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   8004篇
  免费   744篇
  国内免费   21篇
耳鼻咽喉   72篇
儿科学   246篇
妇产科学   276篇
基础医学   1091篇
口腔科学   123篇
临床医学   949篇
内科学   1518篇
皮肤病学   135篇
神经病学   908篇
特种医学   233篇
外科学   803篇
综合类   231篇
一般理论   7篇
预防医学   924篇
眼科学   195篇
药学   480篇
中国医学   20篇
肿瘤学   558篇
  2023年   80篇
  2022年   127篇
  2021年   245篇
  2020年   167篇
  2019年   252篇
  2018年   246篇
  2017年   154篇
  2016年   180篇
  2015年   208篇
  2014年   275篇
  2013年   380篇
  2012年   554篇
  2011年   529篇
  2010年   281篇
  2009年   270篇
  2008年   428篇
  2007年   416篇
  2006年   437篇
  2005年   406篇
  2004年   410篇
  2003年   400篇
  2002年   353篇
  2001年   165篇
  2000年   141篇
  1999年   148篇
  1998年   93篇
  1997年   72篇
  1996年   68篇
  1995年   71篇
  1994年   59篇
  1993年   49篇
  1992年   103篇
  1991年   90篇
  1990年   61篇
  1989年   77篇
  1988年   61篇
  1987年   53篇
  1986年   61篇
  1985年   53篇
  1984年   52篇
  1983年   39篇
  1982年   39篇
  1981年   36篇
  1980年   28篇
  1979年   25篇
  1978年   31篇
  1977年   35篇
  1975年   29篇
  1974年   22篇
  1972年   21篇
排序方式: 共有8769条查询结果,搜索用时 171 毫秒
1.
BackgroundA venous leg ulcer is a chronic leg wound caused by poor venous blood circulation in the lower limbs. It is a recurring condition causing pain, malodour, reduced mobility, and depression. Randomised controlled trials evaluating treatments for venous leg ulcers provide important evidence to inform clinical decision-making. However, for findings to be useful, outcomes need to be clinically meaningful, consistently reported across trials, and fully reported. Research has identified the large number of outcomes reported in venous leg ulcer trials, impacting both synthesis of results, and clinical decision-making. To address this, a core outcome set will be developed. A core outcome set is an agreed standardised set of outcomes which should be, as a minimum, measured and reported in all trials which evaluate treatment effectiveness for a given indication. A core outcome set has the potential to reduce research waste, improve the utility of RCTs, reduce reporting bias, facilitate treatment comparisons across different sources of evidence and expedite the production of systematic reviews, meta-analyses and evidence-based clinical guidelines.AimThe aim of this project is to develop a core outcome set for research evaluating the effectiveness of interventions for treating venous leg ulceration.MethodsThrough a scoping review of the literature on venous leg ulceration, we will firstly identify a list of candidate outcome domains (broad categories in relation to what is being measured) from randomised controlled trials and qualitative research, and outcomes (specific methods in relation to what is being measured). In two further stages, we will use the resulting lists of outcome domains and outcomes to design two online surveys. A range of stakeholders will be invited to participate in the surveys and they will be asked to indicate which outcome domains and outcomes are most important and should be considered as core in future research reports.  相似文献   
2.
Weaver mutant mice are characterized by a decrease in striatal dopamine (DA), which is associated with a progressive loss of DA neurones in the substantia nigra. This mutant thus provides the opportunity to examine the functional effects of DA neurones grafted to the striatum in a genetic model of parkinsonism. Ventral mesencephalic tissue from normal foetuses was placed on the surface of the right dorsal striatum of adult weaver mutants. After grafting, animals were tested for methamphetamine-induced circling behaviour. Mutants with DA containing grafts displayed a significant circling bias toward the left, non-grafted side. Mutants without grafts did not display any rotational bias to either side. These results demonstrate that grafted DA containing neurones establish a functional innervation of the weaver striatum and suggest that grafting of neural tissue is a viable approach in restoring function in genetic degenerative disorders of the nigrostriatal system.  相似文献   
3.
Forty samples of cord blood lymphocytes were isolated from 40 normal healthy full-term newborns. The initial 20 samples were used to determine the dose-response curve of three different thymic extracts (TP-1, bovine thymic extract; TG-15-I and TG-15-II, both porcine thymic extracts) and one of renal origin (KG-1) as a control of non-lymphoid organ extract, by measuring the E-rosette T cells. Results showed that E-rosette T cells increased significantly when the thymic extract concentration was increased to 12.5 micrograms/ml. However, there was no statistical difference between TP-1, TG-15-I and TG-15-II in the increase of E-rosette-forming cells. The remaining 20 samples were preincubated with 0, 12.5, 25 or 50 micrograms/ml of thymic extracts. It was observed that the lymphoproliferation, interleukin-2 (IL-2), gamma-interferon (IFN-gamma) and tumor necrotic factor (TNF) production were all significantly increased after thymic extract treatment. No statistical difference between these three thymic preparations in the stimulation of lymphoproliferative response was found. However, among the three thymic extracts, TP-1 appears to induce the highest amounts of IL-2, IFN-gamma and TNF. Of the TG-15-I and TG-15-II, the former stimulates higher IL-2 production whereas the latter enhances IFN-gamma and TNF production. The different immunostimulating effects and potencies that these three thymic extracts showed may reflect not only the species difference but also the difference in preparation procedures. Different components in these thymic extracts may be responsible for different biological activities. Results from these comparative studies may provide useful information in future clinical trials for the treatment of the primary immunodeficiency diseases according to their pathogenesis and may also indicate a possible beneficial effect of the combination of chemotherapy and thymic extracts.  相似文献   
4.
