全文获取类型
收费全文 | 72620篇 |
免费 | 2661篇 |
国内免费 | 3208篇 |
专业分类
测绘学 | 2283篇 |
大气科学 | 6303篇 |
地球物理 | 13681篇 |
地质学 | 30567篇 |
海洋学 | 6681篇 |
天文学 | 13339篇 |
综合类 | 1227篇 |
自然地理 | 4408篇 |
出版年
2022年 | 903篇 |
2021年 | 1270篇 |
2020年 | 1236篇 |
2019年 | 1360篇 |
2018年 | 4495篇 |
2017年 | 4157篇 |
2016年 | 3308篇 |
2015年 | 1397篇 |
2014年 | 1937篇 |
2013年 | 2784篇 |
2012年 | 2986篇 |
2011年 | 4942篇 |
2010年 | 4410篇 |
2009年 | 4831篇 |
2008年 | 4098篇 |
2007年 | 4649篇 |
2006年 | 2326篇 |
2005年 | 1857篇 |
2004年 | 1758篇 |
2003年 | 1915篇 |
2002年 | 1690篇 |
2001年 | 1330篇 |
2000年 | 1158篇 |
1999年 | 1082篇 |
1998年 | 991篇 |
1997年 | 1018篇 |
1996年 | 838篇 |
1995年 | 818篇 |
1994年 | 722篇 |
1993年 | 628篇 |
1992年 | 568篇 |
1991年 | 525篇 |
1990年 | 523篇 |
1989年 | 497篇 |
1988年 | 443篇 |
1987年 | 460篇 |
1986年 | 470篇 |
1985年 | 547篇 |
1984年 | 587篇 |
1983年 | 578篇 |
1982年 | 532篇 |
1981年 | 488篇 |
1980年 | 471篇 |
1979年 | 432篇 |
1978年 | 391篇 |
1977年 | 400篇 |
1976年 | 361篇 |
1975年 | 371篇 |
1974年 | 352篇 |
1973年 | 384篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
821.
Temperature of the ocean surface as an indicator of thermodynamic processes in the northwest Pacific
The numerical computations and analysis of the anomalies of temperature of the ocean surface in the northwest part of the Pacific Ocean were carried out on the basis of the archival data for 1960 and 1964–1985. A five-year period of general instability of the annual average temperature was revealed (1973–1977). In this period, the year 1974 was the coldest and the year 1977 was characterized as extremely warm. We performed the analysis of the interannual and annual variability of the anomalies of temperature of the ocean surface and revealed common features and distinctions of the seasonal evolution of these anomalies for years with substantially different temperature conditions. A quasistationary zone of maximally heated waters was discovered in the band located (independently of the year and season) between 36 and 46°N to the east of 140°E. This zone coincides in space with the zone of the subarctic front and the south part of the subarctic region. The influence of the meanders of the Kuroshio Current was demonstrated. It is shown that their activity increases after the events of El-Niño and, hence, the thermal energy of the water area considerably increases and remains elevated for a period of 1–2 yr after the indicated events.Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 45–52, September–October, 2004.This revised version was published online in May 2005 with corrections to cover date. 相似文献
822.
N. M. Gavrilov 《Izvestiya Atmospheric and Oceanic Physics》2007,43(4):451-460
Data of an experiment on radio occultation sounding of the atmosphere with the use of GPS signals were used to obtain global distributions of the variances of mesoscale variations in the refractive index in the troposphere and stratosphere. The experiment was carried out with the CHAMP satellite during the period 2001–2005. Measured vertical profiles were smoothed inside 5–10-km-thick layers centered at different altitudes in the troposphere and stratosphere with the use of second-degree polynomials. Deviations from the smoothed quantities and the corresponding variances were obtained for each profile and averaged for each month during the analyzed interval of the CHAMP experiment. Altitude-longitude-latitude inhomogeneities in the distribution of refractive index variances were analyzed. Altitude and latitude distributions of maxima and minima of refractive index variances depend on altitude and season. Turbulence and acoustic gravity waves can be the causes of small-scale and mesoscale variations in the refractive index of the troposphere and stratosphere. The variances of variations in the refractive index are greater in the regions of tropospheric jet streams and in the zones of near-equatorial deep convection. Atmospheric disturbances increase over mountain systems. 相似文献
823.
824.
