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111.
George M. Woodwell 《Climatic change》1991,19(1-2):245-251
Forests contain more than twice as much carbon as the atmosphere and process through their metabolism about 1/7 of the atmospheric carbon annually. Deforestation currently is adding carbon to the atmosphere as carbon dioxide at an increasing rate and causing the impoverishment of soils over large areas in the tropics. But deforestation is also occurring in the temperate and boreal forests. In most cases deforestation is the result of national policies. It proceeds in the United States in response to economic pressures and political weakness, even corruption.The re-establishment of forests has the potential for contributing to the stabilization of the composition of the atmosphere by removing carbon as carbon dioxide from the atmosphere and storing it on land for an indefinite period. Such a transition in land use is difficult to imagine in a world in which the human population is expanding continuously and impoverished land is accumulating.Global interests in management of forests introduce a new element into international relations. Progress in effecting the shifts in controls on land use required to control deforestation in the interests of stabilizing climate and preserving biotic resources will depend on clear definition of the details of the problem by the scientific community and a further definition of how to proceed. 相似文献
112.
North American literature on the changing role of the local state these past two decades has been dominated by the view of a transition from urban managerialism to urban entrepreneurialism. Associated with the transition has been the emergence of a New Urban Politics (NUP). Within a political economy framework. the NUP has been rooted in the material redistributive effects of the transition. This paper explores the character of this NUP, as experienced by one British city, and highlights some fundamental differences with the established political economy reading. Our argument, based upon the city of Glasgow, draws attention to two distinctive features. First, the institutional structure of urban governance in Glasgow differs from that of cities in the United States. In Glasgow, it has been the Left controlled local Council which has orchestrated the transition to entrepreneurialism, rather than the North American model of a coalition between local capital and the local state. Secondly, the transition in Glasgow has been marked not by a significant transfer of local state revenue from service provision to local economic development, but by a symbolic reorientation of the local state as marked by the central importance of large place marketing hallmark events. These events represent the city in ways which differ from traditional ‘self’ identities. Consequently, the transition has evoked a political response which has focused upon the symbolic posturing of the local state rather than the material consequences of the shift. In focusing upon local identity, the politics of urban entrepreneurialism in Glasgow points to a dimension of conflict which has received inadequate treatment in accounts of the NUP to date. 相似文献
113.
The band positions of three partially overlapping Fe2+ spin-allowed transitions located between 4000 and 9000 cm–1 in almandine-pyrope and almandinespessartine garnets solid solutions were measured using near-infrared (NIR) spectroscopy. The crystal field stabilization energies (CFSE) along both binaries were calculated assuming a splitting of 1100 cm–1 for the lower orbitals. The CFSE show a slight increase along the almandine-spessartine binary from 3730 to 3810 cm–1 and a larger increase from 3730 to 3970 cm–1 for the almandine-pyrope binary. Dodecahedral Fe2+-site distortion increases with an increase in spessartine component and decreases with increasing pyrope component, in agreement with average dodecahedral site distortions determined from diffraction experiments. The excess CFSE's along both joins are negative. For the almandinespessartine binary they are small, but are about 3.5 times larger in magnitude along the join almandine-pyrope, where an interaction parameter of W= -2.9 KJ/mole has been derived from a symmetric mixing model. The excess CFSE are relatively small compared to the magnitudes of the excess enthalpies of mixing that have been assigned to garnet solid solutions. Moreover, they give no indication which could support the positive and asymmetric excess enthalpies of mixing that have been proposed for almandine-pyrope solid solutions. 相似文献
114.
