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81.
82.
Summary The meaning of linear absorbing boundary conditions for periodic water waves in elliptical approaches is discussed. It is
found that the direction of propagation of the waves must be known for reliable boundary conditions and that the energy dissipation
of waves running parallel to a boundary in general cannot be modelled in the framework of a linear theory.
Work presented at the Euromech Colloquium 240 on ?Dispersive waves in dissipative fluids?, Bologna, August 30–September 2,
1988. 相似文献
83.
机载激光测深海水后向散射包络的频域分析 总被引:2,自引:0,他引:2
根据机载激光测深海水后向散射雷达方程,在机载激光测深系统典型参数情况下,详细分析了海水衰减系数、海水反照率、飞机高度以及光学接收系统全视场角对海水后向散射频谱的影响。得到了: 当衰减系数C 从0. 2/ m 变到0. 9/ m 时, 后向散射包络频谱将展宽236MHz ;当海水反照率ω从0. 1 变到0. 9 时,后向散射包络频谱将展宽220MHz ;机载激光测深系统接收视场角和飞机高度对系统探测到的海水后向散射包络频率无显著影响;当最小可探测功率Pb = 1. 56 ×10 - 10W 时,在典型的实验参数条件下后向散射包络的频率范围为0 < f< 5. 6 ×108Hz。 相似文献
84.
85.
提出了一种基于海洋流函数模型的双站高频地波雷达径向流生成矢量流算法.该算法避免了传统矢量合成法将径向流进行插值带来的误差,而且符合海洋动力学原理,生成的流场更接近实际分布.通过计算机仿真发现,流函数算法的容错、容差能力比矢量合成法更强.在径向流探测标准误差为10 cm.s-1时,新算法反演结果的均方根误差减小了约5 cm.s-1.应用到雷达实测数据中,与海流计实测结果比较表明,新算法比传统算法的平均误差减小了2 cm.s-1. 相似文献
86.
Summary Different ocean models with one or two layers having constant static stability and supporting constant-shear flows, whose
directions are allowed to change with depth, are examined in the frame-work of the linear nonzonal baroclinic stability theory
and in the absence of the β-effect. The analysis is reduced to solving a simple Sturm-Liouville boundary value problem in
one dimension. A fairly general dispersion relation is found which correctly reproduces several special cases analysed by
other authors. This relation shows a fair variety of possible behaviours for stability curves of two-layer models. The results
show that the presence of a nonplanar shear-flow may have profound consequences on the stability character of the stationary
geostrophic flow. In fact, it appears that the stability properties are strongly dependent on the propagation angle of the
disturbance so that wave numbers which appear stable in the usual zonal theory may result unstable on such a nonzonal flow
andvice versa.
Paper presented at the 1o Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 19–22, 1984, Rome. 相似文献
87.
88.
Summary The possibility that radar sea return observed using aKu band fan beam Doppler airborne scatterometer flown over crude oil artificial spills might have been back-scattered via the
second-order Bragg interaction is surmised. An attempt is made to justify the absence of the first-order Bragg term.
Riassunto Prendendo in considerazione l'effetto dei primi ordini di Bragg e sopprimendo il ter mine di ordine 1, si mostra come l'inesplicato andamento dell'eco del mare in presenza di film di spandimento, rilevato con radar doppler in bandaKu montato su aereo, coincida con misure effettuate altrove in presenza di analogo film. Si propone una teoria secondo cui l'assenza del primo ordine è dovuta ad una carenza dell'onda capillare pertinente.相似文献
89.
Summary A very sophisticated wave model has been applied to the western Mediterranean Sea. The results show the importance of local
effects that had not been taken into account by the input atmospheric model. The need is stressed for the use of local models
nested in the large-scale ones.
Paper presented at the IV Congresso del Gruppo Nazionale per la Fisica dell'Atmosfera e dell'Oceano, June 22–24, 1987, Rome. 相似文献
90.
Summary The role of the free surface on the stability of a wind driven, quasi-geostrophic ocean having an Ekman bottom layer is studied
analytically using a perturbative procedure. It is shown that the growth rate range of the developing disturbances is reduced
by an amount depending on the energetics of the free surface. In other words, the main free surface effect is to increase
the stability of the whole system if this is compared with the rigid-lid ocean model.
Riassunto Viene analizzato il ruolo della superficie libera nella stabilità di un oceano nell'approssimazione quasi-geostrofica, forzato dal vento ed interessato dallo strato di Ekman sul fondo. Nell'ambito di un approccio lineare, si dimostra che la presenza di detta superficie aumenta la stabilità del sistema quando la si confronta con quella di un oceano nell'approssimazione di ?rigid lid?.
Резюме Используя процедуру теории возмущений, аналитически исследуется роль свободной поверхности на устойчивость океана в квази-геострофическом приближении. Показывается, что главный эффект свободной поверхности сводится к увеличению устойчивости всей системы по сравнению с моделью океана в приближении ?жесткой крышки?.相似文献