全文获取类型
收费全文 | 10423篇 |
免费 | 1968篇 |
国内免费 | 961篇 |
专业分类
化学 | 6948篇 |
晶体学 | 83篇 |
力学 | 667篇 |
综合类 | 85篇 |
数学 | 1199篇 |
物理学 | 4370篇 |
出版年
2024年 | 23篇 |
2023年 | 240篇 |
2022年 | 345篇 |
2021年 | 395篇 |
2020年 | 421篇 |
2019年 | 415篇 |
2018年 | 350篇 |
2017年 | 336篇 |
2016年 | 515篇 |
2015年 | 477篇 |
2014年 | 549篇 |
2013年 | 751篇 |
2012年 | 913篇 |
2011年 | 1017篇 |
2010年 | 636篇 |
2009年 | 668篇 |
2008年 | 662篇 |
2007年 | 573篇 |
2006年 | 524篇 |
2005年 | 437篇 |
2004年 | 340篇 |
2003年 | 281篇 |
2002年 | 256篇 |
2001年 | 207篇 |
2000年 | 217篇 |
1999年 | 204篇 |
1998年 | 213篇 |
1997年 | 191篇 |
1996年 | 149篇 |
1995年 | 195篇 |
1994年 | 166篇 |
1993年 | 125篇 |
1992年 | 101篇 |
1991年 | 85篇 |
1990年 | 90篇 |
1989年 | 64篇 |
1988年 | 44篇 |
1987年 | 33篇 |
1986年 | 35篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 21篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 10篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1957年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 892 毫秒
801.
Lu K Luo T Xiang Z You Z Fathi R Chen J Yang Z 《Journal of combinatorial chemistry》2005,7(6):958-967
A one-pot synthesis of diverse benzofurans and indoles from readily available starting materials was achieved via the sequential Ugi four-component reaction, intramolecular Diels-Alder reaction, and oxidative aromatization. 相似文献
802.
We report the development of a novel zeolite-incorporated optical fiber sensor and demonstrate its capability for in situ detection of chemical vapors. The sensor comprises a polycrystalline silicalite thin film grown upon the cleaved end face of a standard single-mode optical fiber. The sensor device operates by measuring the optical reflectivity of the zeolite crystals, which changes reversibly in response to the amount of chemical vapor adsorbed in its crystalline microporous structure. The sensor has been successfully demonstrated for measuring the concentration of isopropanol vapor in mixtures with nitrogen gas. 相似文献
803.
804.
Miao W Luo X Wu S Liang Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(1-2):413-416
Order-disorder transitions of 9-monolayer Langmuir-Blodgett (LB) films of 7-(2-octadecyloxycarbonylethyl)guanine (ODCG) before and after recognition to cytidine were investigated by Fourier transform infrared (FTIR) spectroscopy. The different order-disorder transitions suggest that molecular recognition between ODCG and cytidine influence these two LB films on the order-disorder process of alkyl tailchain. Cleavage of the multi-hydrogen bonds was also observed by the infrared spectroscopy at elevated temperature. 相似文献
805.
The Baylis-Hillman reaction of cyclic enones was greatly accelerated in basic water solution with imidazoles as catalysts, which resulted in short reaction time, high yields, and expanding substrate scopes. Bicarbonate solution was shown to be the optimal reaction medium for the reaction in this study. The apparent "enhanced basicity" of imidazoles accounted for the rate increase in alkaline solution. 相似文献
806.
Q.?Zhao H.Z.?Zhang B.?Xiang X.H.?Luo X.C.?Sun D.P.?YuEmail author 《Applied Physics A: Materials Science & Processing》2004,79(8):2033-2036
Selenium dioxide nanowires were fabricated as the co-products of ZnSe nanostructures. The SeO2 nanowires have diameters between 2070 nm and lengths up to several hundred micrometers. The morphology and microstructure of the nanowires were analyzed using TEM, and the growth mechanism of the SeO2 nanowires was explained under the framework of a vapor-solid model, in which structure defects may play a very important role in the nanowire growth. The nanostructured SeO2 materials may find application in both catalytic and biological fields. PACS 81.07.-b; 81.16.-c; 81.07.Nb; 81.05.-t; 68.37.Lp 相似文献
807.
To overcome the complicated and time-consuming difficulties of current models, a new lubrication equation based on boundary velocity slip model for solving the ultra-thin film gas lubrication in hard disk drives is proposed by adopting the nanoscale effect function, N p. The present model is easy to calculate and applicable at nanoscale. The results of numerical calculations indicate that the present model produces a close approximation to that of the exact Boltzmann model. 相似文献
808.
The universal variation pattern of the total energy of various fullerenes including single-walled carbon nanotubes with respect to their extra charge is revealed by the density-functional-theory calculations. The parabolic energy-charge curve with its lowest energy value corresponding to a negatively charged fullerene indicates that these carbon materials have positive electron affinity and are not in the most stable state. The positive electron affinity seems to originate from the pi-electrons and is found to be related to the aggregation property of fullerenes. 相似文献
809.
We present a positive-negative refraction effect in which, under certain conditions, an incident plane wave launched into a photonic crystal excites a positive-refracted Bloch wave and a negative-refracted Bloch wave simultaneously, both of which maintain the polarization. By utilizing this phenomenon, wide-angle beam splitting can be realized at the microscale level. Numerical simulations are employed to demonstrate this anomalous refraction behavior. 相似文献
810.
To simplify the reconstruction calculation of a large-aperture digital hologram we propose a novel Fourier-transformation reconstruction algorithm. When the reconstructed wave is the same as or similar to the reference wave, the higher-order phase term of reconstruction can be compensated for. For example, the variation between the higher-order phase term and the aperture angle with a different field of view in in-line phase-shifting digital holography is analyzed. 相似文献