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721.
为了开展寒旱山区典型流域融雪径流过程的研究,提高融雪径流模型(SRM)在山区融雪地区的水文过程模拟精度,本文选取新疆提孜那甫河流域作为典型研究区,在SRM径流计算基础上,加入合适的基流数据并进行不确定性分析。考虑4种常见的基流分割方法(数字滤波法、加里宁法、BFI法(滑动最小值法)和HYSEP(hydrograph separation program)法),基于贝叶斯理论,采用马尔科夫链蒙特卡洛(MCMC)模拟进行参数不确定性分析,对使用不同基流数据SRM的融雪径流模拟表现进行综合评价。分析结果表明,基于加里宁基流分割方法的模型(SRMK)能够最佳地模拟研究区融雪径流过程(纳什系数NSE在识别期和验证期分别为0.866和0.721,大于其他对比模型)。MCMC模拟能够较好地识别SRM参数,获得可靠的参数后验概率分布。当实测降水资料缺乏或其代表性较差时,TRMM(tropical rainfall measuring mission)卫星数据能够描述研究区的降水过程特征。 相似文献
722.
According to a long series of measured sediment data, the sedimentation effects of the Dongting Lake Area (DLA) were studied in light of the relationship between sedimentation characteristics and resources and environment. The result shows that the long-term deposition and the impact of human activities have led to a cycle of the evolution of sedimentation pattern, resulting in sediment disaster effects and resources effects in the DLA. The main features are as follows: 1) The water beach, silt beach, lake marsh beach, reed beach and other types of beach shaped by sedimentation effects constitute the main body of the giant lake system. 2) The disaster chains are induced, i.e., sedimentation → marshland expansion and reclamation → flood function decline, fish resource depletion, biodiversity reduction disaster chain, sedimentation → marshland expansion → floods, water pollution disaster chain, sedimentation → marshland floating vegetation rising → schistosomiasis, rodents virulence disaster chain, sedimentation → flood embankment bursting → land desertification disaster chain. 3) Sedimentation has created about 98.13×104 hm2 of land in the past 55 years. Rational development and utilization of marshland resources have produced tremendous economic benefits. 相似文献
723.
724.
基于集对分析和模糊马尔可夫链的滑坡变形预测新方法研究 总被引:4,自引:1,他引:3
滑坡体的变形表现出复杂的非线性演化特征,为克服传统分析方法在处理系统不确定性方面的不足,引入集对分析(SPA)理论,并结合模糊马尔可夫(fuzzy-Markov)理论来对滑坡SPA模型中的不确定系数进行二次预测,提出了滑坡变形SPA-fuzzy-Markov预测新模型。针对fuzzy-Markov子系统,分别提出了基于相关系数和特征值方差的多维空间模糊马尔可夫链拟合效果检验的两个新方法,并据此定量考察fuzzy-Markov子系统对参数响应的敏感性,用以确定最佳的模型参数组合。运用上述理论模型对刘家沱滑坡变形监测成果进行分析,综合定量考察了模型对模糊区间重合等级和马尔可夫状态转移步数这两个参数的敏感程度。结果表明:该算例条件下状态转移步数为敏感因子;与单纯SPA模型相比,复合模型能够进一步提高整体预测精度,在岩土监测分析领域中具有良好的实用价值;同时fuzzy-Markov理论的引入也为深化SPA基础理论研究提供了一条途径,不仅在岩土监测领域,在其他相关领域也具有理论和实用价值。 相似文献
725.
结合支持向量机和马尔可夫链,提出了一种新的位移时序预测模型--支持向量机-马尔可夫链预测模型(SVM-MC)。通过对实测位移值的学习,利用经粒子群算法优化的支持向量机对位移时间序列的宏观发展趋势进行滚动预测;在此基础上应用马尔可夫链确定位移时序的状态转移概率矩阵,通过对状态的划分、实测值与支持向量机拟合值的绝对误差及相对误差等指标的分析,实现了对预测结果的改进。将该模型应用到某工程永久船闸高边坡的位移时序预测中,结果表明,该模型具有科学可靠、预测精度高的优点,在岩土体位移时序预测中具有有一定工程应用价值。 相似文献
726.
