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91.
花岗岩型碳酸钠质交代热液铀矿床蚀变带中的重矿物有明显的改造与叠加现象。随着矿物的解离,热液从围岩中获取了部分矿源。主要铀矿化是在热液连续活动的晚期,铀与金属硫化物共沉淀。本文就西北某花岗岩体在碳酸钠质热液作用下所发生的重矿物组合含量及主要重矿物性质的一系列变化,以及与此有关的铀的活化转移与沉淀阶段等问题进行讨论。 相似文献
92.
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.
93.
94.
Potential hyperaccumulation of Pb, Zn, Cu and Cd in endurant plants distributed in an old smeltery, northeast China 总被引:1,自引:0,他引:1
The absorption and accumulation of Pb, Zn, Cu and Cd in some endurant weed plant species that survived in an old smeltery
in Liaoning, China, were systematically investigated. Potential hyperaccumulative characteristics of these species were also
discussed. The results showed that metal accumulation in plants differed with species, tissues and metals. Endurant weed plants
growing in this contaminated site exhibited high metal adaptability. Both the metal exclusion and detoxification tolerance
strategies were involved in the species studied. Seven species for Pb and four species for Cd were satisfied for the concentration
time level standard for hyperaccumulator. Considering translocation factor (TF) values, one species for Pb, seven species
for Zn, two species for Cu and five species for Cd possessed the characteristic of hyperaccumulator. Particularly, Abutilon theophrasti Medic, exhibited strong accumulative ability to four heavy metals. Although enrichment coefficients of all samples were lesser
than 1 and the absolute concentrations didn’t reach the standard, species mentioned above were primarily believed to be potential
hyperaccumulators. 相似文献
95.
Brent B. Wolfe Matthew D. Falcone Ken P. Clogg-Wright Cherie L. Mongeon Yi Yi Bronwyn E. Brock Natalie A. St. Amour William A. Mark Thomas W. D. Edwards 《Journal of Paleolimnology》2007,37(2):221-231
Recent advances in sample preparation techniques and mass spectrometry have fostered more routine oxygen isotope analysis
of aquatic cellulose in lake sediment cores, a proxy for lake water oxygen isotope history. These methodological developments
have significantly increased the feasibility of incorporating this approach into high-resolution, multi-site, and multi-proxy
studies, which are frequently necessary to answer complex hydrological, hydroecological and hydroclimatic questions requiring
a paleoenvironmental perspective. Direct translation of lake sediment aquatic cellulose oxygen isotope composition into lake
water oxygen isotope composition offers appreciable opportunity for quantitative paleohydrological reconstructions, as evidenced
by studies conducted over the past 15 years that span Holocene and pre-historical timescales. 相似文献
96.
通过对低纬高原地区多个冰雹和暴雨个例的多方面的对比分析,发现冰雹和暴雨的发生在大气环境背景、大气层结、大气不稳定性及云图特征上既有一些相似之处,也存在一些明显的区别.研究发现,发生冰雹时,中纬度低槽较偏南,受北方天气系统影响明显;发生暴雨时,受热带系统影响明显,中纬度低槽稍偏北.在冰雹发生前,大气中层较干、低层较湿,但层结仍为较稳定的状态;在暴雨发生前,大气中、低层均较湿,层结为弱稳定状态.冰雹的发生要求下层大气气温相对较低,以使雹粒在溶化之前可到达地面,而暴雨的发生要求大气富含水汽.冰雹以冬春多见,夏季较少;暴雨以夏季较多,而冬春较少.与此对应,产生暴雨的强对流其对流强度要强于产生冰雹的,但对于同一季节发生的冰雹和暴雨,两者的对流强度是相近的. 相似文献
97.
An Experiment Using the High Resolution Eta and WRF Models to Forecast Heavy Precipitation over India 总被引:1,自引:0,他引:1
Y. V. Rama Rao H. R. Hatwar Ahmad Kamal Salah Y. Sudhakar 《Pure and Applied Geophysics》2007,164(8-9):1593-1615
In the present study using the Weather Research and Forecasting (WRF) and Eta models, recent heavy rainfall events that occurred
(i) over parts of Maharastra during 26 to 27 July, 2005, (ii) over coastal Tamilnadu and south coastal Andhra Pradesh during
24 to 28 October, 2005, and (iii) the tropical cyclone of 30 September to 3 October, 2004/Monsoon Depression of 2 to 5 October
2004, that developed during the withdrawal phase of the southwest monsoon season of 2004 have been investigated. Also sensitivity
experiments have been conducted with the WRF model to test the impact of microphysical and cumulus parameterization schemes
in capturing the extreme weather events. The results show that the WRF model with the microphysical process and cumulus parameterization
schemes of Ferrier et al. and Betts-Miller-Janjic was able to capture the heavy rainfall events better than the other schemes. It is also observed
that the WRF model was able to predict mesoscale rainfall more realistically in comparison to the Eta model of the same resolution. 相似文献
98.
几种Q矢量的比较 总被引:12,自引:1,他引:12
利用 1 991 - 0 7- 0 5T2 0— 0 6T2 0一次江淮梅雨锋暴雨过程实况资料 ,结合地面降水分布 ,从定性 (矢量场 ,即 Q)、定量 (散度场 ,即 2 · Q)的角度细致、具体地比较分析了准地转 Q矢量、半地转 Q矢量、非地转 Q矢量及湿 Q矢量的诊断特性。结果表明 :半地转 Q矢量诊断能力优越于准地转 Q矢量。非地转 Q矢量、湿 Q矢量诊断能力明显优越于准地转 Q矢量、半地转 Q矢量。准地转 Q矢量诊断能力最差 ;从定性的角度分析 ,非地转 Q矢量与湿 Q矢量诊断能力相差不大。但进一步定量分析发现 ,在整个梅雨锋暴雨过程中 ,湿 Q矢量的诊断能力大于其他 Q矢量 ;70 0 h Pa高度上各 Q矢量的矢量、散度辐合区较其在 850 h Pa和 50 0 h Pa上对降水反映更好 ,尤其是70 0 h Pa湿 Q矢量散度辐合区与降水区有非常好的对应关系。 相似文献
99.
The paper gives the distributions of the daily mean temperature of black body of satellite infrared
images from June 7 to 10, 1998 during HUAMEX and examines 14 meso-α-scale convective systems and a
number of meso-b-scale convective systems using the satellite infrared images at 1-h intervals. The mesoscale
convective systems on June 7 and 9, which resulted in severe rainstorm over the middle of Taiwan and the
estuary region of the Pearl River (Zhujiang R.), are emphatically analyzed. The serial development of mesoscale
convective systems is revealed by the distributions of the black body temperature of satellite infrared images. The
environmental conditions in which many mesoscale convective systems continuously occurred are diagnosed.
The visualizing tool, LiveView, displays the link between the upper and lower horizontal wind fields and the
vertical circulations and 3-dimensional trajectories of moist air motions, based on the data of objective analyses. 相似文献
100.
I.horoductionPleNorthwestPacificOceanisti1elnostfrequentlyaffeCtedareaoftropicalcyclone(TC).AboLIt36percentTCoftheworldoccurinffosarea[2],andthenumberofTCWhichlandedonChinawiti1n1akimumwindforcescalesoverlOisabout35percentofti1atintheeastemcoastalcoLUitriesofAsia[l].BothrainstormsandfloodsMide,theidriuenceofTCareheaVyinChina,suchastherainfalldePthof2749mm/3datXinliao,Taiwanandpeakdischargeof44,6oOm'/satHuanggo(55,42okn'),YalujiangRjver.Therefore,TCisanimportantfaCtorforflooddisas… 相似文献