全文获取类型
收费全文 | 32305篇 |
免费 | 5866篇 |
国内免费 | 8034篇 |
专业分类
测绘学 | 5195篇 |
大气科学 | 5639篇 |
地球物理 | 8640篇 |
地质学 | 14512篇 |
海洋学 | 4183篇 |
天文学 | 1435篇 |
综合类 | 2567篇 |
自然地理 | 4034篇 |
出版年
2024年 | 212篇 |
2023年 | 553篇 |
2022年 | 1100篇 |
2021年 | 1323篇 |
2020年 | 1507篇 |
2019年 | 1673篇 |
2018年 | 1378篇 |
2017年 | 1577篇 |
2016年 | 1708篇 |
2015年 | 1860篇 |
2014年 | 1987篇 |
2013年 | 2255篇 |
2012年 | 2120篇 |
2011年 | 2160篇 |
2010年 | 1717篇 |
2009年 | 2073篇 |
2008年 | 1985篇 |
2007年 | 2186篇 |
2006年 | 2065篇 |
2005年 | 1773篇 |
2004年 | 1612篇 |
2003年 | 1436篇 |
2002年 | 1317篇 |
2001年 | 1125篇 |
2000年 | 1066篇 |
1999年 | 977篇 |
1998年 | 920篇 |
1997年 | 781篇 |
1996年 | 707篇 |
1995年 | 607篇 |
1994年 | 569篇 |
1993年 | 480篇 |
1992年 | 316篇 |
1991年 | 255篇 |
1990年 | 205篇 |
1989年 | 166篇 |
1988年 | 151篇 |
1987年 | 96篇 |
1986年 | 45篇 |
1985年 | 38篇 |
1984年 | 25篇 |
1983年 | 2篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 14篇 |
1978年 | 15篇 |
1977年 | 10篇 |
1976年 | 3篇 |
1954年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
东吴小筑园林植物应用评价 总被引:1,自引:0,他引:1
彭丽彬 《云南地理环境研究》2004,16(4):75-78
园林植物配置是园林植物应用的重要内容,对充分发挥园林功能和观赏特性具有重要作用。通过对东吴小筑入口、前庭小院、主景区、山林区、园路、出口等6个功能区园林植物水平配置的现状调查,分析了本景区园林植物的物种多样性、水平结构、垂直结构、色彩变化等特征。结果表明:东吴小筑园林景观营造中.植物配置显示出较高水准。在树种选择、树丛组合、层次搭配、空间组织、色彩表现、季相变化等方面的设计布局十分精细,对今后园林设计及园林绿化水平的提高具有较好的指导作用。 相似文献
92.
93.
94.
The gravity field of the earth is a natural element of the Global Geodetic Observing System (GGOS). Gravity field quantities are like spatial geodetic observations of potential very high accuracy, with measurements, currently at part-per-billion (ppb) accuracy, but gravity field quantities are also unique as they can be globally represented by harmonic functions (long-wavelength geopotential model primarily from satellite gravity field missions), or based on point sampling (airborne and in situ absolute and superconducting gravimetry). From a GGOS global perspective, one of the main challenges is to ensure the consistency of the global and regional geopotential and geoid models, and the temporal changes of the gravity field at large spatial scales. The International Gravity Field Service, an umbrella “level-2” IAG service (incorporating the International Gravity Bureau, International Geoid Service, International Center for Earth Tides, International Center for Global Earth models, and other future new services for, e.g., digital terrain models), would be a natural key element contributing to GGOS. Major parts of the work of the services would, however, remain complementary to the GGOS contributions, which focus on the long-wavelength components of the geopotential and its temporal variations, the consistent procedures for regional data processing in a unified vertical datum and Terrestrial Reference Frame, and the ensuring validations of long-wavelength gravity field data products. 相似文献
95.
