全文获取类型
收费全文 | 6486篇 |
免费 | 332篇 |
国内免费 | 27篇 |
专业分类
测绘学 | 208篇 |
大气科学 | 586篇 |
地球物理 | 2280篇 |
地质学 | 2290篇 |
海洋学 | 266篇 |
天文学 | 897篇 |
综合类 | 25篇 |
自然地理 | 293篇 |
出版年
2022年 | 39篇 |
2021年 | 132篇 |
2020年 | 114篇 |
2019年 | 84篇 |
2018年 | 284篇 |
2017年 | 261篇 |
2016年 | 398篇 |
2015年 | 302篇 |
2014年 | 348篇 |
2013年 | 466篇 |
2012年 | 312篇 |
2011年 | 314篇 |
2010年 | 294篇 |
2009年 | 272篇 |
2008年 | 228篇 |
2007年 | 207篇 |
2006年 | 200篇 |
2005年 | 140篇 |
2004年 | 131篇 |
2003年 | 119篇 |
2002年 | 112篇 |
2001年 | 122篇 |
2000年 | 81篇 |
1999年 | 76篇 |
1998年 | 98篇 |
1997年 | 85篇 |
1996年 | 58篇 |
1995年 | 64篇 |
1994年 | 68篇 |
1993年 | 60篇 |
1992年 | 56篇 |
1991年 | 59篇 |
1990年 | 73篇 |
1989年 | 49篇 |
1988年 | 39篇 |
1987年 | 43篇 |
1986年 | 51篇 |
1984年 | 45篇 |
1983年 | 53篇 |
1982年 | 45篇 |
1981年 | 43篇 |
1980年 | 40篇 |
1979年 | 43篇 |
1978年 | 43篇 |
1977年 | 44篇 |
1976年 | 39篇 |
1975年 | 40篇 |
1974年 | 46篇 |
1973年 | 52篇 |
1971年 | 50篇 |
排序方式: 共有6845条查询结果,搜索用时 93 毫秒
961.
Outdoor domestic water use is often targeted by demand management strategies. However, despite a rich empirical evidence base coming from primary studies, it is still unclear how factors that influence this type of demand interact and which are the most suitable to be addressed by water conservation programs. Based on 423 scientific contributions, we develop a research synthesis combining a variety of techniques to create a theoretical model of the relationships among factors most consistently observed in the literature. The findings uncover a great degree of complexity in terms of interactions between spatial-structural, social-structural, and cultural and psychological factors at different scales. For researchers, the methodology and the outcomes can be useful to better frame existing and future research within the literature on the topic. In practice, the adaptation of the theoretical model to local specificities can facilitate the design of more efficient and integrated demand management strategies. 相似文献
962.
I. Díaz-Reviriego Á. Fernández-Llamazares P. L. Howard J. L. Molina V. Reyes-García 《社会与自然资源》2017,30(6):690-706
We employ social network analysis (SNA) to describe the structure of subsistence fishing social networks and to explore the relation between fishers’ emic perceptions of fishing expertise and their position in networks. Participant observation and quantitative methods were employed among the Tsimane’ Amerindians of the Bolivian Amazon. A multiple-regression quadratic assignment procedure was used to explore the extent to which gender, kinship, and age homophilies influence the formation of fishing networks. Logistic regressions were performed to determine the association between fishers’ expertise, their sociodemographic identities, and network centrality. We found that fishing networks are gendered and that there is a positive association between fishers’ expertise and centrality in networks, an association that is more striking for women than for men. We propose that a social network perspective broadens understanding of the relations that shape the intracultural distribution of fishing expertise, as well as natural resource access and use. 相似文献
963.
Laštovička Jan Burešová Dalia Boška Josef Bremer Jurgen Märcz Ferenc 《Studia Geophysica et Geodaetica》1997,41(2):171-180
Data from four A3 radio wave circuits in central Europe are used to analyse the representativeness of the ionization and gravity wave activity pattern in the lower ionosphere (85 – 100 km) in the CRISTA experiment interval (3 – 12 November 1994) for the given conditions. It has been found that the CRISTA experiment interval was run under conditions, which are highly representative both of October – November 1994 and autumn, low-moderate solar activity, the descending phase of solar cycle conditions, i.e. CRISTA measurements may be considered to provide values identical with, or close to climatological values (at least for central Europe, h = 85 – 100 km). 相似文献
964.
