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111.
Oliver Wild Oliver V. Rattigan Roderic L. Jones John A. Pyle R. Anthony Cox 《Journal of Atmospheric Chemistry》1996,25(2):167-199
The Cambridge 2-D Eulerian model has been used to study the potential atmospheric distributions and lifetimes of a number of CFC replacement compounds and their degradation products. The study has focused on HFC 134a and HCFCs 123, 141b and 142b and the major products formed by their atmospheric degradation. The loss of these compounds and their products by hydroxyl radical attack, photolysis and in-cloud hydrolysis have been investigated. The study has shown that HCFCs 141b and 142b have sufficiently long lifetimes to enter the stratosphere in significant quantities, where degradation leads to an increase in the total stratospheric chlorine concentration. The study has also highlighted areas where further experimental work would be valuable, in particular characterisation of the product channels for the degradation reactions and determination of the removal rates of the products in the aqueous phase. 相似文献
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研究了大孔膦酸树脂对毒砂中主、次和痕量元素的吸附行为及洗脱条件,结合巯基棉和TBP柱分离技术,建立了两个分离流程。在J-A1160型多道直读光谱仪上实现了毒砂单矿物中包括主量元素Fe和As在内的20个元素测定。主量元素As和Fe的相对标准偏差(n为5~10)分别为1.03%和0.9%,其它元素在5%~11%范围。流程经实际试样分析验证,结果与化学法相符。 相似文献
115.
过量酸性铬蓝K隐色光度法测定铜的研究 总被引:2,自引:0,他引:2
在pH 4.0的微酸性介质中,酸性铬蓝K同Cu~(2+)形成稳定的红色络合物,用H_2O_2为隐色剂可以隐去过量显色剂的颜色,消除高色度背景的影响。络合物的最大吸收波长为540nm,摩尔吸光系数为1.6×10~4L·mol~(-1)·cm~(-1),Cu量在0~1.4μg/ml范围服从比尔定律。方法已应用于测定矿样中的Cu。 相似文献
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Richard Winterhalter Peter Neeb Dirk Grossmann Antje Kolloff Osamu Horie Geert Moortgat 《Journal of Atmospheric Chemistry》2000,35(2):165-197
Gas phase ozonolysis of -pinene was performedin a 570 l static reactor at 730 Torr and 296 K insynthetic air and the products were analysed by acombination of gas phase FTIR spectroscopy, HPLC andIC analyses of gas phase and aerosol samples,respectively. The reaction mechanism was investigatedby adding HCHO, HCOOH and H2O as Criegeeintermediate scavenger and cyclohexane as OH radicalscavenger. Main identified products (yields inparentheses) in the presence of cyclohexane as OHradical scavenger were HCHO (0.65 ± 0.04),nopinone (0.16 ± 0.04), 3-hydroxy-nopinone (0.15± 0.05), CO2 (0.20 ± 0.04), CO (0.030± 0.002), HCOOH (0.020 ± 0.002), the secondaryozonide of -pinene (0.16 ± 0.05), andcis-pinic acid (0.02 ± 0.01). The decompositionof the primary ozonide was found to yieldpredominantly the excited C9-Criegee intermediateand HCHO (0.84 ± 0.04) and to a minor extent theexcited CH2OO intermediate and nopinone (0.16± 0.04). Roughly 40% of the excitedC9-Criegee intermediate becomes stabilised andcould be shown to react with HCHO, HCOOH and H2O. The atmospherically important reaction of thestabilised C9-Criegee intermediate with H2Owas found to result in a nopinone increase of (0.35± 0.05) and in the formation of H2O2(0.24 ± 0.03). Based on the observed products,the unimolecular decomposition/isomerisationchannels of the C9-Criegee intermediate arediscussed in terms of the hydroperoxide and esterchannels. Subsequent reactions of the nopinonylradical, formed in the hydroperoxide channel, lead tomajor products like 3-hydroxy-nopinone but also tominor products like cis-pinic acid. A mechanismfor the formation of this dicarboxylic acid isproposed and its possible role in aerosol formationprocesses discussed. 相似文献
118.
抑制型离子色谱法同时测定水中锂和锶 总被引:2,自引:0,他引:2
对离子色谱法测定水中的锂、锶含量及其影响因素进行了研究。以甲烷磺酸为流动相,用IonPacCS12A阳离子色谱柱分离后,电导检测器同时测定矿泉水中锂和锶,其检出限分别为0.003mg/L和0.006mg/L。对Li^+和Sr^2+的离子色谱条件进行了优化,并对流动相的选择及干扰离子的影响进行了讨论。 相似文献
119.
A variety of mathematical expressions that describe changes over time (t) in the extent of amino acid racemisation (AAR, expressed as the ratio of d- to l-amino acid isomers or epimers) have been used in Quaternary geochronology. The integrated rate equation was first used to estimate fossil age from D/L but its geochronological utility is disadvantaged by uncertainties regarding the conformity of AAR in fossil protein to apparent reversible first-order kinetics for the entire reaction history. ‘Non-linear’ models have subsequently been used to relate D/L to t. The logarithmic equation successfully applied to Atlantic Coastal Plain research has not achieved widespread application, perhaps due to the regional calibration required if sensitivity to temperature is to be modelled, or the difficulties encountered when extending the model to include fossils with D/L<0.1. Success producing a linear correlation between D/L transformed with a power function and t has seen this approach emerge as one of the most commonly applied in AAR geochronology in recent years. Like parabola curve fitting, which has been applied to trends in D/L versus t in a variety of fossils and geographic settings, power transformations may not be suitable for geochronological modelling during the latter stages of amino acid diagenesis. Several studies have demonstrated the utility of simple and contingent linear equations for relating D/L to t. Future research should aim to reduce reliance on independent calibration and explore the geochronological benefits of AAR in pools other than the total hydrolysable amino acids. 相似文献