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981.
具有强占型优先权的不耐烦顾客的M/M/m/2k-m排队模型 总被引:2,自引:0,他引:2
首先给出了只有一类不耐烦顾客的M/M/m排队模型,其中顾客到达与服务都服从相互独立的泊松分布,顾客的耐心等待期限截止到服务开始前,并服从指数分布,最终得到了顾客丢失率及稳态下的队长分布。利用此结论研究了具有多个服务台,两类到达顾客的M/M/m/2k-m排队系统,其中第一类顾客对于第二类顾客具有强占型优先权,顾客的耐心等待时间即等待期限仍服从指数分布,两类顾客具有各自的等待轨道。采用矩阵分析的方法给出了两类顾客各自的稳态分布,并作了相应的性能分析。 相似文献
982.
������������״̬���������� 总被引:8,自引:5,他引:3
????????????????????????????????????????????????????????????????????????????????????????????????????????????????λ????????????????????????????????????????????????????????????????????????????????仯???????? 相似文献
983.
984.
A Study of Neutron Star Structure in Strong Magnetic Fields that includes Anomalous Magnetic Moments
Akira Iwamoto 《中国天文和天体物理学报》2003,3(4):359-374
We study the effect of strong magnetic fields on the structure of neutronstar. We find that if the interior field is on the same order as the surface field currently observed, then the influences of the field on the star‘s mass and radius arenegligible; if the field is as large as that estimated from the scalar virial theorem,then considerable effects will be induced. The maximum mass of the star will be increased substantially while the central density is greatly reduced. The radius of a magnetic star can be larger by about 10%~20% than a nonmagnetic star of the same mass. 相似文献
985.
986.
987.
The article takes as its point of departure the apparently contradictory findings in recent research about accident rates in shipping and IMO implementation records. It is argued here that although IMO conventions have probably greatly improved shipping safety, they cannot credibly be held to be the chief cause of reduced accident rates as claimed in a recent Marine Policy article, when the documented failures of flag state and port state implementation continue to leave vessels sailing with grave deficiencies. The present analysis posits and corroborates a cluster of linked tendencies that jointly undermine IMO implementation. The core problem is IMO’s weak connection to the national maritime administrations, leading to broadly discretionary practices, exacerbated by language difficulties. Adding new rules is no panacea, as new rules in some cases negatively affect the functioning of existing regulations, and sometimes seem motivated mainly to show political alertness. The structural weakness of the IMO/member state link is the core implementation problem that urgently needs to be dealt with if marine safety is to be improved. The concluding section proposes a reform to bring the IMO out of this conundrum and ensure effective implementation. 相似文献
988.
对2008年5—11月采集的广东流沙湾海域白腹小沙丁鱼(Sardinellaclupeoides)进行稳定碳、氮同位素比值的测定,分析比较了5个不同体长组的差异,并以此为基础推算其营养级.结果表明,流沙湾白腹小沙丁鱼的δ^13C值变化范围为一17.61%。一15.99%。,平均值为一16.59‰,与浮游动物的δ^13C均值(一17.27%0)较为相近.其6”N值变化范围为12.73%。~15.26%0,平均值为14.03%0,比浮游动物的6”N均值(10.56%0)高出3.47%0.5个体长组的8¨c、8”N平均值没有随着体长的增大而增大.由δ15N值推算出广东流沙湾海域白腹小沙丁鱼的营养级范围为2.24~3.25,平均值为2.76,符合其主要摄食浮游动物的食性. 相似文献
989.
990.
By comparison with the Earth-like planets and the large icy satellites of the Solar System, one can model the internal structure of extrasolar planets. The input parameters are the composition of the star (Fe/Si and Mg/Si), the Mg content of the mantle (Mg# = Mg/[Mg + Fe]), the amount of H2O and the total mass of the planet. Equation of State (EoS) of the different materials that are likely to be present within such planets have been obtained thanks to recent progress in high-pressure experiments. They are used to compute the planetary radius as a function of the total mass. Based on accretion models and data on planetary differentiation, the internal structure is likely to consist of an iron-rich core, a silicate mantle and an outer silicate crust resulting from magma formation in the mantle. The amount of H2O and the surface temperature control the possibility for these planets to harbor an ocean. In preparation to the interpretation of the forthcoming data from the CNES led CoRoT (Convection Rotation and Transit) mission and from ground-based observations, this paper investigates the relationship between radius and mass. If H2O is not an important component (less than 0.1%) of the total mass of the planet, then a relation (R/REarth)=ab(M/MEarth) is calculated with (a,b)=(1,0.306) and (a,b)=(1,0.274) for 10−2MEarth<M<MEarth and MEarth<M<10MEarth, respectively. Calculations for a planet that contains 50% H2O suggest that the radius would be more than 25% larger than that based on the Earth-like model, with (a,b)=(1.258,0.302) for 10−2MEarth<M<MEarth and (a,b)=(1.262,0.275) for MEarth<M<10MEarth, respectively. For a surface temperature of 300 K, the thickness of the ocean varies from 150 to 50 km for planets 1 to 10 times the Earth's mass, respectively. Application of this algorithm to bodies of the Solar System provides not only a good fit to most terrestrial planets and large icy satellites, but also insights for discussing future observations of exoplanets. 相似文献