全文获取类型
收费全文 | 16112篇 |
免费 | 1854篇 |
国内免费 | 877篇 |
专业分类
电工技术 | 106篇 |
技术理论 | 1篇 |
综合类 | 798篇 |
化学工业 | 8254篇 |
金属工艺 | 418篇 |
机械仪表 | 388篇 |
建筑科学 | 154篇 |
矿业工程 | 155篇 |
能源动力 | 184篇 |
轻工业 | 2043篇 |
水利工程 | 22篇 |
石油天然气 | 1451篇 |
武器工业 | 148篇 |
无线电 | 1229篇 |
一般工业技术 | 2564篇 |
冶金工业 | 152篇 |
原子能技术 | 175篇 |
自动化技术 | 601篇 |
出版年
2024年 | 108篇 |
2023年 | 476篇 |
2022年 | 793篇 |
2021年 | 1091篇 |
2020年 | 710篇 |
2019年 | 678篇 |
2018年 | 553篇 |
2017年 | 550篇 |
2016年 | 646篇 |
2015年 | 631篇 |
2014年 | 893篇 |
2013年 | 1058篇 |
2012年 | 1076篇 |
2011年 | 1034篇 |
2010年 | 727篇 |
2009年 | 781篇 |
2008年 | 637篇 |
2007年 | 825篇 |
2006年 | 784篇 |
2005年 | 695篇 |
2004年 | 584篇 |
2003年 | 488篇 |
2002年 | 396篇 |
2001年 | 408篇 |
2000年 | 352篇 |
1999年 | 300篇 |
1998年 | 265篇 |
1997年 | 201篇 |
1996年 | 202篇 |
1995年 | 160篇 |
1994年 | 122篇 |
1993年 | 109篇 |
1992年 | 94篇 |
1991年 | 84篇 |
1990年 | 62篇 |
1989年 | 34篇 |
1988年 | 29篇 |
1987年 | 26篇 |
1986年 | 21篇 |
1985年 | 36篇 |
1984年 | 33篇 |
1983年 | 25篇 |
1982年 | 34篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1959年 | 1篇 |
1951年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
分子印迹技术及其应用 总被引:3,自引:0,他引:3
分子印迹技术是将高分子科学、材料科学、生物学、化学工程等有机集成。基于分子印迹技术所制备的分子印迹聚合物具有选择性高、稳定性好、应用范围广等特点 ,近年来得到了日益广泛和深入的研究。介绍了分子印迹技术的原理、分子印迹聚合物的制备方法、分子印迹技术的应用场合和实例 ,并简要预测了分子印迹技术领域未来的发展趋势。 相似文献
52.
A quantum chemical study of the binding of Li+ cation to polyalkyloxides has been carried out. The lithium cation interaction with three polyalkyloxides (polyethylene oxide (PEO), polytrimethylene oxide (PTMO), and polypropylene oxide (PPO)) has been investigated using ab initio molecular orbital theory at the HF/6-31G* level with molecular models for the polymers. Coordination by one to six oxygens was considered. In addition, higher level calculations were carried out using G3(MP2) theory for coordination of Li+ by one oxygen. For coordination of lithium by one oxygen, the binding energy ordering is PTMO>PPO>PEO, with PTMO having the largest lithium cation affinity. The same ordering is found for larger coordination numbers with the exception of coordination by six oxygens, where the ordering changes due to the steric interactions. 相似文献
53.
Banded textures produced in a thermotropic liquid crystal polymer by shearing between glass slides are examined by using both transmission electron and polarized light microscopy. The periodic variation in director orientation about the shear axis, as measured by light microscopy, is shown to be distinctly different from that indicated by electron diffraction. Measurements of birefringence and observation of Zernicke phase contrast indicate periodic variations in optical properties of the polymer, in step with the bands. Such effects are accounted for in terms of a synchronous rotation of the planar aromatic groups about the molecular chain axes. Evidence for an out-of-plane component of molecular orientation is also presented. 相似文献
54.
Poly(vinyl alcohol) is crosslinked in dilute solution (c=0.1 wt%) with glutaraldehyde. The reaction product is characterized by viscometry and gel permeation chromatography (g.p.c.). The intrinsic viscosity decreases with increasing degree of crosslinking and does not depend on temperature. G.p.c. reveals that the reaction product is not homogeneous, but consists of a mixture of particles with different sizes, possibly both intra- and intermolecularly crosslinked molecules. The intramolecularly crosslinked molecules are smaller in size than the initial polymer molecules and their size depends on the degree of crosslinking. They possess a narrow particle size distribution even if the initial polymer sample had a broad molecular weight distribution. 相似文献
55.
合成了一系列用于苯与直链烯烃烷基化反应的含有杂原子的磷铝分子筛固体酸催化剂 (MeZrAPO 5 ) ,同晶取代磷铝分子筛骨架中磷和铝的杂原子包括锆和至少一种选自硅、硼、镓、锗、铁、镁、锡等的元素。考察了晶化温度、晶化时间、杂原子种类、铝源等因素对催化剂合成的影响 ,探索了合成样品中模板剂脱除的最佳条件。结果表明 ,晶化温度高于 15 0℃、n(TEA) /n(Al2 O3 )≥ 1 5以及加入Zr原子都有利于直接生成MeZrAPO 5晶相 ;用小晶粒和高结晶度的铝源合成时 ,分子筛的结晶度高。 相似文献
56.
57.
58.
Shaofeng Wang Jianwei Xu Yuejin Tong Lin Wang Chaobin He 《Polymer International》2005,54(9):1268-1274
A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry 相似文献
59.
Miriam A Martinello Mauro Villegas Maria del C Pramparo 《Journal of the science of food and agriculture》2007,87(8):1559-1563
A process of physical refining wheat germ oil using the technique of molecular distillation (MD) is presented in this work. Wheat germ oil was obtained from the germ by solvent extraction using hexane and also by cold pressing. The oil extracted with hexane was degummed and bleached before deacidification in order to modify the parameters of phosphorus and color. The goal in carrying out the stage of physical refining by MD was to preserve the maximum amount of original antioxidative potential obtained from extraction of the crude oil. The effect of evaporation temperature of one‐stage MD on the efficiency of free fatty acid elimination was studied. The antioxidant portion was followed by means of analytic determination of tocopherols by high‐performance liquid chromatography. Tocopherol retention up to 98% was achieved in the oil extracted by pressing, and yields of up to 96% were achieved in the oil extracted with hexane. Copyright © 2007 Society of Chemical Industry 相似文献
60.