全文获取类型
收费全文 | 859篇 |
免费 | 66篇 |
出版年
2023年 | 5篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2018年 | 3篇 |
2017年 | 9篇 |
2016年 | 18篇 |
2015年 | 28篇 |
2014年 | 29篇 |
2013年 | 36篇 |
2012年 | 50篇 |
2011年 | 59篇 |
2010年 | 41篇 |
2009年 | 36篇 |
2008年 | 56篇 |
2007年 | 54篇 |
2006年 | 54篇 |
2005年 | 56篇 |
2004年 | 46篇 |
2003年 | 38篇 |
2002年 | 45篇 |
2001年 | 19篇 |
2000年 | 11篇 |
1999年 | 23篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 10篇 |
1988年 | 3篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 4篇 |
1971年 | 5篇 |
排序方式: 共有925条查询结果,搜索用时 31 毫秒
81.
Winfried Hartmeier 《Trends in biotechnology》1985,3(6):149-153
Until recently it was only practical to use immobilized systems containing single enzymes or whole cells. More complex systems providing cofactor regeneration outside living cells have now been developed; coimmobilization of enzymes, cells and organelles from different organisms promises to improve further the industrial feasibility of immobilized biocatalysts. 相似文献
82.
Behavioral and electrophysiological experiments have shown that the elongated paddlefish rostrum, with its extensive population of ampullae of Lorenzini, constitutes a passive electrosensory antenna of great sensitivity and spatial resolution. As demonstrated in juvenile paddlefish, the passive electrosense serves a novel function in feeding serving as the primary, if not exclusive sensory modality for the detection and capture of zooplanktonic prey. Ampullary receptors are sensitive to the weak electrical fields of plankton from distances up to 9 cm, and juvenile paddlefish capture plankton individually with great swimming dexterity in the absence of vision or other stimulus signals. Paddlefish also detect and avoid metal obstacles, the electrical signatures of which are a potential hindrance to their feeding and reproductive migrations. The ampullary receptors, their peripheral innervation and central targets in the dorsal octavolateral nucleus, are described. We also describe the ascending and descending neuronal circuitry of the electrosensory system in the brain based on tracer studies using dextran amines. 相似文献
83.
Schäfer C Parlesak A Eckoldt J Bode C Bode JC März W Winkler K 《Journal of lipid research》2007,48(7):1550-1558
The reduction of cardiovascular mortality associated with moderate alcohol consumption is chiefly thought to be mediated by an increase of high density lipoprotein cholesterol (HDL-CH). This study highlights additional qualitative changes of HDL that might augment this antiatherogenic effect. In 279 healthy men, alcohol and nutrient consumption were evaluated. Groups 1 (n=62), 2 (n=172), and 3 (n=45) comprised subjects with alcohol consumption of 0-5.0, 5.1-30.0, and 30.1-75 g/day, respectively. Lipid analysis was performed in nonfractionated and fractionated plasma, including subfractions HDL(2a), HDL(2b), and HDL(3). No difference in LDL-cholesterol was observed. Compared with group 1, groups 2 and 3 exhibited significant increases of HDL-CH (group 1, 44 +/- 10 mg/dl; group 2, 51 +/- 11 mg/dl; group 3, 55 +/- 11 mg/dl; mean +/- SD, P<0.0005), accompanied by enhanced lipidation of HDL (increase of the HDL(2)-CH/HDL(3)-CH ratio). Moreover, phospholipid enrichment of HDL occurred in alcohol consumers, whereas the ratios between other HDL components remained constant. Multivariate analysis revealed alcohol to have the foremost statistical influence on changes of the HDL fraction, followed by body mass index and physical activity level. The increased lipidation of HDL found in alcohol consumers might augment the antiatherogenic effect of HDL-CH increase. In addition, the phospholipid enrichment of HDL might reduce the inflammatory response of atherogenesis. 相似文献
84.
Albertini AA Clapier CR Wernimont AK Schoehn G Weissenhorn W Ruigrok RW 《Journal of structural biology》2007,158(1):129-133
In order to study the packaging of rabies virus RNA inside the viral nucleocapsid, rabies nucleoprotein was expressed in insect cells. In the cells, it binds to cellular RNA to form long, helical or short circular complexes, depending on the length of the bound RNA. The circular complexes contained from 9 up to 13 N-protomers per ring. Separation of the rings into defined size classes was impossible through regular column chromatographies or gradient centrifugation. The size classes could be separated by native polyacrylamide gel electrophoresis. A large-scale separation was achieved with a 4% native gel using a preparative electrophoresis apparatus. Crystallization trials were set up with N-RNA rings from three size classes and crystals were obtained in all cases. The best diffracting crystals, diffracting up to 6A, contained rings with 11 N-protomers plus an RNA molecule of 99 nucleotides. The diffraction limit was improved to 3.5A by air dehydration prior to flash freezing. 相似文献
85.
