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571.
The International Geographical Union Reports
IGU Commission on Geography of Commercial Activities 相似文献572.
Reports
Regional Seas Towards Sustainable Development 相似文献573.
We examine the question of whether or not the non-periodic variations in solar activity are caused by a white-noise, random process. The Hurst exponent, which characterizes the persistence of a time series, is evaluated for the series of14C data for the time interval from about 6000 BC to 1950 AD. We find a constant Hurst exponent, suggesting that solar activity in the frequency range from 100 to 3000 years includes an important continuum component in addition to the well-known periodic variations. The value we calculate,H 0.8, is significantly larger than the value of 0.5 that would correspond to variations produced by a white-noise process. This value is in good agreement with the results for the monthly sunspot data reported elsewhere, indicating that the physics that produces the continuum is a correlated random process and that it is the same type of process over a wide range of time interval lengths. 相似文献
574.
J. L. Culhane A. T. Phillips M. Inda-Koide T. Kosugi A. Fludra H. Kurokawa K. Makishima C. D. Pike T. Sakao T. Sakurai G. A. Doschek R. D. Bentley 《Solar physics》1994,153(1-2):307-336
Yohkoh observations of an impulsive solar flare which occurred on 16 December, 1991 are presented. This flare was a GOES M2.7 class event with a simple morphology indicative of a single flaring loop. X-ray images were taken with the Hard X-ray Telescope (HXT) and soft X-ray spectra were obtained with the Bragg Crystal Spectrometer (BCS) on board the satellite. The spectrometer observations were made at high sensivity from the earliest stages of the flare, are continued throughout the rise and decay phases, and indicate extremely strong blueshifts, which account for the majority of emission in Caxix during the initial phase of the flare. The data are compared with observations from other space and ground-based instruments. A balance calculation is performed which indicates that the energy contained in non-thermal electrons is sufficient to explain the high temperature plasma which fills the loop. The cooling of this plasma by thermal conduction is independently verified in a manner which indicates that the loop filling factor is close to 100%. The production of superhot plasma in impulsive events is shown to differ in detail from the morphology and mechanisms appropriate for more gradual events. 相似文献
575.
In the Hudson River estuary, fine mud and toxic metals are enriched in the upstream turbidity maximum. The mechanisms causing
the enrichment were assessed through the analysis of suspended-sediment concentration (SSC) (bottom and surface), particle
size, and trace metal distributions. Bottom SSCs varied across the study area by a factor of ten, and the turbidity maximum
activity was observed in between kilometers 45 and 80. The particle-size analysis defined two accumulation modes: <4.65 and
>22.1 μm. The ratio of the fine-to-coarse mode increased from 1.75 to 2.75 in the turbidity maximum. The fine mud concentration
(55–60%) in the turbidity maximum was found to have a high correlation (r=0.98;p<0.005) with the concentration of <2-μm particles. A conceptual model was derived in order to understand the possible mechanisms
by which fine mud (and specifically <2-μm particles) is concentrated. The two dominant size modes were analyzed for toxic
metals. The upstream tributaries are major sources of metals compared to point sources at downstream locations. In the turbidity
maximum, Cd, Cu, Zn, and Pb are significantly enriched compared to average shale metal values and ERM toxicity guidelines
by 580, 42, 10, 16 and 12, 7, 2.4, 1.4 times, respectively. Decreasing metal concentrations downstream of the turbidity maximum
imply that Haverstraw Bay acts as temporary storage for fine particles and enriched metals. It is demonstrated in this study
that toxic metals are enriched in Haverstraw Bay due to the mud accumulation. The high levels of toxic metals in the sediments
of the Hudson River estuary are a major concern because human activities (dredging and river traffic) cause resuspension of
sediments and can change the mobility patterns of bioavailable contaminants.
Received: 4 June 1997 · Accepted: 9 September 1997 相似文献
576.
The International Geographical Union Reports
IGU commission on population geography symposium on ethnicity and geography Ljubljana, Slovenia: September 8–11, 1993 (Second circular) 相似文献577.
