全文获取类型
收费全文 | 356604篇 |
免费 | 7143篇 |
国内免费 | 5060篇 |
专业分类
化学 | 172052篇 |
晶体学 | 5290篇 |
力学 | 21034篇 |
综合类 | 332篇 |
数学 | 54327篇 |
物理学 | 115772篇 |
出版年
2022年 | 2855篇 |
2021年 | 3718篇 |
2020年 | 4010篇 |
2019年 | 4671篇 |
2018年 | 12663篇 |
2017年 | 13017篇 |
2016年 | 10790篇 |
2015年 | 5020篇 |
2014年 | 7258篇 |
2013年 | 12744篇 |
2012年 | 14622篇 |
2011年 | 22492篇 |
2010年 | 15487篇 |
2009年 | 15807篇 |
2008年 | 19834篇 |
2007年 | 22461篇 |
2006年 | 9943篇 |
2005年 | 13474篇 |
2004年 | 10507篇 |
2003年 | 10076篇 |
2002年 | 8625篇 |
2001年 | 7736篇 |
2000年 | 6035篇 |
1999年 | 4459篇 |
1998年 | 3976篇 |
1997年 | 3794篇 |
1996年 | 3726篇 |
1995年 | 3190篇 |
1994年 | 3348篇 |
1993年 | 3188篇 |
1992年 | 3416篇 |
1991年 | 3554篇 |
1990年 | 3490篇 |
1989年 | 3458篇 |
1988年 | 3279篇 |
1987年 | 3271篇 |
1986年 | 3114篇 |
1985年 | 3755篇 |
1984年 | 3840篇 |
1983年 | 3253篇 |
1982年 | 3192篇 |
1981年 | 3071篇 |
1980年 | 2871篇 |
1979年 | 3353篇 |
1978年 | 3346篇 |
1977年 | 3424篇 |
1976年 | 3547篇 |
1975年 | 3245篇 |
1974年 | 3207篇 |
1973年 | 3386篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
A. Lashgari S. Ghammamy R. Ramirez-Tagle G. Salgado-Moran 《Journal of Structural Chemistry》2015,56(8):1505-1513
Two new compounds of fluorine: (C2H5)4N[I2F] and (C2H5)4N[Br2F], have been easily synthesized in a nearly quantitative by a direct reaction of (C2H5)4NF, I2 and Br2. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied computationally with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by timedependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values showes that the experimental results correlate well with the predicted data. 相似文献
82.
83.
Applied Magnetic Resonance - The suggested approach allowed us to derive analytical expressions for modeling the shape of solid-echo signal and its time evolution for a system of three-spin groups... 相似文献
84.
Journal of Applied and Industrial Mathematics - We consider the optimization of the short wave phased antenna arrays as a quadratic programming problem. The penalty function method and the gradient... 相似文献
85.
86.
M. Kroon E. Andreasson E. Persson Jutemar V. Petersson L. Persson M. Dorn P.A.T. Olsson 《Experimental Mechanics》2018,58(1):75-86
Injection-moulding is one of the most common manufacturing processes used for polymers. In many applications, the mechanical properties of the product is of great importance. Injection-moulding of thin-walled polymer products tends to leave the polymer structure in a state where the mechanical properties are anisotropic, due to alignment of polymer chains along the melt flow direction. The anisotropic elastic-viscoplastic properties of low-density polyethylene, that has undergone an injection-moulding process, are therefore examined in the present work. Test specimens were punched out from injection-moulded plates and tested in uniaxial tension. Three in-plane material directions were investigated. Because of the small thickness of the plates, only the in-plane properties could be determined. Tensile tests with both monotonic and cyclic loading were performed, and the local strains on the surface of the test specimens were measured using image analysis. True stress vs. true strain diagrams were constructed, and the material response was evaluated using an elastic-viscoplasticity law. The components of the anisotropic compliance matrix were determined together with the direction-specific plastic hardening parameters. 相似文献
87.
Indermeet Kohli Taylor L. Braunberger Amanda F. Nahhas Fatima N. Mirza Mohsen Mokhtari Alexis B. Lyons Nikiforos Kollias Eduardo Ruvolo Henry W. Lim Iltefat H. Hamzavi 《Photochemistry and photobiology》2020,96(1):208-214
Human skin is exposed to visible light (VL; 400–700 nm) and long-wavelength ultraviolet A1 (UVA1) radiation (370–400 nm) after the application of organic broad-spectrum sunscreens. The biologic effects of these wavelengths have been demonstrated; however, a dose–response has not been investigated. Ten subjects with Fitzpatrick skin phototype IV-VI were enrolled. Subjects were irradiated with 2 light sources (80–480 J cm−2): one comprising VL with less than 0.5% UVA1 (VL+UVA1) and the other pure VL. Skin responses were evaluated for 2 weeks using clinical and spectroscopic assessments. 4-mm punch biopsies were obtained from nonirradiated skin and sites irradiated with 480 J cm−2 of VL+UVA1 and pure VL 24 h after irradiation. Clinical and spectroscopic assessments demonstrated a robust response at VL+UVA1 sites compared with pure VL. Histology findings demonstrated a statistically significant increase in the marker of inflammation (P < 0.05) and proliferation (P < 0.05) at the irradiated sites compared with nonirradiated control. Threshold doses of VL+UVA1 resulting in biologic responses were calculated. Results indicate that approximately 2 h of sun exposure, which equates to VL+UVA1 dose (~400 J cm−2), is capable of inducing inflammation, immediate erythema and delayed tanning. These findings reinforce the need of photoprotection beyond the UV range. 相似文献
88.
89.
Inside Cover: Photoinduced Formation of an Azobenzene‐Based CD‐Active Supramolecular Cyclic Dimer (Chem. Eur. J. 18/2015)
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
90.