全文获取类型
收费全文 | 12594篇 |
免费 | 530篇 |
国内免费 | 204篇 |
专业分类
电工技术 | 225篇 |
综合类 | 600篇 |
化学工业 | 8606篇 |
金属工艺 | 105篇 |
机械仪表 | 125篇 |
建筑科学 | 200篇 |
矿业工程 | 31篇 |
能源动力 | 61篇 |
轻工业 | 801篇 |
水利工程 | 20篇 |
石油天然气 | 869篇 |
武器工业 | 27篇 |
无线电 | 53篇 |
一般工业技术 | 1415篇 |
冶金工业 | 48篇 |
原子能技术 | 111篇 |
自动化技术 | 31篇 |
出版年
2024年 | 31篇 |
2023年 | 98篇 |
2022年 | 160篇 |
2021年 | 233篇 |
2020年 | 203篇 |
2019年 | 203篇 |
2018年 | 177篇 |
2017年 | 262篇 |
2016年 | 268篇 |
2015年 | 272篇 |
2014年 | 404篇 |
2013年 | 612篇 |
2012年 | 794篇 |
2011年 | 772篇 |
2010年 | 604篇 |
2009年 | 631篇 |
2008年 | 639篇 |
2007年 | 782篇 |
2006年 | 882篇 |
2005年 | 734篇 |
2004年 | 670篇 |
2003年 | 669篇 |
2002年 | 575篇 |
2001年 | 472篇 |
2000年 | 409篇 |
1999年 | 361篇 |
1998年 | 313篇 |
1997年 | 202篇 |
1996年 | 155篇 |
1995年 | 127篇 |
1994年 | 127篇 |
1993年 | 109篇 |
1992年 | 75篇 |
1991年 | 54篇 |
1990年 | 50篇 |
1989年 | 31篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 39篇 |
1984年 | 32篇 |
1983年 | 28篇 |
1982年 | 29篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
92.
The photografting copolymerization of a low‐density polyethylene/vinyl acetate (VAC)–maleic anhydride (MAH) binary monomer system was studied from the perspective of dynamics. The total conversion percentage (CP) and grafting conversion percentage (CG) were measured by gravimetry. On the basis of plots of CP and CG as functions of the polymerization time, the total polymerization rate (RP) and grafting polymerization rate (RG) were calculated. In addition, the apparent activation energy (Ea) and the reaction orders of the photografting polymerization under different reaction conditions, such as the total monomer concentration and the concentration of benzophenone (BP), were determined also. The results showed that, in comparison with the photografting polymerization of the two single monomers (VAC and MAH), RP and RG noticeably increased for the VAC–MAH binary monomer system. When the total monomer concentration was kept at 4M, the apparent Ea's of the three photografting polymerization systems were as follows: for VAC ([MAH]/[VAC] = 0/4), Ea's for the total polymerization and grafting polymerization were 41.00 and 43.90 kJ/mol, respectively; for MAH ([MAH]/[VAC] = 4/0, Ea's were 39.65 and 43.23 kJ/mol, respectively; and for the VAC–MAH binary monomer system, Ea's were 34.35 and 40.32 kJ/mol, respectively. These results suggested that the polymerization of the binary system occurred more readily than the other two. The reaction orders of RP with respect to the total monomer concentration of the monomers and the concentration of BP were 1.34 and 0.81, respectively. According to these investigations, it could be inferred that in the binary monomer system, both the free monomers and charge‐transfer complex took part in the polymerization; to the termination of the propagating chains, two possible pathways, unimolecular termination and bimolecular termination, coexisted in this binary monomer system. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 910–915, 2005 相似文献
93.
在复合肥的生产过程中,用流动注射分析测定磷矿,磷石膏,磷酸中的五氧化二磷,该方法制样简单,分析速度快,结果准确。 相似文献
94.
气相法聚乙烯高效催化剂的进展 总被引:2,自引:0,他引:2
综述了国内外气相法聚乙烯高效催化剂研究进展概况,以及各种新型高效催化剂制备技术和性能,并对开发我国新型高效推化剂提出了看法。 相似文献
95.
96.
Previously obtained cloud point curves for mixtures of oligomeric poly(dimethyl siloxanes) (weight fraction W1) with oligomeric polyethylenes have been supplemented by the use of samples of higher molecular weight. Initial flat regions at low-medium W1 as well as a slight shoulder at extremely high W1 are now considered to be due to crystallization, since the temperatures at which they occur are the melting points of the oligoethylenes. The actual cloud point curves were of an unsymmetrical dome shape, the form of which could not be simulated by using a concentration-independent interaction parameter g in the Flory-Huggins equation. However, spinodals calculated by assuming a quadratic dependence of g on composition were of the same shape as the experimental cloud point curves. The critical compositions calculated on this basis were also close to the experimental ones. 相似文献
97.
MAH接枝EPDM增韧PA66的研究 总被引:7,自引:0,他引:7
研究了MAH(马来酸酐)接枝三元乙丙橡胶(EPDM—g-MAH)对尼龙66(PA66)的增韧作用。利用SEM(扫描电镜)观察了共混体系的微观形貌(形态结构),并运用小角激光散射(SALS)方法研究了EPDM的加入对PA66结晶性能的影响。结果表明,未接枝的EPDM与PA66的相容性很差,而EPDM—g—MAH与PA66相容性明显增加,EPDM-g—MAH粒子均匀分散在PA66中,共混体系力学性能有很大提高。随着EPDM—g—MAH用量的增加,PA66球晶尺寸变小,共混体系界面结合更加紧密。 相似文献
98.
99.
100.
用室温对折断裂试验,研究固相法低度氯化聚乙烯老化性能,当氯含量约为7.4%时,其老化时间发生突跃,老化时间发生突跃时,氯含量与试样的氯化温度和老化温度有关. 相似文献