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排序方式: 共有492条查询结果,搜索用时 8 毫秒
91.
REN Zhi'an CHE Guangcan JIA Shunlian CHEN Hong NI Yongming ZHAO Zhongxian 《中国科学A辑(英文版)》2001,44(9):1205-1208
The effect of Mg and C contents on TC in MgCN3, and structure and superconductivity of MgCNi3-x Co x were studied. It is found that the excess of Mg and C in initial material mixture is favorable to improvement inT c and helps to obtain single-phase samples. For preparing MgCNi3 superconductor, the optimum composition of starting materials is MgC1.45Ni3 with excess of Mg (20 wt.%) of the stoichiometric composition. In gCNi3-x Co x system, a continuous solid solution is formed, lattice parameter decreases slightly andT c decreases obviously with increasingx. A suppression of superconductivity is observed due to the substitution of Co (Mn) for Ni. The suppression effect is smaller for the substitution of Co than that of Mn 相似文献
92.
硫酸化氧化锆固体超强酸 总被引:1,自引:0,他引:1
硫酸化氧化锆(SZ)是一种固体超强酸催化剂,它能高效催化异构化、烷化、酰化、环化、裂解、酯化和酯交换等多种类型的催化反应。1979年,日本科学家Hino和Arata发现SZ能在室温催化丁烷异构化反应,首次提出了SZ是一种酸性比100%浓硫酸还强一万倍的固体超强酸,从而引起了科学家们对SZ研究的浓厚兴趣。经过了三十多年发展,研究者们在SZ的合成、改性、表征和应用等方面取得了许多新的研究成果。本文综述了SZ几十年来的研究进展,内容主要包括SZ的合成方法,表面结构和酸性机理,研究者们对SZ性质的不同看法,SZ的改性及应用。 相似文献
93.
94.
激光聚变靶中氘氚燃料的测量 总被引:3,自引:2,他引:1
用Si(Li)-S85低能X-射线谱仪系统测量简单爆推靶中氘氚燃料的含量。用内充气正比计数装置刻度了此谱仪系统的探测效率。其效率与玻璃球成份和壁厚有关。本系统的效率为10~5量级。根据氚含量及燃料的D/T比值,推算出靶内含氘量及氘氚燃料的总气压,并与气泡法测得的总气压进行了比较。最后对实验结果进行分析和讨论。 相似文献
95.
Yongming Zhu Tae Hyun Kim Y. Y. Lee Rongfu Chen Richard T. Elander 《Applied biochemistry and biotechnology》2006,130(1-3):586-598
A novel method of producing food-grade xylooligosaccharides from corn stover and corn cobs was investigated. The process starts
with pretreatment of feedstock in aqueous ammonia, which results delignified and xylan-rich substrate. The pretreated substrates
are subjected to enzymatic hydrolysis of xylan using endoxylanase for production of xylooligosaccharides. The conventional
enzyme-based method involves extraction of xylan with a strong alkaline solution to form a liquid intermediate containing
soluble xylan. This intermediate is heavily contaminated with various extraneous components. A costly purification step is
therefore required before enzymatic hydrolysis. In the present method, xylan is obtained in solid form after pretreatment.
Water-washing is all that is required for enzymatic hydrolysis of this material. The complex step of purifying soluble xylan
from contaminant is essentially eliminated.
Refining of xylooligosaccharides to food-grade is accomplished by charcoal adsorption followed by ethanol elution. Xylanlytic
hydrolysis of the pretreated corn stover yielded glucan-rich residue that is easily digestible by cellulase enzyme. The digestibility
of the residue reached 86% with enzyme loading of 10 filter paper units/g-glucan. As a feedstock for xylooligosaccharides
production, corn cobs are superior to corn stover because of high xylan content and high packing density. The high packing
density of corn cobs reduces water input and eventually raises the product concentration. 相似文献
96.
Yixuan Wang Hao Liu Min Wu Kai Wang Yongming Sui Zhaodong Liu Siyu Lu Zhihong Nie John S. Tse Xinyi Yang Bo Zou 《Chemical science》2021,12(19):6580
Core/shell nanocrystals (NCs) integrate collaborative functionalization that would trigger advanced properties, such as high energy conversion efficiency, nonblinking emission, and spin–orbit coupling. Such prospects are highly correlated with the crystal structure of individual constituents. However, it is challenging to achieve novel phases in core/shell NCs, generally non-existing in bulk counterparts. Here, we present a fast and clean high-pressure approach to fabricate heterostructured core/shell MnSe/MnS NCs with a new phase that does not occur in their bulk counterparts. We determine the new phase as an orthorhombic MnP structure (B31 phase), with close-packed zigzagged arrangements within unit cells. Encapsulation of the solid MnSe nanorod with an MnS shell allows us to identify two separate phase transitions with recognizable diffraction patterns under high pressure, where the heterointerface effect regulates the wurtzite → rocksalt → B31 phase transitions of the core. First-principles calculations indicate that the B31 phase is thermodynamically stable under high pressure and can survive under ambient conditions owing to the synergistic effect of subtle enthalpy differences and large surface energy in nanomaterials. The ability to retain the new phase may open up the opportunity for future manipulation of electronic and magnetic properties in heterostructured nanostructures.Core/shell MnSe/MnS nanocrystals with the B31 phase are thermodynamically stable under high pressure and can survive under ambient conditions owing to the synergistic effect of subtle enthalpy differences and high surface energy in nanomaterials. 相似文献
97.
In this study,the nonlocal strain gradient theory is adopted to investigate the static bending deformation of a functionally graded (FG) multilayered nanoplate ... 相似文献
98.
99.
提出将雷达、声呐领域中的时延估计算法用于均匀应变场或温度场中任意形状的光栅反射谱中心波长的检测.分析了信噪比(SNR)对不同形状反射谱进行峰值提取的影响.分析结果表明,对均匀周期的单模光纤布拉格光栅,其长度越长,折射率变化越大,峰值检测受信噪比影响也越严重;实验结果表明,与常规算法相比,采用时延估计中的相位谱法进行中心波长偏移量的提取,估计精度不受波长扫描精度的限制,对噪声造成的中心波长随机漂移有很好的抑制作用,而且无需对反射谱的形状进行假设与曲线拟合,计算量小,检测精度可达到皮米量级. 相似文献
100.