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991.
G. Lakshminarayana C. Manikyamba Tarun C. Khanna Prachiti P. Kanakdande K. Raju 《Journal of the Geological Society of India》2010,75(6):807-819
The Rajahmundry Traps of the Krishna Godavari Basin (K-G Basin) consist of three distinct basalt flows interbedded with two
intertrappean sedimentary horizons, which in turn are underlain by the late Cretaceous fossiliferous limestone bed (infratrappean)
and overlain by the Cenozoic Rajahmundry Formation (conglomerate/sandstone). Among the three, the lower flow is characterized
by the presence of the physical volcanological features such as rootless cones, tumuli and dyke like forms along with single
to multitier columnar and radial jointing. The middle and upper flows are simple, massive and vesicular and exhibit spheroidal
weathering. Physical volcanological features and lithological attributes indicate that the lower flow was formed by an explosive
volcanic activity in hydrous environment, followed by sub aerial eruption to form the middle and upper flows. The fossiliferous
limestone bed is a representative horizon for the K-T boundary mass extinction caused due to intense volcanism. Intertrappean
sediments exhibit weathered soil profiles (palaeosols) with limestone beds denoting a distinct time gap during various phases
of lava eruption. Evaluation of the palaeogeographic scenario of the Krishna and Godavari Rivers does not provide any evidence
for the existence of Cretaceous palaeovalley which would have provided pathway for lava transportation from the Deccan volcanic
province of western India to the K-G Basin situated along the east coast. The present study opens up an alternative approach
to explain the origin of basalt flows at Rajahmundry. In all probability the lavas could be intrabasinal. NW-SE and NESW faults
or their intersection zones are probable pathways for lava eruption in the K-G Basin. 相似文献
992.
The Mullipallam creek in Muthupet mangroves region is the only E-W trending coastal strip in the SE coast of India and is
very important, as the mangrove acts as a barrier to natural diasters. Natural, anthropogenic signals and accumulation of
elements were made by collecting sediment samples at various depths in a core. All sediments were analyzed for carbonates
(CaCO3), organic carbon (OC), major (Si, Al, Fe, Na, K, Ca, Mg, P), and trace (Mn, Cr, Cu, Ni, Co, Pb, Zn). Normalization with Al
values has been done for all the major and trace elements and enrichment factors have been calculated. The calculated enrichment
factors and comparison indicate that the trace metals (especially Pb) are enriched mainly due to the external (anthropogenic)
activities in the land as well as in the coastal zone (Palk Strait). 相似文献
993.
The strength and deformability of rock mass primarily depend on the condition of joints and their spacing and partially on
the engineering properties of rock matrix. Till today, numerical analysis of discontinuities e.g. joint, fault, shear plane
and others is conducted placing an interface element in between two adjacent rock matrix elements. However, the applicability
of interface elements is limited in rock mechanics problems having multiple discontinuities due to its inherent numerical
difficulties often leading to non-convergent solution. Recent developments in extended finite element method (XFEM) having
strong discontinuity imbedded within a regular element provide an opportunity to analyze discrete discontinuities in rock
masses without any numerical difficulties. This concept is based on partition of unity principle and can be used for cohesive
rock joints. This paper summarizes the mathematical frameworks for the implementation of strong discontinuities in 3 and 6
nodded triangular elements and also provides numerical examples of the application of XFEM in one and two dimensional problems
with single and multiple discontinuities. 相似文献
994.
The water characteristics of the Gucheng Lake, such as eutrophication, health and spatial distribution, were investigated.
On the basis of the trophic state index (TSI) and entropy weight, a synthesized trophic state index (STSI) model was established
to assess lake eutrophication condition through calculating STSI, choosing TP, TN, COD, BOD and NH3-N as trophic variables. The STSI ranged from 50.58 to 62.44, which showed that the water has been between eutrophic and supereutrophic.
A histogram was applied to health risk assessment which was analyzed from carcinogenic substances (Cr+6, As and Cd) and non-carcinogenic substances (hydroxybenzene, Pb, Hg, CN− and NH3), and the results showed that the former was much greater than the latter for effect. The total risk for each resident caused
by all pollutants ranged from 5.18E-05 to 8.34E-05, which is far higher than the standard, recommended by Sweden Bureau of
Environment Protection and Holland Ministry of Building and Environment Protection (1.0E-05). Cluster analysis was used to
detect similarities and dissimilarities among the seven sampling sites and explain the observed clustering in terms of affected
conditions. Twenty-one variables were used to divide seven sampling sites into three groups, namely, north lake, south lake
and lake center. 相似文献
995.
Gary Sands 《GeoJournal》2010,75(6):539-552
Canada’s three large city regions—Montréal, Toronto and Vancouver—have been relatively successful in retaining their Manufacturing
bases, while at the same time adding substantial numbers of New Economy job opportunities. Deindustrialization appears to
have occurred primarily in the Montréal CMA (Census Metropolitan Area) and in some smaller communities where motor vehicle
manufacturing was significant. Growth in New Economy jobs has occurred in the larger CMAs; the smaller urban areas have had
little success in attracting these jobs. For the most part, these trends appear to be path dependent: prosperous communities
with substantial proportions of New Economy jobs are likely to remain prosperous and to attract more such jobs. The lack of
significant correlation between Economic Health and the presence of immigrants, same sex couples, performing and visual artists
suggests that local economic development strategies based on these factors may have limited success. 相似文献
996.
