全文获取类型
收费全文 | 350篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
375篇 |
出版年
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 22篇 |
2013年 | 22篇 |
2012年 | 19篇 |
2011年 | 18篇 |
2010年 | 15篇 |
2009年 | 13篇 |
2008年 | 15篇 |
2007年 | 25篇 |
2006年 | 16篇 |
2005年 | 7篇 |
2004年 | 16篇 |
2003年 | 17篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有375条查询结果,搜索用时 31 毫秒
81.
Jarkko Hantula Anne Kurki Pertti Vuoriranta Dennis Henry Bamford 《Applied microbiology and biotechnology》1991,34(4):551-555
Summary Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of total cellular proteins has been used to classify bacterial strains of the dispersed phase of activated sludge. The dominant bacterial populations are shown to be in dynamic change at species level while higher order taxons are more stable. 相似文献
82.
Hänninen ML Haajanen H Pummi T Wermundsen K Katila ML Sarkkinen H Miettinen I Rautelin H 《Applied and environmental microbiology》2003,69(3):1391-1396
Waterborne outbreaks associated with contamination of drinking water by Campylobacter jejuni are rather common in the Nordic countries Sweden, Norway, and Finland, where in sparsely populated districts groundwater is commonly used without disinfection. Campylobacters, Escherichia coli, or other coliforms have rarely been detected in potential sources. We studied three waterborne outbreaks in Finland caused by C. jejuni and used sample volumes of 4,000 to 20,000 ml for analysis of campylobacters and sample volumes of 1 to 5,000 ml for analysis of coliforms and E. coli, depending on the sampling site. Multiple samples obtained from possible sources (water distribution systems and environmental water sources) and the use of large sample volumes (several liters) increased the chance of detecting the pathogen C. jejuni in water. Filtration of a large volume (1,000 to 2,000 ml) also increased the rate of detection of coliforms and E. coli. To confirm the association between drinking water contamination and illness, a combination of Penner serotyping and pulsed-field gel electrophoresis (digestion with SmaI and KpnI) was found to be useful. This combination reliably verified similarity or dissimilarity of C. jejuni isolates from patient samples, from drinking water, and from other environmental sources, thus confirming the likely reservoir of an outbreak. 相似文献
83.
Correlation between serum levels of some cholesterol precursors and activity of HMG-CoA reductase in human liver 总被引:9,自引:0,他引:9
I Bj?rkhem T Miettinen E Reihnér S Ewerth B Angelin K Einarsson 《Journal of lipid research》1987,28(10):1137-1143
The possibility that the serum concentrations of various cholesterol precursors may reflect the activity of the hepatic HMG-CoA reductase was investigated in humans under different conditions. The serum levels of squalene, free and esterified lanosterol, (4 alpha, 4 beta, 14 alpha-trimethyl-5 alpha-cholest-8, 24-dien-3 beta-ol), two dimethylsterols (4 alpha, 4 beta-dimethyl-5 beta-cholest-8-en-3 beta-ol and 4 alpha, 4 beta-dimethyl-5 alpha-cholest-8, 24-dien-3 beta-ol), two methostenols (4 alpha-methyl-5 alpha-cholest-7-en-3 beta-ol and 4 alpha-methyl-5 alpha-cholest-8-en-3 beta-ol), two lathosterols (5 alpha-cholest-7-en-3 beta-ol and 5 alpha-cholest-8-en-3 beta-ol) and desmosterol (cholest-5, 24-dien-3 beta-ol) were measured in untreated patients (n = 7) and patients treated with cholestyramine (QuestranR, 8 g twice daily for 2-3 weeks, n = 5) or chenodeoxycholic acid (15 mg/kg body weight daily for 3-4 weeks, n = 8) prior to elective cholecystectomy. The activity of the hepatic microsomal HMG-CoA reductase was measured in liver biopsies taken in connection with the operation.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
84.
Vierimaa H Ronkainen J Ruskoaho H Vuolteenaho O 《American journal of physiology. Heart and circulatory physiology》2006,291(3):H1360-H1370
The aim was to find out the effects of endothelin-1 (ET-1) in salmon (Salmo salar) cardiac contractile and endocrine function and its possible interaction with beta-adrenergic regulation. We found that ET-1 has a positive inotropic effect in salmon heart. ET-1 (30 nM) increased the contraction amplitude 17+/-4.7% compared with the basal level. beta-Adrenergic activation (isoprenaline, 100 nM) increased contraction amplitude 30+/-13.1%, but it did not affect the contractile response to ET-1. ET-1 (10 nM) stimulated the secretion of salmon cardiac natriuretic peptide (sCP) from isolated salmon ventricle (3.3+/-0.14-fold compared with control) but did not have any effect on ventricular sCP mRNA. Isoprenaline alone (0.1-1,000 nM) did not stimulate sCP release, but ET-1 (10 nM) together with isoprenaline (0.1 nM) caused a significantly greater increase of sCP release than ET-1 alone (5.4+/-0.07 vs. 3.3+/-0.14 times increase compared with control). The effects on the contractile and secretory function could be inhibited by a selective ETA-receptor antagonist BQ-610 (1 microM), whereas ETB-receptor blockage (by 100 nM BQ-788) enhanced the secretory response. Thus ET-1 is a phylogenetically conserved regulator of cardiac function, which has synergistic action with beta-adrenergic stimulation. The modulatory effects of ET-1 may therefore be especially important in situations with high beta-adrenergic tone. 相似文献
85.
