全文获取类型
收费全文 | 2344篇 |
免费 | 106篇 |
国内免费 | 9篇 |
专业分类
化学 | 1609篇 |
晶体学 | 14篇 |
力学 | 77篇 |
数学 | 333篇 |
物理学 | 426篇 |
出版年
2023年 | 19篇 |
2022年 | 50篇 |
2021年 | 51篇 |
2020年 | 59篇 |
2019年 | 71篇 |
2018年 | 51篇 |
2017年 | 38篇 |
2016年 | 99篇 |
2015年 | 68篇 |
2014年 | 81篇 |
2013年 | 162篇 |
2012年 | 166篇 |
2011年 | 175篇 |
2010年 | 104篇 |
2009年 | 88篇 |
2008年 | 150篇 |
2007年 | 131篇 |
2006年 | 105篇 |
2005年 | 105篇 |
2004年 | 101篇 |
2003年 | 72篇 |
2002年 | 90篇 |
2001年 | 30篇 |
2000年 | 36篇 |
1999年 | 19篇 |
1998年 | 24篇 |
1997年 | 19篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 13篇 |
1991年 | 19篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 15篇 |
1978年 | 19篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1968年 | 4篇 |
排序方式: 共有2459条查询结果,搜索用时 15 毫秒
71.
Dr. Xisen Hou Prof. Chenfeng Ke Dr. Yu Zhou Dr. Zhuang Xie Dr. Ahmed Alngadh Dr. Denis T. Keane Dr. Majed S. Nassar Dr. Youssry Y. Botros Prof. Chad A. Mirkin Prof. J. Fraser Stoddart 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(35):12301-12306
Covalent and supramolecular polymerizations, both of which offer their own unique advantages, have emerged as popular strategies for making artificial materials. Herein, we describe a concurrent covalent and supramolecular polymerization strategy—namely, one which utilizes 1) a bis‐azide‐functionalized diazaperopyrenium dication that undergoes polymeriation covalently with a bis‐alkyne‐functionalized biphenyl derivative in one dimension as a result of a rapid and efficient β‐cyclodextrin(CD)‐accelerated, cucurbit[6]uril(CB)‐templated azide–alkyne cycloaddition, while 2) the aromatic core of the dication is able to dimerize in a criss‐cross fashion by dint of π–π interactions, enabling simultaneous supramolecular assembly, resulting in an extended polymer network in an orthogonal dimension. 相似文献
72.
Denis N. Tomilin Lyubov N. Sobenina Marina V. Markova Maxim D. Gotsko Igor A. Ushakov Vladimir I. Smirnov 《合成通讯》2013,43(14):1652-1661
5-Acylethynylpyrrole-2-carbaldehydes have been synthesized from the protected pyrrole-2-carbaldehydes by their transition-metal-free topochemical mechanoactivated ethynylation with acylbromoacetylenes in a solid Al2O3 medium (room temperature, 6 h, 41–54% yields). 相似文献
73.
74.
α-Functionalized chlorophosphonic monoesters were easily prepared by a selective chlorination of the corresponding phosphonic diesters with phosphorus oxychloride. 相似文献
75.
76.
We study random Hamiltonians on finite-size cubes and waveguide segments of increasing diameter. The number of random parameters determining the operator is proportional to the volume of the cube. In the asymptotic regime where the cube size, and consequently the number of parameters as well, tends to infinity, we derive deterministic and probabilistic variational bounds on the lowest eigenvalue, i.e., the spectral minimum, as well as exponential off-diagonal decay of the Green function at energies above, but close to the overall spectral bottom. 相似文献
77.
The note shows that, for every pair of contractions, a trace formula of Koplienko holds with a summable spectral shift function, see Theorem 1 below. This answers a question by F. Gesztesy, A. Pushnitski, B. Simon (see Zh Mat
Fiz Anal Geom 4(1):63–107, 202, 2008, Open Question 11.2). 相似文献
78.
79.
We prove a compact expression for the Cauchy-Kovalevskaya extension in the setting of discrete Clifford analysis; it seamlessly simplifies to the well-know exponential formula in the continuous setting when the discrete step size tends to zero. 相似文献
80.
In this work, biaxially stretched polymer foams with well‐defined cellular structures were prepared from polyethylene via blown‐film extrusion and subjected to corona charging to produce a piezoelectric response. The charging parameters were first optimized in terms of charging voltage and needle distance, as well as the gas type and pressure to investigate their effect on the piezoelectric coefficient (d33). The results show that samples charged under nitrogen (N2) at 100 kPa had better d33 coefficient than those charged under ambient air or N2 at 20 kPa. Moreover, 2 different thermal pressure treatments were imposed to obtain an optimized eye‐like cellular structure with different cell aspect ratios (AR). The results showed that when the cells were elongated in both the longitudinal and transverse directions (higher AR), higher d33 coefficients were achieved. From all the samples produced, the best results were obtained for a longitudinal aspect ratio (AR‐L) of 7.1, a transversal aspect ratio (AR‐T) of 4.6, and a relative foam density of 0.52 leading to a d33 coefficient of 935 pC/N. This coefficient was further increased using reverse charging and multilayered films, reaching a maximum of 2550 pC/N. This value is much higher than typical ones reported so far for any polyethylene and polypropylene ferroelectrets. These results could increase the use of polyethylene in piezoelectric applications as these materials are very attractive for the large‐scale production of electret‐based sensors and transducers due to their low cost and easy processing. 相似文献