In this paper, we describe the computational framework of a novel method for solving the challenging problem of probabilistic
finite elements. The method is called Improved Dynamic Bounds (IDB) and was developed recently to improve the efficiency of
the dynamic bounds. The IDB is used in finite element numerical models to calculate time-dependent failure analyses of structures.
In applications, the IDB can speed up the overall simulation process by several orders of magnitude. In applications controlled
by two influential variables (e.g, two-dimensional problem), the computational efficiency is improved by a factor of 769 according
to Rajabalinejad (2009). Applications of IDB indicate the method is most efficient for problems where the number of influential variables are limited.
This is often the case for geotechnical and coastal flood defence systems. The IDB method is applied in this paper to the
17th Street Flood Wall, a component of the flood defence system (levee infra-structure) that failed during the Hurricane Katrina,
to calculate the failure probability of an I-wall. 相似文献
997.
Debahuti Mukherjee 《Journal of the Geological Society of India》2010,76(3):267-274
The Bathonian sediments of the Jaisalmer Basin, India host a terebratulide brachiopod Plectoidothyris which has been previously known from the Bajocian rocks of the Boreal Province. The sharp and prominent plication of the
anterior commissure and increased length of costae separates the Jaisalmer specimens from other known species of the genus
and the population represents an endemic species — Plectoidothyris jaisalmerensis. The population was only cursorily described earlier lacking in details of precise stratigraphic control and was wrongly
assigned to a different genus. The present study is based on a large number of specimens from different localities with precise
stratigraphic data, coupled with this some recent findings of time-diagnostic ammonites have helped determine the Plectoidothyris jaisalmerensis duration in the Jaisalmer Basin as the Late Bathonian. Presence of lower Jurassic Boreal brachiopod genera in the Middle
Jurassic rocks of Ethiopian and Indo — Madagascan biogeographic provinces has been noticed earlier whereto Plectoidothyris is a new addition while it is also the first report of the genus from the Jurassic of India. The brachiopod migrations from
the north to south of the Tethys provide evidences for opening of shallow water routes in the Tethyan seaway and are probably
indicative of warmer water conditions in the Indo-Madagascan and African areas during the Middle Jurassic. 相似文献
998.
Measures of Parameter Uncertainty in Geostatistical Estimation and Geostatistical Optimal Design 总被引:2,自引:2,他引:2
Wolfgang Nowak 《Mathematical Geosciences》2010,42(2):199-221
Studies of site exploration, data assimilation, or geostatistical inversion measure parameter uncertainty in order to assess
the optimality of a suggested scheme. This study reviews and discusses measures for parameter uncertainty in spatial estimation.
Most measures originate from alphabetic criteria in optimal design and were transferred to geostatistical estimation. Further
rather intuitive measures can be found in the geostatistical literature, and some new measures will be suggested in this study.
It is shown how these measures relate to the optimality alphabet and to relative entropy. Issues of physical and statistical
significance are addressed whenever they arise. Computational feasibility and efficient ways to evaluate the above measures
are discussed in this paper, and an illustrative synthetic case study is provided. A major conclusion is that the mean estimation
variance and the averaged conditional integral scale are a powerful duo for characterizing conditional parameter uncertainty,
with direct correspondence to the well-understood optimality alphabet. This study is based on cokriging generalized to uncertain
mean and trends because it is the most general representative of linear spatial estimation within the Bayesian framework.
Generalization to kriging and quasi-linear schemes is straightforward. Options for application to non-Gaussian and non-linear
problems are discussed. 相似文献
999.
Recent studies of Chesapeake Bay hypoxia suggest higher susceptibility to hypoxia in years after the 1980s. We used two simple
mechanistic models and Bayesian estimation of their parameters and prediction uncertainty to explore the nature of this regime
shift. Model estimates show increasing nutrient conversion efficiency since the 1980s, with lower DO concentrations and large
hypoxic volumes as a result. In earlier work, we suggested a 35% reduction from the average 1980–1990 total nitrogen load
would restore the Bay to hypoxic volumes of the 1950s–1970s. With Bayesian inference, our model indicates that, if the physical
and biogeochemical processes prior to the 1980s resume, the 35% reduction would result in hypoxic volume averaging 2.7 km3 in a typical year, below the average hypoxic volume of 1950s–1970s. However, if the post-1980 processes persist the 35% reduction
would result in much higher hypoxic volume averaging 6.0 km3. Load reductions recommended in the 2003 agreement will likely meet dissolved oxygen attainment goals if the Bay functions
as it did prior to the 1980s; however, it may not reach those goals if current processes prevail. 相似文献
1000.
In Alborz Mountains, the thickness of sediments in Member 2 of the Mila Formation (Middle Cambrian) underwent dramatic and
abrupt deformations, which were accompanied by normal and reverse faults and asymmetrical folds. These deformed sediments
are covered by parallel beds both in the upper and lower sides. The existence of such extension and compression structures
adjacent to each other indicates the influence of non-tectonic factors in their evolution. These deformations induced by downslope
gliding of sediment packages are fully compatible with the dislocation model of Farrell (J Struct Geol 6:727–736, 1984) and Farrell and Eaton (1987). Moreover, the occurrence of synsedimentary deformations in a vast area in Alborz Mountains reinforces the probability of
the impact of seismic shocks in their formation. In fact, incessant seismic events in the Middle Cambrian led to numerous
submarine slumpings in the sediments of Member 2 of the Mila Formation. 相似文献