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排序方式: 共有372条查询结果,搜索用时 303 毫秒
1.
在Li2O-Al2O3-SiO2系统玻璃中掺入少量晶核剂TiO2,ZrO2,P2O5,再掺入稀土离子和过渡金属离子作为着色剂,在高温下溶制得到彩色透明玻璃,对上述玻璃进行微晶化处理,用差热分析(DTA)确定其晶化温度,测定与讨论了所获彩色透明微晶玻璃在紫外波段至近红外波段的吸收光谱特性,研究结果表明,玻璃微晶化后,由于基质玻璃对光的微弱散射,引起吸收的增强,但不改变稀土离子和过渡金属离子的本征吸收峰位。  相似文献   
2.
Two novel polyketides, penicillones A (1) and B (2), with tricyclo [5.3.1.03,8] undecane skeleton, were isolated from Penicillium terrestre. Their structures and relative stereochemistries were determined on the basis of spectroscopic methods. The absolute configuration of 2 was established by the modified Mosher’s method, while that of 1 was deduced from the similar CD absorptions of 1 and 2. Compound 1 showed weak cytotoxicities against P338 and A-549 cell lines, while 2 was inactive against P388.  相似文献   
3.
Huang H  Panek JS 《Organic letters》2004,6(23):4383-4385
A convergent total synthesis of cytotoxic marine macrolide callipeltoside A is described. The synthesis highlights two stereoselective [4 + 2] annulations for the preparation of associated pyran rings.  相似文献   
4.
合成了标题卟啉配体及其钴、镍、铜、锌和铁的五种配合物.对它们进行了元素分析、UV、IR和荧光光谱等结构表征.用DTA、TG、DSC等手段研究了这些新化合物的热稳定性及热分解机理,实验结果与HMO方法计算的结果一致.  相似文献   
5.
合成了标题卟啉配体及其钴,镍,铜,锌和铁的五种配合物,对它们进行了元素分析,UV,IR和荧光光谱等结构表征。用DTA,TG,DSC等手段研究了这些新化合物的热稳定性及热分解机理,实验结果与HMO方法计算的结果一致。  相似文献   
6.
LiCoO2 xerogel hollow nanofibers were first prepared by co‐electrospinning the sol precursor, and the polycrystalline LiCoO2 hollow nanofibers were obtained after calcination of the xerogel fibers. The obtained hollow nanofibers made up of 20~30 nm nanocrystals were about 100 nm to several micrometers in outer diameter. The hollow nanofibers were detected by means of SEM, TEM, TG, DSC, FTIR, and XRD techniques.  相似文献   
7.
Using a coaxial capillary spinneret electrospinning technique combined with the sol-gel method, the nickelic xerogel hollow nanofibers first were prepared and the polycrystalline LiNiO2 hollow nanofibers were obtained after sintering. The obtained hollow nanofibers were about 500 nm to 4 µm in outer diameter, and were made up of 20 ~ 30 nm nanocrystals. The xerogel hollow nanofibers and those calcined at different temperatures were characterized by thermogravimetric (TG) analysis, Fourier transform infrared (FTIR) spectrum, x-ray diffractometry (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM).  相似文献   
8.

The aim of this study was to perform qualitative and quantitative analyses of aloe-emodin, rhein, and emodin in three prepared samples of compound qi yin granules by high-performance thin-layer chromatography (HPTLC) and to establish an analytical method. TLC was used to qualitatively analyze the three major components of the compound: aloe-emodin, rhein, and emodin. HPTLC was performed to determine the contents of the three components. HPTLC analysis showed that using Anhui Liangchen high-efficiency silica gel G plate was the optimal stationary phase and the upper layer solution of a petroleum ether–ethyl acetate–formic acid (15.5:5:1, V/V) mixed solution was the optimal developing agent. The composition of the samples for testing was basically the same, but the content was different. In summary, this study used HPTLC to qualitatively and quantitatively analyze aloe-emodin, rhein, and emodin in compound qi yin granules. It can lay the foundation for improving the quality control and standards of compound qi yin granules.

  相似文献   
9.
Li  Kun  Wu  Yishi  Li  Xuemei  Fu  Hongbing  Zhan  Chuanlang 《中国科学:化学(英文版)》2020,63(4):490-496
Quaternary blended organic solar cells utilize four blended material components(one donor plus three acceptors, two donors and two acceptors, or three donors plus one acceptor) as the active layer materials. The use of four material components allows us to have more material selections and more mechanism choices to improve the photon-to-electron conversion efficiency. In this contribution, we present a new case of quaternary material system, that shows 17.1% efficiency obtained by adding IDIC and PC_(71)BM as the guest acceptors of the host binary of PM6:Y6. The lowest unoccupied molecular orbital(LUMO) levels of IDIC and PC_(71)BM are both higher than that of Y6, which is one reason to obtain increased open-circuit voltage(V_(oc)) in the quaternary device. Upon introduction of IDIC and PC_(71)BM as the acceptor guests, the hole and electron mobilities are both increased, which contributes to the increased short-circuit current-density(J_(sc)). Effects of the weight ratios of the three acceptor components are investigated, which demonstrates that the increased hole and electron mobilities, the accelerated hole-transfer, and the reduced monomolecular recombination are the factors contributing to the increased J_(sc)and fill-factor. This case of quaternary device demonstrates the applicability of the quaternary strategy in increasing the device functions and hence the efficiencies in the field of organic photovoltaic cells.  相似文献   
10.
铋改性的钒磷氧化物液相催化氧化环己烷的反应机理   总被引:1,自引:0,他引:1  
 制备了铋改性的钒磷氧化物(Bi-VPO)催化剂,并将其用于液相催化氧化环己烷,研究了该反应的反应机理. 结果表明,铋改性可大大提高VPO催化剂在温和条件下对环己烷液相氧化的催化性能. 无溶剂实验和四氢呋喃作溶剂的实验证明反应过程中溶剂乙腈和H2O2之间存在相互作用; 自由基捕捉实验证明环己烷氧化过程中存在自由基反应历程; 环己醇氧化实验证明环己酮并不是来自环己醇的氧化,而是由环己烷直接氧化得到的.  相似文献   
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