J. P. Phillips P. G. Williams A. Mampaso N. Ukita 《Astrophysics and Space Science》1992,188(2):171-204
We have undertaken mapping and spectroscopy of a broad range of type I post-Main-Sequence nebulae in COJ=1→0,J=2→1, andJ=3→2, using the 12 m antenna at Kitt Peak, and the 45 m facility of the Nobeyama Radio Observatory. As a consequence, we find COJ=2→1 emission associated with NGC 3132 and NGC 6445, determine the location of COJ=1→0 emission in the nucleus of NGC 6302, and obtain (for the first time) COJ=3→2 spectroscopy for a substantial cross-section of type I sources. LVG analysis of the results suggests densitiesn(H2) ~ 104 cm?3, and velocity gradients dv/dr ~ 2×102 in both NGC 7027 and CRL 618, commensurate with uniform expansion of a constant velocity outflow, whilst for the case of NGC 2346 these values probably exceedn(H2) ~ 4.0×105 cm?3. dv/dr ~ 2.6×103 km s?1 andT k ~102 K, implying appreciable compression (and shock heating?) of the CO excitation zone. Hi masses extend over a typical range 0.01<M(Hi)/M ⊙<1, whilst corresponding estimates of the progenitor mass imply 0.7<M prog/M ⊙<2.3; values significantly in excess of those pertinent for normal PN, although somewhat at the lower end of the type I mass range. COJ=3→2 profiles for CRL 2688 confirm the presence of an extended plateau with width Δv~85 km s?1, whilst modestJ=3→2 enhancement is also observed for the high-velocity components in NGC 7027. TheJ=3→2 spectrum for NGC 2346 appears to mimic lower-frequency results reasonably closely, confirming the presence of a double-peaked structure towards the core, and predominantly unitary profiles to the north and south, whilst there is also evidence to suggest appreciableJ=3→2 asymmetry in CRL 618 compared to lower-frequency measures. The status of an extended cloud near HB 5 remains uncertain, although this clearly represents a remarkably complex region with velocity span ΔV~50 km s?1. Our presentJ=3→2 results appear to track lower frequency measures extremely closely, implying local densitiesn(H2)>3×103 cm?3—although temperatures close to theV lsr of HB 5 are relatively weak, and of orderT MB (J=3→2)≤0.9 K. Finally, as a result of both this, and previous investigations we find that of type I sources so far observed in CO, some ~42% appear to possess detectable levels of emissionT r * >0.1 K. Similarly, in cross-correlating this data with other results, we note a closely linear relation betweenJ=2→1 antenna temperaturesT MB, and the surface brightness of H2 S(1) quadrupole emissionS(H2)—a trend which appears also to be reflected betweenS(H2) and corresponding parameters for [Oi], [Oii], [Ni], [Nii], and [Sii]. Such relations almost certainly arise from comparable secular variations in line intensities, although the CO, H2, and optical emission components are likely to derive from disparate line excitation zones. As a consequence, it is clear that whilst H2 S(1) emission is probably enhanced as a result of local shock activity, the evidence for post-shock excitation of the CO and optical forbidden lines is at best marginal. Similarly, although it seems likely that CO emission derives from circum-nebular Hi shells with kinetic temperatureT k ~ 30 K or greater, the predominant fraction of low-excitation emission arises from a mix of charge exchange reactions, nebular stratification and, probably most importantly, the influence of UV shadow zones and associated neutral inclusions. 相似文献
578.
Titania, TiO2, precipitation in natural blue sapphire (Fe, Ti: -Al2O3) has been investigated using high resolution and analytical transmission electron microscopy. The structure and habit of the TiO2 precipitate depends on both the Ti4+ concentration and the temperature at which the precipitate formed. Tetragonal TiO2 (Rutile) grows at 1350° C but at 1150° C an orthorhombic non-equilibrium TiO2 polymorph precipitates. Both TiO2 polymorphs nucleate in the (0001)s plane as lens shaped discs twinned along their diameter. The crystallographic alignment of each type of TiO2 precipitate with respect to the -Al2O3 host matrix provides a high degree of structural coherency with minimal lattice mismatch. Electron diffraction analysis established the following precipitate/host orientation relationships: tetragonal TiO2: {011}r {11
07B;100}r(0001)s and 01
r10
0s twinned along the (011)r planeand orthorhombic TiO2: {021}{11
0}s, {100}(0001)s and 0
2 10
0s twinned along the (021) plane. 相似文献
579.
The International Geographical Union Reports
IGU Commission on Health and Development 相似文献580.
We present observations of three post-Main-Sequence nebulae taken with an intermediate despersion spectrograph mounted on the 2.5 m Isaac Newton Telescope (La Palma, Spain). Our results reveal evidence for high-velocity outflows of 102 km s–1 in the primary shells, and very much greater velocities in the cores, while in one unique souce there also appears to be evidence for a core WC binary.Paper presented at the 11th European Regional Astronomical Meeting of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献