全文获取类型
收费全文 | 2084篇 |
免费 | 50篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 51篇 |
大气科学 | 96篇 |
地球物理 | 1112篇 |
地质学 | 457篇 |
海洋学 | 24篇 |
天文学 | 349篇 |
综合类 | 3篇 |
自然地理 | 46篇 |
出版年
2021年 | 25篇 |
2020年 | 26篇 |
2019年 | 22篇 |
2018年 | 44篇 |
2017年 | 59篇 |
2016年 | 68篇 |
2015年 | 67篇 |
2014年 | 72篇 |
2013年 | 77篇 |
2012年 | 39篇 |
2011年 | 53篇 |
2010年 | 61篇 |
2009年 | 62篇 |
2008年 | 51篇 |
2007年 | 54篇 |
2006年 | 52篇 |
2005年 | 27篇 |
2004年 | 33篇 |
2003年 | 34篇 |
2002年 | 39篇 |
2001年 | 34篇 |
2000年 | 27篇 |
1999年 | 25篇 |
1998年 | 33篇 |
1996年 | 39篇 |
1995年 | 23篇 |
1994年 | 31篇 |
1993年 | 29篇 |
1992年 | 29篇 |
1991年 | 43篇 |
1990年 | 26篇 |
1989年 | 49篇 |
1988年 | 34篇 |
1987年 | 39篇 |
1986年 | 38篇 |
1985年 | 27篇 |
1984年 | 33篇 |
1983年 | 35篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 31篇 |
1979年 | 42篇 |
1978年 | 37篇 |
1977年 | 28篇 |
1976年 | 22篇 |
1975年 | 25篇 |
1974年 | 31篇 |
1973年 | 28篇 |
1972年 | 27篇 |
1971年 | 29篇 |
排序方式: 共有2138条查询结果,搜索用时 0 毫秒
101.
Karel Prikner Jaroslav Střeštík Karel Dobeš Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1972,16(3):262-270
Summary The spectral analysis of samples of beating-type pc3 pulsations, recorded at the Budkov Observatory during the summer months of 1968 and 1969 was carried out in the frequency interval10 mHz100 mHz. The average limits of the pulsation frequency range are roughly20 mHz60 mHz. The centre of the occurrence frequency graphs for both components is at the frequency fg 41 mHz. The analysis of three separated daily intervals showed a very slight tendency to a systematic decrease in the frequency of the centre from the morning to the afternoon. The study of the sense of rotation of the pulsation disturbance vector in the (X, Y)-plane showed an overall predominancy of L over R-types during daytime, particularly during the morning. 相似文献
102.
103.
Vladimír Kropáček Miroslav Krs Reviewer V. Bucha 《Studia Geophysica et Geodaetica》1975,19(3):261-274
Summary The paper is devoted to the study of the magnetic properties, of the volume magnetic susceptibility in a weak magnetic field, of the specific magnetic susceptibility in a strong magnetic field, of natural remanent magnetization and its stability in A.C. fields, and of the temperature dependence of magnetic susceptibility of natural Mn-oxides. Samples of pyrolusite, polianite, manganite, hausmannite, psilomelan and wad from different localities all over the world were studied; the measured values are statistically treated so that the given values are valid in general. Hausmannite displayed typical values of the magnetic susceptibility, different from the values of the other Mn-oxides. In general, many natural Mn-oxides contain heterogeneous admixtures of Fe-oxides, which are responsible for their ferromagnetic properties. A high degree of magnetic hardness, predetermining the minerals for palaeomagnetic research, was proved with many of the natural Mn-oxides. 相似文献
104.
105.
106.
Milan Burša 《Studia Geophysica et Geodaetica》1970,14(1):1-9
Résumé De l'ensemble des coefficients harmoniques du développement du géopotentiel [3, 6, 7], calculé à partir des variations des
éléments orbitaux des satellites, on a calculé les paramètres de l'ellipso?de terrestre triaxial, représentant la surface
du géo?de. La solution fut effectuée par méthode analytique sous la condition du minimum de l'intégrale du carré de l'écart
du rayon vecteur du géo?de et de l'ellipso?de, de même que par calcul numérique à partir des valeurs discrètes 10°×10°.
