全文获取类型
收费全文 | 7876篇 |
免费 | 1310篇 |
国内免费 | 1112篇 |
专业分类
化学 | 3906篇 |
晶体学 | 467篇 |
力学 | 757篇 |
综合类 | 70篇 |
数学 | 936篇 |
物理学 | 4162篇 |
出版年
2024年 | 9篇 |
2023年 | 71篇 |
2022年 | 115篇 |
2021年 | 173篇 |
2020年 | 214篇 |
2019年 | 196篇 |
2018年 | 167篇 |
2017年 | 245篇 |
2016年 | 295篇 |
2015年 | 240篇 |
2014年 | 406篇 |
2013年 | 547篇 |
2012年 | 494篇 |
2011年 | 658篇 |
2010年 | 533篇 |
2009年 | 632篇 |
2008年 | 567篇 |
2007年 | 624篇 |
2006年 | 512篇 |
2005年 | 527篇 |
2004年 | 452篇 |
2003年 | 355篇 |
2002年 | 308篇 |
2001年 | 255篇 |
2000年 | 225篇 |
1999年 | 210篇 |
1998年 | 183篇 |
1997年 | 169篇 |
1996年 | 129篇 |
1995年 | 115篇 |
1994年 | 93篇 |
1993年 | 86篇 |
1992年 | 107篇 |
1991年 | 55篇 |
1990年 | 47篇 |
1989年 | 47篇 |
1988年 | 36篇 |
1987年 | 39篇 |
1986年 | 24篇 |
1985年 | 13篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 25篇 |
1978年 | 12篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
R. Damodaran B.M. Moudgil 《Colloids and surfaces. A, Physicochemical and engineering aspects》1993,80(2-3):191-195
Electrophoretic deposition of ultrafine calcium phosphates from non-aqueous suspensions onto metallic substrates was attempted in order to obtain coatings with varying porosities. Aging effects were studied by measuring changes in the electrophoretic deposition behavior of the calcium phosphate particles in the non-aqueous suspensions. It was observed that the surfaces of the calcium phosphates develop significant electrostatic charge during aging in order to enable the formation of a dense and uniform deposit. The addition of surface charge conditioners such as HCl was found to have a similar effect. Dispersion conditions were varied to obtain coatings of the desired green densities, which were sintered to different microporosities. 相似文献
992.
Effects of synthesis parameters on zeolite membrane formation and performance by microwave technique
N. Kuanchertchoo R. Suwanpreedee S. Kulprathipanja P. Aungkavattana D. Atong K. Hemra T. Rirksomboon S. Wongkasemjit 《应用有机金属化学》2007,21(10):841-848
Recently, zeolite membranes on porous supports have been extensively studied in the ethanol–water separation process for further use for gasohol production. This work focuses on a NaA membrane synthesized on an α‐Al2O3 support via microwave hydrothermal treatment. Synthesis temperature and time, type of substrate, seed amount and seeding time for the layer growth of the membrane are considered. The formation of as‐synthesized membranes is discussed according to observations by SEM and XRD. In addition, a preliminary study of the performance of the synthesized NaA zeolite membrane was conducted using the pervaporation technique. It was found that, for the synthesized continuous NaA membranes prepared using a 0.5 µm NaA crystal seed concentration of 3 g/l via vacuum seeding, the optimum conditions were 363 K synthesis temperature for 15–20 min via microwave heating. The flux and the separation factor obtained were 1.6 kg/m2 h and 1760.5, respectively, for the substrate without an intermediate layer. Interestingly, the substrate with an intermediate layer showed better flux and separation factor at 1.7 kg/m2 h and 6532.7, respectively. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
993.
Pietro Favia Victor H. Perez-Luna Thomas Boland David G. Castner Buddy D. Ratner 《Plasmas and Polymers》1996,1(4):299-326
Fluoropolymer films have been deposited in the glow and afterglow regions of radio frequency glow discharges fed with C2F6−H2 mixtures. Structure, growth rate, composition, and wettability of the films have been investigated by means of atomic force
microscopy, electron spectroscopy for chemical analysis, secondary ion mass spectrometry, and water contact angle measurements.125I labeled baboon fibrinogen in baboon plasma has been used to study the adsorption of the protein onto the films. Protein
retention, i.e., the binding affinity of the adsorbed protein, has been examined by elution with a sodium dodecyl sulfate
solution. Adsorption and retention of fibrinogen were correlated using multivariate statistical methods with the wettability,
the degree of film fluorination, and the CF
x
(1≤x≤3) group distribution of the coatings. This correlation identified the influence of each variable on the adsorption and retention
of fibrinogen onto these substrates. These variables or surface properties can be easily balanced by properly tuning the experimental
conditions of the glow discharge deposition process. 相似文献
994.
