首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   286篇
  免费   21篇
  2023年   3篇
  2021年   3篇
  2020年   3篇
  2019年   4篇
  2018年   4篇
  2017年   7篇
  2016年   6篇
  2015年   11篇
  2014年   14篇
  2013年   14篇
  2012年   22篇
  2011年   20篇
  2010年   10篇
  2009年   8篇
  2008年   13篇
  2007年   8篇
  2006年   9篇
  2005年   10篇
  2004年   8篇
  2003年   4篇
  2002年   10篇
  2001年   6篇
  2000年   5篇
  1999年   9篇
  1998年   3篇
  1997年   2篇
  1994年   2篇
  1993年   3篇
  1992年   6篇
  1991年   4篇
  1990年   5篇
  1989年   4篇
  1988年   5篇
  1987年   3篇
  1986年   4篇
  1985年   7篇
  1984年   3篇
  1983年   2篇
  1982年   5篇
  1981年   3篇
  1979年   8篇
  1978年   2篇
  1977年   4篇
  1976年   2篇
  1975年   2篇
  1972年   3篇
  1971年   2篇
  1969年   3篇
  1966年   1篇
  1964年   1篇
排序方式: 共有307条查询结果,搜索用时 31 毫秒
81.
82.
We investigated the extent of poleward shifts in the distribution range of Agonum viridicupreum due to climate change in the western Palaearctic. Species' records were obtained from extensive literature sources as well as from collections, and consistent amateur entomologists' recordings. Within the general geographic range of the species, we analyzed in detail two parts of both, the northern and southern distribution range boundaries: (1 and 2) north-western Germany (leading or high-latitude edge), (3) Israel and (4) southern Italy (rear or low-latitude edge). Temporal changes in the occurrence data of the species indicated a northward shift of the leading edge of a minimum of 100 km within the last 50 to 100 years. In contrast, according to the data gathered, the rear edge has not changed during the last decades. Further studies are needed in order to fully understand the underlying mechanisms of the different behaviour of leading and rear range edges of Agonum viridicupreum in the current context of global change. Despite our incomplete understanding, chronosequences of the occurrence of the given species have the potential to optimize climate niche modelling to predict trends in the distribution range in the future.  相似文献   
83.
ObjectiveTo compare Iiraglutide versus common antihyperglycemic treatments in reducing hemoglobin A1c (A1C) values across multiple levels of baseline glycemic control and in reaching glycemic targets.MethodsPooled patient data from 7 phase 3, multinational, randomized controlled trials in patients with type 2 diabetes were stratified by baseline A1C values into 5 categories: ≤ 7.5%, > 7.5% to 8.0%, > 8.0% to 8.5%, > 8.5% to 9.0%, and > 9.0%. The changes in A1C from baseline to week 26 of treatment and patient proportions reaching A1C targets of < 7.0% and ≤ 6.5% were compared between liraglutide (1.8 mg daily) and sitagliptin, glimepiride, rosiglitazone, exenatide, and insulin glargine across all baseline A1C categories.ResultsIrrespective of treatment, reductions in A1C levels were generally greater in groups with higher baseline A1C values. After 26 weeks of treatment, liraglutide produced the greatest reductions in A1C values across all baseline categories, ranging from 0.7% to 1.8% (baseline A1C categories ≤ 7.5% to > 9.0%, respectively), followed by insulin glargine (0.3% to 1.5%) and then by glimepiride (0.4% to 1.3%). Generally, larger percentages of patients achieved the A1C target of ≤ 6.5% with liraglutide therapy across all baseline categories (from 62% of patients with A1C values ≤ 7.5% to 10% of patients with A1C values > 9.0%) in comparison with other treatments (ranging from 49% to 0% of patients, respectively). Similarly, greater proportions of patients also reached the A1C target of < 7.0% with liraglutide therapy across all baseline categories (from 83% of patients with A1C values ≤ 7.5% to 25% of patients with A1C values > 9.0%) versus comparators (from 74% to 5% of patients, respectively).ConclusionAcross a wide spectrum of baseline A1C categories, liraglutide is an efficacious treatment option for patients with type 2 diabetes. (Endocr Pract. 2011;17: 906-913)  相似文献   
84.
