全文获取类型
收费全文 | 2455篇 |
免费 | 95篇 |
国内免费 | 14篇 |
专业分类
化学 | 1762篇 |
晶体学 | 10篇 |
力学 | 46篇 |
数学 | 397篇 |
物理学 | 349篇 |
出版年
2022年 | 14篇 |
2021年 | 26篇 |
2020年 | 55篇 |
2019年 | 37篇 |
2018年 | 31篇 |
2017年 | 21篇 |
2016年 | 73篇 |
2015年 | 60篇 |
2014年 | 65篇 |
2013年 | 100篇 |
2012年 | 96篇 |
2011年 | 101篇 |
2010年 | 90篇 |
2009年 | 80篇 |
2008年 | 101篇 |
2007年 | 102篇 |
2006年 | 122篇 |
2005年 | 103篇 |
2004年 | 93篇 |
2003年 | 82篇 |
2002年 | 97篇 |
2001年 | 45篇 |
2000年 | 49篇 |
1999年 | 53篇 |
1998年 | 49篇 |
1997年 | 54篇 |
1996年 | 55篇 |
1995年 | 53篇 |
1994年 | 49篇 |
1993年 | 38篇 |
1992年 | 37篇 |
1991年 | 36篇 |
1990年 | 27篇 |
1989年 | 41篇 |
1988年 | 22篇 |
1987年 | 15篇 |
1986年 | 24篇 |
1985年 | 25篇 |
1984年 | 29篇 |
1983年 | 32篇 |
1981年 | 21篇 |
1980年 | 25篇 |
1979年 | 31篇 |
1978年 | 27篇 |
1977年 | 23篇 |
1976年 | 22篇 |
1975年 | 16篇 |
1974年 | 16篇 |
1973年 | 19篇 |
1971年 | 20篇 |
排序方式: 共有2564条查询结果,搜索用时 15 毫秒
91.
Frontispiece: Glycoluril‐Derived Molecular Clips are Potent and Selective Receptors for Cationic Dyes in Water
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
92.
93.
The shadow of a black hole is usually calculated, either analytically or numerically, on the assumption that the black hole is eternal, i.e., that it has existed for all time. Here we ask the question of how this shadow comes about in the course of time when a black hole is formed by gravitational collapse. To that end we consider a star that is spherically symmetric, dark and non-transparent and we assume that it begins, at some instant of time, to collapse in free fall like a ball of dust. We analytically calculate the dependence on time of the angular radius of the shadow, first for a static observer who is watching the collapse from a certain distance and then for an observer who is falling towards the centre following the collapsing star. 相似文献
94.
Volker Elling 《Communications in Mathematical Physics》2016,348(1):27-68
We construct a class of self-similar 2d incompressible Euler solutions that have initial vorticity of mixed sign. The boundaries between regions of positive and negative vorticity form algebraic spirals, similar to the Kaden spiral and as opposed to Prandtl’s logarithmic vortex spirals. Also unlike the Prandtl case, spirals are not initially present. 相似文献
95.
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
96.
97.
Sarah R. Geenen Lysander Presser Dr. Torsten Hölzel Prof. Dr. Christian Ganter Prof. Dr. Thomas J. J. Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(36):8064-8075
Differently 5-substituted 8-methoxypsoralens can be synthesized by an efficient synthetic route with various cross-coupling methodologies, such as Suzuki, Sonogashira and Heck reaction. Compared to previously synthesized psoralens, thereby promising daylight absorbing compounds as potentially active agents against certain skin diseases can be readily accessed. Extensive investigations of all synthesized psoralen derivatives reveal fluorescence in the solid state as well as several distinctly emissive derivatives in solution. Donor-substituted psoralens exhibit remarkable photophysical properties, such as high fluorescence quantum yields and pronounced emission solvatochromicity and acidochromicity, which were scrutinized by Lippert–Mataga and Stern–Volmer plots. The results indicate that the compounds exceed the limit of visible light, a significant factor for potential applications as an active agent. In addition, (TD)DFT calculations were performed to elucidate the underlying electronic structure and to assign experimentally obtained data. 相似文献
98.
The European Physical Journal H - This is a tutorial for the many-worlds theory by Everett, which includes some of my personal views. It has two main parts. The first main part shows the emergence... 相似文献
99.
100.
Róbert Bordás Volker John Ellen Schmeyer Dominique Thévenin 《Theoretical and Computational Fluid Dynamics》2013,27(3-4):253-271
The droplet size distribution in a turbulent flow field is considered and modeled by means of a population balance system. This paper studies different numerical methods for the 4D population balance equation and their impact on an output of interest, the time-space-averaged droplet size distribution at the outlet, which is known from experiments. These methods include different interpolations of the experimental data at the inlet, various discretizations in time and space, and different schemes for computing the coalescence integrals. It will be shown that noticeable changes in the output of interest might occur. In addition, the computational efficiency of the studied methods is discussed. 相似文献