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   40篇
  免费   4篇
  国内免费   32篇
测绘学   1篇
大气科学   6篇
地球物理   12篇
地质学   14篇
海洋学   20篇
天文学   8篇
综合类   2篇
自然地理   13篇
  2024年   3篇
  2023年   7篇
  2022年   6篇
  2021年   3篇
  2020年   2篇
  2019年   2篇
  2017年   1篇
  2014年   1篇
  2013年   2篇
  2012年   4篇
  2011年   1篇
  2010年   2篇
  2009年   1篇
  2007年   2篇
  2006年   2篇
  2005年   1篇
  2003年   2篇
  2001年   3篇
  2000年   5篇
  1999年   5篇
  1998年   1篇
  1997年   2篇
  1995年   3篇
  1994年   6篇
  1993年   1篇
  1992年   1篇
  1990年   1篇
  1986年   1篇
  1964年   1篇
  1957年   1篇
  1956年   1篇
  1955年   1篇
  1954年   1篇
排序方式: 共有76条查询结果,搜索用时 121 毫秒
21.
Abstract-The test organisms (Paralichthys olivaceus) were exposed to CB-28 with differentspiked concentrations. After 72 h, EROD activities in livers of the test organisms were measured. It wasfound that EROD activities significantly mounted up with the increase of spiked quantity. Therefore,there existed a dose-response relationship between EROD activities and specific pollutant concentrations.In the meantime, the optimal conditions for the analysis of EROD activity were discussed. The limita-tion of EROD activities as a monitoring parameter was also analyzed.  相似文献   
22.
Formal change is made of the correlation coefficient(COCOEF) expression,leading to a new formula consisting of Fourier spectral coefficients that indicates a direct connection between the new form and atmospheric dynamic equations,thus resulting in a dynamic equation represented by COCOEF,which is meaningful in exploring a large-scale dynamic process in terms of the correlation field because the connection revealed by the field can have dynamic explanation with the aid of the new formula.  相似文献   
23.
I.Intr0ducti0nAwnerresource-environmentalsystem,withmanyquantitativeandqualitativefactors,consistsofwaterresourcesdevelopmentandenvironment.Itisveryddriculttocarryoutoverallassessmentsanddecision-maldngstudiesofthesystemusingapurelyquantitativen1athematical-l11odel.However,AnalyticalHicerarcl1yProcess(AHP,anewmethodfOrtheplanninganddecisioll-making,combiningqualitativefactorswithquantitativefactors,cansolvethedecision-mdengpr0blemsOfmultiplehierarchiesandgOalsforacomplexsystem.Thismeth0d,t…  相似文献   
24.
The vertically averaged temperature (TAV) from surface to 100 m depth of the South China Sea for the period 1959-1988 is analyzed. The results indicate that there is a significant long-term variability from interannual to interdecadal scales in the heat content in the upper ocean. The heat content of the upper ocean of the South China Sea increases evidently in the El Nino year. TAV anomaly in the ocean was negative from the end of 1950’s to early l970’s, and then changed to positive. The changes of TAV of the ocean are closely related to ENSO events, the Asian winter monsoon and the tropical atmospheric circulation anomalies.  相似文献   
25.
