全文获取类型
收费全文 | 456篇 |
免费 | 30篇 |
国内免费 | 55篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 61篇 |
地球物理 | 84篇 |
地质学 | 189篇 |
海洋学 | 69篇 |
天文学 | 92篇 |
综合类 | 7篇 |
自然地理 | 31篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 5篇 |
2017年 | 17篇 |
2016年 | 14篇 |
2015年 | 24篇 |
2014年 | 22篇 |
2013年 | 29篇 |
2012年 | 18篇 |
2011年 | 18篇 |
2010年 | 11篇 |
2009年 | 41篇 |
2008年 | 35篇 |
2007年 | 39篇 |
2006年 | 18篇 |
2005年 | 20篇 |
2004年 | 28篇 |
2003年 | 11篇 |
2002年 | 18篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1999年 | 15篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有541条查询结果,搜索用时 15 毫秒
311.
Xiong Ding-rong Zhang XiongZheng Yong-gang Huang Bang-rongMao Li-sheng Liu Wen-guang 《Chinese Astronomy and Astrophysics》2013
In this paper, we collect the redshift, bolometric luminosity, the full- width at half maximum of the Hβ emission line, the monochromatic luminosity at 5100 Å and the radio loudness for the sample of 117 quasars, including 20 radio-quiet quasars (RQQs) and 97 radio-loud quasars (RLQs). With the reverberation mapping method we calculate the black hole mass and Eddington ratio for this sample, as well as the radio luminosity from the total 5 GHz ?ux density. By analyzing the correlations among them, we obtain the following conclusions: (1) The black hole mass has weak correlations with the bolometric luminosity, radio loudness and radio luminosity for the RQQs, and has strong correlations with the bolometric luminosity, radio loudness and radio luminosity for the RLQs; (2) For the RQQs, the bolometric luminosity has weak correlations with the radio luminosity and 5 100 Å monochromatic luminosity, and for the RLQs, the bolometric luminosity has strong correlations with the radio luminosity and 5 100 Å monochromatic luminosity; (3) The RQQs and RLQs differ in the distributions of the black hole mass, emission line width and Eddington ratio. Based on these results, we suggest: the difference of emission line width between RQQs and RLQs is probably caused by the difference of black hole mass; the fundamental difference between RQQs and RLQs is caused by the difference of their intrinsic physical nature; the black hole mass, black hole spin, Eddington ratio, and host galaxy morphology are the important parameters to explain the origin of radio loudness and the double-peaked distribution; and the radio jet is closely related with the accretion rate of disk. 相似文献
312.
313.
Quasinormal modes of a black hole with quintessence-like matter and a deficit solid angle: scalar and gravitational perturbations 总被引:1,自引:0,他引:1
Ping Xi 《Astrophysics and Space Science》2009,321(1):47-51
In the previous paper (Li et al. in Phys. Lett. B 666:125–130, 2008), we show the solutions of Einstein equations with static spherically-symmetric quintessence-like matter surrounding a global
monopole. Furthermore, this monopole become a black hole with quintessence-like matter and a deficit solid angle when it is
swallowed by an ordinary black hole. We study its quasinormal modes by WKB method in this paper. The numerical results show
that both the real part of the quasinormal frequencies and the imaginary part decrease as the state parameter w, for scalar and gravitational perturbations. And we also show variations of quasinormal frequencies of scalar and gravitational
fields via different ε (deficit solid angel parameter) and different ρ
0 (density of static spherically-symmetric quintessence-like matter at r=1), respectively. 相似文献
314.
315.
Matts Lindbladh W. Wyatt Oswald David R. Foster Edward K. Faison Juzhi Hou Yongsong Huang 《Quaternary Research》2007,67(3):502-508
Picea is an important taxon in late-glacial pollen records from eastern North America, but little is known about which species of Picea were present. We apply a recently developed palynological method for discriminating the three Picea species in eastern North America to three records from New England. Picea glauca was dominant at 14,500–14,000 cal yr BP, followed by a transition to Picea mariana between 14,000 and 13,500 cal yr BP. Comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the Younger Dryas Chronozone. The ecological changes of the late-glacial interval were not a simple oscillation in the position of a single species' range, but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors, including climate, edaphic conditions, and atmospheric CO2 levels. 相似文献
316.
