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51.
52.
Toshio Fukushima 《Celestial Mechanics and Dynamical Astronomy》2009,105(1-3):245-260
In order to accelerate the numerical evaluation of torque-free rotation of triaxial rigid bodies, we present a fast method to compute various kinds of elliptic functions for a series of the elliptic argument when the elliptic parameter and the elliptic characteristic are fixed. The functions we evaluate are the Jacobian elliptic functions and the incomplete elliptic integral of the second and third kinds regarded as a function of that of the first kind. The key technique is the utilization of the Maclaurin series expansion and the addition theorems with respect to the elliptic argument. The new method is around 25 times faster than the method using the incomplete elliptic integral of general kind and around 70 times faster than the method using mathematical libraries given in the latest version of Numerical Recipes. 相似文献
53.
An introduction to the South China Sea throughflow: Its dynamics, variability, and application for climate 总被引:9,自引:0,他引:9
The South China Sea throughflow (SCSTF) involves the inflow through the Luzon strait and the outflow through the Karimata, Mindoro, and Taiwan straits. Recent studies have suggested that the SCSTF act as a heat and freshwater conveyor, playing a potentially important role in regulating the sea surface temperature pattern in the South China Sea and its adjoining tropical Indian and Pacific Oceans. In this introductory paper, we attempt to convey the progress that has recently been made in understanding the SCSTF. We first provide an overview of existing observations, theories, and simulations of the SCSTF. Then, we discuss its interaction with the Pacific western boundary current and Indonesian throughflow. Finally, we summarize issues and questions that remain to be addressed, with special reference to the SCSTF's dynamics, variability, and implication for climate. 相似文献
54.
A seismicity gap was observed in the early stage of the activity of the earthquake swarm which has been taken place in the northern part of the Aso caldera during January 1975. In the following stage, small earthquakes began to occur, until at last the largest earthquake occured within the seismicity gap. The b-value appreciably increased after the largest earthquake. The above-mentioned characteristics of this earthquake swarm may be a typical example of the fracturing phenomena in relatively heterogeneous rocks. From the estimation of the ultimate strain energy that can be stored up in the seismicity gap, it may be concluded that the above-mentioned largest earthquake took place by the release of ultimate strain energy stored within the seismicity gap. 相似文献
55.
Toshio Fukushima 《Journal of Geodesy》2006,79(12):689-693
By using Halley’s third-order formula to find the root of a non-linear equation, we develop a new iterative procedure to solve an irrational form of the “latitude equation”, the equation to determine the geodetic latitude for given Cartesian coordinates. With a limit to one iteration, starting from zero height, and minimizing the number of divisions by means of the rational form representation of Halley’s formula, we obtain a new non-iterative method to transform Cartesian coordinates to geodetic ones. The new method is sufficiently precise in the sense that the maximum error of the latitude and the relative height is less than 6 micro-arcseconds for the range of height, −10 km ≤ h ≤ 30,000 km. The new method is around 50% faster than our previous method, roughly twice as fast as the well-known Bowring’s method, and much faster than the recently developed methods of Borkowski, Laskowski, Lin and Wang, Jones, Pollard, and Vermeille. 相似文献
56.
T. Terasawa 《Planetary and Space Science》1979,27(4):365-384
a Fermi-type acceleration model is constructed to explain the origin of energetic protons (30 ~ 100 keV) which have been observed upstream of the bow shock. It is shown that the suprathermal protons (with energy of several keV) can be accelerated up to several tens of keV through the Fermi-type process in which the reflection at the shock front and the scattering in the upstream region are coupled. The efficiency of the scattering process is estimated by using the result of Barnes' quasilinear treatment of the wave excitation. The resultant energy spectrum and flux intensity () in 32 ~ 45.3keV) are consistent with the observation, and the softening of the energy spectrum observed in the dawn region can be explained by the decrease in the efficiency of the acceleration process in the dawn region due to the curvature of the bow shock and the reduction of shock strength. The spatial distribution of the flux predicted by the model is also consistent with the observation. In view of these consistencies the Fermi-type acceleration process is suggested as a possible candidate mechanism to explain the upstream protons although we do not intend to exclude other possibilities. 相似文献
57.
