全文获取类型
收费全文 | 868篇 |
免费 | 50篇 |
出版年
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 27篇 |
2014年 | 22篇 |
2013年 | 35篇 |
2012年 | 38篇 |
2011年 | 31篇 |
2010年 | 23篇 |
2009年 | 33篇 |
2008年 | 37篇 |
2007年 | 43篇 |
2006年 | 36篇 |
2005年 | 40篇 |
2004年 | 36篇 |
2003年 | 34篇 |
2002年 | 53篇 |
2001年 | 19篇 |
2000年 | 25篇 |
1999年 | 21篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 10篇 |
1993年 | 4篇 |
1992年 | 21篇 |
1991年 | 17篇 |
1990年 | 25篇 |
1989年 | 28篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 17篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 6篇 |
1970年 | 6篇 |
1968年 | 4篇 |
排序方式: 共有918条查询结果,搜索用时 187 毫秒
131.
132.
Osamu Yamauchi Tatsuo Yajima Rie Fujii Yuichi Shimazaki Masanobu Yabusaki Masako Takani Minoru Tashiro Takeshi Motoyama Mitsuhiro Kakuto Yasuo Nakabayashi 《Journal of inorganic biochemistry》2008,102(5-6):1218
Intramolecular M(II)H–C interactions (M(II)=Cu(II), Pd(II)) involving a side chain alkyl group of planar d8 and d9 metal complexes of the N-alkyl (R) derivatives of N,N-bis(2-pyridylmethyl)amine with an N3Cl donor set were established by structural and spectroscopic methods. The methyl group from the branched alkyl group (R = 2,2-dimethylpropyl and 2-methylbutyl) axially interacts with the metal ion with the MC and MH distances of 3.056(3)–3.352(9) and 2.317(1)–2.606(1) Å, respectively, and the M–H–C angles of 122.4–162.3°. The Cu(II) complexes showing the interaction have a higher redox potential as compared with those without it, and the 1H NMR signals of the interacting methyl group in Pd(II) complexes shifted downfield relative to the ligand signals. Dependence of the downshift values on the dielectric constants of the solvents used indicated that the M(II)H–C interaction is mainly electrostatic in nature and may be regarded as a weak hydrogen bond. Implications for possible environmental effects of the leucine alkyl group at the type 1 Cu site of fungal laccase are also discussed. 相似文献
133.
Aerobic phototrophic bacterium Roseobacter denitrificans has a nitric oxide reductase (NOR) homologue with cytochrome c oxidase (CcO) activity. It is composed of two subunits that are homologous with NorC and NorB, and contains heme c, heme b, and copper in a 1:2:1 stoichiometry. This enzyme has virtually no NOR activity. Electron paramagnetic resonance (EPR) spectra of the air-oxidized enzyme showed signals of two low-spin hemes at 15 K. The high-spin heme species having relatively low signal intensity indicated that major part of heme b3 is EPR-silent due to an antiferromagnetic coupling to an adjacent CuB forming a Fe-Cu binuclear center. Resonance Raman (RR) spectrum of the oxidized enzyme suggested that heme b3 is six-coordinate high-spin species and the other hemes are six-coordinate low-spin species. The RR spectrum of the reduced enzyme showed that all the ferrous hemes are six-coordinate low-spin species. ν(Fe-CO) and ν(C-O) stretching modes were observed at 523 and 1969 cm−1, respectively, for CO-bound enzyme. In spite of the similarity to NOR in the primary structure, the frequency of ν(Fe-CO) mode is close to those of aa3- and bo3-type oxidases rather than that of NOR. 相似文献
134.
Seigo Sato Toshio Yajima Sukekuni Mukataka Joji Takahashi 《Biotechnology Techniques》1995,9(6):383-388
Summary Repeated batch hydrolysis of casein using immobilized protease were carried out at various do tensions and pH. At any of the pH tested, microbial contamination could be satisfactorily suppressed by maintaining high do. In continuous reaction, contamination could be suppressed throughout 40 days under the do of 190 ppm, whereas contamination was observed after 24 hours with the do of 2.5 ppm. 相似文献
135.
Arata Hidano Takehisa Yamamoto Yoko Hayama Norihiko Muroga Sota Kobayashi Takeshi Nishida Toshiyuki Tsutsui 《PloS one》2015,10(3)
Multidrug-resistant enterococci are considered crucial drivers for the dissemination of antimicrobial resistance determinants within and beyond a genus. These organisms may pass numerous resistance determinants to other harmful pathogens, whose multiple resistances would cause adverse consequences. Therefore, an understanding of the coexistence epidemiology of resistance genes is critical, but such information remains limited. In this study, our first objective was to determine the prevalence of principal resistance phenotypes and genes among Enterococcus faecalis isolated from retail chicken domestic products collected throughout Japan. Subsequent analysis of these data by using an additive Bayesian network (ABN) model revealed the co-appearance patterns of resistance genes and identified the associations between resistance genes and phenotypes. The common phenotypes observed among E. faecalis isolated from the domestic products were the resistances to oxytetracycline (58.4%), dihydrostreptomycin (50.4%), and erythromycin (37.2%), and the gene tet(L) was detected in 46.0% of the isolates. The ABN model identified statistically significant associations between tet(L) and erm(B), tet(L) and ant(6)-Ia, ant(6)-Ia and aph(3’)-IIIa, and aph(3’)-IIIa and erm(B), which indicated that a multiple-resistance profile of tetracycline, erythromycin, streptomycin, and kanamycin is systematic rather than random. Conversely, the presence of tet(O) was only negatively associated with that of erm(B) and tet(M), which suggested that in the presence of tet(O), the aforementioned multiple resistance is unlikely to be observed. Such heterogeneity in linkages among genes that confer the same phenotypic resistance highlights the importance of incorporating genetic information when investigating the risk factors for the spread of resistance. The epidemiological factors that underlie the persistence of systematic multiple-resistance patterns warrant further investigations with appropriate adjustments for ecological and bacteriological factors. 相似文献
136.
