全文获取类型
收费全文 | 1388875篇 |
免费 | 29799篇 |
国内免费 | 7750篇 |
专业分类
化学 | 699831篇 |
晶体学 | 20525篇 |
力学 | 75660篇 |
综合类 | 107篇 |
数学 | 244644篇 |
物理学 | 385657篇 |
出版年
2021年 | 13543篇 |
2020年 | 15956篇 |
2019年 | 16103篇 |
2018年 | 14189篇 |
2016年 | 28728篇 |
2015年 | 20957篇 |
2014年 | 30567篇 |
2013年 | 74637篇 |
2012年 | 40734篇 |
2011年 | 39773篇 |
2010年 | 38618篇 |
2009年 | 40619篇 |
2008年 | 38131篇 |
2007年 | 34524篇 |
2006年 | 38877篇 |
2005年 | 31963篇 |
2004年 | 32641篇 |
2003年 | 30180篇 |
2002年 | 30884篇 |
2001年 | 31513篇 |
2000年 | 26584篇 |
1999年 | 23320篇 |
1998年 | 21366篇 |
1997年 | 21321篇 |
1996年 | 21245篇 |
1995年 | 19267篇 |
1994年 | 18737篇 |
1993年 | 18288篇 |
1992年 | 18619篇 |
1991年 | 18857篇 |
1990年 | 18037篇 |
1989年 | 18091篇 |
1988年 | 17608篇 |
1987年 | 17597篇 |
1986年 | 16593篇 |
1985年 | 22938篇 |
1984年 | 24060篇 |
1983年 | 20175篇 |
1982年 | 21793篇 |
1981年 | 21006篇 |
1980年 | 20345篇 |
1979年 | 20671篇 |
1978年 | 21870篇 |
1977年 | 21505篇 |
1976年 | 21256篇 |
1975年 | 19952篇 |
1974年 | 19596篇 |
1973年 | 20068篇 |
1972年 | 14534篇 |
1967年 | 12734篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
The object of this note is to prove the followingTheorem Let{a_n}and{b_n}be sequences of real numbers such that0<∑∑a_n~2<+∞and0<∑b_n~2<+∞.Then we have the inequalitysum from m=1 to∞sum from n=1 to∞a_mb_n/m+n<{sum from n=1 to∞(π-θ/n~(1/2)a_n~2}~1/2{sum from n=1 to∞(π-θ/n~(1/2)b_n~2}~1/2 (1)whereθ=3/2~(1/2)-1=1.121320343. 相似文献
992.
M E Lutman S Gatehouse A G Worthington 《The Journal of the Acoustical Society of America》1991,89(1):320-328
Frequency resolution ability was measured using a psychoacoustical tuning curve (PTC) or a notch-noise technique in two population samples. The first sample incorporated 1764 subjects with various degrees of sensorineural hearing impairment and ranging in age from 17-80 years. The second sample included 240 subjects aged between 50 and 75 years, carefully balanced in terms of impairment and age to avoid confounding between these two variables. In both samples, frequency resolution ability declined with increasing hearing threshold level (HTL), as measured by either method. In a subsample tested with both methods, the correlation between the two was only modest. After accounting for HTL, there was a minor dependence of frequency resolution on age, older subjects having poorer frequency resolution once HTL had been accounted for. No addition to the explained variance was achieved by taking sex, occupational group, or audiogram slope into account. Despite the documented reproducibility of the measures, much of the variance in the frequency resolution measurements remained unrelated to HTL or age. 相似文献
993.
994.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 815–819, May, 1991. 相似文献
995.
K. A. Bronnikov 《Annalen der Physik》1991,503(8):527-534
A multidimensional generalization of the Reissner-Nordström solution of general relativity is obtained for the case of n Ricci-flat internal spaces. A two-parameter family of black-hole solutions for an arbitrary dimensionality D is selected. Nontrivial black holes with D > 4 are shown to exist only with a nonzero electric charge. Observational consequences are discussed, in particular, a violation of Coulomb's law. 相似文献
996.
In this paper, we consider linear combinations of modified Baskakov operators. By use of several lemmas, we obtain the inverse
theorem (Theorem 1.1) and the saturation (Theorem 1.2) for those linear combinations. 相似文献
997.
998.
A. L. Apanasenko A. V. Kuznichenko Yu. B. Govyadovskii V. G. Yakunin 《Journal of Applied Spectroscopy》1991,54(3):271-276
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 3, pp. 438–444, March, 1991. 相似文献
999.
A. S. Merkur'ev 《Journal of Mathematical Sciences》1991,57(6):3489-3497
This article considers the splitting properties of finite-dimensional division rings over universal splitting fields of quadratic forms. An example of a field with u-invariant equal to 6 is constructed, which contradicts Kaplansky's conjecture concerning u-invariants.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im, V. A. Steklova Akademii Nauk SSSR, Vol. 175, pp. 75–89, 1989. 相似文献
1000.
Yu. K. Voron'ko A. B. Kudryavtsev V. V. Osiko E. V. Sorokin 《Journal of Applied Spectroscopy》1991,55(4):953-957
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 535–540, October, 1991. 相似文献