全文获取类型
收费全文 | 1660篇 |
免费 | 280篇 |
国内免费 | 175篇 |
专业分类
化学 | 1165篇 |
晶体学 | 18篇 |
力学 | 91篇 |
综合类 | 10篇 |
数学 | 147篇 |
物理学 | 684篇 |
出版年
2024年 | 2篇 |
2023年 | 45篇 |
2022年 | 37篇 |
2021年 | 55篇 |
2020年 | 91篇 |
2019年 | 78篇 |
2018年 | 50篇 |
2017年 | 47篇 |
2016年 | 73篇 |
2015年 | 79篇 |
2014年 | 68篇 |
2013年 | 95篇 |
2012年 | 115篇 |
2011年 | 143篇 |
2010年 | 111篇 |
2009年 | 117篇 |
2008年 | 123篇 |
2007年 | 104篇 |
2006年 | 109篇 |
2005年 | 92篇 |
2004年 | 57篇 |
2003年 | 47篇 |
2002年 | 42篇 |
2001年 | 50篇 |
2000年 | 37篇 |
1999年 | 42篇 |
1998年 | 29篇 |
1997年 | 25篇 |
1996年 | 33篇 |
1995年 | 21篇 |
1994年 | 29篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 3篇 |
1982年 | 1篇 |
排序方式: 共有2115条查询结果,搜索用时 15 毫秒
131.
Sensitivity analysis of linear vibration system is of wide interest. In this paper, sensitivity analysis based on non-defective system and defective system is summarized in all cases. Specially, for the defective systems, a fast method for the perturbation problem of state vectors is constructed in terms of the theories of generalized eigenvectors and adjoint matrices. By this method, the state vector derivatives can be expressed by a linear combination of generalized eigenvectors. The expansion coefficients can be obtained without solving large-scale equations based on eigensolutions of original system. Numerical results demonstrate the effectiveness and the stability of the method. 相似文献
132.
133.
134.
135.
Zheng Wu WANG Gan Zuo LI* Da Ren GUAN Xi Zhang YI An Jing LOU Key Lab of Colloid Interface Chemistry for State Education Ministry Shandong University Ji''''nan Institute of Theoretical Chemistry Shandong University Ji''''n 《中国化学快报》2001,(7)
The electrical double layer theory is the base of the colloid stability theory (DLVO theory), and the PB eq. is a key to the study of the layer1,2. For a spherical particle, the PB eq. is (1) where and are the dielectric constant of the medium, the valence of ions, the elementary charge, the concentration of ions far away from the particle, the Boltzmann's constant and the temperature of the system, respectively. Since this eq. is a second order nonlinear differential one, only the anal… 相似文献
136.
137.
用红外光谱法测试研究了餐盒用新型非发泡聚丙烯光降解行为。结果表明,降解母粒含量不同,其红外吸收光谱图存在明显的差异;在光降解过程中,羰基指数存在明显的动态变化。 相似文献
138.
络合滴定法测定低压流体输送用镀锌焊接钢管镀锌层重量 总被引:2,自引:0,他引:2
介绍了利用络合滴定法测定低压流体输送用镀锌焊风管镀锌层重量的方法,试样用稀硫酸溶解,在PH1.5 ̄2.0的弱酸性介质中,以磺基水杨酸钠为指标剂,用EDTA滴定铁,调PH为5.5,以PAN为指示剂,用EDTA滴定锌,由EDTA用量求出锌的重量,用GB/T3091-93方法比较,试验结果满意。 相似文献
139.
Acid‐treated g‐C3N4‐Cu2O composite catalyst with enhanced photocatalytic activity under visible‐light irradiation
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Shiyu Zuo Haiming Xu Wei Liao Lei Sun Donghui Han Jie Zan Binyang Zhang Dongya Li Dongsheng Xia 《应用有机金属化学》2018,32(9)
Acid‐treated g‐C3N4‐Cu2O was prepared by hydrothermal reduction followed by high temperature calcination and acid exfoliation. The structures and properties of as‐synthesized samples were characterized using a range of techniques, such as X‐ray photoelectron spectroscopy, scanning electron microscopy, Photoluminescence Spectroscopy and the Brunauer–Emmett–Teller (BET) theory. The photocatalytic activity was evaluated by measuring the photodegradation of methyl orange under visible‐light irradiation. Based on the results of TEM, XPS, EPR and other techniques, it was verified that a heterojunction was formed. The acid treatment process can increase the specific surface area to form abundant heterojunction interfaces as channels for photo‐generated carrier separation, thereby enhancing its light utilization and quantum efficiency. Results indicate that acid‐treated g‐C3N4‐Cu2O possesses a large specific surface area, which provides plentiful activated sites for heterojunctions to form; in addition, it showed a high visible light effect and the minimum charge‐transfer resistance. Furthermore, the g‐C3N4‐Cu2O material exhibits high levels of effectiveness and stability. Electron paramagnetic resonance and a series of radical trapping experiments demonstrate that the holes and ?O2? could be the main active species in methyl orange photodegradation. This work could provide new insights into the fabrication of composite materials as high‐performance photocatalysts, and facilitate their application in addressing environmental protection issues. 相似文献
140.
Huixia Hu Yonggang Shangguan Min Zuo Qiang Zheng 《Journal of Polymer Science.Polymer Physics》2008,46(18):1923-1931
The liquid–liquid phase‐separation (LLPS) behavior of poly(n‐methyl methacrylimide)/poly(vinylidene fluoride) (PMMI/PVDF) blend was studied by using small‐angle laser light scattering (SALLS) and phase contrast microscopy (PCM). The cloud point (Tc) of PMMI/PVDF blend was obtained using SALLS at the heating rate of 1 °C min?1 and it was found that PMMI/PVDF exhibited a low critical solution temperature (LCST) behavior similar to that of PMMA/PVDF. Moreover, Tc of PMMI/PVDF is higher than its melting temperature (Tm) and a large temperature gap between Tc and Tm exists. At the early phase‐separation stage, the apparent diffusion coefficient (Dapp) and the product (2Mk) of the molecules mobility coefficient (M) and the energy gradient coefficient (k) arising from contributions of composition gradient to the energy for PMMI/PVDF (50/50 wt) blend were calculated on the basis of linearized Cahn‐Hilliard‐Cook theory. The kinetic results showed that LLPS of PMMI/PVDF blends followed the spinodal decomposition (SD) mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1923–1931, 2008 相似文献