全文获取类型
收费全文 | 2864篇 |
免费 | 537篇 |
国内免费 | 287篇 |
专业分类
化学 | 2252篇 |
晶体学 | 36篇 |
力学 | 156篇 |
综合类 | 13篇 |
数学 | 237篇 |
物理学 | 994篇 |
出版年
2024年 | 13篇 |
2023年 | 62篇 |
2022年 | 117篇 |
2021年 | 122篇 |
2020年 | 154篇 |
2019年 | 152篇 |
2018年 | 137篇 |
2017年 | 116篇 |
2016年 | 170篇 |
2015年 | 181篇 |
2014年 | 175篇 |
2013年 | 259篇 |
2012年 | 274篇 |
2011年 | 278篇 |
2010年 | 170篇 |
2009年 | 142篇 |
2008年 | 206篇 |
2007年 | 145篇 |
2006年 | 140篇 |
2005年 | 104篇 |
2004年 | 88篇 |
2003年 | 75篇 |
2002年 | 58篇 |
2001年 | 47篇 |
2000年 | 38篇 |
1999年 | 45篇 |
1998年 | 27篇 |
1997年 | 21篇 |
1996年 | 28篇 |
1995年 | 22篇 |
1994年 | 25篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 20篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有3688条查询结果,搜索用时 15 毫秒
91.
92.
本文用准平衡模型分析讨论了线性电压扫描下MIS器件的I/V瞬态.文中除了给出一般的处理方法以外,还给出了几种不同电压扫描率下I/Y特性的计算结果,并与已往的模型作了比较. 相似文献
93.
Frontispiece: Reactivity Study of Pyridyl‐Substituted 1‐Metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of Group 4 Metallocenes 下载免费PDF全文
94.
Yang Jiao Wan‐Lu Li Dr. Jiang‐Fei Xu Dr. Guangtong Wang Prof. Jun Li Prof. Zhiqiang Wang Prof. Xi Zhang 《Angewandte Chemie (International ed. in English)》2016,55(31):8933-8937
Tuning the activity of radicals is crucial for radical reactions and radical‐based materials. Herein, we report a supramolecular strategy to accelerate the Fenton reaction through the construction of supramolecularly activated radical cations. As a proof of the concept, cucurbit[7]uril (CB[7]) was introduced, through host–guest interactions, onto each side of a derivative of 1,4‐diketopyrrolo[3,4‐c]pyrrole (DPP), a model dye for Fenton oxidation. The DPP radical cation, the key intermediate in the oxidation process, was activated by the electrostatically negative carbonyl groups of CB[7]. The activation induced a drastic decrease in the apparent activation energy and greatly increased the reaction rate. This facile supramolecular strategy is a promising method for promoting radical reactions. It may also open up a new route for the catalytic oxidation of organic pollutants for water purification and widen the realm of supramolecular catalysis. 相似文献
95.
A new cytotoxic 2-(2-phenylethyl)chromone from Chinese eaglewood 总被引:5,自引:0,他引:5
A new compound 8-chloro-5,6,7-trihydroxy-2-(3-hydroxy-4-methoxyphenethyl)-5,6,7,8-tetralaydro-4H-chromen-4-one (1) was isolated from the Chinese eaglewood [Aquilaria sinensis (Lour.) Gilg]. Its structure was elucidated on the basis of spectral data. Compound I showed cytotoxicity against human gastric cancer cell line (SGC-7901) in vitro by MTT method with the IC50 value of 14.6 μg/mL. 相似文献
96.
The structures and stabilities of (Al2O3)n (n = 1-10 and 30) clusters were studied by means of first principles calculations. The calculated results reveal that the global minima of small (Al2O3)n (n = 1-5) clusters are cage structures with high symmetries, in which Al and O atoms are three- and two-coordinated, respectively, and are linked to neighbors via single bonds. Beyond (Al2O3)5, we calculated both cage and cage-dimer structures for (Al2O3)n (n = 6-10), and the results show that, at this size range, cage-dimer structures are more stable than cage structures. Furthermore, an onion-like motif for (Al2O3)10 was studied, and it is interesting to find that, at this size, the onion structure is more favorable than cage and cage-dimer structures. For large clusters, a shell structure of Al60O90 is suggested. Electronic properties and calculations on hydrogen adsorption of these aluminum oxide structures are reported, and we discuss their possible use as hydrogen storage materials. 相似文献
97.
98.
Yanan Wang Sufang Zhang Markus Pötter Wenyi Sun Li Li Xiaobing Yang Xiang Jiao Zongbao K. Zhao 《Applied biochemistry and biotechnology》2016,180(8):1497-1507
Under nutrient-limited conditions, the red yeast Rhodosporidium toruloides can accumulate neutral lipids, of which the compositional fatty acids are mainly saturated and mono-unsaturated ones with 16 or 18 carbon atoms. To improve the linoleic acid content in the lipids, we enabled galactose-inducible expression of the gene encoding Δ12-fatty acid desaturase (FADS) from Mortierella alpina or Fusarium verticillioides by integration of the corresponding expression cassettes into the genome of R. toruloides haploid and diploid strains. The relative linoleic acid content increased up to fivefold and the final linoleic acid titer reached 1.3 g/L under flask culture conditions. Our results suggested that R. toruloides may be further explored as cell factory for production of high-valued lipids and other fatty acid derivatives as bio-based chemicals and fuels. 相似文献
99.
Highly fluorescent CdTe quantum dots (QDs) stabilized by 3-mercaptopropionic acid were prepared by an aqueous solution approach and used as a fluorescent label to link substance P (SP) in studying the interaction of SP with NK-1 receptor, which was expressed on the AR4-2J cell line. Nonspecific adsorptions of CdTe QDs on the AR4-2J cell membrane were observed, whereas the QD-SP conjugates successfully crossed the cell membrane and entered the cytosol. SP is a neurotransmitter, and neurotransmitter-induced calcium concentration oscillation is a common phenomenon in diverse cells especially of secretory type. Cytosolic calcium concentration responses were studied in the AR4-2J cell line during stimulation with SP and QD-SP conjugates. The oscillations triggered by SP and QD-SP conjugates were dose-dependent and very similar. Such QD-SP conjugates readily internalized into the cytosol as would be expected of an active NK-1 ligand. Therefore QD-SP conjugates could be used successfully to study ligand and NK-1 receptor interactions in live cells. Our research may provide a meaningful reference for congener research. 相似文献
100.
Ma J Yang J Jiao L Wang T Lian J Duan X Zheng W 《Dalton transactions (Cambridge, England : 2003)》2011,40(39):10100-10108
The Bi(2)S(3) nanomaterials with various morphologies such as nanorods, nanowires, nanowire bundles, urchin-like microspheres and urchin-like microspheres with cavities have been successfully synthesized through a simple hydrothermal method. Experimental results indicate that sulfur sources play crucial roles in determining the morphologies of Bi(2)S(3) products. Moreover, formation mechanisms of different Bi(2)S(3) nanostructures are discussed based on understanding of the growth habit of Bi(2)S(3) crystal. Finally, we also studied the morphologies-dependent electrochemical and optical properties of the as-synthesized Bi(2)S(3) nanomaterials. 相似文献