全文获取类型
收费全文 | 4681篇 |
免费 | 249篇 |
国内免费 | 27篇 |
专业分类
化学 | 3119篇 |
晶体学 | 46篇 |
力学 | 134篇 |
综合类 | 6篇 |
数学 | 689篇 |
物理学 | 963篇 |
出版年
2023年 | 40篇 |
2022年 | 44篇 |
2021年 | 71篇 |
2020年 | 95篇 |
2019年 | 91篇 |
2018年 | 82篇 |
2017年 | 108篇 |
2016年 | 184篇 |
2015年 | 152篇 |
2014年 | 154篇 |
2013年 | 328篇 |
2012年 | 274篇 |
2011年 | 336篇 |
2010年 | 218篇 |
2009年 | 183篇 |
2008年 | 222篇 |
2007年 | 185篇 |
2006年 | 158篇 |
2005年 | 144篇 |
2004年 | 144篇 |
2003年 | 144篇 |
2002年 | 128篇 |
2001年 | 76篇 |
2000年 | 72篇 |
1999年 | 59篇 |
1998年 | 59篇 |
1997年 | 49篇 |
1996年 | 45篇 |
1995年 | 37篇 |
1994年 | 48篇 |
1993年 | 41篇 |
1992年 | 31篇 |
1991年 | 41篇 |
1989年 | 29篇 |
1988年 | 32篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1983年 | 28篇 |
1982年 | 36篇 |
1981年 | 34篇 |
1980年 | 39篇 |
1979年 | 26篇 |
1978年 | 32篇 |
1977年 | 28篇 |
1976年 | 33篇 |
1975年 | 27篇 |
1974年 | 27篇 |
1959年 | 26篇 |
1958年 | 36篇 |
1957年 | 35篇 |
排序方式: 共有4957条查询结果,搜索用时 31 毫秒
81.
Individual extraction constants of some dicarbollylcobaltate anions in the water-nitrobenzene system
E. Makrlík J. Rais K. Baše J. Plešek P. Vaňura 《Journal of Radioanalytical and Nuclear Chemistry》1995,198(2):359-365
Individual extraction constants of nine dicarbollylcobaltate anions in the two-phase water-nitrobenzene system were determined radiometrically assuming that the changes of Gibbs energy of the transfer of the tetraphenylarsonium cation, Ph4As+, and of the tetraphenylborate anion, BPh
4
–
, from the aqueous into the nitrobenzene phase are equal. The constants obtained by this method were correlated with Hansch's constants of hydrophobity. 相似文献
82.
Ludvík Beneš Vítězslav Zima 《Journal of inclusion phenomena and macrocyclic chemistry》1994,20(4):381-391
The course of intercalation of water into 1-VOPO4 has been studied by thermomechanical analysis and X-ray diffraction. Neither formation of vanadyl phosphate monohydrate nor staging were observed during the intercalation. The broadening and the shift of the positions of the lines in the diffractograms have been explained by the random stacking of intercalated and nonintercalated layers in the sample. 相似文献
83.
V. Hnatowicz J. Kvítek V. Švorčík V. Rybka V. Popok 《Czechoslovak Journal of Physics》1994,44(6):621-627
Samples of polyethylene (PE) loaded with carbon black up to 8 wt.% and implanted with 150 keV Sb+ ions to the doses from 2×1013–2×1015 cm–2 were studied using standard Rutherford Back Scattering (RBS) technique. On the PE samples implanted to the doses above 2×1014 cm–2, a considerable surface carbonization is observed. The measured parameters of the Sb depth profile are compared with theoretical TRIM estimations. The projected range is by 25% lower than the theoretical one and the range straggling is about twice of that predicted. The differences are explained by stepwise polymer degradation during the ion bombardment. Strong oxidation of the ion implanted polymers is also observed. The oxygen depth profiles from the sample surface up to the depth comparable with Sb+ ion range evolve from nearly uniform one for low ion doses to highly non-uniform one for doses above 1×1015 cm–2. The total oxygen content in the sample surface layer 300 nm thick reaches a maximum for the doses of (1–2)×1014 cm–2.On leave from Belorussian State University, 220050 Minsk, Belarus.The authors thank the member of electrostatic accelerator group at INP for help during RBS measurements. The work was partly (V.H. and J.K.) supported by the Internal Grant Agency of the Academy of Sciences of Czech Republic under the grant No. 14805 and by the Internal Grant Agency of the Ministry of Education of Czech Republic under the grant No. 1002 (V.., V.R., V.H. and J.K.). In the final stage, the work was also supported by the Grant Agency of Czech Republic under the grant No. 202/93/0121. 相似文献
84.
I. Orúe P. Gorría F. Plazaola M. L. Fernández-Gubieda J. M. Barandiarán 《Hyperfine Interactions》1994,94(1):2199-2205
Mössbauer measurements have been performed on amorphous and nanocrystalline alloy ribbons of nominal composition Fe86Zr7Cu1B6. The nanocrystalline samples were obtained by annealing the as-quenched alloy at different temperatures in the range between 650 and 870 K. Mössbauer spectra of the as-quenched amorphous sample have been recorded at 77 K, room temperature and above the Curie temperature (330 K) at 360 K. We have also performed Mössbauer measurements at room temperature in the nanocrystalline alloys to characterize the phases that appear after the annealing and their relative concentration. The as-quenched sample spectra reveal the existence of two inequivalent sites for Fe. Such a feature is also observed in the remaining amorphous phase of the annealed samples. In the first steps of crystallization, -Fe precipitates and its concentration increases with the annealing temperature. The experimental results suggest that the composition of the whole amorphous phase does not suffer large changes during crystallization. 相似文献
85.
86.
87.
88.
89.
Zdeněk Kotrba 《Mikrochimica acta》1977,68(3-4):97-106
Summary The definitions given by various authors for the limit of detectability are compared and their relationship to the basic measurements (especially the background value) is explained. A new definition is derived on the assumption that the relative standard deviation must not exceed 33.3% if negative results are to be avoided. Negative results may still appear, but only very rarely. The properties of this limit of detectability are discussed, together with the effect of making multiple measurements of the background and peak.
Zusammenfassung Die von verschiedenen Autoren angegebenen Definitionen der Nachweisgrenze wurden verglichen und deren Beziehung zu den Bezugsmessungen (besonders des Untergrundes) wurde erklärt. Eine neue Definition wurde von der Annahme abgeleitet, daß die relative Standardabweichung 33,3% nicht überschreiten darf, sollen negative Resultate vermieden werden. Solche können zwar auftreten, aber nur sehr selten. Die Eigenschaften dieser Nachweisgrenze wurden ebenso wie die Auswirkung mehrfacher Messungen des Untergrundes und der Peaks diskutiert.相似文献
90.
A. Baştuğ Ö. Söğüt Y. Şahin M. Ertuğrul 《Journal of Radioanalytical and Nuclear Chemistry》2002,251(2):323-327
La and Lb X-ray fluorescence cross sections in Er, Ta, W and Au at excitation energies of 16.896, 22.581, 25.770, 32.890, 38.184, 43.949, 50.214 and 59.5 keV were investigated. Measurements were made using a low energy Si(Li) detector coupled to a model 4096 computerized multi-channel analyser. The experimental results were compared with the theoretically calculated values of L X-rays fluorescence cross sections and other experimental results. Good agreement was observed between experimental and theoretical values. 相似文献