全文获取类型
收费全文 | 280篇 |
免费 | 33篇 |
国内免费 | 71篇 |
专业分类
化学 | 240篇 |
晶体学 | 8篇 |
力学 | 65篇 |
综合类 | 3篇 |
数学 | 12篇 |
物理学 | 56篇 |
出版年
2023年 | 7篇 |
2022年 | 5篇 |
2021年 | 16篇 |
2020年 | 15篇 |
2019年 | 11篇 |
2018年 | 5篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 14篇 |
2014年 | 22篇 |
2013年 | 26篇 |
2012年 | 18篇 |
2011年 | 27篇 |
2010年 | 9篇 |
2009年 | 16篇 |
2008年 | 8篇 |
2007年 | 16篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 21篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 16篇 |
1999年 | 7篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有384条查询结果,搜索用时 296 毫秒
61.
TiAl过渡层对电弧离子镀沉积TiAlN膜层的影响 总被引:6,自引:0,他引:6
利用电弧离子镀,在不锈钢和SiCP增强2024铝基复合材料基底上沉积TiAlN薄膜.结果表明:TiAlN膜层直接沉积在不锈钢基底上,膜层呈[111]择优取向;然而,TiAlN膜层沉积在不锈钢基底的TiAl过渡层上,膜层呈[220]方向择优取向;并且随着过渡层从零开始增厚,TiAlN膜层的织构系数T(111)逐渐减小,而T(200)逐渐增大,但膜层一直以[220]方向择优取向,内应力的存在可能是膜层产生[220]方向择优取向的原因.在复合材料基底TiAl过渡层上沉积,随着负脉冲偏压的增加,TiAlN膜层的择优取向由[111]向[200]转变.在不锈钢基底上,没有TiAl过渡层时,膜层表面相对光滑,大颗粒较少;有了TiAl过渡层,表面大颗粒较多;TiAl过渡层不同沉积时间对膜层表面影响不大,颗粒尺寸相差无几.没有TiAl过渡层时,膜层结合强度很差,有了TiAl过渡层,结合强度明显增加,但结合强度的大小随过渡层沉积时间(厚度)变化. 相似文献
62.
63.
丙烯酸酯乳液压敏胶的研制 总被引:4,自引:0,他引:4
本文介绍了丙烯酸乳液压每胶的研制,并研究了单体、乳化剂、加料方式及温度等因素对乳液压敏胶性能的影响。结果表明,软、硬单体的合适配比、乳化剂的种类及用量是制得粘度接性好,稳定性高的乳液压敏胶的必要条件,采用全连续法加料及严格控制反应温度乳液压敏胶的优异性能具有重要作用。 相似文献
64.
膨胀单体对环氧树脂的改性研究 总被引:11,自引:0,他引:11
介绍膨胀单体和膨胀聚合反应,综述膨胀单体对环氧树脂基复合材料,环氧树脂结合剂的改性研究及其进展,并提出今后的发展方向。 相似文献
65.
剪胶接结构的混合模式断裂分析 总被引:1,自引:0,他引:1
给出了Goland-Reissener型剪接结构的J积分表达在被粘物体小转角和胶层很薄的假设下与路径无关。J积分代表胶层厚度与胶层内最大能量密度的乘积。对单剪接接头,本文计算了裂纹在胶层内和界面上两种情况下的局部I型和Ⅱ型应力强度因子之比,即局部载荷相角,从而给出了单剪接接头的断裂判据。 相似文献
66.
Moon G. Kim Yimin Wu Larry W. Amos 《Journal of polymer science. Part A, Polymer chemistry》1997,35(15):3275-3285
A wood adhesive-type phenol–formaldehyde (PF) resol resin synthesized with a typical formaldehyde to phenol mol ratio of 2.10 was thoroughly cured and studied by the solid-state crosspolarization/magic angle spinning 13C nuclear magnetic resonance (CP/MAS NMR) spectroscopy. The methylene group/phenol mol ratio values found were between 1.35 and 1.46, close to the value of a completely cured PF polymer structure. The amount of formaldehyde emitted during resin curing was very small. Other formaldehyde-derived groups determined from CP/MAS NMR spectra and relatively high levels of oxidation products of formaldehyde determined from water extracts of cured resin raised the total formaldehyde-derived groups/phenol mol ratio value to close to that of the synthesis mol ratio. Technological implications of these findings are discussed. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3275–3285, 1997 相似文献
67.
