全文获取类型
收费全文 | 2449篇 |
免费 | 315篇 |
国内免费 | 183篇 |
专业分类
化学 | 1848篇 |
晶体学 | 30篇 |
力学 | 121篇 |
综合类 | 11篇 |
数学 | 255篇 |
物理学 | 682篇 |
出版年
2024年 | 3篇 |
2023年 | 53篇 |
2022年 | 72篇 |
2021年 | 77篇 |
2020年 | 88篇 |
2019年 | 115篇 |
2018年 | 91篇 |
2017年 | 61篇 |
2016年 | 101篇 |
2015年 | 122篇 |
2014年 | 136篇 |
2013年 | 186篇 |
2012年 | 219篇 |
2011年 | 229篇 |
2010年 | 140篇 |
2009年 | 121篇 |
2008年 | 157篇 |
2007年 | 138篇 |
2006年 | 154篇 |
2005年 | 117篇 |
2004年 | 103篇 |
2003年 | 63篇 |
2002年 | 70篇 |
2001年 | 32篇 |
2000年 | 23篇 |
1999年 | 44篇 |
1998年 | 23篇 |
1997年 | 28篇 |
1996年 | 34篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1985年 | 7篇 |
1984年 | 10篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1957年 | 1篇 |
1938年 | 1篇 |
排序方式: 共有2947条查询结果,搜索用时 31 毫秒
81.
82.
83.
84.
85.
Dawei Xu Li Zheng Xinhong Cheng Gang Wang Qian Wang Wenbo Xin Peiyi Ye Lingyan Shen Yuehui Yu 《Physics letters. A》2019,383(25):3134-3137
The efficient passivation of in situ NH3-plasma pre-treatment and its regulation of the band alignment between HfO2 and 4H-SiC have been investigated by XPS. With in situ NH3-plasma passivation by PEALD, a VBO of 0.72 eV and a CBO of 1.54 eV can be obtained across the HfO2/4H-SiC interface. The Si-O bonds components reduction in the passivated interface layers will lead to band bending or band shift at the interface and regulate the band alignments between HfO2 and 4H-SiC. The physical mechanism investigation of band alignments can be a cornerstone for the application of HfO2/4H-SiC heterojunctions in the high-power devices. 相似文献
86.
Novel cinchonine ammonium salt derivatives have been prepared by 1,3‐dipolar cycloaddition. Their chiral catalytic efficacy was investigated in the asymmetric alkylation of N‐diphenylmethyleneglycine t‐butyl ester in the water phase. As the special structure of the catalyst, its asymmetric alkylation catalytic behavior both in organic solvents and in water is satisfactory, which is environmentally friendly. 相似文献
87.
Dr. Maria Książek Dr. Marek Weselski Marcin Kaźmierczak Aleksandra Tołoczko Dr. Miłosz Siczek Dr. Piotr Durlak Dr. Juliusz A. Wolny Prof. Dr. Volker Schünemann Prof. Dr. Joachim Kusz Dr. Robert Bronisz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(63):14419-14434
Reaction of 1,2-di(tetrazol-2-yl)ethane (ebtz) with Fe(BF4)2⋅6 H2O in different nitriles yields one-dimensional coordination polymers [Fe(ebtz)2(RCN)2](BF4)2⋅nRCN (n=2 for R=CH3 ( 1 ) and n=0 for R=C2H5 ( 2 ) C3H7 ( 3 ), C3H5 ( 4 ), CH2Cl ( 5 )) exhibiting spin crossover (SCO). SCO in 1 and 3 – 5 is complete and occurs above 160 K. In 2 , it is shifted to lower temperatures and is accompanied by wide hysteresis (T1/2↓=78 K, T1/2↑=123 K) and proceeds extremely slowly. Isothermal (80 K) time-resolved single-crystal X-ray diffraction studies revealed a complex nature for the HS→LS transition in 2 . An initial, slow stage is associated with shrinkage of polymeric chains and with reduction of volume at 77 % (in relation to the difference between cell volumes VHS−VLS) whereas only 16 % of iron(II) ions change spin state. In the second stage, an abrupt SCO occurs, associated with breathing of the crystal lattice along the direction of the Fe–nitrile bonds, while the nitriles reorient. HS→LS switching triggered by light (808 nm) reveals the coupling of spin state and nitrile orientation. The importance of this coupling was confirmed by studies of [Fe(ebtz)2(C2H5CN/C3H7CN)2](BF4)2 mixed crystals ( 2 a , 2 b ), showing a shift of T1/2 to higher values and narrowing of the hysteresis loop concomitant with an increase of the fraction of butyronitrile. This increase reduces the capability of nitrile molecules to reorient. Density functional theory (DFT) studies of models of 1 – 5 suggest a particular possibility of 2 to adopt a low (140–145°) value of its Fe-N-C(propionitrile) angle. 相似文献
88.
Quanqing Li Kaimin Teng Xian Wu Wenbo Wang 《Mathematical Methods in the Applied Sciences》2019,42(5):1480-1487
In this paper, we study the following fractional Schrödinger equation with critical or supercritical growth where 0 < s < 1, N > 2s, λ > 0, , , ( ? Δ)s denotes the fractional Laplacian of order s and f is a continuous superlinear but subcritical function. Under some suitable conditions, we prove that the equation has a nontrivial solution for small λ > 0 by variational methods. Our main contribution is related to the fact that we are able to deal with the case . 相似文献
89.
Birnšteinová Š. Hnatič M. Lučivjanský T. Mižišin L. Škultéty V. 《Theoretical and Mathematical Physics》2019,200(3):1335-1347
Theoretical and Mathematical Physics - We study an instructive model of the directed percolation process near its second-order phase transition between absorbing and active states. We first express... 相似文献
90.
Lei Wang Kenan Zhang Yuzhuo Wang Wenbo Li Mingjie Chen Prof. Dr. Junliang Zhang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(11):4451-4457
Reported here is a highly efficient Pd/Xiang-Phos catalyzed enantioselective carboetherification of alkenyl oximes with either aryl or alkenyl halides, delivering various chiral 3,5-disubstituted and 3,5,5-trisubstituted isoxazolines in good yields with up to 97 % ee. The sterically bulky and electron-rich (S,Rs)- NMe-X2 ligand is responsible for the excellent reactivities and enantioselectivities. The salient features of this transformation include mild reaction conditions, general substrate scope, good functional-group tolerance, good yields, high enantioselectivities, easy scale-up, and application in the late-stage modification of bioactive compounds. The obtained products can be readily transformed into useful chiral 1,3-aminoalcohols. 相似文献