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41.
Summary A capillary zone electrophoresis method for identification and determination of aesculin and aesculetin has been established
using borate-phosphate buffer containing 30% ethanol with on-column UV detection. A detailed investigation of the influence
of changes in borate concentration, pH, applied voltage, temperature and organic modifier was then carried out. For both aesculin
and aesculetin, a linear plot of migration time (MT) against borate concentration was obtained, and ln[measured peak area
(MA)] and lnMT both gave linear plots against ln(applied voltage) with correlation coefficient r>0.999, which also resulted
in a linear correlation between MA and MT (r≥0.9998) under varied voltage. Ethanol as organic modifier to the background electrolytes
helped in separating aesculin and aesculetin from other components in ash barks. The reproducibility with relative standard
deviation in MT and in normalized peak area(NA) and linearity based on NA against concentration were evaluated. Finally, the
method was successfully applied to monitor the quality of different ash barks and to compare the effect of sample preparation
on content of bioactive components in ash bark. Results indicate that CZE promises to be applicable to quality control of
traditional Chinese medicines containing aesculin and aesculetin. 相似文献
42.
在酸性介质中用氧化还原滴定法研究了铈(IV)离子在痕量铱(III)离子催化作用下,于298~313 K区间氧化四氢糠醇(THFA)的反应动力学. 结果表明,反应对铈(IV)离子为一级,对铱(III)离子也为一级,对四氢糠醇的表观反应级数为正分数. 准一级速率常数kobs随[H+]增加而增大,而随[HSO4-]增加而减小. 在氮气保护下,反应能引发丙烯腈聚合,说明在反应中有自由基产生. 通过kobs与[HSO4-]的依赖关系,找到本反应体系的动力学活性物种是Ce(SO4)2,并计算出平衡常数,速控步骤的速率常数及相应的活化参数. 相似文献
43.
Sumin Wang Gengliang Yang Zhiwei Li Liu Haiyan Jie Bai Yihua Zhang 《Chromatographia》2006,64(1-2):23-29
Use of micellar mobile phases in reversed-phase liquid chromatography (RPLC) results in hydrophobic and electrostatic sites
for interaction. Modified stationary phases in micellar liquid chromatography (MLC) are structurally similar to biomembranes.
To confirm this we focused on the effects of the type and concentration of surfactant (Brij 35, SDS, and CTAB) and mobile
phase pH on the retention of antihypertensive drugs on modified C18 stationary phases. Quantitative retention-activity relationships are proposed for the drugs and the different surfactants
and compared with those obtained using aqueous–organic mobile phases. Finally, a correlation was obtained between the logarithm
of retention factors (log k) and the toxicity (LD50) of antihypertensive drugs.
Revised: 14 September 2005 and 4 April 2006 相似文献
44.
A multiresidue method has been developed for the simultaneous determination of sulfadiazine, sulfathiazole, sulfapyridine,
sulfamerazine, sulfamethoxydiazine, sulfamethylthiazole, sulfamethazine, sulfamonomethoxine, sulfamethoxypyridazine, sulfisoxazole,
sulfamethoxazole, sulfadimethoxine and sulfaquinoxaline in natural animal casings by HPLC after solid-phase extraction. The
sulfonamides were extracted with acetonitrile and the extract cleaned up with an Oasis MCX SPE cartridge prior to analysis.
Separation was on a ZOBAX Eclipse XDB-C8 column using gradient elution with acetonitrile/methanol/0.1% acetic acid. The effect of separation conditions on chromatographic
behavior and recovery has been studied. Calibration graphs were linear with very good correlation coefficients (r = 0.9983−0.9996) in the concentration range from 0.02 to 1 μg mL−1. The limits of quantitation (LOQ) for the 13 sulfonamides were in the range of 1.5–2.2 μg kg−1. Decision limits (CCα) and detection capabilities (CCβ) were in the range of 105.2–111.0 and 113.0–120.2 μg kg−1, respectively. The recovery for casings spiked with 1.5–100 μg kg−1 ranged from 65.2 to 85.9%. The relative standard deviations (RSDs) of the sulfonamides for six measurements at 100 μg kg−1 were from 2.2 to 7.7%. The applicability of the method to the analysis of salted swine casings, salted sheep casings and
dry casing samples was demonstrated. 相似文献
45.
