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   265篇
  免费   21篇
  2023年   2篇
  2022年   3篇
  2021年   11篇
  2020年   8篇
  2019年   10篇
  2018年   8篇
  2017年   5篇
  2016年   11篇
  2015年   14篇
  2014年   20篇
  2013年   29篇
  2012年   31篇
  2011年   30篇
  2010年   14篇
  2009年   17篇
  2008年   14篇
  2007年   10篇
  2006年   10篇
  2005年   5篇
  2004年   8篇
  2003年   7篇
  2002年   2篇
  2001年   2篇
  2000年   1篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1994年   1篇
  1991年   1篇
  1990年   1篇
  1987年   2篇
  1985年   1篇
  1984年   3篇
  1983年   1篇
  1974年   1篇
排序方式: 共有286条查询结果,搜索用时 780 毫秒
261.
Plant Cell, Tissue and Organ Culture (PCTOC) - Several references in the initial online publication were incorrect. The original article has been corrected.  相似文献   
262.

Rationale

Given that the diagnosis of chronic obstructive pulmonary disease (COPD) relies on demonstrating airflow limitation by spirometry, which is known to be poorly sensitive to early disease, and to regional differences in emphysema, we sought to evaluate individual lobar contributions to global spirometric measures.

Methods

Subjects with COPD were compared with smokers without airflow obstruction, and non-smokers. Emphysema (% low attenuation area, LAAinsp<−950 HU, at end-inspiration) and gas trapping (%LAAexp<−856 HU at end-expiration) on CT were quantified using density mask analyses for the whole lung and for individual lobes, and distribution across lobes and strength of correlation with spirometry were compared.

Results

The right middle lobe had the highest %LAAinsp<−950 HU in smokers and controls, and the highest %LAAexp<−856 HU in all three groups. While RML contributed to emphysema and gas trapping disproportionately to its relatively small size, it also showed the least correlation with spirometry. There was no change in correlation of whole lung CT metrics with spirometry when the middle lobe was excluded from analyses. Similarly, RML had the highest %LAAexp<−856 HU while having the least correlation with spirometry.

Conclusions

Because of the right middle lobe’s disproportionate contribution to CT-based emphysema measurements, and low contribution to spirometry, longitudinal studies of emphysema progression may benefit from independent analysis of the middle lobe in whole lung quantitative CT assessments. Our findings may also have implications for heterogeneity assessments and target lobe selection for lung volume reduction.

