全文获取类型
收费全文 | 3575篇 |
免费 | 218篇 |
国内免费 | 14篇 |
专业分类
化学 | 2702篇 |
晶体学 | 16篇 |
力学 | 76篇 |
数学 | 475篇 |
物理学 | 538篇 |
出版年
2023年 | 50篇 |
2022年 | 41篇 |
2021年 | 65篇 |
2020年 | 136篇 |
2019年 | 146篇 |
2018年 | 64篇 |
2017年 | 42篇 |
2016年 | 148篇 |
2015年 | 143篇 |
2014年 | 132篇 |
2013年 | 187篇 |
2012年 | 289篇 |
2011年 | 294篇 |
2010年 | 157篇 |
2009年 | 109篇 |
2008年 | 219篇 |
2007年 | 166篇 |
2006年 | 153篇 |
2005年 | 178篇 |
2004年 | 119篇 |
2003年 | 93篇 |
2002年 | 79篇 |
2001年 | 70篇 |
2000年 | 56篇 |
1999年 | 47篇 |
1998年 | 44篇 |
1997年 | 34篇 |
1996年 | 50篇 |
1995年 | 47篇 |
1994年 | 34篇 |
1993年 | 29篇 |
1992年 | 33篇 |
1991年 | 29篇 |
1990年 | 13篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 27篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1977年 | 15篇 |
1976年 | 7篇 |
1975年 | 14篇 |
1974年 | 8篇 |
1973年 | 9篇 |
排序方式: 共有3807条查询结果,搜索用时 15 毫秒
1.
Interactions of Pt‐ttpy with G‐Quadruplexes Originating from Promoter Region of the c‐myc Gene Deciphered by NMR and Gel Electrophoresis Analysis 下载免费PDF全文
2.
Phase Relations and Sodium Ion Conductivity within the Quasi-binary System Na2SiF6/Na2AIF6 . The phase diagram of the Na2SiF6/Na3AlF6 system has been determined by means of x-ray powder diffraction, thermal analysis and conductivity measurements in the sub-solidus region. Na3AlF6 accomodates up to 73 mol.-% Na2SiF6 maintaining the crystal structure type. The sodium ion conductivity increases by about five orders of magnitude upon doping Na3AlF6 with Na2SiF6. 相似文献
3.
Evolutionary algorithms are applied as problem-independent optimization algorithms. They are quite efficient in many situations. However, it is difficult to analyze even the behavior of simple variants of evolutionary algorithms like the (1+1) EA on rather simple functions. Nevertheless, only the analysis of the expected run time and the success probability within a given number of steps can guide the choice of the free parameters of the algorithms. Here static (1+1) EAs with a fixed mutation probability are compared with dynamic (1+1) EAs with a simple schedule for the variation of the mutation probability. The dynamic variant is first analyzed for functions typically chosen as example-functions for evolutionary algorithms. Afterwards, it is shown that it can be essential to choose the suitable variant of the (1+1) EA. More precisely, functions are presented where each static (1+1) EA has exponential expected run time while the dynamic variant has polynomial expected run time. For other functions it is shown that the dynamic (1+1) EA has exponential expected run time while a static (1+1) EA with a good choice of the mutation probability has polynomial run time with overwhelming probability. 相似文献
4.
If the Riemann–Christoffel tensor associated with a field of class of positive definite symmetric matrices of order three vanishes in a connected and simply connected open subset , then this field is the metric tensor field associated with a deformation of class of the set , uniquely determined up to isometries of . We establish here that the mapping defined in this fashion is continuous, for ad hoc metrizable topologies. To cite this article: P.G. Ciarlet, F. Laurent, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 489–493. 相似文献
5.
6.
We obtain asymptotic formulas for all the moments of certain arithmetic functions with linear recurrence sequences. We also apply our results to obtain asymptotic formulas for some mean values related to average orders of elements in finite fields. 相似文献
7.
Synthesis and Structure of K3N Two phases in the binary system K/N have been obtained via co‐deposition of potassium and nitrogen onto polished sapphire at 77 K and subsequent heating to room temperature. The powder diffraction pattern of one of these phases can be satisfactorily interpreted by assuming the composition K3N, and the anti‐TiI3 structure‐type, which is also adopted by Cs3O. The resulting hexagonal lattice constants are: a = 779.8(2), c = 759.2(9) pm, Z = 2, P63/mcm. Comparison with possible structures of K3N generated by computational methods and refined at Hartree‐Fock‐ and DFT level, reveals that the energetically most favoured structure has not formed (presumable Li3P‐type), but instead one of those with very low density. In this respect, the findings for K3N are analogous to the results on Na3N. The thermal evolution of the deposited starting mixture has been investigated. Hexagonal K3N transforms to another K/N phase at 233 K. Its XRD can be fully indexed resulting in an orthorhombic cell a = 1163, b = 596, c = 718 pm. Decomposition leaving elemental potassium as the only residue occurs at 263 K. 相似文献
8.
9.
10.
Wendelin Winfried Knotz Florian Schramm Hans-Wolfgang 《Monatshefte für Chemie / Chemical Monthly》1975,106(1):159-168
Monatshefte für Chemie - Chemical Monthly - Primary, secondary and tertiary aliphatic alcohols quickly react with 1-chloromethyl-isatin (1) to give good yields of alkoxymethylisatines4-novel... 相似文献