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排序方式: 共有383条查询结果,搜索用时 15 毫秒
61.
浦桑果铜多金属矿床是在南木林火山盆地内新近发现的矽卡岩型铜多金属矿床。文章对矿区内的花岗闪长岩、花岗闪长斑岩和闪长玢岩进行了岩石地球化学研究,结果表明:这些岩石的ω(SiO2)介于59.08%~67.28%,ω(Al2O3)为15.38%~16.86%,ω(MgO)为1.52%~4.06%,ω(TFeO)介于1.2%~3.46%,均属钙碱性系列。稀土元素总量为22.0×10-6~148.56×10-6,LaN/YbN比值为17.98~37.57,为轻稀土元素富集。花岗闪长岩、花岗闪长斑岩和闪长玢岩均相对富集Cs、Rb、Sr等大离子亲石元素(LILE),亏损高场强元素(HFSE)Th、U、Nb等,强负铕异常或弱负铕异常,无铈异常或弱铈异常。岩石学、岩石化学、微量元素研究表明,花岗闪长斑岩和闪长玢岩形成于中生代雅鲁藏布新特提斯洋向北部拉萨地体俯冲的岛弧环境,花岗闪长岩形成于青藏高原碰撞后伸展作用环境。 相似文献
62.
利用动态定位模块Track进行GPS单历元定位研究 总被引:1,自引:0,他引:1
在研究GPS单历元定位方法基础上,利用GAMIT GPS数据处理软件中的动态定位模块Track,分别得到了动船的运动轨迹和2011年3月日本地震发生后4个IGS站的位移量。实验结果表明:Track模块解算动态GPS数据能得到清晰的动船运动轨迹;采用TRACK模块解算地震发生时的GPS观测数据能够得到地震后的位移特征,且能有效探测主震发生时间。 相似文献
63.
Keith F. Blonquist 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):919-926
Bundle adjustment is a method for simultaneously calculating both the interior and exterior orientation parameters of a set of images, and the object-space coordinates of the observed points. In the case of long focal length lenses and narrow field-of-view (FOV) imaging situations, collinearity based (perspective projection) algorithms may result in linear dependencies between parameters that cause solution instability. The use of a scaled orthographic projection model based on linear algebraic formulations was therefore adopted to reduce this risk. Using quaternions, a new mathematical model is derived that includes the partial derivatives as well as the inner constraint equations for a scaled orthographic bundle adjustment. The model was then tested using two image sets of a single, small vessel (about 6 m length) with a cube target of known dimensions at two distinct ranges; perspective solutions were also calculated for comparison. RMS residual errors of 0.74-0.78 pixels associated with the new method compare favorably to a residual error range of 0.59-0.74 pixels using a perspective bundle adjustment of the same target points. Relative precisions (as a ratio of target size) of between 1:1650 and 1:750 have been achieved at ranges of 375 m and 850 m, respectively, given comparisons with the known cube dimensions. A third image dataset consisting of a network of 16 images was solved with a 1:2200 relative precision showing the new method can successfully handle high redundancy. For the experiments that were conducted, the new method was found to produce less precise results than the perspective bundle solution for a FOV of 0.50-0.65° where the object fills 5-8% of the image. However, it was found to match the precision of the perspective model (with an uncalibrated camera) for a FOV of 0.20-0.30° where the object of interest fills only 1-2% of the full image. 相似文献
64.
三峡梯级枢纽多目标生态优化调度模型及其求解方法 总被引:2,自引:0,他引:2
针对三峡梯级枢纽综合效益的充分发挥及其对长江流域典型生态系统修复及持续改善的科学需求,通过分析发电效益与生态效益之间的制约竞争关系,以发电量最大和生态缺水量最小为目标建立了梯级电站多目标生态优化调度模型,对三峡梯级枢纽多目标生态优化调度进行了研究。同时,针对传统优化方法难以同时处理多个调度目标的固有缺陷,提出一种改进多目标差分进化算法对所构建模型进行高效求解。该方法针对差分进化算法在多目标协同优化和全局寻优能力等方面的不足,依据问题的特点重新设计了差分进化算法的进化算子,同时设计了一种多目标混沌搜索策略以加强算法的局部搜索能力。最后,依据多目标生态优化调度问题的特点设计了一种不需要设置惩罚因子的约束处理方法。通过三峡梯级枢纽多目标生态优化调度的实例应用,验证了本文所构建模型的合理性以及所提出算法的有效性和工程实用性。 相似文献
65.
