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681.
682.
Using the ground based neutron monitor data of Deep River, the high-amplitude anisotropic wave train events (HAE) in cosmic ray intensity have been investigated during the period 1991-1994. It has been observed that the phase of diurnal anisotropy for majority of HAE shifts towards later hours; whereas it remains in the corotational/18-h direction for some of the HAE cases. Further, for majority of HAE cases the amplitude of diurnal and semi-diurnal anisotropy significantly deviates from the annual average values. The phase of semi-diurnal and tri-diurnal anisotropy for all HAE cases has shifted to later hours. Furthermore, for tri-diurnal anisotropy the amplitude remains statistically the same. The occurrence of HAE is unaffected by the nature of the Bz component of IMF polarity. 相似文献
683.
Zhang Yujiang Zhan Songmei Cao Pengli Liu Ning Chen Xuehong Wang Yuejun Wang Chunbo 《中国海洋湖沼学报》2005,23(3):357-362
To investigate the effect of polypeptide fromChlamys farreri (PCF) on NHDFin vitro, we modeled oxidative damage on normal human dermal fibroblasts (NHDF) exposed to ultraviolet B (UVB). In this study, 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium
bromide (MTT) and lactate dehydrogenase (LDH) were tested to measure cell viability. Enzymes including superoxide dismutase
(SOD), glutathione peroxidase (GSH-PX), catalase (CAT) and xanthine oxidase (XOD) were determined biochemically. Total antioxidative
capacity (T-AOC) and anti-superoxide anion capacity (A-SAC) were also determined. Ultrastructure of fibroblasts was observed
under transmission electron microscope. The results showed that: UVB (1.176×10−4 J/cm2) suppressed the growth of fibroblasts and the introduction of PCF (0.25%–1%) before UVB reduced the suppression in a concentration-dependent
manner. PCF could enhance the activities of SOD, GSH-PX and T-AOC as well as A-SAC. Also PCF could inhibit XOD activity, while
it did not affect CAT activity. Ultrastructure of fibroblasts were damaged after UVB irradiation, concentration-dependent
PCF reduced the destructive effect of UVB on cells. These results indicated that PCF can protect human dermal fibroblasts
from being harmed by UVB irradiation via its antioxidant proerty.
This work was supported by the National Natural Science Foundation of China (No. 39970638) and the Science and Technology
Bureau of Qingdao (No. 2001-28-50). 相似文献
684.
Francis Halzen 《Astrophysics and Space Science》2007,309(1-4):407-414
Although kilometer-scale neutrino detectors such as IceCube are discovery instruments, their conceptual design is very much
anchored to the observational fact that Nature produces protons and photons with energies in excess of 1020 eV and 1013 eV, respectively. The puzzle of where and how Nature accelerates the highest energy cosmic particles is unresolved almost
a century after their discovery. From energetics considerations we anticipate on the order of 10–100 neutrino events per kilometer
squared per year pointing back at the source(s) of both galactic and extragalactic cosmic rays. In this context, we discuss
the results of the AMANDA and IceCube neutrino telescopes which will deliver a kilometer-square-year of data over the next
3 years. 相似文献
685.
R.K. Manchanda 《Astrophysics and Space Science》2002,282(1):149-160
The spectral and temporal measurements in the hard X-ray region between 20-200 keV not only determines the extended behaviour
of thermal X-ray spectrum below 10 keV but also provide a unique insight into the non-thermal processes in relativistic astrophysical
plasma. From our present understanding of the X-ray sources, a significant fluxin the 20-200 keV band is expected from a variety
of astrophysical phenomena, however, the available spectral data on the galactic and extragalactic X-ray source is very limited.
This is mainly due to the fact that sensitivity of the detector systems used for earlier measurements was relatively poor.
Since 1997, we have been carrying out a programme of hard X-ray observations galactic and extragalactic sources, in the 20-200
keV energy band using a highly sensitive balloon borne experiment. The X-ray telescope consists of three modules of large
area scintillation counters specially configured in the back-to-back geometry and have a combined sensitivity of ∼ 10-6 ph cm-2 s-1 keV-1 for an on-source observations of 3 hrs. A total of 30 hours of ceiling data above an altitude of 3 mbar has been collected
in 4 successful balloon flights from Hyderabad, India. Almost a dozen galactic and extragalactic X-ray sources were targeted
and tracked during these observations. A positive detection was made in each case and in some cases the observed spectra extended
right up to 150 keV. A brief account of the observed spectral and temporal features on some of the sources along with accurate
measurement of diffuse background spectrum and a weak gamma ray burst will be presented in the paper.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
686.
