全文获取类型
收费全文 | 734篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
化学 | 301篇 |
晶体学 | 3篇 |
力学 | 30篇 |
数学 | 70篇 |
物理学 | 343篇 |
出版年
2020年 | 8篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2016年 | 21篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 24篇 |
2012年 | 17篇 |
2011年 | 21篇 |
2010年 | 13篇 |
2009年 | 10篇 |
2008年 | 21篇 |
2007年 | 23篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 17篇 |
2002年 | 28篇 |
2001年 | 19篇 |
2000年 | 18篇 |
1999年 | 11篇 |
1997年 | 6篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 21篇 |
1993年 | 30篇 |
1992年 | 17篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 18篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 16篇 |
1978年 | 15篇 |
1977年 | 12篇 |
1976年 | 14篇 |
1975年 | 14篇 |
1974年 | 11篇 |
1973年 | 12篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1969年 | 4篇 |
1967年 | 4篇 |
排序方式: 共有747条查询结果,搜索用时 437 毫秒
151.
Experimental measurements of small-signal gain in an optically-pumped NH3 amplifier are carried out at pressures ranging from 40 Torr to 760 Torr, and the results are used to validate a rate-equation model describing the amplifier dynamics. The gain measurements show that dilute mixtures of <0.5% NH3 in N2 are reqired to minimize the problems of gas heating due to pump absorption. The model is used to extrapolate the results to gas pressures of several atmospheres, and to demonstrate the potential for highpressure operation of optically-pumped NH3 lasers. For a pump intensity of 100 MW/cm2, calculations indicate that operation of an NH3–N2 laser is feasible up to a pressure of 10 atm, which would provide a maximum continuous tuning range of 4 cm–1. High-resolution spectroscopy reveals that gain on a few NH3 transitions is eliminated at high pressures due to the presence of overlapping absorptions in other NH3 bands. 相似文献
152.
Isosteric and integral heats of adsorption of xenon on Grafoil have been determined calorimetrically at 195.5 K and at surface coverages of up to 1.1. 相似文献
153.
M. H. Barley J. D. Morrison A. O'Donnel I. B. Parker S. Petherbridge R. W. Wheelhouse 《Fluid Phase Equilibria》1997,140(1-2):183-206
The acceptance of the Montreal Protocol has led to a timetable for the phasing out of chlorine-containing refrigerants and their replacement by new chlorine-free materials. For many applications a pure alternative refrigerant can not be found with the appropriate properties and refrigerant mixtures have been considered. In order to model the properties of these refrigerant blends accurate vapour-liquid equilibrium (VLE) data are required over the range of temperature and pressure of interest to the refrigeration engineer. In this paper we report VLE data for six binary mixtures of the new hydrofluorocarbon refrigerants over a wide range of temperatures and pressures. The six mixtures are: R32/R125, R32/R143a, R32/R134a, R125/R143a, R125/R134a and R143a/R134a. Results for R32/R125 and R32/R134a were obtained down to at least −30°C and were done in duplicate. The raw data were correlated to two models using Maximum Likelihood techniques. One of the models was then used to predict azeotropic compositions for three of the mixtures (R32/R125, R32/R143a and R125/R143a) and the approximate composition of a ternary saddle point azeotrope. 相似文献
154.
The harmonics-to-noise ratio (HNR) was proposed for measurement of noise in sustained vowels. A generalized algorithm is described here for removing the dependence on the data offset and for reducing the influence of jitter and shimmer. In addition, a new algorithm is proposed that accommodates periodic perturbations. Formulations are presented that can be computed in a single pass through the data under certain assumptions, thus simplifying the implementation of an efficient analysis program. A mathematical analysis of the effect of small errors in pitch-period demarcation is presented. The analysis indicates that the sensitivity to demarcation errors depends on the preponderance of high-frequency components, and significant underestimation is predicted for /a/ and /i/ data. A method for correcting quantization and demarcation errors in pitch-period markers is described. The method is shown to be effective at reducing demarcation errors for all but the most severely perturbed waveforms. Examples of the use of this method for HNR estimation are provided. Finally, a comparison with recent work by Milenkovic [J. Speech Hear. Res. 30, 529-538 (1987)] is presented. 相似文献
155.
A. E. Asratvan M. Aderholz V. V. Ammosov G. S. Gapienko V. A. Gapienko J. Guy G. T. Jones V. S. Kaftanov U. F. Katz J. Kern V. A. Korotkov S. P. Krutchinin M. A. Kubantsev P. Marage D. R. O. Morrison N. Schmitz W. Venus W. Wittek V. G. Zaetz 《Zeitschrift fur Physik C Particles and Fields》1995,68(1):43-46
Data from BEBC experiments are combined to provide large statistics for neutrino interactions. ChargedD
* mesons are produced in (1.22±0.25)% of neutrino and (1.01±0.31)% of antineutrino charged current interactions. The mean fraction of the hadronic laboratory energy taken by theD
*+ in these events is 0.59±0.03±0.08. Less than 18% of all chargedD
* mesons from (anti)neutrino interactions are found to be daughters ofD
**0 (at the 90% confidence level). 相似文献
156.
