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11.
Chan Kwing Lam 《紫金山天文台台刊》2003,(2)
1 IntroductionManybottlenecksinthetheoreticalstudyofstellarevolutionarisefromthelackofunder standingofsomehighlycomplicatedprocessesthatcannotbetreatedwithanalyticaltech niques .Alargeportionoftheseprocessesisrelatedtohydrodynamics,particularlyconvec tion .Theapplicationofmultidimensionalnumericalcomputationstotheinvestigationofthesedifficultproblemshasmadegreatprogressinrecentyears .Here ,weprovideasurveyoftherecentnumericalstudiesofconvectionrelatedproblems.Theobjectiveistoassistthosewhoar… 相似文献
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土壤干湿交替促进硒酸盐的还原作用 总被引:3,自引:0,他引:3
采集不同类型的新鲜土壤,经处理获得其风干、烘干的样品,重新潮湿后,加入一定量的Na2SeO4溶液,进行了培育实验(incubationexperiments)。实验结果表明,随着土壤干燥程度的增加,硒酸盐还原作用的速度也随之加快。这进一步证实,作为一种地球化学营力的土壤干湿交替,通过对土壤水势(soilwaterpotential)、微生物群落等的影响,间接地促进了硒酸盐还原作用,因而成为硒生物地球化学循环的驱动力之一。 相似文献
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利用EQIM软件建设和拓展广西地震速报系统 总被引:1,自引:0,他引:1
介绍在全国EQIM软件基础上,结合广西地震台网速报工作的需要,开发适用于广西区域台网内部使用的广西地震速报系统,其基本功能包括:地震速报、信息共享、手机短信发布、Web互联网查询数据资料、数据汇集等多个方面.广西地震速报系统的建立可提高地震速报信息向各级部门的快速传递能力,并为分析预报人员提供及时的地震数据服务. 相似文献
16.
本文概述由国家自然科学基金委员会与大庆油田联合资助的九五油储重大项目的立项背景、研究目标和学科内涵、实验基地及地质目标、组织措施、具体成果概述、实际效果、人才培养和九五油储后续的重大成果产出等相关内容. 相似文献
17.
Yoon-Seok Timothy Hong Byeong-Cheon Paik 《Stochastic Environmental Research and Risk Assessment (SERRA)》2012,26(5):695-707
Developing a mathematical model for predicting fecal coliform bacteria concentration is very important because it can provide a basis for water quality management decisions that can minimize microbial pollution risk to the public. This paper introduces a hybrid modeling methodology which is a combined use of a neural network-based pattern analysis and an evolutionary process model induction system. The neural network-based pattern analysis technique is applied to extract knowledge on inter-relationships between fecal coliform concentrations and other measurable variables in a sewer system. Based on the result of neural network-based pattern analysis, an evolutionary process model induction system is used to derive mathematical inference models that can predict fecal coliform bacteria concentration from easily measurable variables instead of directly measuring fecal coliform bacteria concentration in a sewer system. The neural network-based pattern analysis extracts that temperature and ammonia concentration are the most important driving forces leading to an increase in fecal coliform bacteria concentration in the sewer system at Paraparaumu City, New Zealand. Fecal coliform bacteria concentration is also positively correlated with dissolved phosphorus and inversely with flow rate. The multivariate inference models that are able to predict fecal coliform bacteria concentration are successfully derived as functions of flow rate, temperature, ammonia, and dissolved phosphorus in the form of understandable mathematical formulae using the evolutionary process model induction system, even if a priori mathematical knowledge of the dynamic nature of fecal coliform bacteria is poor. The multivariate inference models evolved by the evolutionary process model induction system produce a slightly better performance than the multi-layer perceptron neural network model. 相似文献
18.
