全文获取类型
收费全文 | 975025篇 |
免费 | 10154篇 |
国内免费 | 3118篇 |
专业分类
化学 | 510477篇 |
晶体学 | 13502篇 |
力学 | 46303篇 |
综合类 | 33篇 |
数学 | 133401篇 |
物理学 | 284581篇 |
出版年
2021年 | 8144篇 |
2020年 | 8915篇 |
2019年 | 9840篇 |
2018年 | 12423篇 |
2017年 | 12321篇 |
2016年 | 18691篇 |
2015年 | 11640篇 |
2014年 | 17976篇 |
2013年 | 44189篇 |
2012年 | 33725篇 |
2011年 | 41081篇 |
2010年 | 29124篇 |
2009年 | 28692篇 |
2008年 | 38013篇 |
2007年 | 37979篇 |
2006年 | 35345篇 |
2005年 | 31766篇 |
2004年 | 29250篇 |
2003年 | 26061篇 |
2002年 | 25769篇 |
2001年 | 27120篇 |
2000年 | 21140篇 |
1999年 | 16702篇 |
1998年 | 14138篇 |
1997年 | 13773篇 |
1996年 | 13450篇 |
1995年 | 12116篇 |
1994年 | 11901篇 |
1993年 | 11554篇 |
1992年 | 12555篇 |
1991年 | 12749篇 |
1990年 | 12247篇 |
1989年 | 11934篇 |
1988年 | 11851篇 |
1987年 | 11615篇 |
1986年 | 11064篇 |
1985年 | 14633篇 |
1984年 | 15110篇 |
1983年 | 12490篇 |
1982年 | 13192篇 |
1981年 | 12797篇 |
1980年 | 12141篇 |
1979年 | 12849篇 |
1978年 | 13182篇 |
1977年 | 13097篇 |
1976年 | 12949篇 |
1975年 | 12301篇 |
1974年 | 12109篇 |
1973年 | 12403篇 |
1972年 | 8625篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.
V. A. Ginzburg 《Functional Analysis and Its Applications》1992,26(1):51-52
The Institute of the Earth Physics, Academy of Sciences of the USSR. Translated from Funktsional'nyi Analiz i Ego Prilozheniya, Vol. 26, No. 1, pp. 64–66, January–March, 1992. 相似文献
892.
S. A. Merkulov 《Functional Analysis and Its Applications》1992,26(1):72-73
Branch of Theoretical Problems, USSR Academy of Sciences, Translated from Funktsional'nyi Analiz i Ego Prilozheniya, Vol. 26, No. 1, pp. 89–90, January–March, 1992. 相似文献
893.
The effects of different ventilation methods on cardiac output measured by the indicator-dilution method, liver blood flow measured by a deuterium washout technique using 2H nuclear magnetic resonance (NMR) and liver concentrations of ATP and intracellular pH determined with 31P NMR were compared in anesthetized rats. No differences in mean arterial blood pressure were demonstrable with the different modes of ventilation. However, significant drops in cardiac output were observed between freely breathing and animals ventilated with positive pressure but not the high frequency oscillatory method (407 +/- 46 and 520 +/- 88 vs. 633 +/- 86 ml/min/kg, p less than 0.05 and p = NS, respectively). Moreover, liver blood flow was significantly reduced during positive pressure but not high frequency oscillatory ventilation compared with free breathing rats (32 +/- 4 and 43 +/- 10 vs. 46 +/- 8 ml/100 g, p less than 0.05 and p = NS, respectively). 31P NMR spectroscopy revealed no effects of either ventilation method on tissue ATP or intracellular pH as estimated by the chemical shift of inorganic phosphate. These data suggest that controlled ventilation in normal rats accomplished with standard positive pressure methods is associated with major decreases in cardiac output and liver blood flow despite maintenance of normal blood pressure. High frequency oscillatory ventilation appears to effect less compromise of cardiac output and hepatic perfusion than positive pressure ventilation and may, therefore, be preferable for some biological studies. 相似文献
894.
We generalize a method for determination of time scales of nonstationary diffusion in a one-dimensional medium. The time of relaxation to a stationary non-equilibrium density of substance in a system with a source, a sink, and an arbitrary potential profile are obtained and studied in detail. A few specific examples are considered. 相似文献
895.
M. J. Soupioni B. D. Symeopoulos H. V. Papaefthymiou 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(3):441-444
Summary Four different bottled water brands sold in Greece in the winter of 2001-2002 were analyzed for a wide range of chemical elements,
using neutron activation analysis (NAA). The elements Na and Br were determined instrumentally (INAA), whereas the other metals
and trace elements radiochemically (RNAA). The results indicated that the mean level of all the elements determined in the
samples were well within the European Union (EU) directive on drinking water and accomplish the drinking water standards of
the World Health Organisation (WHO) as well as of the Food and Drug Administration (FDA). 相似文献
896.
897.
898.
899.
900.
Hypothetical helical organic polymers with localized electrons, charges, and/or atoms are described, in which these localized substructures can move along the backbones of the polymers via sigmatropic H shifts. 相似文献