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91.
We are totally immersed in the Big Data era and reliable algorithms and methods for data classification are instrumental for astronomical research. Random Forest and Support Vector Machines algorithms have become popular over the last few years and they are widely used for different stellar classification problems. In this article, we explore an alternative supervised classification method scarcely exploited in astronomy, Logistic Regression, that has been applied successfully in other scientific areas, particularly biostatistics. We have applied this method in order to derive membership probabilities for potential T Tauri star candidates from ultraviolet-infrared colour-colour diagrams. 相似文献
92.
M. G. Bernardini F. Xie P. Sizun F. Piron Y. Dong J.-L. Atteia S. Antier F. Daigne O. Godet B. Cordier J. Wei 《Experimental Astronomy》2017,44(1):113-127
SVOM (Space-based multi-band astronomical Variable Objects Monitor) is a Sino-French space mission dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade, capable to detect and localise the GRB emission, and to follow its evolution in the high-energy and X-ray domains, and in the visible and NIR bands. The satellite carries two wide-field high-energy instruments: a coded-mask gamma-ray imager (ECLAIRs; 4–150 keV), and a gamma-ray spectrometer (GRM; 15–5500 keV) that, together, will characterise the GRB prompt emission spectrum over a wide energy range. In this paper we describe the performances of the ECLAIRs and GRM system with different populations of GRBs from existing catalogues, from the classical ones to those with a possible thermal component superimposed to their non-thermal emission. The combination of ECLAIRs and the GRM will provide new insights also on other GRB properties, as for example the spectral characterisation of the subclass of short GRBs showing an extended emission after the initial spike. 相似文献
93.
巴黎能力建设委员会助力全球气候治理 总被引:1,自引:0,他引:1
张永香 《气候变化研究进展》2021,17(3):374-376
在全球气候治理中,能力建设涉及减缓、适应等多个方面.相对于发达国家,发展中国家在应对气候变化能力方面存在更多挑战,也亟待支持.巴黎能力建设委员会(PCCB)是《联合国气候变化框架公约》(以下简称公约)下属能力建设议题唯一的常设机构.在《巴黎协定》的授权下, PCCB于2016年成立,致力于解决发展中国家在实施和加强应对... 相似文献
94.
Evaluation of heavy metal contamination and implication of multiple sources from Hunchun basin, northeastern China 总被引:1,自引:0,他引:1
J.-W. Moon H.-S. Moon N.-C. Woo J.-S. Hahn J.-S. Won Y. Song X. Lin Y. Zhao 《Environmental Geology》2000,39(9):1039-1052
Present concentrations and distributions of heavy metals through profiles, surface soil, and stream sediment samples in the
Hunchun area, north-eastern China, were investigated to determine the elemental background values. This study also aims to
characterize potentially toxic materials such as pulverized fly ash (PFA) from power stations or ash and slag from coal used
domestically in urban areas, agrochemicals applied inappropriately, and urban sewage sludges from Hunchun City, as well as
to ascertain the possibility of natural enrichment through site characterization by mineralogical and geochemical investigation.
The distribution of contaminants in the alluvial soils (fluvisol) of this area has been influenced by several interacting
factors. The parent alluvial materials from weathered products of amphiboles have made coatings such as ferrihydrite, goethite,
and hematite. This natural inheritance factor is supported by the fact that the concentrations of weak acid-extractable (plant-available)
heavy metals are very low, except for Fe and Mn. However, in agricultural soils and adjacent stream sediments, an anthropogenic
input of Cd, Pb, Ni and Cr by agrochemicals is strongly suggested. Also, F contamination by coal combustion and the dissolution
of F-bearing minerals could cause some future problems. Wide distribution and significantly high concentrations of Cd, Fe,
Mn, and F in soils throughout the combination of pollutants originating from lithogenic and the anthropogenic sources pose
potential problems in utilizing water resources.
Received: 14 June 1999 · Accepted: 27 December 1999 相似文献
95.