George M. Woodwell 《Climatic change》1989,15(1-2):31-50
The dominant influence on global climate for the indefinite future is expected to be a warming in the middle and high latitudes of both hemispheres. The speed of the warming is uncertain. The warming in winter may exceed 1.0 degree per decade. The warming in summer is expected to be less. The cause is the accumulation of infra-red absorptive gases, especially CO2 and CH4, in the atmosphere. The sources are the combustion of fossil fuels, the destruction of forests and their soils, and, possibly, the warming itself, which can be expected to stimulate decay of organic matter in soils. The warming in these latitudes is expected to be accompanied by increased precipitation as climatic zones migrate generally poleward. A 1 °C change in mean temperature is equivalent to a change in latitude of 100–150 km. The changes expected are rapid enough to exceed the capacity of forests to migrate or otherwise adapt. Forest trees will die at their warmer and drier limits of distribution more rapidly than forests can be regenerated in regions where climates become favorable. The destruction of forests will add further to the releases of C to the atmosphere. There is no equivalent countervailing storage that has been identified. The result suggests that a significant enhancement of the warming beyond current predictions is to be expected. An open-ended, accelerating warming of the Earth at rates that bring rapid changes in climatic zones, drive forests to impoverishment, and raise sea level rapidly is beyond the limits of simple adjustments of the human enterprise. Steps to stabilize the atmospheric composition seem inevitable. Because the total emissions of C to the atmosphere are not known, the current rate of transfer from the atmosphere to the oceans is uncertain. But whatever the current total release to the atmosphere, the annual atmospheric increase is about 3.0 G-tons of C as CO2. At least three possibilities exist for reducing or eliminating the imbalance and moving toward long-term stability:
- a reduction in the use of fossil fuels globally, now estimated as the source of about 5.6 G-tons of C annually;
- a reduction or cessation of deforestation, now estimated as releasing 1–3 G-tons annually;
- a vigorous program of reforestation that would remove from the atmosphere into storage in plants and soils about 1 G-ton of C annually for each 2 × 106 km2 tract reforested.
115.
Achache et al.'s averages over 10 west European observatories of the annual mean magnetic components X, Y, Z are studied from 1953 to 1979. A 1970 jerk is fitted to the data by least squares, and the fit is quantitatively compared with that of a polynomial having the same number of free parameters as the jerk (a quintic). A crude correction for the 11-y sunspot cycle is also attempted. The jerk and quintic are equally good fits to X, the jerk is clearly better for Y, and the quintic is modestly better for Z. The jerk amplitudes of X and Z but not Y depend heavily on whether a sunspot correction is made, and such a correction may be required to estimate the energy of the internal part of the jerk in the manner of Malin and Hodder. The sunspot correction to Y probably cannot be brought above the noise because it is small and highly correlated with both the jerk and the quintic. The sunspot corrections to X and Z are statistically significant but depend on whether the core signal is taken as a jerk or a quintic. Courtillot and Le Mouël's physical model for the jerk predicts that the jerk amplitudes of X, Y, Z will be proportional to the longitudinal derivatives of X, Y and Z. This prediction is roughly verified for the magnitudes but not the signs; it is just possible that the signs in X and Z are not statistically significant. 相似文献
116.
The magnitude M = 6-5 Coalinga earthquake of 2 May 1983 caused intense ground shaking throughout the epicentral region. Unanchored cylindrical ground supported tanks located at six sites within this oil producing area were damaged; damages included elephant's foot buckling at the base of three moderate sized tanks, joint rupture and top shell buckling in one large old rivetted tank, bottom plate rupture of a relatively new welded tank and damage to the floating roofs of 11 tanks. Also oil spilled over the top of many tanks and secondary damages occurred in pipe connections, ladders, etc. In this paper an estimate is made of the intensity of ground motion at each of the tank sites, based on strong motion records made during the main shock and the strongest aftershock. Then response parameters specified by current codes are correlated with the damages observed at each tank site. Based on this comparison, it is concluded that current U.S. practice under-estimates the sloshing response of tanks with floating roofs and does not adequately address the uplifting mechanism of unanchored ground supported tanks. 相似文献
117.
