全文获取类型
收费全文 | 16943篇 |
免费 | 2681篇 |
国内免费 | 1920篇 |
专业分类
化学 | 12358篇 |
晶体学 | 190篇 |
力学 | 1167篇 |
综合类 | 135篇 |
数学 | 2019篇 |
物理学 | 5675篇 |
出版年
2024年 | 38篇 |
2023年 | 318篇 |
2022年 | 374篇 |
2021年 | 510篇 |
2020年 | 618篇 |
2019年 | 643篇 |
2018年 | 506篇 |
2017年 | 522篇 |
2016年 | 733篇 |
2015年 | 732篇 |
2014年 | 913篇 |
2013年 | 1131篇 |
2012年 | 1509篇 |
2011年 | 1541篇 |
2010年 | 1052篇 |
2009年 | 930篇 |
2008年 | 1082篇 |
2007年 | 979篇 |
2006年 | 981篇 |
2005年 | 792篇 |
2004年 | 601篇 |
2003年 | 545篇 |
2002年 | 548篇 |
2001年 | 462篇 |
2000年 | 345篇 |
1999年 | 360篇 |
1998年 | 288篇 |
1997年 | 269篇 |
1996年 | 298篇 |
1995年 | 237篇 |
1994年 | 206篇 |
1993年 | 159篇 |
1992年 | 169篇 |
1991年 | 174篇 |
1990年 | 131篇 |
1989年 | 126篇 |
1988年 | 84篇 |
1987年 | 70篇 |
1986年 | 80篇 |
1985年 | 60篇 |
1984年 | 54篇 |
1983年 | 44篇 |
1982年 | 32篇 |
1981年 | 31篇 |
1980年 | 29篇 |
1978年 | 24篇 |
1977年 | 25篇 |
1976年 | 23篇 |
1974年 | 20篇 |
1973年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
141.
Unsteady mass transfer in a steady flow field of a laminar forced flow against a rotating disk is analyzed by using a very effective solution method. Rigorous numerical solutions have been obtained for steady and unsteady mass transfer for any relative flow strength of external flow and rotation-induced flow for 0.1 ≤Sc ≤ 10000. Simple but very accurate correlation equations of Sherwood number for both the steady and unsteady mass transfer are proposed. 相似文献
142.
采用微波电子回旋共振等离子体化学气相沉积(MWPECRCVD)方法,使用不同的源气体(CHF3CH4,CHF3C2H2,CHF3C6H6)体系制备了aC∶F∶H薄膜.由于CH4,C2H2,C6H6气体在等离子体中的分解反应不同导致了薄膜的沉积速率和结构上的差异.红外吸收谱的结果表明,用C6H6CHF3作为源气体沉积的薄膜中几乎不含H,而用C2H2CHF3所沉积的薄膜中的含氟量最高,其相应的CF振动峰位向高频方向偏移.薄膜的真空退火结果表明,aC∶F∶H薄膜的热稳定性除了取决于薄膜的CC键浓度外,还与CC键
关键词:
氟化非晶碳膜
电子回旋共振化学气相沉积
红外吸收光谱 相似文献
143.
This paper is concerned with a class of nonlinear delay partial difference equations with variable coefficients, which may
change sign. By making use of frequency measures, some new oscillatory criteria are established. This is the first time oscillation
of these partial difference equations is discussed by employing frequency measures.
相似文献
144.
Two series of size‐fractionated combusted residues, a bag‐house ash and a scrubber residue, from a municipal solid waste incinerator (MSWI) were prepared and extracted by means of sequential chemical extraction (SCE) procedures proposed by Tessier. Concentrations of water‐soluble phase, exchangeable phase, carbonated phase, Fe/Mn oxide phase, organic matter phase, and residual phase bound amphoteric metals (Pb and Zn) were obtained, and have been compared with those of single batch extraction of toxic characteristic leaching procedure (TCLP). In each size fraction of baghouse ash or scrubber residue, lead or zinc shows a common phenomena that the TCLP value is always lower than the content of the water‐soluble fraction. For lead, baghouse ash has a significant size‐dependent distribution on the water‐soluble phase to perform a size‐dependent test of lead in the TCLP test. The zinc TCLP data having less size dependence might be due to that neither the baghouse ash nor the scrubber residue has a size‐dependent distribution on the water‐soluble zinc phase. 相似文献
145.
This paper tries to introduce the reader to the method of using photochemical re-action to copy holographic optical elements(HOEs)in relief.The holographic blazing gratingso copied is groove depth adjustable phase modulability enlarged through copying and 3.3times the diffraction efficiency(DE)of the original grating.It is expected that the newmethod will lead to the mass production of the light-weight HOEs at low cost. 相似文献
146.
Stephen Z. D. Cheng 《Journal of Thermal Analysis and Calorimetry》1997,50(5-6):907-910
147.
148.
149.
150.
Wen-Yin Chen Bo-Jung Chen Hung-Hsin Shih Chien-Hong Cheng 《Applied Surface Science》2006,252(19):6594-6596
A model organic light-emitting diodes (OLEDs) with structure of tris(8-hydroxyquinoline) aluminum (Alq3)/N,N′-diphenyl-N,N′-bis[1-naphthy-(1,1′-diphenyl)]-4,4′-diamine (NPB)/indium tin oxide (ITO)-coated glass was fabricated for diffusion study by ToF-SIMS. The results demonstrate that ToF-SIMS is capable of delineating the structure of multi-organic layers in OLEDs and providing specific molecular information to aid deciphering the diffusion phenomena. Upon heat treatment, the solidity or hardness of the device was reduced. Complicated chemical reaction might occur at the NPB/ITO interface and results in the formation of a buffer layer, which terminates the upper diffusion of ions from underlying ITO. 相似文献