全文获取类型
收费全文 | 4418篇 |
免费 | 121篇 |
国内免费 | 13篇 |
专业分类
化学 | 3122篇 |
晶体学 | 17篇 |
力学 | 58篇 |
数学 | 492篇 |
物理学 | 863篇 |
出版年
2023年 | 20篇 |
2022年 | 27篇 |
2021年 | 52篇 |
2020年 | 82篇 |
2019年 | 51篇 |
2018年 | 33篇 |
2017年 | 20篇 |
2016年 | 100篇 |
2015年 | 88篇 |
2014年 | 113篇 |
2013年 | 197篇 |
2012年 | 249篇 |
2011年 | 294篇 |
2010年 | 138篇 |
2009年 | 124篇 |
2008年 | 237篇 |
2007年 | 211篇 |
2006年 | 223篇 |
2005年 | 227篇 |
2004年 | 231篇 |
2003年 | 179篇 |
2002年 | 183篇 |
2001年 | 102篇 |
2000年 | 92篇 |
1999年 | 49篇 |
1998年 | 45篇 |
1997年 | 56篇 |
1996年 | 69篇 |
1995年 | 55篇 |
1994年 | 81篇 |
1993年 | 77篇 |
1992年 | 75篇 |
1991年 | 59篇 |
1990年 | 50篇 |
1989年 | 49篇 |
1988年 | 43篇 |
1987年 | 26篇 |
1986年 | 26篇 |
1985年 | 51篇 |
1984年 | 34篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 29篇 |
1980年 | 26篇 |
1979年 | 31篇 |
1978年 | 23篇 |
1977年 | 26篇 |
1976年 | 23篇 |
1975年 | 25篇 |
1973年 | 32篇 |
排序方式: 共有4552条查询结果,搜索用时 15 毫秒
991.
992.
Herbert Budzikiewicz Peter-Eric Vieth Uwe Krüger 《Monatshefte für Chemie / Chemical Monthly》1981,112(6-7):825-840
In1H-NMR spectra of amids with long-chain aliphatic N-substituents one observes—despite of the free mobility of the aliphatic chain—splitting of the signals of the terminal methyl groups which is caused by the hindered rotation of the amide bond. 相似文献
993.
994.
The efficiency of the multiconfigurational time-dependent Hartree (MCTDH) method for calculating the initial-state selected dissociation probability of H(2)(v=0,j=0) on Cu(100) is investigated. The MCTDH method is shown to be significantly more efficient than standard wave packet methods. A large number of single-particle functions is required to converge the initial-state selected reaction probability for dissociative adsorption. Employing multidimensional coordinates in the MCTDH ansatz (mode combination) is found to be crucial for the efficiency of these MCTDH calculations. Perspectives towards the application of the MCTDH approach to study dissociative adsorption of polyatomic molecules on surfaces are discussed. 相似文献
995.
The determination of mercury by the title method with sodium tetrahydroborate as reducing agent can be interfered with by volatile nitrogen oxides which inhibit the reduction of mercury by scavenging the reducing agent. The nitrogen oxides are formed as reduction products of nitric acid during sample decomposition. The interference effect was encountered in the determination of mercury in sewage sludge digests, and the main symptom was poor reproducibility of the shape of the mercury peak. The area of the mercury peak is more resistant to the interference than the peak height. The nitrogen oxide interference did not cause any systematic error in the mercury determination when calibration was done by standard addition. The interference can be easily remedied by purging the sample with argon. 相似文献
996.
997.
Bean A Bobbink GJ Brock IC Engler A Ferguson T Kraemer RW Rippich C Vogel H Bebek C Berkelman K Blucher E Cassel DG Copie T DeSalvo R DeWire JW Ehrlich R Galik RS Gilchriese MG Gittelman B Gray SW Halling AM Hartill DL Heltsley BK Holzner S Ito M Kandaswamy J Kowalewski R Kreinick DL Kubota Y Mistry NB Mueller J Namjoshi R Nordberg E Ogg M Perticone D Peterson D Pisharody M Read K Riley D Silverman A Stone S Yi X Sadoff AJ Avery P Besson D Bowcock T Giles RT Hassard J Kinoshita K Pipkin FM 《Physical review letters》1987,58(3):183-186
998.
The effectiveness of the anionic surfactant sodium dodecyl sulfate (SDS) for suppressing adsorption interferences in anodic stripping voltammetry (ASV) was investigated. The samples included fruit juices, wine, beer, milk powder and waste water, and the analytes were cadmium, lead and copper. In most of the samples, the ASV signals were severely depressed or even absent due to electrode fouling, but addition of SDS in concentrations up to 10 g L(-1) proved effective in restoring the ASV response. By using SDS as an interference suppressor, the content of lead and copper in a milk powder reference material was determined, and the results were in agreement with the certified values. In this determination, which could not have been performed without SDS, the surfactant also served as a homogenizing agent, preventing separation of the sample components. The effect of SDS was explained by the interaction of the surfactant with the electrode surface and with the constituents of the sample matrix. 相似文献
999.
Mass spectrometric detection for capillary isoelectric focusing separations of complex protein mixtures 总被引:7,自引:0,他引:7
Jensen PK Pasa-Tolić L Peden KK Martinović S Lipton MS Anderson GA Tolić N Wong KK Smith RD 《Electrophoresis》2000,21(7):1372-1380
Capillary isoelectric focusing (CIEF) can provide high-resolution separations of complex protein mixtures, but until recently it has primarily been used with conventional UV detection. This technique would be greatly enhanced by much more information-rich detection methods that can aid in protein characterization. We describe progress in the development of the combination of CIEF with Fourier transform ion cyclotron resonance (FTICR) mass spectrometry and its application to proteome characterization. Studies have revealed 400-1000 putative proteins in the mass range of 2-100 kDa from total injections of approximately 300 ng protein in single CIEF-FTICR analyses of cell lysates for both Escherichia coli (E. coli) and Deinococcus radiodurans (D. radiodurans). We also demonstrate the use of isotope labeling of the cell growth media to improve mass measurement accuracy and provide a means for quantitative proteome-wide measurements of protein expression. The ability to make such comprehensive and precise measurements of differences in protein expression in response to cellular perturbations should provide new insights into complex cellular processes. 相似文献
1000.
Gerhard Quinkert Uwe Dller Mathias Eichhorn Frank Küber Hans Peter Nestler Heinrich Becker Jan W. Bats Gottfried Zimmermann Gerd Dürner 《Helvetica chimica acta》1990,73(7):1999-2047
Further Contributions to the Synthesis of (+)-Aspicilin There are two reasons to try to find out. whether the initial and final parts of the ‘photochemical synthesis’ of the 18-membered lichen macrolide (+)-aspicilin ( 5a ) can be improved (cf. Schemes 1 and 2). This synthesis acts as an indicator for the utility of the earlier introduced photolactonization and as a source of large-ring-sized lactones, objects for computer-assisted conformational analysis. 相似文献