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A study on the synthesis of La1−xAgxMnO3+δ (x = 0, 0.2) using a microwave process (MWhyd) has been carried out by comparing the heating time and reaction temperature with the same factor under conventional thermal process (CHhyd). Experiments have been conducted using the hydrothermal method at medium pressure (T = 200 °C, P = 20 atm) followed by a thermal treatment of the precursor at 700 °C (10 h).Structural and physico-chemical properties of the catalysts were investigated using X-ray diffraction (XRD), BET sorption, temperature-programmed reduction or desorption, mass spectrometry (TPR-MS and TPD-MS), and X-ray photoelectron spectroscopy (XPS). While CHhyd and MWhyd powder catalysts exhibited the same XRD patterns indexed as pure perovskite structure, their surface physico-chemical properties were found to be strongly influenced by the preparation method. The effect of the nature of oxygen species, their amount and mobility, evidenced by temperature programmed experiments, on the catalytic properties in methane combustion in the presence and in the absence of hydrogen sulphide has been studied. MWhyd-La0.8Ag0.2MnO3+δ catalysts were found to exhibit a much better performance in methane combustion together with higher resistance to sulphur poisoning than CHhyd catalysts. 相似文献
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Philip Eckert Prof. Dr. Michael G. Organ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(69):15751-15754
The impact of LiBr and ZnBr2 salts on the Negishi coupling of alkylZnBr and dialkylzinc nucleophiles with both electron-rich and -poor aryl electrophiles has been examined. Focusing only on the more difficult coupling of deactivated (electron-rich) oxidative addition partners, LiBr promotes coupling with BuZnBr, but does not have such an effect with Bu2Zn. The presence of exogenous ZnBr2 shuts down the coupling of both BuZnBr and Bu2Zn, which has been shown before with alkyl electrophiles. Strikingly, the addition of LiBr to Bu2Zn reactions containing exogenous ZnBr2 now fully restores coupling to levels seen without any salt present. This suggests that there is a very important interaction between LiBr and ZnBr2. It is proposed that Lewis acid adducts are forming between ZnBr2 and the electron-rich Pd0 centre and the bromide from LiBr forms inorganic zincates that prevent the catalyst from binding to ZnBr2. This idea has been supported by catalyst design as chlorinating the backbone of the NHC ring of Pd-PEPPSI-IPent to produce Pd-PEPPSI-IPentCl catalyst now gives quantitative conversion, up from a ceiling of only 50 % with the former catalyst. 相似文献
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Chunmei Zhang Zhijia Liu Yongming Li Qi Li Chaojun Song Zhuwei Xu Yun Zhang Yusi Zhang Ying Ma Yuanjie Sun Lihua Chen Liang Fang Angang Yang Kun Yang Boquan Jin 《Analytica chimica acta》2013
In this study, detection of staphylococcal enterotoxin A (SEA) in multi-matrices using a highly sensitive and specific microplate chemiluminescence enzyme immunoassay (CLEIA) has been established. A pair of monoclonal antibodies (mAbs) was selected from 37 anti-SEA mAbs by pairwise analysis, and the experimental conditions of the CLEIA were optimized. This CLEIA exhibited high performance with a wide dynamic range from 6.4 pg mL−1 to 1600 pg mL−1, and the measured low limit of detection (LOD) was 3.2 pg mL−1. No cross-reactivity was observed when this method was applied to test SEB, SEC1, and SED. It has also been successfully applied for analyzing SEA in a variety of environmental, biological, and clinical matrices, such as sewage, tap water, river water, roast beef, peanut butter, cured ham, 10% nonfat dry milk, milk, orange juice, human urine, and serum. Thus, the highly sensitive and SEA-specific CLEIA should make it attractive for quantifying SEA in public health and diagnosis in near future. 相似文献
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建立了在线固相萃取-液相色谱-串联质谱(online SPE-LC-MS/MS)测定蘑菇中毒患者尿液中痕量α -鹅膏毒肽的分析方法。样品经甲酸酸化的乙腈-甲醇(5:1,v/v)沉淀蛋白质,反相液液微萃取去除样品提取液中的有机溶剂,毒素经ODS微柱(5 mm×2.1 mm,5 μm)在线SPE净化,XBridgeTM BEH C18 色谱柱(150 mm×3.0 mm,2.5 μm)分离,MS/MS测定。采用基于定量环的快速阀切换技术作为在线SPE和LC-MS/MS模块的接口,使得两个分离模块互相独立,无论是流动相还是压力,都不会互相干扰,保证了系统的稳定性;在线系统的精准净化,有效消除了后续质谱检测的基质效应,确保了尿液中痕量水平α -鹅膏毒肽的定性定量检测。尿液中α -鹅膏毒肽在0.1~50 μg/L范围内线性关系良好,相关系数(r 2 )为0.9983;检出限(LOD)为0.03 μg/L;α -鹅膏毒肽的加标(0.1、2.0和20 μg/L)平均回收率为84.3%~91.7%,相对标准偏差(RSD)为3.8%~7.2%。体内鹅膏毒肽代谢迅速,生物基质中痕量水平毒素的检测是其中毒实验室鉴定的主要难题,通过实际样品检测,证明该法操作简单,准确、灵敏;溶剂沉淀蛋白质和反相液液微萃取去除有机相和脂溶性基质的简单操作,可以作为水溶性毒素在线SPE-LC-MS/MS检测时快速且有效的配套前处理方法;基于在线SPE精准净化技术,可以实现尿液中α -鹅膏毒肽的高灵敏度测定(LOD为0.03 μg/L),解决了中毒时患者体内痕量水平α -鹅膏毒肽定性确证的难题,部分患者α -鹅膏毒肽中毒实验室鉴定的时间可以扩展到90 h以上;同时,痕量水平的定量检测技术,可以为中毒后迅速代谢的α -鹅膏毒肽在体内的剂量反应关系研究提供可靠的技术支撑。 相似文献
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综述了国内外学龄前儿童铅中毒的危害和防治现状,针对目前健康教育对降低铅暴露有效性的研究结果并不理想,而且部分研究尚存在设计缺陷的情形,提出了健康促进对学龄前儿童预防和控制铅中毒的必要性和科学根据。 相似文献
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立得益片对铅中毒小鼠(生殖系统、脑、血液、心脏)促排铅的作用 总被引:4,自引:0,他引:4
研究了立得益片对铅中毒小鼠促排铅的作用。给小鼠腹腔注射醋酸铅溶液染毒 7d ,建立铅中毒模型后 ,灌胃给药不同剂量立得益片及阳性对照药物EDTA ,极谱法测定不同时间生殖系统、脑、血液、心脏中的铅含量 ,观察及统计立得益片对铅中毒小鼠上述各脏器的促排铅作用。结果表明 ,铅中毒小鼠给药 6、 1 3d后脑、心脏、血液中的铅含量明显下降 ,生殖系统中仅卵巢和子宫中的铅含量在给药 1 3d后 ,立得益片高剂量组与模型对照组有显著性差异 (P <0 0 1 )。提示立得益片对铅中毒小鼠血液及脏器有明显促排铅作用 ,降低机体的铅负荷且存在时效、量效关系 相似文献