全文获取类型
收费全文 | 3056篇 |
免费 | 154篇 |
国内免费 | 9篇 |
专业分类
化学 | 2116篇 |
晶体学 | 3篇 |
力学 | 45篇 |
数学 | 427篇 |
物理学 | 463篇 |
无线电 | 165篇 |
出版年
2023年 | 28篇 |
2022年 | 23篇 |
2021年 | 55篇 |
2020年 | 62篇 |
2019年 | 71篇 |
2018年 | 39篇 |
2017年 | 34篇 |
2016年 | 95篇 |
2015年 | 119篇 |
2014年 | 119篇 |
2013年 | 176篇 |
2012年 | 239篇 |
2011年 | 232篇 |
2010年 | 142篇 |
2009年 | 125篇 |
2008年 | 167篇 |
2007年 | 165篇 |
2006年 | 179篇 |
2005年 | 157篇 |
2004年 | 173篇 |
2003年 | 125篇 |
2002年 | 102篇 |
2001年 | 59篇 |
2000年 | 33篇 |
1999年 | 38篇 |
1998年 | 44篇 |
1997年 | 40篇 |
1996年 | 26篇 |
1995年 | 39篇 |
1994年 | 39篇 |
1993年 | 21篇 |
1992年 | 26篇 |
1991年 | 22篇 |
1990年 | 13篇 |
1989年 | 21篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 24篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1974年 | 6篇 |
1973年 | 11篇 |
1970年 | 5篇 |
排序方式: 共有3219条查询结果,搜索用时 15 毫秒
991.
992.
Adsorption of I2 by Macrocyclic Polyazadithiophenolato Complexes Mediated by Charge‐Transfer Interactions 下载免费PDF全文
Matthias Golecki Norman Beyer Dr. Gunther Steinfeld Dr. Vasile Lozan Dr. Sergei Voitekhovich Dr. Muhamed Sehabi Dr. Jens Möllmer Prof. Dr. Hans‐Jörg Krüger Prof. Dr. Berthold Kersting 《Angewandte Chemie (International ed. in English)》2014,53(37):9949-9952
The macrocyclic complex [Ni2(L)(OAc)]ClO4 ( 1 ) adsorbs up to 17 molar equivalents (>270 wt %) of iodine, although it does not exhibit permanent porosity. Vibrational spectroscopic and crystallographic studies reveal that two I2 molecules are captured by means of thiophenolate→I2 charge‐transfer interactions, which enable the diffusion and sorption of further I2 molecules in a polyiodide‐like network. The efficient sorption and desorption characteristics make this material suitable for accommodation, sensing, and slow release of I2. 相似文献
993.
994.
在实现三电平逆变器全功能PWM单元时,用于决定开关序列以及必须的死区时间的数字逻辑,可以和故障诊断以及控制软核CPU一起集成在一个廉价的FPGA里面。因为简明的VHDL各自的状态机编程实现方案非常迅速,即使在非常高的开关频率下仍然能够采用低价高效的单芯片实现上述功能。 相似文献
995.
996.
997.
Oscillatory shear measurements on a series of branched graft polystyrenes (PS) synthesized by the macromonomer technique are presented. The graft PS have similar molar masses (M
w
between 1.3×105 g/mol and 2.4×105 g/mol) and a polydispersity M
w
/M
n
around 2. The molar masses of the grafted side chains M
w,br range from 6.8×103 g/mol to 5.8×104 g/mol, which are well below and above the critical entanglement molar mass M
c of linear polystyrene. The average number
of side chains per molecule ranges from 0.6 to 6.7. The oscillatory measurements follow the time–temperature superposition principle. The shift factors do not depend on the number of branches. The zero-shear viscosities of all graft PS are lower than those of linear PS with the same molar mass, which can be attributed to the smaller coil size of the branched molecules. It is shown that the influence of branching on the frequency dependence of the dynamic moduli is weak for all graft PS that were investigated, which can be explained by the low entanglement density.Electronic Supplementary Material Supplementary material is available for this article at
This article has already been published online first (DOI: ). Due to an oversight at the publisher's, this version contained several mistakes. The article is herewith republished in its entirety as a "publisher's erratum". 相似文献
998.
The flow around bridge structures is a recent research topic, given the significance of bridges as basic engineering infrastructures.
This study investigates the internal flow features around circular bridge piers by Particle Image Velocimetry applied both in the horizontal and vertical planes and therefore allowing for a quasi-spatial visualization of the velocity
field. The temporal evolution of the vertical deflected flow at the pier front and the horseshoe vortex inside the increasing
scour hole were explored resulting in the velocity and vorticity profiles. This work, therefore, provides novel insight into
the complex and fascinating two-phase flow around circular bridge piers placed in loose sediment and provides an experimental
data basis for advanced numerical simulation. 相似文献
999.
Jens Wintermayr 《PAMM》2016,16(1):885-886
We give a definition for positivity on an extrapolation space for positive strongly continuous semigroups. We prove a perturbation result on AM spaces for positive semigroups by positive operators. Finally, we give an example for this kind of perturbations. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
1000.
The M.E.S.S. software suite for solving large scale matrix equations and related problems is the successor of the obsolete LyaPack MATLAB® toolbox. The software suite consists of a new MATLAB toolbox and a separate C library C-M.E.S.S. which works independent from MATLAB. Due to the fact that many scientists use Python with NumPy and SciPy for their computations, we want to provide the key algorithms of M.E.S.S. there as well. In this paper, we describe and compare two possible approaches for the implementation, with special focus on their multicore performance. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献