全文获取类型
收费全文 | 646436篇 |
免费 | 7079篇 |
国内免费 | 1724篇 |
专业分类
化学 | 336159篇 |
晶体学 | 9834篇 |
力学 | 29620篇 |
综合类 | 17篇 |
数学 | 84543篇 |
物理学 | 195066篇 |
出版年
2020年 | 4874篇 |
2019年 | 5256篇 |
2018年 | 12870篇 |
2017年 | 13363篇 |
2016年 | 13183篇 |
2015年 | 7301篇 |
2014年 | 10168篇 |
2013年 | 25764篇 |
2012年 | 22079篇 |
2011年 | 32337篇 |
2010年 | 21706篇 |
2009年 | 21514篇 |
2008年 | 29268篇 |
2007年 | 31615篇 |
2006年 | 20210篇 |
2005年 | 23149篇 |
2004年 | 19343篇 |
2003年 | 17338篇 |
2002年 | 15630篇 |
2001年 | 17032篇 |
2000年 | 13070篇 |
1999年 | 10213篇 |
1998年 | 8423篇 |
1997年 | 8154篇 |
1996年 | 8145篇 |
1995年 | 7249篇 |
1994年 | 7139篇 |
1993年 | 6892篇 |
1992年 | 7802篇 |
1991年 | 7793篇 |
1990年 | 7530篇 |
1989年 | 7369篇 |
1988年 | 7357篇 |
1987年 | 7257篇 |
1986年 | 6894篇 |
1985年 | 8970篇 |
1984年 | 9193篇 |
1983年 | 7431篇 |
1982年 | 7717篇 |
1981年 | 7613篇 |
1980年 | 7120篇 |
1979年 | 7647篇 |
1978年 | 8018篇 |
1977年 | 7750篇 |
1976年 | 7638篇 |
1975年 | 7160篇 |
1974年 | 7070篇 |
1973年 | 7151篇 |
1972年 | 4982篇 |
1967年 | 4373篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
291.
292.
Reynaldo C. Castells Eleuterio L. Arancibia Angel M. Nardillo 《Journal of solution chemistry》1993,22(1):85-94
The retention behavior of eight halomethanes and four saturated hydrocarbons was measured in gas chromatographic stationary phases consisting in tri-n-octylamine (TOA), squalane (SQ) and six TOA+SQ mixtures, at 55.0, 58.5, 62.5 and 65.0°C. Equlibrium constants for complex formation were extracted from experimental data by using a lattice model developed by Martire. The results may be interpreted in terms of the formation of weak hydrogen-bonded complexes, with sociation constants of about 0.13 L-mol–1 for haloforms and 0.07 L-mol–1 for dihalomethanes at 60°C. 相似文献
293.
Whittum D.H. Ebihara K. Hiramatsu S. Kishiro J.-i. Monaka T. Ozaki T. Takayama K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(1):136-141
Studies of microwave amplification with an in-focused electron beam drawn from an induction injector are reported. A free-electron laser (FEL) operating at 9.4 GHz and employing ion-focusing within the interaction region has achieved power in excess of 30 MW at 9.4 GHz, with a beam energy of 0.8 MeV and current of 0.7 kA. Peak gain is 20 dB/m, with no saturation after 15 wiggler periods. Also reported are the first evolution and detuning data for an ion-channel laser/maser (ICL). Two shortcomings of the prematurely halted ICL studies are poor frequency discrimination and a large axial plasma gradient. Prospects for operation with an upgraded 1.6 MeV accelerator are discussed 相似文献
294.
V. M. Shopa B. N. Polevoi I. I. Popadyuk V. I. Tusevich 《Journal of Mathematical Sciences》1993,63(3):398-401
We propose a method of determining the contact pressures between the shells in a packet under the influence of nonlinear internal and constant external pressure. Using the equations of the general moment theory of shells we determine the stress-deformed state of a packet of finite cylindrical shells taking account of frictional forces on the contacting surfaces. One table. Bibliography: 10 titles.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 30, 1989, pp. 94–98. 相似文献
295.
I. M. Karnaukh A. S. Moskovkin G. V. Ponomarev 《Chemistry of Heterocyclic Compounds》1994,30(1):20-25
The mass spectral behavior of 1, 2-di (mesoetioporphyr inyl-1)- and 1, 2-di (mesooctaethylporphyrlnyl) ethanes and ethylenes, their Cu and Ni complexes, as well as Ni Schiff bases of 1, 2-di (mesooctaethylporphyrinyl)ethane complexes, under ionization by electron impact and bombardment by accelerated atoms, was studied. Peaks of molecular ions, for which the basic decomposition pathways were established on the basis of an analysis of the parent and daughter ions, were observed in the electron impact mass spectra of all these compounds.For Communication 29, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 24–29, January, 1994. 相似文献
296.
297.
É. Abele Yu. Popelis É. Lukevits M. Shimanska Yu. Gol'dberg 《Chemistry of Heterocyclic Compounds》1994,30(1):14-19
Alkylation of 2 furanyl- and 2-thienylalkyl ketoximes with alkyl, allyl, and propargyl halides in the two phase catalytic system sol. K2CO3/C6H6/18-crown-6 at room temperature causes the formation of mixtures of E- and Z-isomers of the corresponding O-ethers with yields of 32–74%. Partial E/Z-isomerization takes place during the reaction.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 18–23, January, 1994. 相似文献
298.
M. A. Mikhaleva B. M. Bolotin T. A. Kizner E. S. Serebrykova 《Chemistry of Heterocyclic Compounds》1994,30(1):79-81
We have synthesized 5-alkyl(alkoxy)-2-(o-lzydroxy-p-alkoxyphenyl)pyrimidines and considered the effect of the OH group on the inesomorphism. We have found that in binuclear o-hydroxyarylpyrimidines, an ortho OH group forming an intramolecular hydrogen bond increases Tmp, inhibits the appearance of nematic properties, and promotes the appearance of a smectic A.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 30, No. 1, pp. 90–92, January, 1994. 相似文献
299.
M. M. Benidze 《Chemistry of Natural Compounds》1994,30(5):633-633
300.