Address: Politickych vězňů 12, Praha 1-Nové Město. 相似文献
Address: Politickych vězňů 12, Praha 1-Nové Město. 相似文献
107.
Milan Burša 《Studia Geophysica et Geodaetica》1970,14(3):274-285
Summary This paper ties up with [5, 6] the fundamental notations of which have been adopted. The sets of Stokes' constants (harmonic
coefficients) J
n
(k)
, S
n
(k)
were adopted from [4], and the scale factor for lengths, R0=GM/W0, from [5]. The equations for global meridional and parallel sections of the geoid surface W=W0 are formulated. The geoid sections are represented by best fitting ellipses, as regards the meridians always for the arcs
between the equator and the pole.
Address: Politickych vězňů 12, Praha 1-Nové Město. 相似文献
108.
M. Vochozka A. Maroušková J. Váchal J. Straková 《International Journal of Environmental Science and Technology》2016,13(6):1607-1614
A positive energy balance caused by accelerated production of CH4 and additional financial benefits associated with shorter retention times, reduction in volumes, easier dewatering, enhanced hygiene, etc., are the reasons why most modern wastewater treatment plants are newly equipped with hydrothermal pretreatment units. This study examined how the changes in composition of the pretreated sewage sludge fermentation residues manifested themselves in subsequent processing by pyrolysis, both in terms of technology and financial impacts. It has been found that concentrations of heavy metals and other hazardous inhibitors might increase; however, the overall biotoxicity is lower due to their immobilization in the charred mass. Moreover, charring of the fermentation residues results in significant financial as well as technological benefits. 相似文献
109.
Surfaces of phosphorite nodules and pebbles from the “Cambridge Green Sand” (Cenomanian, South England) yielded several discernible types of scratches. These originated before the burial of nodules/pebbles as evidenced by fossil epibiotic oysters cemented to cover the scratches. The individual forms of scratches differ in size and shape; therefore, the set of “scratching instruments” also had to be different. The scratches described differ from scratches generated by glacial processes, namely by the regularity of length and intervals, parallel orientation, existence of recurrent forms and placement along the nodule edges. We interpret the scratches as trace fossils of the ichnogenus Machichnus. Three new species, namely M. normani, M. harlandi and M. jeansi, are erected for them herein. The series of scratches originated probably by teeth on a couple of jaws; the makers possibly scraped bacterial or algal film off the surface of nodules that were covered with the phosphate gel. Both homodont and heterodont animals (probably fish) were involved. 相似文献
110.
Dušan Polomčić Bojan Hajdin Zoran Stevanović Dragoljub Bajić Katarina Hajdin 《Hydrogeology Journal》2013,21(7):1519-1530
The Vi? Bare groundwater source is used to supply water to the population and industry of Obrenovac, one of the municipalities of Belgrade (the capital of Serbia). It is a typical riverbank filtration site; exploitation is performed through 30 drilled wells and two radial wells located in the meander of the Sava River. The established hydraulic connection between the river and tapped aquifer is so great that the river regime has a dominant influence on the aquifer. As a consequence of this, water-delivery reduction occurs in the dry months (summer–autumn), when the population needs water the most. Based on the data associated with the river’s gauges, precipitation, quantity of pumped water and groundwater-level fluctuation, a simulation of the groundwater regime for non-steady-state flow conditions has been undertaken through a numerical model. To overcome problems of water shortage during the dry season, the possibility of artificial recharge using an infiltration channel, made up of two connected parts, was analyzed. During the dry months, 80 % of the wells receive water partly from the infiltration channel. In this way, possibilities for extracting additional water are created. The application of this concept is discussed. 相似文献