全文获取类型
收费全文 | 1146篇 |
免费 | 10篇 |
国内免费 | 45篇 |
专业分类
化学 | 326篇 |
晶体学 | 1篇 |
力学 | 3篇 |
综合类 | 8篇 |
数学 | 7篇 |
物理学 | 48篇 |
综合类 | 808篇 |
出版年
2023年 | 7篇 |
2022年 | 24篇 |
2021年 | 28篇 |
2020年 | 21篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 12篇 |
2016年 | 20篇 |
2015年 | 16篇 |
2014年 | 32篇 |
2013年 | 48篇 |
2012年 | 29篇 |
2011年 | 41篇 |
2010年 | 42篇 |
2009年 | 50篇 |
2008年 | 52篇 |
2007年 | 72篇 |
2006年 | 58篇 |
2005年 | 57篇 |
2004年 | 92篇 |
2003年 | 36篇 |
2002年 | 44篇 |
2001年 | 55篇 |
2000年 | 59篇 |
1999年 | 54篇 |
1998年 | 44篇 |
1997年 | 28篇 |
1996年 | 31篇 |
1995年 | 26篇 |
1994年 | 26篇 |
1993年 | 12篇 |
1992年 | 13篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有1201条查询结果,搜索用时 15 毫秒
991.
赵涛 《东华大学学报(英文版)》2004,21(5):33-35
The paper discussed the synthesis and application of sodium benzoylthioglycollate (BTG) to cotton cellulose. The main product was proved to be BTG. Dyeing substantivity of modified cotton fibre by BTG with disperse dye were improved. The effect of modification conditions, such as the property of alkali and its using amount, curing temperature and time were discussed. Colour yield and resistance to wash fastness were also measured. 相似文献
992.
自由基与纸浆漂白(Ⅰ)——自由基的产生及其在漂白中的作用 总被引:9,自引:0,他引:9
论述在纸浆的常用漂白剂漂白过程中自由基的产生、自由基与过渡金属离子的关系,自由基的漂白作用及其对碳水化全物的影响等。 相似文献
993.
在聚乙烯醇(PVA)存在下,铑(Ⅲ)与钨酸盐及番红花T(ST)形成的离子缔合物在480nm处产生最大吸收.据此建立了测定铑(Ⅲ)的光度分析方法,其表观摩尔吸光系数ε达108L·mol-1·cm-1数量级.方法的检测范围为0.15~1.5 ng/25ml.大量存在的常见离子对Rh(Ⅲ)的测定不干扰.用此方法测定了催化剂及工业产品中铑的含量,结果与标准方法(SnCl2法)一致. 相似文献
994.
Effect of Added Poly (vinyl pyrrolidone) during Condensation on Properties of Poly(p-phenylene terephthalamide)Pulp 总被引:1,自引:0,他引:1
Poly (p-phenylene terephthalamide) (PPTA) pulp was prepared by polycondensation of the p-phenylene diamine (PPDA) with terephthaloyl chloride (TPC) in the completely anhydrous solvent system of N-methyl pyrrolidone (NMP) having calcium chloride, in the presence of poly (vinyl pyrrolidone) (PVP) having a viscosity average molecular weight lower than 40 000. It was confirmed that the polycondensation could be accelerated, the inherent viscosity of the polymer could be increased, and the polymers could be fibrillated more easily by the addition of the PVP. FTIR and X-ray spectra proved that PVP had not combined into molecular chains of the resultant PPTA pulps. The morphology of the resultant pulps, the effect of viscosity average molecular weight, amount and adding mode of PVP on inherent viscosity, specific surface area,and mean length of the resultant pulps were discussed in detail. And the friction and wear properties of the compound reinforced by the resultant pulps were simply investigated. 相似文献
995.
袁建畅 《西安工程科技学院学报》2000,14(3):251-255
在分析了机械式和气动成卷机成卷压力控制系统的基础上 ,提出了一种采用电液比例控制技术的成卷机控制系统 .它不仅可以提高成卷质量 ,而且可以简化系统设计 ,降低成本 ,是一种有希望的成卷机成卷压力控制系统 . 相似文献
996.
介绍了转杯纺棉氨复合纱的纺纱原理,并在经过改装的转杯纺纱机上,选用两种规格的氨纶丝,通过调整氨纶丝的牵伸倍数纺制不同外观和性能的转杯纺棉氨复合纱。经纱线外观和性能的测试分析,表明氨纶丝牵伸倍数对转杯纺棉氨复合纱的外观和性能有一定的影响。 相似文献
997.
