全文获取类型
收费全文 | 906篇 |
免费 | 32篇 |
出版年
2023年 | 3篇 |
2022年 | 8篇 |
2021年 | 16篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 18篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 34篇 |
2014年 | 40篇 |
2013年 | 61篇 |
2012年 | 75篇 |
2011年 | 54篇 |
2010年 | 33篇 |
2009年 | 30篇 |
2008年 | 34篇 |
2007年 | 56篇 |
2006年 | 49篇 |
2005年 | 43篇 |
2004年 | 39篇 |
2003年 | 46篇 |
2002年 | 30篇 |
2001年 | 17篇 |
2000年 | 15篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1974年 | 5篇 |
1964年 | 5篇 |
1961年 | 1篇 |
排序方式: 共有938条查询结果,搜索用时 15 毫秒
21.
The species composition of the damselfly assemblage and the life history patterns of two Coenagrionidae (Ischnura elegans
and Cercion lindeni) were investigated along the urban tract of a river characterized by increasing organic pollution. The
assemblage was dominated by generalist species, usually recorded in lentic habitats, rather than by typical riverine species
and the proportion of the latter decrease at the most polluted sites. At the end of Winter, the mean size and in star distribution
were different between the sampling sites showing that the life history of both species examined were influenced by a degradation
of the environmental quality. A longer reproductive period, absence of diapause, and tolerance of low oxygen concentration
appear to be key factors that allow generalist species I. elegans and C. lindeni to predominate at the polluted sites.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
22.
Cellulase and Sugar Formation by Bacteroides cellulosolvens, a Newly Isolated Cellulolytic Anaerobe 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A newly isolated mesophilic anaerobe, Bacteroides cellulosolvens, has the ability to produce cellulase and to degrade cellulose to cellobiose and glucose. It does not utilize glucose, and it lacks β-glucosidase activity. This anaerobe appears to degrade cellulose to cellobiose by cellulase action, and the presence of cells appears necessary for the formation of glucose. 相似文献
23.
Dr. Ubaldo Armato Gastone G. Nussdorfer Giuliano Neri Enrica Draghi Paola G. Andreis Giuseppina Mazzocchi Franco Mantero 《Cell and tissue research》1978,190(2):187-205
Summary Stereological studies showed that treatment of normal adult human adrenocortical cells in primary culture with ACTH or cyclic-AMP for 2 days results in similar increases in the volume of cells, of the mitochondrial and membrane space compartments and of the surface area of the smooth endoplasmic reticulum and mitochondrial cristae, and decrease in the lipid content of the cells. These changes were more marked after 8 days of treatment. Treatment for 2 days with cyclic-GMP had no striking effects on cell ultrastructure, whereas an 8-day treatment led to ultrastructural changes similar to those obtained after 2 days of ACTH-or cyclic-AMP-treatment. A discrete population of untreated cortical cells maintained a slow proliferation that was not effected by exposure to cyclic-GMP, but was significantly increased in cultures treated with ACTH or cyclic-AMP. Radioimmunological studies showed that untreated cortical cells kept secreting progesterone and cortisol and that ACTH, but neither cyclic nucleotide, increased the secretion rate per cell of both hormones. These results assign a major role to cyclic-AMP and a minor one to cyclic-GMP in the mediation of the differentiation-promoting and trophic effects, but not in the steroidogenic effects of ACTH on the human adrenal cortex.The authors wish to thank Miss A. Coi and Mr. G. Gottardo for their technical assistance. These investigations were partly supported by a contract with CNR-Italy (CT 74.00226/115.3439) 相似文献
24.
Alessandro Ballio Renato Capasso Antonio Evidente Giuliano Grandolini Giacomino randazzo 《Phytochemistry》1982,21(7):1810-1811
The stereostructure of cotylenol, the aglycone of the cotylenins, has been confirmed by chemical correlation with the aglycone of fusicoccin A. 相似文献
25.
Giuliano Armando E. Irie Reiko F. Morton Donald L. 《Cancer immunology, immunotherapy : CII》1981,10(4):243-249
Summary The oncofetal antigen-I (OFA-I) has been defined as an immunogenic antigen that is expressed on human cancer cells and is cross reactive with fetal brain tissue. Quantitative variations in the expression of OFA-I among different cultured melanoma cell lines were determined by absorption techniques based on functionally monospecific anti-OFA-I serum. Allo-antibodies were removed by absorption with lymphoblasts autologous to an OFA-I-positive target cell. Functional monospecificity toward OFA-I was confirmed by complete absorption with a specimen of fetal brain but not by liver from the same fetus.Of 14 melanoma cell lines tested, two did not express OFA-I, whereas 12 expressed the antigen to varying degrees. Five of the cell lines were highly antigenic, and serum absorbed with 5×105 of any of these cell lines could reduce the anti-OFA-I titer (1 : 96) at least four-fold. OFA-I was detected on biopsied melanomas autologous to the antigenic cultured cells. The ability to select highly antigenic cell lines could be useful in further attempts to characterize OFA-I and to monitor tumor immunity in vitro. Antigenic cell lines may improve the response of patients treated in trials of immunotherapy. 相似文献
26.
