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   1579篇
  免费   51篇
  2023年   27篇
  2022年   22篇
  2021年   50篇
  2020年   33篇
  2019年   49篇
  2018年   42篇
  2017年   48篇
  2016年   54篇
  2015年   55篇
  2014年   102篇
  2013年   118篇
  2012年   122篇
  2011年   156篇
  2010年   94篇
  2009年   71篇
  2008年   88篇
  2007年   93篇
  2006年   87篇
  2005年   79篇
  2004年   72篇
  2003年   57篇
  2002年   51篇
  2001年   11篇
  2000年   8篇
  1999年   4篇
  1998年   6篇
  1997年   2篇
  1996年   1篇
  1995年   3篇
  1994年   3篇
  1993年   1篇
  1991年   2篇
  1990年   4篇
  1989年   3篇
  1987年   1篇
  1986年   3篇
  1982年   2篇
  1979年   1篇
  1964年   1篇
  1963年   1篇
  1891年   2篇
  1889年   1篇
排序方式: 共有1630条查询结果,搜索用时 31 毫秒
101.
The antifungal activities of volatile phase effects of essential oils from Origanum onites, O. syriacum, O. minutiflorum, O. vulgare, O, marjorana, Thymus vulgaris, T. serpyllum, Rosmarinus officinalis, Salvia officinalis and Micromeria fruticosa were evaluated for their ability to inhibit growth of three vegetative compatibility groups (VCGs) of Verticillium dahliae. Carvacrol was the main component of O. onites, O. minutiflorum and O. vulgare essential oils, while γ-terpinene was the main component of O. syriacum. P-cymene and thymol were the dominant component of T. vulgaris and T. serpyllum. β- thujone and l-camphor were the main component of S. officinalis. Polegone and isomenthone were the dominant components of M. fruticosa essential oil. Based on the in vitro test, the degree of fungistatical effects can be ranked in the following order of inhibition: O. syriacum = O. onites = O. minutiflorum = O. vulgare = T. vulgaris > T. serpyllum > M. fruticosa > S. officinalis = O. marjorana > R. officinalis. The essential oils of S. officinalis, O. marjorana and R. officinalis displayed moderate antifungal activity, that increased with increasing concentrations. Among the VCGs, VCG2A and VCG4B were found to be highly sensitive to the essential oils. The essential oils of O. syriacum, O. onites, O. minutiflorum, O. vulgare and T. vulgaris were the most efficacious, demonstrating strong antifungal activity against all of the tested VCGs of V. dahliae at relatively low concentrations and they could find practical application as natural fungicides in the prevention and protection of plants from V. dahliae infections.  相似文献   
102.
The aim of this study was to evaluate the possible protective effects of quercetin (QE) against cholestatic oxidative stress and liver damage in the common bile duct ligated rats. A total of 24 male Wistar albino rats were divided into three groups: control, bile duct ligation (BDL) and BDL + received QE; each group contain 8 animals. The rats in QE treated groups were given QE (15 mg/kg) once a day intraperitoneally for 4 weeks starting 3 days prior to BDL operation. The changes demonstrating the bile duct proliferation and fibrosis in expanded portal tracts include the extension of proliferated bile ducts into lobules, mononuclear cells, and neutrophil infiltration into the widened portal areas were observed in BDL group. Treatment of BDL with QE attenuated alterations in liver histology. The alpha smooth muscle actin (α-SMA), transforming growth factor beta (TGF-β1) positive cells and the activity of TUNEL in the BDL were observed to be reduced with the QE treatment. The data indicate that QE attenuates BDL-induced cholestatic liver injury, bile duct proliferation, and fibrosis. The hepatoprotective effect of QE is associated with antioxidative potential.  相似文献   
103.
Salvia ballsiana (Rech. fil.) Hedge, previously known only from the type gathering, is a local endemic species from Turkey. The species was first collected from Gölbaşı (Malatya) by E. K. Balls in 1935, and was not collected again until 2008, when we found it in Gerger (Adıyaman). The diagnostic morphological characters of this rare endemic species are discussed, including its anatomical, palynological and nutlet micromorphological features. Morphological characteristics of leaves, calyces, corollas and types of stamens are useful for sectional and specific delimitation in Salvia . Anatomical characters such as number of ray rows in roots, distance between vascular bundles in stems, mesophyll structures in leaves, shape of mid-rib and presence/absence of sclerenchymatic tissue in petioles are of taxonomic significance. In addition, size, shape and ornamentation of pollen grains and nutlets are diagnostic.  相似文献   
104.
