全文获取类型
收费全文 | 2819篇 |
免费 | 120篇 |
国内免费 | 35篇 |
专业分类
测绘学 | 101篇 |
大气科学 | 230篇 |
地球物理 | 659篇 |
地质学 | 904篇 |
海洋学 | 268篇 |
天文学 | 494篇 |
综合类 | 6篇 |
自然地理 | 312篇 |
出版年
2023年 | 12篇 |
2022年 | 8篇 |
2021年 | 47篇 |
2020年 | 57篇 |
2019年 | 75篇 |
2018年 | 82篇 |
2017年 | 88篇 |
2016年 | 114篇 |
2015年 | 91篇 |
2014年 | 94篇 |
2013年 | 185篇 |
2012年 | 109篇 |
2011年 | 158篇 |
2010年 | 132篇 |
2009年 | 169篇 |
2008年 | 133篇 |
2007年 | 127篇 |
2006年 | 135篇 |
2005年 | 103篇 |
2004年 | 114篇 |
2003年 | 93篇 |
2002年 | 70篇 |
2001年 | 68篇 |
2000年 | 61篇 |
1999年 | 44篇 |
1998年 | 50篇 |
1997年 | 33篇 |
1996年 | 35篇 |
1995年 | 27篇 |
1994年 | 30篇 |
1993年 | 21篇 |
1992年 | 34篇 |
1991年 | 21篇 |
1990年 | 28篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 21篇 |
1986年 | 15篇 |
1985年 | 29篇 |
1984年 | 24篇 |
1983年 | 31篇 |
1982年 | 27篇 |
1981年 | 24篇 |
1980年 | 14篇 |
1979年 | 16篇 |
1978年 | 18篇 |
1977年 | 15篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1972年 | 6篇 |
排序方式: 共有2974条查询结果,搜索用时 0 毫秒
111.
Keith D. Suter 《Marine Policy》1983,7(3):213-215
Disarmament has again become a major public concern in many nations. The main manifestations of this development have been demonstrations and marches and mass media attention to the possible consequences of a nuclear war. Less publicized has been governmental work, including that at the United Nations, in negotiating disarmament treaties. 相似文献
112.
113.
Variation in surface turbulence and the gas transfer velocity over a tidal cycle in a macro-tidal estuary 总被引:2,自引:0,他引:2
Christopher?J.?ZappaEmail author Peter?A.?Raymond Eugene?A.?Terray Wade?R.?McGillis 《Estuaries and Coasts》2003,26(6):1401-1415
The gradient flux technique, which measures the gas transfer velocity (k), and new observational techniques that probe turbulence in the aqueous surface boundary layers were conducted over a tidal
cycle in the Plum Island Sound, Massachusetts. Efforts were aimed at testing new methods in an estuarine system and to determine
if turbulence created by tidal velocity can be responsible for the short-term variability ink. Measurements were made during a low wind day, at a site with tidal excursions of 2.7 m and a range in tidal velocity of
nearly 1 m s−1. Estimates ofk using the gradient flux technique were made simultaneously with the Controlled Flux Technique (CFT), infrared imagery, and
high-resolution turbulence measurements, which measure the surface renewal rate, turbulent scales, and the turbulent dissipation
rate, respectively. All measurements were conducted from a small mobile catamaran that minimizes air- and water-side flow
distortions. Infrared imagery showed considerable variability in the turbulent scales that affect air-water gas exchange.
These measurements were consistent with variation in the surface renewal rate (range 0.02 to 2 s−1), the turbulent dissipation rate (range 10−7 to 10−5 W kg−1), andk (range 2.2 to 12.0 cm hr−1). During this low wind day, all variables were shown to correlate with tidal speed. Taken collectively our results indicate
the promise of these methods for determining short-term variability in gas transfer and near surface turbulence in estuaries
and demonstrate that turbulent transport associated with tidal velocity is a potentially important factor with respect to
gas exchange in coastal systems. 相似文献
114.
115.
Kristen E. K. Coppin Christopher J. Davis & Milena Micono 《Monthly notices of the Royal Astronomical Society》1998,301(1):L10-L14
We discuss the formation of spectral features in the decelerating ejecta of gamma-ray bursts, including the possible effect of inhomogeneities. These should lead to blueshifted and broadened absorption edges and resonant features, especially from H and He. An external neutral ISM could produce detectable H and He, as well as Fe X-ray absorption edges and lines. Hypernova scenarios may be diagnosed by Fe Kα and H Lyα emission lines. 相似文献
116.
117.
118.
Temperature estimates produced by a radiolarian-based transfer function, factor distributions of radiolarian assemblages, and variations in calcium carbonate were used to reconstruct the oceanographic conditions in the South Atlantic during the last glacial maximum (18,000 yr B.P.). This study suggests that while the position of the Subtropical Convergence at 18,000 yr B.P. was very similar to its present position, the Antarctic Polar Front shifted northward 1° to 3° of latitude in the eastern South Atlantic and 3° to 5° of latitude in the western South Atlantic. The largest temperature changes occurred in the subantarctic region and along the eastern portion of the Subtropical Gyre. 相似文献
119.
Jeffrey L. Bada E. Hoopes D. Darling Graham Dungworth Henk J. Kessels Keith A. Kvenvolden David J. Blunt 《Earth and Planetary Science Letters》1979,43(2):265-268
Enantiomeric measurements for aspartic acid, glutamic acid, and alanine in twenty-one different fossil bone samples have been carried out by three different laboratories using different analytical methods. These inter-laboratory comparisons demonstrate that D/L aspartic acid measurements are highly reproducible, whereas the enantiomeric measurements for the other amino acids show a wide variation between the three laboratories. At present, aspartic acid measurements are the most suitable for racemization dating of bone because of their superior analytical precision. 相似文献
120.
Keith C.C. Bancroft Susan B. Kendall Michael M. Rhead Gerard Hentic 《Marine pollution bulletin》1979,10(8):238-239
Hydrocarbon fractions in crude oil were separated by a new charge-transfer polymer in place of silver ions in Argentation TLC. The charge-transfer plates are cheaper than their silver nitrate equivalents, do not discolour, and store well. The polymer/silica gel mix can be re-used. 相似文献