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941.
942.
943.
Olga Leaos-Castaeda Gerardo Gold-Bouchot Glen Van Der Kraak Andrea Lister Victor Ceja-Moreno Raul Sim-Alvarez 《Marine environmental research》2004,58(2-5):337
The objective of this study was to determine if tamoxifen or an aromatase inhibitor (4-hydroxyandrostenedione; 4-OHA) affected plasma concentrations of o,p′-DDT and its metabolites, o,p′-DDD and o,p′-DDE, in mature tilapia. Male and female tilapia were injected 6 times intraperitoneally with o,p′-DDT (40 mg/kg) alone or in combination with 4-OHA (2 mg/kg) over a 12 day period. An additional group of male fish was injected with tamoxifen (5 mg/kg) plus o,p′-DDT. At the end of the treatment period, plasma samples were extracted and analyzed by GC/ECD. Females injected only with o,p′-DDT had significantly higher levels of o,p′-DDT compared with males. Interestingly, females and males treated concomitantly with o,p′-DDT and 4-OHA or tamoxifen had significantly lower concentrations of plasma o,p′-DDT (about 50%) compared with fish treated with only o,p′-DDT. These initial results suggest that an interaction between endocrine-active compounds occurs in vivo in tilapia and may involve alterations in metabolism of o,p′-DDT. 相似文献
944.
The stable form of dissolved chromium in oxygenated seawater is Cr(VI). But Cr(III)-species are also present at an analytically significant level. It is shown that Cr(III) is oxidized only slowly by dissolved oxygen, and that manganese oxide is a strong catalyst for such oxidation. However, the low oceanic concentration of suspended MnO2 impedes the conclusion that the former process is quantitatively less important than the latter one. The distribution of dissolved chromium among Cr(VI)- and Cr(III)-species is probably kinetically controlled. 相似文献
945.
946.
P. Ya. Baklanov V. V. Ermoshin V. P. Karakin V. V. Zharikov Nguyen Van Cu Dao Dinh Cham 《Geography and Natural Resources》2017,38(4):333-340
Coastal-marine nature management is treated as a spatiotemporal structure consisting of two interrelated components: the coastal territorial component occurring in the coastal territory, and the coastal aquatic component occurring within the coastal aquatic area as well as the sea shores connecting them. The study revealed the components of the main and concomitant uses of natural resources which have evolved directly across the land and sea areas of mining of separate kinds of natural resources and having technogenic impacts on them. From a combination of natural resources as well as of spatial scales of the main and concomitant uses of natural resources on the coastal territory and in coastal waters, we identified the main types of coastal-marine nature management in the southern areas of Pacific Russia and in Northern Vietnam: different kinds of nature management including the utilization of the territory for industrial-residential and transportation purposes as well as for cultivation of rice and vegetable crops, extraction of building materials, other mineral resources, forest use, extraction of marine salt from the sea water, coastal fisheries, various forms of mariculture, marine recreation, etc. A fragment of the cartographic assessment of the current types of coastal-marine nature management is presented for the southern coastal areas of Pacific Russia. 相似文献
947.
