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851.
This paper combines the climatological and societal perspectives for assessing future climatic extremes over Kangasabati River basin in India using an ensemble of four high resolution (25 km) regional climate model (RCM) simulations from 1970 to 2050. The relevant extreme indices and their thresholds are defined in consultation with stakeholders and are then compared using RCM simulations. To evaluate the performance of RCM in realistically representing atmospheric processes in the basin, model simulations driven with ERAInterim global re-analysis data from 1989 to 2008 are compared with observations. The models perform well in simulating seasonality, interannual variability and climatic extremes. Future climatic extremes are evaluated based on RCM simulations driven by GCMs, for present (1970–1999) and for the SRES A1B scenario for future (2021–2050) period. The analysis shows an intensification of majority of extremes as projected by future ensemble mean. The study suggests that there is a marked consistency in stakeholder observed changes in climate extremes and future predicted trends. 相似文献
852.
The kinetics of hydrogen atom abstraction reactions of HFE-227pc by OH and Cl was studied by ab initio method. The structural optimization and frequency calculation of the titled compound and the species formed during the abstraction reactions were performed with density functional theory using hybrid meta density functional MPWB1K with 6–31?+?G(d,p) basis set. The energy of the species was further refined by making a single point energy calculation at G3B3 level of theory. The standard enthalpies of formation of reactant and the radical formed after H-atom abstraction was calculated using isodesmic method. The rate constants of abstraction reactions were calculated using Conventional Transition State Theory (CTST) and were found to be 1.5?×?10?15 and 0.53?×?10?16 cm3molecule?1 s?1 for OH and Cl respectively. The calculated value for the abstraction by OH is close to the experimental value of 2.26?×?10?15 cm3molecule?1 s?1 whereas the same for Cl is found to be about five times lower than that of 2.70?×?10?16 cm3molecule?1 s?1. The theoretical studies yielded the enthalpies of formation and the rate constants that are vital in determining the lifetime of HFE-227pc. 相似文献
853.
This paper investigates the motion of a test particle around the triangular equilibrium points under the effects of radiation pressure of the second primary and its Poynting–Robertson (P–R) effect when the first primary is an oblate spheroid. It is seen that triangular points are influenced by the presence of these parameters: radiation pressure from the secondary and the incidental P–R effect and the oblateness of the first primary. The linear stability of the problem is studied and applied to the binary system RXJ 0450.1-5856, the triangular points are unstable due to positive roots in the Lyapunov sense when P–R effect is considered as against their conditional stability in the absence of P–R drag effect. 相似文献
854.
This paper studies the motion and orbital stability of the infinitesimal mass in the vicinity of the equilateral (triangular) Lagrangian points of the elliptic restricted three body problem, considering photo gravitational effects of both the primaries. The stability of the triangular points is studied under the effects of radiating primaries around the binary system (Achird, Luyten, αCen AB, Kruger-60, Xi-Bootis); using simulation technique by drawing different curves of zero velocity. 相似文献
855.
D. Dwivedee B. Nayak M. Jamil L. P. Singh R. Myrzakulov 《Journal of Astrophysics and Astronomy》2014,35(1):97-106
In this work, we study the evolution of primordial black holes within the context of loop quantum cosmology. First we calculate the scale factor and energy density of the Universe for different cosmic era and then taking these as inputs, we study evolution of primordial black holes. From our estimation it is found that accretion of radiation does not affect evolution of primordial black holes in loop quantum cosmology. We also conclude that due to slow variation of scale factor, the upper bound on initial mass fraction of presently evaporating PBHs are much greater in loop quantum cosmology than the standard case. 相似文献
856.
We have examined the effects of oblateness up to J 4 of the less massive primary and gravitational potential from a circum-binary belt on the linear stability of triangular equilibrium points in the circular restricted three-body problem, when the more massive primary emits electromagnetic radiation impinging on the other bodies of the system. Using analytical and numerical methods, we have found the triangular equilibrium points and examined their linear stability. The triangular equilibrium points move towards the line joining the primaries in the presence of any of these perturbations, except in the presence of oblateness up to J 4 where the points move away from the line joining the primaries. It is observed that the triangular points are stable for 0 < μ < μ c and unstable for \(\mu_{\mathrm{c}} \le \mu \le \frac {1}{2},\) where μ c is the critical mass ratio affected by the oblateness up to J 4 of the less massive primary, electromagnetic radiation of the more massive primary and potential from the belt, all of which have destabilizing tendencies, except the coefficient J4 and the potential from the belt. A practical application of this model could be the study of motion of a dust particle near a radiating star and an oblate body surrounded by a belt. 相似文献
857.
We analyze in situ measurements of the solar wind velocity obtained by the Advanced Composition Explorer (ACE) and the Helios spacecraft during the years 1998?–?2012 and 1975?–?1983, respectively. The data mainly belong to solar cycles 23 (1996?–?2008) and 21 (1976?–?1986). We used the directed horizontal-visibility-graph (DHVg) algorithm and estimated a graph functional, namely, the degree distance (D), which is defined using the Kullback–Leibler divergence (KLD) to understand the time irreversibility of solar wind time-series. We estimated this degree-distance irreversibility parameter for these time-series at different phases of the solar activity cycle. The irreversibility parameter was first established for known dynamical data and was then applied to solar wind velocity time-series. It is observed that irreversibility in solar wind velocity fluctuations show a similar behavior at 0.3 AU (Helios data) and 1 AU (ACE data). Moreover, the fluctuations change over the phases of the activity cycle. 相似文献
858.
We show that the solutions obtained by Lorenz-Petzold (1982) are special cases of the solutions given by us (1985b). We also show that the observations made by Lorenz-Petzold (1985a) about the solution given by Roy and Narain (1985a) are not correct. 相似文献
859.
For half-space (Z>0), homogeneous, collisonal and warm plasma, the expressions for fields and penetration depth δ/δ e (in the unit of ion collisionless cold plasma penetration depth, i.e., when v i =0, υ0i =) are derived and discussed numerically. It is concluded that the propagation of transverse waves is only slightly affected by the ion collisions and the applied magnetic field when the plasma frequence is greater than the wave frequency (ω pe >ω). For the case of ω pe ≤ω, the damping of the wave is not affected by the changes in the ion collision frequency and the ion temperature. However, in this case, the propagation of the wave is drastically affected by the applied magnetic field and the wave damps quickly as the magnetic field strength or the gyrofrequency (Ω e ) increases. 相似文献
860.
Ng. Ibohal Singh 《Astrophysics and Space Science》1988,148(2):199-205
A slow rotation perturbation of Robertson-Walker universes filled with perfect fluid has been investigated. It is found that the unit-four vector of perfect fluid hasno angular velocity in the perturbed cosmological models. The slow rotation which is related to the dragging of the local inertial frames, is compatible only with the cases of positive and negative curvatures of the cosmological universe. The intrinsic velocity vector field of the Universe isexpanding as well asshearing. 相似文献