全文获取类型
收费全文 | 85189篇 |
免费 | 662篇 |
国内免费 | 432篇 |
专业分类
化学 | 29401篇 |
晶体学 | 833篇 |
力学 | 6875篇 |
数学 | 33058篇 |
物理学 | 16116篇 |
出版年
2023年 | 41篇 |
2022年 | 142篇 |
2021年 | 215篇 |
2020年 | 155篇 |
2019年 | 192篇 |
2018年 | 10495篇 |
2017年 | 10331篇 |
2016年 | 6317篇 |
2015年 | 1067篇 |
2014年 | 557篇 |
2013年 | 709篇 |
2012年 | 4309篇 |
2011年 | 11026篇 |
2010年 | 5970篇 |
2009年 | 6321篇 |
2008年 | 7084篇 |
2007年 | 9193篇 |
2006年 | 668篇 |
2005年 | 1747篇 |
2004年 | 1887篇 |
2003年 | 2223篇 |
2002年 | 1256篇 |
2001年 | 377篇 |
2000年 | 389篇 |
1999年 | 241篇 |
1998年 | 261篇 |
1997年 | 220篇 |
1996年 | 294篇 |
1995年 | 185篇 |
1994年 | 135篇 |
1993年 | 143篇 |
1992年 | 98篇 |
1991年 | 120篇 |
1990年 | 94篇 |
1989年 | 91篇 |
1988年 | 89篇 |
1987年 | 86篇 |
1986年 | 90篇 |
1985年 | 91篇 |
1984年 | 82篇 |
1983年 | 62篇 |
1982年 | 78篇 |
1981年 | 56篇 |
1980年 | 57篇 |
1979年 | 51篇 |
1978年 | 47篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
23.
24.
25.
Highly Selective Copper‐Catalyzed Asymmetric [3+2] Cycloaddition of Azomethine Ylides with Acyclic 1,3‐Dienes 下载免费PDF全文
María González‐Esguevillas Ana Pascual‐Escudero Dr. Javier Adrio Prof. Dr. Juan C. Carretero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4561-4565
The first examples of the catalytic asymmetric 1,3‐dipolar cycloaddition of azomethine ylides with acyclic activated 1,3‐dienes (and 1,3‐enynes) are described. Under copper catalysis, a selective cycloaddition at the terminal γ,δ‐C?C bond is observed. In addition, depending on the ligand used, either the exo or the endo adduct can be obtained with high selectivity. Under appropriate reaction conditions, the acyclic 1,6‐addition product is detected, suggesting a stepwise mechanism. The resulting C4‐alkenyl‐substituted pyrrolidines are suitable substrates for further access to polycyclic systems, as highlighted by the preparation of hexahydrochromeno[4,3‐b]pyrrole and the tetracyclic core of the alkaloid gracilamine. 相似文献
26.
27.
Brandão Pedro Francisco Ramos Rui Miguel Rodrigues José António 《Analytical and bioanalytical chemistry》2018,410(26):6873-6880
Analytical and Bioanalytical Chemistry - Formaldehyde is often applied in the industrial production of different products, such as textiles, insulation materials, or cosmetics, due to its... 相似文献
28.
29.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
30.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective. 相似文献