INTRODUCTIONTheDenglouCape ,inthesouthwestoftheLeizhouPeninsula ,isatthenorthmarginoftropicalzone .SeveralresearchesandcartographiesoftheregionalgeomorphologyandQuater narygeology ,whichwerecarriedoutinthepast,allincludethisarea (MGL ,SCSIO ,CAS ,1 978;GPCSGRCZT… 相似文献
825.
作者采用自由基引发氧化模型。通过测定卵磷脂氢过氧化物 ( PCOOH) ,研究了“916”低聚糖对卵磷脂 ( PC)氧化的抑制作用。实验结果表明 :( 1)“916”低聚糖具有良好的抗氧化活性 ;( 2 )各低聚糖在质量相同和含硫量大致相同的条件下 ,总体上分子量越小抗氧化活性越高。 相似文献
826.
运城盆地11 kaBP以来气候环境变迁与湖面波动 总被引:7,自引:0,他引:7
通过黄土区湖泊沉积研究来恢复古气候、古环境,是对黄土区古气候、古环境研究的补充和检验。通过山西运城盆地硝地湖泊沉积物的多环境代用指标分析,结合史料记载,探讨了该地区11kaBP以来古气候演化和湖面波动的历史。结果表明,该地区存在YD(Younger Dryas)事件,进入全新世后气候有显著的趋势,最高湿润度发生在7.88-5.15和5kaBP后,气候逐渐变干,湖面波动与气候波动相关,全新世早期湖面开始上升,湖泊扩张,5kaBP后湖泊萎缩,盐类结晶析出。 相似文献
827.
具有国际先进水平的CTD定标检测设备 总被引:1,自引:0,他引:1
在国家863计划的支持下,海洋技术研究成功研制了一套CTD仪器的校准设备,本文介绍了设备的组成,性能,设计经过与SBE设备进行了比较,表明该设备达到了EOCECTD设备的校准要求,同时,该设备是海洋技术研究所开发自有的高度CTD剖面仪的有力工具。 相似文献
828.
829.
William A. Watkins Mary Ann Daher Joseph E. George David Rodriguez 《Deep Sea Research Part I: Oceanographic Research Papers》2004,51(12):1889-1901
A unique whale call with 50–52 Hz emphasis from a single source has been tracked over 12 years in the central and eastern North Pacific. These calls, referred to as 52-Hz calls, were monitored and analyzed from acoustic data recorded by hydrophones of the US Navy Sound Surveillance System (SOSUS) and other arrays. The calls were noticed first in 1989, and have been detected and tracked since 1992. No other calls with similar characteristics have been identified in the acoustic data from any hydrophone system in the North Pacific basin. Only one series of these 52-Hz calls has been recorded at a time, with no call overlap, suggesting that a single whale produced the calls. The calls were recorded from August to February with most in December and January. The species producing these calls is unknown. The tracks of the 52-Hz whale were different each year, and varied in length from 708 to 11,062 km with travel speeds ranging from 0.7 to 3.8 km/h. Tracks included (A) meandering over short ranges, (B) predominantly west-to-east movement, and (C) mostly north-to-south travel. These tracks consistently appeared to be unrelated to the presence or movement of other whale species (blue, fin and humpback) monitored year-round with the same hydrophones. 相似文献
830.
Jan E. Vermaat Rene N. Rollon Cristina Day A. Lacap Claire Billot Filipe Alberto Hildie M.E. Nacorda Frank Wiegman Jorge Terrados 《Journal of Sea Research》2004,52(4):201
Flower and fruit production of the abundant, tall, long-lived, dioecious, surface-pollinating seagrass species Enhalus acoroides (L.) Royle were estimated at seven sites in the reef flats off Bolinao (NW Luzon, The Philippines) featuring different fragmentation of the seagrass meadows. Fragmentation of the seagrass meadow was quantified as cover of E. acoroides and all seagrass species present in 20×20 m plots. E. acoroides and overall seagrass cover were correlated positively. The proportion of female flowers of E. acoroides that developed a fruit increased sharply as overall seagrass cover was around 50%. Apparent sex ratio bore no relationship with overall seagrass cover. This threshold-type of relationship suggests that fragmentation of seagrass meadows can have a major effect on the reproductive output of this species. A possible mechanism underlying these results would be a non-linear increase of the efficiency of trapping the surface-dispersed pollen with increasing seagrass canopy density. This provides the first evidence based on real data that fragmentation can affect the population dynamics of seagrass species. 相似文献