G. T. Jones B. W. Kennedy S. W. O'Neale K. Böckmann W. Gebel C. Geich-Gimbel B. Nellen A. M. Cooper-Sarkar A. Grant H. Klein D. R. O. Morrison P. Schmid H. Wachsmuth J. S. Chima M. M. Mobayyen M. Talebzadeh O. Villalobos-Baillie M. Aderholz L. Deck N. Schmitz K. L. Wernhard W. Wittek G. Corrigan G. Myatt D. Radojicic B. Saitta J. Wells S. Towers P. Shotton 《Zeitschrift fur Physik C Particles and Fields》1985,27(1):43-52
157.
We describe the application of a high-speed spectrophotometric detector and high-performance liquid chromatography to the determination of anthracycline purity in extracted patient specimens and to the identification of chemical reduction products. Blood contained pure anthracyclines whilst in urine, tissue and tumour there was evidence of co-eluting endogenous peaks and complexation. Aerobic reduction yielded two main products: a C13 alcohol and a fully reduced, non-fluorescent, yellow hydroquinone. Anaerobic reduction in the presence of DNA yielded a 7-deoxyaglycone metabolite end product instead of the fully reduced hydroquinone. Eight other separate chromatographic species were identified, all of which showed unique absorbance characteristics, having a visible lambda max at 530 nm and being coloured purple/blue. 相似文献
158.
Morrison R Schmidt D Procario M Johnson DR Lingel K Rankin P Smith JG Alexander J Artuso M Bebek C Berkelman K Besson D Browder TE Cassel DG Cheu E Coffman DM Drell PS Ehrlich R Galik RS Garcia-Sciveres M Geiser B Gittelman B Gray SW Hartill DL Heltsley BK Honscheid K Kandaswamy J Katayama N Kreinick DL Lewis JD Ludwig GS Masui J Mevissen J Mistry NB Nandi S Ng CR Nordberg E O'Grady C Patterson JR Peterson D Pisharody M Riley D Sapper M Selen M Worden H Worris M Avery P Freyberger A Rodriguez J 《Physical review letters》1991,67(13):1696-1700
159.
Akerib DS Barish B Cowen DF Eigen G Stroynowski R Urheim J Weinstein AJ Morrison R Schmidt D Procario M Johnson DR Lingel K Rankin P Smith JG Alexander J Bebek C Berkelman K Besson D Browder TE Cassel DG Cheu E Coffman DM Drell PS Ehrlich R Galik RS Garcia-Sciveres M Geiser B Gittelman B Gray SW Hartill DL Heltsley BK Honscheid K Kandaswamy J Katayama N Kreinick DL Lewis JD Ludwig GS Masui J Mevissen J Mistry NB Nandi S Ng CR Nordberg E O'Grady C Patterson JR Peterson D Pisharody M Riley D 《Physical review letters》1991,67(13):1692-1695
160.
W. Wittek M. Aderholz P. Allport N. Armenise J. P. Baton M. Berggren F. W. Bullock M. Calicchio E. F. Clayton T. Coghen A. M. Cooper-Sarkar O. Erriquez P. Fitch N. Giannakopoulos J. Guy E. Hoffmann P. O. Hulth G. T. Jones P. Kasper U. F. Katz J. Kern H. Klein P. Marage E. Matsinos D. R. O. Morrison M. Neveu M. A. Parker N. Schmitz E. Simopoulou K. Varvell A. Vayaki W. Venus H. Wachsmuth BEBC WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1988,40(2):231-251
The average multiplicities of charged hadrons and of π+, π? and π0 mesons, produced in \(\bar v\) Ne and νNe charged current interactions in the forward and backward hemispheres of theW ±-nucleon center of mass system, are studied with data from BEBC. The dependence of the multiplicities on the hadronic mass (W) and on the laboratory rapidity (y Lab) and the energy fraction (z) of the pion is also investigated. Special care is taken to determine the π0 multiplicity accurately. The ratio of average π multiplicities \(\frac{{2\left\langle {n_{\pi ^O } } \right\rangle }}{{[\left\langle {n_{\pi ^ + } } \right\rangle + \left\langle {n_{\pi ^ - } } \right\rangle ]}}\) is consistent with 1. In the backward hemisphere \(\left\langle {n_{\pi ^O } } \right\rangle \) is positively correlated with the charged multiplicity. This correlation, as well as differences in multiplicities between \(\mathop v\limits^{( - )} \) and \(\mathop v\limits^{( - )} \) , \(\mathop v\limits^{( - )} \) scattering, is attributed to reinteractions inside the neon nucleus of the hadrons produced in the initial \(\mathop v\limits^{( - )} \) interaction. 相似文献