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931.
Introduction of species evolutionary sequence into the quantitative biostratigraphy is a significant work, either for studying
biologic evolution or for making stratigraphic correlation and reconstructing geologic history. The quantitative biostratigraphy
is to determine biostratigraphic event sequences by using probabilistic analysis. The evolutionary sequence systematics can
efficiently ascertain species evolutionary sequences. Two methods have been proposed to determine the sequence of species-disappearance
events: (1) species extinction events can be closed by last occurrence events using quantitative biostratigraphic analysis;
(2) the duration of a species may be approximately replaced by the duration of its parent species. To combine these two methods
for determining the sequence of species disappearance is the best way up to now. A consulting standard sequence that consists
of the speciation sequence of Permian waagenophylloid corals and the biostratigraphic event sequence of other important fossils
in Permian is used as an example. The group spearman rank-correlation test is used to test the consulting standard sequence
by comparing four types of calculations and two kinds of sequences and to find abnormal events. Based on the found abnormal
events in the test, the consulting standard sequence is revised to deal with different conditions. Sequences of speciation
and species-disappearance, and species duration are determined. Application of species evolutionary sequence to quantitative
biostratigraphy can largely improve the quality of biostratigraphic event sequence. In stratigraphic correlation, furthermore,
event sequences have higher precision than range biozones. 相似文献
932.
933.
新疆及邻区大地构造编图研究 总被引:21,自引:5,他引:21
新疆及邻区大地构造1150万的编图范围为北纬34°~50°,东经72°~98°,面积约370×10 相似文献
934.
935.
In this paper, the definition of latitudinal density and density flattening of the level ellipsoid is given, and integral
formulas of latitudinal density for pole gravity and equator gravity are derived. According to the pole gravity condition
and equator gravity condition for the level ellipsoid, latitudinal density distribution function of the level ellipsoid is
obtained. It is proved mathematically that latitudinal density of the earth’s equator is larger than that of the pole, the
earth’s density flattening calculated preliminarily is 1/322, and hypothesis of the earth’s latitudinal normal density is
further proposed, so that theoretical preparation for studying the forming cause of the earth gravity in problems such as
continent drift, mantle convection, and submarine extension is made well. 相似文献
936.
937.
Abstract: 3–D velocity images of the crust beneath the northern margin of the North China Plate have been constructed using P-wave travel time residuals of the latest earthquakes, with the data supplied by Chinese seismic networks.
The seismic image results indicate that there is a lateral heterogeneity in the crust beneath the northern part of the North China block. The velocity images of the upper crust show features closely related to the tectonic features on the surface. It can be seen from these velocity images of the vertical sections, and from the horizontal slice images at depths of 11 and 16 km that there exist East-West and North-East structures. The images indicate that the juncture zone of basin–and–range terrain is between the blue-colored high–velocity block corresponding to the Yanshan mountain range that developed during the Yanshan period in northwest Beijing and the green low-velocity area corresponding to the North China basin in southeast Beijing (Fig. 5). The juncture zone between high-velocity and low–velocity, and EW and NE fault zones have significant ore-control effects. From the chart of epicenters in the northern region of North China, we find that the epicenters of earthquakes are almost entirely distributed within the NE strip. Almost all major earthquakes took place in the transition strip between the high and low-velocity zones in the crust. The distribution of epicenters also reflects the strikes of known NE–faults. From the image sections along the latitude, we find that in the area between 114.0 E –118.0 E , there is a blue high-velocity block standing upright from the Moho to the upper crust (Fig. 6), from which can be deduced that some materials such as magma moved upward from the upper mantle during the history of its geological development. 相似文献
The seismic image results indicate that there is a lateral heterogeneity in the crust beneath the northern part of the North China block. The velocity images of the upper crust show features closely related to the tectonic features on the surface. It can be seen from these velocity images of the vertical sections, and from the horizontal slice images at depths of 11 and 16 km that there exist East-West and North-East structures. The images indicate that the juncture zone of basin–and–range terrain is between the blue-colored high–velocity block corresponding to the Yanshan mountain range that developed during the Yanshan period in northwest Beijing and the green low-velocity area corresponding to the North China basin in southeast Beijing (Fig. 5). The juncture zone between high-velocity and low–velocity, and EW and NE fault zones have significant ore-control effects. From the chart of epicenters in the northern region of North China, we find that the epicenters of earthquakes are almost entirely distributed within the NE strip. Almost all major earthquakes took place in the transition strip between the high and low-velocity zones in the crust. The distribution of epicenters also reflects the strikes of known NE–faults. From the image sections along the latitude, we find that in the area between 114.0 E –118.0 E , there is a blue high-velocity block standing upright from the Moho to the upper crust (Fig. 6), from which can be deduced that some materials such as magma moved upward from the upper mantle during the history of its geological development. 相似文献
938.
939.
940.
1995年,我国大部地区降水正常或偏多,但季节分配不均。春季,北方干旱范围较大,陕、甘等省冬春夏连旱,旱情严重。汛期,江南及东北南部暴雨频繁,赣、湘、辽、吉等省发展严重洪涝。全国大部地区热量比较充足,但光照条件欠佳,部分地区作物遭受低温寡照或霜冻危害。登陆台风和热带风暴偏多,两广局地损失严重。部分地区遭受风雹或沙尘暴袭击。 相似文献