全文获取类型
收费全文 | 6101篇 |
免费 | 612篇 |
国内免费 | 1647篇 |
专业分类
化学 | 4931篇 |
晶体学 | 27篇 |
力学 | 210篇 |
综合类 | 20篇 |
数学 | 1524篇 |
物理学 | 1648篇 |
出版年
2024年 | 9篇 |
2023年 | 224篇 |
2022年 | 260篇 |
2021年 | 245篇 |
2020年 | 279篇 |
2019年 | 193篇 |
2018年 | 222篇 |
2017年 | 241篇 |
2016年 | 253篇 |
2015年 | 280篇 |
2014年 | 384篇 |
2013年 | 461篇 |
2012年 | 564篇 |
2011年 | 538篇 |
2010年 | 405篇 |
2009年 | 414篇 |
2008年 | 360篇 |
2007年 | 349篇 |
2006年 | 326篇 |
2005年 | 241篇 |
2004年 | 207篇 |
2003年 | 150篇 |
2002年 | 144篇 |
2001年 | 163篇 |
2000年 | 255篇 |
1999年 | 211篇 |
1998年 | 103篇 |
1997年 | 86篇 |
1996年 | 65篇 |
1995年 | 61篇 |
1994年 | 58篇 |
1993年 | 46篇 |
1992年 | 57篇 |
1991年 | 50篇 |
1990年 | 34篇 |
1989年 | 30篇 |
1988年 | 71篇 |
1987年 | 123篇 |
1986年 | 133篇 |
1985年 | 32篇 |
1984年 | 20篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有8360条查询结果,搜索用时 62 毫秒
151.
Wen Weng Qing Le Zeng Bi Xia Yao Wen Shi Lin Qing Hua Wang Xiu Li You 《Chromatographia》2006,64(7-8):463-467
Five structurally related amino acid derivatives were enantioseparated by HPLC with a commercially available chiral stationary phase, Chiralcel OD-H. The chromatographic experiments were performed in the normal phase mode. n-Hexane/polar alcohol was used as mobile phase. Excellent baseline enantioseparations could be obtained for all these solutes. The effects of the concentration of polar alcohol and the column temperature on the retentions and enantioseparations were studied in detail. From the van't Hoff plots the corresponding apparent thermodynamic parameters were derived. Mechanism aspects of chiral recognition were discussed based on the relationship between the thermodynamic parameters and the structures of the solutes. It was found that the substituent of the phenyl group on the residual group of the amino acid derivatives was close relevant to thermodynamic origin of enantioseparation. Much better enthalpy–entropy compensation effect was obtained by plotting the differential, rather than the original, thermodynamic parameters. 相似文献
152.
153.
Yang HH Zhu QZ Li DH Lin P Ding MT Xu JG 《Fresenius' Journal of Analytical Chemistry》2001,370(1):88-91
A new fluorimetric immunoassay for alpha-fetoprotein (AFP) has been developed using a novel promising mimetic peroxidase, iron(III) tetrasulfonatophthalocyanine (FeTSPc), as a labeling reagent to catalyze the fluorescence reaction of P- hydroxyphenylacetic acid (P-HPA) and hydrogen peroxide (H2O2). In the competitive immunoassay, anti-AFP antibody was coated on a 96-well plate (polystyrene) and a constant amount of FeTSPc-labeled AFP and a known amount of test solution were added. Non-labeled and FeTSPc-labeled AFP compete for binding to the plate-bound antibody. After the immunoreaction, the immunochemically adsorbed FeTSPc-AFP conjugate moiety was determined by measuring the fluorescence produced in a solution containing P-HPA and H2O2. AFP can be determined in the concentration range of 1-300 ng mL(-1) with a detection limit of 0.5 ng mL(-1). 相似文献
154.
155.
Although the theories and potential applications of intermolecular multiple-quantum coherences (iMQCs) have been under active investigations for over a decade, discussion of iMQC NMR signal formation was mainly confined in the time domain. In this paper, a full line-shape theory was developed to describe iMQC signals in the frequency domain. Relevant features of the line shape, such as peak height, linewidth, and phase, were investigated in detail. Predictions based on the theory agree well with experimental and simulated results. Since radiation-damping effects always couple with iMQCs in highly polarized liquid-state NMR systems, and strongly radiation-damped signals have many spectral characteristics similar to those of iMQCs, a detailed comparison was also made between them from different spectral aspects. With detailed comparison of peak height, linewidth, and phase, this work demonstrates that the iMQC and radiation-damping phenomena result from two completely different physical mechanisms despite that both present similar signal features and coexist in highly polarized liquid-state NMR systems. 相似文献
156.
Based on building emerging engineering education of "energy chemistry", we investigated the state key petro-chemical enterprises according to the industrial development and the demand of professional talents. The research report summarizes, analyzes and discusses the current priority development fields of industry, the talent training status, curriculum structure and education program of the chemistry and chemical engineering in universities. The ideas on emerging engineering education of "energy chemistry" have been proposed, and it will be beneficial to building a novel education program for talents training, which integrates the principle of chemistry, energy conversion and information science, etc. 相似文献
157.
Iron tetrasulfonatophthalocyanine (FeTSPc), a peroxidase mimic, was used as a labeling reagent and poly(N-isopropylacrylamide) (PNIP) as the separation support of the immune complex for the mimetic-enzymatic immunoassay of hepatitis B surface antigen (HBsAg). PNIP was precipitated from aqueous solution when the ambient temperature was higher than its lower critical solution temperature of 31 degrees C. In a sandwich immunoassay, the antigen (HBsAg) first reacted with mouse anti-human HBsAg antibody immobilized on PNIP (PNIP-antibody) and then further reacted with FeTSPc-labeled mouse anti-HBsAg antibody (antibody-FeTSPc) at room temperature in a homogeneous format. After changing the temperature to separate the PNIP-antibody-HBsAg-antibody-FeTSPc conjugate moiety, it was re-dissolved and determined by coupling with the fluorogenic reaction of hydrogen peroxide and p-hydroxyphenylpropionic acid. The sensitivity of this method (3 ng mL-1) was close to that of the traditional ELISA using the same reactants. However, the assay was much faster (the assay time decreased from 100-120 to 45 min). This method was applied to determine HBsAg in human serum with satisfactory results. 相似文献
158.
A flexible approach to ethyl (3R,4S)-N-Boc-4-amino-3-hydroxy-5-phenylpentanoate (N-Boc-AHPPA-OEt), the γ-amino-β-hydroxy acid moiety of hapalosin is described. The synthetic method features a ring-opening ethanolysis of an activated N-Boc-lactam, which is obtained via a diastereoselective reductive-alkylation of (R)-malimide derivative. The flexibility of the method resides in the introduction of the alkyl side chain by Grignard reagent addition. 相似文献
159.
160.
[structure: see text] The viability of the Diels-Alder (DA) cycloaddition of conjugated dienes onto the sidewalls of single-wall carbon nanotubes is assessed by means of a two-layered ONIOM(B3LYP/6-31G:AM1) approach. Whereas the DA reaction of 1,3-butadiene on the sidewall of an armchair (5,5) nanotube is found to be unfavorable, the cycloaddition of quinodimethane is predicted to be viable due to the aromaticity stabilization at the corresponding transition states and products. 相似文献