Characteristics of particle size for creeping and saltating sand grains in aeolian transport
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Hong Cheng Jiajia He Xueyong Zou Jifeng Li Chenchen Liu Bo Liu Chunlai Zhang Yongqiu Wu Liqiang Kang 《Sedimentology》2015,62(5):1497-1511
Creep and saltation are the primary modes of surface transport involved in the fluid‐like movement of aeolian sands. Although numerous studies have focused on saltation, few studies have focused on creep, primarily because of the experimental difficulty and the limited amount of theoretical information available on this process. Grain size and its distribution characteristics are key controls on the modes of sand movement and their transport masses. Based on a series of wind tunnel experiments, this paper presents new data regarding the saltation flux, obtained using a flat sampler, and on the creeping mass, obtained using a specifically designed bed trap, associated with four friction velocities (0·41, 0·47, 0·55 and 0·61 m sec?1). These data yielded information regarding creeping and saltating sand grains and their particle size characteristics at various heights, which led to the following conclusions: (i) the creeping masses increased as a power function (q = ?1·02 + 14·19u*3) of friction wind velocities, with a correlation (R2) of 0·95; (ii) the flux of aeolian sand flow decreases exponentially with increasing height (q = a exp(–z/b)) and increases as a power function (q = ?26·30 + 428·40 u*3) of the friction wind velocity; (iii) the particle size of creeping sand grains is ca 1·15 times of the mean diameter of salting sand grains at a height of 0 to 2 cm, which is 1·14 times of the mean diameter of sand grains in a bed; and (iv) the mean diameter of saltating sand grains decreases rapidly with increasing height whereas, while at a given height, the mean diameter of saltating sand grains is positively correlated with the friction wind velocity. Although these results require additional experimental validation, they provide new information for modelling of aeolian sand transport processes. 相似文献
19.
Hangyu Dong Baohua Guo Yizhe Li Kai Si Long Wang 《Geotechnical and Geological Engineering》2017,35(3):1169-1183
The prime objective of this work is to provide a reference to predict the peak shear strength of rock fractures. The paper studied some shear properties of rock fractures and proposed an empirical formula for the peak shear strength of rock fractures based on 3D morphology parameters. The rock fractures were induced in cylindrical sandstone and marble specimens by means of indirect tension. A rock direct shear apparatus (RDS-200) was adopted to conduct direct shear tests on five groups of rock fractures under different levels of normal load. Before the direct shear test, 3D morphology parameters of rock fracture surfaces were obtained using a 3D optical scanner. By analyses of direct shear test data, the relationships between peak shear strength, peak shear displacement, peak dilatancy angle, residual friction coefficient and peak normal stress were found. According to the evolution trends of peak shear strength and peak dilatancy angle along with the normal stress, an empirical formula was proposed to predict the peak shear strength of rock fractures in both sliding and cutting failure modes considering the 3D morphology parameters of rock fracture surfaces. The empirical formula could be commonly used for different types (sandstone and marble) and grain sizes (powder-grained, fine-grained, medium-grained and coarse-grained) of rock fractures. 相似文献
20.
高星级酒店外籍管理者对广州地方景观的感知与跨文化认同 总被引:2,自引:1,他引:2
全球化是当今世界最重要的特征之一。有关跨国移民对城市景观的感知和跨文化认同研究也得到越来越多的关注。在文献回顾的基础上, 以广州高星级酒店外籍管理者作为研究对象, 通过定性研究进行数据的收集和分析, 构建了外籍管理者对城市地方景观感知和跨文化认同的形成演变机制, 并得出以下结论:① 在职业影响下, 外籍管理者对迁入城市产生了被动的地方认同, 进而形成了被迫同化的跨文化认同模式;② 外籍管理者基于身份构建对城市地方景观进行感知, 对反映“他者”、“我者”和“世界人”身份的景观感知度较高, 反映出他们对故乡和迁入城市的地方认同, 从而产生了同时具有整合和边缘特征的跨文化认同模式;③ 外籍管理者通过迁入城市的地方景观感知而产生地方意义的解读, 基于对迁入城市正面的地方意义解读, 对城市产生了地方认同和整合的跨文化认同模式, 基于对迁入城市负面的地方意义解读, 对城市产生了地方不认同和分隔的跨文化模式。研究结论丰富了城市景观研究和跨文化认同研究的相关理论成果, 并为中国跨国移民政策和国际化城市建设提供了可供借鉴的实践参考。 相似文献