The in situ zircon U-Pb-Lu-Hf isotope records from end-Permian volcanic interlayers in southwest China, integrated with previous studies, restructure the evolutionary history of the Yangtze Craton from Precambrian to Late Paleozoic. This includes early continental crust formation before ~3.0 Ga and massive juvenile crustal growth at 2.6–2.4 Ga; large-scale crustal reworking at ~2.1–1.7 Ga; Neoproterozoic crust addition at ~1.1 to 0.7 Ga; collision and subduction along the craton margin between ~700–541 Ma; Early Ordovician to Late Silurian magmatism; and large tectono-thermal events in the Middle Carboniferous to end-Permian. Some zircons with TMD2 ages from 4.40 to 4.01 Ga and lower initial 176Hf/177Hf values of 0.280592 to 0.280726 may imply the existence of Hadean crust relics beneath the Yangtze Craton and their provenances could be associated with Hadean crustal remelting. This study further clarifies that the Precambrian-age zircons between the end-Permian volcanic interlayers, the complexes in the western margin of the Yangtze Craton, and the sedimentary Kangdian Basin, may share an affinity based on similar U-Pb age spectra and Hf isotope features. It also shows that the Neoproterozoic tectono-thermal event may be associated with large-scale tectono-rifting activity, which is different from the Grenville-age continental collision between Yangtze and Cathaysia blocks in South China. The above findings support the inference of a widespread Archean basement extending to the western Yangtze Craton and a provenance in the Kangdian Basin that is derived from the weathering and erosion of Paleoproterozoic continental crust.  相似文献   
26.
INTRODUCTIONForavarietyofapplications,includingcoastalandoceanengineering,shiproutingandtheinterpretationofremotelysensedata,informationonthedirectionalwavespectrumisdesirable.Knowledegeoftheintegratedorone-dimensionalspectrumisconsiderable,duelargelytofieldmeasurementssuchasJONSWAP.Asimilarsituation,however,doesnotexistinthecaseofdirectionalsprectra.Thisislargelyduetotheaddedcomplexityandthecostofdirectionalmeasure1.InstituteofPhysicalOceanography,OceanUniversityofQingdao,Qingdao266…  相似文献   
27.
<正>China,the world’s leading producer and consumer of mineral resources,faces significant ecological and environmental challenges resulting from the extensive and intensive exploitation of these resources.These challenges include the degradation of the geological environment in mining areas,depletion of land resources,and the decline in ecosystem functions.In 2018,remote sensing monitoring of the mining environment revealed that mining-damaged land (excluding salt lakes) in China accounted...  相似文献   
28.
Ma M  Feng Z  Guan C  Ma Y  Xu H  Li H 《Marine pollution bulletin》2001,42(2):132-136
Current contents of persistent organic contaminants, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and the congeners (naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, chrysene, benzo(a)anthracene, benzo(a)pyrene and benzo(e)pyrene), DDTs and metabolites in the intertidal sediments of the Bohai Sea and the Yellow Sea were studied. The mean levels of DDTs, PAHs and PCBs were 177.52, 877.2 and 3.4 ng g-1 dry weight, respectively. The spatial trends of the contaminant residue levels were analysed too.  相似文献   
29.
The concentrations, compositional profiles, and potential ecological risk of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in sediments of the Daliao River Estuary were investigated. Total concentrations of PCDD/Fs, PCBs, and PCNs were in the range of 11.3-133.2 ng/kg dry weight (dw), 1 971-37 632 ng/kg dw and 33.1-284.4 ng/kg dw, respectively. The total TEQ values varied from 0.37 to 4.08 ng/kg dw, with the dominant contributions by PCDD/Fs, then by PCBs and PCNs. The spatial distributions of PCDD/Fs, PCBs and PCNs in the river estuary were much related to hydrodynamic conditions. The risk of contamination to the deeper sea was increased in the flood seasons. Moreover, our data confirmed that both organic matter in sediments and molecular properties of dioxin-like compounds were the factors which strongly influenced the partition behavior of these dioxin-like compounds between sediments and water phase in the estuarine zone.  相似文献   
30.
This study analyzes the signal quality and the accuracy of BeiDou 3 rd generation Satellite Navigation System(BDS3) Precise Point Positioning(PPP) in the Arctic Ocean. Assessment of signal quality of BDS3 includes signal to noise ratio(SNR), multipath(MP), dilution of precision(DOP), and code-minus-carrier combination(CC). The results show that, 5 to 13 satellites are visible at any time in the Arctic Ocean area as of September 2018, which are sufficient for positioning. In the mid-latitude ocea...  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