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   1157篇
  免费   44篇
  国内免费   4篇
耳鼻咽喉   5篇
儿科学   55篇
妇产科学   25篇
基础医学   147篇
口腔科学   6篇
临床医学   98篇
内科学   298篇
皮肤病学   25篇
神经病学   68篇
特种医学   39篇
外科学   120篇
综合类   14篇
预防医学   69篇
眼科学   27篇
药学   93篇
中国医学   9篇
肿瘤学   107篇
  2023年   15篇
  2022年   16篇
  2021年   42篇
  2020年   16篇
  2019年   25篇
  2018年   35篇
  2017年   16篇
  2016年   23篇
  2015年   27篇
  2014年   47篇
  2013年   55篇
  2012年   88篇
  2011年   91篇
  2010年   54篇
  2009年   30篇
  2008年   67篇
  2007年   60篇
  2006年   52篇
  2005年   51篇
  2004年   51篇
  2003年   27篇
  2002年   39篇
  2001年   13篇
  2000年   18篇
  1999年   27篇
  1998年   9篇
  1997年   14篇
  1995年   6篇
  1994年   11篇
  1992年   10篇
  1991年   15篇
  1990年   9篇
  1989年   12篇
  1988年   5篇
  1987年   9篇
  1986年   6篇
  1985年   14篇
  1984年   6篇
  1983年   9篇
  1982年   5篇
  1981年   6篇
  1980年   6篇
  1979年   12篇
  1978年   5篇
  1977年   5篇
  1976年   10篇
  1975年   6篇
  1974年   6篇
  1973年   8篇
  1972年   4篇
排序方式: 共有1205条查询结果,搜索用时 11 毫秒
21.
22.
Most studies of lateralized behaviour have to date focused on active behaviour such as sensorial perception and locomotion and little is known about lateralized postures, such as lying, that can potentially magnify the effectiveness of lateralized perception and reaction. Moreover, the relative importance of factors such as sex, age and the stress associated with social status in laterality is now a subject of increasing interest. In this study, we assess the importance of sex, age and reproductive investment in females in lying laterality in the Iberian ibex (Capra pyrenaica). Using generalized additive models under an information-theoretic approach based on the Akaike information criterion, we analyzed lying laterality of 78 individually marked ibexes. Sex, age and nursing appeared as key factors associated, in interaction and non-linearly, with lying laterality. Beyond the benefits of studying laterality with non-linear models, our results highlight the fact that a combination of static factors such as sex, and dynamic factors such as age and stress associated with parental care, are associated with postural laterality.  相似文献   
23.
An efficient and eco compatible approach for the regio- and stereoselective synthesis of structurally diverse novel hybrid heterocycles comprising spiropyrrolidine, indenoquinoxaline and indole structural units in excellent yields, has been achieved through a one-pot multicomponent process involving 1,3-dipolar cycloaddition as a key step. The 1,3-dipolar component is the azomethine ylide generated in situ from indenoquinoxaline and l-tryptophan and reacts with various substituted β-nitrostyrenes affording the spiroheterocyclic hybrids. The ring system thus created possesses two C–C and three C–N bonds and four adjacent stereogenic carbons, one of which is quaternary and the reaction proceeded with full diastereomeric control. All the synthesized compounds were assayed for their in vitro activity against Mycobacterium tuberculosis H37Rv using MABA assay. Interestingly, the compound bearing a 2-fluoro substituent on the aryl ring displayed an equipotent activity (MIC 1.56 μg mL−1) to ethambutol against Mycobacterium tuberculosis H37Rv.

An efficient and eco compatible approach for the regio- and stereoselective synthesis of structurally diverse novel spiropyrrolidine tethered indole hybrids in excellent yields employing a one-pot multicomponent 1,3-dipolar cycloaddition strategy.  相似文献   
24.
Two alkyl substituted triaryl-cyclopentadienyl ligands [4,4′-(4-phenylcyclopenta-1,3-diene-1,2-diyl)bis(methylbenzene) (1) and 4,4′,4′′-(cyclopenta-1,3-diene-1,2,4-triyl)tris(methylbenzene) (2)] have been synthesized via cross-aldol condensation followed by Zn-dust mediated cyclization and acid catalyzed dehydration reactions. The fluorescence properties of 1 and 2 have been studied in solution and solid state. The ligands exhibited aggregation-induced emission enhancement (AIEE) in THF/water solution. 1 and 2 have been found to be significantly more fluorescent in the solid state than in their respective solutions. This phenomenon can be attributed to the strong intermolecular CH⋯π interactions present in 1 and 2 which leads to the tight packing of molecules in their solid-state. Both 1, 2 and their corresponding anions have been studied by theoretical calculations. Ligands 1 and 2 have been shown to react with anhydrous DyCl3 in the presence of potassium metal at high temperature to afford two fluorescent chloride-bridged tetra-nuclear mixed potassium–dysprosium metallocenes [(Me2Cp)4Dy2IIICl4K2]·3.5(C7H8) (5) and [(Me3Cp)4Dy2IIICl4K2]·3(C7H8) (6), respectively in good yields.

