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941.
Bo Jing Qingzhong Li Baoan Gong Ran Li Zhenbo Liu Wenzuo Li Jianbo Cheng Jiazhong Sun 《International journal of quantum chemistry》2012,112(5):1491-1498
An ab initio computational study of the dual functions of C?S group in the M2C?S ··· HCN (M = H, F, Cl, Br, HO, H3C, H2N) complex has been performed at the MP2(Full)/aug‐cc‐pVTZ level. The C?S group can act as both the electron donor and acceptor, thus two minima complexes were found for each molecular pairs. The interaction energy of hydrogen bond in the F, Cl, or Br substituted complexes is less negative than that in the corresponding H2CS one, while the interaction energy of the σ‐hole interaction is more negative. The OH substitution weakens the hydrogen bond, whereas the H3C and H2N substitution strengthens it. The σ‐hole interaction in the HO, H3C, and H2N complexes is very weak. The substitution effect has been understood with electrostatic induction and conjugation effects. The energy decomposition analysis has been performed for the halogen‐substituted complexes. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012. 相似文献
942.
以原子类型电拓扑状态指数(ETSI)有效表征了135 个多氯二苯并噻吩(PCDT)和135 个多氯二苯并噻吩砜(PCDTO2)的分子结构, 应用基于预测的变量选择与模型化(VSMP)方法建立PCDT 和PCDTO2 化合物在DB-5 气相色谱柱上的气相色谱保留指数(RI)与分子结构(ETSI)的定量相关模型, 模型的相关系数r2 分别为0.9939 和0.9729, LOO 交叉验证相关系数 q2 分别为0.9921 和0.9692. 为验证模型稳定性和预测能力, 应用17 个PCDT 和PCDTO2 训练集样本构建的QSRR 模型的r2 分别为0.9959 和0.9783, LOO 交叉验证相关系数 q2 分别为0.9921 和0.9740, 说明模型具有良好的稳定性. 以此模型预测外部8 个检验集及110 个预测集的RI 值, 8 个检验集样本的结果表明训练集模型具有良好预测能力. 相似文献
943.
采用量子化学MM+和AM1方法计算聚甘油和脂肪酸多聚甘油酯的分子结构参数,然后用逐步线性回归方法建立脂肪酸多聚甘油酯HLB值的定量结构性质(QSPR)模型,所得的预测模型中包含四个参数(单位质量分子所含氧原子数Xo、生成热ΔfHm、电子能Ee和水合能Eh),预测值及外部检验的复相关系数(R2)和标准偏差(SD)分别为0.9553、0.73722和0.9678、6.34426。结果表明,量子化学方法计算简单,对脂肪酸多聚甘油酯结构的表征能力较强,所建QSPR模型具有能较好的预测能力和较强的稳健性,并在一定程度上阐明了脂肪酸多聚甘油酯分子结构与性能之间的关系。 相似文献
944.
硼酰化钴中硼的快速测定 总被引:1,自引:1,他引:1
硼酰化钴中硼的测定采用EDTA作为钴的络合掩蔽剂,消除了钴对测定硼的影响。同时改用溴甲酚绿-甲基红-酚酞三元混合指示剂作为测定硼的指示剂,使滴定终点灵敏、准确。建立了一种测定硼酰化钴中硼含量的简便、快速的分析方法。 相似文献
945.
A scheme has been proposed to classify valence bond(VB) wave functions for the calculations of ground and excited states,according to the symmetry properties of one-electron orbitals which are involved in the construction of VB wave functions.This scheme is illustrated by the examples of BeH and BH.Ab initio VB computations of these two test molecules in combination with the present classification scheme give reliable results.For example,calculation results show that the state C2∑ of BeH is stable,with the bonding energy 0.87 eV and bond length 0.238nm,which are in good agreement with those obtained by Gerratt et al.The bonding features of ground and low-lying excited states of BeH and BH are discussed. 相似文献
946.
947.
Pan Fusu Zeng Yi Xie Hui Xiong Rui Yu Zuxing Tang Wufeng Shi Jing Mo Shaobo 《化学物理学报(中文版)》2005,18(5):793-797
The core-level X-ray photoelectron emission spectra of the quasi-one dimensional spin 1/2 antiferromagnetic system Sr14-xCaxCu24O41(x=0, 3.5, 6, 7, 8.4) were measured. The main peak of Cu2p3/2 was about 933.8 eV, and the full width of half maximum height was about 3.3 eV. Simulation of Cu2p3/2 by XPSPEAK41 shows that the percents of Cu2+ and Cu3+ in Sr14Cu24O41 are 92.13% and 7.87%, no obvious change to Cu2p core-level is observed by the partial substituting Ca for Sr, and the average valence of Cu in this system is estimated to be 2.08. The main peak of O1s is about 531.0 eV, and the weak shoulder toward the low binding energy direction can be considered as the contribution of Ca-O bond. The binding energies of Ca2p3/2 and Sr3d5/2 indicate that their valence in this system are both +2, without mixed valence. 相似文献
948.
Zaifa Pan Lili Wang Weimin Mo Chen Wang Wei Hu Juanjuan Zhang 《Analytica chimica acta》2005,545(2):218-223
A new application of pyrolytic methylation was developed to determine benzoic acid in soft drinks by gas chromatography (GC) without using any pretreatment procedures and special pyrolyzer. With the on-line pyrolytic methylation by tetramethylammonium hydroxide (TMAH), benzoic acid was converted into its corresponding methyl ester in the injector at 280 °C. Thus, samples containing benzoic acid could be well determined by direct-injection in GC on the medium polar stationary phase column. To obtain optimum methylation conditions, important factors were investigated and then applied to the following experiments. The results were obtained as following: 280 °C as reaction temperature, 2:1 as the proportion of TMAH to benzoic acid. The storage time of mixed solution had no obvious effect on the area of benzoic acid methyl ester peak. With the p-xylene as an inter-standard, GC behaviors were investigated under these optimum conditions. The linear range achieved for benzoic acid was 1-10,000 mg/l with the correlation coefficient of 0.9985. The precision was quite high with the R.S.D. of 2.8% and the limit of detection reached 0.1 mg/l. The potential of the proposed method was assessed by applying it to the determination of benzoic acid in soft drinks. The results obtained coincided with the statement on the labels and all of the detected data were below the maximum permitted concentration of the European Union Legislation. This on-line pyrolytic methylation technique was proved to be simple to implement, sensitive and selective. 相似文献
949.
Formation and Oxidation of Hydrogen Molybdenum Bronze on Platinum Electrode in Sulfuric Acid Solution 总被引:2,自引:0,他引:2
Jin LU Jun Hua DU Wei Shan Li Jia Mo FUDepartment of Chemistry South China Normal University Guangzhou State Key Laboratory of Organic Geochemistry Guangzhou Institute of Geochemistry ChineseAcademy of Sciences Guangzhou 《中国化学快报》2004,15(6):703-706
Hydrogen molybdenum bronze (HxMoO3) can be electrodeposited on platinum and oxidized in two steps to the hydrogen molybdenum bronze with less amount of hydrogen HyMoO3 (y相似文献
950.
Zhang L Yu JC Mo M Wu L Li Q Kwong KW 《Journal of the American Chemical Society》2004,126(26):8116-8117
Oriented films of nickel sulfide nanostructures, ranging from hierarchical dendrites to nanobelts and nanorods, were hydrothermally grown on Ni foils. This approach has proven to be a general method for preparing nanostructured metal chalcogenides films on corresponding metal foils. 相似文献