全文获取类型
收费全文 | 399064篇 |
免费 | 26667篇 |
国内免费 | 18095篇 |
专业分类
化学 | 216160篇 |
晶体学 | 6447篇 |
力学 | 19669篇 |
综合类 | 26篇 |
数学 | 45618篇 |
物理学 | 155906篇 |
出版年
2020年 | 3151篇 |
2019年 | 3902篇 |
2018年 | 4550篇 |
2017年 | 5087篇 |
2016年 | 7038篇 |
2015年 | 5512篇 |
2014年 | 7177篇 |
2013年 | 17998篇 |
2012年 | 14282篇 |
2011年 | 18301篇 |
2010年 | 16855篇 |
2009年 | 16828篇 |
2008年 | 14965篇 |
2007年 | 14494篇 |
2006年 | 13832篇 |
2005年 | 13233篇 |
2004年 | 13156篇 |
2003年 | 11464篇 |
2002年 | 11154篇 |
2001年 | 12609篇 |
2000年 | 9575篇 |
1999年 | 8250篇 |
1998年 | 7009篇 |
1997年 | 6712篇 |
1996年 | 6809篇 |
1995年 | 6836篇 |
1994年 | 6717篇 |
1993年 | 6717篇 |
1992年 | 6658篇 |
1991年 | 6473篇 |
1990年 | 5925篇 |
1989年 | 5999篇 |
1988年 | 5982篇 |
1987年 | 5309篇 |
1986年 | 5076篇 |
1985年 | 6304篇 |
1984年 | 6667篇 |
1983年 | 5126篇 |
1982年 | 5966篇 |
1981年 | 5610篇 |
1980年 | 5607篇 |
1979年 | 5503篇 |
1978年 | 5697篇 |
1977年 | 5610篇 |
1976年 | 6024篇 |
1975年 | 5023篇 |
1974年 | 4897篇 |
1973年 | 5329篇 |
1972年 | 3765篇 |
1971年 | 3026篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Kinetics and Catalysis - A series of Cu-SSZ-13@CeO2 catalysts with surface modification with CeO2 was prepared by the modified self-resemble method based on the one-pot synthesized Cu-SSZ-13... 相似文献
102.
Gelikonov G. V. Ksenofontov S. Yu. Shilyagin P. A. Gelikonov V. M. 《Radiophysics and Quantum Electronics》2019,62(3):228-236
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in... 相似文献
103.
A.G. Rousskikh A.V. Fedyunin A.P. Artyomov A.S. Zhigalin V.I. Oreshkin 《Current Applied Physics》2019,19(6):704-708
The aim of the study presented in this paper was to characterize quantitatively the erosion of aluminum cathodes in high-current vacuum arcs. The experimental setup comprised two current generators. The first one, capable of generating a current of amplitude up to 350 kA, was used to produce a plasma jet, that is, the object to be investigated. The second generator was used to produce a source of probe radiation for imaging the object under investigation in soft x rays of energy ?ν ≈ 0.5–3 keV. The findings of the study are based on experimental data obtained by electrophysical and radiographic methods. It has been shown that the cathode erosion rate in a high-current vacuum arc is a function of the charge passed through the cathode. 相似文献
104.
105.
106.
107.
Savita Verma Deepak M. Maher Samadhan S. Nagane Bhausaheb V. Tawade Prakash P. Wadgaonkar 《Journal of polymer science. Part A, Polymer chemistry》2019,57(5):588-597
New aromatic (co)polyesters containing pendant propargyloxy groups were synthesized by phase transfer‐catalyzed interfacial polycondensation of 5‐(propargyloxy)isophthaloyl chloride (P‐IPC) and various compositions of P‐IPC and isophthaloyl chloride with bisphenol A. FTIR and NMR spectroscopic data, respectively, revealed successful incorporation of pendant propargyloxy groups into (co)polyesters and formation of (co)polyesters with desired compositions. (Co)polyesters exhibited good solubility in common organic solvents such as chloroform, dichloromethane, and tetrahydrofuran and could be cast into transparent, flexible, and tough films from chloroform solution. Inherent viscosities and number average molecular weights of (co)polyesters were in the range 0.77–1.33 dL/g and 43,600–118,000 g/mol, respectively, indicating the achievement of reasonably high‐molecular weights. The 10% weight loss temperatures of (co)polyesters were in the range 390–420 °C, demonstrating their good thermal stability. (Co)polyesters exhibited Tg in the range 146–170 °C and Tg values decreased with increase in mol % incorporation of P‐IPC. The study of non‐isothermal curing by DSC indicated thermal crosslinking of (co)polyesters via propargyloxy groups. The utility of pendant propargyloxy group was demonstrated by post‐modification of the selected copolyester with 1‐(4‐azidobutyl)pyrene, 9‐(azidomethyl)anthracene, and azido‐terminated poly(ethyleneglycol) monomethyl ether via copper(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction. FTIR and 1H NMR spectra confirmed that click reaction was quantitative. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 588–597 相似文献
108.
Anfimov N. V. Vorobel V. Kovalev Yu. S. Kodyš P. 《Physics of Particles and Nuclei Letters》2019,16(6):820-825
Physics of Particles and Nuclei Letters - The Silicon Photomultiplier (SiPM) is a novel semiconducting photodetector which can detect single photons. It consists of many microcells (pixels)... 相似文献
109.
Gas-phase 21Ne nuclear magnetic resonance spectra were measured at the natural abundance of 21Ne isotope for samples consisting of pressurized neon up to 60 bar at room temperature and applying the magnetic field of the strength B0 = 11.7574 T. It showed that the nuclear magnetic resonance frequency is linearly dependent on the density of gaseous neon. The resonance frequency was extrapolated to the zero-density point, and it permitted the determination of the 21Ne nuclear magnetic moment, μ(21Ne) = 0.6617774(10) μN. The present value of μ(21Ne) is not influenced by the bulk magnetic susceptibility of neon and interactions between neon atoms; therefore, it is more precise and reliable than the previous result obtained for μ(21Ne). 相似文献
110.
Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface. 相似文献