全文获取类型
收费全文 | 61篇 |
免费 | 15篇 |
国内免费 | 154篇 |
专业分类
化学 | 229篇 |
物理学 | 1篇 |
出版年
2005年 | 1篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 16篇 |
1988年 | 11篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 26篇 |
1984年 | 16篇 |
1983年 | 23篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1966年 | 1篇 |
1965年 | 7篇 |
1964年 | 3篇 |
1963年 | 1篇 |
1960年 | 1篇 |
1959年 | 3篇 |
1958年 | 2篇 |
1953年 | 1篇 |
排序方式: 共有230条查询结果,搜索用时 15 毫秒
1.
The graft copolymerization of N-methacryl-N'-methyl-opiperazine onto segmented polye-therurethane (SPEU) film by Go60-r-preirradiation has been studied. It is found that the grafting time varies with structure of different chain extenders. The grafted substrated become opaque, the contact angle drops down and from SEM photographs with salient micrograph showing grafts of macrochain on the surface of SPEU film. 相似文献
2.
Polyvinyl alcohol carriers bearing active amide and active ester groups were prepared by acetaliza-tion of granular macro-reticular water-insolub1e PVA with glyoxylic acid or p-formylbenzoic acidand further activation reaction with benzotriazole or N-hydroxysuccinimide using DCCI as con-densation agent. The active amides or active esters obtained were easy to react with amines suchas n-butylamine or proteins under mild condition. Ovomucoid, an inhibitor of trypsin was immo-bilized on the above-obtained reactive PVA carrier to give effective affinity adsorbent for the separa-tion or purification of trypsin. 相似文献
3.
The molecular weight of polytetramethylene glycol (PTMG) prepared from tetrahydrofu-ran (THF) by using cocatalysts of BF3-etherate and epichlorohydrin (ECH) in the presence of butylene glycol(BG) increased sharply with the polymer conversion, but at yields higher than 80% but could be exactly controlled by the molar ratio of BG to BF3. The polyether obtained possessed around 70 mol% primaly hydrcxyl end-groups and a hydroxyl end-group functionality of two. The content of ECH derived units in each polymer chain containing 18.2 or 33.8THF derived units is around 1.60 or 2.16 respectively. 相似文献
4.
5.
6.
7.
8.
9.
10.
Initiation mechanism of the photopolymerization of acrylonitrile and methyl methacrylate, usingbinary condensed aromatic hydrocarbon (CAH)-aniline systems as initiator, was studied. The strongerthe electron-donating ability of the aniline derivatives, the faster the the of photopolymerizationwill be. The radical intermediates produced by photoreaction between anthracene and anilinewere detected with ESR spectra. The initiation scheme involves the formation of exciplex betweenthe excited singlet state of CAH and the ground state of aniline as the first step, and then followedby proton transfer, leading to the generation of two kinds of radicals. From the end-group analysisof the polymers obtained, it is suggested that both kinds of radicals are involved in the initiation. 相似文献