全文获取类型
收费全文 | 674篇 |
免费 | 89篇 |
国内免费 | 1篇 |
出版年
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2017年 | 21篇 |
2016年 | 11篇 |
2015年 | 27篇 |
2014年 | 15篇 |
2013年 | 28篇 |
2012年 | 28篇 |
2011年 | 33篇 |
2010年 | 33篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 29篇 |
2006年 | 23篇 |
2005年 | 30篇 |
2004年 | 30篇 |
2003年 | 24篇 |
2002年 | 34篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 15篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1977年 | 8篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1970年 | 4篇 |
1968年 | 3篇 |
1966年 | 5篇 |
排序方式: 共有764条查询结果,搜索用时 15 毫秒
681.
682.
683.
Alan D. Borthwick Keith Biggadike Ian L. Paternoster Jonathan A. V. Coates David J. Knight 《Bioorganic & medicinal chemistry letters》1993,3(12):2577-2580
The chiral carbocyclic nucleosides 2 and 3 were prepared from aristeromycin. The 4′-hydroxy compound 2 displays good antiviral activity against HSV-1 and HSV-2 with low toxicity. 相似文献
684.
Aminopeptidase P (AP-P; X-Pro aminopeptidase; EC 3.4.11.9) cleaves the N-terminal X-Pro bond of peptides and occurs in mammals as both cytosolic and plasma membrane forms, encoded by separate genes. In mammals, the plasma membrane AP-P can function as a kininase, but little is known about the physiological role of the cytosolic enzyme. The C. elegans genome contains a single gene encoding AP-P (W03G9.4), analysis of which predicts regions displaying high levels of amino-acid sequence homology between the predicted gene product and mammalian cytoplasmic AP-P, with the absolute conservation of key catalytic residues. The sequence of an EST (yk91g4), comprising the open reading frame of W03G9.4, confirmed the predicted genomic structure of the gene and the prediction that W03G9.4 codes for a nonsecreted protein with a molecular mass of 68 kDa. Nematodes transformed with a promoter reporter construct, W03G9.4:GFP, showed high levels of fluorescence in the intestine of larvae and adult hermaphrodites, indicating that the intestine is a major site of W03G9.4 expression. yk91g4 tagged with a hexahistidine and DLYDDDDK peptide epitope was expressed in Escherichia coli to yield, after affinity purification, a recombinant protein with a molecular mass of 71 kDa. The recombinant W03G9.4 removed the N-terminal amino acid from bradykinin (RPPGFSPFR), a Caenorhabditis elegans neuropeptide (KPSFVRFamide) and Lem Trp 1 (APSGFLGVRamide), but did not display activity towards angiotensin I (NRVYIHPFHL), des-Arg bradykinin and AF1 (KNEFIRFamide). The activity towards bradykinin was inhibited by EDTA and 1, 10 phenanthroline, as expected for a metalloenzyme, and also by apstatin (IC50, 1 microM), a selective inhibitor of mammalian AP-P. A Km of 45 microM and an optimum pH of 7-8 was observed with bradykinin as the substrate. The activity of the nematode AP-P, like its mammalian counterparts, was strongly influenced by metal ions, with Co2+, Mn2+ and Zn2+ all inhibiting the hydrolysis of bradykinin. We conclude that W03G9.4 codes for a cytoplasmic AP-P with very similar enzymatic properties to those of mammalian AP-P, and we suggest that the enzyme has a physiological role in the intracellular hydrolysis of proline-containing peptides absorbed from the lumen of the intestine. 相似文献
685.
686.
Maurice J O’Kane Brendan Bunting Margaret Copeland Vivien E Coates 《BMJ (Clinical research ed.)》2008,336(7654):1174-1177
Objectives To assess the effect of self monitoring of blood glucose concentrations on glycaemic control and psychological indices in patients with newly diagnosed type 2 diabetes mellitus.Design Prospective randomised controlled trial of self monitoring versus no monitoring (control).Setting Hospital diabetes clinics.Participants 184 (111 men) people aged <70 with newly diagnosed type 2 diabetes referred to the participating diabetes clinics. Major exclusion criteria were secondary diabetes, insulin treatment, previous self monitoring of blood glucose.Interventions Participants were randomised to self monitoring or no monitoring (control) groups for one year with follow-up at three monthly intervals. Both groups underwent an identical structured core education programme. The self monitoring group received additional education on monitoring.Main outcome measures Between group differences in HbA1c, psychological indices, use of oral hypoglycaemic drugs, body mass index (BMI), and reported hypoglycaemia rates.Results 96 patients (55 men) were randomised to monitoring and 88 (56 men) to control. There were no baseline differences in mean (SD) age (57.7 (11.0) in monitoring group v 60.9 (11.5) in control group) or HbA1c (8.8 (2.1)% v 8.6 (2.3)%, respectively). Those in the monitoring group had a higher baseline BMI (34 (7) v 32 (6.2)). There were no significant differences between groups at any time point (12 months values given) in HbA1c (6.9 (0.8)% v 6.9 (1.2)%, P=0.69; 95% confidence interval for difference −0.25% to 0.38%), BMI (33.1 (6.4) v 31.8 (6.0); adjusted for baseline BMI, P=0.32), use of oral hypoglycaemic drugs, or reported incidence of hypoglycaemia. Monitoring was associated with a 6% higher score on the depression subscale of the well-being questionnaire (P=0.01).Conclusions In patients with newly diagnosed type 2 diabetes self monitoring of blood glucose concentration has no effect on glycaemic control but is associated with higher scores on a depression subscale.Trial registration ISRCTN 49814766. 相似文献
687.
