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751.
天山-兴蒙钼矿带是中亚成矿域的重要组成部分,该成矿带主要呈近东西向分布;本文通过对天山-兴蒙钼矿带4个典型矿床Re-Os同位素精确定年,结合前人区域动力学背景的研究,揭示天山-兴蒙造山带钼矿床的成矿作用主要与岩浆侵入形成的花岗岩热液作用有关,并识别出兴蒙造山带3期岩浆活动、钼成矿作用和构造热事件;Re-Os定年结果揭示出晚古生代铜-钼矿床与俯冲-增生作用有关,三叠纪钼的成矿形成于西伯利亚板块与塔里木-华北克拉通碰撞背景下,而侏罗纪-早白垩世的钼成矿作用与古太平洋板块西向俯冲作用有关。 相似文献
752.
753.
Stable isotope paleoaltimetry has provided unprecedented insights into the topographic histories of many of the world’s highest mountain ranges. However, on the Tibetan Plateau (TP), stable isotopes from paleosols generally yield much higher paleoaltitudes than those based on fossils. It is therefore essential when attempting to interpret accurately this region’s paleoaltitudes that the empirical calibrations of local stable isotopes and the relations between them are established. Additionally, it is vital that careful estimations be made when estimate how different isotopes sourced from different areas may have been influenced by different controls. We present here 29 hydrogen isotopic values for leaf wax-derived n-alkanes (i.e., δDwax values, and abundance-weighted average δD values of C29 and C31) in surface soils, as well as the δD values of soil water (δDsw) samples (totaling 22) from Mount Longmen (LM), on the eastern TP (altitude ~0.8–4.0 km above sea level (asl), a region climatically affected by the East Asian Monsoon (EAM). We compared our results with published data from Mount Gongga (GG). In addition, 47 river water samples, 55 spring water samples, and the daily and monthly summer precipitation records (from May to October, 2015) from two precipitation observation stations were collected along the GG transect for δD analysis. LM soil δDwax values showed regional differences and responded strongly to altitude, varying from?160‰ to?219‰, with an altitudinal lapse rate (ALR) of?18‰ km?1 (R 2=0.83; p<0.0001; n=29). These δDwax values appeared more enriched than those from the GG transect by ~40‰. We found that both the climate and moisture sources led to the differences observed in soil δDwax values between the LM and GG transects. We found that, as a general rule, ε wax/rw, ε wax/p and ε wax/sw values (i.e., the isotopic fractionation of δDwax corresponding to δDrw, δDp and δDsw) increased with increasing altitude along both the LM and GG transects (up to 34‰and 50‰, respectively). Basing its research on a comparative study of δDwax, δDp, δDrw(δDspringw) and δDsw, this paper discusses the effects of moisture recycling, glacier-fed meltwater, relative humidity (RH), evapotranspiration (ET), vegetation cover, latitude, topography and/or other factors on ε wax/p values. Clearly, if ε wax-p values at higher altitudes are calculated using smaller ε wax-p values from lower altitudes, the calculated paleowaterδDp values are going to be more depleted than the actual δD values, and any paleoaltitude would therefore be overestimated. 相似文献
754.
755.
介绍该县堆积面滑坡和层面滑坡两种典型滑坡的发育特征,分析其形成条件和机理.在此基础上,利用分形分维理论,分析研究区水系特征对滑坡分布和发育特征的影响. 相似文献
756.
757.
The change in community diversity and structure of the indigenous, dominant, polycyclic aromatic hydrocarbon (PAH)-degrading bacterial genera, Sphingomonas and Mycobacterium, due to contamination in the environment is not very well known. A combination of PCR-DGGE with specific primers and a cultivation-dependent microbiological method was used to detect different populations of Sphingomonas and Mycobacterium in mangrove sediments. The structure of the entire bacterial community (including Sphingomonas) did not show a shift due to environmental contamination, whereas the diversity of Mycobacterium populations in mangrove sediments with higher PAH contamination increased from exposure between Day 0 and Day 30. The isolated Mycobacterium strains migrated to the same position as the major bands of the bacterial communities in Mycobacterium-specific DGGE. A dioxygenase gene system, nidA, which is commonly found in PAH-degrading Mycobacterium strains, was also detected in the more highly contaminated sediment slurries. The present study revealed that Mycobacterium species were the dominant PAH-degraders and played an important role in degrading PAHs in contaminated mangrove sediments. 相似文献
758.
板块构造成矿理论认为西昆仑叶尔羌河中下游地区属于Au、Cu及多金属矿成矿远景区,但因其野外地质条件恶劣,交通状况差,地质勘探极其困难而影响了找矿工作的深入开展,为此我们利用航天遥感技术的优势进行了找矿有利地段预测研究。在研究中首先对区域地质遥感影像特征进行了综合分析,并根据板块构造成矿理论对矿化作用进行了空间划分和成矿条件总结。在此基础上,通过成矿相关影像特征信息的提取,圈定出Au、Cu及多金属矿成矿有利地段。 相似文献
759.
Li ChuanXin Guo ZhaoJie Meng ZiFang Li HaiYan Zhang ZhiCheng Wu ChaoDong 《中国科学D辑(英文版)》2007,50(4):544-554
Analyses of rock-magnetic properties of Neogene sediments of the Taxihe section, northern Tianshan Mountains, show that the section can be classified into three categories including lacustrine facies, fluvial facies and alluvial facies, which correspond to the lower, middle and upper of the Taxihe section respectively. The magnetic minerals of the lacustrine facies may be affected by the process of weath- ering, lithogenesis and biolithogenesis besides the source of the sediments. The natural remanence intensities are between 10-3 A/m and 10-2 A/m. The minerals are dominated by magnetite and the high coercive magnetic mineral may be goethite. The magnetic grains are the mixture of PSD SD or SD SP. The natural remanence intensities of the strata of fluvial facies are between 10-2 A/m and 10-1 A/m, about ten times that of the lacustrine facies. The magnetic minerals are mainly magnetite and hematite, and the magnetic grains are mainly PSD. The characteristic remanence (ChRM) carriers are magnetites. In the alluvial facies, the natural remanence intensities are mostly less than 1×10-2 A/m. The magnetic minerals of the series are dominated by magnetite and hematite, almost the same as the fluvial facies. But the difference is that most of the stepwise demagnetization can reveal two components and the ChRM carriers are hematites. The magnetic grains are PSD in terms of the hysteresis parameters. 相似文献
760.
Two-dimensional tidal open boundary conditions of the M2 constituent in the Bohai and Yellow Seas(BYS) have been estimated by assimilating T/P altimeter data.During inversion,independent point(IP) strategy was used,in which several IPs on the open boundary is assumed,values at these IPs can be optimized with an adjoint method,and those at other grid points are determined by linearly interpolating the values at IPs.The reasonability and feasibility of the model are tested by ideal twin experiments.In the practical experiment(PE) after assimilation,the cost function may reach 1% or less of its initial value.Mean absolute errors in amplitude and phase can be less than 5 cm and 5°,respectively,and the obtained co-chart can show the character of the M2 constituent in the BYS.The results of the PE indicate that using only two IPs on the open boundary can yield better simulated results. 相似文献