Hypercholesterolemia and lipid peroxidation play complementary roles in atherosclerosis. Artichoke (Cynara scolymus L., Asteraceae) leaf extract (ALE), rich in antioxidants, has cholesterol-reducing effect. We investigated the effect of ALE on serum and hepatic lipid levels and pro-oxidant–antioxidant balance in the liver and heart of hypercholesterolemic rats. Rats were fed on 4% (w/w) cholesterol and 1% cholic acid (w/w) supplemented diet for 1 month. ALE (1.5 g/kg/day) was given by gavage during the last 2 weeks. High cholesterol (HC) diet caused significant increases in serum and liver cholesterol and triglyceride levels. It increased malondialdehyde (MDA) and diene conjugate (DC) levels in both tissues. Hepatic vitamin E levels and hepatic and cardiac glutathione peroxidase (GSH-Px) activities decreased, but superoxide dismutase and glutathione transferase activities, glutathione, and vitamin C levels remained unchanged due to HC diet. Serum cholesterol and triglyceride levels and ratio of cholesterol to high-density lipoprotein (HDL)-cholesterol decreased in ALE plus HC-treated rats, but liver cholesterol and triglyceride levels remained unchanged. Significant decreases in hepatic and cardiac MDA and DC levels and increases in hepatic vitamin E and GSH-Px activities were observed in ALE-treated hypercholesterolemic rats. Our results indicate that ALE decreases serum lipids and hypercholesterolemia-induced pro-oxidant state in both tissues.  相似文献   
105.
106.
We use replica-exchange molecular dynamics (REMD) to interrogate molecular structures and properties of four engineered dodecapeptides (in solution, in the absence of a surface) that have been shown to bind to quartz with different propensities. We find that all of the strong-binding peptides feature some polyproline type II secondary structure, have less conformational freedom, and feature fewer intrapeptide hydrogen bonds compared with the weak binder. The regions of contiguous proline content in a given sequence appear to play a role in fostering some of these properties of the strong binders. For preliminary insights into quartz binding, we perform lattice-matching studies between a grid corresponding with the quartz (100) surface and the strong-binding peptide REMD structures. Our findings indicate a commonality among the putative contact residues, even for peptide structures with very different backbone conformations. Furthermore, interpeptide interactions in solution are studied. Our preliminary findings indicate that the strong-binder interpeptide contacts are dominated by weak, nonspecific hydrophobic interactions, while the weak-binding peptide shows more variable behavior due to the distribution of charged residues. In summary, the solution structures of peptides appear to be significant. We propose that these differences in their intra- and interpeptide interactions can influence their propensity to bind onto a solid substrate.  相似文献   
107.
Dielectric heaters and sealers present the most common source of occupational exposure to excessive radio frequency (RF) fields. These systems are used industrially to heat or melt dielectric materials. Nowadays, the effects of high frequency electromagnetic (EM) fields on the health have been discussed frequently but there are few health studies done for workers around dielectric heaters and sealers. In this study, the leakage fields around dielectric heaters and sealers (27.12?MHz) were measured in MKE--Mechanical and Chemical Industry Corporation, Gazi Rocket Factory and evaluated in terms of standards. It has been observed that operators exposed to same RF fields with occupational exposure limits. Many workers have health complaints, such as elevated body temperatures in the factory. Safe distances or areas for workers should be recommended in these systems. Protective measures could be implemented to minimize these exposures. Further measurements and occupational exposure studies of RF exposed women and men are needed to demonstrate the levels of exposed Radio Frequency Radiation (RFR). Precautions should therefore be taken either to reduce the leakage fields or minimise the exposed fields.  相似文献   
108.
109.
110.
Demirkan A  Melli M 《Lab animal》2007,36(2):39-41
Many studies require collection of metabolic wastes from laboratory animals, and oftentimes it is important that feces and urine be collected separately. The authors describe an easily assembled and inexpensive device that can be used to collect urine samples from rats without any invasive operations. The device affords reasonable separation of feces and urine.  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