Abrahamsen N. Bengaard H-J. Friderichsen J.D. Van der Voo R. 《Geologie en Mijnbouw》1997,76(1-2):83-95
Three basic dyke swarms of post-Ellesmerian (post-Early Carboniferous) age in Nansen Land (83° N, 43° W) are still not dated numerically, but cross-cutting relationships show Group 1 to be older than Group 2, while Group 3 is the freshest and likely the youngest. Group 1 (the most northerly swarm) strikes N-S; Group 2 NW-SE, and Group 3 (the most southerly swarm) E-W. From more than 200 dykes 234 specimens from 28 sites were investigated palaeomagnetically. Group 1 dykes show unexpected shallow inclinations with a cleaned mean direction of (Dm, Im) = (151°, –5.8°), N = 7, k = 18.5, 95 = 13.9°. They show hydrothermal alterations, some remagnetization by lightning, and the low inclination indicates a low palaeo latitude. The palaeopole is (Plat, Plon) = (8.9° S, 14.0° W) with (dp, dm) = (7°, 14°), and is close to the North American Early Carboniferous mean pole, suggesting a syn- or early late-tectonic dyke injection. The polarity is reverse. Groups 2 and 3 of presumed Cretaceous or Tertiary age show dominantly normal and reverse polarities, respectively. Their mean directions per polarity are well grouped, with (Dm, Im) = (–30.6°, 76.7°), n = 13, k = 191.4, 95 = 3.9°, and (Dm, Im) = (133.4°, –76.7°), n = 10, k = 87.5, 95 = 5.9°, respectively. They are antipodal within 95% significance, and combining both swarms gives (Dm, Im) = (–37.5°, 76.8°), n = 23, k = 124.3, 95 = 2.7°, corresponding to a mean pole of (Plat, Plon) = (70.0° N, 185.1° E) with (dp, dm) = (4.7°, 5.0°), for which the spline of Late Cretaceous-Tertiary poles for all Greenland indicates a palaeomagnetic age of 57 ± 10 Ma. This pole (in present-day coordinates) is very close to the Late Cretaceous North American pole, in accordance with the fact that Greenland belongs to the North American craton, and that the two younger swarms are essentially postdating the opening of Baffin Bay. 相似文献
948.
Observations of circumstellar dust clouds of Wolf-Rayet stars made with the Short Wavelength Spectrometer on ISO reveal a
subtle variety of spectral energy distributions not evident from ground-based observations. The modelling of these using the
radiative transfer code "Dusty" by Ivezić, Nenkova & Elitzur is reported. The results are used to examine the contributions
by different possible grain types to the emission and of circumstellar and interstellar components to the reddening.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
949.
K. P. Dere G. E. Brueckner R. A. Howard M. J. Koomen C. M. Korendyke R. W. Kreplin D. J. Michels J. D. Moses N. E. Moulton D. G. Socker O. C. St. Cyr J. P. Delaboudinière G. E. Artzner J. Brunaud A. H. Gabriel J. F. Hochedez F. Millier X. Y. Song J. P. Chauvineau J. P. Marioge J. M. Defise C. Jamar P. Rochus R. C. Catura J. R. Lemen J. B. Gurman W. Neupert F. Clette P. Cugnon E. L. Van Dessel P. L. Lamy A. Llebaria R. Schwenn G. M. Simnett 《Solar physics》1997,175(2):601-612
We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations
with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of
prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated
to about 100 km s-1 and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at
a velocity of 200–400 km s-1. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in
the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the
LASCO coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest is the fact that this large-scale event, spanning
as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 104 km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated
with this event as well as a considerable degree of activity near the west limb. 相似文献
950.
Van Driel-Gesztelti L. Csepura G. Schmieder B. Malherbe J.-M. Metcalf T. 《Solar physics》1997,172(1-2):151-160
We present a study of the evolution of NOAA AR 7205 in the photosphere and corona, including an analysis of sunspot motions, and show the evolutionary aspects of flare activity using full-disc white-light observations from Debrecen, vector magnetograms from Mees Observatory, Hawaii, and Yohkoh soft X-ray observations. NOAA AR 7205 was born on the disc on 18 June, 1992. During the first 3 days it consisted of intermittent minor spots. A vigorous evolution started on 21 June when, through the emergence and merging (v 100–150 m s-1) of several bipoles, a major bipolar sunspot group was formed. Transverse magnetic fields and currents indicated the presence of shear (clockwise twist) already on 21 June (with 0.015 Mm-1). On 23 June, new flux emerged in the trailing part of the region with the new negative polarity spot situated very close to the big positive polarity trailing spot of the main bipole. The secondary bipole seemed to emerge with high non-potentality (currents). From that time the AR became the site of recurrent flare activity. We find that all 14 flares observed with the Yohkoh satellite occurred between the highly sheared new bipole and the double-headed principal bipole. Currents observed in the active region became stronger and more extended with time. We propose that the currents have been (i) induced by sunspot motions and (ii) increased by non-potential flux emergence leading to the occurrence of energetic flares (X1.8 and X3.9). This observation underlines the importance of flare analysis in the context of active region evolution. 相似文献