全文获取类型
收费全文 | 316388篇 |
免费 | 36825篇 |
国内免费 | 26924篇 |
专业分类
化学 | 157492篇 |
晶体学 | 3308篇 |
力学 | 15646篇 |
综合类 | 1420篇 |
数学 | 30721篇 |
物理学 | 93059篇 |
无线电 | 78491篇 |
出版年
2024年 | 954篇 |
2023年 | 5367篇 |
2022年 | 7719篇 |
2021年 | 10051篇 |
2020年 | 9947篇 |
2019年 | 9667篇 |
2018年 | 9175篇 |
2017年 | 9446篇 |
2016年 | 12341篇 |
2015年 | 12040篇 |
2014年 | 15307篇 |
2013年 | 19947篇 |
2012年 | 22895篇 |
2011年 | 23244篇 |
2010年 | 17784篇 |
2009年 | 17822篇 |
2008年 | 18849篇 |
2007年 | 17155篇 |
2006年 | 16008篇 |
2005年 | 14166篇 |
2004年 | 10811篇 |
2003年 | 9236篇 |
2002年 | 8861篇 |
2001年 | 7582篇 |
2000年 | 6624篇 |
1999年 | 6511篇 |
1998年 | 5644篇 |
1997年 | 4950篇 |
1996年 | 5019篇 |
1995年 | 4181篇 |
1994年 | 4001篇 |
1993年 | 3403篇 |
1992年 | 3146篇 |
1991年 | 2905篇 |
1990年 | 2476篇 |
1989年 | 2014篇 |
1988年 | 1698篇 |
1987年 | 1550篇 |
1986年 | 1485篇 |
1985年 | 1448篇 |
1984年 | 1297篇 |
1983年 | 1121篇 |
1982年 | 1041篇 |
1981年 | 881篇 |
1979年 | 885篇 |
1977年 | 880篇 |
1976年 | 985篇 |
1975年 | 877篇 |
1974年 | 908篇 |
1973年 | 899篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
A nanomaterials-based novel molecular beacon has attracted growing attentions in fluorescent assays as many nanomaterials possess excellent quenching efficiency. In this work, a gold-based nanobeacon probe was established to detect organophosphorus pesticides for the first time. The constructed gold-based nanobeacon acted as a signal indicator and could display the decreasing of the intensity in the presence of targets, which competitively bound to single strand DNA. To achieve a high sensitive probe, some parameters including solution pH, temperature and reaction time were investigated and optimized. The gold-based nanobeacon probe assay was proved to be rapid and sensitive to achieve a detection limit of 0.035 μM for isocarbophos, 0.134 μM for profenofos, 0.384 μM for phorate and 2.35 μM for omethoate, respectively. The prepared nanobeacon effectively reduced the background and improved the detection sensitivity and selectivity. The probe is stable, easy to operate and does not need sophisticated instruments. These features makes the probe feasible for screening trace organophosphorus pesticides in real samples. 相似文献
42.
Inside Cover: Photoinduced Formation of an Azobenzene‐Based CD‐Active Supramolecular Cyclic Dimer (Chem. Eur. J. 18/2015) 下载免费PDF全文
43.
44.
45.
就标准厚度卡片在霍尔传感器的定标方面的应用作了有益的探讨。在纵向测量微小长度时,霍尔片处于磁场边缘位置,其对磁场的梯度更大,即灵敏度更高,且靠中心位置的线性更好。 相似文献
46.
S. Q. Hou W. Wang Z. Y. Wang Z. W. Hu K. Liu 《Journal of Applied Mechanics and Technical Physics》2018,59(1):153-162
In order to investigate the characteristics of force chains in a granular flow system, a parallel plate shear cell is constructed to simulate the shear movement of an infinite parallel plate and observe variations in relevant parameters. The shear dilatancy process is divided into three stages, namely, plastic strain, macroscopic failure, and granular recombination. The stickslip phenomenon is highly connected with the evolution of force chains during the shear dilatancy process. The load–distribution rate curves and patterns of the force chains are utilized to describe the load-carrying behaviors and morphologic changes of force chains separately. Force chains, namely, “diagonal gridding,” “tadpole-shaped,” and “pinnate” are defined according to the form of the force chains in the corresponding three stages. 相似文献
47.
48.
Polypyrrole Shell@3D‐Ni Metal Core Structured Electrodes for High‐Performance Supercapacitors 下载免费PDF全文
Gao‐Feng Chen Yu‐Zhi Su Pan‐Yong Kuang Zhao‐Qing Liu Dao‐Yi Chen Xu Wu Nan Li Prof. Shi‐Zhang Qiao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(12):4614-4621
Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g?1 at a charge/discharge rate of 1 A g?1), good rate capability (a decay of 33 % in Csp with charge/discharge rates increasing from 1 to 20 A g?1), and high cycle stability (only a small decrease of 4.2 % in Csp after 1000 cycles at a scan rate of 100 mV s?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in Csp after 2000 and 5000 cycles, respectively). 相似文献
49.
50.