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   185361篇
  免费   12491篇
  国内免费   9458篇
耳鼻咽喉   1581篇
儿科学   3737篇
妇产科学   2780篇
基础医学   17381篇
口腔科学   3982篇
临床医学   21186篇
内科学   25761篇
皮肤病学   2268篇
神经病学   7063篇
特种医学   7973篇
外国民族医学   34篇
外科学   15456篇
综合类   36386篇
现状与发展   23篇
一般理论   17篇
预防医学   17533篇
眼科学   3890篇
药学   17454篇
  96篇
中国医学   11681篇
肿瘤学   11028篇
  2024年   272篇
  2023年   1362篇
  2022年   3280篇
  2021年   4399篇
  2020年   3505篇
  2019年   3011篇
  2018年   3288篇
  2017年   3336篇
  2016年   3498篇
  2015年   5272篇
  2014年   6918篇
  2013年   7751篇
  2012年   11374篇
  2011年   14586篇
  2010年   10515篇
  2009年   8672篇
  2008年   10279篇
  2007年   10065篇
  2006年   9596篇
  2005年   9846篇
  2004年   12510篇
  2003年   11933篇
  2002年   9500篇
  2001年   7595篇
  2000年   5270篇
  1999年   5101篇
  1998年   3227篇
  1997年   3013篇
  1996年   2058篇
  1995年   1742篇
  1994年   1718篇
  1993年   2123篇
  1992年   1948篇
  1991年   1660篇
  1990年   1308篇
  1989年   1105篇
  1988年   860篇
  1987年   737篇
  1986年   685篇
  1985年   407篇
  1984年   234篇
  1983年   171篇
  1982年   121篇
  1981年   114篇
  1980年   81篇
  1979年   132篇
  1978年   98篇
  1977年   101篇
  1976年   80篇
  1975年   92篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
骨巨细胞瘤的MRI诊断价值   总被引:10,自引:0,他引:10  
目的探讨骨巨细胞瘤的MRI表现特点及其病理基础。资料与方法搜集经手术病理证实的12例骨巨细胞瘤患者资料,分析其MRI征象并与病理结果对照。结果T1WI上肿瘤实体表现为低、等信号,T2WI上为不均匀高信号,Gd-DTPA增强扫描呈中度到明显强化。此外,MRI还可显示肿瘤内坏死、出血、含铁血黄素沉着等。结论MRI能够提供比较全面的影像学信息,可提高对骨巨细胞瘤诊断的准确性。  相似文献   
52.
表皮生长因子及其受体与流产关系的探讨   总被引:4,自引:0,他引:4  
采用放射免疫竞争抑制饱和分析法,检测47例难免流产患者,65例人工流产及20例健康非孕妇女血清表皮生长因子(EGF)水平;同时采用免疫组织化学法检测流产者胚胎组织中表皮生长因子受体(EGFR)表达程度。结果:人工流产组血清EGF水平高于自然流产及非孕妇女,而自然流产与非孕妇女差异无显著性;胚胎组织中EGFR阳性表达率人工流产组明显高于自然流产组。提示:EGF通过与其受体结合对妊娠维持、胚胎及胎儿的  相似文献   
53.
小切口胆囊切除术108例临床观察   总被引:1,自引:0,他引:1  
本文报告腹部切口5-8cm的小切口胆囊切除术108例,与同期大切口胆囊切除术相比,具有创伤较小、恢复较快、并发症少、切口疤痕小的优点,虽不如腹腔镜胆囊切除术(LC)的疼痛轻、恢复快,但并症比LC少,只要适应症选择得当,在术者的经验和技术较成熟的情况下,不昔为一种可供选择的方法。  相似文献   
54.
短暂性脑缺血发作患者血浆中TXB2和PGF1α含量检测   总被引:3,自引:0,他引:3  
本文用放射免疫法测定47例短暂性脑缺血发作(TIA)患者血浆中血栓素B_2(TXB_2)和6酮-前列腺F_(1α)(PGF_(1α))的含量。结果发现TIA患者血浆中TXB_2含量增高,PGF_(1α)降低;头颅CT或MRI示有小灶性梗塞者及TIA发作持续时间长于30min者TXB_2升高和PGF_(1α)降低更显著。治疗3个月后,血浆PGF_(1α)显著增高。TXB_2和PGF_(1α)在体内的失平衡是急性脑血管疾病发病的重要机理之一。  相似文献   
55.
