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   593篇
  免费   25篇
  2023年   8篇
  2022年   5篇
  2021年   14篇
  2020年   5篇
  2019年   7篇
  2018年   13篇
  2017年   8篇
  2016年   24篇
  2015年   24篇
  2014年   31篇
  2013年   40篇
  2012年   53篇
  2011年   51篇
  2010年   28篇
  2009年   27篇
  2008年   38篇
  2007年   27篇
  2006年   37篇
  2005年   33篇
  2004年   23篇
  2003年   18篇
  2002年   22篇
  2001年   4篇
  2000年   6篇
  1999年   3篇
  1998年   6篇
  1997年   2篇
  1996年   5篇
  1995年   9篇
  1994年   3篇
  1992年   4篇
  1991年   2篇
  1990年   3篇
  1989年   6篇
  1987年   4篇
  1986年   2篇
  1983年   1篇
  1982年   3篇
  1981年   2篇
  1980年   3篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1970年   2篇
  1967年   1篇
  1965年   1篇
排序方式: 共有618条查询结果,搜索用时 15 毫秒
11.
12.
Egyptian flower mantis Blepharopsis mendica (Order: Mantodea) is a widespread mantis species throughout the southwest Palearctic region. The ecological and geographical distribution of such interesting species is rarely known. So, through this work, habitat suitability models for its distribution through Egyptian territory were created using MaxEnt software from 90 occurrence records. One topographic (altitude) and eleven bioclimatic variables influencing the species distribution were selected to generate the models. The predicted distribution in Egypt was focused on the Delta, South Sinai, the north-eastern part of the country, and some areas in the west including Siwa Oasis. Temporal analysis between the two periods (1900–1961) and (1961–2017) show current reduction of this species distribution through Delta and its surrounding areas, may be due to urbanization. On the other hand, it increases in newly protected areas of South Sinai. Under the future climate change scenario, the MaxEnt model predicted the habitat gains for B. mendica in RCP 2.6 for 2070 and loss of habitat in RCP 8.5 for the same year. Our results can be used as a basis for conserving this species not only in Egypt, but also throughout the whole of its range, also, it show how the using of geo-information could help in studying animal ecology.  相似文献   
13.
A convenient method for the ‘one-pot’ synthesis of novel target molecule 2,7-diaryl-[1,4]-diazepan-5-ones from the respective 2,6-diaryl-piperidin-4-ones was catalyzed by NaHSO4.Al2O3 heterogeneous catalyst in dry media under microwave irradiation in solvent-free conditions. Moreover, the catalyst could be recovered and re-used up to 4 times after washing with ethyl acetate. They were evaluated for potential antibacterial activity against Staphylococcus aureus, β-Haemolytic streptococcus, Vibreo cholerae, Salmonella typhii, Escherichia coli, Klebsiella pneumonia, Pseudomonas and antifungal activity against Aspergillus flavus, Aspergillus fumigatus, Mucor, Candida albicans and Rhizopus. Structure-Activity Relationship (SAR) led to the conclusion that, of all the compounds 25–32 tested, compound 30 exerted strong in vitro antibacterial activity against S. aureus, S. typhii, and Pseudomonas and all the compounds 25–32 were less active against E. coli, whereas all the compounds 25–32 displayed potent in vitro antifungal activity against all the fungal strains used, except compound 30, which was more effectual against Mucor.  相似文献   
14.
New 3-chloro-1-hydroxy-2,6-diarylpiperidin-4-ones 18–22 were synthesized, characterized by melting point, elemental analysis, MS, FT-IR, one-dimensional NMR (1H & 13C) spectroscopic data and evaluated for their in vitro antibacterial and antifungal activities. All the newly synthesized compounds exerted a wide range of antibacterial activities against the entire tested gram-positive and gram-negative bacterial strains except Escherichia coli. Compounds 21 and 22 exerted strong antifungal activities against Aspergillus flavus, mucor and Microsporum gypsuem. In addition, compound 20 was more potent against Rhizopus.

  相似文献   
15.
Vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) exhibit hyperproliferation and overexpression of cell cycle proteins. We earlier showed that small peptide fragments of cytoplasmic domain of natriuretic receptor-C (NPR-C) attenuate vasoactive peptide-induced hyperproliferation of VSMC. The present study investigated if C-ANP4–23, a specific agonist of NPR-C, could attanuate the hyperproliferation of VSMC from SHR by inhibiting the overexpression of cell cycle proteins and examine the underlying signaling pathways contributing to this inhibition. The proliferation of VSMC was determined by [3H] thymidine incorporation and the expression of proteins was determined by Western blotting. The hyperproliferation of VSMC from SHR and overexpression of cyclin D1,cyclin A, cyclin E, cyclin-dependent kinase 2 (cdk2), phosphorylated retinoblastoma protein (pRb), Giα proteins and enhanced phosphorylation of ERK1/2 and AKT exhibited by VSMC from SHR were attenuated by C-ANP4–23 to control levels. In addition, in vivo treatment of SHR with C-ANP4–23 also attenuated the enhanced proliferation of VSMC. Furthemore, PD98059, wortmannin and pertussis toxin, the inhibitors of MAP kinase, PI3kinase and Giα proteins respectively, also attenuated the hyperproliferation of VSMC from SHR and overexpression of cell cycle proteins to control levels. These results indicate that NPR-C activation by C-ANP4–23 attenuates the enhanced levels of cell cycle proteins through the inhibition of enhanced expression of Giα proteins and enhanced activation of MAPkinase/PI3kinase and results in the attenuation of hyperproliferation of VSMC from SHR. It may be suggested that C-ANP4–23 could be used as a therapeutic agent in the treatment of vascular complications associated with hypertension, atherosclerosis and restenosis.  相似文献   
16.
