全文获取类型
收费全文 | 5582篇 |
免费 | 105篇 |
国内免费 | 9篇 |
专业分类
化学 | 4046篇 |
晶体学 | 17篇 |
力学 | 91篇 |
数学 | 623篇 |
物理学 | 919篇 |
出版年
2020年 | 52篇 |
2018年 | 43篇 |
2017年 | 43篇 |
2016年 | 68篇 |
2015年 | 78篇 |
2014年 | 86篇 |
2013年 | 167篇 |
2012年 | 172篇 |
2011年 | 199篇 |
2010年 | 136篇 |
2009年 | 149篇 |
2008年 | 193篇 |
2007年 | 207篇 |
2006年 | 201篇 |
2005年 | 202篇 |
2004年 | 192篇 |
2003年 | 153篇 |
2002年 | 169篇 |
2001年 | 136篇 |
2000年 | 157篇 |
1999年 | 109篇 |
1998年 | 90篇 |
1997年 | 90篇 |
1996年 | 97篇 |
1995年 | 79篇 |
1994年 | 89篇 |
1993年 | 91篇 |
1992年 | 98篇 |
1991年 | 71篇 |
1990年 | 60篇 |
1989年 | 63篇 |
1988年 | 65篇 |
1987年 | 69篇 |
1986年 | 77篇 |
1985年 | 95篇 |
1984年 | 66篇 |
1983年 | 61篇 |
1982年 | 74篇 |
1981年 | 73篇 |
1980年 | 58篇 |
1979年 | 75篇 |
1978年 | 63篇 |
1977年 | 54篇 |
1976年 | 55篇 |
1975年 | 48篇 |
1974年 | 48篇 |
1973年 | 44篇 |
1972年 | 45篇 |
1970年 | 37篇 |
1967年 | 37篇 |
排序方式: 共有5696条查询结果,搜索用时 235 毫秒
41.
42.
Kurt V. Schenker Wolfgang Von Philipsborn C. Anderson Evans Werner Skuballa Georg-Alexander Hoyer 《Helvetica chimica acta》1986,69(7):1718-1727
The configurations of the 5,6-double bond in the carbacyclins iloprost ( 3 ; (E)) and isoiloprost ( 4 ; (Z)) are based on a complete assignment of the 13C and 1H resonances determined by 1D and 2D 13C-NMR and 1H-NMR methods. 相似文献
43.
Wolfgang Will Gerhard Hoffmann Andreas Zober 《Fresenius' Journal of Analytical Chemistry》1992,342(9):744-745
Summary A simple method is described which allows the quantification of 1-vinyl-2-pyrrolidone (NVP) in human serum. NVP is extracted from serum with diethylether and determined with HPLC/UV-detection. 1-Cyclohexyl-2-pyrrolidone serves as an internal standard. The detection limit is 0.1 mg/l. The method has shown that NVP can enter the organisms of workers occupationally exposed to this substance. 相似文献
44.
Scholze H Hoffmann E Lüdke C Platalla A 《Analytical and bioanalytical chemistry》1996,355(7-8):892-894
The use of laser ablation inductively coupled mass spectrometry (laser ICP-MS), in combination with a calibration procedure involving the addition of enriched isotopes, for the determination of trace elements in birch leaves and their ashes is described. Samples are pressed into pellets without binder materials and analyzed using the ICP-MS spectrometer ELAN 5000 with the laser sampler type 320 (Perkin Elmer). The analytical results obtained by two methods are compared with the values obtained after digestion of the same samples and analysis of the resulting solutions by ICP-MS. The results are discussed in terms of precision, accuracy and limits of detections. 相似文献
45.
Hiller W Brüll A Argyropoulos D Hoffmann E Pasch H 《Magnetic resonance in chemistry : MRC》2005,43(9):729-735
The application of HPLC-NMR for the analysis of a mixture of fatty alcohol ethoxylates (FAEs) is described. The use of the new generation, cryogenically cooled probes is investigated in respect of the sensitivity advantage that they provide. The FAE mixture is separated using liquid chromatography at the critical point of adsorption. The ability of the method to differentiate between the different end groups and the degree of polymerization of the mixture constituents is investigated. Both on-flow and stop-flow HPLC-NMR techniques were used together with two-dimensional NMR spectroscopy. The results are compared with those obtained by using an evaporative light scattering detector for the HPLC. 相似文献
46.
VNCl2(Pyridine)2; Synthesis, I. R. Spectrum, and Crystal Structure VNCl2(Pyridine)2 is formed from the cyclothiazeno-vanadium(IV) complex [VCl(N3S2)(Pyridine)2]2 · 2 CH2Cl2 in boiling toluene in form of brown-red, hydrolysis sensitive crystal. It was characterized by its I.R. spectrum and an X-ray crystal structure determination. VNCl2(Pyridine)2crystallizes in the orthorhombic space group Pccn with four formula units per unit cell (668 observed independent reflexions, R = 0.055). Lattice constants: a = 1550, b = 924, c = 832 pm. Monomer molecules are situated on twofold rotation axes. They are stacked along the V?N axis to form columns V?N…V. The short VN bond of 160 pm corresponds to a triple bond, whereas the V…N distance of 256 pm indicates a weak interaction. The V? N(Pyridine) and V? Cl bond lengths are 213.0 and 233.5 pm, respectively. 相似文献
47.
The racemic cis-anti-trans-steroids 9 to 11 have been synthesized in a highly stereoselective manner starting from 4-methoxybenzocyclobutene carboxylic acid via the key step 8 → 9 . (cf. Scheme 2). 相似文献
48.
49.
Pilz N. Hoffmann P. Lieser K. H. Dams W. Nelges K. H. 《Analytical and bioanalytical chemistry》1989,334(7):695-717
Analytical and Bioanalytical Chemistry - A non-destructive method and an experimental set-up are described by which the Pu content in UO2/PuO2 mixed oxide (MOX) pellets and in fuel rods,... 相似文献
50.
The process of electron transport plays an essential role in the fundamental phenomena of life like photosynthesis, respiration and vision as well as in photoelectronic devices. However, the molecular mechanisms of the electron way and factors governing the transport rate in such systems are still unclear. Several groups have reported theoretical approaches for searching the mechanisms by using statistical mechanics, coherent dynamics and quantum mechanics. The current density vector inside the semiconducting layer is determined. In this paper we consider the problem of transport of electron promoted in the electrochemical cell constructed of two electrodes with the dye molecules immersed in. We describe the process of electron promotion by refractive light wave on the vacuum–semiconductor boundary as well as on the semiconducting electrode and the dye molecule layer in terms of extended phenomenological electrodynamics formalism. The results of our theoretical model show that such a theoretical approach will give more information on the mechanism of electron transport and will give insight in the determination of some electric features of materials. 相似文献