全文获取类型
收费全文 | 1125篇 |
免费 | 34篇 |
国内免费 | 2篇 |
专业分类
化学 | 866篇 |
晶体学 | 9篇 |
力学 | 15篇 |
数学 | 64篇 |
物理学 | 207篇 |
出版年
2022年 | 8篇 |
2021年 | 12篇 |
2020年 | 19篇 |
2019年 | 23篇 |
2018年 | 9篇 |
2017年 | 11篇 |
2016年 | 26篇 |
2015年 | 28篇 |
2014年 | 20篇 |
2013年 | 62篇 |
2012年 | 57篇 |
2011年 | 63篇 |
2010年 | 44篇 |
2009年 | 40篇 |
2008年 | 57篇 |
2007年 | 69篇 |
2006年 | 69篇 |
2005年 | 42篇 |
2004年 | 46篇 |
2003年 | 56篇 |
2002年 | 34篇 |
2001年 | 29篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 11篇 |
1996年 | 21篇 |
1995年 | 7篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 23篇 |
1988年 | 5篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 16篇 |
1984年 | 17篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1970年 | 4篇 |
1930年 | 4篇 |
排序方式: 共有1161条查询结果,搜索用时 365 毫秒
11.
Katsuhiro Inomata Chieko Fukuda Kuniyoshi Hori Hideki Sugimoto Eiji Nakanishi 《Journal of Polymer Science.Polymer Physics》2007,45(2):129-137
The phase behavior and crystallization of graft copolymers consisting of poly(n‐hexyl methacrylate) (PHMA) as an amorphous main chain and poly(ethylene glycol) (PEG) as crystallizable side chains (HMAx with 15 ≤ x ≤ 73, where x represents the weight percentage of PEG) were investigated. Small‐angle X‐ray scattering profiles measured above the melting temperature of PEG suggested that a microdomain structure with segregated PHMA and PEG domains was formed in HMA40 and HMA46. This phase behavior was qualitatively described by a calculated phase diagram based on the mean‐field theory. Because of the segregation of PEG into microdomains, the crystallization temperature of the PEG side chains in HMAx was higher than that in poly(methyl acrylate)‐graft‐poly(ethylene glycol) having a similar value of x, which was considered to be in a disordered state above the melting temperature. In HMAx with x ≤ 40, PEG crystallization was strongly restricted, probably because the PEG microdomains were isolated in the PHMA matrix. As a result, the growth of PEG spherulite was not observed because the PEG crystallization occurred after vitrification of the PHMA segregated domains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 129–137, 2007 相似文献
12.
13.
We present a new method for homocysteine quantitation in human plasma based on in-capillary reaction of homocysteine with 2,2′-dipyridyl disulfide. Homocysteine is in this so-called thiol-exchange reaction quantitatively transformed in mixed disulfide concomitantly with formation of an equimolar amount of 2-thiopyridone that is further separated by micellar electrokinetic chromatography and determined specifically at 343 nm. The concentration of homocysteine is thus estimated indirectly from the result of 2-thiopyridone determination. The linear detection range for concentration versus peak area for the assay was from 0.03–3 mM (correlation coefficient 0.994) with a detection limit of 6 μM and a limit of quantitation 20 μM. The inter-day reproducibility of the peak area and the migration time were 1.37% and 0.05%, respectively. The method is simple, relatively rapid and can be easily automated. Moreover the common capillary electrophoresis apparatus with a UV detector can be used to distinguish between normal and pathological hyperhomocysteinemia plasma samples. 相似文献
14.
