全文获取类型
收费全文 | 567篇 |
免费 | 38篇 |
出版年
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 24篇 |
2014年 | 30篇 |
2013年 | 26篇 |
2012年 | 39篇 |
2011年 | 30篇 |
2010年 | 10篇 |
2009年 | 8篇 |
2008年 | 25篇 |
2007年 | 32篇 |
2006年 | 26篇 |
2005年 | 35篇 |
2004年 | 19篇 |
2003年 | 20篇 |
2002年 | 25篇 |
2001年 | 11篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1978年 | 3篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 4篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1966年 | 3篇 |
排序方式: 共有605条查询结果,搜索用时 15 毫秒
91.
Sigrid C Roberts Jerry Scott Judith E Gasteier Yuqui Jiang Benjamin Brooks Armando Jardim Nicola S Carter Olle Heby Buddy Ullman 《The Journal of biological chemistry》2002,277(8):5902-5909
The polyamine biosynthetic enzyme, S-adenosylmethionine decarboxylase (ADOMETDC) has been advanced as a potential target for antiparasitic chemotherapy. To investigate the importance of this protein in a model parasite, the gene encoding ADOMETDC has been cloned and sequenced from Leishmania donovani. The Delta adometdc null mutants were created in the insect vector form of the parasite by double targeted gene replacement. The Delta adometdc strains were incapable of growth in medium without polyamines; however, auxotrophy could be rescued by spermidine but not by putrescine, spermine, or methylthioadenosine. Incubation of Delta adometdc parasites in medium lacking polyamines resulted in a drastic increase of putrescine and glutathione levels with a concomitant decrease in the amounts of spermidine and the spermidine-containing thiol trypanothione. Parasites transfected with an episomal ADOMETDC construct were created in both wild type and Delta adometdc parasites. ADOMETDC overexpression abrogated polyamine auxotrophy in the Delta adometdc L. donovani. In addition, ADOMETDC overproduction in wild type parasites alleviated the toxic effects of 5'-(((Z)-4-amino-2-butenyl)methylamino)-5'-deoxyadenosine (MDL 73811), but not pentamidine, berenil, or methylglyoxyl bis(guanylhydrazone), all inhibitors of ADOMETDC activities in vitro. The molecular, biochemical, and genetic characterization of ADOMETDC establishes that it is essential in L. donovani promastigotes and a potential target for therapeutic validation. 相似文献
92.
Olle Anderbrant Jan Lfqvist Hans-Erik Hgberg Erik Hedenstrm 《Entomologia Experimentalis et Applicata》1995,74(1):83-90
Mating disruption of the pine sawflyNeodiprion sertifer (Geoffroy) (Hymenoptera: Diprionidae) was strongly indicated by reduced male trap catches in pine plantations permeated with
the sex phermone, (2S, 3S, 7S)-diprionly acetate. The trap catch reduction was 95 to near 100% when dispensers every 10 m were used, giving a total release
of about 3 mg per hectare and day. Two mg of pheromone per cotton roll dispenser maintained low catches for the whole season
(about 2 months) without any renewal of disruption dispensers. Anerythro-mixture was as effective as the pure pheromone isomer. The effects of the experiments on population density and sex ratio
were not possible to investigate, due to a general collapse of the population, also outside experimental plots, the year after
the experiments. 相似文献
93.
Behnam Sadeghi Elham Roshandel Ali Pirsalehi Sepide Kazemi Ghazaleh Sankanian Mohammad Majidi Maryam Salimi Nasser Aghdami Hoda Sadrosadat Sarvenaz Samadi Kochaksaraei Farshid Alaeddini Olle Ringden Abbas Hajifathali 《Journal of cellular and molecular medicine》2021,25(22):10554-10564
Acute respiratory distress syndrome (ARDS) is the most common cause of death in COVID-19 patients. The cytokine storm is the main driver of the severity and magnitude of ARDS. Placenta-derived decidua stromal cells (DSCs) have a stronger immunosuppressive effect than other sources of mesenchymal stromal cells. Safety and efficacy study included 10 patients with a median age of 50 (range 14–68) years with COVID-19-induced ARDS. DSCs were administered 1–2 times at a dose of 1 × 106/kg. End points were safety and efficacy by survival, oxygenation and effects on levels of cytokines. Oxygenation levels increased from a median of 80.5% (range 69–88) to 95% (range 78–99) (p = 0.012), and pulmonary infiltrates disappeared in all patients. Levels of IL-6 decreased from a median of 69.3 (range 35.0–253.4) to 11 (range 4.0–38.3) pg/ml (p = 0.018), and CRP decreased from 69 (range 5–169) to 6 (range 2–31) mg/ml (p = 0.028). Two patients died, one of a myocardial infarction and the other of multiple organ failure, diagnosed before the DSC therapy. The other patients recovered and left the intensive care unit (ICU) within a median of 6 (range 3–12) days. DSC therapy is safe and capable of improving oxygenation, decreasing inflammatory cytokine level and clearing pulmonary infiltrates in patients with COVID-19. 相似文献
94.
