全文获取类型
收费全文 | 2991篇 |
免费 | 81篇 |
国内免费 | 175篇 |
专业分类
电工技术 | 7篇 |
综合类 | 149篇 |
化学工业 | 989篇 |
金属工艺 | 112篇 |
机械仪表 | 62篇 |
建筑科学 | 48篇 |
矿业工程 | 14篇 |
能源动力 | 31篇 |
轻工业 | 1201篇 |
水利工程 | 3篇 |
石油天然气 | 88篇 |
武器工业 | 5篇 |
无线电 | 68篇 |
一般工业技术 | 301篇 |
冶金工业 | 51篇 |
原子能技术 | 63篇 |
自动化技术 | 55篇 |
出版年
2024年 | 14篇 |
2023年 | 82篇 |
2022年 | 121篇 |
2021年 | 146篇 |
2020年 | 153篇 |
2019年 | 154篇 |
2018年 | 88篇 |
2017年 | 142篇 |
2016年 | 124篇 |
2015年 | 102篇 |
2014年 | 183篇 |
2013年 | 358篇 |
2012年 | 360篇 |
2011年 | 318篇 |
2010年 | 159篇 |
2009年 | 143篇 |
2008年 | 116篇 |
2007年 | 107篇 |
2006年 | 79篇 |
2005年 | 63篇 |
2004年 | 74篇 |
2003年 | 36篇 |
2002年 | 23篇 |
2001年 | 19篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 17篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有3247条查询结果,搜索用时 15 毫秒
11.
Styrene-butadiene-styrene (SBS) modified asphalt (SMA) has been widely used in road engineering for decade. However, the phase separation of SMA was obvious during the transport and SBS degraded after aging. To resolve these problems, β-cyclodextrin (β-CD) was used to modify SMA in this work. Conventional properties, storage stability, the effect of short-term aging on the morphology, and rheological property for SMA and β-CD/SMA were investigated. The softening point of modified asphalt reached to the maximum of 66.7°C when 1 wt% β-CD was added to SMA, where the penetration had shown the minimum of 80.8 dmm. In addition, the ductility of β-CD/SMA increased to the maximum of 797 mm when the content of β-CD was increased to 5 wt%. Furthermore, incorporation of β-CD improved the storage stability of SMA. Importantly, the aggregation of SBS was observed in β-CD/SMA, but modifiers distributed uniformly after a short-term aging. The rutting resistance and antiaging performances of SMA were also improved by the addition of β-CD. Considering the comprehensive properties of modified asphalt, the optimum content of β-CD was found to be 2 wt%. 相似文献
12.
Ning Wang Jun Chen Qi Zhou Lianzhou Jiang Liqi Wang Yingjie Dai Dianyu Yu Walid Elfalleh 《European Journal of Lipid Science and Technology》2021,123(6):2000091
Crude wax extracted from rice bran oil (RBO) is used to improve the oleogel properties and oxidative stability of RBO. The effect of crude rice bran wax (CrBW) on the formation characteristics and oxidative stability of oleogels is discussed. The results show that oleogels can be formed with 7.0 wt% CrBW at 20 °C. As the concentration of CrBW increases from 7.0 to 11.0 wt%, the hardness and solid fat content (SFC) of the oleogels increase significantly, and the oleogels are primarily β' crystals. Moreover, oleogel crystals formed with 5 and 7 wt% CrBW are flocculent; when the amount included is 9%, the oleogel crystals are transformed into long dendrites, and the density rises. After 90 days of storage at 20 °C, the peroxide value of oleogels formed with 9.0 wt% CrBW slowly rises from 3.21 to 6.52 mmol kg−1. Practical Applications: Oleogels prepared here by CrBW and RBO are an innovative structural lipid without trans fats. Useful information on the rich fats and nutrients in CrBW is provided, which reduces the production cost and improves the industrial production capacity. 相似文献
13.
为了探究影响GH5家族β-甘露聚糖酶最适pH的各种因素,利用该酶的序列信息,构建了基于氨基酸组成的β-甘露聚糖酶理化性质与其最适pH的相关性模型。结果表明:该酶N端氨基酸序列是影响其最适pH的重要因素,在243个理化性质中有17个呈极显著相关,其中7个呈正相关。优化的转移能量参数相关性最高,为0.78:7个正相关的理化性质中,与螺旋相关的理化性质占3个。优化的转移能量参数和螺旋是影响pH稳定性的最重要的因素。所建立的模型为研究该酶酸碱适应性机理提供了一种简单有效的方法。 相似文献
14.
