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891.
介绍如何利用GPS水准点加强和改善天文重力水准网的原理、方法及实现的途径。以单线推进路线为例,一般证明GPS水准点的控制作用。还着重讨论并验证间接平差方法的有效性,能够满足当前需要。 相似文献
892.
无定向附合导线的实用性分析 总被引:1,自引:0,他引:1
本文介绍了无定向附合导线的应用、两种平差计算的方法及精度分析 ,证明了无定向附合导线是一种可靠、实用的控制方法。 相似文献
893.
本文导出了中点多边形近似平差的新算法,并给出了适合任意中点多边形平差的计算程序,计算结果和传统方法一致,但避免了数据的重复输入,提高了计算效率。 相似文献
894.
A survey of unbalanced flow diagnostics and their application 总被引:9,自引:0,他引:9
1.IntroductionImbalanceisdefinedintermsoftowhatextenttheflowdepartsfromabalancedstate.Despitetheapparentcomplexityofatmosphericmotions,thepressure(massfield)andvelocity(momentum)distributioncanberelatedbyrathersimpleapproximateforcebalances(sothatparcelaccelerationscanbeignored).Davisetal.(1996)pointedoutthattheunderlyingassumptionofbalanceddingnosticsisthatthenowevolvesinawayconsistentwiththerestrictionsimplicitwithinthediagnosticframework.ThesimplesttwobalancerelationsaregeostrOPhl'cbalance… 相似文献
895.
DEFINITING AND ITS GEOLOGIC MEANING OF SOUTH-NORTH TREND FAULTED STRUCTURE BELT IN QIANGTANG BASIN, NORTH PART OF TIBET 总被引:5,自引:1,他引:4
There were more expounding to north—west (west) trend fault and north\|east trend fault within Qiangtang Basin, North Part of Tibet, in the past literature. With increasing of geophysical exploration data, nearly east\|west trend structure began to be taken note to. Since the year of 1995, by a synthetic study to geophysical and geological data, that south\|north trend faulted structures are well developed. These structures should be paid much more attention to, because they have important theoretical meaning and practical significance.1 Spreading of south\|north faulted structure belt According to different geological and geophysical data, the six larger scale nearly south\|north faulted structure belt could be distinguished within the scope of east longitude 84°~96° and near Qiangtang Basin. The actual location of the six belts are nearly located in the west of the six meridian of east longitude 85°,87°,89°,91°,93°,95° or located near these meridian. The six south\|north faulted structure belts spread in the same interval with near 2° longitude interval. The more clear and much more significance of south\|north trend faulted structure belts are the two S—N trend faulted structure belts of east longitude 87° and 89°. There are S—N trend faulted structure belts in the west of east longitude 83°,81°, or near the longitudes. The structure belts spreading features,manifestation,geological function and its importance, and inter texture and structure are not exactly so same. The structure belts all different degree caused different region of geological structure or gravity field and magnetic field. There is different scale near S—N trend faulted structure belt between the belts. 相似文献
896.
M. A. A. Gadallah 《Journal of Arid Environments》2000,44(4):451
Three-week old soybean (Glycine max) plants were subjected to a factorial combination of four regimes of soil matric water potential (ψm=−0·03, −0·5, −1·0 and −1·5 MPa), two levels of supplementary Zn (O and 20 mgl−1) and two levels of foliar IAA application (O and 10 mgl−1). Under control conditions (no Zn, no IAA), increasing soil drying progressively retarded shoot and root growth (length and dry mass production), reduced leaf relative water content (RWC) and decreased the contents of chlorophyll (Chl) and shoot soluble sugars (SS), but increased soluble sugar content of roots and lowered osmotic water potential of shoots and roots (osmotic adjustment). Total free amino acid (TAA) content increased in shoots but decreased in roots whereas contents of soluble proteins (SP) decreased in shoots and roots. The effect of water stress was statistically significant (p<0·05) and had a major effect (as indicated by η2values) on leaf RWC, shoot and root dry masses and osmotic potential. Supplementary Zn improved root growth at all levels of stress and shoot growth under severe stress. Improvement of growth was positively correlated with the internal tissue Zn concentrations (r=0·91 and 0·86 for shoot and 0·94 and 0·82 for root length and dry mass respectively). Exogenous IAA raised (p<0·05) RWC, Chl, DM (slightly), root SS, and SP, whereas shoot TAA was lowered. Effects on root TAA and shoot SS were more complex: they were lowered at zero stress and raised under severe stress. IAA and Zn in combination had additive effects on Chl, growth and osmotic potential, but their combined effects on SP and TAA were more complex. It is concluded that the treatment of soybean plants grown under conditions of low soil water potentials and Zn deficiency with Zn and IAA solutions counteracted the deleterious effects of stress, especially at high stress levels, and helped stressed plants to grow successfully under these adverse unfavourable conditions. 相似文献
897.
This paper examines the status of traditional agriculture in two areas of Azilal province in the Atlas Mountains, seeking to identify what is needed to counter any breakdown in livelihood strategies and improve the quality of life enjoyed by the farmers. Irrigated terrace agriculture is an important part of livelihood strategies in the areas studied and has the potential to be more productive and sustainable. In some areas it is reported to be endangered by socioeconomic changes and highland land degradation caused by excessive shifting cultivation, sheep and goat grazing, and charcoal production. Field visits made during summer 1998 to establish the condition of irrigated terrace and runoff agriculture and the factors affecting it showed that in at least one of the villages supportive social capital has ensured that challenges are being met and beneficial innovations are being made. Considerable variation in success was evident from community to community, with some farmers maintaining adequate lifestyles and innovating, while in other communities prospects are less promising. The effects of structural adjustment have clearly been felt and may also have triggered some of the highland degradation and difficulties, which clearly threaten some irrigated terrace agriculture and other livelihood practices. 相似文献
898.
International compilations of marine gravity, such as the International Gravity Bureau (BGI) contain tens of millions of point
data. Lemoine et al. (The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential
Model EGM96, NASA/TP-1998-206861) chose not to include any marine gravity in the construction of the global gravity model
EGM96. Instead they used synthetic anomalies derived from altimetry, so that no independent information about Mean Dynamic
Topography (MDT) can be deduced. Software has been developed not only to identify and correct those aspects of marine gravity
data that are unreliable, but to do so in a way that can be applied to very large, ocean-wide data sets. First, we select
only straight-line parts of ship-tracks and fit each one with a high-degree series of Chebyshev polynomials, whose misfit
standard deviation is σ
line and measures the random error associated with point gravity data. Then, network adjustment determines how the gravity datum is offset for each survey.
A free least squares adjustment minimises the gravity anomaly mismatch at line-crossing points, using σ
line to weight the estimate for each line. For a long, well crossed survey, the instrumental drift rate is also adjusted. For
some 42,000 cross-over points in the northern Atlantic Ocean, network adjustment reduces the unweighted standard deviation
of the cross-over errors from 4.03 to 1.58 mGal; when quality weighted, the statistic reduces from 1.32 to 0.39 mGal. The
geodetic MDT is calculated combining the adjusted gravity anomalies and satellite altimetry, and a priori global ocean model
through a new algorithm called the Iterative Combination Method. This paper reports a first demonstration that geodetic oceanography
can characterise the details of basin wide ocean circulation with a resolution better than global ocean circulation models.
The result matches regional models of ocean circulation from hydrography measurements (Geophys Res Lett 29:1896, 2002; J Geophys
Res 108:3251, 2003). 相似文献
899.
900.