George Devries Klein 《Tectonophysics》1985,119(1-4)
The frequency and periodicity of preserved graded turbidite cycles in submarine fans in the Coral Sea and Sea of Japan are correlated to times of tectonic uplift in response to major collisions in the Owen-Stanley Range of Papua and the Hida Range of Japan, respectively. Large frequencies and shorter-term periodicities of turbidites at DSDP Site 210 were coeval with early Pliocene maximum tectonic-uplift rates which occurred in the Owen-Stanley Range in response to obduction. Similarly, large frequencies and shorter-term periodicities of turbidites at Site 299 (Toyama Submarine Fan) were coeval with the late Pleistocene uplift in the Hida Range; this uplift of 1000 to 1500 m occurred in response to collision tectonics. In both cases, trends of increasing frequencies and towards shorter-term periodicities of preserved turbidite depositional events correlate to trends of increasing rates of tectonic uplift.The role of sea-level fluctuations on changing denudation rates in these two collision zones is secondary. At Site 210, larger frequencies and short-term periodicities of preserved turbidites were coeval with early Pliocene high stands of sea level, whereas at Site 299, Pleistocene sea-level fluctuations are considered minor because at low stands of sea level, both relief and denudation rates were increased by about ten to 14%. At Site 286 (New Hebrides Basin), Eocene turbidite deposition is coeval with high stands of sea level, whereas at Site 297 (Northern Shikoku Basin), turbidite deposition was coeval with both rising and falling sea level.Analysis of both frequency and periodicity of turbidites by fan subenvironment at Site 299 indicates a record of continuous deposition, and maintainance of frequency and periodicity trends controlled by tectonic uplift. Late Pleistocene channel and overbank deposits showed periodicity differences of less than 28% of an order of magnitude, whereas Miocene-Pliocene overbank and distal turbidite periodicities differed by a 19% order of magnitude. Greater differences in magnitude occurred between distal turbidites or early Pleistocene age and Pliocene age than between Miocene-Pliocene overbank and distal turbidite deposition with a magnitude difference of 860%. These findings suggest that shifting depocenters and differences in sedimentation history in subenvironments of submarine fans are secondary to the role of tectonic uplift in this particular case.The minimal rate of tectonic uplift required to generate deep-sea fan turbidities appears to be approximately 400 m/million years. This figure is tentative and is based on very few observation points.Frequency and periodicity of preserved turbidite cycles in submarine fans in active continental margins and ancient counterparts should provide an independent measurement of rates and timing of tectonic uplift, particularly in collision terrains. Because this sediment parameter is a record of a single process from a single source and a record of “event stratigraphy”, its usage is preferable over standard and bulk sediment accumulation rates determined from age depth curves. 相似文献
118.
Spindle- and parabolic-shaped drumlins examined at fifty-five localities in northern Ireland possess stratification sequences on their lee-side flanks. These forms lack the distinctive steep stoss- and tapering lee-ends of classical drumlins and tend to occur in linear zones transverse to late Pleistocene ice-flow. In most cases (90 per cent) the stratified deposits infill embayments excavated in the lee-side of barkhanoid forms and, in the remainder (10 per cent), they are superimposed on the lee-side of whaleback forms. The stratification sequences developed as a result of sedimentation in interconnected subglacial water-filled cavities and are unlike remanie proglacial sediments moulded by ice into drumlin form. Stratigraphic evidence indicates that the lee-side sequences developed during drumlin streamlining, which supports the view that subglacial hydraulic processes played an important role in drumlin formation. 相似文献
119.
120.
Hydrogen speciation in synthetic quartz 总被引:1,自引:0,他引:1
Roger D. Aines Stephen H. Kirby George R. Rossman 《Physics and Chemistry of Minerals》1984,11(5):204-212
The dominant hydrogen impurity in synthetic quartz is molecular H2O. H-OH groups also occur, but there is no direct evidence for the hydrolysis of Si-O-Si bonds to yield Si-OH HO-Si groups. Molecular H2O concentrations in the synthetic quartz crystals studied range from less than 10 to 3,300 ppm (H/Si), and decrease smoothly by up to an order of magnitude with distance away from the seed. OH? concentrations range from 96 to 715 ppm, and rise smoothly with distance away from the seed by up to a factor of three. The observed OH? is probably all associated with cationic impurities, as in natural quartz. Molecular H2O is the dominant initial hydrogen impurity in weak quartz. The hydrolytic weakening of quartz may be caused by the transformation H2O + Si-O-Si → 2SiOH, but this may be a transitory change with the SiOH groups recombining to form H2O, and the average SiOH concentration remaining very low. Synthetic quartz is strengthened when the H2O is accumulated into fluid inclusions and cannot react with the quartz framework. 相似文献