Photoreceptor adaptation ensures appropriate visual responses during changing light conditions and contributes to colour constancy. We used behavioural tests to compare UV-sensitivity of budgerigars after adaptation to UV-rich and UV-poor backgrounds. In the latter case, we found lower UV-sensitivity than expected, which could be the result of photon-shot noise corrupting cone signal robustness or nonlinear background adaptation. We suggest that nonlinear adaptation may be necessary for allowing cones to discriminate UV-rich signals, such as bird plumage colours, against UV-poor natural backgrounds. 相似文献
95.
Isabel Regadas Olle Dahlberg Roshan Vaid Oanh Ho Sergey Belikov Gunjan Dixit Sebastian Deindl Jiayu Wen Mattias Mannervik 《Molecular cell》2021,81(8):1766-1780.e10
- Download : Download high-res image (197KB)
- Download : Download full-size image
96.
Extracellular-regulated protein kinase cascades are activated in response to injury in human skeletal muscle 总被引:6,自引:0,他引:6
97.
Olle Lindvall Anders Björklund Tomas Hökfelt Åke Ljungdahl 《Histochemistry and cell biology》1973,35(1):31-38
Summary The glyoxylic acid fluorescence histochemical method for the visualization of neuronal monoamines has been applied to fresh or glyoxylic acid-perfused brain tissue, sectioned with the Vibratome intrument. This technique demonstrates the central noradrenaline and dopamine neuron systems with a sensitivity and richness in details that is superior to the standard Falck-Hillarp formaldehyde method, as observed in the following three ways: First, the entire axon, including the non-terminal portions, became fluorescent; second, more extensive terminal systems were detected in certain brain regions ; third, due to the absence of diffusion, the delicate dopamine-containing fibres in e. g. the caudate nucleus and the median eminence had a distinct fluorescence. It is concluded that the glyoxylic acid method applied to Vibratome sections should be ideal for precise and detailed neuroanatomical studies on central catecholamine neuron systems. 相似文献
98.
Stimulation of ornithine decarboxylase activity and inhibition of S-adenosyl-l-methionine decarboxylase activity in leukaemic mice by methylglyoxal bis(guanylhydrazone) (Short Communication)
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Administration of methylglyoxal bis(guanylhydrazone) to leukaemic mice results in an early depression followed by a marked elevation of S-adenosyl-l-methionine decarboxylase activity. Further, there is an early prolonged increase in the activity of ornithine decarboxylase, the initial enzyme in the polyamine biosynthetic pathway. Because of the profound effects of methylglyoxal bis(guanylhydrazone) in vivo on the polyamine biosynthetic pathway, the drug can no longer be considered a specific inhibitor of spermidine synthesis. 相似文献
99.
Wolfgang Uerkvitz Olle Karlström Agnete Munch-Petersen 《Molecular & general genetics : MGG》1973,121(4):337-346
Summary A two-step mutant lacking two periplasmic enzymes, alkaline phosphatase and 5-nucleotidase, was prepared. In extracts of this strain phosphatase activities towards several 5-nucleotides could be detected. We have partially purified a dUMP phosphatase by streptomycin precipitation and DEAE-chromatography. This preparation has significant phosphatase activity towards three substrates, viz. dUMP, dTMP and UMP, but only traces of activity towards nine other tested nucleoside monophosphates. The three activities are probably due to a single enzyme, since they decrease in parallel on long time storage at 4°C and respond in parallel to stimulatory and inhibitory influences of different buffers and metal ions. The best buffer tested is glycylglycine buffer; Mg2+ is required but 25% activity can be obtained with Co2+ and Mn2+ and 6–8% activity with Fe2+ and Ni2+. Ca2+, Cu2+ or Zn2+ inhibit the phosphatase activities in the presence of Mg2+ or Co2+. The activities towards UMP and dUMP in the DEAE—chromatography eluted identically. The enzyme has the remarkably high apparent K
m of 10-2 M with all three substrates. 相似文献
100.
Aileen Berasategui Karolin Axelsson Göran Nordlander Axel Schmidt Anna‐Karin Borg‐Karlson Jonathan Gershenzon Olle Terenius Martin Kaltenpoth 《Molecular ecology》2016,25(16):4014-4031
The pine weevil (Hylobius abietis, Coleoptera: Curculionidae) is an important pest of conifer seedlings in Europe. Despite its economic importance, little is known about the composition of its gut microbial community and the role it plays in mediating the weevil's ability to utilize conifers as a food source. Here, we characterized the gut bacterial communities of different populations of H. abietis across Europe and compared them to those of other beetles that occupy similar ecological niches. We demonstrate that the microbial community of H. abietis is similar at higher taxonomic levels (family and genus) across locations in Europe, with Wolbachia as the dominant microbe, followed by Enterobacteria and Firmicutes. Despite this similarity, we observed consistent differences between countries and locations, but not sexes. Our meta‐analysis demonstrates that the gut bacterial community of the pine weevil is very similar to that of bark beetles that also exploit conifers as a food source. The Enterobacteriaceae symbionts of both host taxa are especially closely related phylogenetically. Conversely, the microbiota of H. abietis is distinct from that of closely related weevils feeding on nonconifer food sources, suggesting that the microbial community of the pine weevil is determined by the environment and may be relevant to host ecology. Furthermore, several H. abietis‐associated members of the Enterobacteriaceae family are known to contain genes involved in terpenoid degradation. As such, we hypothesize that the gut microbial community is important for the utilization of conifer seedlings as a food source, either through the detoxification of plant secondary metabolites or through the supplementation of essential nutrients. 相似文献