687.
A Practical Method for Accurate Measurement of Trace Level Fluorine in Mg‐ and Fe‐Bearing Minerals and Glasses Using Electron Probe Microanalysis 下载免费PDF全文
Chao Zhang Jürgen Koepke Lian‐Xun Wang Paul E. Wolff Sören Wilke André Stechern Renat Almeev Francois Holtz 《Geostandards and Geoanalytical Research》2016,40(3):351-363
Fluorine plays an important role in magmatic and hydrothermal processes, but due to its low abundance in geological samples determining F is difficult by electron probe microanalysis. By using a W‐Si multi‐layered pseudocrystal as the diffraction crystal instead of thallium acid phthalate (TAP), count rates were considerably higher, which however introduced spectral interferences between FKα and FeLα and MgKβ lines when normal integral mode is applied. In this study, we developed a protocol using a W‐Si multi‐layered pseudocrystal for measuring accurately trace level F in both minerals and glasses. First, we used differential mode with an optimised PHA (pulse height analysis) setting in signal processing, instead of normal integral mode, which completely eliminated the second‐order MgKβ line. Second, the overlap of the first‐order FeLα on FKα peak, which cannot be filtered by modifying the PHA setting, was calibrated quantitatively using F‐free minerals and silicate glasses. Applying this two‐step method, F was determined in a number of reference glasses, as well as in glasses synthesised from powders of the rock reference materials AC‐E, GS‐N and DR‐N. Our data are consistent within error with F concentrations determined by other methods, demonstrating the reliability of this method. 相似文献
688.
《Marine Policy》2016
In the Northeast Atlantic, elasmobranchs are a common bycatch in many fisheries, including demersal trawls, longlines, or gillnets and many countries do not have regulations or any control over the amount taken. In the Mid Atlantic, the Azores EEZ (Exclusive Economic Zone), small-scale fishing operations, artisanal and hook-and-line fishing methods are responsible for part of local total landed elasmobranch biomass, although some species are specifically focused and severely harvested by international large-scale fleets. This work provides a review and analysis of the commercial elasmobranch fisheries in the Azores EEZ, and its evolution over the last two decades, highlighting management priorities, taking into account the Northeast Atlantic elasmobranch fisheries status. In the Mid-Atlantic, elasmobranch fisheries mainly target 4 species, that are usually landed as bycatch: the tope shark (Galeorhinus galeus) and the thornback ray (Raja clavata), captured mainly by local demersal artisanal fisheries, the blue shark (Prionace glauca) and the shortfin mako shark (Isurus oxyrinchus) captured by a more industrialised fleet, including those from foreign nations. Considering elasmobranchs life history traits and fishery history, caution is advised in the development of a management strategy focusing on these species, considering the Northeast Atlantic context and regional, local and national interests. 相似文献
689.
690.
McEwen et al. (McEwen, A.S., Preblich, B.S., Turtle, E.P., Artemieva, N.A., Golombek, M.P., Hurst, M., Kirk, R.L., Burr, D.M., Christensen, P. [2005]. Icarus 176, 351-381) developed a useful test for the internal consistency of crater-count chronometry systems. They argued that certain multi-kilometer, fresh-looking martian craters with prominent rays should be the youngest or near-youngest craters in their size range. The “McEwen et al. test” is that the ages determined from crater densities of the smallest superimposed craters (typically diameter D ∼ 5-20 m) should thus be comparable to the expected formation intervals of the host primary. McEwen et al. concluded from MOC data that crater chronometry failed this test by factors of 700-2000. We apply HiRISE and other imagery to eight different young craters in order to re-evaluate their arguments. We use existing crater chronology systems as well as the reported observed production rate of 16 m craters (Malin, M.C., Edgett, K., Posiolova, L., McColley, S., Noe Dobrea, E. [2006]. Science 314, 1573-1557; Hartmann, W.K., Quantin, C., Mangold, N. [2007]. Icarus 186, 11-23; Kreslavsky [2007]. Seventh International Conference on Mars, 3325). Every case passes the McEwen et al. test. We conclude that the huge inconsistencies suggested by McEwen et al. are spurious. Many of these craters show evidence of impact into ice-rich material, and appear to have ice-flow features and sublimation pits on their floors. As production rate data improve, decameter-scale craters will provide a valuable way of dating these young martian geological formations and the processes that modify them. 相似文献