Alkyl substituted triaryl-cyclopentadienyl ligands with aggregation-induced emission enhancement (AIEE) properties and their applications in the syntheses of novel chloride bridged tetra-nuclear mixed potassium–dysprosium metallocenes.  相似文献   
25.
BACKGROUND: Status of growth especially in early childhood is not only the most important determinant of health of a child but also a reflection of the well-being of the entire society. The extent of malnutrition in India is very high, but the exact magnitude varies considerably depending on which indicator is used. Child health in this paper is measured through chronic malnutrition (termed as stunting). Three states were selected, namely Bihar, West Bengal and Kerala. These three states represent the three stages of development. Bihar is one of the least and Kerala is one of the most developed states in India. AIM: The present paper aims to investigate the degree of chronic malnutrition in the context of socio-economic, demographic and other characteristics of the children and their households in the three selected states in India. SUBJECTS AND METHODS: The data for this study were taken from the National Family Health Survey (NFHS-2) conducted by the International Institute for Population Sciences (IIPS), Mumbai, in 1998-1999. The NFHS-2 sample covers ever-married women in the age group 15-49 years from 26 states in India. Besides collecting information on health, the survey collects data on socio-economic and demographic characteristics at individual and household level. RESULTS: The percentage of stunting of children in Bihar, West Bengal and Kerala was found to be 54, 39 and 23%, respectively. Regression analysis showed that the major factors that significantly influenced the status of health in the children in all three states were women's education and the household condition index. Months of breastfeeding and birth interval also had some association with health status. The effect of the above-mentioned variables was most prominent in Bihar and least in Kerala in terms of statistical significance. CONCLUSION: There is a close positive link between the nutritional status of pre-school children and the stages of development of the states. Mothers' education and household condition are important influences on children's health status irrespective of the stage of development.  相似文献   
26.
27.

Fungi play an important role in the degradation of leather goods. Economics often influence the choice of fungicide, thus, search for highly effective and low cost fungicides is immensely important. The authors have screened antifungal activity of ten Indian traditional medicinal plants viz Acalypha fruticosa, Acalypha indica, Aegle marmelos, Adathoda vasika, Calotropis gigantea, Erythrina indica, Morinda citrifolia, Nerium oleander, Pithecellobium dulce, and Acorus calamus based upon their traditional knowledge and usage. Various solvent extracts and essential oils were screened for antifungal activity against Aspergillus niger. The antifungal potency was compared to untreated control and standard antifungal drugs itraconazole and voriconazole. The bioactive principle from highly active fragment was isolated and chemically characterized. The mode of action was determined by a range of studies that include the lesion of plasma membrane, ergosterol content in the plasma membrane, acidification of external medium, and mitochondrial dehydrogenase activity in A. niger ATCC 16888. Among the ten plants studied, A. calamus exhibited greater antifungal potency in comparison to untreated control and standard drugs itraconazole and voriconazole. The minimum inhibitory concentration of both methanolic extract and essential oil of A. calamus against A. niger ATCC 16888 is around 5 µg/ml. The authors identified β-Asarone as the bioactive principle of A. calamus using spectral studies viz ultraviolet–visible spectroscopy, Fourier transform infrared spectroscopy and gas chromatography coupled mass spectroscopy. The results indicate that β-Asarone interfere and reduces the ergosterol content in the plasma membrane of A. niger ATCC 16888 thus exert their antifungal activity.

  相似文献   
28.
29.
European Journal of Nuclear Medicine and Molecular Imaging - Cardiac imaging with positron emission tomography/computed tomography (PET/CT) allows measurement of coronary artery calcium (CAC),...  相似文献   
30.
Vascular calcification progresses under hyperphosphatemia, and represents a risk factor for cardiovascular disease in chronic kidney disease (CKD) patients. We recently indicated that phosphorus (P) fluctuations also exacerbated vascular calcification in early-stage CKD rats. Dietary fiber intake is reportedly associated with cardiovascular risk. This study investigated the effects of dietary fiber on vascular calcification by repeated P fluctuations in early-stage CKD rats. Unilateral nephrectomy rats were used as an early-stage CKD model. For 36 days, a P fluctuation (LH) group was fed low-P (0.02% P) and high-P (1.2% P) diets alternating every 2 days, and a P fluctuation with dietary fiber intake (LH + F) group was fed low-P and high-P diets containing dietary fiber alternating every 2 days. The effect on vascular calcification was measured calcium content. Effects on uremic toxin were measured levels of indoxyl sulfate (IS) and investigated gut microbiota. The LH + F group showed significantly reduced vessel calcium content compared to the LH group. Further, dietary fiber inhibited increases in blood levels of IS after intake of high-P diet, and decreased uremic toxin-producing intestinal bacteria. Dietary fiber may help suppress progression of vascular calcification due to repeated P fluctuations in early-stage CKD rats by decreasing uremic toxin-producing intestinal bacteria.  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