Y Watanabe Y Matsumoto N Hori H Funato M Matsumoto 《Chemical & pharmaceutical bulletin》1991,39(11):3007-3012
The absorption of two kinds of insulin (from porcine or bovine pancreas) from the rectum of rabbits after the administration of hollow-type suppositories containing insulin and glyceryl-1-monooctanoate (GMO) as an absorption-enhancing agent was investigated. Two types of suppositories were employed: type I containing insulin in an aqueous solution (approx. 25 IU/mg/100 microliters citric buffer solution at pH 3.0) in the cavity of the suppository and GMO mixed with a base material (Witepsol H-15), and type II containing insulin in a crystalline form in the same amount as in type I. Without GMO, the insulin and glucose levels in plasma were unchanged, whereas a marked increase in the plasma levels of insulin and a decrease of glucose concentrations were found following coadministration of insulin and GMO by the type I suppository. Similar enhancement of rectal absorption of insulin was obtained from porcine and bovine sources. In the case of the crystalline insulin, despite the use of the same amount of GMO, porcine insulin was more efficiently absorbed than bovine insulin by the type II suppository. GMO enhances the absorption of insulin in an aqueous solution or a crystalline form, and the dissolution rate of insulin may be an important factor in the rectal absorption of insulin. 相似文献
15.
HPLC determination of (+)-pseudoephedrine and (-)-ephedrine in Japanese herbal medicines containing Ephedra herb using solid-phase extraction 总被引:2,自引:0,他引:2
Ichikawa M Udayama M Imamura K Shiraishi S Matsuura H 《Chemical & pharmaceutical bulletin》2003,51(6):635-639
We developed a rapid and simple HPLC method combined with solid-phase extraction (SPE) for quantitative analysis of (+)-pseudoephedrine (PEP) and (-)-ephedrine (EP) in Japanese herbal (Kampo) medicines such as Kakkon-to, Sho-seiryu-to, Goshaku-san and Bofu-tsusho-san. SPE was performed on TOYOPAK IC-SP M containing propylsulfonic groups. Determination of PEP and EP was carried out using ion-pair reversed-phase HPLC with sodium dodecyl sulfate. N-Benzyldiethylamine was used as an internal standard. The analytical procedure was validated with regard to specificity, linearity, accuracy, and precision. These data suggest that the analytical method developed in this study is useful for quantitative analysis of PEP and EP in various formulations of Kampo medicine containing Ephedra herb. 相似文献
16.
Chau Jin Hu Ryuichi Oshima Yuji Arai Manabu Sen
《Journal of polymer science. Part A, Polymer chemistry》1988,26(9):2423-2433
Copolymers containing an intramolecular electron donor-acceptor (EDA) complex were synthesized by free radical copolymerization of 2-N-carbazolylethyl acrylate and 2-(3,5-dinitrobenzoyloxy)ethyl methacrylate. Glass transition temperatures show a positive deviation from the weight-average values of copolymers, indicating the presence of the specific EDA interaction in copolymers in the solid state. Photoinduced “memory effect,” which is defined as the percentage of the difference of the surface potential given by corona charging before and after irradiation of light on polymer films, was 30% for the copolymer with 5 mol% of acceptor content. Memory effect increased to 70% for a 8 μm film by doping with 2 wt% of trichloroacetic acid (TCAA), and leveled off at 5 wt% of TCAA content. Memory effect was also enhanced by increasing the thickness of polymer films and irradiation time. The largest value of memory effect (85%) was obtained from the film of the copolymer with 5 mol% acceptor content doped with 1 wt% TCAA and with thickness larger than 14 μm. 相似文献
17.
Tsuyoshi Miura Satoshi Tsujino Kohtaro Goto Midori Noguchi Manabu Node Nobuyuki Imai 《Tetrahedron》2005,61(27):6518-6526
The use of the bisfluorous chain-type propanoyl (Bfp) group as a fluorous protective group made it possible to rapidly synthesize the Gb2 and Gb3 oligosaccharide derivatives by a simple fluorous-organic extraction purification. Furthermore, the fluorescence-labeled Gb2 and Gb3 oligosaccharides were prepared as a potential Vero Toxins detecting reagent. 相似文献
18.
19.
20.
Breviones A∼E (1∼5), allelopathic agents isolated from Penicillium brevicompactum Dierckx, are structurally unique pentacyclic or hexacyclic diterpenoid derivatives. The first synthesis of brevione B (2) was achieved by employing the double SN2′-type tandem reaction as a key step. 相似文献