Jarho EM Venäläinen JI Juntunen J Yli-Kokko AL Vepsäläinen J Christiaans JA Forsberg MM Järvinen T Männistö PT Wallén EA 《Bioorganic & medicinal chemistry letters》2006,16(21):5590-5593
A series of ionizable prolyl oligopeptidase inhibitors were developed through the introduction of a pyridyl group to the P3 position of the prolyl oligopeptidase inhibitor structure. The study was performed on previously developed prolyl oligopeptidase inhibitors with proline mimetics at the P2 position. The 3-pyridyl group resulted in equipotent compounds as compared to the parent compounds. It was shown that the pyridyl group improves water solubility and, in combination with a 5(R)-tert-butyl-l-prolyl group at the P2 position, good lipophilicity can be achieved. 相似文献
86.
87.
Maria Kahlert Raino-Lars Albert Eeva-Leena Anttila Roland Bengtsson Christian Bigler Tiina Eskola Veronika Gälman Steffi Gottschalk Eva Herlitz Amelie Jarlman Jurate Kasperoviciene Mikołaj Kokociński Helen Luup Juha Miettinen Ieva Paunksnyte Kai Piirsoo Isabel Quintana Janne Raunio Bernt Sandell Heikki Simola Irene Sundberg Sirje Vilbaste Jan Weckström 《Journal of applied phycology》2009,21(4):471-482
The goal of this study was a harmonization of diatom identification and counting among diatomists from the Scandinavian and
Baltic countries to improve the comparison of diatom studies in this geographical area. An analysis of the results of 25 diatomists
following the European standard EN 14407 during an intercalibration exercise showed that a high similarity was achieved by
harmonization and not because of a long experience with diatoms. Sources of error were wrong calibration scales, overlooking
of small taxa, especially small Navicula s.l., misidentifications (Eunotia rhomboidea was mistaken for Eunotia incisa) and unclear separation between certain taxa in the identification literature. The latter was discussed during a workshop
with focus on the Achnanthes minutissima group, the separation of Fragilaria capucina var. gracilis from F. capucina var. rumpens, and Nitzschia palea var. palea from N. palea var. debilis. The exercise showed also that the Swedish standard diatom method tested here worked fine with acceptable error for the indices
IPS (Indice de Polluo-sensibilité Spécifique) and ACID (ACidity Index for Diatoms) when diatomists with a low similarity (Bray–Curtis
<60%) with the auditor in at least one of the samples are excluded. 相似文献
88.
Johan Reinert Vikan Bård Gunnar Stokke Jarkko Rutila Esa Huhta Arne Moksnes Eivin Røskaft 《Evolutionary ecology》2010,24(5):1141-1157
The brood parasitic common cuckoo Cuculus canorus has a history of coevolution that involves numerous passerine hosts, but today only a subset is known to be regularly parasitised
in any area. In some hosts, there is significant variation in the occurrence of parasitism between populations, but still
individuals in non-parasitised populations show strong antiparasite defences. In the present study we compared the strength
of egg rejection of four distant Fennoscandian brambling Fringilla montifringilla populations experiencing different levels of cuckoo parasitism (0–6%). Egg rejection ability was in general very well developed
and we did not find any population differences in the relationship between egg rejection probability and similarity between
host and experimental parasitic eggs. Furthermore, bramblings very rarely made errors in rejection, indicating that selection
against rejection behaviour is likely to be very weak. The brambling-cuckoo system therefore differs from other well studied
systems which are characterised by pronounced spatial and temporal variation in the host’s level of defence. This result is
unlikely to reflect independent replication of the same evolutionary trajectory because the weak breeding site tenacity of
bramblings should result in an extreme amount of gene flow within the distribution area and thus strongly impede localised
responses to selection. Instead, lack of geographic variation has more likely arisen because bramblings respond to selection
as one evolutionary unit, and because the average parasitism pressures have been high enough in the past to cause regional
fixation of rejection alleles and evolution of clutch characteristics that facilitate cost free egg recognition. 相似文献
89.
Jarkko Rautio Jukka Leppänen Marko Lehtonen Krista Laine Mikko Koskinen Jarmo Pystynen Jouko Savolainen Mikko Sairanen 《Bioorganic & medicinal chemistry letters》2010,20(8):2614-2616
Compound 1 is an investigational, nanomolar inhibitor of catechol-O-methyltransferase (COMT) that suffers from poor oral bioavailability, most probably due to its low lipophilicity throughout most of the gastrointestinal tract and, to a lesser extent, its rapid systemic clearance. Several lipophilic esters were designed as prodrugs and synthesized in an attempt to optimize presystemic drug absorption. A modest twofold increase in 6-h exposure of 1 was observed with two prodrugs, compared to that of 1, after oral treatment in rats. 相似文献
90.
Juuti M van Veen B Peiponen KE Ketolainen J Kalima V Silvennoinen R Pakkanen TT 《AAPS PharmSciTech》2006,7(1):E43-E48
The purpose of this study was to detect local gloss and surface structure changes of sodium chloride tablets. The changes
in surface structure were reflected by gloss variation, which was measured using a diffractive optical element-based gloss-meter
(DOG). By scanning a surface area, we constructed a 2-dimensional gloss map that characterized the tablet’s surface structure.
The gloss variation results were compared with scanning electron microscopy (SEM) images and average surface roughness values
that were measured by conventional diamond stylus profilometry. The profilometry data showed a decrease in tablet surface
roughness as a function of compression force. In general, a smoother surface contributes to higher average gloss values. The
average gloss values for this material, in contrast, showed a decrease as a function of the compression force. The sequence
of particle fragmentation and deformation together with crack formation in sodium chloride particles resulted in a loss of
gloss for single sodium chloride particles at the tablet surfaces, which could be detected by the DOG. These results were
supported by the SEM images. The results show that detailed information regarding tablets’ surface structure changes can be
obtained by detection of local gloss variation and average gloss.
Published: January 13, 2006 相似文献