全文获取类型
收费全文 | 2251篇 |
免费 | 77篇 |
国内免费 | 22篇 |
专业分类
测绘学 | 44篇 |
大气科学 | 169篇 |
地球物理 | 1031篇 |
地质学 | 594篇 |
海洋学 | 65篇 |
天文学 | 398篇 |
综合类 | 6篇 |
自然地理 | 43篇 |
出版年
2021年 | 27篇 |
2020年 | 29篇 |
2018年 | 59篇 |
2017年 | 78篇 |
2016年 | 104篇 |
2015年 | 78篇 |
2014年 | 101篇 |
2013年 | 114篇 |
2012年 | 53篇 |
2011年 | 71篇 |
2010年 | 88篇 |
2009年 | 78篇 |
2008年 | 69篇 |
2007年 | 61篇 |
2006年 | 39篇 |
2005年 | 24篇 |
2004年 | 33篇 |
2003年 | 39篇 |
2002年 | 47篇 |
2001年 | 30篇 |
2000年 | 36篇 |
1999年 | 25篇 |
1998年 | 42篇 |
1997年 | 24篇 |
1996年 | 47篇 |
1995年 | 27篇 |
1994年 | 32篇 |
1993年 | 43篇 |
1992年 | 35篇 |
1991年 | 30篇 |
1990年 | 37篇 |
1989年 | 27篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 36篇 |
1985年 | 19篇 |
1984年 | 35篇 |
1983年 | 31篇 |
1982年 | 35篇 |
1981年 | 26篇 |
1980年 | 23篇 |
1979年 | 39篇 |
1978年 | 30篇 |
1977年 | 26篇 |
1976年 | 19篇 |
1975年 | 22篇 |
1974年 | 26篇 |
1973年 | 26篇 |
1972年 | 27篇 |
1971年 | 29篇 |
排序方式: 共有2350条查询结果,搜索用时 15 毫秒
161.
Studia Geophysica et Geodaetica - 相似文献
162.
A. V. Shavrina N. S. Polosukhina J. Zverko V. Khalak V. V. Tsymbal J. Žižňovský 《Astronomy Reports》2001,45(10):784-796
The spectra of two roAp stars have been analyzed as part of a project to study lithium in magnetic Ap stars. Variability of the Li I 6708 Å resonance doublet and rare-earth lines was detected, which can be explained using an oblique rotator model with the lithium spots located at the magnetic poles. Synthetic spectra obtained at different rotational phases have yielded the first data on the atmospheric chemical compositions of these spotted stars. Using refined atomic data and the most complete line lists has enabled a detailed study of the spectra near the Li I 6708 Å line and computation of the Li I line profile taking into account the spotted distribution of the lithium over the stellar surfaces. The positions of two lithium spots and lithium abundances for each of the spots have been determined. 相似文献
163.
The Velenje area (almost 200 km2 with over 31,000 inhabitants) is based on the Šalek Valley, which became a leading area of industrialisation and urbanisation
after the Second World War, with consequent pollution problems. Various industrial plants polluted the river Paka while more
serious hazards arose through the coal mine which is a still causing landscape subsidence and the thermal power station in
the neighbourhood of Šoštanj which is a major source of sulphur dioxide and nitrogen oxide pollution. In 1987 there was an
ecological protest which marked the beginning of a sustainable development strategy for the community. During the past decade
programmes have dealt with the degradation of air, soil and water to achieve cleaner air, a transformation in landuse and
enhancement the river's formerly weak self-purifying capabilities. This article examines the changes in the valley since the
attention of the authorities was drawn to the deterioration of living conditions. Despite the pressures of transition which
have seen unemployment rising to over ten percent, significant environmental improvements have been made and the area stands
as a model for the rest of the country.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
164.
