全文获取类型
收费全文 | 1360333篇 |
免费 | 25814篇 |
国内免费 | 7726篇 |
专业分类
化学 | 683873篇 |
晶体学 | 20085篇 |
力学 | 74728篇 |
综合类 | 104篇 |
数学 | 242942篇 |
物理学 | 372141篇 |
出版年
2021年 | 13549篇 |
2020年 | 15953篇 |
2019年 | 16095篇 |
2016年 | 27583篇 |
2015年 | 20752篇 |
2014年 | 30516篇 |
2013年 | 74582篇 |
2012年 | 39310篇 |
2011年 | 36206篇 |
2010年 | 36816篇 |
2009年 | 38951篇 |
2008年 | 35467篇 |
2007年 | 30947篇 |
2006年 | 38474篇 |
2005年 | 29754篇 |
2004年 | 31281篇 |
2003年 | 29392篇 |
2002年 | 30640篇 |
2001年 | 30129篇 |
2000年 | 25851篇 |
1999年 | 23061篇 |
1998年 | 21302篇 |
1997年 | 21213篇 |
1996年 | 21224篇 |
1995年 | 19267篇 |
1994年 | 18695篇 |
1993年 | 18248篇 |
1992年 | 18387篇 |
1991年 | 18642篇 |
1990年 | 17832篇 |
1989年 | 17850篇 |
1988年 | 17446篇 |
1987年 | 17329篇 |
1986年 | 16331篇 |
1985年 | 22722篇 |
1984年 | 23905篇 |
1983年 | 20053篇 |
1982年 | 21772篇 |
1981年 | 20966篇 |
1980年 | 20286篇 |
1979年 | 20517篇 |
1978年 | 21815篇 |
1977年 | 21404篇 |
1976年 | 21159篇 |
1975年 | 19877篇 |
1974年 | 19585篇 |
1973年 | 20044篇 |
1972年 | 14515篇 |
1968年 | 12344篇 |
1967年 | 12673篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
A numerical procedure, with an exact strain-displacement relationship of twisted and curved cylindrical panels having variable thickness derived by considering the Green strain tensor on general shell theory, is presented using the principle of virtual work and the Rayleigh-Ritz method with algebraic polynomials as in-plane and transverse displacement functions. The accuracy and applicability of the procedure are verified by comparing the present results with previous experimental and theoretical results for several panels. The effects of variation ratio of thickness in chordwise and lengthwise directions, twist, and curvature both in two directions aforementioned on vibrations of cylindrical panels are studied in detail, and typical vibration mode shapes are plotted to demonstrate the effects. 相似文献
142.
Optics and Spectroscopy - The relationship between the parameters of quadripoles (mirrors, for example) ensuring the fulfillment of the energy conservation law are considered. Apart from the... 相似文献
143.
The Wheeler–DeWitt equation of arbitrary Hartle–Hawking factor ordering for several minisuperspace universe models, such as the pure gravity Friedmann–Robertson–Walker and Taub ones, is mapped onto the dynamics of corresponding classical oscillators. The latter ones are studied by the classical Ermakov invariant method, which is a natural approach in this context. For the more realistic case of a minimally coupled massive scalar field, one can study, within the same type of approach, the corresponding squeezing features as a possible means of describing cosmological evolution. Finally, we comment on the analogy with the accelerator physics. 相似文献
144.
A.-S. F. Obada M. Darwish H. H. Salah 《International Journal of Theoretical Physics》2002,41(9):1755-1768
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined. 相似文献
145.
The thermal decomposition of piperidine hydrothiocyanate, piperazine hydrothiocyanate, and the dihydrothiocyanates of ethylenediamine and 1,3-diaminopropane has been studied using TG. Piperidine hydrothiocyanate decomposes in a single step while the dihydrothiocyanates follow more complicated decomposition patterns yielding H2S and half of the organic moiety first. The second step involves the loss of H2S and the remainder of the organic moiety. In each case, complex polymeric materials result. Piperazine hydrothiocyanate also decomposes in two steps, the first involving the loss of half of the piperazine and the second involving the loss of piperazine and H2S. Kinetic parameters have been determined for all these reactions. 相似文献
146.
147.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 5, pp. 815–819, May, 1991. 相似文献
148.
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
149.
150.
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