselective preconcentration technique. A special backing foil to take up the sample liquid to be dried was developed for these experiments. By careful adjustment of the experimental parameters, we reached a detection limit lower than 1 ppb for most detected elements. Thus, it will be possible to analyze precipitation at low concentrations of trace elements which are important for air chemistry and environmental studies.Supported by DFG/Bonn under Sonderforschungsbereich 233.  相似文献   
15.
Zusammenfassung Die vorliegende Arbeit behandelt Gefrierkernmessungen, die im Rahmen eines europäischen Gemeinschaftsprogrammes auf dem Kleinen Feldberg/Taunus vorgenommen wurden. Ein Ziel dieser Arbeiten war die Aufdeckung und Deutung sommerlicher Anomalien der Gefrierkernkonzentration. Die Ergebnisse zeigen, daß während des Sommers 1964 aufgetretene Anomalien im wesentlichen regionalen Einflüssen zugeschrieben werden können. Ein Zusammenhang mit den an verschiedenen in Frankreich, Italien, Österreich und Spanien unterhaltenen Meßstellen gleichzeitig gewonnenen Ergebnissen ist nicht nachweisbar.
Summary This paper deals with measurements of the concentration of atmospheric freezingnuclei carried out in the frame of an European cooperative program. The investigations described here were made on Mt. Kleiner Feldberg/Taunus. They aimed at detecting and explaining anomalies of the freezing-nucleus concentration generally occurring during the summer-months. The results show that the anomalies observed on Mr. Kleiner Feldberg during summer 1964 are mainly caused by regional phenomena. There exists hardly any connection to results gained at the same time at sites of measurement in France, Italy, Austria and Spain.
  相似文献   
16.
17.
A three-stage vertical-flow thermal gradient vapour diffusion chamber for the fast, continuous measurement of the number concentration of cloud condensation nuclei (CCN) at three different water vapour supersaturations was constructed. CCN are monitored by imaging cloud droplets in the chamber with a CCD-camera. The counting of droplets and the control of all instrumental parameters are computerized. The instrument was calibrated with NaCl-aerosols, and was successfully operated in the field. Data from 2 weeks of field measurements at an island in the North Sea are presented.  相似文献   
18.
The dominant model of journal evaluation emerged at the time when there were no open-access journals, and nobody has assessed yet whether this model is able to cope with this modern reality. This commentary attempts to fill the gaps in the common understanding of the role that 'impact factor' should play in evaluation of open-access journals.  相似文献   
19.
The 50-year global CO2 record led the way in establishing a scientific fact: modern civilization is changing important properties of the global atmosphere, oceans and biosphere. The evidence on which this scientific fact is based will be refined further, but the next challenge for scientists is broader. In addition to its traditional role in providing discovery, diagnosis, and prediction of the changes that are taking place on our planet, science has now also a role in helping society mitigate emissions by objectively quantifying them, and in helping adaptation by providing environmental forecasts on regional scales. Science is also expected to provide new options for society to tackle the transition to a new energy system, and to provide thorough environmental evaluation of all such options. This is what the meeting recognized as planetary responsibilities for scientists in the next 50 years.  相似文献   
20.
Zusammenfassung Es wird über parallele Untersuchungen der atmosphärischen Gefrierkerne und der Kondensationskerne berichtet, die an drei klimatisch verschidenen Meßorten — Frankfurt/M, Taunus Observatorium und Zugspitze — bei unterschiedlichen Witterungsbedingungen vorgenommen wurden. Im Verlauf der Untersuchungen zeigte sich eine starke Abhängigkeit der Aktivierungstemperatur der Gefrierkerne von der Teilchengröße der Kondensationskerne, die mit verschiedenen Methoden nachgewiesen werden konnte.
Summary Parallel measurements of freezing nuclei and condensation nuclei were carried out at three different locations — Frankfurt/M, Taunus observatory and Zugspitze — under various weather conditions. During these investigations a strong relation between the activation-temperature of freezing nuclei and the particle size of the condensation nuclei was detected and confirmed with different methods.
  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号