Effect of long term cholesterol diet withdrawal on accelerated atherosclerosis in iliac artery of New Zealand White (NZW) rabbits has not been explored so far. Atherosclerosis was thus induced in rabbits by a combination of balloon injury and atherogenic diet (AD) (1% cholesterol and 6% peanut oil) feeding for 8 weeks (baseline) followed by chow diet (CD) feeding for 4, 8, 16, 32, 50 and 64 weeks. The plaque characterization was done using histology, real time RT-PCR and vasoreactivity studies. Significant elevation in plasma lipids with AD feeding was normalized following 16 weeks of CD feeding. However, baseline comparison showed advanced plaque features even after 8 weeks of CD period with significant elevation in intima/media thickness ratio and plaque area later showing reduction at 50 and 64 weeks CD periods. Lesion lipid accumulation and CD68 positivity was maintained till 16 weeks of CD feeding which significantly reduced from 32 to 64 weeks CD periods. Baseline comparison showed significant increase in ground substance, MMP-9 and significant decrease in α-actin and collagen content at 8 weeks CD period indicating features of unstable plaque. These features regressed up to 64 weeks of CD. Partial restoration of functional vasoconstriction and vasorelaxation was seen after 64 weeks of CD feeding. mRNA expression of MCP-1, VCAM-1, collagen type I and III, MMP-9, TIMP-1, IFN-γ, TNF-α, IL-10 and eNOS supported the above findings. The study thus reveals insights into initial plaque instability and subsequent regression on AD withdrawal in this model. These results are suggestive of an appropriate window for drug intervention for plaque stability/regression and restenosis as well as improves understanding of plaque regression phenomenon in this model.  相似文献   
17.
We report here a case of non-healing ulcer due to Trichosporon loubieri in an apparently immunocompetent female. The identity of isolate was confirmed by DNA sequencing of D1/D2 region of 26S rDNA. The minimum inhibitory concentrations of the isolate were amphotericin B—0.5 μg/ml; fluconazole—4 μg/ml; posaconazole—0.25 μg/ml; voriconazole—0.06 μg/ml. The patient was managed by extensive debridement and oral fluconazole 150 mg daily for 6 weeks. She responded to therapy. To the best of our knowledge, till date, this is the fourth report of human infection due to T. loubieri and the first of its kind in an immunocompetent host. A review of published literature on infections due to T. loubieri is also included.  相似文献   
18.
The growth of horticulture industries worldwide has generated huge quantities of fruit wastes (25%–40% of the total fruits processed). These residues are generally a good source of carbohydrates, especially cell wall polysaccharides and other functionally important bioactive molecules such as proteins, vitamins, minerals and natural antioxidants. “Apple pomace” is a left-over solid biomass with a high moisture content, obtained as a by-product during the processing of apple fruits for juice, cider or wine preparation. Owing to the high carbohydrate content, apple pomace is used as a substrate in a number of microbial processes for the production of organic acids, enzymes, single cell protein, ethanol, low alcoholic drinks and pigments. Recent research trends reveal that there is an increase in the utilization of apple pomace as a food processing residue for the extraction of value added products such as dietary fibre, protein, natural antioxidants, biopolymers, pigments and compounds with unique properties. However, the central dogma is still the stability, safety and economic feasibility of the process(s)/product(s) developed. This review is mainly focused on assessing recent research developments in extraction, isolation and characterization of bioactive molecules from apple pomace, along with their commercial utilization, in food fortification.  相似文献   
19.
The Fn14 and TWEAK are the receptor and ligand respectively and their mutual recognition and binding was reported to induce pathogenesis of cancer and chronic autoimmune diseases. We had identified Fn14 as a novel target of low linear energy transfer (LET) ionizing radiation in mice population. In the present study we generated the novel homology model of human Fn14, optimized its energy and validated for authenticity by checking Ramachandran plot and also by calculating the RMSD. Based on our earlier findings with Hippophae rhamnoides, a group of flavonoids and tannins were screened for their docking potential with Fn14 at the site where its natural ligand TWEAK was binding. The comparative docking analysis showed that the order of docking, from best to least, was Genistein, Rutin, Gallic acid ethyl ester and Quercetin, respectively. The findings predicted the radiomodifying action of flavonoids and tannins. The study has immediate applications in development of non-toxic drugs/ nutraceuticals that may protect human population from harmful effects of radiation in various situations, such as nuclear accidents, occupational exposure, diagnosis or radiotherapy.  相似文献   
20.
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