全文获取类型
收费全文 | 22957篇 |
免费 | 4131篇 |
国内免费 | 4301篇 |
专业分类
化学 | 11785篇 |
晶体学 | 318篇 |
力学 | 845篇 |
综合类 | 336篇 |
数学 | 1923篇 |
物理学 | 6018篇 |
无线电 | 10164篇 |
出版年
2024年 | 72篇 |
2023年 | 341篇 |
2022年 | 620篇 |
2021年 | 686篇 |
2020年 | 730篇 |
2019年 | 748篇 |
2018年 | 645篇 |
2017年 | 738篇 |
2016年 | 906篇 |
2015年 | 1097篇 |
2014年 | 1341篇 |
2013年 | 1615篇 |
2012年 | 1860篇 |
2011年 | 1996篇 |
2010年 | 1756篇 |
2009年 | 1847篇 |
2008年 | 2004篇 |
2007年 | 1924篇 |
2006年 | 1827篇 |
2005年 | 1469篇 |
2004年 | 1172篇 |
2003年 | 943篇 |
2002年 | 1078篇 |
2001年 | 925篇 |
2000年 | 784篇 |
1999年 | 452篇 |
1998年 | 275篇 |
1997年 | 220篇 |
1996年 | 220篇 |
1995年 | 177篇 |
1994年 | 162篇 |
1993年 | 146篇 |
1992年 | 107篇 |
1991年 | 84篇 |
1990年 | 72篇 |
1989年 | 54篇 |
1988年 | 50篇 |
1987年 | 49篇 |
1986年 | 36篇 |
1985年 | 27篇 |
1984年 | 27篇 |
1983年 | 27篇 |
1982年 | 12篇 |
1981年 | 14篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1965年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
1.
恶意代码数量已经呈现爆炸式增长,对于恶意代码的检测防护显得尤为重要.近几年,基于深度学习的恶意代码检测方法开始出现,基于此,提出一种新的检测方法,将恶意代码二进制文件转化为十进制数组,并利用一维卷积神经网络(1 Dimention Convolutional Neural Networks,1D CNN)对数组进行分类和识别.针对代码家族之间数量不平衡的现象,该算法选择在分类预测上表现良好的XGBoost,并对Vision Research Lab中的25个不同恶意软件家族的9458个恶意软件样本进行了实验.实验结果表明,所提的方法分类预测精度达到了97%. 相似文献
2.
3.
Shuhai Liu Ming Han Xiaolong Feng Qiuhong Yu Long Gu Longfei Wang Yong Qin Zhong Lin Wang 《Advanced functional materials》2021,31(17):2010339
Utilizing inner-crystal piezoelectric polarization charges to control carrier transport across a metal-semiconductor or semiconductor–semiconductor interface, piezotronic effect has great potential applications in smart micro/nano-electromechanical system (MEMS/NEMS), human-machine interfacing, and nanorobotics. However, current research on piezotronics has mainly focused on systems with only one or rather limited interfaces. Here, the statistical piezotronic effect is reported in ZnO bulk composited of nanoplatelets, of which the strain/stress-induced piezo-potential at the crystals’ interfaces can effectively gate the electrical transport of ZnO bulk. It is a statistical phenomenon of piezotronic modification of large numbers of interfaces, and the crystal orientation of inner ZnO nanoplatelets strongly influence the transport property of ZnO bulk. With optimum preferred orientation of ZnO nanoplatelets, the bulk exhibits an increased conductivity with decreasing stress at a high pressure range of 200–400 MPa, which has not been observed previously in bulk. A maximum sensitivity of 1.149 µS m−1 MPa−1 and a corresponding gauge factor of 467–589 have been achieved. As a statistical phenomenon of many piezotronic interfaces modulation, the proposed statistical piezotronic effect extends the connotation of piezotronics and promotes its practical applications in intelligent sensing. 相似文献
4.
Liu Jun-Wei Shen Shu-Qian Li Ming Li Lei 《International Journal of Theoretical Physics》2021,60(5):1712-1719
International Journal of Theoretical Physics - Quantum coherence, coming from quantum superposition, occupies a significant position in the field of physics. We put forward a lower bound of the... 相似文献
5.
6.
Wireless Personal Communications - The purpose of this study is to construct a structural equation model of shared bicycle added psychological factors proceeding from the theory of planned... 相似文献
7.
9.
Metabolic profiles of dioscin in rats revealed by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
He Zhu Jin‐Di Xu Qian Mao Hong Shen Ming Kong Jian‐Ping Chen Song‐Lin Li 《Biomedical chromatography : BMC》2015,29(9):1415-1421
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
10.