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961.
干旱区城镇发展的理论探讨:以新疆为例 总被引:1,自引:0,他引:1
本文在实际调查的基础上,通过专家意见咨询与定量方法的结合,探讨了干旱区城镇发展的一般规律:a.经济发展水平仍是干旱区城镇发展的渊源;b.水资源是干旱区域镇发展的限制性因子,但并不能解释干旱区城镇发展一般的规律性;c.应重视科技水平对城市发展的重要作用。 相似文献
962.
963.
Distribution and formation of high-fluorine groundwater in China 总被引:3,自引:0,他引:3
In China, high-fluorine groundwater, which contains more than 1.0 mg/l fluorine, is mainly distributed in shallow aquifers
of unconsolidated deposits in some arid and semiarid areas, deep aquifers of unconsolidated deposits in semiarid areas, as
well as in hot springs of bed rock mountainous area and aquifers of fluorite-mine area. Its formation is controlled by regional
climate factors, seepage conditions of groundwater, as well as the hydrogeochemical environment. The physicochemical properties
of soil mass of the aeration zone play an important role in fluorine concentration in shallow groundwater. In the coastal
plain areas, where groundwater is mainly recharged and discharged vertically, and its regime type belongs to the type of infiltration—evaporation,
the grain size of soil mass of aeration zone directly influences the amount of fluorine transferred from solid medium into
water; and the chemical constituents of the soil mass of aeration zone controls the chemical characteristics of the shallow
groundwater, consequently influencing the concentration condition of fluorine in water.
Fluorine ion in groundwater continuously migrates and concentrates under the comprehensive influence of many factors. High-fluorine
groundwater exceeding the sanitary standard (1.0 mg/l) has an obvious zonality in regional distribution in China. Based on
current statistics, there are roughly 50 million people (Zheng Qifu 1986) who have consumed water which exceeds standards
in China. In highfluorine groundwater areas, endemic fluorine-poisoning often arises to different extents, affecting human
health seriously. At the end of 1983, over 20 million patients were suffering from fluorine-poisoning diseases in China (Xu
Guozhang, unpublished data). Therefore, research of the distribution feature and formation mechanism of fluorine ion in groundwater
has become an important task. 相似文献
965.
Wang Andong Ren Yuhe Sun Wenfu Yu Longwei Liang Jingming Cao Tianqing Gu Haoding 《地震学报(英文版)》1988,1(4):60-72
We have obtained altogether heat flux data of 23 drill holes including 2 observational holes of thermal flow in the Haicheng
seismic area. These data show roughly thermal structure of the crust in eastern Liaoning and in the Haicheng seismic area.
The results indicate that there is higher value of heat flow in the belt north by east from Liaoyang to Xiongyue, the average
thermal flux being 8.29× 10−2J/m2·s (2.0 hfu). The average thermal fulx in the Haicheng seismic area is 9.22×102J/m2·s (2.2 hfu).
Comparing with other known geophysical data of the Haicheng seismic area, we give a geophysical section of comprehensive interpretation.
We suppose the low-velocity layer in the lower crust of the Haicheng seismic area is a result from intrusion of large-scale
uper mantle substance. High temperature and low velocity mean that the layer has the nature of plastic mechanics. The focal
region of the Haicheng earthquake is situated right in the upper part of that plastic layer. Obviously, this result is significant
for studying the seismogenic process of the Haicheng earthquake and other intra-plate earthquakes.
We attempt to emphasize that observation of heat flow is necessary for earthquake study.
Gu Haoding did the actual writing. 相似文献
966.
Most of the sulfide nickel deposits in China occur on the margins of platforms and their outer mobilebelts. The ore-bearing basic-ultrabasic rock bodies were formed in the Proterozoic and Variscan. The types ofmetallogenic rock bodies include ultrahasic-basic complexes related to volcanism in eugeosynclines andultrabasic rock bodies, ultrabasic-basic complexes and basic rock bodies related to deep fractures. On the basisof ore-forming processes and modes, nickel sulfide deposits of China may be divided into two major types:in-situ magmatic liquid unmixing deposits and deep-seated magmatic liquid unmixing injection deposits. Thelatter may by subdivided into four types: single injection deposits, multiple injection deposits, and pulsatory in-jection depositis, and late injection deposits which may inject into either comagmatic rocks or other kinds ofcountry rocks. Two metallogenic models for nickel sulfide deposits are proposed in this paper. 相似文献
967.
968.
Symmetrical folding of a single layer and folding process of an overfold are analyzed by using the finite element method. In the analysis, the constituent substances are assumed to be isotropic and incompressible and to behave as Newtonian fluids. The penalty function method is used to deal with incompressibility, The results of the analysis are compared with the data measured in the field and with those obtained by the elastopla(?)e finite element analysis, It shows that the overfold geometry may be well simulated by using the viscous fluid model. Thus, a possible mechanism of the formation of overfold is proposed. 相似文献
969.
Ren Jishun 《《地质学报》英文版》1987,61(1):23-36
After the Variscan Cycle, the global tectonic framework underwent three major adjustments. The first occurred in the Late Triassic-initial Jurassic, the second in the Late Jurassic-early Early Cretaceous and the third in the Late Cretaceous-Eogene. On that basis, the post-Variscan tectonic history is divided into three tectonic cycles——the Indosinian, Yanshanian and Himalayan Cycles. The post-Neocom(k_1~1) andpre-Aptian(k_1~2) tectonic movement marks the end of the Yanshanian orogeny in eastern China and the initiation of the subduction of the Tethyan ocean in western China and represents the boundary between the Yanshanian and Himalayan Tectonic Cycles. 相似文献
970.
Gravity field terrain effect computations by FFT 总被引:2,自引:2,他引:2
René Forsberg 《Journal of Geodesy》1985,59(4):342-360
The widespread availability of detailed gridded topographic and bathymetric data for many areas of the earth has resulted
in a need for efficient terrain effect computation techniques, especially for applications in gravity field modelling. Compared
to conventional integration techniques, Fourier transform methods provide extremely efficient computations due to the speed
of the Fast Fourier Transform (FFT. The Fourier techniques rely on linearization and series expansions of the basically unlinear terrain effect integrals, typically
involving transformation of the heights/depths and their squares. TheFFT methods will especially be suited for terrain reduction of land gravity data and satellite altimetry geoid data.
In the paper the basic formulas will be outlined, and special emphasis will be put on the practial implementation, where a
special coarse/detailed grid pair formulation must be used in order to minimize the unavoidable edge effects ofFFT, and the special properties ofFFT are utilized to limit the actual number of data transformations needed. Actual results are presented for gravity and geoid
terrain effects in test areas of the USA, Greenland and the North Atlantic. The results are evaluated against a conventional
integration program: thus, e.g., in an area of East Greenland (with terrain corrections up to10 mgal), the accuracy ofFFT-computed terrain corrections in actual gravity stations showed anr.m.s. error of0.25 mgal, using height data from a detailed photogrammetric digital terrain model. Similarly, isostatic ocean geoid effects in the
Faeroe Islands region were found to be computed withr.m.s. errors around0.03 m 相似文献