将中尺度非静力模式MM5中的积云参数化Grell方案作了改进,使它含有降水云的云水,即雨水含量,并用该模式对1998年6月29日08时-30日08时(北京时)和1998年7月1日08时-2日08时(北京时)发生在淮河流域的两次特大暴雨进行数值模拟研究,同时通过采用R-qr关系将TRMM/PR(Tropical Rainfall Measuring Mission/Precipitation Radar)得到的降水强度资料月计算出比含水量qr,然后用qv′=qv qr取代原模式中的比湿qv。结果表明将TRMM/PR资料加入模式后,由于PR雷达具有较高的空间分辨率,能够很好地反映中小尺度系统的空间结构,能够使湿度值接近实际,缩短了中尺度系统的发展时间,使得模拟出来的降雨强度、雨量中心位置以及雨带形状更接近实况。 相似文献
58.
59.
Yuko Soma Yukinori Tani Mitsuyuki Soma Hideo Mitake Ryo Kurihara Shinya Hashomoto Takahiro Watanabe Toshio Nakamura 《Journal of Paleolimnology》2007,37(2):163-175
Detailed depth profiles of photosynthetic pigments in a sediment core (G-12) collected at the BDP93 site, the Buguldeika saddle,
of south Lake Baikal, along with depth profiles of total organic carbon (TOC) and biogenic silica, were studied to elucidate
the temporal changes of phytoplankton assemblages in the lake during the past 28 kyr. In addition to the quantification of
carotenoids by high-performance liquid chromatography with photodiode-array detection (HPLC-PDA), steryl chlorin esters (SCEs)
were analyzed by HPLC-PDA, HPLC-mass spectrometry (LC-MS) and sterols in SCEs by gas chromatography–mass spectrometry (GC–MS)
to enrich the taxonomical information on the phytoplankton composition. Allochthonous input of organic matter from the Selenga
River resulted in the higher TOC contents in core G-12 than in a previously reported core (G-6) collected at another site
from the southern basin. The poorer correlation in core G-12 than in G-6 between TOC and chlorophyll-a-originating pigments, which are indicative of autochthonous production, also indicated a significant allochthonous input
at the site. The abundance of lutein among the carotenoids detected, and the good correlation of total chlorophyll a and b shows that green algae represented a significant portion of the phytoplankton, accompanying the diatoms at the G-12 site,
after the last glacial period. The presence of cryptomonads and cyanobacteria were confirmed from marker carotenoids in the
sediment core. GC–MS analysis of sterols in SCEs detected marker sterols of diatoms, green algae, chrysophytes and dinoflagellates.
The depth profiles of the measured indicators gave consistent features for temporal changes in phytoplankton assemblage at
the G-12 site of Lake Baikal after the last glacial maximum.
Notably, the profile of a chrysophyte-specific sterol in SCEs was consistent with the reported distribution of chrysophyte
cysts during the Holocene. The presence of phytoplankton, such as green algae, diatoms and chrysophytes, in Lake Baikal during
the late last glacial period was indicated by the analysis of sterols in SCEs.
Sedimentary carotenoids and sterols in SCEs were found to give complementary information about phytoplankton composition.
These molecular indicators allow us to reconstruct past lake phytoplankton assemblages responding to environmental changes
with a time resolution as high as age–depth relationship in sediments attainable at present. 相似文献
60.
The relationship between the relativistic electron bursts (0.3 ~ 1.0 MeV) observed in the magnetotail at X = ?20 ~ ?30 Re and the evolution of the structure of the magnetotail during substorms is investigated. It is found that the majority of the relativistic electron bursts are associated with the substorm activity and occurs inside the plasma sheet at the time of the local BZ-southward turning. It is suggested that these electrons are accelerated at the neutral line and trapped in the magnetic loop structure. 相似文献