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   2018359篇
  免费   145556篇
  国内免费   2974篇
耳鼻咽喉   27519篇
儿科学   66369篇
妇产科学   56642篇
基础医学   295335篇
口腔科学   59045篇
临床医学   177005篇
内科学   385675篇
皮肤病学   43677篇
神经病学   157902篇
特种医学   79012篇
外国民族医学   529篇
外科学   304592篇
综合类   46145篇
现状与发展   3篇
一般理论   647篇
预防医学   155071篇
眼科学   46462篇
药学   153233篇
  40篇
中国医学   3783篇
肿瘤学   108203篇
  2018年   18523篇
  2015年   18428篇
  2014年   25378篇
  2013年   38832篇
  2012年   52439篇
  2011年   56039篇
  2010年   32926篇
  2009年   31394篇
  2008年   53681篇
  2007年   56827篇
  2006年   57806篇
  2005年   55864篇
  2004年   55154篇
  2003年   52658篇
  2002年   51717篇
  2001年   93195篇
  2000年   96593篇
  1999年   81487篇
  1998年   21922篇
  1997年   19862篇
  1996年   20052篇
  1995年   19428篇
  1994年   18266篇
  1993年   17294篇
  1992年   66970篇
  1991年   66216篇
  1990年   65153篇
  1989年   62965篇
  1988年   58487篇
  1987年   57675篇
  1986年   54763篇
  1985年   52985篇
  1984年   39476篇
  1983年   33928篇
  1982年   19619篇
  1981年   17732篇
  1980年   16645篇
  1979年   37895篇
  1978年   26546篇
  1977年   22406篇
  1976年   21262篇
  1975年   22891篇
  1974年   27818篇
  1973年   26586篇
  1972年   24726篇
  1971年   23387篇
  1970年   21540篇
  1969年   20310篇
  1968年   18712篇
  1967年   16960篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The interaction of trolox with ammonia, alkylamines of different classes, and amino derivatives of heterocyclic compounds, including nitroxyl radicals and alkaloids, led to the production of ammonium salts called ion conjugates (ICs). Five ICs were characterised by X-ray diffraction. This is the first time a wide range of ICs were made from trolox with amines, and ESI-MS data demonstrated they have the potential to generate pseudomolecular [(A?B+)?+?H]+ ions. For all obtained trolox ICs, a significant increase (1–3 orders of magnitude) in water solubility was achieved while retaining high antioxidant activity. ICs synthesised from two biologically active fragments may be used to create polyfunctional agents with varying solubility and bioavailability.  相似文献   
92.
Resveratrol (RL), a natural polyphenol, is known for its diverse biological effects against various human cancer cell lines. But low aqueous solubility, poor bioavailability, and stability limit its efficacy against prostate cancer. In this study polymeric nanoparticles encapsulating resveratrol (RLPLGA) were designed and their cytotoxic and mode of apoptotic cells death against prostate cancer cell line (LNCaP) was determined. Nanoparticles were prepared by solvent displacement method and characterized for particle size, TEM, entrapment efficiency, DSC and drug release study. RLPLGA exhibited a significant decrease in cell viability with 50% and 90% inhibitory concentration (IC50 and IC90) of 15.6?±?1.49 and 41.1?±?2.19?μM respectively against the LNCaP cells. This effect was mediated by apoptosis as confirmed by cell cycle arrest at G1-S transition phase, externalization of phosphatidylserine, DNA nicking, loss of mitochondrial membrane potential and reactive oxygen species generation in LNCaP cells. Furthermore, significantly greater cytotoxicity to LNCaP cells was observed with nanoparticles as compared to that of free RL at all tested concentrations. RLPLGA nanoparticles presented no adverse cytotoxic effects on murine macrophages even at 200?μM. Our findings support the potential use of developed resveratrol loaded nanoparticle for the prostate cancer chemoprevention/ chemotherapy with no adverse effect on normal cells.  相似文献   
93.
94.
Genetically informative designs and, in particular, twin studies, are the most widely used methodology to analyse the relative contribution of genetic and environmental factors to inter-individual variability. These studies basically compare the degree of phenotypical similarity between monozygotic and dizygotic twin pairs. In addition to the traditional estimate of heritability, this kind of registry enables a wide variety of analyses which are unique due to the characteristics of the sample. The Murcia Twin Registry is population-based and focused on the analysis of health-related behaviour. The observed prevalence of health problems is comparable to that of other regional and national reference samples, which guarantees its representativeness. Overall, the characteristics of the Registry facilitate developing various types of research as well as genetically informative designs, and collaboration with different initiatives and consortia.  相似文献   
95.
96.
The aims of this study were to evaluate the weekly and annual cumulative radiofrequency-electromagnetic field (RF-EMF) exposure attributed to mobile phone (MP) use, and assess whether a novel app (Quanta Monitor?) could be employed in a small human sample to characterise the RF-EMF exposures associated with the use of MPs. Ten participants provided their two months’ daily objective data on their MP exposures (i.e. transmitted and received power densities) attributed to different modes of MP usage such as cellular calls, cellular data and Wi-Fi. The results demonstrated that total transmitted power density (cellular phone calls, data and Wi-Fi surfing) could be many orders of magnitude higher than that from the total received power density. Of the total transmitted power density, cellular data use contributed the largest portion. Our study showed that Quanta Monitor? could be employed in prospective assessment of exposures to MPs in epidemiological studies.  相似文献   
97.
98.
99.
100.
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