全文获取类型
收费全文 | 100435篇 |
免费 | 27666篇 |
国内免费 | 26351篇 |
专业分类
化学 | 64730篇 |
晶体学 | 2108篇 |
力学 | 6937篇 |
综合类 | 1504篇 |
数学 | 13614篇 |
物理学 | 65559篇 |
出版年
2024年 | 513篇 |
2023年 | 901篇 |
2022年 | 1665篇 |
2021年 | 1513篇 |
2020年 | 1703篇 |
2019年 | 2148篇 |
2018年 | 2099篇 |
2017年 | 3283篇 |
2016年 | 2881篇 |
2015年 | 3450篇 |
2014年 | 3643篇 |
2013年 | 5608篇 |
2012年 | 6115篇 |
2011年 | 7841篇 |
2010年 | 11346篇 |
2009年 | 11750篇 |
2008年 | 6058篇 |
2007年 | 5230篇 |
2006年 | 4860篇 |
2005年 | 5003篇 |
2004年 | 5361篇 |
2003年 | 4117篇 |
2002年 | 4019篇 |
2001年 | 4269篇 |
2000年 | 3611篇 |
1999年 | 3333篇 |
1998年 | 2523篇 |
1997年 | 2228篇 |
1996年 | 2536篇 |
1995年 | 2962篇 |
1994年 | 3004篇 |
1993年 | 3069篇 |
1992年 | 2645篇 |
1991年 | 2248篇 |
1990年 | 1916篇 |
1989年 | 2023篇 |
1988年 | 1983篇 |
1987年 | 1274篇 |
1986年 | 1287篇 |
1985年 | 914篇 |
1984年 | 1061篇 |
1982年 | 951篇 |
1981年 | 782篇 |
1980年 | 801篇 |
1979年 | 572篇 |
1978年 | 546篇 |
1977年 | 638篇 |
1976年 | 1042篇 |
1972年 | 532篇 |
1971年 | 441篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
乌桕类可可脂结晶过程中表现体积变化 总被引:1,自引:0,他引:1
为了解乌桕类可可脂(CTCBE)缓冷结晶横向胀罐爆裂原因,研究CTCBE结晶过程中的膨胀特性,采用流体静力法测试了不同等温结晶条件下CTCBE结晶形成的表观密度和表观体积及其横纵向膨胀状况。结果表明,CTCBE缓冷结晶后形成外部和中部两个晶区。在5-25℃的各等温结晶范围内,当结晶温度增加时,外部结晶区域减小、表观密度变化不大;中部结晶区域增大、表观密度明显减小,CTCBE的表观体积、横向、纵向膨胀率均增大,膨胀横向大于纵向。进一步表明CTCBE在自然缓冷固化的表观体积根本上由其结晶温度决定。为有效防止横向胀罐,自然缓冷固化温度应低于10℃。 相似文献
62.
Solid state nuclear track detectors are commonly used for measurements of concentrations of radon gas and/or radon progeny. All these measurements depend critically on the thickness of the removed layer during etching. However, the thickness of removed layer calculated using the etching period does not necessarily provide a sufficiently accurate measure of the thickness. For example, the bulk etch rate depends on the strength of stirring during etching for the LR 115 detector. We propose here to measure the thickness of the removed layer by using energy-dispersive X-ray fluorescence spectrometry. In the present work, a reference silver nitrate pellet is placed beneath the LR 115 detector, and the fluorescence X-ray intensity for silver is then measured. We have found a linear relationship between the X-ray intensity and the thickness of the removed layer for LR 115 detector. This provides a fast method to measure the thickness of removed layer from etching of LR 115 detector. However, this method was found to be inapplicable for the CR-39 detector. Therefore, alternative methods have yet to be explored for the CR-39 detector. 相似文献
63.
We have simultaneously used adsorption isotherm volumetry and Fourier transform infrared spectroscopy in order to take the investigations on amorphous ice structure a step further, especially concerning porosity and annealing-induced modifications. We have studied surface reorganization during annealing and found that the number of surface sites decreases before crystallization, their relative ratios being different for amorphous and crystalline ice. We also present results confirming that ice can have a large specific surface area and nevertheless be non-microporous. 相似文献
64.
65.
Vytautas Getautis Maryte Daskeviciene Tadas Malinauskas Vygintas Jankauskas 《Monatshefte für Chemie / Chemical Monthly》2007,28(5):277-283
Synthesis of a new monomer and polymer containing both ferrocene and hydrazone moieties are reported. The obtained materials
were examined by various techniques including differential scanning calorimetry, UV, IR, NMR spectroscopy, and time of flight
method. These materials may be of particular interest for the development of future electrophotographic photoreceptors as
electron photoemission spectra of the layers showed ionization potentials of 5.35–5.41 eV. The hole drift mobility values
in compositions of the designed structures with bisphenol Z polycarbonate exceeded 10−8 cm2/Vs at strong electric fields. 相似文献
66.
Azizollah Habibi Leyla Mousavifar Issa Yavari Mohammad R. Yazdanbakhsh 《Monatshefte für Chemie / Chemical Monthly》2007,4(8):603-606
Alkyl isocyanides undergo a smooth reaction with alkylidene Meldrum’s acids in the presence of arylhydroxylamines to produce N
1-alkyl-2-(3,5-dioxo-2-aryltetrahydro-4-isoxazolyl)alkanamides in high yields. 相似文献
67.
N. A. Anurova V. A. Blatov G. D. Ilyushin O. A. Blatova A. K. Ivanov-Shitz L. N. Demyanets 《Crystallography Reports》2008,53(6):930-936
A new method was developed for studying voids and channels in crystal structures based on the Voronoi-Dirichlet partition
of crystal space, and 822 structurally characterized ternary compounds Li
p
X
q
O
r
were analyzed for the first time. For these compounds, the dimensionality was determined and the migration patterns of channel
systems capable of providing lithium-ion transport were constructed. The calculated coordinates of lithium atoms in the centers
of the voids are consistent (within 0.4 ?) with the known structural data. Among these compounds, 113 compounds have infinite
channel systems, 60 compounds (18 structural types, STs) have been described earlier in the literature as solid electrolytes,
and 53 compounds (23 STs) can be considered as potential one-, two-, or three-dimensional ionic conductors (13, 3, and 7 STs,
respectively).
Original Russian Text ? N.A. Anurova, V.A. Blatov, G.D. Ilyushin, O.A. Blatova, A.K. Ivanov-Shitz, L.N. Dem’yanets, 2008,
published in Kristallografiya, 2008, Vol. 53, No. 6, pp. 987–993. 相似文献
68.
Accelerated phase transformations and chemical reactions of metastable aluminas and kaolinite, doped with Cu2
+, Mn3
+/Mn2
+ and Fe3
+/Fe2
+ ions, are accompanied with accelerated decrease of surface area and pore volume values. The phenomena in metal ion doped
samples are explained by a catalytic mechanism, in terms of the Jahn-Teller effect.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
69.
70.
基于CSCW的协同编著系统的设计 总被引:3,自引:0,他引:3
讨论了计算机支持的协同工作(CSCW)的主要技术,其中重点讨论了协同编著系统设计中的并发控制技术,指出了其与传统的并发控制技术的区别。根据CSCW的基本原理设计出了一个基于Browse/Server结构的协同编著系统的系统模型。该系统模型比传统的模型更加方便了用户之间通过Internet的浏览器进行协作。 相似文献