P. M. Nikolić S. Ðurić D. M. Todorović D. Vasiljević-Radović V. Blagojević P. Mihajlović J. Elazar K. T. Radulović A. I. Bojičić D. Urošević 《Physics and Chemistry of Minerals》2001,28(1):44-51
Electron transport properties of single crystal and polycrystalline natural mineral galena (PbS) samples from the Trep?a mine, Yugoslavia, were determined using the photoacoustic frequency transmission technique. Their thermal diffusivity (D T≈0.16 × 10?5 m2 s?1), the coefficient of diffusion (D between 0.15×10?2 0.16×10?2 m2 s?1) and lifetime of the excess carrier (τ≈35 μs and the front and rear recombination velocity (s g≈65.5 m s?1 and s b≈66.4 m s?1, respectively), were calculated by comparing the experimental results and the theoretical photoacoustic amplitude and phase signals. The lattice parameter obtained by X-ray work was a?=5.936?Å. The free carrier concentration of these single-crystal samples was measured using the Hall method (N?=?3×1018 cm?3). Measurements of the optical reflectivity of the same samples, as a function of wavelength, in the infrared and far infrared ranges, were performed. In the far infrared range a free electron plasma frequency was observed and numerically analyzed, using the least-squares fitting procedure. The values of optical parameters were calculated and the value of the free carrier concentration obtained by the Hall method was confirmed. 相似文献
165.
166.
Summary The structure of the surface-air temperature field in meso-alpha and meso-beta scale is studied for the purpose of regionalisation and for the optimum interpolation meso-analysis in Slovenia. The possibilities of subregionalisation, of the split into the horizontal and the vertical part of autocorrelation function and of separation according to the general weather type have been tested. It was found that the influence of weather type could not be introduced without the simultaneous introduction of first-guess fields for each weather type. The relative importance of first-guess field versus the importance of the type of autocorrelation function is estimated by several tests of the optimum interpolation meso analysis.With 6 Figures 相似文献
167.
Ivana Nemešová Nina Klimperová Radan Huth Jaroslava Kalvová 《Studia Geophysica et Geodaetica》1992,36(4):370-375
Summary The results of an objective weather categorization are presented. The 9 meteorological variables recorded daily during winter seasons of 1961–66 at Prague-Clementinum represent the input dataset. The principal component analysis and a few clustering procedures have been evaluated. 5 component solution and the average linkage clustering method were found optimal. The winter days have been grouped, according to their meteorological character, into 14 clusters. The warm categories represent 20% of the time and the cold categories less than 15% of the days. The mean maps of 1000 hPa and 500 hPa are shown for a few selected categories. Clustering techniques applied to long-time instrumental series can provide a better basis for attempting to detect temperature changes which have taken place over a long time span. 相似文献
168.
Summary Some errors of method occurring in A. C. measurements of the electrical conductivity of rocks are discussed. It is demonstrated that the difference between A.C. and D.C. conductivities, at given frequency, depends mostly on the magnitude of the D.C. conductivity and magnitude of the dielectric constant. 相似文献
169.
Summary Indirect phase reflection height measurements have been performed at the Panská Ves Observatory, Czechoslovakia, for 30 years to monitor solar flare effects (SFA). Only after introducing the new receiver in May 1985, could the indirect phase height analysis (IPHA) method be applied to measurements along the Allouis — Panská Ves 162 kHJ measuring path. The IPHA method allows the electron density and pressure variability in the lower ionosphere to be studied, particularly near the 80 km altitude. This paper describes the theoretical background of the IPHA method, the measuring equipment used at Panská Ves, the method of evaluating records and checking of data, and the program package developed by us both for graphic and numerical processing, as well as our efforts to develop a homogeneous East European IPHA network. The IPHA method has been introduced succesfully at the Panská Ves Observatory. 相似文献
170.
E. V. Bunkše 《GeoJournal》1992,26(2):203-209
The dominant element in Latvian culture is nature rather than history. Latvians are as bound to place, to landscape, to particular geographies, as other peoples are bound to tribal legends and religions. Incorporation of this Baltic land into the Soviet Union in 1940 occasioned dramatic conflicts between these deeply-rooted orientations to the concrete facts of nature and the abstract formulations of Marxism-Leninism. The nature culture of Latvia, celebrated in daina, folk arts and crafts, is the bedrock on which the current independence movement has been built. Two major challenges are being addressed: the overt political one between Moscow center and the Baltic republics, and a deep intellectual conflict between the closed ideology of Marxism-Leninism and the open-ended nature and place-oriented cultures of the Baltic peoples. 相似文献