全文获取类型
收费全文 | 6587篇 |
免费 | 451篇 |
国内免费 | 774篇 |
专业分类
化学 | 2436篇 |
晶体学 | 35篇 |
力学 | 48篇 |
综合类 | 69篇 |
数学 | 4795篇 |
物理学 | 429篇 |
出版年
2024年 | 7篇 |
2023年 | 105篇 |
2022年 | 73篇 |
2021年 | 113篇 |
2020年 | 157篇 |
2019年 | 196篇 |
2018年 | 199篇 |
2017年 | 204篇 |
2016年 | 217篇 |
2015年 | 172篇 |
2014年 | 286篇 |
2013年 | 538篇 |
2012年 | 236篇 |
2011年 | 351篇 |
2010年 | 328篇 |
2009年 | 431篇 |
2008年 | 457篇 |
2007年 | 469篇 |
2006年 | 438篇 |
2005年 | 394篇 |
2004年 | 365篇 |
2003年 | 324篇 |
2002年 | 313篇 |
2001年 | 189篇 |
2000年 | 196篇 |
1999年 | 177篇 |
1998年 | 147篇 |
1997年 | 160篇 |
1996年 | 109篇 |
1995年 | 69篇 |
1994年 | 61篇 |
1993年 | 38篇 |
1992年 | 39篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 19篇 |
1988年 | 21篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 22篇 |
1981年 | 10篇 |
1980年 | 21篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1974年 | 4篇 |
排序方式: 共有7812条查询结果,搜索用时 15 毫秒
81.
带有弹性碰撞的离散的凝结方程 总被引:1,自引:0,他引:1
带有弹性碰撞的离散的凝结方程是反映粒子增长动力学的数学模型,它刻划了这样一种粒子反应系统;系统中任意两个粒子碰撞后一定的概率或者凝结成为更大的粒子,或者发生弹性碰撞.本文研究了这一系统发生冻肢的可能性,并给出了一个充分条件. 相似文献
82.
A. O. Manyashin A. I. Fomenko V. N. Storozhenko N. T. Berberova 《Russian Journal of Electrochemistry》2003,39(11):1240-1244
Stoichiometry and kinetics of reactions of 2,6-diphenyl-4-chloropyrylium, 4-chloroflavylium, 4-bromoflavylium, and 4-iodoflavylium perchlorates with nucleophiles N,N-dimethylaniline and n-phenylenediamine are studied using cyclic voltammetry and spectroscopy. Nucleophilic substitution in these compounds proceeds via the formation of a charge-transfer complex, which converts into a radical ion pair as a result of the electron transfer. Heterolytic clevage of the C–Hal bond occurs at the stage of pyranyl (flavanyl) radical. 相似文献
83.
84.
We wish to solve the heat equation ut=Δu-qu in Id×(0,T), where I is the unit interval and T is a maximum time value, subject to homogeneous Dirichlet boundary conditions and to initial conditions u(·,0)=f over Id. We show that this problem is intractable if f belongs to standard Sobolev spaces, even if we have complete information about q. However, if f and q belong to a reproducing kernel Hilbert space with finite-order weights, we can show that the problem is tractable, and can actually be strongly tractable. 相似文献
85.
Wolfgang W. Schoeller 《无机化学与普通化学杂志》2003,629(5):816-827
The particular role of the phosphaneiminato ligand as a donor is investigated for a) nitrenes (phosphinidenes) and carbenes and b) cubane formation with transition metals. Accordingly, and as shown for the case a) the ligand is a stronger π‐donor than an amino group and can be considered as a special case of imine‐type substituents. The latter are very effective in π‐donation. In the case b), i.e. the cubane formation with transition metals, one has to consider transition metals with a partially or completely filled d‐shell (with electrons). Hence depending on the transition metal, cubanes are build with weak ferromagnetic coupled or closed shell systems. For the cubanes with closed shell character the matter of insertion of halide anions is discussed. In the last chapter of the review the bond stretching in the dithionitrosyl complexes with rhenium is characterized. 相似文献
86.
Hye-Sun Jeon 《Tetrahedron letters》2004,45(38):7023-7026
Allylic sulfones undergo the conjugate addition to diethyl chloroisopropylidenemalonate, followed by intramolecular cyclopropanation. DBU-promoted ring opening and subsequent desulfonation reactions of the resulting adduct produce the conjugated polyene chains with the 1,4-dimethyl substitution. 相似文献
87.
Veli B. Shakhmurov 《Journal of Mathematical Analysis and Applications》2004,292(2):605-620
This study focuses on nonlocal boundary value problems (BVP) for degenerate elliptic differential-operator equations (DOE), that are defined in Banach-valued function spaces, where boundary conditions contain a degenerate function and a principal part of the equation possess varying coefficients. Several conditions obtained, that guarantee the maximal Lp regularity and Fredholmness. These results are also applied to nonlocal BVP for regular degenerate partial differential equations on cylindrical domain to obtain the algebraic conditions that ensure the same properties. 相似文献
88.
The hyperreal numbers of nonstandard analysis are characterized in purely algebraic terms as homomorphic images of a suitable class of rings of functions.
89.
S. Alpay E. Yu. Emel'yanov Z. Ercan 《Proceedings of the American Mathematical Society》2004,132(12):3627-3628
In this paper we give a characterization of order ideals in Riesz spaces.
90.
本文在Q-正则Loewner空间中用环模不等式刻划了拟对称映射.另外,在 Q-维Ahlfors-David正则空间中建立了拟对称映射作用下的Grotzsch-Teichmuller型 模不等式,它是通过伸张系数的积分平均来表示. 相似文献