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71.
The dynamics of two uncoupled distinct Chua circuits driven by a common direct current voltage is explored experimentally.
It was found that, with increasing current intensity, the dominant frequencies of these two Chua circuits will first vary
at different speeds, approach an identical value for a certain current intensity and then separate. Techniques such as synchronization
index and phase difference distribution were employed to analyze the phase coherence between these two Chua circuits. 相似文献
72.
本文应用401螯合村脂在合适酸度下吸着阳离子的性质,研究了对砷(Ⅲ)、(Ⅴ)、锑(Ⅲ)、铋(Ⅲ)、锡(Ⅱ)、锗(Ⅳ)、硒(Ⅳ)的吸着行为;讨论了氢化发生-分光光度法测砷时二甲基甲酰胺-乙醇胺(简称DMF)对砷化氢的吸附问题。建立了一种用螯合树脂分离铜(Ⅱ),铅(Ⅱ)、铬(Ⅲ)、镍(Ⅱ)、锑(Ⅲ)铋(Ⅲ)、锡(Ⅱ)、硒(Ⅳ)等于扰离子、用硼氢化物还原测定碑的新方法。本法可用于测定地面水、地下水、工业废水及工业废渣浸出液等环境水样中的砷。 相似文献
73.
An efficient enantioselective approach to chiral dihydropyrones has been developed by the hetero-Diels-Alder (HDA) reactions of (E)-4-methoxy-2-trimethylsiloxy-penta-1,3-diene (diene 1) with aldehydes and pyruvates. It has been found that the readily accessible (R)-BINOL-Ti(OiPr)(4) (1.1:1) complex was a very effective catalyst for this reaction. Aromatic, heteroaromatic, conjugated, and aliphatic aldehydes afforded the corresponding products in moderate to high isolated yields (up to 99%) with excellent enantioselectivities (up to 99% ee). The first example of highly enantioselective synthesis of 2,2,6-trisubstituted dihydropyrones by the catalytic reaction of diene 1 with pyruvates was reported. The isolated intermediates indicated that this asymmetric HDA reaction proceeded in a Mukaiyama aldol pathway. On the basis of the absolute configurations of the products, a possible mechanism was proposed. Moreover, the catalytic system could be used to synthesize a series of enantioenriched beta-hydroxyketones 4. Finally, this methodology was successfully applied for the one-step synthesis of the important natural product (R)-(+)-Hepialone with 88% isolated yield and 94% enantioselectivity. 相似文献
74.
稀土环己烷酸配合物合成及振动光谱研究 总被引:2,自引:0,他引:2
The solid state complexes of trivalent lanthanid, yttrium and scandium with cyclohexane carboxylic acid have been isolated and characterized by IR and Raman spectroscopy. It was found that there are only chelated carboxylate groups in the scandium complex and that there are the chelated, bridged and chelate-bridged carboxylate groups in other rare earth complexes. The former is a mononuclear complex and the latter is a polynuclear polymer. The RE—O coordinate bonds possess the characters of convalent ionic bond. 相似文献
75.
76.
Twelve 5, 10, 15, 20‐tetra[(4‐alkoxy‐3‐ethyloxy)phenyl]porphyrin hydroxylanthanide complexes Ln[(C n OEOP)4P](OH) (n?=?12, 14, 16;Ln?=?Tb, Dy, Er, Yb) and three ligands have been synthesized and their composition, structure and spectral properties studied. Their liquid crystalline behaviour is also presented. Differential scanning calorimetry and polarizing optical microscopy reveal that all exhibit a discotic liquid crystalline phase. X‐ray diffraction shows that the mesophase is a hexagonal columnar, Colh. The lanthanide ion, which is coordinated to the four nitrogen atoms of the porphyrin and to the oxygen atom of the hydroxyl group, is out of the porphyrin molecular plane. All the complexes are stable below 200°C and undergo complete decomposition at 800°C. The fluorescence quantum yields of the lanthanide complexes are much lower than those of the corresponding ligands. The electrochemical studies show that the redox potentials do not change on varying the chain length. 相似文献
77.
78.
79.
采用便携式拉曼光谱仪对新鲜乳腺正常组织、良性组织和恶性组织进行检测,通过稳健统计方法对拉曼光谱数据进行分析处理,建立乳腺组织拉曼光谱标准图谱,根据标准图谱特征峰归纳3类组织的主要区别和特征.在3类乳腺组织中,正常组织有明显的脂类特征峰(1078,1297,1437,1653,1746 cm-1),而在良性和恶性组织中则出现了较明显的蛋白特征峰(1259,1530,1650 cm-1),正常、良性和恶性组织的主要区别集中在1340和1534 cm-1处,应归属为蛋白和类胡萝卜素,这一结果并不能由经典统计方法得出.基于稳健统计建立的新鲜乳腺组织拉曼光谱标准图谱为构建数学模型来鉴别乳腺病灶的性质奠定了基础. 相似文献
80.
在微通道内表面通过化学吸附组装上银纳米粒子制成了微通道表面增强拉曼散射(SERS)器件,其对常见探针分子罗丹明6G(R6G)和4-巯基吡啶(4-MPY)的最低检测浓度分别达到10-11和10-8mol/L,说明其具有很好的增强效果.用该器件对2种有害化学药品进行了检测,三聚氰胺的最低检测浓度可到10-6mol/L,而福美双的最低检测浓度可达到10-7mol/L,说明所制备的微通道器件可用于对有害化学品的检测.微通道SERS器件具有体积小、取样少、制备简单、能够进行现场实时动态检测等特点,具有广阔的应用前景. 相似文献