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47.
The glass-transition temperature and non-isothermal crystallization of poly(trimethylene terephthalate)/poly(ethylene 2,6-naphthalate) (PTT/PEN) blends were investigated by using differential scanning calorimeter (DSC). The results suggested that the binary blends showed different crystallization and melting behaviors due to their different component of PTT and PEN. All of the samples exhibited a single glass-transition temperature, indicating that the component PTT and PEN were miscible in amorphous phase. The value of Tg predicted well by Gordon-Taylor equation decreased gradually with increasing of PTT content. The commonly used Avrami equation modified by Jeziorny, Ozawa theory and the method developed by Mo were used, respectively, to fit the primary stage of non-isothermal crystallization. The kinetic parameters suggested that the PTT content improved the crystallization of PEN in the binary blend. The crystallization growth dimension, crystallization rate and the degree of crystallinity of the blends were increased with the increasing content of PTT. The effective activation energy calculated by the advanced iso-conversional method developed by Vyazovkin also concluded that the value of Ea depended not only on the system but also on temperature, that is, the binary blend with more PTT component had higher crystallization ability and the crystallization ability is increased with increasing temperature. The kinetic parameters U* and Kg were also determined, respectively, by the Hoffman-Lauritzen theory. 相似文献
48.
氨·二甲胺·羧酸根合铂(Ⅱ)类配合物的合成、抗肿瘤活性和与DNA的键合水平 总被引:1,自引:0,他引:1
本工作设计合成了6种新型混胺羧酸根合铂(Ⅱ)类配合物[Pt((?)NH)(NH3)X2](a~f){其中,X=CH3COO-(乙酸根),CH3Cl COO-(氯乙酸根),CHCl2COO-(二氯乙酸根),C6H5-COO-(苯甲酸根),p-CH3-C6H4-COO-(对甲基苯甲酸根),p-CH3O-C6H4-COO-(对甲氧基苯甲酸根)}。通过元素分析、摩尔电导、差热分析、红外光谱、紫外光谱和 1H核磁共振谱对配合物进行了表征。通过MTT法研究了配合物的体外抗肿瘤活性,通过等离子体质谱研究了配合物与细胞DNA的键合量;体外抗肿瘤活性测试表明,配合物(a~f)对所测试的肿瘤细胞MCF-7、HCT-8和BGC-823没有表现出活性,但对EJ和HL-60两种肿瘤细胞表现出好的活性,而且配合物(d~f)对HL-60细胞的活性与顺铂相当。配合物(a~f)与HL-60细胞的DNA键合量与其作用浓度表现出一定的依赖性,从小到大的顺序为:cisplatin < c < b < a < f < e < d。 相似文献
49.
pH 4.1的条件下,铜与洛美沙星、曙红反应生成三元络合物,使曙红溶液褪色并产生新的吸收峰,最大褪色峰谷波长位于508 nm,三元络合物吸收峰波长位于546 nm.利用吸收峰、谷的高度差,进行洛美沙星的测定,洛美沙星的质量浓度在0.7~3.8 mg/L范围内符合比耳定律.方法的表观摩尔吸光系数为5.47×104 L·mol-1·cm-1,检出限为0.46 mg/L.该方法用于HCl洛美沙星片剂样品中洛美沙星的测定,准确、灵敏、选择性好.对样品平行6次测定,相对标准偏差为0.42%~3.1%,回收率为92.6%~106.9%. 相似文献
50.
本文提出了一种快速、简便、灵敏检测痕量多胺的新方法。用对酞内酰胺苯甲酰氯同多胺进行柱前衍生反应,以反相高效液相色谱定量测定多胺含量。在4~500 pmol范围内有良好的定量线性关系,腐胺、精脒和精胺的检测限均为0.1 pmol。 相似文献