全文获取类型
收费全文 | 128872篇 |
免费 | 9267篇 |
国内免费 | 19988篇 |
专业分类
化学 | 105778篇 |
晶体学 | 2717篇 |
力学 | 2963篇 |
综合类 | 1179篇 |
数学 | 15367篇 |
物理学 | 30123篇 |
出版年
2024年 | 273篇 |
2023年 | 1562篇 |
2022年 | 3408篇 |
2021年 | 3366篇 |
2020年 | 3838篇 |
2019年 | 3573篇 |
2018年 | 3020篇 |
2017年 | 4211篇 |
2016年 | 4367篇 |
2015年 | 3667篇 |
2014年 | 5049篇 |
2013年 | 10374篇 |
2012年 | 8551篇 |
2011年 | 7613篇 |
2010年 | 6521篇 |
2009年 | 8517篇 |
2008年 | 8522篇 |
2007年 | 8751篇 |
2006年 | 7996篇 |
2005年 | 6852篇 |
2004年 | 6385篇 |
2003年 | 5319篇 |
2002年 | 6217篇 |
2001年 | 3923篇 |
2000年 | 3641篇 |
1999年 | 3279篇 |
1998年 | 2840篇 |
1997年 | 2280篇 |
1996年 | 1951篇 |
1995年 | 1860篇 |
1994年 | 1655篇 |
1993年 | 1369篇 |
1992年 | 1265篇 |
1991年 | 890篇 |
1990年 | 712篇 |
1989年 | 674篇 |
1988年 | 522篇 |
1987年 | 393篇 |
1986年 | 346篇 |
1985年 | 324篇 |
1984年 | 313篇 |
1983年 | 169篇 |
1982年 | 256篇 |
1981年 | 246篇 |
1980年 | 242篇 |
1979年 | 237篇 |
1978年 | 208篇 |
1977年 | 160篇 |
1976年 | 131篇 |
1973年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
蕴涵代数与BCK代数 总被引:6,自引:0,他引:6
系统研究 Fuzzy蕴涵代数与 BCK代数之间的关系 ,给出 MV代数与 BCK代数之间的联系 ,建立正则 FI代数和对合 BCK代数的对偶代数 相似文献
102.
Let T and S be invertible measure preserving transformations of a probability measure space (X, ℬ, μ). We prove that if the group generated by T and S is nilpotent, then exists in L
2-norm for any u, v∈L
∞(X, ℬ, μ). We also show that for A∈ℬ with μ(A)>0 one has . By the way of contrast, we bring examples showing that if measure preserving transformations T, S generate a solvable group, then (i) the above limits do not have to exist; (ii) the double recurrence property fails, that
is, for some A∈ℬ, μ(A)>0, one may have μ(A∩T
-n
A∩S
-
n
A)=0 for all n∈ℕ. Finally, we show that when T and S generate a nilpotent group of class ≤c, in L
2(X) for all u, v∈L
∞(X) if and only if T×S is ergodic on X×X and the group generated by T
-1
S, T
-2
S
2,..., T
-c
S
c
acts ergodically on X.
Oblatum 19-V-2000 & 5-VII-2001?Published online: 12 October 2001 相似文献
103.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
104.
Summary In 1980 Dahmen-DeVore-Scherer introduced a modulus of continuity which turns out to reflect invariance properties of compound cubature rules effectively. Accordingly, sharp error bounds are derived, the existence of relevant counterexamples being a consequence of a quantitative resonance principle, established previously. 相似文献
105.
A comparative study of the structure and crystallization of bulk metallic amorphous rod Pr60Ni30Al10 and melt-spun metallic amorphous ribbon Al87Ni10Pr3 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pr-based bulk metallic amorphous (BMA) rods (Pr60Ni30Al10) and Al-based amorphous ribbons (Al87Ni10Pr3) have been prepared by using copper mould casting and single roller melt-spun techniques, respectively. Thermal parameters deduced from differential scanning calorimeter (DSC) indicate that the glass-forming ability (GFA) of Pr60Ni30Al10 BMA rod is far higher than that of Al87Ni10Pr3 ribbon. A comparative study about the differences in structure between the two kinds of glass-forming alloys, superheated viscosity and crystallization are also made. Compared with the amorphous alloy Al87Ni10Pr3, the BMA alloy Pr60Ni30Al10 shows high thermal stability and large viscosity, small diffusivity at the same superheated temperatures. The results of x-Ray diffraction (XRD) and transmission electron microscope (TEM) show the pronounced difference in structure between the two amorphous alloys. Together with crystallization results, the main structure compositions of the amorphous samples are confirmed. It seems that the higher the GFA, the more topological type clusters in the Pr-Ni-Al amorphous alloys, the GFAs of the present glass-forming alloys are closely related to their structures. 相似文献
106.
GAO Jing ZHOU Xiaohua CHEN Xun Chongqing University Chemical Engineering Department Chongqing China 《Chinese Journal of Reactive Polymers》2006,(2)
1. INTRODUCTION In the process of coking plant, about 30%~35% sulfur is transformed to H2S and some other sulfide, which form impurity in coal gas together with NH3 and HCN. Only 0.1% H2S containing in air can lead to die, so it is very important to carry on desulphurization and decyanation with coal gas [1~3]. Currently desulphurization and decyanation craft technique have Dry Oxidation Technology, Wet Oxidation Technology and Liquid Absorption Technology [2] three main kinds. The… 相似文献
107.
Electron spin resonance spectra of Mn2+ in diluted solid solutions of MnO2 in Y2O3 have been studied at room temperature for Mn concentrations between 0.20 and 2.00 mol%. Isolated Mn2+ ions in sites with two different symmetries were observed, as well as Mn2+ ions coupled by the exchange interaction. The relative concentration of isolated to coupled Mn2+ ions decreases with increasing manganese concentration. The results are consistent with the assumption that the manganese ions occupy preferentially the C2 symmetry sites. A theoretical calculation based on this model yields an effective range of the exchange interaction between Mn2+ ions of 0.53 nm, of the same order as that of Mn2+ ions in CaO. 相似文献
108.
许多实验对用CsI(Tl)闪烁晶体作为探测器来寻找和探测暗物质的可行性进行了研究.本工作利用8MeV单能中子轰击CsI(Tl)晶体探测器来研究Cs核和I核的QuenchingFactor.在数据处理中,运用脉冲形状甄别(PSD)方法来分辨反冲核信号和本底信号.实验结果表明,在7keV到132keV的能区中,Quench ingFactor随着反冲核能量的减少而增加.在探测暗物质的实验中,这一性质对于CsI(Tl)晶体探测器获得较低的能量阈值是很有利的. 相似文献
109.
We obtain a solution of the DGLAP equation for the gluon at low x first by expanding the gluon in a Taylor series and then using the method of characteristics. We test its validity by comparing
it with that of Glück, Reya and Vogt. The convergence criteria of the approximation used are also discussed. We also calculate
εF
2(x,Q)2/ε In Q
2 using its approximate relations with the gluon distribution at low x. The predictions are then compared with the HERA data. 相似文献
110.