Satoru Arata Tohru Hirayama Yuri Akiyama Jun-ichi Mashimo Nobuhiko Kasai Katsuhiko Yoshida Yoshiko Nakamura Yoshio Aoki 《FEMS microbiology letters》1989,60(2):223-225
Abstract In vitro antigenic reactivity of lipid A from Pseudomonas diminuta and Pseudomonas vesicularis with homologous and heterologous lipid A antibodies including monoclonal antibodies was studied by inhibition test of enzyme-linked immunosorbent assay (ELISA). The results suggest that both Pseudomonas lipid As have very similar epitopes, including species-specific and cross-reactive epitopes as compared with enterobacterial lipid A. 相似文献
137.
T Yajima 《Histochemistry》1988,90(4):245-253
The ultrastructural localization of acid phosphatase (ACPase) activity was examined in cultured human gingival fibroblasts in the formative and resorptive phases. In the collagen-secreting fibroblasts, weak ACPase activity was demonstrated in the lysosomes, inner Golgi cisternae, and condensing vacuoles, and none was found in the Golgi-associated endoplasmic reticulum-lysosome system (GERL), presecretory granules, or secretory granules. On the contrary, collagen phagocytosis induced strong ACPase activity in the GERL, which was in addition to the weaker activity found in the same sites as those in the collagen-secreting cells. At the same time, collagen secretion was suppressed, and dense elongated secretory bodies associated with ACPase activity accumulated within the cells. When collagen fibrils had been interiorized in whole or in part within the phagosomes, primary lysosomes derived from the Golgi-GERL complex then fused with them to form phagolysosomes. Collagen degradation occurred within these bodies. The observations indicate significant differences in ACPase activity used as a marker for lysosomal enzyme activities in the different functional phases of fibroblasts. These results suggest that fibroblasts work only one way at a given time, viz., collagen synthesis or collagen degradation. 相似文献
138.
Hisataka Shikama Motoyuki Yajima Michio Ui 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,631(2):278-288
Hepatic glycogen metabolism was studied in rats during the period of transition from the fed to fasted states. Glycogenic activity was measured in vivo based on the incorporation of [14C]glucose into liver glycogen. Its changes were almost parallel to the changes in glucogen synthase activity. Progressive accumulation of liver glycogen that occurred in the fed state was associated with a proportional increase in glycogenic activity. Within 4 h after the cessation of food intake, glycogenic activity showd a precipitous fall from the peak to its nadir without significant changes in glycogen content. Meanwhile, the glucose concentration in the portal vein decreased. Upon further development of fasting, glycogenic activity displayed a progressive regain, reciprocally as glycogen contents gradually decreased. The precipitous fall of glycogenic activity during the transition from the fed to fasted states was associated with a transient increase in plasma glucagon, and was partly overcome by the injection of anti-glucagon serum. It is concluded that the fall of portal venous concentration of glucose and secretion of glucagon act as a signal to initiate liver glycogen metabolism characteristics of the fasted or postabsorptive state. 相似文献
139.
Amino acid substitutions of human interleukin-6 (IL-6) were performed. Single substitution Met162----Ala and double substitutions Leu159.166----Val resulted in a significant decrease of IL-6 activity in the production of immunoglobulin (Ig) from B-cells. Single substitution Leu166----Val or Leu159----Val gave a slight or no significant decrease in the Ig-induction activity, respectively. The receptor-binding activity of each IL-6 mutant was also examined. It was observed that the decrease of the receptor-binding activity was generally in parallel with that of the Ig-induction activity. We therefore suggest that hydrophobic side-chains existing in Met162, Leu159, and Leu166 are significantly involved in the receptor-binding of IL-6. 相似文献
140.
γ-Isomer of 1,2,3,4,5,6-hexachlorocyclohexane (BHC) showed greater decomposition on γ or UV irradiation of five isomers of BHC in crystalline state or in 2-propanol solution. The α- and δ-isomer of BHC and known la, 2a, 3e, 4e, 5e-pentachlorocyclohexane were separated from the irradiation product of crystalline γ-BHC. Four compounds were isolated from the irradiation product of γ-BHC in 2-propanol. Two compounds were tetrachloro-cyclohexenes (C6H6C14): γ-isomer (mp 86 ~87°C) and ?-isomer (mp 99 ~ 100°C). The other two were isomers of pentachlorocyclohexane (C6H7C15). One of them (mp 78 ~ 8.5°C) was consistent with known meso-1e,2a,3a,4a,5e isomer. The molecular structure of the other (mp 75°C) established by X-ray crystal structure analysis was 1α, 2α, 3α, 4β, 5α configuration or le 2a 3e 4e 5e conformation of CI atoms. A reaction mechanism was proposed that included a radical chain reaction and chlorine atom migration. 相似文献