5.
Endoneurial hypoxia and a high frequency of closed capillaries have been found in chronic experimental diabetes and human diabetic sural nerve, respectively. These findings have led to the hypothesis that the pathogenesis of diabetic neuropathy is due to endoneurial hypoxia. To evaluate the role of endoneurial hypoxia in experimental diabetic neuropathy, the effects of supplementation and deprivation of oxygen on peripheral nerve lipid biosynthesis were studied in normal control and streptozotocin-induced diabetic rats. Defective lipid biosynthesis in diabetic nerve was partially prevented by oxygen supplementation. When normal rats were placed in a hypoxic chamber, lipid abnormalities similar to those observed in diabetic nerves were demonstrated in the absence of changes in nerve free sugars. These findings suggest that endoneurial hypoxia may underlie some key biochemical abnormalities encountered in experimental diabetic neuropathy.  相似文献   
6.
INTRODUCTION: Angiotensin (Ang) IV enhances learning and memory in rats but there are strain differences in its effects in mice. Oxytocin (OT) also influences learning and memory in rats and mice and, in the light of the proposed effects of Ang IV on oxytocinase, the hypothesis that the effects of Ang IV on cognition in mice involve OT was tested. MATERIALS AND METHODS: The effects of Ang IV and OT, alone and combined, were determined in rat isolated uterine smooth muscle and in object recognition and forced swim tests in BKW mice. RESULTS: Ang potentiated the contractile effects of OT in the uterus. Neither peptide had any effect on object recognition nor locomotor activity. Ang IV had no effect in the forced swim test but abolished the effects of OT. CONCLUSIONS: Ang IV influences the actions of OT in vitro and in vivo, possibly by inhibition of oxytocinase, but the lack of effect of Ang IV on object recognition in BKW mice is unlikely to be a consequence of a deficiency endogenous OT. Unlike OT, Ang IV alone has no effect on learned helplessness in the forced swim test, an effect often used to predict potential antidepressant efficacy in humans.  相似文献   
7.
8.
AIM: Although research has demonstrated the efficacy of pelvic floor exercises (PFXs) for the prevention and treatment of female urinary incontinence (FUI), adherence to PFX regimens is commonly poor. There is some evidence that this finding is in part due to a lack of knowledge about how to perform PFXs correctly and misconceptions about the required frequency and duration of PFX regimens. METHODS: By using a sample of 720 postpartum women, this study investigates women's PFX regimens both before and during pregnancy and postpartum. RESULTS: Findings demonstrated that most women were aware of the required frequency for PFXs (at least every second day): just over half had done them this often during pregnancy and 91% intended to do so postpartum. However, few had done them at this level before pregnancy and less than half knew that PFXs should be carried out indefinitely throughout the lifetime. Moreover, only two thirds were confident that they were doing PFXs correctly. CONCLUSION: The findings suggest that, despite good knowledge of the required frequency of PFXs, few women practise them regularly over their lifetime, many apparently perceiving PFXs as relevant only to the childbirth years. Implications for health professionals in addressing these gaps in women's knowledge and practises are discussed.  相似文献   
9.
An efficient shim system and an optimized localization sequence were used to measure in vivo 1H NMR spectra from cerebral cortex, hippocampus, striatum, and cerebellum of C57BL/6 mice at 9.4 T. The combination of automatic first- and second-order shimming (FASTMAP) with strong custom-designed second-order shim coils (shim strength up to 0.04 mT/cm2) was crucial to achieve high spectral resolution (water line width of 11-14 Hz). Requirements for second-order shim strengths to compensate field inhomogeneities in the mouse brain at 9.4 T were assessed. The achieved spectral quality (resolution, S/N, water suppression, localization performance) allowed reliable quantification of 16 brain metabolites (LCModel analysis) from 5-10-microL brain volumes. Significant regional differences (up to 2-fold, P < 0.05) were found for all quantified metabolites but Asp, Glc, and Gln. In contrast, 1H NMR spectra measured from the striatum of C57BL/6, CBA, and CBA/BL6 mice revealed only small (<13%, P < 0.05) interstrain differences in Gln, Glu, Ins, Lac, NAAG, and PE. It is concluded that 1H NMR spectroscopy at 9.4 T can provide precise biochemical information from distinct regions of the mouse brain noninvasively that can be used for monitoring of disease progression and treatment as well as phenotyping in transgenic mice models.  相似文献   
10.
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