全文获取类型
收费全文 | 4833篇 |
免费 | 236篇 |
国内免费 | 1799篇 |
专业分类
化学 | 4388篇 |
晶体学 | 109篇 |
力学 | 57篇 |
综合类 | 41篇 |
数学 | 1553篇 |
物理学 | 720篇 |
出版年
2023年 | 59篇 |
2022年 | 84篇 |
2021年 | 72篇 |
2020年 | 103篇 |
2019年 | 116篇 |
2018年 | 92篇 |
2017年 | 105篇 |
2016年 | 119篇 |
2015年 | 113篇 |
2014年 | 197篇 |
2013年 | 334篇 |
2012年 | 192篇 |
2011年 | 240篇 |
2010年 | 201篇 |
2009年 | 253篇 |
2008年 | 303篇 |
2007年 | 341篇 |
2006年 | 246篇 |
2005年 | 240篇 |
2004年 | 239篇 |
2003年 | 248篇 |
2002年 | 274篇 |
2001年 | 262篇 |
2000年 | 168篇 |
1999年 | 157篇 |
1998年 | 166篇 |
1997年 | 128篇 |
1996年 | 126篇 |
1995年 | 91篇 |
1994年 | 110篇 |
1993年 | 115篇 |
1992年 | 131篇 |
1991年 | 100篇 |
1990年 | 108篇 |
1989年 | 137篇 |
1988年 | 122篇 |
1987年 | 146篇 |
1986年 | 134篇 |
1985年 | 125篇 |
1984年 | 120篇 |
1983年 | 84篇 |
1982年 | 26篇 |
1981年 | 21篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1975年 | 12篇 |
1974年 | 17篇 |
1973年 | 11篇 |
排序方式: 共有6868条查询结果,搜索用时 15 毫秒
71.
72.
项斯端 《浙江大学学报(理学版)》2004,31(1):88-97
根据KIM和LEE(1999)将多管藻属分为两独立属新管藻及多管藻,报道了我国14种及1变种1变型多管藻,以及11种新管藻,其中19种为我国新记录,发表了新种垫状多管藻(Polysiphonia caespitosa sp.nov)及新变种岩生多管藻长节变种(P.scopulorum var.longinodium var.nov.). 相似文献
73.
74.
75.
Zachary Cline 《Journal of Pure and Applied Algebra》2019,223(8):3635-3664
Let q be an nth root of unity for and let be the Taft (Hopf) algebra of dimension . In 2001, Susan Montgomery and Hans-Jürgen Schneider classified all non-trivial -module algebra structures on an n-dimensional associative algebra A. They further showed that each such module structure extends uniquely to make A a module algebra over the Drinfel'd double of . We explore what it is about the Taft algebras that leads to this uniqueness, by examining actions of (the Drinfel'd double of) Hopf algebras H “close” to the Taft algebras on finite-dimensional algebras analogous to A above. Such Hopf algebras H include the Sweedler (Hopf) algebra of dimension 4, bosonizations of quantum linear spaces, and the Frobenius–Lusztig kernel . 相似文献
76.
In the present work we characterize the existence of quasistationary distributions for diffusions on allowing singular behavior at 0 and . If absorption at 0 is certain, we show that there exists a quasistationary distribution as soon as the spectrum of the generator is strictly positive. This complements results of Cattiaux et al. (2009) and Kolb and Steinsaltz (2012) for 0 being a regular boundary point and extends results by Cattiaux et al. (2009) on singular diffusions. 相似文献
77.
Joachim Toft 《Applied and Computational Harmonic Analysis》2019,46(1):154-176
We extend Feichtinger's minimality property on the smallest non-trivial time-frequency shift invariant Banach space, to the quasi-Banach case. Analogous properties are deduced for certain matrix spaces.We use these results to prove that the pseudo-differential operator is a Schatten-q operator from to and r-nuclear operator from to when for suitable p, q and r in . 相似文献
78.
79.
《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2309-2317
Complexes of beryllium chloride and nitrate with (Me2N)2P(O)F were characterized in solution by multinuclear NMR spectroscopy and in some cases by IR spectroscopy and conductimetry. 31P and 19F NMR spectra were informative of changes associated with complex formation revealing resonances consistent with different species in solution and suggest an equilibrium between these species in both beryllium derivatives. These compounds show narrow lines in the solution 9Be NMR spectra, indicative of a highly symmetric environment for beryllium. The presence of the different species was more pronounced in beryllium chloride complexes. The results are compared to those reported in the literature for hexamethylphosphoramide (HMPA). 相似文献
80.
《Phosphorus, sulfur, and silicon and the related elements》2013,188(11):2349-2356
Seven new 1-fluorinated-4-phosphopyrazoles 2 have been prepared in 60–94% yield by cyclization of N-(2′,2′,2′-trifluoroethyl) phosphonyl β-hydrazones 1 with triethyl orthoformate in the presence of acetic acid. The IR data, the 1H, 13C, 19F, 31P chemical shifts and coupling constants of the compounds 2 are reported. 相似文献