Clinical Trial Registration

ClinicalTrials.gov NCT00608764  相似文献   
263.
Recent shift in trends of agricultural practices from application of synthetic fertilizers and pesticides to organic farming has brought into focus the use of microorganisms that carryout analogous function. Trichoderma spp. is one of the most popular genera of fungi commercially available as a plant growth promoting fungus (PGPF) and biological control agent. Exploitation of the diverse nature of secondary metabolites produced by different species of Trichoderma augments their extensive utility in agriculture and related industries. As a result, Trichoderma has achieved significant success as a powerful biocontrol agent at global level. The endorsement of Trichoderma spp. by scientific community is based on the understanding of its mechanisms of action against a large set of fungal, bacterial and in certain cases viral infections. However, it is still an agnostic view that there could be any single major mode of operation, although it is argued that all mechanisms operate simultaneously in a synchronized fashion. The central idea behind this review article is to emphasize the potentiality of applications of target specific secondary metabolites of Trichoderma for controlling phytopathogens as a substitute of commercially available whole organism formulations. With the aim to this point, we have compiled an inclusive list of secondary metabolites produced by different species of Trichoderma and their applications in diverse areas with the major emphasis on agriculture. Outlining the importance and diverse activities of secondary metabolites of Trichoderma besides its relevance to agriculture would generate greater understanding of their other important and beneficial applications apart from target specific biopesticides.  相似文献   
264.
Buccal patches for the delivery of atenolol using sodium alginate with various hydrophilic polymers like carbopol 934 P, sodium carboxymethyl cellulose, and hydroxypropyl methylcellulose in various proportions and combinations were fabricated by solvent casting technique. Various physicomechanical parameters like weight variation, thickness, folding endurance, drug content, moisture content, moisture absorption, and various ex vivo mucoadhesion parameters like mucoadhesive strength, force of adhesion, and bond strength were evaluated. An in vitro drug release study was designed, and it was carried out using commercial semipermeable membrane. All these fabricated patches were sustained for 24 h and obeyed first-order release kinetics. Ex vivo drug permeation study was also performed using porcine buccal mucosa, and various drug permeation parameters like flux and lag time were determined.  相似文献   
265.
In recent years, there has been a growing interest in the cluster system as an accepted form of supercomputing, due to its high performance at an affordable cost. This paper attempts to elaborate performance analysis of Myrinet-based cluster. The communication performance and effect of background load on parallel applications were analyzed. For point-to-point communication, it was found that an extension to the Hockney's model was required to estimate the performance. The proposed model suggested that there should be two ranges to be used for the performance metrics to cope with the cache effect. Moreover, based on the extension of the point-to-point communication model, the Xu and Hwang's model for collective communication performance was also extended. Results showed that our models can make better estimation of the communication performance than the previous models. Finally, the interference of other user processes to the cluster system is evaluated by using synthetic background load generation programs.  相似文献   
266.
Grewia nervosa is a herbal plant used in traditional medicine for different purposes. Bioassay‐guided chemical fractionation of G. nervosa roots resulted in an identification of two known and one new compound, namely microgrewiapine A, homomicrogrewiapine, and N‐methylmicrocosamine, respectively. Their structures were determined using combination of LC/HR‐MS, 1H‐NMR, and IR spectral analyses and followed by comparison with those reported in the literature. The problematic separation of these alkaloids on traditional column chromatography (Silica gel, Octadecyl silane, Sephadex) was resolved by using HPLC. Structurally similar compounds from the piperidine family have been characterized by using HR‐MS analysis in combination with NMR data of crude samples. The major constituent i.e. N‐methylmicrocosamine isolated from the butanol fraction of methanol root extract (MRE) was found to possess the dose dependent α‐glucosidase inhibition activity with an IC50 value of 53.40 μm . Furthermore, N‐methylmicrocosamine showed maximum α‐glucosidase inhibition of 97.48 ± 0.7% at 107.5 μm , which is approximately 1.3 × 103 fold higher than the activity shown by acarbose (97.72% inhibition at 61.95 mm ), a standard anti‐diabetic drug available commercially. This work also reports the in vitro α‐glucosidase inhibitory activity of the major alkaloids isolated from G. nervosa for the first time.  相似文献   
267.
The first microsatellite-based linkage map for Vitis aestivalis was constructed using 183 progeny from the crosses of V. aestivalis-derived “Norton” and V. vinifera “Cabernet Sauvignon”. A total of 1157 simple sequence repeat (SSR) markers were tested, 859 were amplified via PCR and 413 were polymorphic for at least one parent. The map for Norton consisted of 376 markers and covered 1496.6 centimorgan (cM) on 19 chromosomes. The consensus map consisted of 411 markers on 19 linkage groups with a total distance of 1678.6 cM. Although isozyme and SSR marker analyses in 1993 and 2009 provided preliminary evidence that Norton and Cynthiana grapes are genetically identical, only five banding patterns and four microsatellite loci were reported. This study characterized the relationship between these two cultivars using 185 microsatellites spanning 19 linkage groups for a genome-wide analysis. Four accessions of Norton and three accessions of Cynthiana were used; capillary electrophoresis results revealed Norton and Cynthiana to be identical at all selected loci.  相似文献   
268.
Cell lines resistant to Fusarium oxysporum f. sp. Ciceri crude culture filtrate have been selected In Cicer arietinum cv C235. Phenol content and the activities of tyrosine ammonia lyase (TAL), phenylalanine ammonia lyase (PAL) and ß-1, 3-glucanase were Increased by the elicitor In callus cultures of Fusarium susceptible cultlvar C235, resistant cultlvar WR315 and a stable Fusarium resistant cell clone FC-3. The Increase In phenols and glucanase activity, was more In selected cell line than In ev C235 and ev WR315, while the increase In activities of TAL and PAL showed reverse correlation.  相似文献   
269.
270.
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