全文获取类型
收费全文 | 87177篇 |
免费 | 827篇 |
国内免费 | 503篇 |
专业分类
化学 | 30838篇 |
晶体学 | 859篇 |
力学 | 7134篇 |
综合类 | 3篇 |
数学 | 33052篇 |
物理学 | 16621篇 |
出版年
2023年 | 93篇 |
2022年 | 473篇 |
2021年 | 433篇 |
2020年 | 359篇 |
2019年 | 447篇 |
2018年 | 10692篇 |
2017年 | 10446篇 |
2016年 | 6560篇 |
2015年 | 1242篇 |
2014年 | 851篇 |
2013年 | 1363篇 |
2012年 | 4512篇 |
2011年 | 11148篇 |
2010年 | 6126篇 |
2009年 | 6438篇 |
2008年 | 7011篇 |
2007年 | 9127篇 |
2006年 | 509篇 |
2005年 | 1589篇 |
2004年 | 1695篇 |
2003年 | 2141篇 |
2002年 | 1153篇 |
2001年 | 322篇 |
2000年 | 340篇 |
1999年 | 213篇 |
1998年 | 229篇 |
1997年 | 194篇 |
1996年 | 241篇 |
1995年 | 148篇 |
1994年 | 113篇 |
1993年 | 112篇 |
1992年 | 88篇 |
1991年 | 95篇 |
1990年 | 79篇 |
1989年 | 94篇 |
1988年 | 91篇 |
1987年 | 91篇 |
1986年 | 87篇 |
1985年 | 83篇 |
1984年 | 77篇 |
1983年 | 57篇 |
1982年 | 69篇 |
1981年 | 57篇 |
1980年 | 69篇 |
1979年 | 64篇 |
1978年 | 52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 156 毫秒
21.
Kai He Tsegaye TadesseTsega Xi Liu Jiantao Zai Xin‐Hao Li Xuejiao Liu Wenhao Li Nazakat Ali Xuefeng Qian 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(34):12029-12035
The modulation of electron density is an effective option for efficient alternative electrocatalysts. Here, p‐n junctions are constructed in 3D free‐standing FeNi‐LDH/CoP/carbon cloth (CC) electrode (LDH=layered double hydroxide). The positively charged FeNi‐LDH in the space‐charge region can significantly boost oxygen evolution reaction. Therefore, the j at 1.485 V (vs. RHE) of FeNi‐LDH/CoP/CC achieves ca. 10‐fold and ca. 100‐fold increases compared to those of FeNi‐LDH/CC and CoP/CC, respectively. Density functional theory calculation reveals OH? has a stronger trend to adsorb on the surface of FeNi‐LDH side in the p‐n junction compared to individual FeNi‐LDH further verifying the synergistic effect in the p‐n junction. Additionally, it represents excellent activity toward water splitting. The utilization of heterojunctions would open up an entirely new possibility to purposefully regulate the electronic structure of active sites and promote their catalytic activities. 相似文献
22.
23.
24.
25.
26.
27.
28.
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
29.
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
30.
Chee Sing Yap 《The Journal of the Operational Research Society》1989,40(7):649-658
This paper describes three case studies which investigated issues relating to the implementation and management of advanced information technology. The benefits derived from information technology were found to vary from one organization to another. These studies provide further evidence to support earlier research findings that senior management has an important role to play in the effective exploitation of information technology, and that the investment approach taken by an organization has a significant effect on the development of computer-based information systems. The effectiveness of a system depends not only on applying the appropriate technology, but also on how successfully technical and behavioural issues are resolved. 相似文献