Bing Wang Chengmin Feng Jiafeng Dang Lijing Niu Chengyi Shen Xiaomei Yang Ting Zhang Xiaoming Zhang 《Macromolecular bioscience》2020,20(2)
Intestinal resection and anastomosis are performed in over a million people with various bowel diseases annually. Excessive fibrosis and anastomotic site leakage are the main complications of anastomosis surgery, despite great improvements in operative technique and equipment in recent years. In this study, cRGD modified poly(p‐dioxanone‐co‐l ‐Phe) (PDPA) membranes are designed and applied in intestinal anastomosis to simultaneously solve the two aforementioned complications. cRGD is modified onto PDPA membranes through both physical absorption and π–π accumulation between d ‐Phe of cRGD and l ‐Phe of PDPA. Although cRGD modification enhanced the biocompatibility of PDPA membranes, cRGD modified PDPA membrane suppresses fibroblast proliferation both in vitro and in vivo as a result of degradation and subsequent release of fibroblast suppressive l ‐Phe from PDPA. Meanwhile, platelets are entrapped by cRGD modified PDPA membranes through the specific binding of cRGD and platelet GPIIbIIIa. cRGD modified PDPA membranes are applied in rat intestinal anastomosis, and both adhesion and stenosis are successfully prevented at anastomotic sites. At the same time, bursting pressure, which represents healing intensity at anastomotic sites, is promoted. The gathering and activation of platelets on PDPA membranes induce secretion of autologous PDGF and VEGF to facilitate angiogenesis and subsequent healing of anastomotic sites. 相似文献
68.
A thin layer of un-cured resin over metal substrates applied by using an acetone-diluted resin solution (without hardener) has been found to be beneficial to strong adhesive bonding. The resin pre-coating (RPC) solution can effectively seal sub-surface micro-cavities and increase the substrate wettability. This study examines possible aftermath effects of the acetone dilution on mechanical properties of epoxy through comparison of samples made from as-received resin and resins diluted once and twice by acetone. RPC can be accepted with confidence in substrate pre-treatments for strong adhesive bonding if no detrimental effect on epoxy properties is observed. Fourier transform infrared spectrum (FTIR) was conducted, showing the spectrogram of the resin previously diluted by acetone was the same as that of as-received resin, i.e. no change in epoxy molecular structures after complete evaporation of acetone. Strength and modulus of elasticity measured by flexural and compressive tests were compared using samples made from as-received resin, and resins diluted once and twice by acetone. Variations among results from the three groups were less than 2%, or negligible, affirming the RPC method can be used for substrate pre-treatments and stronger adhesive bonding. 相似文献
69.
P. Vieillefosse 《Journal of statistical physics》1985,41(5-6):1015-1035
First we show, from the BBGKY hierarchy and under exponential clustering assumption, that the three-dimensional one-component plasma obeys the compressibility sum rule which links the compressibility to the fourth moment of the two-point correlation function. Then it is proved that the first equation of the hierarchy is equivalent to the known value of the correlation function of momentum current and density. Finally we are concerned with the energy density, its definition, and its correlation with the numerical density and with itself. 相似文献
70.
Yu. A. Gorbatkina V. G. Ivanova-Mumjieva A. S. Putyatina T. M. Ul’yanova 《Mechanics of Composite Materials》2007,43(1):1-8
The concentration dependences of adhesive strength are investigated for fiber/dispersedly filled epoxy matrix systems. The
measurements were carried out using an improved model of adhesiometer under normal conditions at a constant rate of loading.
It is shown that the adhesive strength as a function of filler concentration has a maximum, which is more or less pronounced.
The location of the maximum depends on the nature of filler and particle geometry. The increase in the adhesive strength at
the maximum reaches 20–30% in comparison with that for the unfilled epoxy matrix. Since the interfacial strength between steel
wire and all the mineral powders investigated is zero, the growth in the adhesive strength upon introduction of a finely divided
filler in polymer binders is rather un expected. The possible reasons for the phenomenon observed are discussed.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 43, No. 1, pp. 3–14, January–February, 2007. 相似文献