全文获取类型
收费全文 | 26995篇 |
免费 | 5183篇 |
国内免费 | 9719篇 |
专业分类
测绘学 | 2814篇 |
大气科学 | 8922篇 |
地球物理 | 5633篇 |
地质学 | 11425篇 |
海洋学 | 5741篇 |
天文学 | 1496篇 |
综合类 | 2147篇 |
自然地理 | 3719篇 |
出版年
2024年 | 237篇 |
2023年 | 619篇 |
2022年 | 1059篇 |
2021年 | 1274篇 |
2020年 | 1444篇 |
2019年 | 1626篇 |
2018年 | 1289篇 |
2017年 | 1453篇 |
2016年 | 1480篇 |
2015年 | 1644篇 |
2014年 | 1796篇 |
2013年 | 2028篇 |
2012年 | 1979篇 |
2011年 | 1930篇 |
2010年 | 1573篇 |
2009年 | 1802篇 |
2008年 | 1792篇 |
2007年 | 2165篇 |
2006年 | 2005篇 |
2005年 | 1750篇 |
2004年 | 1535篇 |
2003年 | 1254篇 |
2002年 | 1145篇 |
2001年 | 940篇 |
2000年 | 1005篇 |
1999年 | 968篇 |
1998年 | 787篇 |
1997年 | 624篇 |
1996年 | 480篇 |
1995年 | 419篇 |
1994年 | 383篇 |
1993年 | 354篇 |
1992年 | 271篇 |
1991年 | 196篇 |
1990年 | 116篇 |
1989年 | 144篇 |
1988年 | 94篇 |
1987年 | 55篇 |
1986年 | 49篇 |
1985年 | 32篇 |
1984年 | 27篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1954年 | 7篇 |
1877年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Gopal C. Kilambi Praveen Nagar N. Kameswara Rao 《Journal of Astrophysics and Astronomy》1992,13(2):175-194
Mid-ultraviolet and optical photometric analysis of helium stars are presented. A linear relation exists between the effective
temperature derived from model atmospheres and (1965-V)0 index. The effective temperatures derived from (1965-V)0 index are somewhat higher than that of MK spectral type estimates especially for late B-type helium objects. 相似文献
62.
Aimed at promoting regional coalitions and expanding the approach to economic links, this paper puts forward some new concepts
such as link intensity and receiving coefficient, expounds the indexes of quantitative analysis of economic links and establishes
the quantitative-analysis model of economic links. With help of the model, this paper calculates the values of the link intensities
between Su-Xi-Chang (Suzhou-Wuxi-Changzhou) region and Shanghai, and analyzes the regional difference of the economic links. 相似文献
63.
Luigi R. Bedin † Santi Cassisi Fiorella Castelli Giampaolo Piotto Jay Anderson Maurizio Salaris Yazan Momany Adriano Pietrinferni 《Monthly notices of the Royal Astronomical Society》2005,357(3):1038-1048
We propose a zero-point photometric calibration of the data from the Advanced Camera for Surveys (ACS) Wide Field Channel (WFC) on board the Hubble Space Telescope , based on a spectrum of Vega and the most up-to-date in-flight transmission curves of the camera. This calibration is accurate at the level of a few hundredths of a magnitude. The main purpose of this effort is to transform the entire set of evolutionary models into a simple observational photometric system for ACS/WFC data, and to make them available to the astronomical community. We provide the zero-points for the most used ACS/WFC bands, and give basic recipes for calibrating both the observed data and the models. We also present the colour–magnitude diagram from ACS data of five Galactic globular clusters, spanning the metallicity range −2.2 <[Fe/H] < −0.04 , and we provide fiducial points representing their sequences from several magnitudes below the turn-off to the red giant branch tip. The observed sequences are compared with the models in the newly defined photometric system. 相似文献
64.
Based on the Germany Koldwey Station's 1994-2003 conventional observation hourly data, this paper conducts a statistical analysis on the short-term climate characteristics for an arctic tundra region (Ny-(A)lesund island) where our first arctic expedition station (Huanghe Station) was located. Affected by the North Atlantic warming current, this area has a humid temperate climate, and the air temperature at Ny-(A)lesund rose above 0 ℃ even during deep winter season during our research period. The wind speed in this area was low and appeared most at southeast direction. We find that the temperature at Ny-(A)lesund rose in the faster rate (0.68 ℃/10 a) than those at the whole Arctic area. Compared with the floating ices where our expedition conducted in the Arctic, Ny-(A)lesund was warmer and more humid and had lower wind speed. Comparison of the near surface air temperature derived by NCEP/NCAR reanalysis to the conventional measurements conducted at the Koldwey site in Ny-(A)lesund area shows a good agreement for winter season and a significant difference for summer season. 相似文献
65.
Galileo系统及其在中国的应用 总被引:9,自引:0,他引:9
较详细地介绍了Galileo系统的全面体系结构、频率设计、服务内容及其广泛的应用范围,指出了它与GPS系统相比的优点,并对开发和增强Galileo系统在我国多层次、全方位的应用提出了建议。 相似文献
66.
EFFECT OF SULPHATE-REDUCING BACTERIA ON ELECTRO-CHEMICAL CORROSION BEHAVIOR OF 16Mn STEEL IN SEA MUD
INTRODUCTIONItwasgenerallyconsideredpreviouslythatthecorrosionofsteelinseamudwasnotserious.However,itwaslaterfoundthatthecorrosionrateofsteelinsomeseamudwashigherthanthatinseawater(King,1980;Sehmide,1982;Guoetal.,1997;Hou,1998).Therearesomereportsthatthecorrosionr… 相似文献
67.
68.
69.
INTRODUCTIONTheSubeiShoalandtheChangjiangRiverestuarineareainthewestoftheHuanghaiandEastChinaSeasisoneofthemarginalseasintheworld ,wheresuspendedmatterisextremelyhigh .Here ,notonlyistheretheTaiwanWarmCurrentoneoftheKuroshio’sbranchesintheEastChinaSea,butalsotheHuanghaiCoastalCurrent,andChangjiangDilutedWater.Sothestrongmixingbetweenthecoastalandoffshorewaterscomplicatessuspendedmatterdistributioninthisarea.HowthesuspendedmatterdischargedfromtheChangjiangRiverandtheabandonedHuan… 相似文献
70.
A coupled deterministic hydrological and water temperature model, CEQUEAU, was modified to include soil temperature and crown closure in its calculation of local advective terms in the heat budget. The modified model was than tested to verify its sensitivity to these modifications. An analysis of the heat budget of a small forested catchment in eastern Canada revealed that the advective term related to interflow plays a significant role in the daily water heat budget, providing on average 28% of the local advective budget (which also includes advective heat terms from surface runoff and groundwater) and nearly 14% of the total heat budget (which includes all radiative terms at the water surface, convection and evaporation, as well as the local advective terms). Relative sensitivity indices (RSIs) were used to verify the impact of the newly introduced parameters and variables. Among them, parameters related to the forest cover (crown closure and leaf area index) have a maximum RSI of ?0·6; i.e. a 100% increase in value produces a 60% decrease in the local advective term. Parameters with the greatest influence are the volume of water contributing to interflow and the amplitude of the net radiative flux at the soil surface, which, if doubled, would double the contribution of the local interflow advective term to the heat budget. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献