通过原子吸收分光光度计(FAAS)对原料中金属离子含量进行定量分析.以果胶酸钙为模型物,考察氢氧化钠、草酸钠等脱果胶试剂对棉秆皮部的果胶脱除及化学成分的影响,进而探讨改进全棉秆化机浆成浆性能的方法.实验结果表明:各脱果胶试剂与果胶酸钙模型物反应速率的关系为2 2 43 4Na C O NaOHNa POv>v>v;用3%草酸钠进行皮部预处理,棉秆皮部果胶脱除率可达到53.72%.对全棉秆化机浆漂白结果显示,当温度90,℃、草酸钠用量3%的预处理条件下,以6.5%NaOH和11%H2O2制得全棉秆化机浆白度可以达到76.2%,尘埃度可降至50.10,mm2/m2. 相似文献
998.
In Vivo Osteogenic Differentiation of Human Dental Pulp Stem Cells Embedded in an Injectable In Vivo‐Forming Hydrogel 下载免费PDF全文
Ja Yong Jang Seung Hun Park Ji Hoon Park Bo Keun Lee Jeong‐Ho Yun Bong Lee Jae Ho Kim Byoung Hyun Min Moon Suk Kim 《Macromolecular bioscience》2016,16(8):1158-1169
In this study, human dental pulp stem cells (hDPSCs) are examined as a cellular source for bone tissue engineering using an in vivo‐forming hydrogel. The hDPSCs are easily harvested in large quantities from extracted teeth. The stemness of harvested hDPSCs indicates their relative tolerance to ex vivo manipulation in culture. The in vitro osteogenic differentiation of hDPSCs is characterized using Alizarin Red S (ARS), von Kossa (VK), and alkaline phosphatase (ALP) staining. The solution of hDPSCs and a methoxy polyethylene glycol‐polycaprolactone block copolymer (PC) is easily prepared by simple mixing at room temperature and in no more than 10 s it forms in vivo hydrogels after subcutaneous injection into rats. In vivo osteogenic differentiation of hDPSCs in the in vivo‐forming hydrogel is confirmed by micro‐computed tomography (CT), histological staining, and gene expression. Micro‐CT analysis shows evidence of significant tissue‐engineered bone formation in hDPSCs‐loaded hydrogel in the presence of osteogenic factors. Differentiated osteoblasts in in vivo‐forming hydrogel are identified by ARS and VK staining and are found to exhibit characteristic expression of genes like osteonectin, osteopontin, and osteocalcin. In conclusion, hDPSCs embedded in an in vivo‐forming hydrogel may provide benefits as a noninvasive formulation for bone tissue engineering applications.
999.
Muhammad Hariadi Nawawi Rosfarizan Mohamad Paridah Md Tahir Ainun Zuriyati Asaari Wan Zuhainis Saad 《Molecules (Basel, Switzerland)》2021,26(14)
The present work reports the biobleaching effect on OPEFB pulp upon utilisation of extracellular xylano-pectinolytic enzymes simultaneously yielded from Bacillus amyloliquefaciens ADI2. The impacts of different doses, retention times, pH, and temperatures required for the pulp biobleaching process were delineated accordingly. Here, the OPEFB pulp was subjected to pre-treatment with xylano-pectinolytic enzymes generated from the same alkalo-thermotolerant isolate that yielded those of higher quality. Remarkable enhanced outcomes were observed across varying pulp attributes: for example, enzyme-treated pulp treated to chemical bleaching sequence generated improved brightness of 11.25%. This resulted in 11.25% of less chlorine or chemical consumption required for obtaining pulp with optical attributes identical to those generated via typical chemical bleaching processes. Ultimately, the reduced consumption of chlorine would minimise the organochlorine compounds found in an effluent, resulting in a lowered environmental effect of paper-making processes overall as a consequence. This will undoubtedly facilitate such environmentally-friendly technology incorporation in the paper pulp industry of today. 相似文献
1000.
不同时期干旱胁迫对棉花生长和产量的影响Ⅱ棉花生长发育及生理特性的变化 总被引:6,自引:0,他引:6
在棉花生育中、后期缺水会使株高降低,果枝数、果节数、铃数减少,铃期变短,脱落增加,导致产量下降。随土壤含水量降低,棉叶水势下降,水分饱和亏上升,叶绿素含量降低,蒸腾强度减弱。叶片水分饱和亏与土壤含水量及叶片蒸腾强度具有高度相关关系,可用作反映棉叶水分状况、指导灌溉的诊断指标。 相似文献