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761.
762.
763.
Assessing modern arboreal phytolith sensitivity to vegetation variations in temperate forest regions
Gui‐Zai Gao Dong‐Mei Jie De‐Hui Li Nan‐Nan Li Li‐Dan Liu Hong‐Yan Liu Cheng‐Cheng Leng Jiang‐Yong Wang Bao‐Jian Liu Ping Li 《Boreas: An International Journal of Quaternary Research》2019,48(3):731-745
To assess the reliability of arboreal phytoliths for differentiating vegetation types in temperate forest regions, we systematically analysed arboreal leaf phytoliths from 72 arboreal plants and 49 modern soils from three forest types in northeast China. The arboreal leaf phytolith production and morphotypes were highly variable between species. The arboreal leaf phytolith assemblages could clearly distinguish between broadleaf and coniferous species, but they were much less successful in differentiating broadleaved trees into subtaxa. Coniferous leaf morphotypes were successfully used to differentiate coniferous trees into families and subtaxa, especially in the Pinaceae. Two diagnostic broadleaved and six coniferous phytolith morphotypes were recognized within the modern soil beneath forest ecosystems. These arboreal phytoliths comprised up to 10–15% of the total soil phytoliths, and were dominated by coniferous types. Arboreal phytolith concentrations and phytolith assemblages in the soils fluctuated substantially amongst the three forest types. Soil arboreal phytolith assemblages were successfully used to differentiate samples from Larix mixed forest, broadleaf forest and Pinus koraiensis mixed forest. In addition, the arboreal index quantitatively distinguished the three forest types, with B/BE values <0.4 for Larix mixed forest samples, values from 0.4 to 0.6 for broadleaf forest samples, and values from 0.6 to 0.9 for P. koraiensis mixed forest. Thus, our surface soil arboreal phytolith assemblages and arboreal index are a useful reference for differentiating forest ecotypes, and they also provide reliable analogues for arboreal phytoliths from palaeoecological contexts in temperate forest regions. 相似文献
764.
Ancient town Dali is located in northwest Yunnan Province. With its ancient history and natural scenery, it is preserved as
one of the first 24 historical and cultural towns in China. Dali has become one of the most popular attractions for foreign
tourists since it had its first foreign visitors in 1983. As a result, English came into the life of the local people. This
paper presents and explains the results of questionnaires and interviews about Dali people’s attitude toward learning English.
Three types of questionnaires were designed to local businessmen, local residents and foreign tourists. Interviews were also
given whenever possible. In this study, businessmen in Dali were divided into two distinct groups. One group had their business
in “Foreigners’ Street”, which was in front of Hongshancha Hotel where many foreign tourists stayed. Another group had business
in Fuxin Street, which was vertically across “Foreigners’ Street”. The 41 shops and restaurants in “Foreigners’ Street” served
mainly foreign visitors, and most of them had English names and advertisements. The 353 shops and restaurants in Fuxin Street
mainly catered for domestic visitors but also served more and more overseas ones. Subjects from local residents were mostly
young people because aging ones were apparently not much affected by English. The results of the study showed that the oral
English levels became lower from “Foreigners’ Street” to Fuxin Street to local residents, due to declining frequency of contact
with foreign people. There were also distinct differences in general English level, the understanding of the importance of
English, the purposes of communicating with foreign tourists, the willingness and purposes of going on learning English between
businessmen in “Foreigners’ Street” and Fuxin Street: people in “Foreigners’ Street” had more positive feedback than those
in Fuxin Street because their constant contact with foreigners required them to speak better English which enabled them to
exchange with foreigners in many aspects, which in turn help them to know more about other cultures. On the other hand, Fuxin
Street businessmen would catch up with more and more prospective contact with overseas people. Though local residents had
nothing to do with foreign tourists, they met them in the street every day and might have to talk with them in unexpected
ways. They lived in a place where they saw English advertisement every day. Accordingly, study results showed that they were
very much motivated to learn English. They showed even stronger desire to learn more English than businessmen in “Foreigners’
Street”, though many of them were too young to tell why English was so important for them. This is an indication that English
has become part of the necessary education for young people in Dali. With the development of tourism, Dali is gradually becoming
a place where Chinese culture and western culture meet and coexist.
This project was supported by National Natural Science Foundation of China. 相似文献
765.
本文通过各阶升阶多边形之间的逼近程度,求出升阶多边形对Bezier曲线的逼近程度。给出了在曲线生成、弧长求值及面积求值中的应用。 相似文献
766.
In this paper, a new method of maintaining the high sensitivity and stability of a physically coated mercury film electrode
is proposed, and its mechanism is explained. The polarographic analysis procedure in this method can be simplified, the analysis
precision can be raised, and the life of the electrode can be prolonged. The method is practical.
Contribution No. 1338 from Inst. of Ocean., Academia Sinica. 相似文献
767.
该成矿区位于雪峰孤形构造带东北段,赋存在两条北东向断裂夹持并具矿源层特征的下奥陶统宁国组砂页岩中。矿脉呈中一陡倾斜柱板状产出,严格受断裂构造控制。成矿作用与构造活动同步,属动力变质热液矿床类型。 相似文献
768.
浙江中生代存在4个成盆期。以各个成盆期内盆地形成的运动学和动力学机制,划分成5大类型和6个基本型式及2个复合型式。它们是西太平洋陆缘活动的不同阶段所发育的。丽水运动以天台群、衢江群与永康群是区域不整合接触为特征,是白垩世内部一次重要的“变格运动。” 相似文献
769.
利用1981—2010年历史气象数据和2031—2060年(RCP2.6和RCP8.5)气候情景数据,根据橡胶寒害等级指标,结合插值分析、提取分析和地图代数等空间分析方法,研究在未来气候情景下我国橡胶树寒害事件的变化特征。结果表明:(1) RCP2.6和RCP8.5气候情景下2031—2060年我国橡胶种植适宜区基本呈现寒害发生降低的趋势,其中次适宜区(III)和局部可植区(IV)的降低幅度较为明显,有向高一等级适宜区转化的趋势。(2)我国橡胶树寒害中心的纬度,由1981—2010年的22.5°~23.5°N向北移动至2031—2060年RCP2.6情景下的24.0°~24.5°N和RCP8.5情景下的23.5°~24.0°N。(3) 2种气候情景下,2031—2060年我国海南、广西、广东、福建等植胶区橡胶树寒害发生概率(较基准时段1981—2010年)主要呈现降低趋势,云南植胶区在2种气候情景下有明显的差异,表现为RCP2.6情景下,轻度和特重寒害呈现降低趋势,中度和重度寒害呈现增加趋势;RCP8.5情景下,轻度和重度寒害呈现降低趋势,中度和特重寒害呈现增加趋势。(4)对比2种气候情景较基准时段的变化情况,RCP2.6情景对橡胶树轻度和特重寒害影响较大,RCP8.5情景对橡胶树中度和重度寒害影响较大。 相似文献
770.