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991.
992.
E. O. Frind E. A. Sudicky S. L. Schellenberg 《Stochastic Environmental Research and Risk Assessment (SERRA)》1987,1(4):263-279
The migration of contaminants in heterogeneous aquifers involves dispersive processes that act at different scales. The interaction of these processes as a plume evolves can be studied by micro-scale modelling whereby two scales, a local- or micro-scale and an aquifer- or macro-scale, are covered simultaneously. Local-scale dispersive processes are represented through the local dispersion coefficient in the transport equation, while large-scale dispersion due to heterogeneities is represented through the resolution of the flow field and the diffusive exchange between streamtubes. The micro-scale model provides both the high degree of resolution compatible with local-scale processes, and the extent required for the approach to asymptotic conditions, using grids of up to a million nodal points. The model is based on the dual potential-streamfunction formulation for flow, and the transport problem is formulated in a natural coordinate system provided by the flownet. Simulations can be used to verify stochastic theories of dispersion, without the restrictive assumptions inherent in the theory. For the two-dimensional case, results indicate convergence of the effective dispersivity to the theoretical macrodispersivity value. Convergence takes place within a travel distance of about 50 correlation lengths of the hydraulic conductivity field. However, the approach taken to asymptotic conditions, as well as the macrodispersivity value, may differ for different realizations of the same medium. The influence of early-time events such as plume splitting on the asymptotic convergence remains to be investigated. 相似文献
993.
赵勇胜 《吉林大学学报(地球科学版)》1987,(1)
文章指出不考虑地域、条件,一律采用《工业“三废”排放试行标准》的不合理性。提出了用负荷控制来代替目前采用的污染质排放的浓度控制、总量控制,并从石家庄市地下水污染现状出发,建立了以该市地下环境系统最大限度容纳污染质为目标的线性最优化模型;得出该市防止地下水污染的排放浓度;求得了污水允许渗入量区间和地下水开采模数区间。 相似文献
994.
本文介绍了模糊综合评判法在铀矿成矿预测中的应用。该法可定量地分析预测区的地质信息,综合多种成矿因素的作用,以达到分析预测区成矿远景的目的。其步骤是:将整个预测区划分为若干子区单元,作为评判对象;根据预测区的特殊性及地质成矿过程的一般性,确定出影响成矿的主要因素,组成评判因素集;计算每个子区单元在每个因素上对“成矿”的隶属度,确定评判矩阵;选用加权平均等3个评判函数,用二次评判的方法进行模糊综合评判,得到评判结果,最后对评判结果择优,划分出三级成矿远景区。 相似文献
995.
~(218)Po法寻找隐伏铀矿体初见成效 总被引:2,自引:0,他引:2
本文介绍了一种寻找隐伏铀矿体的快速测氡方法,即~(218)Po法。作者叙述了该法的工作原理、特点以及找矿效果,并阐述了~(218)Po法寻找隐伏铀矿体的可能性。最后着重叙述了~(218)Po法测量结果的解释方法。通过野外试验,作者认为:~(218)Po法不仅可以寻找隐伏铀矿体,而且能够定量预测盲矿体的埋藏深度与规模。 相似文献
996.
The arrival time difference for the AB branch of PKP from deep Tonga earthquakes is constant over years with a standard deviation
of ±0.05 seconds at seismographs located 10 to 50 km from each other. If published travel time curves are used to calculate
the relative residuals of PKP the standard deviation from the constant mean is improved by approximately 0.01 seconds for
AB branch data. For the BC branch, standard deviations of relative travel times of ±0.06 seconds are reduced to less than
±0.05 seconds by calculating relative residuals. We conclude that changes of crustal transit time forP-waves could be resolved, based on careful PKP arrival time measurement at two or more neighboring stations if the changes
exceed 0.05 sec and last for more than one year. The conditions for achieving this result are that PKP from Tonga earthquakes
is clearly recorded, and that time-keeping is accurate. The data on which these conclusions are based were obtained from the
Graefenberg seismograph array, which is located in West Gemany and consists of 13 stations separated by distances of 10 km
to 100 km. We propose that relative arrival times of PKP from Tonga could be used in the Mediterranean - Middle East area
to search for precursory travel time changes before large earthquakes. 相似文献
997.
地下水开采—地面沉降模型研究 总被引:27,自引:5,他引:22
本文建立三维流支--一维非线性固结地面沉降模型,在混合井流,降雨滞后补给,初始水头形成,人为边界刻画,水流-固结耦合及软土层固结滞后于地下水开采层水头变化等方面有所改进,所建模型用于苏州市,模拟出若干地面沉降重要特征,地面沉降中心偏离地下水漏斗中心,地面沉降动态滞后于地下水的水头动态,软土层渗透系数随固结过程的变化及头在软土层中的传递特征。 相似文献
998.
Intensive water sampling in conjunction with hydrological observations was conducted during three different rainstorms in order to understand the effects of rainfall events on the temporal variation of streamwater chemistry in a small headwater forest catchment. Concentrations of Na+ and SO42? decreased as the discharge rate increased. Hydrograph separation of the components was made using the three‐component model based on the end‐members mixing analysis (EMMA). The three end‐members were:
- 1 the groundwater in the saturated zone that prescribes the chemistry of the baseflow;
- 2 the throughfall that dilutes the streamwater;
- 3 the groundwater in the transient saturated zone prescribed, which was dependent on the groundwater level.
999.
1000.
DIAGNOSTIC ANALYSIS AND VERIFICATION OF PREDICTION OF THE TROPICAL PACIFIC SEA SURFACE TEMPERATURE ANOMALIES
DURING 1997 ~ 1998 总被引:1,自引:1,他引:0
By comparing with ENSO events that ever happened in the history, the basic features and probable
causes of the anomalous sea surface temperature of the tropical Pacific Ocean during 1997 and 1998 have been
analyzed diagnostically. It is found that the 1997/1998 El Nino had significant abnormalities and peculiarities. It
differs from the previous El Ni?o events falling into the simple “eastern pattern” or “western pattern”. The
predictions of 1997/1998 El Ni?o event have also been tested with an intermediate ocean-atmosphere coupled
dynamic model. The results show that the skills of the 0~24 lead month forecasts for the warm event are all
above 0.5. The predictions of the mature phase and the later stages of the warm event are better than those of the
beginning phase. 相似文献