全文获取类型
收费全文 | 6889篇 |
免费 | 320篇 |
国内免费 | 117篇 |
专业分类
电工技术 | 197篇 |
综合类 | 271篇 |
化学工业 | 4697篇 |
金属工艺 | 74篇 |
机械仪表 | 93篇 |
建筑科学 | 167篇 |
矿业工程 | 21篇 |
能源动力 | 44篇 |
轻工业 | 282篇 |
水利工程 | 19篇 |
石油天然气 | 457篇 |
武器工业 | 26篇 |
无线电 | 38篇 |
一般工业技术 | 835篇 |
冶金工业 | 31篇 |
原子能技术 | 53篇 |
自动化技术 | 21篇 |
出版年
2024年 | 20篇 |
2023年 | 79篇 |
2022年 | 95篇 |
2021年 | 177篇 |
2020年 | 144篇 |
2019年 | 147篇 |
2018年 | 120篇 |
2017年 | 172篇 |
2016年 | 178篇 |
2015年 | 169篇 |
2014年 | 240篇 |
2013年 | 369篇 |
2012年 | 432篇 |
2011年 | 421篇 |
2010年 | 313篇 |
2009年 | 320篇 |
2008年 | 355篇 |
2007年 | 431篇 |
2006年 | 468篇 |
2005年 | 429篇 |
2004年 | 384篇 |
2003年 | 365篇 |
2002年 | 309篇 |
2001年 | 221篇 |
2000年 | 167篇 |
1999年 | 119篇 |
1998年 | 105篇 |
1997年 | 64篇 |
1996年 | 69篇 |
1995年 | 59篇 |
1994年 | 68篇 |
1993年 | 61篇 |
1992年 | 47篇 |
1991年 | 27篇 |
1990年 | 29篇 |
1989年 | 21篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 30篇 |
1984年 | 26篇 |
1983年 | 26篇 |
1982年 | 25篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7326条查询结果,搜索用时 15 毫秒
41.
42.
《Journal of Industrial and Engineering Chemistry》2014,20(3):947-952
Composites of waste polyethylene (WPE), collected from municipal solid waste/recycled waste rubber powder (RWRP) reactive compatibilizing agent, maleic anhydride (MA) and glass fiber (GF) up to 20 wt%, prepared by melting and irradiated with gamma-rays up to 150 kGy have been studied. Tensile strength (TS), elongation at break (Eb), elastic modulus, hardness, thermal and morphological parameters of the irradiated composites were investigated. The examined mechanical properties have been found to improve largely with filler content. Interesting Eb behavior has been detected for the irradiated composites loaded up to ∼10 wt% GF and has been basically discussed in view of matrix crystallinity and morphology. TGA thermograms of unirradiated composites revealed enhanced thermal stability than that reported for the blend whereas comparatively slight improvement has been demonstrated by irradiation. Whereby insignificant alteration in Tm values was observed by loading or irradiation, yet ΔHm maximum of 3.41 J/g, indicated for the 5 wt% GF irradiated composite with an integral dose of 75 kGy, emphasizes the influence of the relatively moderate load and dose levels on matrix stability. The phenomenon has been confirmed by the respective SEM micrographs. 相似文献
43.
44.
以高密度聚乙烯为树脂基体,同时并采用两种自主开发的木塑专用耐候母粒对其进行光稳定化改性,制备了PE基木塑复合材料,并对其耐候性能进行了研究。结果表明,耐候母粒LS-1和LS-2均对PE基木塑复合材料有较好的抗老化作用。经1000h的氙灯加速老化后,光稳定化改性前后的木塑复合材料的拉伸性能变化不大;改性后的木塑复合材料的冲击强度保持率明显提高,色差明显减小,其中LS-2的效果更佳。 相似文献
45.
46.
对聚乙烯丙纶复合防水卷材产品及应用体系的特色、构成及配套胶粘剂作了深入探讨,并对该类材料的发展定位提出了看法. 相似文献
47.
介绍了某住宅楼采用FSG憎水性膨胀珍珠岩作保温层,氯化聚乙烯-共混作防水层的防水施工技术,同时还提出了在混凝土墙面无泛水槽部位,出屋面管道及排气管道采用辅助防水的措施;指出了作屋面也水时由中间向四周,电梯房屋顶由三边向中间铺贴以有排气孔留到屋顶中间等的注意事项。 相似文献
48.
49.
50.
J Passagot J.M Crance R Deloince H Laveran D Beytout R Fontanges 《Water research》1985,19(9):1167-1170
Viral hepatitis type A is the most prevalent waterborne disease in U.S.A. and the number of cases has been increasing in recent years (Melnick et al., 1978). Till now, few works were performed on Hepatitis A Virus (HAV) concentration in water (Hejkal et al., 1982, Elkana et al., 1983). In this paper the filter adsorption-elution method, widely used with other viruses (Wallis and Melnick, 1967; Fields et Metcalf, 1975; Smith and Gerba, 1982), was selected to concentrate HAV from experimentally-contaminated distilled water. Filtration was performed through two cellulose membranes (RAWP 04700 and HAWP 04700 Millipore). Eluate or filtrate viruses were precipitated by polyethylene glycol 6000. HAV is detected by solid phase radioimmunoassay according to a previously described method (Deloince et al., 1982). Figure 1 shows the results of adsorbing HAV at different pH levels. Analysis of variance pointed out that, for the pH levels between 3 and 4, the differences were not significant (P = 0.05). Table 1 shows the effects of pH and number of passages of 3% beef extract or 0.2 M glycin buffer on HAV elution. For both eluents the differences in function of pH levels and number of passages of eluent through the membrane were not significant (variance analysis P = 0.05). On the other hand, the comparison between the two eluents pointed out the higher efficiency of beef extract (t-test, P = 0.001). After this procedure, HAV replication occurred in human hepatocarcinoma cells PLC/PRF/5 (Fig. 2) inoculated according to a previously described method (Crance et al., 1983). As poliovirus (Sobsey et al., 1973), HAV adsorption is the most efficient at acid pH levels. Between pH 4.5 and 5, the remarkable adsorption decrease might be related to the inversion of the HAV electrostatic charges sign, i.e. to the occurrence of an isoelectric point. The HAV elution is different from the poliovirus one, the efficiency of which increased with pH (Wallis et al., 1972) and eluent passage numbers (Farrah et al., 1976). That might suggest that from pH 7.5, both the HAV particles and membranes have negative charges which give enough repulsive forces to allow a good elution efficiency. Improvement of HAV elution efficiency by beef extract is similar to a result obtained with poliovirus by Landry et al. (1978). This effect might be explained by the proteinous material presence in beef extract. HAV replication in cell cultures shows the biological properties preservation after this procedure. 相似文献