全文获取类型
收费全文 | 569篇 |
免费 | 42篇 |
国内免费 | 33篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 12篇 |
2017年 | 21篇 |
2016年 | 12篇 |
2015年 | 16篇 |
2014年 | 27篇 |
2013年 | 42篇 |
2012年 | 39篇 |
2011年 | 34篇 |
2010年 | 29篇 |
2009年 | 21篇 |
2008年 | 16篇 |
2007年 | 35篇 |
2006年 | 37篇 |
2005年 | 31篇 |
2004年 | 27篇 |
2003年 | 13篇 |
2002年 | 22篇 |
2001年 | 6篇 |
2000年 | 12篇 |
1999年 | 17篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 2篇 |
排序方式: 共有644条查询结果,搜索用时 31 毫秒
1.
Rafael L. X. Consani Mariana R. Carmignani Marcelo F. Mesquita Lourenço Correr‐Sobrinho Ricardo D. Guiraldo 《Gerodontology》2010,27(3):236-242
doi:10.1111/j.1741‐2358.2009.00333.x Effect of microwave treatment on the shear bond strength of different types of commercial teeth to acrylic resin Objective: The purpose of this study was to verify the effect of microwave treatment on the shear bond strength of commercial types of teeth to acrylic resin, when the glossy ridge laps were unmodified (groups 1 and 5), bur abraded (groups 2 and 6), bur grooved (groups 3 and 7) or etched by monomer (groups 4 and 8). Background: Controversial findings have shown that mechanical or chemical changes in ridge‐lap surface of the tooth increase or decrease the bond strength between tooth and acrylic resin, and the microwave disinfection may cause different changes on this bond strength. Materials and methods: Eighty specimens (n = 10) were made with the acrylic resin bonded to tooth glossy ridge lap, polymerised in water at 74°C for 9 h, and deflasked after flask cooling. Specimens of the groups 5, 6, 7 and 8 were individually immersed in 150 ml of water and submitted to microwave treatment in an oven at 650 W for 3 min. Control specimens (groups 1, 2, 3 and 4) were not microwave treated. Shear bond strength test was performed in an Instron machine with a cross‐speed of 1 mm/min. Collected data were submitted to anova and Tukey’s test (α = 0.05). Results: Microwave treatment decreased the shear bond strength values of the tooth/resin bond. In the microwaved and non‐microwaved procedures, mechanical retention improved the shear bond strength when compared with the control and monomer treatments. Conclusion: Shear bond strength of the tooth/resin bond was influenced by the microwave treatment and different commercial teeth association, and was lower for the Biotone tooth. 相似文献
2.
Secretory tissues in vascular plants 总被引:18,自引:3,他引:15
ABRAHAM FAHN 《The New phytologist》1988,108(3):229-257
3.
4.
用多孔强碱型三乙醇胺基聚苯乙烯阴离子交换树脂做为载体,用CNBr与载体上的多羟基作用共价偶联了胰酶。红外光谱表明:其共价偶联反应机理与用CNBr活化多糖类载体并接酶的机理相类似。最适偶联条件研究表明:CNBr用量增多,酶蛋白载量增加。但比活下降。偶联pH为10时,固定化酶有适宜的载量和较高的比活。由于胰酶水解蛋白反应释放出H~+质子,这些质子在载体内积累,使微环境内H~+质子浓度增加,进而使得固定化胰酶的pH—活性曲线在pH9~11范围内未出现下降。在变温和60℃恒温下对固定化酶的热稳定性测试表明:固相酶的热稳定性比天然酶的热稳定性有所提高。 相似文献
5.
无花果蛋白酶通过8%戊二醛活化载体,共价结合到聚苯乙烯阴离子交换树脂GM201上,固定化作用在pH7.7,酶浓度0.8mg/g树脂,4℃下进行6h。得到的固定化酶表观K_m值(酪蛋白,1.11×10~(-4)mol/L)小于溶液酶K_m值(1.96×10~(-4)mol/L);固定化酶活性在pH6~8保持稳定,溶液酶最适pH为7.2;固定化酶最适温度由溶液酶的50~60℃移至37℃;固定化酶25℃保持7d,重复水解酪蛋白7次后,保留83.3%活性。固定化酶对酪蛋白水解度达47.5%,对大豆球蛋白达11.6%。 相似文献
6.
Simultaneous extraction of soil phytoavailable cadmium,copper, and lead by chelating resin membrane 总被引:2,自引:0,他引:2
Cadmium, copper, and lead were extracted from suspensions of contaminated soils using metal chelating exchange resin membranes.
Nine soils with widely varying properties and Cd, Cu and Pb levels were tested. Soil suspensions made up with 4 g in 40 mL
deionized water were equilibrated with 5 cm2 Ca-saturated Chelex exchange resin membrane which was retained inside a polypropylene bag and shaken at 150 rpm for 24 hrs.
Resin membrane extractable Cd, Cu and Pb of the soils were correlated with Cd, Cu, and Pb uptake by young wheat seedlings
grown in these soils and compared with soil Cd, Cu, and Pb extracted by 0.1 M HCl, 0.01 M CaCl2, and 0.005 M Diethylenetriamine pentaacetic acid (DTPA). The amounts of Cd, Cu and Pb extracted by the Ca-saturated Chelex membrane from
all tested soils correlated well with those absorbed by young wheat seedlings. The Ca-saturated Chelex membrane extractable
Cd, Cu and Pb of the soil had the strongest correlation with plant uptake Cd, Cu and Pb among the extraction methods we tested.
It was demonstrated that the Ca-saturated Chelex membrane extraction is an appropriate method in simultaneously estimating
Cd, Cu and Pb phytoavailability of soil and is applicable to a wide range of soils. 相似文献
7.
为挖掘湿地松(Pinus elliottii)松脂合成相关的基因,对不同采脂期的木质部和针叶进行高通量转录组测序,与火炬松(Pinus taeda)参考基因组进行比对,共获得了68 211条unigenes,546 356 450条clean reads,平均比对率达90.21%。将不同时期木质部、木质部与针叶间进行两两对比,以P<0.05,|log2FoldChange|>1.0为标准来筛选差异基因,并进行GO和KEGG富集分析。结果表明,参与萜类物质合成的差异基因有133个,其中大部分富集在MEP途径,从差异基因中挑选8个产脂相关的候选基因进行RT-qPCR验证,确定HMGR、DXS、TPS、ABC转运蛋白基因与产脂存在关联性。通过转录组测序与分析,挖掘出133个参与松脂萜类物质合成相关的差异基因,其中萜烯合酶基因(TPS)和ABC转运基因在正调控萜类物质合成中发挥关键作用。 相似文献
8.
Anion-exchange chromatography on polystyrene resin is shown to be more effective than DEAE-cellulose for purification of glucoamylase from crude enzyme extracts of Aspergillus awamori or from commercial preparations. The glucoamylase from A. awamori culture medium was purified to electrophoretic homogeneity with yields approaching 80%. 相似文献
9.
10.