全文获取类型
收费全文 | 29531篇 |
免费 | 5642篇 |
国内免费 | 3191篇 |
专业分类
化学 | 21149篇 |
晶体学 | 321篇 |
力学 | 1766篇 |
综合类 | 136篇 |
数学 | 2981篇 |
物理学 | 12011篇 |
出版年
2024年 | 47篇 |
2023年 | 666篇 |
2022年 | 738篇 |
2021年 | 1059篇 |
2020年 | 1376篇 |
2019年 | 1344篇 |
2018年 | 1130篇 |
2017年 | 997篇 |
2016年 | 1555篇 |
2015年 | 1437篇 |
2014年 | 1875篇 |
2013年 | 2307篇 |
2012年 | 2810篇 |
2011年 | 2868篇 |
2010年 | 1869篇 |
2009年 | 1780篇 |
2008年 | 1994篇 |
2007年 | 1737篇 |
2006年 | 1626篇 |
2005年 | 1280篇 |
2004年 | 969篇 |
2003年 | 747篇 |
2002年 | 713篇 |
2001年 | 563篇 |
2000年 | 448篇 |
1999年 | 580篇 |
1998年 | 503篇 |
1997年 | 488篇 |
1996年 | 480篇 |
1995年 | 420篇 |
1994年 | 342篇 |
1993年 | 275篇 |
1992年 | 276篇 |
1991年 | 223篇 |
1990年 | 200篇 |
1989年 | 151篇 |
1988年 | 92篇 |
1987年 | 79篇 |
1986年 | 103篇 |
1985年 | 73篇 |
1984年 | 37篇 |
1983年 | 43篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 7篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1957年 | 4篇 |
1923年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
83.
84.
85.
Xi‐Sha Zhang Yun‐Fei Zhang Zhao‐Wei Li Fei‐Xian Luo Zhang‐Jie Shi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(18):5568-5572
A rhodium(III)‐catalyzed cross‐coupling of benzyl thioethers and aryl carboxylic acids through the two directing groups is reported. Useful structures with diverse substituents were efficiently synthesized in one step with the cleavage of four bonds (C H, C S, O H) and the formation of two bonds (C C, C O). The formed structure is the privileged core in natural products and bioactive molecules. This work highlights the power of using two different directing groups to enhance the selectivity of a double C H activation, the first of such examples in cross‐oxidative coupling. 相似文献
86.
Erqiang Liu Jianguo Wu Huaying Li Haitao Liu Guanghui Zhao Lingyu Kong Jinbao Lin Gesheng Xiao You Jia 《Journal of polymer science. Part A, Polymer chemistry》2021,59(5):451-461
Instrumented indentation tests using both constant loading rate (CLR) and continuous stiffness measurement (CSM) operation modes were performed to investigate the deformation mechanism and their sensitivity to the deformation rate in semi-crystalline polymers through the quantitative analysis of load-depth loading and unloading curves. The strain rate was constant during the CSM tests, while the strain rate decreased with the increasing of loading time in CLR tests. The mechanical response mechanism of the semi-crystalline polymers to these tests was very complicated because of the combined effects of strain-hardening in the crystal phase and strain-softening in the amorphous phase. Results show that the loading index m reflects the strain-hardening or strain-softening response during indentation. When m > 2, the mechanical response was due to the strain-hardening, and when m < 2, the response was due to strain-softening. A method based on the measured contact hardness was proposed to obtain the unloading stiffness, and the other mechanical parameters could then be determined according to the unloading stiffness. 相似文献
87.
88.
Injectable hydrogels for nonsteroidal anti‐inflammatory drugs’ (NSAIDs) delivery to minimize the side effects of NSAIDs and achieve long‐term sustained release at the targeted site of synovial joint are attractive for osteoarthritis therapy, but how to improve its mechanical strength remains a challenge. In this work, a kind of 1D natural clay mineral material, attapulgite (ATP), is introduced to a classical cyclodextrin pseudopolyrotaxane (PPR) system to form a reinforced supramolecular hydrogel for sustained release of diclofenac sodium (DS) due to its rigid, rod‐like morphology, and unique structure, which has great potential in tissue regeneration, repair, and engineering. Investigation on the interior morphology and rheological property of the obtained hydrogel points out that the ATP distributed in PPR hydrogel plays a role similar to the “reinforcement in concrete” and exhibits a positive effect on improving the mechanical properties of PPR hydrogel by regulating their interior morphology from a randomly distributed style to the well‐ordered porous frame structure. The hybrid hydrogels demonstrate good shear‐thinning and thixotropic properties, excellent biocompability, and sustained release behavior both in vitro and in vivo. Furthermore, preliminary in vivo treatment in an acute inflammatory rat model reveals that the ATP hybrid hydrogels present sustained anti‐inflammatory effect. 相似文献
89.
Yu Wang Xin-jing Zhao Rong-Jing Wei Gui-jie Liang Kang Wang Yuan-zhi Tan Ye Yang 《化学物理学报(中文版)》2021,34(5):591-597
The intermolecular interaction determines the photophysical properties of the organic aggregates, which are critical to the performance of organic photovoltaics. Here, excitonic coupling, an important intermolecular interaction in organic aggregates, between the π-stacking graphene quantum dots is studied by using transient absorption spectroscopy. We find that the spectral evolution of the ground state bleach arises from the dynamic variation of the excitonic coupling in the excited π-stacks. According to the spectral simulations, we demonstrate that the kinetics of the vibronic peak can be exploited as a probe to measure the dynamics of excitonic coupling in the excited π-stacks. 相似文献
90.
Shehzad Hamza Zhou Limin Wang Yun Ouyang Jinbo Huang Guolin Liu Zhirong Li Zhao 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(2):605-611
Journal of Radioanalytical and Nuclear Chemistry - The kinetics of Co ions sorption on CoTreat® was investigated in the 5–40 mg/L concentration range at a bulk temperature of... 相似文献