Extracellular phospholipase A2 (PLA2) is a proinflammatory enzyme found especially in the inflammatory exudate to modulate blood flow to areas of antigen stimulation. In this study we found that PLA2 exerted a biphasic effect on the proliferation of phytohemagglutinin (PHA)-stimulated human mononuclear cells (PHA MNC). At low concentrations range from 0.001 to 1 U/ml, PLA2 enhanced the proliferation of PHA MNC (maximal increase was 37.0 +/- 5.67%). Conversely, at concentrations over 10 U/ml, PLA2 markedly suppressed the PHA-induced MNC proliferation (maximal decrease was 88.86 +/- 2.89%). PLA2 was non-toxic to lymphocytes after three days culture, unless the concentration was higher than 100 U/ml. The membrane polarization of PHA-stimulated lymphocytes was also increased by PLA2 at a low concentration. In addition, PLA2 displayed a similar effect on the proliferation of streptokinase-streptodornase (SK/SD) or allogeneic cell stimulated lymphocytes. The change of lymphocyte proliferation by PLA2, was parallel to the change of percentage of helper T cells. Furthermore--a CD4-rich population was proved more susceptible to PLA2 effect than a CD8-rich population. Para-bromophenacyl bromide (pBPB), an irreversible inhibitor of PLA2, abrogated the biphasic effect of PLA2 on PHA MNC proliferation. These results suggest that PLA2 plays a regulatory role on immune reactions by modulating the percentage of helper T cells.  相似文献   
56.
.We report five patients with Laurence-Moon-Bardet-Biedl syndrome (LMBBS) who had renal involvement. Intravenous pyelography showed bilateral or unilateral calyceal clubbing and blunting in all patients. In addition, one patient had a parapelvic cyst in the left kidney and another had bilateral lobulated renal outlines of the fetal type. One patient had a urinary concentrating defect and two patients showed increased fractional sodium excretion. Estimated tubular phosphate reabsorption values were in normal limits in all of five patients. No patient had a urine acidification defect, proteinuria, glycosuria, or hyperaminoaciduria. One patient died from end-stage renal failure. The remaining four patients had normal serum creatinine values and estimated creatinine clearances. 99mTechnetium-diethylenetriamine pentaacetate renal scanning showed prolonged and delayed concentration and delayed excretion in three of the four patients who survived. A focal scar was determined on the left kidney of one of four patients by 99mtechnetium-dimercaptosuccinic acid renal scanning. All LMBBS cases with or without renal symptoms should be routinely evaluated for renal abnormalities. Renal scanning is a valuable method, especially for determining the renal involvement in the early stage of disease. Received November 14, 1995; received in revised form and accepted May 23, 1996  相似文献   
57.
58.
为了探讨精神分裂症患者治疗期间多巴胺的变化,我们选择舒必利治疗组20例,非舒必利治疗组10例作为病例组;15例非精神病患者作为对照组;检测脑脊液中多巴胺代谢产物高香草酸的含量;结果显示两组无显著性差异。精神分裂症患者治疗后舒必利组高香草酸含量升高,非舒必利组则降低,进一步分析显示舒必利治疗组非显效者较显效者治疗后高香草酸显著升高。提示机体对药物阻滞多巴胺受体后代偿反应的强弱与疗效有一定关系。  相似文献   
59.
Ischaemia-reperfusion injury (IRI) is of obvious relevance in situations where there is an interruption of blood supply to the gut, as in vascular surgery, or in the construction of free intestinal grafts. It is now appreciated that IRI also underlies the gut dysfunction that occurs in early shock, sepsis, and trauma. The events that occur during IRI are complex. However, recent advances in cellular biology have started to unravel these underlying processes. The aim of this review is to provide an outline of current knowledge on the mechanisms and consequences of IRI. Initially, IRI appears to be mediated by reactive oxygen metabolites and, at a later stage, by the priming and activation of polymorphonuclear neutrophils (PMN). Ischaemia-reperfusion injury can diminish the barrier function of the gut, and can promote an increase in the leakage of molecules (intestinal permeability) or the passage of microbes across the wall of the bowel (bacterial trans-location). Ischaemia-reperfusion injury to the gut can result in the generation of molecules that may also harm distant tissues.  相似文献   
60.
The synaptic connections established by grafted noradrenergic (NA) neurons into the lesioned adult rat spinal cord were analysed using immunocytochemistry at the electron microscopic level. An embryonic cell suspension of the locus coeruleus region from E-13 rat embryos was transplanted into the spinal cord following either: (1) spinal cord transection or (2), partial selective denervation by 6-hydroxy dopamine (6-OH DA). One month after grafting, the NA-neurons established, in the two models, an innervation pattern similar to that found in the intact spinal cord. In both models, the transplanted NA-immunoreactive neurons formed extensive synaptic contacts with dendrites, spines and perikarya. The proportion of axodendritic and axospinous contacts was inverse in the two models. The first model thus reproduced more closely the normal synaptic pattern prefering dendritic targets, which could correspond to a better integration of the graft. In the second model, a partially NA-denervated spinal cord, there existed a competition between residual intrinsic and grafted neuron-derived fibres, which presumably affects synaptogenesis. In conclusion, the present study illustrate the complexity of cell interations conducting to the formation of a specific circuitry. Recognition phenomenon are likely modulated by space constraints, which ultimately shape-up the geometry of synaptic contacts.  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