全文获取类型
收费全文 | 159577篇 |
免费 | 18746篇 |
国内免费 | 9006篇 |
专业分类
化学 | 112783篇 |
晶体学 | 1944篇 |
力学 | 8099篇 |
综合类 | 567篇 |
数学 | 17458篇 |
物理学 | 46478篇 |
出版年
2023年 | 1278篇 |
2022年 | 2754篇 |
2021年 | 3193篇 |
2020年 | 4487篇 |
2019年 | 5749篇 |
2018年 | 4668篇 |
2017年 | 4214篇 |
2016年 | 7783篇 |
2015年 | 6859篇 |
2014年 | 8031篇 |
2013年 | 10658篇 |
2012年 | 10211篇 |
2011年 | 9999篇 |
2010年 | 8574篇 |
2009年 | 8501篇 |
2008年 | 8414篇 |
2007年 | 7412篇 |
2006年 | 6721篇 |
2005年 | 6212篇 |
2004年 | 5399篇 |
2003年 | 4753篇 |
2002年 | 5492篇 |
2001年 | 4515篇 |
2000年 | 3853篇 |
1999年 | 2604篇 |
1998年 | 2101篇 |
1997年 | 1809篇 |
1996年 | 1797篇 |
1995年 | 1542篇 |
1994年 | 1572篇 |
1993年 | 1423篇 |
1992年 | 1392篇 |
1991年 | 1378篇 |
1990年 | 1374篇 |
1989年 | 1247篇 |
1988年 | 1063篇 |
1987年 | 1046篇 |
1986年 | 984篇 |
1985年 | 1031篇 |
1984年 | 990篇 |
1983年 | 882篇 |
1982年 | 852篇 |
1979年 | 817篇 |
1978年 | 817篇 |
1977年 | 815篇 |
1976年 | 930篇 |
1975年 | 829篇 |
1974年 | 847篇 |
1973年 | 852篇 |
1972年 | 758篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
The effect of ITO films thickness on the properties of flexible organic light emitting diode 总被引:1,自引:0,他引:1
Indium tin oxide (ITO) thin films were deposited on cyclic olefin copolymer substrate at room temperature by an inverse target sputtering system. The crystal structure and the surface morphology of the deposited ITO films were examined by X-ray diffraction and atomic force microscopy, separately. The electrical properties of the conductive films were explored by four-point probing. Visible spectrometer was used to measure the optical properties of ITO-coated films. The performance of the flexible organic light emitting diode device with different thickness anode was investigated in this study. 相似文献
962.
963.
表面活性剂对均相沉淀法制备单晶Ce2O(CO3)2¢H2O微粉形貌及
形成机理的影响 总被引:2,自引:0,他引:2
在尿素及硝酸铈的混合溶液中分别加入表面活性剂CTAB、 PEG19000、OP-10,利用均相沉淀法合成了不同形貌的CeO2超细前驱体Ce2O(COa)2·H2O,采用X射线衍射及透射电子显微镜等测试手段,对产品的物相和形貌进行了表征.实验结果表明,所得产品均为斜方晶系的单晶Ce2O(CO3)2·H2O,且表面活性剂的加入使晶体的晶化程度明显提高;添加不同的表面活性剂得到不同形貌尺寸的产物: 阳离子型表面活性剂CTAB对Ce2O(CO3)2·H2O晶体的形貌影响不大,所得产物尺寸变小,且分散性得到一定的改善;非离子型表面活性剂对所得产物的形貌影响显著.加入PEG19000和OP-10分别得到了形状排列有序的、尺寸较均匀的、较规则无团聚的微米棒及具有紧密结合中心的发散状的花样微粒.不同形貌前驱体的形成与晶粒形成生长机理的改变有关. 相似文献
964.
不同方法制备的CO2-3替换磷灰石固溶体晶体化学的FTIR研究 总被引:1,自引:0,他引:1
采用不同方法制备了CO2-3替换的磷灰石固溶体,利用FTIR结合XRD对其进行了晶体化学研究,结果表明均相沉淀法制备的碳羟磷灰石(CHAP)属B型替换且替换方式是[CO3·OH]四面体替换[PO4]四面体;固相离子交换法制备的CHAP属A型替换且替换方式是[CO3]三角形配位体替换通道位置的OH-;固相反应法制备的碳氟磷灰石(CFAP)属B型替换,其替换方式是[CO3·F]四面体替换[PO4]四面体;sol-gel法制备的CHAP属AB混合型替换,其Ψ3分裂为Ψ3-1,Ψ3F,Ψ3-4.高斯函数法拟合表明Ψ3F峰是A型替换的Ψ3-2与B型替换的Ψ3-3的叠合.当WCO2-3<3.34%时,随CO2-3含量增加,A型替换量增大,且当WCO2-3=3.34%时达最大值,当3.34%<WCO2-3<7.52%时,随CO2-3含量增加,B型替换量增大,且当WCO2-3= 7.52%时亦到饱和. 相似文献
965.
