全文获取类型
收费全文 | 289篇 |
免费 | 21篇 |
专业分类
310篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 9篇 |
2015年 | 18篇 |
2014年 | 8篇 |
2013年 | 12篇 |
2012年 | 13篇 |
2011年 | 15篇 |
2010年 | 17篇 |
2009年 | 11篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 18篇 |
2005年 | 11篇 |
2004年 | 15篇 |
2003年 | 16篇 |
2002年 | 18篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有310条查询结果,搜索用时 15 毫秒
1.
N. J. Belshaw S. Hakola H. Nevalainen M. Penttil? P. Suominen D. B. Archer 《Molecular & general genetics : MGG》1997,256(1):18-27
Three DNA fragments, trs1, 2 and 3, were isolated from the Trichoderma reesei genome on the basis of their ability to promote autonomous replication of plasmids in Saccharomyces cerevisiae. Each trs element bound specifically to the isolated T. reesei nuclear matrix in vitro, and two of them bound in vivo, indicating that they are matrix attachment regions (MARs). A similar
sequence previously isolated from Aspergillus nidulans (ans1) was also shown to bind specifically to the T. reesei nuclear matrix in vitro. The T. reesei MARs are AT-rich sequences containing 70%, 86% and 73% A+T over 2.9, 0.8 and 3.7 kb, respectively for trs1, 2 and 3. They exhibited no significant sequence homology, but were shown to contain a number of sequence motifs that occur frequently
in many MARs identified in other eukaryotes. However, these motifs occurred as frequently in the trs elements as in randomly generated sequences with the same A+T content. trs1 and 3 were shown to be present as single copies in the T. reesei genome. The presence of the trs elements in transforming plasmids enhanced the frequency of integrative transformation of T. reesei up to five fold over plasmids without a trs. No evidence was obtained to suggest that the trs elements promoted efficient replication of plasmids in T. reseei. A mechanism for the enhancement of transformation frequency by the trs elements is proposed.
Received: 1 March 1997 / Accepted: 13 May 1997 相似文献
2.
Heikki O. Laurila Helena Nevalainen Veijo Mäkinen 《Applied microbiology and biotechnology》1985,21(3-4):210-212
Summary Protoplast formation in Curvularia inaequalis was achieved using non-commercial and commercial snail gut enzymes or Trichoderma harzianum enzymes. The cells were grown for enzyme treatment on cellophane sheets or in liquid cultures for varying periods of time. The production of T. harzianum enzymes is discussed. The highest protoplast yields were 2.6x107 protoplasts/ml enzyme solution. Protoplasts were shown to have zero to four nuclei. Protoplast regeneration was succesfully carried out in semisolid agar. 相似文献
3.
Meria E. Penttilä K. M. Helena Nevalainen Alain Raynal Jonathan K. C. Knowles 《Molecular & general genetics : MGG》1984,194(3):494-499
Summary The possibility of cloning filamentous fungal genes by expression in the yeast Saccharomyces cerevisiae has been studied. A genome bank of Aspergillus niger was made in E. coli using a yeast cosmid shuttle vector and over 10,000 different cosmid clones were individually isolated. Yeast transformants carrying Aspergillus DNA were screened for the expression of the genes for fungal secreted glycoproteins, -galactosidase, -glucosidase, and amyloglucosidase, and for the expression of fungal genes complementing yeast ura3 and leu2 mutations.Of the five Aspergillus genes studied, only one, -glucosidase, was found to be expressed in yeast, and this at a low level. This suggests that there are essential differences between the genes of yeast and filamentous fungi. 相似文献
4.
Taina Karhunen Arja Mäntylä K. M. Helena Nevalainen Pirkko L. Suominen 《Molecular genetics and genomics : MGG》1993,241(5-6):515-522
The chromosomal cellobiohydrolase 1 locus (cbh1) of the biotechnologically important filamentous fungus Trichoderma reesei was replaced in a single-step procedure by an expression cassette containing an endoglucanase I cDNA (egl1) under control of the cbh1 promoter. CBHI protein was missing from 37–63% of the transformants, showing that targeting of the linear expression cassette to the cbh1 locus was efficient. Studies of expression of the intact cbh1-egl1 cassette at the cbh1 locus revealed that egl1 cDNA is expressed from the cbh1 promoter as efficiently as cbh1 itself. Furthermore, a strain carrying two copies of the cbh1-egl1 expression cassette produced twice as much EG I as the amount of CBHI, the major cellulase protein, produced by the host strain. The level of egl1-specific mRNA in the single-copy transformant was about 10-fold higher than that found in the non transformed host strain, indicating that the cbh1 promoter is about 10 times stronger than the egl1 promoter. The 10-fold increase in the secreted EG I protein, measured with an enzyme-linked immunosorbent assay (ELISA), correlated well with the increase in egl1-specific mRNA. 相似文献
5.
Ritva Saarelainen Marja Paloheimo Richard Fagerström Pirkko L. Suominen K. M. Helena Nevalainen 《Molecular genetics and genomics : MGG》1993,241(5-6):497-503
The Trichoderma reesei xln2 gene coding for the pI 9.0 endoxylanase was isolated from the wild-type strain QM6a. The gene contains one intron of 108 nucleotides and codes for a protein of 223 amino acids in which two putative N-glycosylation target sites were found. Three different T. reesei strains were transformed by targeting a construct composed of the xln2 gene, including its promoter, to the endogenous cbh1 locus. Highest overall production levels of xylanase were obtained using T. reesei ALK02721, a genetically engineered strain, as a host. Integration into the cbh1 locus was not required for enhanced expression under control of the xln2 promoter. 相似文献
6.