Islands are often considered to be a priority for conservation, because of their relatively high levels of biodiversity and their vulnerability to a range of natural and anthropogenic threats. However, the capacity of islands to conserve and manage biodiversity may depend upon their governance structures. Many island states are affiliated to other countries through an ‘overseas territory’ status, which may provide them with access to resources and support mechanisms, but which may also influence the capacity for local-scale management of environmental issues. The United Kingdom has 12 island Overseas Territories (UKOTs), most of which support biodiversity of high conservation concern. This study investigates perceptions of current and future threats to marine ecosystems and constraints to environmental protection on the six Caribbean UKOTs, through semi-structured interviews with officials from UK and UKOT government departments and non-governmental organisations. Coastal development, pollution and over-fishing were perceived as threats of most concern for the next decade, but climate change was perceived as by far the greatest future threat to the islands' marine ecosystems. However, a series of common institutional limitations that currently constrain mitigation and conservation efforts were also identified, including insufficient personnel and financial support, a lack of long-term, sustainable projects for persistent environmental problems and inadequate environmental legislation. These findings highlight the need for regional cooperation and capacity-building throughout the Caribbean and a more concerted approach to an UKOT environmental management by the UK and UKOTs' governments. 相似文献
66.
附有条件的参数平差模型的有偏估计 总被引:1,自引:0,他引:1
讨论附有条件的参数平差模型参数的有偏估计问题。提出了约束岭估计和约束主成分估计,并证明了它们的优良性质,最后给出了一个算例,验证了所得结果。 相似文献
67.
68.
Rodolfo Console Rita Di Giovambattista Aldo Di Sanza Paolo Favali Giuseppe Smriglio 《Geophysical Journal International》2000,143(1):129-141
In this paper we show how the performance of the joint hypocentre determination (JHD) method can be improved, leading to reduced instability in cases close to singularity. The method has been extended by imposing a number of constraints introduced by other authors, and adding a new one. We tested the stability of the method and the relative advantages of the various constraints by simulating a geometrical space distribution of hypocentres recorded by a regional seismic network. We then applied this method to deep earthquakes that occurred in the Southern Tyrrhenian Sea subduction zone and to the seismicity of the Northern Apennines, which is moderately deeper than the typical shallow seismicity of the Apennines. The results obtained from the analysis of synthetic data and actual earthquakes confirm that the JHD method produces less scatter in the hypocentral determinations with respect to the standard locations. The main conclusion of our study is that we can significantly reduce the systematic mislocations that result from applying JHD to very clustered seismicity if we introduce the appropriate set of constraints. 相似文献
69.
70.
Scales of predator detection behavior and escape in Fissurella limbata: A field and laboratory assessment
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The consumptive effects of predators are widely acknowledged, but predation can also impact prey populations through non‐consumptive effects (NCEs) such as costly antipredator behavioral responses. The magnitude of antipredator behavioral responses by prey is determined by an assessment of risk using sensory cues, which in turn is modulated by the environmental context. We studied the detection behavior and escape response of the keyhole limpet Fissurella limbata from the predatory sea star Heliaster helianthus. Through laboratory and field experimental trials, we quantified the distance and time of predator detection behavior by the prey, and measured their active escape responses when elicited. We found that predator detection by the limpet was chiefly mediated by distance, with experimental individuals capable of detecting predator presence effectively up to distances of at least 50 cm in the field and 70 cm under laboratory conditions. Our results indicate that this prey species is able to evaluate the proximity of its predator and use it as an indication of predation risk; therefore, predator–prey distance appears to be a primary predictor of the magnitude of the antipredator response. Given the tight relationship between predator distance and prey movement and the important role herbivores can play, particularly in this ecosystem, we expect that NCEs will cascade to the patterns of abundance and composition of rocky shore communities through changes in prey foraging behavior under risk. 相似文献