全文获取类型
收费全文 | 11836篇 |
免费 | 189篇 |
国内免费 | 49篇 |
专业分类
化学 | 6904篇 |
晶体学 | 91篇 |
力学 | 433篇 |
数学 | 1949篇 |
物理学 | 2697篇 |
出版年
2022年 | 110篇 |
2021年 | 139篇 |
2020年 | 145篇 |
2019年 | 157篇 |
2018年 | 144篇 |
2017年 | 117篇 |
2016年 | 231篇 |
2015年 | 186篇 |
2014年 | 201篇 |
2013年 | 639篇 |
2012年 | 432篇 |
2011年 | 532篇 |
2010年 | 370篇 |
2009年 | 332篇 |
2008年 | 478篇 |
2007年 | 447篇 |
2006年 | 434篇 |
2005年 | 416篇 |
2004年 | 417篇 |
2003年 | 341篇 |
2002年 | 317篇 |
2001年 | 208篇 |
2000年 | 206篇 |
1999年 | 177篇 |
1998年 | 133篇 |
1997年 | 157篇 |
1996年 | 184篇 |
1995年 | 142篇 |
1994年 | 142篇 |
1993年 | 165篇 |
1992年 | 177篇 |
1991年 | 168篇 |
1990年 | 133篇 |
1989年 | 132篇 |
1988年 | 144篇 |
1987年 | 188篇 |
1986年 | 161篇 |
1985年 | 220篇 |
1984年 | 205篇 |
1983年 | 158篇 |
1982年 | 179篇 |
1981年 | 187篇 |
1980年 | 177篇 |
1979年 | 179篇 |
1978年 | 172篇 |
1977年 | 171篇 |
1976年 | 148篇 |
1975年 | 165篇 |
1974年 | 134篇 |
1973年 | 127篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
C L Van Doren G A Gescheider R T Verrillo 《The Journal of the Acoustical Society of America》1990,87(5):2201-2206
The ability of subjects to detect temporal gaps between bursts of sinusoids or bursts of bandlimited noise was measured to evaluate the phenomenon of tactile "sensory persistence" in older persons. Vibratory stimuli were delivered to the right thenar eminence of 27 subjects ranging in age from 8-75 years. The subjects' task was to detect the presence of a silent interval or "gap" between flanking 350-ms vibrotactile stimuli. The gap-detection threshold, expressed as the amplitude of vibration relative to the absolute detection threshold, decreased as the gap duration increased and was higher for gaps in noise than for gaps in sinusoids. The threshold for detecting short gaps increased with age for noise stimuli, but not for sinusoidal stimuli. Furthermore, the gap-detection threshold recovered more rapidly in older subjects for noise stimuli, but less rapidly in older subjects for sinusoidal stimuli. Because of these differences, it appears that the effects of age on gap detection cannot be due to a simple increase in sensory persistence, but may be due to multiple processes. 相似文献
54.
In this paper, we adapt the octahedral simplicial algorithm for solving systems of nonlinear equations to solve the linear complementarity problem with upper and lower bounds. The proposed algorithm generates a piecewise linear path from an arbitrarily chosen pointz
0 to a solution point. This path is followed by linear programming pivot steps in a system ofn linear equations, wheren is the size of the problem. The starting pointz
0 is left in the direction of one of the 2
n
vertices of the feasible region. The ray along whichz
0 is left depends on the sign pattern of the function value atz
0. The sign pattern of the linear function and the location of the points in comparison withz
0 completely govern the path of the algorithm.This research is part of the VF-Program Equilibrium and Disequilibrium in Demand and Supply, approved by the Netherlands Ministry of Education, Den Haag, The Netherlands. 相似文献
55.
56.
57.
J. D. Lamb F. R. Nordmeyer R. G. Smith A. Van Orden R. Allison R. P. Lash 《Journal of Radioanalytical and Nuclear Chemistry》1992,159(2):285-292
Ion chromatography (IC) can be used to separate radioiodine from fission products and other ionic species in complex reprocessing solution matrices. A preliminary concentration and separation of the radioiodine is performed using a column filled with a platinum-coated copper bed which converts all forms of iodine to iodide and selectively adsorbs the iodide. The separation is completed by employing an anion chromatographic system. The iodide peak aliquot is collected for subsequent radioanalysis by low energy photon spectroscopy. Results indicate quantitative separation and recovery of iodine. The entire system is automated under computer control and is able to handle small (l) and large (500 ml) sample sizes. 相似文献
58.
E. Matsinos J. Guy E. Simopoulou W. Venus P. Allport M. Berggren M. Calicchio T. Coghen A. M. Cooper-Sarkar O. Erriquez N. Giannakopoulos G. T. Jones P. Marage M. M. Mobayyen D. R. O. Morrison S. O'Neale M. A. Parker J. Sacton R. A. Sansum N. Schmitz G. W. Van Apeldoorn K. Varvell A. Vayaki H. Wachsmuth W. Wittek BEBC WA Collaboration 《Zeitschrift fur Physik C Particles and Fields》1989,44(1):79-87
Backward proton and pion production is studied in ν and \(\bar v\) charged current interactions in neon. The results are compared with other experiments and theory. The complete backward proton data is compatible with protons produced by reinteractions in the nucleus. However in events with only one proton, muon variables appear correlated to those for the backward proton, as expected by the two-nucleon correlation model. 相似文献
59.
60.
Tobacco protein separation by aqueous two-phase extraction 总被引:13,自引:0,他引:13
Tobacco has long been considered as a host to produce large quantity of high-valued recombinant proteins. However, dealing with large quantities of biomass is a challenge for downstream processing. Aqueous two-phase extraction (ATPE) has been widely used in purifying proteins from various sources. It is a protein-friendly process and can be scaled up easily. In this paper, ATPE was studied for its applicability to recombinant protein purification from tobacco with egg white lysozyme as the model protein. Separate experiments with poly(ethylene glycol) (PEG)-salt-tobacco extract and PEG-salt-lysozyme were carried out to determine the partition behavior of tobacco protein and lysozyme, respectively. Two-level fractional factorial designs were used to study the effects of factors such as, PEG molecular mass, PEG concentration, the concentration of phase forming salt, sodium chloride concentration and pH, on protein partitioning. The results showed that, among the studied systems, PEG-sodium sulfate system was most suitable for lysozyme purification. Detailed experiments were conducted by spiking lysozyme into the tobacco extract. The conditions with highest selectivity of lysozyme over native tobacco protein were determined using a response surface design. The purification factor was further improved by decreasing the phase ratio along the tie line corresponding to the phase compositions with the highest selectivity. Under selected conditions the lysozyme yield was predicted to be 87% with a purification factor of 4 and concentration factor of 14. From this study, ATPE was shown to be suitable for initial protein recovery and partial purification from transgenic tobacco. 相似文献