全文获取类型
收费全文 | 753329篇 |
免费 | 8078篇 |
国内免费 | 2197篇 |
专业分类
化学 | 392118篇 |
晶体学 | 10724篇 |
力学 | 35913篇 |
综合类 | 23篇 |
数学 | 98268篇 |
物理学 | 226558篇 |
出版年
2021年 | 6264篇 |
2020年 | 6919篇 |
2019年 | 7649篇 |
2018年 | 9856篇 |
2017年 | 9895篇 |
2016年 | 14436篇 |
2015年 | 8611篇 |
2014年 | 13702篇 |
2013年 | 33772篇 |
2012年 | 25879篇 |
2011年 | 31299篇 |
2010年 | 22347篇 |
2009年 | 22187篇 |
2008年 | 29256篇 |
2007年 | 29249篇 |
2006年 | 27147篇 |
2005年 | 24286篇 |
2004年 | 22412篇 |
2003年 | 20057篇 |
2002年 | 19895篇 |
2001年 | 21329篇 |
2000年 | 16488篇 |
1999年 | 12949篇 |
1998年 | 10976篇 |
1997年 | 10730篇 |
1996年 | 10330篇 |
1995年 | 9338篇 |
1994年 | 9141篇 |
1993年 | 8827篇 |
1992年 | 9549篇 |
1991年 | 9923篇 |
1990年 | 9436篇 |
1989年 | 9238篇 |
1988年 | 9271篇 |
1987年 | 8883篇 |
1986年 | 8497篇 |
1985年 | 11261篇 |
1984年 | 11664篇 |
1983年 | 9752篇 |
1982年 | 10369篇 |
1981年 | 9931篇 |
1980年 | 9464篇 |
1979年 | 10053篇 |
1978年 | 10312篇 |
1977年 | 10216篇 |
1976年 | 10133篇 |
1975年 | 9705篇 |
1974年 | 9466篇 |
1973年 | 9882篇 |
1972年 | 6739篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
The auction algorithm for the transportation problem 总被引:1,自引:0,他引:1
The auction algorithm is a parallel relaxation method for solving the classical assignment problem. It resembles a competitive bidding process whereby unassigned persons bid simultaneously for objects, thereby raising their prices. Once all bids are in, objects are awarded to the highest bidder. This paper generalizes the auction algorithm to solve linear transportation problems. The idea is to convert the transportation problem into an assignment problem, and then to modify the auction algorithm to exploit the special structure of this problem. Computational results show that this modified version of the auction algorithm is very efficient for certain types of transportation problems. 相似文献
972.
We consider a quark model based on QCD scale anomaly in which the quarks move in the field of an effective glueball field.
Hadrons correspond to solitonic bags of higher energy density in a nonperturbative sea of condensed gluons. We calculate the
static properties of nucleon in this model and find that the nucleon mass is far too large (2.4–4 GeV) and the proton charge
radius (0.37–0.54 fm) is low. The proton gyromagnetic ratio and gA/gv are in reasonable agreement with the experimental numbers. 相似文献
973.
974.
975.
S. P. Tretyakova Yu. S. Zamyatnin V. N. Kovantsev Yu. S. Korotkin V. L. Mikheev G. A. Timofeev 《Zeitschrift für Physik A Hadrons and Nuclei》1989,333(4):349-353
The emission of Ne and Mg nuclei was detected in the spontaneous decay of234U with probabilities of, respectively, (3.9 ±1.0) × 10?13 and (2.3 ±0.7) × 10?13 relative toα-decay. The upper limits of this kind of decay for235U and236U have been established. Systematics of half-lives for cluster emission are found to be similar to the Geiger-Nuttall dependence forα-decay. Some evidence for the presence of hindrance to cluster emission from the odd-mass nuclei233U and235U is obtained. 相似文献
976.
J E Paanakker J M Thio H M Van den Wildenberg F M Kaspersen 《Journal of chromatography. A》1987,421(2):327-335
An assay has been developed and validated for the routine monitoring of vecuronium in plasma. It consists of solid-phase extraction using C18 disposables as sample pre-treatment, high-performance liquid chromatography and post-column ion-pair extraction with fluorimetric detection. The fluorescent anion 9,10-dimethoxyanthracene-2-sulphonate (DAS) is used as the counter ion. The detection limit is ca. 5 ng/ml in plasma with a signal-to-noise ratio of 10. The assay is also applicable for monitoring vecuronium and its potential metabolites in other biological media, e.g., urine, bile and tissue (liver, kidney) homogenates. 相似文献
977.
The variational approach based on the covariant quantization method for the curved Einstein space is applied. 相似文献
978.
Blood serum samples were irradiated by monochromatic synchrotron radiation (15 keV) and by 2.4-MeV protons to compare their performance for the detection of trace elements by x-ray fluorescence (XRF) spectrometry. Absolute concentration assignment was based on the addition of an internal standard and on a method which uses the incoherent and coherent radiation as a flux monitor of the incoming beam. Preliminary experiments with a synchrotron XRF microprobe are reported. 相似文献
979.
The precision of intensity modulated fiber optic sensor systems mainly is restricted by the attenuation characteristics of the analog fiber optical data link. Special encoding and referencing schemes are used to overcome this data link dependence. In this paper encoding and referencing principles for optical sensors are outlined and compared. Especially the two wavelengths referencing and the optical delay line processing techniques are discussed in more detail and results are presented. 相似文献
980.