全文获取类型
收费全文 | 9779篇 |
免费 | 308篇 |
国内免费 | 63篇 |
专业分类
化学 | 6226篇 |
晶体学 | 54篇 |
力学 | 304篇 |
数学 | 1711篇 |
物理学 | 1252篇 |
无线电 | 603篇 |
出版年
2023年 | 66篇 |
2022年 | 212篇 |
2021年 | 253篇 |
2020年 | 213篇 |
2019年 | 203篇 |
2018年 | 179篇 |
2017年 | 144篇 |
2016年 | 337篇 |
2015年 | 296篇 |
2014年 | 304篇 |
2013年 | 573篇 |
2012年 | 660篇 |
2011年 | 716篇 |
2010年 | 442篇 |
2009年 | 441篇 |
2008年 | 658篇 |
2007年 | 582篇 |
2006年 | 558篇 |
2005年 | 467篇 |
2004年 | 426篇 |
2003年 | 339篇 |
2002年 | 328篇 |
2001年 | 134篇 |
2000年 | 101篇 |
1999年 | 90篇 |
1998年 | 92篇 |
1997年 | 111篇 |
1996年 | 108篇 |
1995年 | 67篇 |
1994年 | 94篇 |
1993年 | 63篇 |
1992年 | 61篇 |
1991年 | 46篇 |
1990年 | 63篇 |
1989年 | 56篇 |
1988年 | 45篇 |
1987年 | 48篇 |
1986年 | 32篇 |
1985年 | 53篇 |
1984年 | 64篇 |
1983年 | 46篇 |
1982年 | 47篇 |
1981年 | 33篇 |
1980年 | 44篇 |
1979年 | 29篇 |
1978年 | 34篇 |
1977年 | 31篇 |
1975年 | 14篇 |
1974年 | 16篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Munguia-Lopez Jose G. Juarez Rodrigo Muñoz-Sandoval Emilio Kalixto-Sanchez Marco A. Kinsella Joseph Matthew De Leon-Rodriguez Antonio 《Journal of nanoparticle research》2019,21(8):1-15
Journal of Nanoparticle Research - Workers are increasingly exposed to nanoparticles, mostly via inhalation. Respiratory protection is recommended as an additional control measure. Particulate... 相似文献
92.
Dr. Antonio Sánchez-Ruiz Dr. Julián Rodríguez-López Dr. Andrés Garzón-Ruiz Dr. Sonia B. Jiménez-Pulido Dr. Nuria A. Illán-Cabeza Dr. Amparo Navarro Dr. Joaquín C. García-Martínez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(61):13990-14001
Different molecular strategies have been carefully evaluated to produce solid-state luminescence enhancement (SLE) in compounds that show dark states in solution. A set of α-phenylstyrylarene derivatives with a butterfly shape have been designed and synthesised, for the first time, with the aim of improving the solid-state fluorescence emission of their parent styrylarene compounds. Although these butterfly molecules are not fluorescent in solution, one of them (1,2,4,5-tetra(α-phenylstyryl)benzene) exhibits a fluorescence quantum yield as high as 68 % in a drop-cast sample and 31 % in its crystalline form. In contrast, 1,3,5-tris(α-phenylstyryl)benzene and 4,6-bis(α-phenylstyryl)pyrimidine do not show SLE. A range of fluorescence spectroscopy experiments and DFT calculations were carried out to unravel the origin of different photophysical behaviour of these compounds in the solid state. The results indicate that a rational strategy to control the SLE effect in luminogens depends on a delicate balance between molecular properties and inter-/intramolecular interactions in the solid state. 相似文献
93.
Nonlinear Dynamics - This work explores the role of asymmetrical damping and geometrical nonlinearities in the suspension system of a simplified vehicle model in order to improve comfort. Improving... 相似文献
94.
Alessandro Passera Prof. Dr. Antonio Mezzetti 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(1):193-197
The bis(carbonyl) manganese(I) complex [Mn(CO)2( 1 )]Br ( 2 ) with a chiral (NH)2P2 macrocyclic ligand ( 1 ) catalyzes the asymmetric transfer hydrogenation of polar double bonds with 2-propanol as the hydrogen source. Ketones (43 substrates) are reduced to alcohols in high yields (up to >99 %) and with excellent enantioselectivities (90–99 % ee). A stereochemical model based on attractive CH–π interactions is proposed. 相似文献
95.
96.
Domnech-Carb Antonio Domnech-Casass Clara Pontones Jos Lus Ramos David 《Journal of Solid State Electrochemistry》2020,24(11):2853-2860
An electrochemical method for discriminating healthy and malignant tissues in prostate biopsies using the voltammetry of immobilized particles methodology is described. The method involves the sampling with graphite bars 0.5 mm in diameter on paraffin-impregnated cross sections of prostate tissues used in ordinary cytological evaluation after local staining with methylene blue (MB). The subsequent record of the voltammetric response of sample-modified graphite electrodes displays clearly different MB-centered features for healthy and malignant regions due to the different association of the dye to the respective cells.
相似文献97.
98.
We prove the following result concerning the degree spectrum of the atom relation on a computable Boolean algebra. Let be a computable Boolean algebra with infinitely many atoms and be the Turing degree of the atom relation of . If is a c.e. degree such that , then there is a computable copy of where the atom relation has degree . In particular, for every c.e. degree , any computable Boolean algebra with infinitely many atoms has a computable copy where the atom relation has degree .
99.
In the following,G denotes a finite group,r(G) the number of conjugacy classes ofG, β(G) the number of minimal normal subgroups ofG andα(G) the number of conjugate classes ofG not contained in the socleS(G). Let Φ
j
= {G|β(G) =r(G) −j}. In this paper, the family Φ11 is classified. In addition, from a simple inspection of the groups withr(G) =b conjugate classes that appear in ϒ
j
=1/11
Φ
j
, we obtain all finite groups satisfying one of the following conditions: (1)r(G) = 12; (2)r(G) = 13 andβ(G) > 1; …; (9)r(G) = 20 andβ(G) > 8; (10)r(G) =n andβ(G) =n −a with 1 ≦a ≦ 11, for each integern ≧ 21. Also, we obtain all finite groupsG with 13 ≦r(G) ≦ 20,β(G) ≦r(G) − 12, and satisfying one of the following conditions: (i) 0 ≦α(G) ≦ 4; (ii) 5 ≦α(G) ≦ 10 andS(G) solvable. 相似文献
100.
Igor Leite Freire Antonio Cândido Faleiros 《Nonlinear Analysis: Theory, Methods & Applications》2011,74(11):3478-3486
Using the classical Lie method we obtain the full Lie point symmetry group of the Aronsson equation in two independent variables. Some group invariant solutions of this equation are found and a conjecture on the Lie point symmetry group of the Aronsson equation in Rn is presented. 相似文献