965.
C. Íbanoğlu E.R. Pekünlü V. Keskín Z. Tunca S. Evren M.C. Akan A. Devlen 《Astrophysics and Space Science》1997,257(1):83-94
The light curves, obtained by the authors of the present paper during the period 1978–1992, of the chromospherically active binary system RT Lac were examined. The average (B–V) colour indices were obtained and corrected for the interstellar extinction. Spectroscopic studies indicate that the less massive component may be taken as G8. The light curve analysis indicates that the less massive, larger component fills its corresponding Roche lobe. Both photometric and spectroscopic observations compel one to draw a conclusion that circumstellar matter does exist around the binary system. A colour excess caused by this matter is found to be 0.278 for B–V colour at mid–secondary eclipse. On the basis of photometric colour indices alone, the components of RT Lac are classified as G3–4 and G8. If we use the observed radial velocities of the less massive subgiant star from Ca II emission lines and from other optical lines we find for the mass of the more massive component as 1.34–1.70 M. This mass range corresponds to the main sequence late F stars. The common envelope hypothesis and mass function and also blending of the spectral lines of more massive component point out that it should be at most a late F type main sequence star. 相似文献
966.
967.
H. Steinhäußer 《Theoretical and Applied Climatology》1950,2(1-2):129-133
Zusammenfassung Aus den Monatsberichten einiger hydrographischer Stationen der Ostalpen in verschiedenen Höhenlagen wird bestimmt, welche Niederschlagsmengen 1 cm der gemessenen Neuschneehöhen entsprechen, im Monats- und im Jahresmittel. In Abhängigkeit von der Höhenlage weist die Niederschlagsmenge pro Zentimeter Neuschneehöhe ein ausgeprägtes Minimum bei 1350 m Seehöhe auf. Durch Multiplikation des der Seehöhe entsprechenden Wertes dieser Kurve mit der an einer Station der Ostalpen gemessenen Neuschneehöhe der Periode 1896/97–1915/16 erhält man den Schneeanteil dieser Station am Gesamtniederschlag. Die auf diese Art bestimmten Anteilmengen sind in der Regel dann größer bzw. kleiner als die nachV. Conrad berechneten Werte, wenn die Anomalien der jährlichen Neuschneehöhen nachE. Ekhart positiv bzw. negativ sind.
Mit 2 Textabbildungen. 相似文献
Summary On the base of monthly reports of several hydrographic stations in the Eastern Alps, the amounts of precipitation corresponding to 1 cm of fresh snow-depth have been calculated in the monthly and yearly average. As a function of the altitude the amount of precipitation per cm fresh snow-depth shows a marked minimum at the altitude of 1350 m. By multiplication of the fresh snow-depths, measured at a station of the Eastern Alps during the period 1896/97–1915/16, with the corresponding value of the above curve the snow fraction of the total precipitation of this station can be obtained. As a rule, the fractions determined in this way are greater or smaller than those calculated byV. Conrad according as the anomalies of the yearly fresh snow-depths given byE. Ekhart are respectively positive or negative.
Résumé On calcule la quantité d'eau météorique correspondant à 1 cm. de neige fraîche (moyennes mensuelles et annuelles) sur la base des rapports mensuels de quelques stations hydrographiques des Alpes orientales. Cette quantité, considérée en fonction de l'altitude, présente un minimum net vers 1350 m. En multipliant la valeur correspondant à l'altitude d'une station des Alpes orientales où furent mesurées les hauteurs de neige fraîche pendant la période 1896/97 à 1915/16 par cette hauteur même, on obtient la fraction en neige des précipitations totales en ce point. Les fractions ainsi calculées sont dans la règle plus grandes ou plus petites que les valeurs établies parV. Conrad selon que les anomalies des hauteurs annuelles de neige fraîche, d'aprèsE. Ekhart, sont respectivement positives ou négatives.
Mit 2 Textabbildungen. 相似文献
968.
Dr. med G. Huber-Pestalozzi Hans Wolfgang Schäfer 《Aquatic Sciences - Research Across Boundaries》1951,13(1):192-196
Ohne Zusammenfassung 相似文献
969.
Esa Hyyppä 《International Journal of Earth Sciences》1942,32(4-5):595-611
Ohne Zusammenfassung 相似文献
970.