全文获取类型
收费全文 | 44313篇 |
免费 | 7812篇 |
国内免费 | 5323篇 |
专业分类
化学 | 31132篇 |
晶体学 | 448篇 |
力学 | 3168篇 |
综合类 | 387篇 |
数学 | 5004篇 |
物理学 | 17309篇 |
出版年
2024年 | 146篇 |
2023年 | 872篇 |
2022年 | 1516篇 |
2021年 | 1582篇 |
2020年 | 1813篇 |
2019年 | 1645篇 |
2018年 | 1454篇 |
2017年 | 1295篇 |
2016年 | 2045篇 |
2015年 | 2106篇 |
2014年 | 2479篇 |
2013年 | 3165篇 |
2012年 | 3935篇 |
2011年 | 4169篇 |
2010年 | 2722篇 |
2009年 | 2535篇 |
2008年 | 2778篇 |
2007年 | 2499篇 |
2006年 | 2515篇 |
2005年 | 2026篇 |
2004年 | 1713篇 |
2003年 | 1309篇 |
2002年 | 1306篇 |
2001年 | 1065篇 |
2000年 | 961篇 |
1999年 | 998篇 |
1998年 | 804篇 |
1997年 | 739篇 |
1996年 | 779篇 |
1995年 | 704篇 |
1994年 | 650篇 |
1993年 | 523篇 |
1992年 | 493篇 |
1991年 | 415篇 |
1990年 | 357篇 |
1989年 | 292篇 |
1988年 | 228篇 |
1987年 | 185篇 |
1986年 | 144篇 |
1985年 | 140篇 |
1984年 | 83篇 |
1983年 | 76篇 |
1982年 | 52篇 |
1981年 | 46篇 |
1980年 | 23篇 |
1979年 | 11篇 |
1977年 | 5篇 |
1975年 | 6篇 |
1969年 | 4篇 |
1957年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
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
22.
Simultaneous quantitative determination of 20 active components in the traditional Chinese medicine formula Zhi‐Zi‐Da‐Huang decoction by liquid chromatography coupled with mass spectrometry: application to study the chemical composition variations in different combinations 下载免费PDF全文
Zheng Tang Ran Yin Kaishun Bi Heyun Zhu Fei Han Kelin Chen Fenrong Wang 《Biomedical chromatography : BMC》2015,29(9):1406-1414
23.
24.
Zhang Jia-Rui Zhang Jia-Qi Zheng Zhao-Lin Lin Da Shen Yu-Jia 《Nonlinear dynamics》2022,108(2):1005-1026
Nonlinear Dynamics - Parametrically excited oscillators are used in several domains, in particular to improve the dynamical behaviour of systems like in the case of the parametric amplification or... 相似文献
25.
26.
27.
28.
Ionics - This study aims to explore the potential merits of palladium oxide sensing electrode. PdO is applied on a solid-state potentiometric sensor on an yttria-stabilized zirconia (YSZ)... 相似文献
29.
Xiaoshuang Luo Xinxian Qin Zhengyi Liu Dan Chen Weiwei Yu Kankan Zhang Deyu Hu 《Biomedical chromatography : BMC》2020,34(1):e4694
A simple and rapid analytical method for the detection of trifloxystrobin, trifloxystrobin acid and tebuconazole in soil, brown rice, paddy plants and rice hulls was established and validated by liquid chromatography with tandem mass spectrometry. Acceptable linearity (R2 > 0.99), accuracy (average recoveries of 74.3–108.5%) and precision (intra- and inter-day relative standard deviations of 0.9–8.8%) were obtained using the developed determination approach. In the field trial, the half-lives of trifloxystrobin and tebuconazole in paddy plants were 5.7–8.3 days in three locations throughout China, and the terminal residue concentrations of trifloxystrobin and tebuconazole were <100 and 500 μg/kg (maximum residue limits set by China), respectively, at harvest, which indicated that, based on the recommended application procedure, trifloxystrobin and tebuconazole are safe for use on rice. The risk assessment results demonstrated that, owing to risk quotient values of both fungicides being <100%, the potential risk of trifloxystrobin and tebuconazole on rice was acceptable for Chinese consumers. These data could provide supporting information for the proper use and safety evaluation of trifloxystrobin and tebuconazole in rice. 相似文献
30.
Liming Fan Feng Wang Dongsheng Zhao Yuxin Peng Yuxin Deng Yinwei Luo Xiutang Zhang 《应用有机金属化学》2020,34(12):e5960
Guided by the self-penetrating features can improve the stability of metal organic frameworks (MOFs), an unprecedented 3D self-penetrated framework, {[Zn (tptc)0.5(bimb)]·H2O}n ( NUC-6 , here NUC corresponding to North University of China), with 3D (4,4)-c {86} net, was designed. Benefit from the high chemical stability and excellent luminescent property, NUC-6 can be act as an efficient multi-response chemo-sensor in detecting dichloronitroaniline pesticide and nitrofuran antibiotics in water with the detection limits are 116 ppb for DCN pesticide, 16 ppb for NFT antibiotic, and 12 ppb for NTZ antibiotic. Besides, the mechanisms of luminescence quenching were revealed from the viewpoint of internal filter effect (IFE) and photo-induced electron transfer (PET), implied by the optical spectroscopy and quantum chemical calculation. This work provides a promising strategy to design stable MOFs by improving the self-penetrating features and to expand their practical applications in the detection of organic pollutants in aqueous medium. 相似文献