全文获取类型
收费全文 | 14312篇 |
免费 | 2394篇 |
国内免费 | 1904篇 |
专业分类
化学 | 10213篇 |
晶体学 | 206篇 |
力学 | 574篇 |
综合类 | 71篇 |
数学 | 223篇 |
物理学 | 7323篇 |
出版年
2024年 | 47篇 |
2023年 | 275篇 |
2022年 | 443篇 |
2021年 | 468篇 |
2020年 | 683篇 |
2019年 | 553篇 |
2018年 | 518篇 |
2017年 | 678篇 |
2016年 | 749篇 |
2015年 | 605篇 |
2014年 | 692篇 |
2013年 | 1251篇 |
2012年 | 962篇 |
2011年 | 1009篇 |
2010年 | 858篇 |
2009年 | 893篇 |
2008年 | 906篇 |
2007年 | 897篇 |
2006年 | 801篇 |
2005年 | 708篇 |
2004年 | 656篇 |
2003年 | 532篇 |
2002年 | 573篇 |
2001年 | 441篇 |
2000年 | 384篇 |
1999年 | 288篇 |
1998年 | 246篇 |
1997年 | 210篇 |
1996年 | 205篇 |
1995年 | 155篇 |
1994年 | 160篇 |
1993年 | 116篇 |
1992年 | 116篇 |
1991年 | 76篇 |
1990年 | 67篇 |
1989年 | 60篇 |
1988年 | 48篇 |
1987年 | 35篇 |
1986年 | 39篇 |
1985年 | 38篇 |
1984年 | 38篇 |
1983年 | 16篇 |
1982年 | 32篇 |
1981年 | 20篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 13篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
921.
Remote Actuation of a Light-Emitting Device Based on Magnetic Stirring and Wireless Electrochemistry
Alice L. Dauphin Dr. Stéphane Arbault Prof. Dr. Alexander Kuhn Prof. Dr. Neso Sojic Dr. Laurent Bouffier 《Chemphyschem》2020,21(7):600-604
We propose a straightforward access to a rotating light-emitting device powered by wireless electrochemistry. A magnetic stirrer is used to rotate a light-emitting diode (LED) due to the intrinsic magnetic properties of the tips that contain iron. At the same time, the LED is submitted to an electric field and acts as a bipolar electrode. The electrochemical processes that are coupled on both extremities of the LED drive an electron flow across the device, resulting in light emission. The variation of the LED alignment in time enables an alternating light emission that is directly controlled by the rotation rate. The stirring also enables a continuous mixing of the electrolyte that improves the stability of the output signal. Finally, the LED brightness can readily reveal a change of chemical composition in the electrolyte solution. 相似文献
922.
Shengyun Huang Andrea Cel Erwin Adams Zdenk Glatz Ann Van Schepdael 《Journal of separation science》2020,43(17):3565-3572
Capillary electrophoresis is a modern separation technique characterized by many benefits, which qualify it also for enzyme assays and the study of enzyme kinetics during drug development. Homogeneous or heterogeneous approaches can be followed for the enzymatic incubation. In this study, an immobilization procedure of aldehyde oxidase on magnetic particles was developed considering their integration with capillary electrophoresis. A number of magnetic nano/microparticle types were tested for this purpose, showing that aldehyde oxidase was most active when immobilized on bare silica magnetic nanoparticles. Primarily, the reusability of the enzyme immobilized on bare silica nanoparticles was tested. Three consecutive incubations with substrate could be performed, but the activity considerably dropped after the first incubation. One reason could be an enzyme detachment from the nanoparticles, but no release was detected neither at 4°C nor at 37°C during 5 h. The drop in enzymatic activity observed in consecutive incubations, could also be due to inactivation of the enzyme over time at given temperature. For the immobilized enzyme stored at 4°C, the activity decreased to 83% after 5 h, in contrast with a steep decrease at 37°C to 37%. 相似文献
923.
Dongmei Zhang Bulei Wang Yajuan Sun Changhao Wang Somnath Mukherjee Cheng Yang Yashao Chen 《Macromolecular bioscience》2020,20(6)
Burn wound healing remains a challenging health problem worldwide due to the lack of efficient and precise therapy. Inherent oxidative stress following burn injury is importantly responsible for prolonged inflammation, fibrotic scar, and multiple organ failure. Herein, a bioinspired antioxidative defense system coupling with in situ forming hydrogel, namely, multiresponsive injectable catechol‐Fe3+ coordination hydrogel (MICH) matrix, is engineered to promote burn‐wound dermal repair by inhibiting tissue oxidative stress. This MICH matrix serves as the special traits of “Fe‐superoxide dismutases,” small molecular antioxidant (vitamin E), and extracellular matrix (ECM) in alleviating cellular oxidative damage, which demonstrates precise scavenging on reactive oxygen species (ROS) of different cellular locations, blocking lipid peroxidation and cell apoptosis. In in vivo burn‐wound treatment, this MICH promptly integrates with injured surrounding tissue to provide hydration microenvironment and physicochemical ECM for burn wounds. Importantly, the MICH matrix suppresses tissue ROS production, reducing the inflammatory response, prompting re‐epithelization and neoangiogenesis during wound healing. Meanwhile, the remodeling skin treated with MICH matrix demonstrates low collagen deposition and normal dermal collagen architecture. Overall, the MICH prevents burn wound progression and enhances skin regeneration, which might be a promising biomaterial for burn‐wound care and other disease therapy induced by oxidative stress. 相似文献
924.
925.
926.