黑鲷的营养需要及配合饲料研究 总被引:9,自引:0,他引:9
本文论述了黑鲷饲料中最适蛋白质含量及动,植物蛋白比例的有关研究,黑鲷对于饲料中磷的需要量及钙磷化,黑鲷饲料中必需氨基酸添加的必要性,在此基础上,制成黑鲷配合饲料并与冰冻玉筋鱼进行了比较养殖试验,取得较好的结果。 相似文献
317.
J. S. Ulvestad 《New Astronomy Reviews》1999,43(8-10)
Supermassive black holes, with masses of 106 M to more than 109 M, are among the most spectacular objects in the Universe, and are laboratories for physics in extreme conditions. The primary goal of ARISE (Advanced Radio Interferometry between Space and Earth) is to use the technique of Space VLBI to increase our understanding of black holes and their environments, by imaging the havoc produced in the near vicinity of the black holes by their enormous gravitational fields. The mission will be based on a 25-meter space-borne radio telescope operating at frequencies between 8 and 86 GHz, roughly equivalent to an orbiting element of the Very Long Baseline Array. In an elliptical orbit with an apogee height of 40 000–100 000 km, ARISE will provide a resolution of 15 microarcsecond or better, 5–10 times better than that achievable on the ground. At frequencies of 43 and 86 GHz, the resolution of light weeks to light months in distant quasars will complement the gamma-ray and X-ray observations of high-energy photons, which come from the same regions near the massive black holes. At 22 GHz, ARISE will image the H2O maser disks in active galaxies more than 15 Mpc from Earth, probing accretion physics and giving accurate measurements of black-hole masses. ARISE also will study gravitational lenses at resolutions of tens of microarcseconds, yielding important information on the dark-matter distribution and on the possible existence of compact objects with masses of 103 M to 106 M. 相似文献
318.
天津夏季大气消光性质的研究 总被引:2,自引:0,他引:2
利用2010年夏季天津城市边界层观测站颗粒物、黑碳气溶胶、氮氧化物(NOX)浓度、地面能见度和气象梯度观测资料,分析了天津夏季大气消光特性及低能见度事件产生的原因。结果表明,天津夏季主要污染物为PM10和PM2.5,大气气溶胶消光系数为529.06M.m-1,其中,吸收系数为50.17M.m-1,散射系数为478.89M.m-1,气体吸收系数为7.74M.m-1,气溶胶单次散射反射率为0.87。天津夏季边界层大气状态有近一半的时间为中性或偏稳定层结,当出现中性或偏稳定层结大气时则有接近一半的情况出现低能见度事件(能见度<5km),影响人们的日常生活。 相似文献
319.
More than 100 new heat flow measurements have been collected in recent years (2002–2004) in different tectonic environments
of the northern Black Sea. The northern periphery of the Black Sea is characterized by strong geodynamic and seismic activity,
high sedimentation rates, diapiric structures, mud volcanism, and fluid and gas escape at the sea floor. We present new thermal
data from the shelf, continental slope and deep-water basin, measured off-shore using a marine thermo-probe and on-shore in
drill holes. Heat flow density ranges from 20 to more than 2,000 mW/m2. For two local areas (the Dnieper gas seeps and the Dvurechenski mud volcano area), we discuss the relation between heat
flow variability and the geological and physical processes in the near-bottom sediment layer. The Dnieper gas seeps area is
characterized by strong small-scale heat flow variability and is controlled by fluid and gas migration. In the Dvurechenski
active mud volcano, the near-bottom temperature in sediments is anomalously elevated because additional heat is carried out
by mass flows of fluids and clay minerals. Away from the mud volcano heat flow quickly decreases to background values. 相似文献
320.