全文获取类型
收费全文 | 18906篇 |
免费 | 3711篇 |
国内免费 | 4919篇 |
专业分类
测绘学 | 1493篇 |
大气科学 | 3795篇 |
地球物理 | 4691篇 |
地质学 | 10003篇 |
海洋学 | 2445篇 |
天文学 | 673篇 |
综合类 | 1901篇 |
自然地理 | 2535篇 |
出版年
2024年 | 72篇 |
2023年 | 363篇 |
2022年 | 1019篇 |
2021年 | 1119篇 |
2020年 | 999篇 |
2019年 | 1046篇 |
2018年 | 1235篇 |
2017年 | 1055篇 |
2016年 | 1160篇 |
2015年 | 1042篇 |
2014年 | 1256篇 |
2013年 | 1237篇 |
2012年 | 1211篇 |
2011年 | 1238篇 |
2010年 | 1237篇 |
2009年 | 1100篇 |
2008年 | 1001篇 |
2007年 | 883篇 |
2006年 | 754篇 |
2005年 | 695篇 |
2004年 | 571篇 |
2003年 | 541篇 |
2002年 | 612篇 |
2001年 | 621篇 |
2000年 | 588篇 |
1999年 | 741篇 |
1998年 | 591篇 |
1997年 | 547篇 |
1996年 | 522篇 |
1995年 | 428篇 |
1994年 | 409篇 |
1993年 | 347篇 |
1992年 | 301篇 |
1991年 | 200篇 |
1990年 | 165篇 |
1989年 | 141篇 |
1988年 | 108篇 |
1987年 | 76篇 |
1986年 | 58篇 |
1985年 | 53篇 |
1984年 | 35篇 |
1983年 | 34篇 |
1982年 | 28篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1958年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
Andrei V. Ivanov Nataliya N. Kononkova S. Vincent Yang Michael E. Zolensky 《Meteoritics & planetary science》2003,38(5):725-737
Abstract— Clasts of alkaline (the second find in meteorites) and subalkaline rocks were found in the Kaidun meteorite. One of them (#d4A) is a large crystal of albite with inclusions of fluorapatite, arfvedsonite, aenigmatite, and wilkinsonite. The two latter minerals were previously unknown in meteorites. Another clast (#d[3–5]D) has a melt crystallization texture of mainly feldspar (oligoclase) composition and contains relict grains of both high‐Ca and low‐Ca pyroxene and fluorapatite. The mineralogical characteristics of these clasts suggest a genetic relationship and an origin from the same parent body. The textural and mineralogical characteristics of the clasts indicate origin by extensive igneous differentiation. Such processes most likely took place in a rather large differentiated body. The material of clast #d(3–5)D is similar in some mineralogical respects to basaltic shergottites. 相似文献
72.
本文通过对成都10个重污染日进行天气学分析,将污染浓度与气象要素进行聚类、研究了重污染日形成原因及污染浓度与气象要素的关系。在此基础上,建立了SO_2、TSP日平均浓度分级预报方程。 相似文献
73.
网络经济已成为新的社会生产力的代表。广西地质矿产勘查开发局应该利用其行业和地域方面的固有优势,积极参与网络经济,以期打开矿业市场。文章提出了建立矿业网站的设想和框架。 相似文献
74.
利用三维有限元模拟两层地球模型(包括弹性层和粘弹性层)介质的横向不均匀和断层错动的复杂性对震后地表位移场的影响,其数值结果包括弹性解和粘弹性解。结果表明,震后位移场的分布特征不仅与粘弹性层的流变特性有关,还与弹性层介质的剪切模量以及断层的同震错动有关。 相似文献
75.
Qing-Yao Liu Yu-Lan Yang National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 《中国天文和天体物理学报》2006,6(3):331-337
The variation in the orbital period of the W UMa type contact binary V502 Oph is analyzed. The orbital period exhibits a wavelike variation with a periodicity of 23.0 years and an amplitude of △P = 1.24×10~(-6) days superimposed on secular decrease of dP/dt = 1.68×10-7 day per year. The long-term decrease may be accompanied by the contraction of the secondary at a rate of 83 m per year and a mass transfer rate from the primary to the secondary of 4.28×10~8 M per year. The short-term oscillation may be explained by the presence of a third component. Orbital elements of the third body and its possible mass are presented. 相似文献
76.
The new polyenzyme method for making gravy fromHarengula zunasi offal involves protein enzymolysis with flavorase after proper alkaline and neutral protease levels were established by orthogonal
trials to select the best hydrolytic conditions for processing offal with alkaline and neutral protease. The conditions for
the polyenzyme method were pH of 7.0, temperature of 50°C, alkaline and neutral protease concentration of 1.5% respectively,
hydrolysis time of 120 min, and flavorase concentration of 2.0%, for 60 min. The new gravy-making technology yields a nutritious
and delicious gravy containing 40.3% of total essential amino acids, with delicious amino acids Glu, Asp, Gly, Ala, Pro and
Ser comprising 49.5%, total and amino nitrogen being respectively 1.9 and 1.1 g/100 g (amino acid nitrogen being 61.0% of
total nitrogen), The polyenzyme method was used to make 14.8% protein gravy fromHarengula zunasi offal. In addition, inorganic elements, the phosphorus content is the highest.
This project was aided financially by the Guangdong Science and Technology Office (No. 2KM06002S). 相似文献
77.
78.
利用上海天文台的照相底片资料,确定了疏散星团NGC6530天区364颗恒星的自行和成员概率,并对有关自行测定的方法、结果和精度等问题作了较为详细的介绍和讨论。使用的底片历元差为87年,全部恒星自行中误差的均方根值为1.09mas/a。 相似文献
79.
The pyroxenite xenoliths in the volcanic rocks of Hoh Xil consist of clinopyroxenes and orthopyroxenes. The mineral composition of these pyroxenes is similar to that of mantle xenoliths including peridotite and pyroxenite from China and abroad, and different from that of granulites. The pyroxenes formed at 1101–1400°C (averaging 1250°C) and under 30–60 kb (averaging 46 kb). We deduced that the magma was derived from the mantle at a depth of more than 150 km, which fits in with the geophysical conclusion that the low-velocity layer existed in the mantle under 150 km.
相似文献80.
We study a model of mergers affecting only the progenitors of present E/SO. We adopt the standard scenarios of star formation as prescribed by Guiderdoni & Rocca-Volmerange. The merging process is parametrized under the assumptions of(1) self-similarity of the Schechter MF and(2) mass conservation. Nine models are discussed. The predictions are compared with counts ofB
J
,U
+,F
+,N
+ bands. E/SO mergers account for the excess of the faintest blue galaxies without causing excess in redder bands. However, as we no longer have enough mergers at brighter magnitudes, a plain E/SO merging model fits less tightly for the redshift and the colour distributions. Detection effect, a steeper slope of LF may be ways to improve. Our models predict acceptable merger frequencies atz = 0.5 although some models predict more interacting galaxies than observation atz = 0. 相似文献