全文获取类型
收费全文 | 586051篇 |
免费 | 7878篇 |
国内免费 | 2454篇 |
专业分类
化学 | 315797篇 |
晶体学 | 8657篇 |
力学 | 25636篇 |
综合类 | 72篇 |
数学 | 70528篇 |
物理学 | 175693篇 |
出版年
2021年 | 4728篇 |
2020年 | 5334篇 |
2019年 | 5777篇 |
2018年 | 7471篇 |
2017年 | 7390篇 |
2016年 | 11204篇 |
2015年 | 7168篇 |
2014年 | 10923篇 |
2013年 | 26449篇 |
2012年 | 20877篇 |
2011年 | 25506篇 |
2010年 | 17953篇 |
2009年 | 17768篇 |
2008年 | 23612篇 |
2007年 | 23580篇 |
2006年 | 21910篇 |
2005年 | 19678篇 |
2004年 | 18044篇 |
2003年 | 15886篇 |
2002年 | 15676篇 |
2001年 | 17570篇 |
2000年 | 13333篇 |
1999年 | 10265篇 |
1998年 | 8621篇 |
1997年 | 8377篇 |
1996年 | 8169篇 |
1995年 | 7268篇 |
1994年 | 7247篇 |
1993年 | 7026篇 |
1992年 | 7769篇 |
1991年 | 7847篇 |
1990年 | 7500篇 |
1989年 | 7259篇 |
1988年 | 7176篇 |
1987年 | 7048篇 |
1986年 | 6763篇 |
1985年 | 8887篇 |
1984年 | 9029篇 |
1983年 | 7328篇 |
1982年 | 7561篇 |
1981年 | 7359篇 |
1980年 | 6808篇 |
1979年 | 7337篇 |
1978年 | 7667篇 |
1977年 | 7593篇 |
1976年 | 7525篇 |
1975年 | 6984篇 |
1974年 | 7064篇 |
1973年 | 7039篇 |
1972年 | 5162篇 |
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
921.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 9, pp. 1132–1136, September, 1989. 相似文献
922.
923.
Time structure of iodine laser pulse in the free running mode of operation was studied using the power amplifier of laser system PERUN as the laser oscillator. Two characteristic shapes of laser pulse correspond to different regimes of laser operation, the existence of which is ascribed to the critical concentration of I2 molecules. Simultaneously an additional chemical pumping was proved at least in the initial phase of photodissociation and in a late-time lasing after the end of flashlamps pumping light. 相似文献
924.
925.
M. P. Nosov V. A. Smirnova Yu. F. Zabashta A. Ya. Fridman M. P. Mokhnach 《Mechanics of Composite Materials》1989,25(1):8-12
Conclusion A method was proposed which makes it possible to study the low-frequency internal friction of complex fibers. This method was used to study the internal friction of complex composite fibers based on PCA and PE. We observed a relaxation process which is typical of the composite and is absent in the pure materials.Translated from Mekhanika Kompozitnykh Materialov, No. 1, pp. 11–15, January–February, 1989. 相似文献
926.
M. Faucher D. Garcia E. Antic-Fidancev M. Lemaitre-Blaise 《Journal of Physics and Chemistry of Solids》1989,50(12)
Some structural and spectroscopic features of rare earth orthoaluminates are examined.The trigonal→ orthorhombic transition is studied in a series of NdxSm1−xAlO3 compounds. The evolution of the crystal structure is followed by X-ray analysis and optical absorption. The free ion and crystal field parameters of Nd3+ (4f3 configuration) are determined in LuAlO3:Nd3+.The anomaly of the calculated splitting of the
levels is slight, but well characterized in NdAlO3. The spin correlated crystal field and orbitally correlated crystal field models are tested as well as an empirical correction which was proposed earlier. 相似文献
927.
In an effort to clarify the role of controlled oxygen exposure in the synthesis of LaBa2Cu3Oy samples which achieve zero resistivity above 90 K, we have prepared samples of La(1+x)Ba(2–x)Cu3Oy with x approximately equal to 0 and with y varying between 6.22 and 7.00. We find that for large values of y, 6.88相似文献
928.
Summary We have estimated and measured the daily thermal expansion of an oceanographic platform. This has been found negligible as
far as the calibration of a satellite altimeter is concerned. 相似文献
929.
V. A. Popova I. V. Podgornaya V. G. Lundina L. I. Kurnikova A. I. Tarasov 《Russian Chemical Bulletin》1987,36(11):2361-2364
Conclusions Complex compounds of bisacyl derivatives of diaminodibenzo-18-crown-6 ether are active catalysts of the two stages of the synthesis of poly(ethylene terephthalate).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2544–2547, November. 1987. 相似文献
930.
D. B. Kayumova Yu. P. Syrnikov N. V. Penkina M. N. Rodnikova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(10):1634-1635
The structural relaxation time for series of various liquids (alkanes, aliphatic alcohols, and diols) are calculated from published data on the shear viscosity and the heat of evaporation per unit volume. Liquids having a 3D H-bond network (diols) are characterized by relaxation times one to two orders of magnitudes longer than those typical of liquids without such a network (alkanes and aliphatic alcohols). 相似文献