全文获取类型
收费全文 | 204458篇 |
免费 | 1716篇 |
国内免费 | 593篇 |
专业分类
化学 | 102552篇 |
晶体学 | 3345篇 |
力学 | 9290篇 |
综合类 | 5篇 |
数学 | 22514篇 |
物理学 | 69061篇 |
出版年
2021年 | 1658篇 |
2020年 | 1798篇 |
2019年 | 2003篇 |
2018年 | 2700篇 |
2017年 | 2602篇 |
2016年 | 3772篇 |
2015年 | 2308篇 |
2014年 | 3619篇 |
2013年 | 9090篇 |
2012年 | 7248篇 |
2011年 | 8744篇 |
2010年 | 6043篇 |
2009年 | 5919篇 |
2008年 | 7928篇 |
2007年 | 8098篇 |
2006年 | 7732篇 |
2005年 | 6905篇 |
2004年 | 6436篇 |
2003年 | 5660篇 |
2002年 | 5499篇 |
2001年 | 6429篇 |
2000年 | 4937篇 |
1999年 | 3798篇 |
1998年 | 3043篇 |
1997年 | 3053篇 |
1996年 | 2794篇 |
1995年 | 2618篇 |
1994年 | 2474篇 |
1993年 | 2342篇 |
1992年 | 2696篇 |
1991年 | 2678篇 |
1990年 | 2607篇 |
1989年 | 2398篇 |
1988年 | 2459篇 |
1987年 | 2452篇 |
1986年 | 2285篇 |
1985年 | 2968篇 |
1984年 | 3219篇 |
1983年 | 2632篇 |
1982年 | 2803篇 |
1981年 | 2773篇 |
1980年 | 2644篇 |
1979年 | 2732篇 |
1978年 | 2824篇 |
1977年 | 2824篇 |
1976年 | 2890篇 |
1975年 | 2675篇 |
1974年 | 2648篇 |
1973年 | 2777篇 |
1972年 | 1764篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
942.
C. D. Kalkar V. M. Raut V. B. Gaikwad 《Journal of Radioanalytical and Nuclear Chemistry》1994,177(2):345-355
Lyoluminescence of luminol induced by -irradiated NaCl has been studied in aqueous amines. The emission spectra of lyoluminescence are recorded on 400 ASA Kodak film using a Fuess spectrograph. A broad continuous emission band appears in the visible region from 390 to 500 nm. The emission band showed two peaks centered at 430 and 470 nm. The 430 nm peak is more intense in secondary amines while the 470 nm band is more intense in primary amines. The mechanism of light emission is based on the comparative study of lyoluminescence, fluorescence and chemiluminescence of luminol in aqueous amines. 相似文献
943.
The electrochemical production and doping of soluble, as well as the physicochemical properties of a soluble electrically conducting polymer based on 3-methyl-4-phenylthiophene were studied.Translated from Teoreticheskaya i Éxperimental'naya Khimiya, Vol. 29, No. 2, pp. 143–148, March–April, 1993.The authors would like to express gratitude to the State Committee of the Ukraine on questions of science and technology for financial support for this work within the framework of the State Scientific and Technical Program 7.1. Materials for Electronic Technology, as well as to V. P. Kandilenko and V. Ya. Chernov for aid in recording the fluorescence spectra of the P3M4PT films. 相似文献
944.
Electroanalytical methods based on biosensor technology and differential pH measurement for the determination of l-lactic and l-malic acids in wine were developed. Lactic acid was determined according to two procedures consisting of the use of two lactate electrochemical biosensors, one based on a Clark O(2) probe and the other based on the H(2)O(2) probe. The two probes were assembled employing a polymeric membrane where the enzyme lactate oxidase was previously immobilized. Both sensors exhibited high storage and operational stabilities, and good reproducibility when used in wine matrix. Measurement of lactate was carried out using two different flow-through cells assembled with the lactate probes. The low detection limit of these probes and the relatively high concentration of lactate in wine samples required a serial dilution in the range 1:100 to 1:200, thus eliminating all potential electrochemical or enzyme interferences present in the sample. Malic acid was determined using a differential commercially available pH-meter and an enzymatic procedure. For this analysis, we employed the malic enzyme (EC 1.1.1.40) and the NADP(+) cofactor. The pH variation due to the action of this enzyme on malic acid was found to be proportional to the malic acid present in the sample. Experimental parameters such as pH, temperature, and co-factor concentration were optimized, resulting in malate determination in less than 1 min with good reproducibility. Various samples of wine and wine musts were assayed for lactate with the two biosensor procedures, and for malate with differential pH-metry. The results when compared with those obtained with the commonly used spectrophotometric procedure correlated well. 相似文献
945.
Mark D. Haiman 《Journal of Algebraic Combinatorics》1994,3(1):17-76
We formulate a series of conjectures (and a few theorems) on the quotient of the polynomial ring
in two sets of variables by the ideal generated by all S
n invariant polynomials without constant term. The theory of the corresponding ring in a single set of variables X = {x
1, ..., x
n} is classical. Introducing the second set of variables leads to a ring about which little is yet understood, but for which there is strong evidence of deep connections with many fundamental results of enumerative combinatorics, as well as with algebraic geometry and Lie theory. 相似文献
946.
Joseph D. Lakey 《Journal of Fourier Analysis and Applications》1994,1(2):201-232
In the spirit of work of Kerman and Sawyer, a condition is given that is necessary and sufficient for the Fourier transform norm inequality $\Big(\int_{{\Bbb R}_d} \vert\hat{f}\vert^q d\mu\Big)^{1/q} \leq C\Big(\int_{{\Bbb R}_d} \vert f\vert^p v\Big)^{1/p}$ provided v is a radial weight for which v?1/p is convexly decreasing and μ is a suitable measure. We also establish alternative conditions for such inequalities by proving corresponding trace type inequalities and maximal function inequalities that underlie the Fourier transform estimates. Our conditions are relatively simple to compute. Among applications we give extensions of a Sobolev restriction theorem. 相似文献
947.
948.
Mathew D. Penrose 《Journal of statistical physics》1994,77(1-2):3-15
LetG
R
be the graph obtained by joining all sites ofZ
d which are separated by a distance of at mostR. Let (G
R
) denote the connective constant for counting the self-avoiding walks in this graph. Let (G
R
) denote the coprresponding constant for counting the trees embedded inG
R
. Then asR, (G
R
) is asymptotic to the coordination numberk
R ofG
R
, while (G
R
) is asymptotic toek
R. However, ifd is 1 or 2, then (G
R
)-k
R
diverges to –.Dedicated to Oliver Penrose on this occasion of his 65th birthday. 相似文献
949.
Yu. I. Orekhov L. P. Khokhrin A. V. Gavrin L. D. Rasnetsov L. I. Matusis 《Radiophysics and Quantum Electronics》1994,37(1):89-90
The devices and systems for EHF therapy and diagnosis of the BAYuR series are examined and compared with known analogs.Scientific-Research Measuring-Systems Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 1, pp. 155–157, January, 1994. 相似文献
950.