Kade D. Lazenby Peter S. Coates Shawn T. ONeil Michel T. Kohl David K. Dahlgren 《Ecology and evolution》2021,11(6):2741
Human enterprise has led to large‐scale changes in landscapes and altered wildlife population distribution and abundance, necessitating efficient and effective conservation strategies for impacted species. Greater sage‐grouse (Centrocercus urophasianus; hereafter sage‐grouse) are a widespread sagebrush (Artemisia spp.) obligate species that has experienced population declines since the mid‐1900s resulting from habitat loss and expansion of anthropogenic features into sagebrush ecosystems. Habitat loss is especially evident in North Dakota, USA, on the northeastern fringe of sage‐grouse’ distribution, where a remnant population remains despite recent development of energy‐related infrastructure. Resource managers in this region have determined a need to augment sage‐grouse populations using translocation techniques that can be important management tools for countering species decline from range contraction. Although translocations are a common tool for wildlife management, very little research has evaluated habitat following translocation, to track individual behaviors such as habitat selection and fidelity to the release site, which can help inform habitat requirements to guide selection of future release sites. We provide an example where locations from previously released radio‐marked sage‐grouse are used in a resource selection function framework to evaluate habitat selection following translocation and identify areas of seasonal habitat to inform habitat management and potential restoration needs. We also evaluated possible changes in seasonal habitat since the late 1980s using spatial data provided by the Rangeland Analysis Platform coupled with resource selection modeling results. Our results serve as critical baseline information for habitat used by translocated individuals across life stages in this study area, and will inform future evaluations of population performance and potential for long‐term recovery. 相似文献
688.
A Phillips M A Wainberg R Coates M Klein A Rachlis S Read F Shepherd H Vellend S Walmsley P Halloran et al. 《CMAJ》1989,140(12):1456-1460
Eight patients with AIDS (acquired immune deficiency syndrome) but free of life-threatening infection were treated with the immunosuppressive drug cyclosporine for a mean of 53.9 days. The serum cyclosporine levels were maintained in the desired therapeutic range. All eight patients experienced severe toxic symptoms, which necessitated discontinuation of cyclosporine therapy in six. The serum levels of creatinine, urea and potassium rose during treatment and fell after therapy was stopped. The total leukocyte count, hemoglobin level, platelet count, total T-cell count, and T4- and T8-cell counts all fell markedly during treatment. The total leukocyte count, platelet count, and T4- and T8-cell counts rose after therapy was stopped, but the hemoglobin level remained low. No patient experienced resolution of symptoms during therapy, and the condition of all patients improved after treatment was stopped. The results of this pilot study indicate that cyclosporine does not alleviate, and may worsen, the symptoms and laboratory findings in patients with AIDS. 相似文献
689.
690.
Climate change poses an unprecedented threat to biodiversity worldwide. Consequently, unrecognised taxa may not receive adequate conservation attention to survive. We used molecular and morphological data to address the challenge of species delimitation within the genus Schilbe. The presence or absence of an adipose fin and distribution based on east-flowing, conceivably faster-flowing, or west-flowing, probably more slow-flowing, river systems were considered. Distinctive geographic patterns in genetic variation within southern, eastern, and western African populations were revealed. Particularly, the South African population is distinct from those of Namibia, Botswana and Nigeria. No individuals with rudimentary adipose fins were found at any locality, but specimens from three localities either had or did not have adipose fins. These mixed occurrences are suspected to be a result of human interventions, and that the presence of rudimentary adipose fins in the east African species could be an adaptive feature that serves to stabilise these fish in faster currents. In addition, the genetic divergence observed among African silver catfish from geographically isolated river systems is conceivably the result of micro-evolutionary adaptive responses to different environmental conditions. Collectively, these results distinguish S. depressirostris from S. intermedius. 相似文献