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191.
Does ratification matter and do major conventions improve safety and decrease pollution in shipping?
This article develops a method to measure the effect of the major international conventions in the area of safety, pollution, search and rescue and work related measures. It further distinguishes between the effect of entry into force and the status of ratification of a convention by its parties. Standard econometric models are used and the analysis is based on a unique dataset of 30 years of monthly data where the models also correct for other factors which can influence safety such as safety inspections and ship economic cycles. The results show a complex picture where the average time between adoption and entry into force was calculated to be 3.1 years. Overall, the more parties ratify a convention, the more likely safety is improved and pollution is decreased although one can detect a certain level of non-compliance. The immediate effect of entry into force presents a mixed picture where most negative effects can be found with legislation in the area of safety management and pollution, followed by technical areas. The effect of legislation in the areas related to working and living conditions and certification and training is smallest. Seasonality can be found with peaks in December and January for all conventions but are less important for pollution. 相似文献
192.
Y. Bourls M. Alunno-Bruscia S. Pouvreau G. Tollu D. Leguay C. Arnaud P. Goulletquer S.A.L.M. Kooijman 《Journal of Sea Research》2009,62(2-3):62
A bio-energetic model, based on the DEB theory exists for the Pacific oyster Crassostrea gigas. Pouvreau et al. [Pouvreau, S., Bourles, Y., Lefebvre, S., Gangnery, A., Alunno-Bruscia, M., 2006. Application of a dynamic energy budget model to the Pacific oyster, C. gigas, reared under various environmental conditions. J. Sea Res. 56, 156–167.] successfully applied this model to oysters reared in three environments with no tide and low turbidity, using chlorophyll a concentration as food quantifier. However, the robustness of the oyster-DEB model needs to be validated in varying environments where different food quantifiers reflect the food available for oysters, as is the case in estuaries and most coastal ecosystems. We therefore tested the oyster-DEB model on C. gigas reared in an Atlantic coastal pond from January 2006 to January 2007. The model relies on two forcing variables: seawater temperature and food density monitored through various food quantifiers. Based on the high temperature range measured in this oyster pond (3–30 °C), new boundary values of the temperature tolerance range were estimated both for ingestion and respiration rates. Several food quantifiers were then tested to select the most suitable for explaining the observed growth and reproduction of C. gigas reared in an oyster pond. These were: particulate organic matter and carbon, chlorophyll a concentration and phytoplankton enumeration (expressed in cell number per litre or in cumulative cell biovolume). We conclude that when phytoplankton enumeration was used as food quantifier, the new version of oyster-DEB model presented here reproduced the growth and reproduction of C. gigas very accurately. The next step will be to validate the model under contrasting coastal environmental conditions so as to confirm the accuracy of phytoplankton enumeration as a way of representing the available food that sustains oyster growth. 相似文献
193.
Nelson Valdivia Kate L. de la Haye Stuart R. Jenkins Susan A. Kimmance Richard C. Thompson Markus Molis 《Journal of Sea Research》2009,61(4):216-221
The efficiency by which communities capture limiting resources may be related to the number of species or functional types competing therein. This is because species use different resources (i.e. complementarity effect) or because species-rich communities include species with extreme functional traits (positive selection effect). We conducted two manipulative studies to separate the effects of functional richness and functional identity on the feeding efficiency (i.e. filtration rate) of suspension-feeding invertebrates growing on vertical surfaces. In addition, one experiment tested whether the density of organisms influences the effect of functional diversity. Monocultures and complete mixtures of functional types were fed with a solution of microalgae of different sizes (6 μm–40 μm). Experiments conducted at two locations, Helgoland and Plymouth, showed that functional identity had far larger effects on filtration rate than richness. Mixtures did not outperform the average monoculture or the best-performing monoculture and this pattern was independent on density. The high efficiency of one of the functional types in consuming most microalgae could have minimised the resource complementarity. The loss or gain of particular species may therefore have a stronger impact on the functioning of epibenthic communities than richness per se. 相似文献
194.
本文以东北、华北及川滇地区为例,系统研究了余震时空丛集对概率地震危险性分析的影响.采用基于传染型余震序列模型(ETAS)的蒙特卡罗模拟方法,模拟了包含余震和不包含余震的两套地震序列,然后以模拟地震目录为基础输入,采用基于空间光滑地震活动性模型的地震危险性分析方法计算了两套地震危险性结果——PGA(Peak Ground Acceleration,峰值加速度),通过分析比较这两套PGA的绝对差值和相对差值来研究余震时空丛集对概率地震危险性分析的影响.研究结果表明余震对50年超越概率10%地震危险性计算结果的影响均值为6%左右,最大可达10%,并且随着超越概率水平的提高,余震影响也越大.弱地震活动区余震对概率地震危险性分析的影响要高于强地震活动区.研究结果还进一步揭示两套PGA结果绝对差值的最大值约为15 cm·s~(-2),且出现在高PGA区,这意味着余震对概率地震危险性计算结果不会产生显著影响.因此在地震区划或一般性地震危险性分析中可考虑不用删除余震. 相似文献
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196.
章古台固沙造林技术与效益评价 总被引:11,自引:1,他引:10
章古台从1955年开始引种樟子松进行育苗造林试验,至60年代初期引种造林成功后,又于70年代后期在内蒙古敖汉旗扩大引种造林,获得成功。近年樟子松人工林出现了生长减缓现象,主要是由于造林选地不适和经营不善所引起的。樟子松扩大引种造林的技术关键是采取乔灌草型,等宽隔带式造林模式,降水量不低于300~350mm,土壤含水率不低于2.0%~2.5%。土壤类型为生草风沙土、栗钙土型风沙土和黑土型风沙土,pH值为6.8~8.3。造林时间比正常拖后至4月8日~20日之间,2a生苗造林深度以25~35cm为宜,苗木根长以25cm左右为佳,苗木运输前应沾泥浆进行包装。植苗时放在苗木罐中以防根系风干,剔除不合格苗木,造林时铲除干土层或干草皮。对松树幼株进行埋土越冬处理。 相似文献
197.
旱林作业对水分因子再分配研究 总被引:2,自引:0,他引:2
水分因子严重制约着干旱半干旱条件下林木的生长,因地制宜地采用各种造林技术,最大限度地创造集流条件,合理利用水资源,是干旱造林研究的主要课题。根据多年的试验观测与研究,对旱林作业技术措施的实践应用效果,进行了综合评价和分析研究。 相似文献
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