The aim of this study was to investigate the effects of Raloxifene (Ral) on degeneration-related changes in osteoarthritis (OA)-like chondrocytes using two- and three-dimensional models. Five-azacytidine (Aza-C) was used to induce OA-like alterations in rat articular chondrocytes and the model was verified at molecular and macrolevels. Chondrocytes were treated with Ral (1, 5 and 10 μM) for 10 days. Caspase-3 activity, gene expressions of aggrecan, collagen II, alkaline phosphatase (ALP), collagen X, matrix metalloproteinases (MMP-13, MMP-3 and MMP-2), and MMP-13, MMP-3 and MMP-2 protein expressions were studied in two-dimensional model. Matrix deposition and mechanical properties of agarose-chondrocyte discs were evaluated in three-dimensional model. One μM Ral reduced expression of OA-related genes, decreased apoptosis, and MMP-13 and MMP-3 protein expressions. It also increased aggrecan and collagen II gene expressions relative to untreated OA-like chondrocytes. In three-dimensional model, 1 μM Ral treatment resulted in increased collagen deposition and improved mechanical properties, although a significant increase for sGAG was not observed. In summation, 1 μM Ral improved matrix-related activities, whereas dose increment reversed these effects except ALP gene expression and sGAG deposition. These results provide evidence that low-dose Ral has the potential to cease or reduce the matrix degeneration in OA.  相似文献   
85.
Probiotics have decreased the counts of salivary mutans streptococci (MS) in clinical studies. The aim of this study was to compare the effects of Lactobacillus reuteri PTA 5289 and L. paracasei DSMZ16671 on the adhesion of a reference strain and a clinical isolate of Streptococcus mutans and on the counts of MS in a biofilm. The adhesion of S. mutans Ingbritt and the clinical isolate S. mutans 2366 to a smooth glass surface and saliva-coated hydroxyapatite (SHA) were studied in the presence of and without the lactobacilli. A three-species biofilm formed on saliva-coated hydroxyapatite discs was used in the biofilm experiments. The lactobacilli did not affect adhesion to the glass surface but interfered with binding to SHA. No effects of the lactobacilli were detected on the MS levels in the three-species biofilms. The results of the SHA binding experiments best reflected the results of the existing clinical studies.  相似文献   
86.
87.
Gliadin polymorphism in 19 landrace populations of Turkish cultivated emmer wheat [Triticum turgidum L. ssp. dicoccon (Schrank) Thell.] was assessed using the aluminum lactic acid-polyacrylamide gel electrophoresis (A-PAGE) technique. Being a source of useful genes, landraces of wheat represent one of the most important genetic resources available to breeders for present and future genetic improvement of wheat. This is the first genetic characterization of these 19 Turkish emmer wheat landrace populations collected from their main cultivation areas. Considerably high amounts of variation were detected within and among the populations. A total of 27 alleles (n a) were identified among all analyzed populations, 10 of them being unique to populations?C, D, H, K, L, M, and N. The highest allele number (n a?=?7) was observed in populations?A and L, whereas the lowest number of alleles (n a?=?3) was observed in populations?F, G, and U. The mean number of effective alleles (n ae) was 12.33, and the mean values of gene diversity, genetic differentiation, and gene flow between populations were H e?=?0.92, F ST?=?0.296, and N m ?=?0.60, respectively. Certain gliadins closely linked to dough quality, such as ??-45 and ??-35, were found in 13 and 18 of the populations, respectively. According to Pearson??s correlation coefficient values, gene diversity estimates had strong positive correlation (r P?=?0.510; p?=?0.026 at <0.05%) with latitude. The rest of the genetic data (n a and n ae) obtained in the present study showed no correlation with geographic (altitude, latitude, and longitude) or climatic factors (temperature and annual rainfall). Principal component analysis was performed to explain spatial genetic variation, revealing 90.044% of total genetic variation in three components. Results obtained from this study can effectively be used in developing more efficient breeding programs to improve wheat genotypes, and to direct genetic resource conservation studies.  相似文献   
88.
In many respects, hydrogen is an ideal biofuel. However, practical, sustainable means of its production are presently lacking. Here we review recent efforts to apply the capacity of photosynthetic bacteria to capture solar energy and use it to drive the nearly complete conversion of substrates to hydrogen and carbon dioxide. This process, called photofermentation, has the potential capacity to use a variety of feedstocks, including the effluents of dark fermentations, leading to the development of various configurations of two-stage systems, or various industrial and agricultural waste streams rich in sugars or organic acids. The metabolic and enzymatic properties of this system are presented and the possible waste streams that might be successfully used are discussed. Recently, various immobilized systems have been developed and their advantages and disadvantages are examined.  相似文献   
89.
90.
We studied a data set of structurally similar interfaces that bind to proteins with different binding-site structures and different functions. Our multipartner protein interface clusters enable us to address questions like: What makes a given site bind different proteins? How similar/different are the interactions? And, what drives the apparently less-specific association? We find that proteins with common binding-site motifs preferentially use conserved interactions at similar interface locations, despite the different partners. Helices are major vehicles for binding different partners, allowing alternate ways to achieve favorable association. The binding sites are characterized by imperfect packing, planar architectures, bridging water molecules, and, on average, smaller size. Interestingly, analysis of the connectivity of these proteins illustrates that they have more interactions with other proteins. These findings are important in predicting "date hubs," if we assume that "date hubs" are shared proteins with binding sites capable of transient binding to multipartners, linking higher-order networks.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号