全文获取类型
收费全文 | 529596篇 |
免费 | 4164篇 |
国内免费 | 1281篇 |
专业分类
化学 | 269413篇 |
晶体学 | 7665篇 |
力学 | 26030篇 |
综合类 | 17篇 |
数学 | 67978篇 |
物理学 | 163938篇 |
出版年
2021年 | 5053篇 |
2020年 | 5489篇 |
2019年 | 6237篇 |
2018年 | 8458篇 |
2017年 | 8597篇 |
2016年 | 11655篇 |
2015年 | 6192篇 |
2014年 | 10483篇 |
2013年 | 23542篇 |
2012年 | 18393篇 |
2011年 | 21849篇 |
2010年 | 16483篇 |
2009年 | 16352篇 |
2008年 | 20724篇 |
2007年 | 20553篇 |
2006年 | 18679篇 |
2005年 | 16650篇 |
2004年 | 15498篇 |
2003年 | 13975篇 |
2002年 | 13859篇 |
2001年 | 14748篇 |
2000年 | 11377篇 |
1999年 | 8768篇 |
1998年 | 7618篇 |
1997年 | 7489篇 |
1996年 | 6931篇 |
1995年 | 6261篇 |
1994年 | 6266篇 |
1993年 | 6017篇 |
1992年 | 6376篇 |
1991年 | 6869篇 |
1990年 | 6579篇 |
1989年 | 6486篇 |
1988年 | 6322篇 |
1987年 | 6134篇 |
1986年 | 5872篇 |
1985年 | 7412篇 |
1984年 | 7771篇 |
1983年 | 6535篇 |
1982年 | 6818篇 |
1981年 | 6330篇 |
1980年 | 6006篇 |
1979年 | 6508篇 |
1978年 | 6745篇 |
1977年 | 6633篇 |
1976年 | 6587篇 |
1975年 | 6305篇 |
1974年 | 6130篇 |
1973年 | 6426篇 |
1972年 | 4710篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
912.
913.
914.
915.
Methods of preparing diverse metallosupramolecular polymers containing 2,2′-bipyridine and 2,2′:6′,2″-terpyridine moieties in main chains and their properties have been considered and analyzed. It has been shown that these polymers offer new possibilities for the design of materials possessing valuable specific characteristics. 相似文献
916.
R. B. Bayatyan B. E. Bayatyan L. A. Saakyan 《Russian Journal of Applied Chemistry》2006,79(11):1849-1852
Liquid-phase oxidation of bromovinyl compounds with the aim to obtain the corresponding α-bromo acids was studied.
Original Russian Text R.B. Bayatyan, B.E. Bayatyan, L.A. Saakyan, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol.
79, No. 11, pp. 1870–1873. 相似文献
917.
S. A. Giller L. A. Sherin' D. É. Zarin' R. A. Zhuk 《Chemistry of Heterocyclic Compounds》1978,14(5):556-561
The corresponding monophosphates, cyclophosphates, and , -diphosphates were obtained by phosphorylation of 1-(1, 4-dihydroxy-2-pentyl) thymine, 1-(1, 3-dihydroxy-2-propyl) uracil, and their derivatives with selective protection of one of the hydroxyl groups. 2-Cyanoethyl phosphate (CEP) in the presence of N, N-dicyclohexylcarbodiimide (DCC), polyphosphoric acid, and pyrophosphoryl chloride were used as phosphorylating agents. The dependence of the yields of the products of phosphorylation of 1-(1, 4-dihydroxy-2-pentyl) thymine with CEP on the ratio of the reacting substances and the reaction time was studied. The monophosphates were cyclized under the influence of DCC. In the case of 1-(1, 3-dihydroxy-2-propyl) uracil 1-phosphate a dimeric phosphate was obtained in addition to a cyclophosphate. The acid hydrolysis of the cyclophosphates was investigated.See [1] for communication V; see [2] for a preliminary communication.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 678–683, May, 1978. 相似文献
918.
919.
920.
R. A. Gavar L. Kh. Baumane Ya. P. Stradyn' S. A. Giller 《Chemistry of Heterocyclic Compounds》1974,10(3):280-284
Anion radicals of 2-vinylene derivatives of 5-nitrofuran were obtained by electrochemical generation. The hyperfine structure (hfs) of the ESR spectra of these anion radicals indicates delocalization of the unpaired electron over their entire π-electron system. The effect of the vinylene grouping on the distribution of the unpaired electron in the anion radicals and on the distribution of the unpaired electron in the vinylene grouping itself was examined on the basis of the hfs constants. It was found that the vinylene grouping by localizing more than 10% of the density of the unpaired electron on itself reduces, by a factor of 1.4, the effect of substituents in the 2 position of 5-nitrofuran on the distribution of the spin of the unpaired electron in the nitrofuran framework. 相似文献