K A Giuliano 《Analytical biochemistry》1991,197(2):333-339
A simple and inexpensive aqueous two-phase system for the affinity partitioning of proteins is introduced. An aqueous solution consisting of maltodextrin (M100; molecular mass, 1800) and polyvinylpyrrolidone (PVP360; molecular mass, 360,000) formed two phases at 4 degrees C when the concentration of the polymers was 22.5% (w/w) and 4.0% (w/w), respectively. When the amino derivatives of chlorotriazine textile dyes or other azo textile dyes were added to the two-phase system they partitioned asymmetrically, favoring the upper, less dense, PVP360-rich phase. The association of the textile dyes with PVP360 did not prevent them from acting as affinity ligands for proteins. Three of the dyes screened increased the partition coefficient of purified lysozyme nearly 50-fold over a control containing no dye. Parameters such as pH, ionic strength, and dye concentration modulated the affinity-partitioning effect of the system. The partition coefficient of lysozyme in an egg white protein mixture increased severalfold as the total protein content of the system approached 4% (w/w), indicating that protein concentration is also important in determining the partitioning characteristics of this two-phase system. Proteins were efficiently freed of PVP360 and textile dye by recovery in a high-salt solution when another two-phase system was formed upon the addition of a solution of concentrated potassium phosphate to the isolated upper phase of a PVP360/M100/textile dye two-phase system. The affinity-partitioning system presented here allows one to screen large numbers of potentially useful protein ligands to optimize protein separation, followed by direct scaleup to a system size determined by the user. 相似文献
27.
Giuliano Gazzotti Enrico Garattini Mario Salmona 《Chemico-biological interactions》1981,35(3):311-318
Apparent Km- and Vmax-values of nuclear styrene 7,8-oxide hydrolase were determined at different protein concentrations. In the protein concentrations range used no significant differences in the apparent Km-values were observed. The influence of the incubation with different modifiers (i.e. SKF-525A, metyrapone, 1,2-epoxy-3,3,3 trichloropropane, cyclohexene oxide) at two different concentrations on this enzyme activity was also determined. Cyclohexene oxide and 1,2-epoxy-3,3,3-trichloropropane, two well known inhibitors of the microsomal epoxide hydrolase(s) caused a marked inhibition, metyrapone had a strong activating effect whereas SKF-525A had no effect. In vivo pretreatment with phenobarbital significantly induced the nuclear epoxide hydrolase whereas β-naphthoflavone caused a lower degree of induction. This pattern is quantitatively different but qualitatively very similar to the microsomal one. Moreover a toxifying to detoxifying enzymatic activity balance is attempted for the metabolization of the alkenic double bond of styrene, taking into account the ratio between the styrene monooxygenase (toxifying enzyme) and the styrene 7,8-oxide hydrolase (detoxifying enzyme) after the above mentioned pretreatments, both in the microsomal and nuclear fractions. 相似文献
28.
Corrado Barghigiani Giuliano Colombetti Francesco Lenci Rosalba Banchetti Maria Pia Bizzaro 《Archives of microbiology》1979,120(3):239-245
We have investigated the effect of some metabolic drugs, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), 2,4-dinitrophenol (DNP), sodium azide (NaN3), on the photobehavior of single cells of Euglena gracilis, in order to clarify the relevance of different metabolic pathways in the process of photoperception and sensory transduction in this alga. The results obtained show that the photophobic response of Euglena is not affected by the action of these drugs. This suggests that neither the photosynthetic process nor oxidative phosphorylation play a significant role in the phenomenon of photosensory transduction in Euglena.List of Abbreviations DNP
2,4-dinitrophenol
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- PSI
Photosystem I
- PSII
Photosystem II 相似文献
29.
30.
Doris Ribitsch Sonja Heumann Eva Trotscha Enrique Herrero Acero Katrin Greimel Regina Leber Ruth Birner‐Gruenberger Sigrid Deller Inge Eiteljoerg Peter Remler Thomas Weber Petra Siegert Karl‐Heinz Maurer Ilaria Donelli Giuliano Freddi Helmut Schwab Georg M. Guebitz 《Biotechnology progress》2011,27(4):951-960
From a screening on agar plates with bis(benzoyloxyethyl) terephthalate (3PET), a Bacillus subtilis p‐nitrobenzylesterase (BsEstB) was isolated and demonstrated to hydrolyze polyethyleneterephthalate (PET). PET‐hydrolase active strains produced clearing zones and led to the release of the 3PET hydrolysis products terephthalic acid (TA), benzoic acid (BA), 2‐hydroxyethyl benzoate (HEB), and mono‐(2‐hydroxyethyl) terephthalate (MHET) in 3PET supplemented liquid cultures. The 3PET‐hydrolase was isolated from non‐denaturating polyacrylamide gels using fluorescein diacetate (FDA) and identified as BsEstB by LC‐MS/MS analysis. BsEstB was expressed in Escherichia coli with C‐terminally fused StrepTag II for purification. The tagged enzyme had a molecular mass of 55.2 kDa and a specific activity of 77 U/mg on p‐nitrophenyl acetate and 108 U/mg on p‐nitrophenyl butyrate. BsEstB was most active at 40°C and pH 7.0 and stable for several days at pH 7.0 and 37°C while the half‐life times decreased to 3 days at 40°C and only 6 h at 45°C. From 3PET, BsEstB released TA, MHET, and BA, but neither bis(2‐hydroxyethyl) terephthalate (BHET) nor hydroxyethylbenzoate (HEB). The kcat values decreased with increasing complexity of the substrate from 6 and 8 (s?1) for p‐nitrophenyl‐acetate (4NPA) and p‐nitrophenyl‐butyrate (4NPB), respectively, to 0.14 (s?1) for bis(2‐hydroxyethyl) terephthalate (BHET). The enzyme hydrolyzed PET films releasing TA and MHET with a concomitant decrease of the water‐contact angle (WCA) from 68.2° ± 1.7° to 62.6° ± 1.1° due to formation of novel hydroxyl and carboxyl groups. These data correlated with a fluorescence emission intensity increase seen for the enzyme treated sample after derivatization with 2‐(bromomethyl)naphthalene. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011 相似文献