Groundwater targeting in a hard-rock terrain using fracture-pattern modeling, Niva River basin, Andhra Pradesh, India 总被引:1,自引:0,他引:1
In hard-rock terrain, due to the lack of primary porosity in the bedrock, joints, fault zones, and weathered zones are the
sources for groundwater occurrence and movement. To study the groundwater potential in the hard-rock terrain and drought-prone
area in the Niva River basin, southern Andhra Pradesh state, India, Landsat 5 photographic data were used to prepare an integrated
hydrogeomorphology map. Larsson's integrated deformation model was applied to identify the various fracture systems, to pinpoint
those younger tensile fracture sets that are the main groundwater reservoirs, and to understand the importance of fracture
density in groundwater prospecting. N35°–55°E fractures were identified as tensile and N35°–55°W fractures as both tensile
and shear in the study area. Apparently, these fractures are the youngest open fractures. Wherever N35°–55°E and N35°–55°W
fracture densities are high, weathered-zone thickness is greater, water-table fluctuations are small, and well yields are
high. Groundwater-potential zones were delineated and classified as very good, good to very good, moderate to good, and poor.
Electronic Publication 相似文献
96.
Centuries of artificial recharge on the southern edge of the Sierra Nevada (Granada,Spain) 总被引:1,自引:0,他引:1
In the Alpujarra (southern Spain), every year between the March and June, an ancestral practice continues in the form of diverting water from the rivers by way of an extensive network of irrigation channels (acequias) to well-defined, highly permeable areas. This practice, known ascareos, constitutes an ancient example of artificial recharge. The objective is to guarantee a supply of drinking water during the dry months, as well as improve the physicochemical characteristics of the water. In addition, this system helps maintain moisture in the immediate environment, and thus has a positive effect on local vegetation. 相似文献
97.
A. Suryachandra Rao Y. Sadhuram V. V. Gopala Krishna 《Journal of Earth System Science》1995,104(4):607-611
We estimate, from the moisture budget the bulk aerodynamic coefficient for latent heat flux (C
e) during the monsoon season over the central Arabian Sea. The average value ofC
eunder active monsoon conditions was found to be 2.25 × 10−3 which is nearly 60% higher than those previously used. 相似文献
98.
Quantifying living roots in a marsh is a necessary but difficult task in wetland research. The two main difficulties usually encountered are distinguishing living from dead roots and processing a dense mat of fine roots. We found that living roots of salt-marsh plants release much more dissolved organic carbon (DOC) in boiling water than dead roots. Based on the finding, we developed a DOC procedure to quantify living roots of Spartina alterniflora and Juncus roemerianus. The DOC released in boiling water is a function of root activity, and the amount released can be used to calculate the living root biomass of a sample. The amount of living roots determined by the DOC method correlated well with the amount of living roots determined by the manual, sorting method (r2 = 0.78, p<0.01). The DOC method is more objective, precise, and much less tedious than the manual sorting method. 相似文献
99.
A statistical analysis for the Rf/φ method is developed in the paper. The technique provides estimates of Rs, Ri and θ according to Rf and φ. Moreover, we can restore the pattern of initial orientations of marker objects by means of their frequency histogram, provided the strain is homogeneous. It is unnecessary to postulate random initial orientations if the principal directions of strain ellipsoid are known. 相似文献
100.
Idael Francisco Blanco-Quintero C. Lázaro A. García-Casco J. A. Proenza Y. Rojas-Agramonte 《Contributions to Mineralogy and Petrology》2011,162(2):395-413
Whole-rock compositions of muscovite-bearing amphibolite, trondhjemite, pegmatite and quartz-muscovite rocks from Sierra del
Convento and La Corea mélanges (eastern Cuba), as well as mineralogy, record complex circulation of Ba-rich fluids and melts
in the subduction environment. Partial melting of fluid-fluxed, MORB-derived amphibolite produced trondhjemite magmas that
crystallized at depth, in some cases evolving into pegmatites. Qtz-Ms rocks probably crystallized from primary fluids derived
from subducted sediments. All these rocks have elevated concentrations of large-ion lithophile elements, especially Ba (up
to 11,810 ppm), presumably released from slab sediments by fluids and/or melts. Fluid–rock interaction produced crystallization
of phengite in parental amphibolites. The phengite crystallized in all types of rocks is rich in Ba, with concentric zoning,
characterized by Ba-rich cores and Ba-poor rims, indicating a compatible behaviour of Ba in the studied systems. Zoning in
phengite is governed primarily by the celadonite (tschermak) exchange vector ((Mg,Fe)Si-(Al)-2), with more moderate contributions of the celsian (BaAl-(KSi)-1) and paragonite (NaK-1) exchange vectors. Late remobilization of Ba at relatively low temperature formed retrograde celsian. The compatible behaviour
of Ba in the studied rocks strengthens the importance of the stability of phengite for the transfer of LIL elements from the
subduction to the volcanic arc environments. 相似文献