966.
针对高功率二极管重复率抽运的V型非稳腔Yb3+∶YAG激光头,提出了利用金刚石窗口冷却和直接水冷相结合的复合冷却设计.在YAG片的抽运面进行直接水冷,同时在激光提取面利用金刚石窗口冷却介质.金刚石优异的导热性能不仅能够有效地冷却激光介质,还能消除横向的温度梯度,解决了高功率激光器冷却和高功率抽运的矛盾.模拟结果表明对掺杂10 at %厚度为1.6 mm的Yb3+∶YAG片在抽运功率密度为20 kW/cm2,重复频率为10 Hz的条件下,要将最高温度控制在可接受的范围内(比如320 K),周围冷却水的对流换热系数约为4000 W/m2K. 相似文献
967.
We propose an experimentally feasible scheme to generate Greenberger-Horne-Zeilinger type of maximal entanglement among three atomic ensembles, and show one of the applications, controlled secure direct communication. The scheme involves laser manipulation of atomic ensembles, quarter- and half-wave plates, beam splitters, polarizing beam splitters and single-photon detectors, which are within the reach of current experimental technology. 相似文献
968.
A. Yu. Khnykov S. A. Zav’yalov E. I. Grigor’ev S. N. Chvalun 《Polymer Science Series A》2006,48(11):1157-1163
Poly(p-xylylene)-based nanocomposites containing various amounts of copper have been prepared by vacuum codeposition on a cooled substrate. On the basis of the relationship between the electrical conductivity of composites and the volume content of copper, the percolation threshold has been estimated as 10%. This value coincides with the corresponding parameter derived from the concentration dependence of the electrical resistance temperature coefficient. It has been shown that the conductivity of the nanocomposites increases with the moisture content and their moisture sensitivity decreases with an increase in the content of copper from a concentration of 4%. An analysis of the kinetics of the sensor response measured for various moisture contents has shown that the capacity structure of the samples rearranges during adsorption of water. According to the advanced model, the value of the sensor response is determined by a reduction in the height of the potential barrier between nanoparticles and a change in the fractal characteristics of nanocomposites that results from the adsorption of water molecules. 相似文献
969.
The aggregation of dansyl chloride (DNS-Cl) in acetone has been studied in detail by steady-state fluorescence techniques.It has been demonstrated that DNS-Cl is stable in acetone during purification and aggregation study processes.The aggregates are not solvolyzed in acetone,and do not take part n any chemical reactions either.It has been found that DNS-Cl tends to aggregate even when its concentration is much lower than its solubility in acetone.The aggregation is reversible,and both the aggregation and the deaggregation are very slow processes.Introduction of SDS has a positive effect upon the formation and stabilization of the aggregates. 相似文献
970.
I. G. Alekseev P. E. Budkovsky V. P. Kanavets L. I. Koroleva B. V. Morozov V. M. Nesterov V. V. Ryltsov D. N. Svirida A. D. Sulimov V. V. Zhurkin Yu. A. Beloglazov A. I. Kovalev S. P. Kruglov D. V. Novinsky V. A. Shchedrov V. V. Sumachev V. Yu. Trautman N. A. Bazhanov E. I. Bunyatova 《Physics of Atomic Nuclei》2002,65(2):220-228
New experimental data on the spin-rotation parameters A and R measured for elastic π ± p scattering in the resonance region and on the asymmetry in pC scattering at primary momenta in the range 1.35–2.02 GeV/c, as well as in quasielastic proton scattering on nuclei in the same momentum range, are summarized. All these data were recently obtained by using the proton synchrotron installed at the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The spectrum and features of seven isospin-3/2 baryon resonances that form a peak in the total cross section at a c.m. energy of 1.9 GeV are analyzed on the basis of new data on the parameters A and R, and the results of this analysis are presented. The experiments surveyed in this article were performed by a collaboration of researchers from ITEP and the Petersburg Nuclear Physics Institute (PNPI, Gatchina), the ITEP-PNPI collaboration. 相似文献