G. Cristiani G. Martínez C.H. Mandrini C.G. Gimnez de Castro M.G. Rovira P. Kaufmann H. Levato 《Journal of Atmospheric and Solar》2005,67(17-18):1744
We present a detailed study of a 1B/M6.9 impulsive flare combining high time resolution (1 ms) and instantaneous emission source localization observations at submillimeter frequencies (212 GHz), obtained with the solar submillimeter telescope (SST), and Hα data from the Hα solar telescope for argentina (HASTA). The flare, starting at 16:34 UT, occurred in active region (AR) 9715 (NOAA number) on November 28, 2001, and was followed by an Hα surge. We complement our data with magnetograms from the Michelson Doppler Imager (SOHO/MDI). SST observed a short impulsive burst at 212 GHz, presenting a weak bulk emission (of about 90 sfu) composed of a few shorter duration structures. The integrated Hα and the 212 GHz light curves present a remarkable agreement during the impulsive phase of the event. The delay between both curves stays below 12 s (the time resolution of the Hα telescope). The flare as well as the surge are linked to new flux emergence very close to the main AR bipole. Taking into account the AR magnetic field evolution, we infer that magnetic field reconnection, occurring at low coronal levels, could have been at the origin of the flare; while in the case of surge this would happen at the chromospheric level. 相似文献
96.
Distribution of chlorophyll-a off the Changjiang River and its dynamic cause interpretation 总被引:1,自引:1,他引:1
ZHU Jianrong State Key Laboratory of Estuarine Coastal Research East China Normal University Shanghai China 《中国科学D辑(英文版)》2005,48(7)
Red tide,also called harmful algal bloom interna-tionally,is a disaster abnormal phenomenon of oceanecology with an explosive breed or dense assemble ofone or several phytoplanktons in a specific ocean en-vironment condition,colors the seawater,influencesand harms ocean living things.The formation of redtide is controlled mainly by a complex interplay ofbiological,physical and chemical processes,but themost main cause influencing the occurrence of red tideis the seawater eutrophication,i.e.,the… 相似文献
97.
The time history of strong ground motion can be synthesized by empirical Green's function (EGF) method.Firstly a large seismic event is discretized into a series of subevents; secondly recordings of earthquakes with proper size and spatial distribution are chosen as time history (EGF) of those subevents; finally the EGFs are summated to get the time history of ground motion caused by the large event. 相似文献
98.
Differential GPS (DGPS) and Differential Interferometric Synthetic Aperture Radar (DInSAR) analyses were applied to the Kos-Yali-Nisyros Volcanic Field (SE Hellenic Volcanic Arc) to quantify the ground deformation of Nisyros Volcano. After intense seismic activity in 1996, a GPS network was installed in June 1997 and re-occupied annually up to 2002. A general uplift ranging from 14 to 140 mm was determined at all stations of the network. The corresponding horizontal displacements ranged from 13 to 53 mm. The displacement vectors indicate that the island is undergoing extension towards the East, West and South. A two-source “Mogi” model combined with assumed motion along the Mandraki Fault was constructed to fit the observed deformation. The best-fit model assumes sources at a depth of 5500 m NW of the centre of the island and at 6500 m offshore ESE of Yali Island. DInSAR analysis using four pairs of images taken between May 1995 and September 2000 suggests that deformation was occurring during 1995 before the start of the seismic crisis. An amplitude of at least 56 mm along the slant range appeared for the period 1996 through 1999. This deformation is consistent with the two-source model invoked in DGPS modelling. Surface evidence of ground deformation is expressed in the contemporaneous reactivation of the Mandraki Fault. In addition, a 600 m long N-S trending irregular rupture in the caldera floor was formed between 2001 and 2002. This rupture is interpreted as the release of surface stress in the consolidated epiclastic and hydrothermal sediments of the caldera floor. 相似文献
99.
工程勘察设计行业信息化建设问题反思及其新领域应用开发综述 总被引:2,自引:0,他引:2
本文通过对勘察设计行业信息化建设的深入思考,总结并提出了在设计院信息化建设七个领域应用开发的新思路。 相似文献
100.