Elke EM Brouwers Alwin DR Huitema Jos H Beijnen Jan HM Schellens 《BMC clinical pharmacology》2008,8(1):7
Background
The aim of this study was to evaluate long-term platinum retention in patients treated with cisplatin and oxaliplatin. 相似文献7.
Chlorophyll fluorescence induction curves of toxic and non-toxic strains of the cyanobacterium Nodularia were measured and compared with fluorescence curves measured from four species of eukaryotic algae. Both cyanobacteria and algae were isolated from the Baltic Sea. The results show that Nodularia strains can be distinguished from the eukaryotes by applying a pattern recognition procedure to the fluorescence induction curves, suggesting that the fluorescence fingerprinting technique might be useful in environmental monitoring of marine algae. The six studied Nodularia strains could not be distinguished from each other from their fluorescence induction kinetics. However, their fluorescence curves fell into two clear categories, the toxic and the non-toxic Nodularia. Emission spectroscopy and differences in the fluorescence induction curves showed that the ratio of the intensity of the Photosystem I emission peak to the Photosystem II peak is higher in non-toxic Nodularia than in the toxic strains, suggesting that the toxicity affects the structure of the photosynthesis machinery. The effect on photosynthesis may be related to the ability of the microcystins to chelate iron. 相似文献
8.
Leppänen J Huuskonen J Savolainen J Nevalainen T Taipale H Vepsäläinen J Gynther J Järvinen T 《Bioorganic & medicinal chemistry letters》2000,10(17):1967-1969
Entacapone was reacted with phosphorous oxychloride in dry pyridine to yield a phosphate ester. The phosphate promoiety increased aqueous solubility of the parent drug by more than 1700- and 20-fold at pH 1.2 and 7.4, respectively. The phosphate ester provides adequate stability (t(1/2) = 2227 h; pH 7.4) towards chemical hydrolysis, and allowed for release of the parent drug via enzymatic hydrolysis in liver homogenate. 相似文献
9.
Bahareh Honarparvar Sachin A Pawar Cláudio Nahum Alves Jer?nimo Lameira Glenn EM Maguire José Rogério A Silva Thavendran Govender Hendrik G Kruger 《Journal of biomedical science》2015,22(1)
Background
Novel pentacycloundecane (PCU)-lactone-CO-EAIS peptide inhibitors were designed, synthesized, and evaluated against wild-type C-South African (C-SA) HIV-1 protease. Three compounds are reported herein, two of which displayed IC50 values of less than 1.00 μM. A comparative MM-PB(GB)SA binding free energy of solvation values of PCU-lactam and lactone models and their enantiomers as well as the PCU-lactam-NH-EAIS and lactone-CO-EAIS peptide inhibitors and their corresponding diastereomers complexed with South African HIV protease (C-SA) was performed. This will enable us to rationalize the considerable difference between inhibitory concentration (IC50) of PCU-lactam-NH-EAIS and PCU-lactone-CO-EAIS peptides.Results
The PCU-lactam model exhibited more negative calculated binding free energies of solvation than the PCU-lactone model. The same trend was observed for the PCU-peptide inhibitors, which correspond to the experimental activities for the PCU-lactam-NH-EAIS peptide (IC50 = 0.076 μM) and the PCU-lactone-CO-EAIS peptide inhibitors (IC50 = 0.850 μM). Furthermore, a density functional theory (DFT) study on the natural atomic charges of the nitrogen and oxygen atoms of the three PCU-lactam, PCU-lactim and PCU-lactone models were performed using natural bond orbital (NBO) analysis. Electrostatic potential maps were also used to visualize the electron density around electron-rich regions. The asymmetry parameter (η) and quadrupole coupling constant (χ) values of the nitrogen and oxygen nuclei of the model compounds were calculated at the same level of theory. Electronic molecular properties including polarizability and electric dipole moments were also calculated and compared. The Gibbs theoretical free solvation energies of solvation (∆Gsolv) were also considered.Conclusions
A general trend is observed that the lactam species appears to have a larger negative charge distribution around the heteroatoms, larger quadrupole constant, dipole moment and better solvation energy, in comparison to the PCU-lactone model. It can be argued that these characteristics will ensure better eletronic interaction between the lactam and the receptor, corresponding to the observed HIV protease activities in terms of experimental IC50 data.Electronic supplementary material
The online version of this article (doi:10.1186/s12929-015-0115-5) contains supplementary material, which is available to authorized users. 相似文献10.
Feeding behavior of macroinvertebrates is significant in determining aquatic ecosystem functioning. However, there is a lack of knowledge on the distribution of feeding guilds, and in particular on the influence of climate on the feeding functions at large spatial and long temporal scales. In this study, lakes at different climatic zones are examined for modern abundances of midge (Diptera) feeding guilds to establish the relationships between the feeding functions and climate. In addition, 11,000-year and 700-year sediment core records are investigated for their midge feeding guilds to establish their long-term relationships with climate changes. The results indicated that feeding guilds had a significant relationship with air temperature in the modern dataset and similar climate-related patterns in trait abundances had also occurred during the important climatic intervals of the past. In addition, the long-term records agreed with the modern spatial dataset in that feeding guild diversity was decreased under warm and cold climate compared to intermediate climate conditions. The results of this study are significant in demonstrating the influence of climate on the functioning of aquatic ecosystems and in providing valuable information on long-term variability in feeding functions that is needed to better understand future changes under the ongoing climate change. 相似文献