Marjolein Glas H. Bart van den Berg van Saparoea Stephen H. McLaughlin Winfried Roseboom Fan Liu Gregory M. Koningstein Alexander Fish Tanneke den Blaauwen Albert J. R. Heck Luitzen de Jong Wilbert Bitter Iwan J. P. de Esch Joen Luirink 《The Journal of biological chemistry》2015,290(35):21498-21509
Cell division in Escherichia coli involves a set of essential proteins that assembles at midcell to form the so-called divisome. The divisome regulates the invagination of the inner membrane, cell wall synthesis, and inward growth of the outer membrane. One of the divisome proteins, FtsQ, plays a central but enigmatic role in cell division. This protein associates with FtsB and FtsL, which, like FtsQ, are bitopic inner membrane proteins with a large periplasmic domain (denoted FtsQp, FtsBp, and FtsLp) that is indispensable for the function of each protein. Considering the vital nature and accessible location of the FtsQBL complex, it is an attractive target for protein-protein interaction inhibitors intended to block bacterial cell division. In this study, we expressed FtsQp, FtsBp, and FtsLp individually and in combination. Upon co-expression, FtsQp was co-purified with FtsBp and FtsLp from E. coli extracts as a stable trimeric complex. FtsBp was also shown to interact with FtsQp in the absence of FtsLp albeit with lower affinity. Interactions were mapped at the C terminus of the respective domains by site-specific cross-linking. The binding affinity and 1:1:1 stoichiometry of the FtsQpBpLp complex and the FtsQpBp subcomplex were determined in complementary surface plasmon resonance, analytical ultracentrifugation, and native mass spectrometry experiments. 相似文献
86.
87.
Jabari S da Silveira AB de Oliveira EC Neto SG Quint K Neuhuber W Brehmer A 《Histochemistry and cell biology》2011,135(1):47-57
One frequent chronic syndrome of Chagas’ disease is megacolon, an irreversible dilation of a colonic segment. Extensive enteric
neuron loss in the affected segment is regarded as key factor for deficient motility. Here, we assessed the quantitative balance
between cholinergic and nitrergic neurons representing the main limbs of excitatory and inhibitory colonic motor innervation,
respectively. From surgically removed megacolonic segments of four patients, each three myenteric wholemounts (from non-dilated
oral, megacolonic and non-dilated anal parts) was immunohistochemically triple-stained for choline acetyltransferase, neuronal
nitric oxide synthase (NOS) and the panneuronal human neuronal protein Hu C/D. Degenerative changes were most pronounced in
the megacolonic and anal regions, e.g. bulked, honeycomb-like ganglia with few neurons which were partly enlarged or atrophic
or vacuolated. Neuron counts from each 15 ganglia of 12 megacolonic wholemounts were compared with those of 12 age- and region-matched
controls. Extensive neuron loss, mainly in megacolonic and anal wholemounts, was obvious. In all three regions derived from
megacolonic samples, the proportion of NOS-positive neurons (control: 55%) was significantly increased: in non-dilated oral
parts to 61% (p = 0.003), in megacolonic regions to 72% (p < 0.001) and in non-dilated anal regions to 78% (p < 0.001). We suggest the chronic dilation of megacolonic specimens to be due to the preponderance of the nitrergic, inhibitory
input to the intestinal muscle. However, the observed neuronal imbalance was not restricted to the dilated regions: the non-dilated
anal parts may be innervated by ascending, cholinergic axons emerging from less affected, more anally located regions. 相似文献
88.
89.
Becker SL Sieto B Silué KD Adjossan L Koné S Hatz C Kern WV N'Goran EK Utzinger J 《PLoS neglected tropical diseases》2011,5(8):e1292
Background
Infections with Strongyloides stercoralis and other helminths represent important, yet often neglected issues in developing countries. Indeed, strongyloidiasis can be fatal, but only a few studies provide information regarding its health relevance in Africa. Moreover, clinical data on symptomatology and typical recognition patterns mainly originate from Western travel clinics.Methodology
A cross-sectional epidemiological survey was carried out in a rural part of south-central Côte d''Ivoire. Stool samples from 292 randomly selected individuals were examined for intestinal helminths, using a suite of diagnostic techniques (i.e., Kato-Katz, Baermann funnel, and Koga agar plate). Participants were interviewed with a pre-tested questionnaire and clinically examined. Multivariate logistic regression analysis was done to relate perceived morbidity and clinical findings to helminth infection status.Principal Findings
The prevalence of hookworm and S. stercoralis was 51.0% and 12.7%, respectively. Both infections were strongly associated with each other (adjusted odds ratio, 6.73; P<0.001) and higher prevalences were observed with age. S. stercoralis-infected individuals expressed self-reported morbidity considerably more often than those with hookworm infection. Clinical examination identified high prevalences of various pathologies and detected tendencies to worse health conditions in helminth-infected subjects.Conclusions/Significance
The use of multiple diagnostic tools showed that S. stercoralis and hookworm are co-endemic in rural Côte d''Ivoire and that each infection causes clinical symptoms and sequelae. Our findings are important for (re-)estimating the burden of helminth infections, and highlight the need for integrating epidemiological surveys, rigorous diagnostic approaches, and clinical assessments in the developing world. 相似文献90.