全文获取类型
收费全文 | 8194篇 |
免费 | 1355篇 |
国内免费 | 2309篇 |
专业分类
测绘学 | 90篇 |
大气科学 | 240篇 |
地球物理 | 614篇 |
地质学 | 7448篇 |
海洋学 | 358篇 |
天文学 | 2297篇 |
综合类 | 412篇 |
自然地理 | 399篇 |
出版年
2024年 | 29篇 |
2023年 | 79篇 |
2022年 | 197篇 |
2021年 | 223篇 |
2020年 | 222篇 |
2019年 | 264篇 |
2018年 | 230篇 |
2017年 | 208篇 |
2016年 | 258篇 |
2015年 | 325篇 |
2014年 | 454篇 |
2013年 | 395篇 |
2012年 | 468篇 |
2011年 | 521篇 |
2010年 | 441篇 |
2009年 | 687篇 |
2008年 | 620篇 |
2007年 | 691篇 |
2006年 | 698篇 |
2005年 | 594篇 |
2004年 | 590篇 |
2003年 | 555篇 |
2002年 | 456篇 |
2001年 | 432篇 |
2000年 | 379篇 |
1999年 | 391篇 |
1998年 | 352篇 |
1997年 | 228篇 |
1996年 | 153篇 |
1995年 | 139篇 |
1994年 | 105篇 |
1993年 | 95篇 |
1992年 | 108篇 |
1991年 | 53篇 |
1990年 | 54篇 |
1989年 | 55篇 |
1988年 | 31篇 |
1987年 | 21篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
61.
Stellar population synthesis at the resolution of 2003 总被引:2,自引:0,他引:2
62.
基于统一强度理论的地基临界荷载公式 总被引:1,自引:0,他引:1
基于统一强度理论,按照临界荷载公式的推导方法,得到地基临界荷载的统一解公式。Mohr-Coulomb强度理论计算的结果为其特例。把计算结果与《建筑地基基础设计规范》中的结果进行了对比分析,认为当不同程度地考虑中间主应力σ2的影响时,可以有效地发挥地基的强度潜能。并通过实例计算了统一强度理论参数b取不同值时地基承载力特征值,并进行了对比分析。 相似文献
63.
64.
In this paper we show that a change in the signs of some of the metric components of the solution of the field equations for
the classical cosmic string results in a solution which we interpret as a time-dependent wall composed of tachyons. We show
that the walls have the property of focusing the paths of particles which pass through them. As an illustration of this focusing,
we demonstrate the results of a simple simulation of the interaction between one such tachyon wall and a rotating disk of
point masses. This interaction leads to the temporary formation of spiral structures. These spiral structures exist for a
time on the order of one galactic rotation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
65.
Guinevere Kauffmann Timothy M. Heckman Simon D. M. White Stéphane Charlot Christy Tremonti Jarle Brinchmann Gustavo Bruzual Eric W. Peng Mark Seibert Mariangela Bernardi Michael Blanton Jon Brinkmann Francisco Castander Istvan Csábai Masataka Fukugita Zeljko Ivezic Jeffrey A. Munn Robert C. Nichol Nikhil Padmanabhan Aniruddha R. Thakar David H. Weinberg Donald York 《Monthly notices of the Royal Astronomical Society》2003,341(1):33-53
66.
Late Cretaceous-Paleogene Palynostratigraphy from the Arkhara-Boguchan Brown Coal Mine of Zeya-Bureya Depression, Russia 总被引:1,自引:1,他引:0
Tatyana V. Kezina 《东北亚地学研究》2003,(2)
1IntroductionThe Arkhara-Boguchan brown coal mine is lo-cated in the western Arkhara depression,southeast-ern part of the Zea-Bureya Basin (Fig.1). Late Creta-ceous-Paleogene coal-bearing strata are well out-cropped at the Arkhara-Boguchan quarry. It contains four coal-bearing beds (in descending order): “Ve-likan”, “Promezhutochny”,“Dvoinoy”and “Nyzhny”, and composed of three sedimentary cycles (Fig.2). The lower cycle can be divided into two sub-cycles:the lowest sub-cycle is … 相似文献
67.
The present-day chemical and dynamical properties of the Milky Way are signatures of the Galaxy's formation and evolution.
Using a self consistent chemodynamical evolution code we examine these properties within the currently favoured paradigm for
galaxy formation – hierarchical clustering within a CDM cosmology. Our Tree N-body/Smoothed Particle Hydrodynamics code includes
a self-consistent treatment of gravity, hydrodynamics, radiative cooling, star formation, supernova feedback and chemical
enrichment. Two models are described which explore the role of small-scale density perturbations in driving the evolution
of structure within the Milky Way. The relationship between metallicity and kinematics of halo stars are quantified and the
implications for galaxy formation discussed. While high-eccentricity halo stars have previously been considered a signature
of `rapid collapse', we suggest that many such stars may have come from recently accreted satellites.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
68.
Zhang Qing Wang Li-fan Hu Jing-yao P. A. Mazzali Wang Zhen-ru 《Chinese Astronomy and Astrophysics》1995,19(4):426-431
We present the modeling of the ultraviolet and optical spectra obtained simultaneously on 1993 April 15 with the HST and at Lick Observatory. A Monte Carlo code is employed in the modeling and a comparison is made between models reported by different groups. With an atmosphere similar to the Sun in chemical composition, the observed spectral lines are well reproduced by a power law density structure of index around 20 except the strong H and HeI λ5876 lines which have peculiar absorption profiles. The photospheric velocity is found to be 9500 km/s and the blackbody temperature of the spectrum is 7990 K. For H and HeI λ5876, we suggest a two-component density structure which has a smoother layer located immediately outside the steeply decreasing inner envelope. The power law indices are most probably 20 and 3, respectively, with the transition point at about 13 000 km/s. In addition, this outer smooth layer serves to flatten the far UV spectrum as observed. 相似文献
69.
70.