Dr. Thomas M. Osborn Popp Ariel Z. Plantz Prof. Omar M. Yaghi Prof. Jeffrey A. Reimer 《Chemphyschem》2020,21(1):32-35
Understanding the factors that affect self-diffusion in isoreticular and multivariate (MTV) MOFs is key to their application in drug delivery, separations, and heterogeneous catalysis. Here, we measure the apparent self-diffusion of solvents saturated within the pores of large single crystals of MOF-5, IRMOF-3 (amino-functionalized MOF-5), and 17 MTV-MOF-5/IRMOF-3 materials at various mole fractions. We find that the apparent self-diffusion coefficient of N,N-dimethylformamide (DMF) may be tuned linearly between the diffusion coefficients of MOF-5 and IRMOF-3 as a function of the linker mole fraction. We compare a series of solvents at saturation in MOF-5 and IRMOF-3 to elucidate the mechanism by which the linker amino groups tune molecular diffusion. The ratio of the self-diffusion coefficients for solvents in MOF-5 to those in IRMOF-3 is similar across all solvents tested, regardless of solvent polarity. We conclude that average pore aperture, not solvent-linker chemical interactions, is the primary factor responsible for the different diffusion dynamics upon introduction of an amino group to the linker. 相似文献
927.
Nan Wen Bojun Jiang Xiaojing Wang Zhifu Shang Dawei Jiang Lu Zhang Caiying Sun Zijian Wu Hui Yan Chuntai Liu Zhanhu Guo 《Chemical record (New York, N.Y.)》2020,20(8):773-792
The properties of polyvinyl alcohol (PVA) nanocomposite hydrogels influenced by nanoparticles are reviewed. Various kinds of nanoparticles with excellent mechanical and electrical properties have been introduced into PVA hydrogel to produce stretchable and conductive PVA nanocomposite hydrogel. Understanding the mechanism between the matrix of PVA hydrogel and nanoparticles is therefore critical for the development of PVA nanocomposite hydrogels. This review focuses on the nanoparticles include carbon nanotubes, graphene oxide and metal nanoparticles, and describes the effects of nanoparticles on the mechanical and conductive properties of PVA nanocomposite hydrogels. A new promising area of soft stretchable PVA nanocomposite hydrogel is highlighted for possible applications. Finally, a brief outlook for future research is presented. 相似文献
928.
Construction of 3D tissues by various types of cells with specific characteristics is an important and fundamental technology in tissue reconstruction medicine and animal‐free diagnosis system. To do so, an excellent extracellular matrix (ECM) is needed for encapsulation of cells and maintaining cell activity. Spontaneously forming hydrogel matrix is used by complexation between two water‐soluble polymers, 2‐methacryloyloxyethyl phosphorylcholine polymer bearing phenylboronic acid groups and poly(vinyl alcohol). Two cytokines for cell proliferation are immobilized in the hydrogel matrix to control the activities of the encapsulated cells. The cytokine‐immobilized hydrogel matrix can encapsulate both L929 fibroblasts and normal human dermal fibroblasts under mild condition. The physical properties of the hydrogel matrix can follow the proliferation process of the encapsulated cells. The encapsulated cells secrete ECM in the polymer hydrogel networks upon 3D culturing for 7 days. Consequently, the tissue‐mimicking ECM hybrid hydrogels are fabricated successfully. 相似文献
929.
Xing‐Cai Huang Jia‐Xin Li Yong‐Zhi Chen Wen‐Yan Wang Rui Xu Jin‐Xia Tao Dong Shao Yi‐Quan Zhang 《化学:亚洲杂志》2020,15(9):1469-1477
Tuning the magnetic anisotropy of metal ions remains highly interesting in the design of improved single‐molecule magnets (SMMs). We herein report synthetic, structural, magnetic, and computational studies of four mononuclear CoII complexes, namely [Co(hfac)2(MeCN)2] ( 1 ), [Co(hfac)2(Spy)2] ( 2 ), [Co(hfac)2(MBIm)2] ( 3 ), and [Co(hfac)2(DMF)2] ( 4 ) (MeCN=acetonitrile, hfac=hexafluoroacetylacetone, Spy=4‐styrylpyridine, MbIm=5,6‐dimethylbenzimidazole, DMF=N,N‐dimethylformamide), with distorted octahedral geometry constructed from hexafluoroacetylacetone (hfac) and various axial ligands. By a building block approach, complexes 2 – 4 were synthesized by recrystallization of the starting material of 1 from various ligands containing solution. Magnetic and theoretical studies reveal that 1 – 4 possess large positive D values and relative small E parameters, indicating easy‐plane magnetic anisotropy with significant rhombic anisotropy in 1 – 4 . Dynamic alternative current (ac) magnetic susceptibility measurements indicate that these complexes exhibit slow magnetic relaxation under external fields, suggesting field‐induced single‐ion magnets (SIMs) of 1 – 4 . These results provide a promising platform to achieve fine tuning of magnetic anisotropy through varying the axial ligands based on Co(II) bis(hexafluoroacetylacetonate) complexes. 相似文献
930.
室温下我们研究了稀磁半导体(Ga,Mn)As的光调制反射(PR)光谱,观测到来自样品的Franz-Keldysh振荡(FKO)信号。随着Mn原子浓度的增加,PR线形展宽,但是临界点E0和E0+Δ0没有明显的移动。根据FKO振荡数据,计算得到样品表面电场强度随Mn原子掺杂浓度的增加而增强。测量到与Mn原子掺杂相关的杂质带,其能量位置离GaAs价带边~100 meV。根据样品的表面电场强度和表面耗尽层模型,估算样品的空穴浓度为~1017cm-3,较低的空穴浓度可能与样品具有较低的居里温度有关,或测量的PR信号来自于样品中外延层的部分耗尽区域。 相似文献