全文获取类型
收费全文 | 740篇 |
免费 | 38篇 |
出版年
2021年 | 5篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 8篇 |
2016年 | 10篇 |
2015年 | 16篇 |
2014年 | 22篇 |
2013年 | 33篇 |
2012年 | 33篇 |
2011年 | 38篇 |
2010年 | 19篇 |
2009年 | 21篇 |
2008年 | 24篇 |
2007年 | 36篇 |
2006年 | 47篇 |
2005年 | 38篇 |
2004年 | 32篇 |
2003年 | 40篇 |
2002年 | 43篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1978年 | 5篇 |
1974年 | 7篇 |
1972年 | 7篇 |
1971年 | 4篇 |
1969年 | 5篇 |
1968年 | 7篇 |
1967年 | 4篇 |
1932年 | 5篇 |
1930年 | 4篇 |
1927年 | 6篇 |
排序方式: 共有778条查询结果,搜索用时 666 毫秒
61.
The heterofermentative lactic acid bacterium Oenococcus oeni requires pantothenic acid for growth. In the presence of sufficient pantothenic acid, glucose was converted by heterolactic fermentation stoichiometrically to lactate, ethanol and CO2. Under pantothenic acid limitation, substantial amounts of erythritol, acetate and glycerol were produced by growing and resting bacteria. Production of erythritol and glycerol was required to compensate for the decreasing ethanol production and to enable the synthesis of acetate. In ribose fermentation, there were no shifts in the fermentation pattern in response to pantothenate supply. In the presence of pantothenate, growing O. oeni contained at least 10.2 microM HSCoA, whereas the HSCoA content was tenfold lower after growth in pantothenate-depleted media. HSCoA and acetyl-CoA are cosubstrates of phosphotransacetylase and acetaldehyde dehydrogenase from the ethanol pathway. Both enzymes were found with activities commensurate with their function in ethanol production during heterolactic fermentation. From the kinetic data of the enzymes and the HSCoA and acetyl-CoA contents, it can be calculated that, under pantothenate limitation, phosphotransacetylase, and in particular acetaldehyde dehydrogenase activities become limiting due to low levels of the cosubstrates. Thus HSCoA deficiency represents the major limiting factor in heterolactic fermentation of glucose under pantothenate deficiency and the reason for the shift to erythritol, acetate, and glycerol fermentation. 相似文献
62.
NMR experiments for the sign determination of homonuclear scalar and residual dipolar couplings 总被引:1,自引:0,他引:1
A modified version of the JHH-TOCSY experiment, `signed COSY', is presented that allows the determination of the sign of residual dipolar 1H-1H coupling constants with respect to the sign of one-bond 1H-X coupling constants in linear three-spin systems X-1H-1H, where X = 13C or 15N. In contrast to the original JHH-TOCSY experiments, the signs of J
HH couplings may be determined for CH2-CH2 moieties and for uniformly 13C/15N-labelled samples. In addition, sensitivity is enhanced, diagonal peaks are suppressed and cross peaks are observed only between directly coupled protons, as in a COSY spectrum. 相似文献
63.
Patrik Andersson Kerstin Nordstrand Maria Sunnerhagen Edvards Liepinsh Ivars Turovskis Gottfried Otting 《Journal of biomolecular NMR》1998,11(4):445-450
Spin-state selective experiments, HSQC-/ and CT-HMQC-/, are proposed for the simple and rapid measurement of scalar one-bond coupling constants in two-dimensional,1 H-detected 15N-1H or13 C-1H correlation experiments based on HSQC and HMQC schemes. Pairs of subspectra are obtained, containing either the high-field or the low-field component of the doublet representing the one-bond coupling constant. The subspectral editing procedure retains the full sensitivity of HSQC and HMQC spectra recorded without heteronuclear decoupling during data acquisition, with a spectral resolution similar to that of decoupled spectra. 相似文献
64.
65.
Patrik Andersson Bernard Gsell Beat Wipf Hans Senn Gottfried Otting 《Journal of biomolecular NMR》1998,11(3):279-288
An HMQC experiment is proposed, dubbed FHMQC, where water flip-back is achieved by a single water-selective pulse preceding the basic HMQC pulse sequence. The scheme is demonstrated with a 15N, 1H-HMQC spectrum of uniformly 15N/2H-labelled S. aureus DNA gyrase B with a molecular weight of 45 kDa for the unlabelled protein. The sensitivity of the experiment is improved compared to that of an FHSQC spectrum. It is further shown that the original FHSQC experiment can be shortened by the use of bipolar gradients. Relaxation times of different 15N magnetizations and coherences were measured. The new FHMQC scheme is implemented in 3D NOESY-15N-HMQC and 3D15 N-HMQC-NOESY-15N-HMQC pulse sequences which are demonstrated with a 24 kDa fragment of uniformly 15N/13C/2H-labelled S. aureus DNA gyrase B. 相似文献
66.
