全文获取类型
收费全文 | 82990篇 |
免费 | 517篇 |
国内免费 | 404篇 |
专业分类
化学 | 28198篇 |
晶体学 | 836篇 |
力学 | 6784篇 |
数学 | 32218篇 |
物理学 | 15875篇 |
出版年
2021年 | 56篇 |
2020年 | 65篇 |
2019年 | 95篇 |
2018年 | 10470篇 |
2017年 | 10287篇 |
2016年 | 6149篇 |
2015年 | 929篇 |
2014年 | 413篇 |
2013年 | 578篇 |
2012年 | 4059篇 |
2011年 | 10833篇 |
2010年 | 5806篇 |
2009年 | 6255篇 |
2008年 | 6924篇 |
2007年 | 9078篇 |
2006年 | 611篇 |
2005年 | 1637篇 |
2004年 | 1841篇 |
2003年 | 2219篇 |
2002年 | 1266篇 |
2001年 | 321篇 |
2000年 | 347篇 |
1999年 | 207篇 |
1998年 | 258篇 |
1997年 | 210篇 |
1996年 | 260篇 |
1995年 | 168篇 |
1994年 | 109篇 |
1993年 | 134篇 |
1992年 | 81篇 |
1991年 | 98篇 |
1990年 | 67篇 |
1989年 | 77篇 |
1988年 | 84篇 |
1987年 | 87篇 |
1986年 | 102篇 |
1985年 | 104篇 |
1984年 | 89篇 |
1983年 | 59篇 |
1982年 | 93篇 |
1981年 | 91篇 |
1980年 | 90篇 |
1979年 | 82篇 |
1978年 | 63篇 |
1977年 | 44篇 |
1973年 | 43篇 |
1914年 | 45篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
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
14.
15.
16.
17.
Minoru Koyama Dr. Takafumi Kawakami Dr. Takashi Okazoe Prof. Dr. Kyoko Nozaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10913-10917
Methacrylic esters, represented by methyl methacrylate (MMA), are widely used as commodity chemicals. Here, the one-pot synthesis of methacrylic esters from acetone, a haloform and alcohols in the presence of an organic base is described. Using DBU as the organic base for the reaction of acetone, chloroform and methanol in acetonitrile afforded MMA in 66 % yield. When the solvent was replaced by benzonitrile, the product MMA was successfully purified by distillation. Applicability of this process to various alcohols was also investigated to show ethyl, phenyl, CF3CH2, and n-C6F13CH2CH2 esters were obtained in moderate yields. The use of bromoform instead of chloroform resulted in the improvement of the yield, for example, methyl and n-C6F13CH2CH2 esters up to 81 and 70 %, respectively. The reaction with deuterated starting materials acetone-d6 and MeOH-d4, with DBU in acetonitrile afforded deuterated MMA (MMA-d8) in 70 % yield. 相似文献
18.
19.
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
20.
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