丹霞地貌是我国五大地貌之一,具有极大的科研和观赏价值。剑门关丹霞地貌具有年代新、类型多、分布较集中等特点,主要形成于侏罗—白垩纪,沉积岩层自下而上包括上侏罗统的遂宁组、莲花口组和下白垩统的剑门关组。根据沉积序列与旋回研究,将剑门关丹霞地貌沉积相划分为山麓-洪积扇、河流、湖泊、三角洲沉积相,运用马尔科夫链法建立丹霞地貌的沉积相序,形成沉积相模式,对研究剑门关丹霞地貌的古地理和古环境具有重要意义。 相似文献
727.
In current Naval Architecture practice, employing static considerations is an important and necessary step in assessing ship stability and seakeeping properties (e.g. inclining experiments, load line regulations, range of stability calculations). However, damaged vessels and vessels operating in heavy weather or in conditions where topside icing is a concern may require an additional assessment of stability that considers dynamic effects. Within such contexts, the actual (i.e. current) second moment properties of the vessel mass become very important in the associated equations of motion for a given ship. One such critical second mass moment property is the roll gyradius, as it is closely related to the occurrence of capsizing. The present paper furnishes a means for reckoning the actual roll gyradius of a given ship operating within a seaway. The approach hinges on the formulation and solution of a stochastic inverse problem that leverages existing seakeeping software against the shipboard inertial measurement unit (IMU) telemetry. The method is demonstrated at full-scale and validated at model scale. 相似文献
728.
《Marine Policy》2017
Over the past two decades, there has been a proliferation of consumer-facing, market-based initiatives for marine conservation—most notably in seafood eco-labels and sustainability certifications. Yet, despite the growing recognition of these initiatives by consumers and retailers in North America and Europe and the (subsequent) acceptance of their role in seafood distribution by fisheries and fish marketing industries around the world, seafood certification programs have thus far made little progress in Japan. Here, the evolution of the three seafood eco-label and certification programs in Japan is examined and insights into the ongoing challenges they face in terms of the domestic supply chain network, consumer preference and their social-cultural attitude toward sustainability are provided. Despite an initial lack of success, seafood certification programs in Japan can be useful in enhancing consumer awareness for fisheries resource conservation and identifying Japanese domestic small-scale fisheries that are already engaged in sustainable fishing practices. A possible pathway for developing an eco-certification program suitable for the Japanese seafood market is provided through integration of environmental and cultural sustainability under the existing certification framework. 相似文献
729.
《Marine Policy》2017
Cod and haddock are two of the “big 5” UK supermarket fish species and intrinsic to fish and chip shops nationwide. UK whitefish fleets produce a significant amount, however there is a reliance on imports to maintain supply. The UK is in a strong position to compete for raw material from Iceland and Norway given high prices paid for imports and investment by Icelandic and Norwegian companies in the UK. Regarding UK production of whitefish, the European Common Fisheries Policy landing obligation has introduced significant uncertainty. To avoid discarding of any quota stock, fishing may be stopped before all target stocks quota is reached. For demersal fleets, there is a transition period between 2016 and 18 where target stocks are introduced according to Advisory Council and EU agreement and Article 15, with all quota stocks from 2019. As the capacity of the fleets balance to the new regulations, supply will likely return and if maximum sustainable yield (MSY) is reached in 2020 then an increase in TACs from current levels is likely too. However, markets and industries can change in a short period. Particularly, most processing companies are small to medium size enterprises and those that concentrate on cod and haddock may have to adjust their business. Fleets could be resilient to such short term reductions in landings however this cannot be assumed. The competitiveness of producers will surely be affected in the short to medium term as a result. 相似文献
730.
《Marine Policy》2017
A value chain analysis is conducted to identify upgrading, that is, improvements in quality and product design that enable producers to gain enhanced value or through diversification in the product lines served. However, a range of data and information of use to managing small-scale fisheries can be also be produced. Eight value chain studies, carried out for specific fish species in different locations around the Philippines, are examined. Policy and management lessons learned and interventions resulting from the value chain analysis for small-scale fisheries management are discussed. Recommendations for using value chain analysis in small-scale fisheries management include stricter regulation on size limits of harvest, monitoring schemes, certification processes, post-harvest facilities, seasonal closures, social enterprises, credit facilities, and habitat protection. 相似文献