全文获取类型
收费全文 | 5593篇 |
免费 | 679篇 |
国内免费 | 746篇 |
专业分类
化学 | 4255篇 |
晶体学 | 75篇 |
力学 | 262篇 |
综合类 | 77篇 |
数学 | 883篇 |
物理学 | 1466篇 |
出版年
2023年 | 110篇 |
2022年 | 140篇 |
2021年 | 190篇 |
2020年 | 249篇 |
2019年 | 260篇 |
2018年 | 216篇 |
2017年 | 222篇 |
2016年 | 265篇 |
2015年 | 305篇 |
2014年 | 352篇 |
2013年 | 516篇 |
2012年 | 512篇 |
2011年 | 502篇 |
2010年 | 394篇 |
2009年 | 366篇 |
2008年 | 428篇 |
2007年 | 356篇 |
2006年 | 326篇 |
2005年 | 225篇 |
2004年 | 177篇 |
2003年 | 121篇 |
2002年 | 119篇 |
2001年 | 76篇 |
2000年 | 67篇 |
1999年 | 63篇 |
1998年 | 40篇 |
1997年 | 40篇 |
1996年 | 33篇 |
1995年 | 16篇 |
1994年 | 27篇 |
1993年 | 25篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 10篇 |
1978年 | 18篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有7018条查询结果,搜索用时 15 毫秒
1.
2.
Nonlinear Dynamics - In this paper, we study a delayed diffusive predator–prey model with nonlocal competition in prey and habitat complexity. The local stability of coexisting equilibrium is... 相似文献
3.
We describe the static charge susceptibility and correlation function of the charge density in the twodimensional t-J-V model based on the method of equations of motion for the relaxation functions of the Hubbard operators. We obtain the dependence of the susceptibility and correlation function on the hole concentration and temperature. Charge density waves can develop if the intersite Coulomb interaction is sufficiently strong. 相似文献
4.
Acta Mathematicae Applicatae Sinica, English Series - For the variational inequality with symmetric cone constraints problem, we consider using the inexact modified Newton method to efficiently... 相似文献
5.
Jin Zhang Weiwei Lei Jurg Schutz Dan Liu Bin Tang Chun H. Wang Xungai Wang 《Journal of Polymer Science.Polymer Physics》2019,57(7):406-414
New multifunctional materials with both high structural and gas barrier performances are important for a range of applications. Herein we present a one‐step mechanochemical process to prepare molybdenum disulfide (MoS2) nanosheets with hydroxy functional groups that can simultaneously improve mechanical strength, thermal conductivity, and gas permittivity of a polymer composite. By homogeneously incorporating these functionalized MoS2 nanosheets at low loading of less than 1 vol %, a poly(vinyl alcohol) (PVA) polymer exhibits elongation at break of 154%, toughness of 82 MJ/m3, and in‐plane thermal conductivity of 2.31 W/m K. Furthermore, this composite exhibits significant gas barrier performance, reducing the permeability of helium by 95%. Under fire condition, the MoS2 nanosheets form thermally stable char, thus enhancing the material's resistance to fire. Hydrogen bonding has been identified as the main interaction mechanism between the nanofillers and the polymer matrix. The present results suggest that the PVA composite reinforced with 2D layered nanomaterial offers great potentials in packaging and fire retardant applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 406–414 相似文献
6.
7.
Ping Chen Yanhong Hao Xinxin Wang Prof. Dr. Dan Yuan Prof. Dr. Yingming Yao Prof. Dr. Lutz Ackermann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(30):7292-7297
Highly position selective alkylations of N-alkylindoles at C7-positions have been enabled by cationic zirconium complexes. The strategy provides a straightforward access to install alkyl groups at C7-positions of indoles without a complex directing group. Mechanistic studies provided support for the importance of Brønsted acids in the catalytic manifold. 相似文献
8.
在碳酸钾、碳酸锂和二氧化钛的混合原料中加入熔盐氯化钾,通过高温煅烧一步制备出钛酸锂钾片晶( K0.8 Li0.27Ti1.73O4, KLTO).通过控制熔盐的添加方式以及煅烧工艺(升温速率、煅烧时间)使材料的形貌朝着二维方向生长,并利用XRD和SEM等手段进行表征.分析发现:过快的升温速率或者较短的煅烧时间都会使材料朝三维方向生长成球状或者块状,反之则会使材料趋向一维方向生长成棒状;同时在煅烧温度达到一定值时再加入熔盐则更有利于片晶的生成.最终得到KLTO片状形貌的最佳控制工艺为:先以300 ℃/h升温至800 ℃后,再加入质量分数为40;的KCl熔盐,接着将升温速率变为200 ℃/h,加热至950 ℃,并在此温度下煅烧3 h. 相似文献
9.
Towards Fabrication of Atomic Dopant Wires via Monolayer Doping Patterned by Resist-Free Lithography 下载免费PDF全文
Fabrication of atomic dopant wires at large scale is challenging.We explored the feasibility to fabricate atomic dopant wires by nano-patterning self-assembled dopant carrying molecular monolayers via a resist-free lithographic approach.The resist-free lithography is to use electron beam exposure to decompose hydrocarbon contaminants in vacuum chamber into amorphous carbon that serves as an etching mask for nanopatterning the phosphorus-bearing monolayers.Dopant wires were fabricated in silicon by patterning diethyl vinylphosphonate monolayers into lines with a width ranging from 1 μm down to 8 nm.The dopants were subsequently driven into silicon to form dopant wires by rapid thermal annealing.Electrical measurements show a linear correlation between wire width and conductance,indicating the success of the monolayer patterning process at nanoscale.The dopant wires can be potentially scaled down to atomic scale if the dopant thermal diffusion can be mitigated. 相似文献
10.
Science China Chemistry - 相似文献