In dealing with phenomena which show a linear response such as viscoelastic or dielectric properties, measurements are carried
out by observing the relationship between the stimulus applied to the sample and the response from the sample. Since the Fourier
analysis technique is effective in obtaining this relationship, two types of circuitries based on Fourier analysis have been
created. Both DMA and dielectric measurement were used to evaluate these circuitries. Results were satisfactory, especially
with respect to tanδ precision.
Zusammenfassung Bei der Arbeit mit Erscheinungen, die wie z.B. viskoelastische oder dielektrische Eigenschaften eine lineare Reaktion zeigen, wurden Messungen durch Beobachtung der Beziehung zwischen der auf die Probe angewendeten Aktion und der von der Probe gezeigten Reaktion durchgeführt. Da die Fourier-Analyse eine effektive Technik zur Ermittlung dieser Beziehung ist, wurden auf der Grundlage der Fourier-Analyse zwei Typen von Schemen geschaffen. Sowohl DMA als auch dielektrische Messungen wurden zur Entwicklung dieser Schemen verwendet. Did Resultate waren zufriedenstellend, insbesondere mit Hinblick auf die Genauigkeit von tanδ.相似文献
995.
利用非等强度、等脉冲相关技术测量甲酚紫染料吸收恢复时间。实验结果给出了甲酚紫染料吸收恢复时间为158ps。 相似文献
996.
D. Lenssen H. L. Bay St. Mesters C. Dieker D. Guggi R. Carius S. Mantl 《Journal of luminescence》1998,80(1-4):461-465
Recent band structure calculations indicate that ruthenium silicide (Ru2Si3) is semiconducting with a direct band gap. Electrical measurements lead to a band gap around 0.8 eV which is technologically important for fiber communications. This makes Ru2Si3 a promising candidate for silicon based optical devices, namely LEDs. We present first results on the epitaxial growth of ruthenium silicide films on Si(1 0 0) and Si(1 1 1) fabricated by the template method, a special molecular beam epitaxy technique. Orientational relationships on Si(1 1 1) have been determined. We characterized the films by Rutherford Backscattering and Channeling, X-ray diffraction and transmission electron microscopy. 相似文献
997.
报道了甲酚紫染料的非线性光学性质的实验研究方法及其结果.利用简并四波混频技术,测量得到甲酚紫甲醇溶液(浓度为5×10~(-4)M)的三阶非线性极化率X~(3)为2.0×10~(-10)esu.此外,利用不同强度皮秒脉冲相关技术得到了甲酚紫甲醇溶液的吸收恢复时间τ_(21)为163ps. 相似文献
998.
金刚石砂轮的精密修整是脆硬材料镜面磨削的关键技术之一,为了保证磨轮起到足够数量微小磨削刃的作用,以使脆硬材料镜面磨削得到较好的面形精度,超微粒金刚石砂轮精密修整技术是目前国内外研究的一个课题。这里介绍了目前国内外修整金刚石砂轮的各种技术方法,并提出采用碗形碳化硅修整器和在线电解修整法,可获得较理想的修整效果。 相似文献
999.
一种新型非晶态分子材料的非线性光学折射率和吸收特性 总被引:8,自引:8,他引:0
用单光束扫描法测量了在532nm处一种新型非晶态分子材料5,5′Bis(dimesitylboryl)2,2′bithiophene的非线性折射率和吸收系数样品非线性透射特性的分析表明,在靠近线性吸收区的532nm处有饱和吸收存在由三能级饱和模型和Zscan法确定了饱和强度、非线性折射率的实部和虚部研究结果表明:这种新型非晶态分子材料具有非常好的光子学应用前景. 相似文献
1000.