Markus Düchler Fritz Schmoll Franz Pfneisl Gottfried Brem Karl Schellander 《Biology of the cell / under the auspices of the European Cell Biology Organization》1998,90(2):199-205
We have established three independent ovine mammary epithelial cell lines which arose from primary cultures of ovine mammary epithelial cells by spontaneous immortalization. One of them, OMEC II, was characterised in greater detail. The cells grow rapidly on plastic dishes in medium containing 10% FCS without any requirement for additional growth factors or hormones. Immunofluorescence staining of this cell line showed expression of cytokeratin (46 kDa) and ZO-1, a tight-junction associated protein, but negative immunostaining for an anti-vimentin antibody. In confluent cell monolayers ‘domes’ became visible indicating the development of a polarised phenotype and the ability of directed secretion. When grown in collagen gels typical ducts with end-buds were observed. Treatment with lactogenic hormones increased the frequency of dome formation, but no expression of β-lactoglobulin was found. To our knowledge this is the first report on an ovine mammary epithelial cell line. 相似文献
67.
68.
Katrin Spiesberger Florian Paulfranz Anton Egger Judith Reiser Claus Vogl Judith Rudolf-Scholik Corina Mayrhofer Ludger Grosse-Hovest Gottfried Brem 《PloS one》2015,10(10)
Background
30 years ago, the potential of bispecific antibodies to engage cytotoxic T cells for the lysis of cancer cells was discovered. Today a variety of bispecific antibodies against diverse cell surface structures have been developed, the majority of them produced in mammalian cell culture systems. Beside the r28M, described here, no such bispecific antibody is known to be expressed by transgenic livestock, although various biologicals for medical needs are already harvested—mostly from the milk—of these transgenics. In this study we investigated the large-scale purification and biological activity of the bispecific antibody r28M, expressed in the blood of transgenic cattle. This tandem single-chain variable fragment antibody is designed to target human CD28 and the melanoma/glioblastoma-associated cell surface chondroitin sulfate proteoglycan 4 (CSPG4).Results
With the described optimized purification protocol an average yield of 30 mg enriched r28M fraction out of 2 liters bovine plasma could be obtained. Separation of this enriched fraction by size exclusion chromatography into monomers, dimers and aggregates and further testing regarding the biological activity revealed the monomer fraction as being the most appropriate one to continue working with. The detailed characterization of the antibody’s activity confirmed its high specificity to induce the killing of CSPG4 positive cells. In addition, first insights into tumor cell death pathways mediated by r28M-activated peripheral blood mononuclear cells were gained. In consideration of possible applications in vivo we also tested the effect of the addition of different excipients to r28M.Conclusion
Summing up, we managed to purify monomeric r28M from bovine plasma in a large-scale preparation and could prove that its biological activity is unaffected and still highly specific and thus, might be applicable for the treatment of melanoma. 相似文献69.
Klaudia Schossleitner Andreas Habertheuer Richard Finsterwalder Heinz P. Friedl Sabine Rauscher Marion Gr?ger Alfred Kocher Christine Wagner Stephan N. Wagner Gottfried Fischer Marcus J. Schultz Dominik Wiedemann Peter Petzelbauer 《PloS one》2015,10(11)
Background
Despite significant advances in organ preservation, surgical techniques and perioperative care, primary graft dysfunction is a serious medical problem in transplantation medicine in general and a specific problem in patients undergoing lung transplantation. As a result, patients develop lung edema, causing reduced tissue oxygenation capacity, reduced lung compliance and increased requirements for mechanical ventilatory support. Yet, there is no effective strategy available to protect the grafted organ from stress reactions induced by ischemia/reperfusion and by the surgical procedure itself.Methods
We assessed the effect of a cingulin-derived peptide, XIB13 or a random peptide in an established rat model of allogeneic lung transplantation. Donor lungs and recipients received therapeutic peptide at the time of transplantation and outcome was analyzed 100min and 28 days post grafting.Results
XIB13 improved blood oxygenation and reduced vascular leak 100min post grafting. Even after 28 days, lung edema was significantly reduced by XIB13 and lungs had reduced fibrotic or necrotic zones. Moreover, the induction of an allogeneic T cell response was delayed indicating a reduced antigen exchange between the donor and the host.Conclusions
In summary, we provide a new tool to strengthen endothelial barrier function thereby improving outcomes in lung transplantation. 相似文献70.
Ngo Thi Hai Yen Xenia Bogdanović Gottfried J. Palm Olaf Kühl Winfried Hinrichs 《Journal of biological inorganic chemistry》2010,15(2):195-201
Crystal structures of polypeptide deformylase (PDF) of Escherichia coli with nickel(II) replacing the native iron(II) have been solved with chloride and formate as metal ligands. The chloro complex
is a model for the correct protonation state of the hydrolytic hydroxo ligand and the protonated status of the Glu133 side
chain as part of the hydrolytic mechanism. The ambiguity that recently some PDFs have been identified with Zn2+ ion as the active-site centre whereas others are only active with Fe2+ (or Co2+, Ni2+) is discussed with respect to Lewis acid criteria of the metal ion and substrate activation by the CD loop. 相似文献