全文获取类型
收费全文 | 8303篇 |
免费 | 330篇 |
国内免费 | 71篇 |
专业分类
测绘学 | 258篇 |
大气科学 | 644篇 |
地球物理 | 2562篇 |
地质学 | 2928篇 |
海洋学 | 578篇 |
天文学 | 1276篇 |
综合类 | 35篇 |
自然地理 | 423篇 |
出版年
2022年 | 64篇 |
2021年 | 133篇 |
2020年 | 144篇 |
2019年 | 110篇 |
2018年 | 310篇 |
2017年 | 295篇 |
2016年 | 418篇 |
2015年 | 295篇 |
2014年 | 364篇 |
2013年 | 478篇 |
2012年 | 400篇 |
2011年 | 456篇 |
2010年 | 372篇 |
2009年 | 434篇 |
2008年 | 362篇 |
2007年 | 298篇 |
2006年 | 323篇 |
2005年 | 289篇 |
2004年 | 382篇 |
2003年 | 286篇 |
2002年 | 205篇 |
2001年 | 181篇 |
2000年 | 143篇 |
1999年 | 118篇 |
1998年 | 160篇 |
1997年 | 105篇 |
1996年 | 67篇 |
1995年 | 71篇 |
1994年 | 80篇 |
1993年 | 65篇 |
1992年 | 78篇 |
1991年 | 56篇 |
1990年 | 83篇 |
1989年 | 47篇 |
1988年 | 39篇 |
1987年 | 48篇 |
1986年 | 47篇 |
1985年 | 35篇 |
1984年 | 47篇 |
1983年 | 42篇 |
1982年 | 39篇 |
1981年 | 46篇 |
1980年 | 34篇 |
1978年 | 46篇 |
1977年 | 44篇 |
1976年 | 40篇 |
1975年 | 41篇 |
1974年 | 39篇 |
1973年 | 44篇 |
1971年 | 48篇 |
排序方式: 共有8704条查询结果,搜索用时 125 毫秒
51.
52.
53.
Antonín Papež 《Studia Geophysica et Geodaetica》1964,8(2):200-204
Резюме Дабление воздуха, переснитанное иа уровень моря по стандартной атмосфере в Q-коде обозчачается через QNH. Давление воздуха
пересчитанное на уровень моря по высотной барометрической формуле обознаеается через QFF. Для целей авиационной службы погоды
должны быть известны значения QNH, однако Зе барическое поле на синоптических картах выражается через QFF. С помощью рис.
1 для соответствующей температуры воздуха на станцин и ее высоты н. у. м. можно определить разность значений QFF—QNH при давленин
QFF=1000мб. Далее по табл. 2 можно определить поправку для каждого значения QFF отличного от значения QFF при ином давлении, чем 1000мб путем умножения табулированного значения ва разность QFF—1000мб и его алгебраического сложения со значением, полученным по рис. 1.
相似文献
54.
55.
Резюме С помощью принятия простых кинематических предположений и на основании ω—уравнения выла определена конфигурация полос облаков
в полностью окклюдированном циклоне без фронтов. Облачная система определяется полем скрытой теплоты, выделяемой в процессах
конденсации. Полосы облаков теоретически представляют собой в основном листы синусоидальной спирали.
Address: Boční II, Praha 4-Spořilov. 相似文献
Address: Boční II, Praha 4-Spořilov. 相似文献
56.
57.
The longitudinal strength of the high-speed ferry was investigated by subjecting the ship's hull girder to long-term loads obtained from a frequency-domain panel code. Prior to the statistical analysis, linearly computed transfer functions were corrected for nonlinear effects, yielding two sets of transfer functions valid for different wave amplitudes. One set corresponded to the hogging condition; the other set, to the sagging condition. Two regular equivalent design waves were specified that resulted in loads representing the most severe global design load conditions. The still-water loading condition, yielding a still-water vertical bending moment in hogging, was superimposed on the wave-induced loads to obtain the total (design) loads in hogging. For the sagging condition only, additional impact-related loads were superimposed to obtain the total (design) loads in sagging. A finite element model of the ship's structure was subjected to pressure distributions according to the two regular design waves. For comparison with classification society rule values, a simple beam theory strength analysis of the ship's midship section was performed first, and then another finite element analysis was carried out, whereby the imposed loads were tuned to the rule values of vertical bending moments. Rule-based magnitudes of nominal maximum longitudinal stress deviated significantly (25–39%) from comparable stresses obtained by the panel code based finite element analysis. However, stresses obtained from the rule-based finite element analysis agreed more favorably, especially in hogging. In the uppermost deck, for example, the panel code based compressive stress was only 9% larger than the comparable stress from the rule-based finite element analysis. 相似文献
58.
C. Riedel A. Tryggvason B. Brandsdottír T. Dahm R. Stéfansson M. Hensch R. Böðvarsson K. S. Vogfjord S. Jakobsdottír T. Eken R. Herber J. Holmjarn M. Schnese M. Thölen B. Hofmann B. Sigurdsson S. Winter 《Marine Geophysical Researches》2006,27(4):267-281
Between June 2004 and September 2004 a temporary seismic network was installed on the northern insular shelf of Iceland and onshore in north Iceland. The seismic setup aimed at resolving the subsurface structure and, thus, the geodynamical transition from Icelandic crust to typical oceanic crust along Kolbeinsey Ridge. The experiment recorded about 1,000 earthquakes. The region encloses the Tjörnes Fracture Zone containing the Husavik–Flatey strike-slip fault and the extensional seismic Grimsey Lineament. Most of the seismicity occurs in swarms offshore. Preliminary results reveal typical mid-ocean crust north of Grimsey and a heterogeneous structure with major velocity anomalies along the seismic lineaments and north–south trending subsurface features. Complementary bathymetric mapping highlight numerous extrusion features along the Grimsey Lineament and Kolbeinsey Ridge. The seismic dataset promises to deliver new insights into the tectonic framework for earthquakes in an extensional transform zone along the global mid-ocean ridge system. 相似文献
59.
采用Wilbert蛋白银法及Chatton—Lwoff银浸法对一种附生于栉孔扇贝鳃丝上的寄生车轮虫进行了光镜水平下的研究。依据其形态学和纤毛图式特征,该种被鉴定为TrichodinajadranicaRaabe,1958.此为我国新记录,同时也是第一例有关外寄生于扇贝鳃表纤毛虫原生动物的报道。 相似文献
60.
Georg Irion Jens Müller Jose Nunes de Mello Wolfgang J. Junk 《Geo-Marine Letters》1995,15(3-4):172-178
The Quaternary history of the Amazon lowlands is characterized by deposition of sediments of Andean provenance and by the influences of changing sea levels. Areas well above the present water tables were not reached by Pleistocene high-water stages. These areas have been intensively weathered since the Tertiary, forming hard lateritic weathering horizons. These weathering horizons are best explained by the relatively constant, humid tropical climate throughout the Quaternary. In the western Amazonian Lowland, flood plains corresponding to the different Pleistocene sea-level heights were formed. During low sea level, erosion in the drainage areas increased and the water levels of the central Amazon River system were lowered. Valleys drowned and lakes formed in the lower reaches of rivers and creeks during high sea-level stages. These lakes (ria lakes) remained in the valleys with rivers having a low sediment load. Seismic profiling (3.5 kHz) in some of these lakes clearly showed deposits of the three last periods of Quaternary high sea-level stages. 相似文献