The morphological and hydrodynamic properties of a series of homogeneous fractions of substituted poly(methylmethacrylate) (A units) bearing keto-β-functional groups (B units) of the general structureCOCH2R, with R = SOxCH3 (x = 1,2) or SO2N(CH3)2, were investigated by intrinsic viscosity, light scattering and partial specific volume measurements in dimethylformamide (DMF) solution at 25°C. For molar substitution degrees , the copolymers behave as flexible random coils. The Stockmayer-Fixman-Yamakawa analysis of the data leads to slightly higher unperturbed dimensions Ko and steric factor σ than those for PMMA, and to stronger chain expansion as a result of the weak hydrogen bonding between DMF and COCH2R units and a positive XAB interaction parameter. For however, copolymers bearing COCH2SO2N(CH3)2 groups behave as worm-like chains, as derived from the Fujii-Yamakawa analysis of the data: the persistence length increases from 380 to 570 Å within the m range 0.57–0.75. This transition from a random coil to a worm-like chain for was tentatively correlated with the accumulation of B units in sterically hindered and self-associated short blocks of average length lB ? 1.6 which provide drastically increased rigidity to the copolymer chain. 相似文献
15.
β-环糊精是由7个D-吡喃葡萄糖单元通过α-1,4-糖苷键键连成环的超分子主体分子,“内疏水、外亲水”的独特结构赋予了其优异的分子识别能力;氧化石墨烯类材料凭借其优良特性成为近几年的研究热点。由β-环糊精和氧化石墨烯构筑的超分子杂化体在兼具二者特有性能的基础上又有新功能的引入。本文综述了β-环糊精-氧化石墨烯超分子杂化体的构筑方式,按二者间的连接方式,分别为共价键和非共价键两种连接方式,其中通过共价键连接是目前最主要的构筑方式;此外对β-环糊精-氧化石墨烯超分子杂化体的特征和表征进行了简述。同时对β-环糊精-氧化石墨烯超分子杂化体在水污染处理、电化学检测、药物控释和催化等领域的应用进展进行了综述。最后对该超分子杂化体在构筑和应用上的发展趋势进行了展望。 相似文献
16.
17.
采用Hypersil-ODS2(4.6mm×250mm,5μm)色谱柱,乙腈-水(70∶30)流动相,242nm检测波长,建立了测定2-苯基-4-对氯苯基-1,5-苯并硫氮杂-α-(丁二酰亚胺基)-β-内酰胺的高效液相色谱法。该法线性范为0~0.1mg/mL,回归方程为A=1.63×108c-2.86×105,相关系数r=0.9994,相对标准偏差为0.33%(c=0.06mg/mL,n=5),检出限为0.08μg/mL。平均回收率在97.2%~102.4%之间。该法重现性好,灵敏度高,简单,快速,准确。 相似文献
18.
Memory effect of locally ordered α-phase in the melting and phase transformation behavior of β-isotactic polypropylene 总被引:1,自引:0,他引:1
Kilwon Cho D Nabi SahebHoichang Yang Byoung-Il KangJoonkyung Kim Sang-Soo Lee 《Polymer》2003,44(14):4053-4059
Structural changes in β-isotactic polypropylene (β-iPP) during the heating were studied by means of differential scanning calorimetry and real-time in situ X-ray diffraction using a synchrotron source. Crystalline phase transformation and the memory effect caused by residual nuclei of α-iPP were observed during the heating of β-iPP. The memory effect observed in β-iPP during heating and crystallization is believed to be due to the existence of locally ordered α-from in the melt. The effect of local α-form order was probed by studying the behavior under heating of samples with a range of thermal histories. Samples were heated above the equilibrium melting temperature of iPP to remove all residual local order and the memory effect associated with this local order. The samples crystallized isothermally at different temperatures exhibited a significantly different melting and phase transformation behavior during heating. β-iPP is found to be an excellent material for the study of polymorphism, phase transformations, and characteristic memory effects in semicrystalline polymers. 相似文献
19.
以β-乳球蛋白氨基酸序列为模板,错位合成β-乳球蛋白多肽,以收集到的牛乳过敏患者血清为抗体,鉴定β-乳球蛋白IgG抗原决定簇,探讨牛乳过敏机理.结果表明,β-乳球蛋白IgG抗原决定簇有2条,它们在β-乳球蛋白中的氨基酸序列定位分别为aa22—36和aa127—141.结果表明通过特异性水解抗原决定簇实现牛奶脱敏的方法是可行的. 相似文献
20.
新型纤维素基螯合纤维的制备与吸附性能 总被引:1,自引:0,他引:1
为了发展水处理的途径,制备了β-环糊精改性的新型纤维素基螯合纤维.运用原子吸收光谱和紫外光谱考察了其对模拟水样中重金属离子(Cu2+)和有机染料(中性红)的吸附性能.实验结果表明,螯合纤维对Cu2+吸附率达6.24 mg/g,符合Langmuir吸附模型;对中性红也具有较强的包结能力.该鏊合纤维水处理能力强,制备简单,操作简便,有潜在的应用价值. 相似文献