全文获取类型
收费全文 | 3384篇 |
免费 | 482篇 |
国内免费 | 202篇 |
专业分类
化学 | 2085篇 |
晶体学 | 116篇 |
力学 | 110篇 |
综合类 | 17篇 |
数学 | 28篇 |
物理学 | 1712篇 |
出版年
2024年 | 7篇 |
2023年 | 10篇 |
2022年 | 33篇 |
2021年 | 49篇 |
2020年 | 50篇 |
2019年 | 46篇 |
2018年 | 66篇 |
2017年 | 99篇 |
2016年 | 108篇 |
2015年 | 84篇 |
2014年 | 138篇 |
2013年 | 296篇 |
2012年 | 182篇 |
2011年 | 267篇 |
2010年 | 147篇 |
2009年 | 172篇 |
2008年 | 182篇 |
2007年 | 186篇 |
2006年 | 187篇 |
2005年 | 175篇 |
2004年 | 164篇 |
2003年 | 160篇 |
2002年 | 145篇 |
2001年 | 98篇 |
2000年 | 119篇 |
1999年 | 83篇 |
1998年 | 87篇 |
1997年 | 86篇 |
1996年 | 82篇 |
1995年 | 44篇 |
1994年 | 63篇 |
1993年 | 58篇 |
1992年 | 43篇 |
1991年 | 23篇 |
1990年 | 29篇 |
1989年 | 15篇 |
1988年 | 17篇 |
1987年 | 24篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 19篇 |
1983年 | 17篇 |
1982年 | 27篇 |
1981年 | 34篇 |
1980年 | 31篇 |
1979年 | 57篇 |
1978年 | 31篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有4068条查询结果,搜索用时 15 毫秒
111.
A method is described for the gas-chromatographic determination of the diastereomers of vitamin K1 (phylloquinone) in the form of their dihydro dimethyl ethers. The reported method of derivatization and chromatographic analysis in conjunction with optical rotation measurements are useful approaches for characterization of vitamin K1 samples with respect to their origin. 相似文献
112.
Two published procedures for glass capillary column production are applied to produce capillaries for chromatography of polar natural compounds. Soda lime glass capillaries, after leaching with aqueous HCL, are either treated with colloidal silicic acid or with barium carbonate and coated with either Silar 7CP or SE 52. A test mixture as well as polar carbohydrate and peptide mixtures are chromatographed on the different columns and their chromatographic properties are evaluated. Combined capillary gas chromatography-electron impact and chemical ionization mass spectrometry are used for identification of the peptide sequence. 相似文献
113.
114.
Ahmed Abd El-Fattah Mohamad Nageeb Hassan Ahmad Rashad Mona Marei Sherif Kandil 《International Journal of Polymer Analysis and Characterization》2020,25(5):362-373
Abstract An injectable composite hydrogel composed of polyvinyl alcohol (PVA) and bioactive glass (BG) particles were synthesized by a physical crosslinking approach. The morphology, mechanical properties, and viscoelasticity of the PVA/BG composite hydrogel were characterized. Scanning electronic microscopy (SEM) showed uniform and homogeneous distribution of BG particles throughout the composite hydrogel. The incorporation of 2.5?wt% of BG particles in the composite hydrogel formulations, enhanced the static compressive strength and static elastic modulus by 325% and 150%, respectively. The storage molds (G′) was greater than the loss modules (G′′) at all the frequency range studied, which revealed a self-standing elastic composite hydrogel with a smooth injectability. The PVA/BG composite hydrogel was also implanted subcutaneously in the dorsal region of adult male rats. After 4?weeks of implantation, no inflammatory cells were seen within and around the implant, which indicated that the composite hydrogel was biocompatible. The properties of the synthesized injectable PVA/BG composite hydrogel demonstrate its capability toward bone regeneration. 相似文献
115.
A.A. Ahmed I.M. Youssof A.F. Abbas O. Abou Eleinen 《Journal of Sol-Gel Science and Technology》1998,13(1-3):753-756
The chemical durability of lead glass tumblers (24% PbO) in a 4% (v/v) acetic acid solution before and after coating with sol-gel derived SiO2 films was assessed to determine the extent of reduction in Pb-leaching that can be achieved. It was found that by coating the internal surface of the glass tumblers with 1 ml of 10% TEOS solutions at 100°C and densifying the coating formed at 500°C for 1 h, it was possible to reduce Pb-leaching to about one quarter of that of the uncoated glass. 相似文献
116.
Xi-yan Liu Dong Qiu Mei-li Guo Zhen-zhong Yang 《高分子科学》2005,(5):561-566
Sub-micron sized phenolic epoxy resin waterborne particles were prepared by phase inversion emulsification. Micro-phase separation occurred during the curing process at high temperature. The as-prepared samples possessed one glass transition temperature (Tg) and two exothermal processes during DSC heating scannings. After being thermally treated above the exothermal peak temperature, they possessed two glass transition temperatures with the disappearance of exothermal peaks, whilst a core/shell structure was formed. This was likely related with the outward diffusion of reactive oligomers to the outer layer of particles. 相似文献
117.
Two types of commercial glass fibers were subjected to attack in strongly basic KOH solutions. The resulting leach solutions were analysed for Na, Ca, and Si. This showed that the corrosion process attacks the fibers incongruently. Although there are some distinct differences in the performance of these fibers, to a first approximation both types behave similarly. Further, the fibers were depth profiled using a recently developed SNMS technique for fiber in-depth analysis. This showed that both types of fibers behave in a quite dissimilar manner. The fibers were weathered already without any treatment. Although both fibers show alkali ion exchange and network splitting processes, on one of the fiber layers enriched in SiO2, Fe2O3, and CaO are formed by a redeposition process from the leach solution.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
118.
Exfoliated polystyrene (PS)/laponite nanocomposites were prepared successfully. The characteristic doo1 diffraction peak of organo-laponite disappeared in the XRD patterns of nanocomposites, indicating that the laponite layers were exfoliated and the ordered crystal structure of laponite was destroyed because of the styrene polymerization. TEM observations showed that the exfoliated laponite primary particles were dispersed randomly in the PS matrix with lateral dimensions from 1 nm to 10 rim. SEM results showed that the PS/laponite nanocomposite particles were almost monodispersed spheres with the size of about 120 rim. Because of the interaction between PS and laponite nanolayers, the nanocomposites exhibited higher thermal stability and glass transition temperature when compared to pure PS. 相似文献
119.
Summary Thermally stimulated depolarization currents (TSDC) of atactic (a), syndiotactic (s) and isotactic (i) PMMA and mixtures ofs- andi-PMMA were measured. In pure tactic PMMA, TSDC peak was obtained at a temperature corresponding to the glass transition temperature of each PMMA. TSDC of mixtures isolated as precipitates from 1/1 and 1/2 (i/sweight ratio) mixed solutions showed a peak which can be attributed to the glass transition temperature of the stereocomplex. TSDC of original l/1 mixture showed two peaks which are ascribed to the glass transition temperature of residual i-PMMA and the stereocomplex. The results suggests that stereocomplex formation occurs ini/s weight ratio of 1/2 independent of the way of preparation.With 9 figures and 1 table 相似文献
120.
Most of the common classes of organic compounds chromatograph normally on Superoxes. There is no tailing or adverse effect from excessively different activity different activity coefficients. Superoxes are therefore universal phases for gas chromatography. This is also expressed by a wide useful temperature range from ~50° to ~300°. High MW Superox-4 has a MAOT about 20° higher than the lower MW Superox-0.1. Several applications illustrating the versatility of Superox phases in (GC)2 are presented. 相似文献