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   21521篇
  免费   1912篇
  国内免费   1507篇
耳鼻咽喉   125篇
儿科学   217篇
妇产科学   196篇
基础医学   2657篇
口腔科学   373篇
临床医学   3059篇
内科学   3118篇
皮肤病学   222篇
神经病学   1130篇
特种医学   746篇
外国民族医学   13篇
外科学   2094篇
综合类   3977篇
现状与发展   5篇
预防医学   1097篇
眼科学   563篇
药学   2329篇
  21篇
中国医学   1191篇
肿瘤学   1807篇
  2024年   78篇
  2023年   410篇
  2022年   964篇
  2021年   1166篇
  2020年   898篇
  2019年   716篇
  2018年   810篇
  2017年   690篇
  2016年   698篇
  2015年   1060篇
  2014年   1277篇
  2013年   1079篇
  2012年   1607篇
  2011年   1766篇
  2010年   1032篇
  2009年   803篇
  2008年   1073篇
  2007年   1055篇
  2006年   1087篇
  2005年   1058篇
  2004年   697篇
  2003年   629篇
  2002年   545篇
  2001年   488篇
  2000年   510篇
  1999年   512篇
  1998年   307篇
  1997年   304篇
  1996年   213篇
  1995年   206篇
  1994年   218篇
  1993年   122篇
  1992年   135篇
  1991年   128篇
  1990年   124篇
  1989年   90篇
  1988年   88篇
  1987年   77篇
  1986年   63篇
  1985年   59篇
  1984年   23篇
  1983年   12篇
  1982年   15篇
  1981年   15篇
  1980年   3篇
  1979年   15篇
  1978年   2篇
  1977年   5篇
  1976年   3篇
  1974年   3篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
42.
Deng X  Cadet JL 《Brain research》1999,851(1-2):254-257
The accumulated evidence suggests that the overproduction of nitric oxide (NO) is involved in methamphetamine (METH)-induced neurotoxicity. Using NADPH-diaphorase histochemistry, neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) antibody immunohistochemistry, the possible overexpression of nNOS and iNOS was investigated in the brains of mice treated with METH. The number of positive cells or the density of positive fibers was assessed at 1 h, 24 h and 1 week after METH injections. There were no clear positive iNOS cells and fibers demonstrated in the brains of mice after METH treatment. In contrast, METH caused marked increases in nNOS in the striatum and hippocampus at 1 and 24 h post-treatment. The nNOS expression normalized by 1 week. There were no statistical changes in nNOS expression in the frontal cortex, the cerebellar cortex, nor in the substantia nigra. These results provide further support for the idea that NO is involved in the neurotoxic effects of METH.  相似文献   
43.
Injury to a peripheral nerve induces in the dorsal root ganglia (DRG) sprouting of sympathetic and peptidergic terminals around large-diameter sensory neurons that project in the damaged nerve. This pathological change may be implicated in the chronic pain syndromes seen in some patients with peripheral nerve injury. The mechanisms underlying the sprouting are not known. Using in situ hybridization and immunohistochemical techniques, we have now found that nerve growth factor (NGF) and neurotrophin-3 (NT3) synthesis is upregulated in satellite cells surrounding neurons in lesioned DRG as early as 48 h after nerve injury. This response lasts for at least 2 months. Quantitative analysis showed that the levels of mRNAs for NT3 and NGF increased in ipsilateral but not contralateral DRG after nerve injury. Noradrenergic sprouting around the axotomized neurons was associated with p75-immunoreactive satellite cells. Further, antibodies specific to NGF or NT3, delivered by an osmotic mini-pump to the DRG via the lesioned L5 spinal nerve, significantly reduced noradrenergic sprouting. These results implicate satellite cell-derived neurotrophins in the induction of sympathetic sprouting following peripheral nerve injury.  相似文献   
44.
45.
术后患者肠道吸收乳果糖、甘露醇的变化与创伤程度的关系   总被引:12,自引:0,他引:12  
Sun M  Liu Y  Liu W  Deng G  Tang W  Jiang Z 《中华外科杂志》1999,37(5):298-300
目的 测定手术后患者肠道对甘露醇和乳果糖吸收的变化,并研究这些变化与手术应激程度的关系。方法 用小剂量乳果糖(lactulose,L,2g)和甘露醇(mannitol,M,1g)的方法测定20例腹部手术患者术前,术后第5第和10天乳果糖/甘露醇比值(L/M比值)的变化。用急性生理和慢性健康状况评分方法Ⅱ(APACHEⅡ)对患者的创伤程度进行评分。用带电化学检测器的高压液相色谱仪测定尿中的乳果糖和甘  相似文献   
46.
47.
Brief ischaemia or heat stress protects the myocardium against ischaemia-reperfusion injury. Heat stimulus evokes release of sensory nerve transmitters, including calcitonin gene-related peptide (CGRP). Since CGRP has been shown to play an important role in the mediation of ischaemic preconditioning, the present study examined whether early or delayed preconditioning induced by retrograde hyperthermic perfusion in vitro or by whole-body hyperthemia in vivo also involves endogenous CGRP. Isolated rat hearts were perfused in the Langendorff mode and subjected to 30 min global ischaemia and 30 min reperfusion. Heart rate, coronary flow, left ventricular pressure and its first derivatives (±dp/dt) were recorded and the CGRP-like immunoreactivity (CGRP-LI) content and the release of creatine kinase (CK) during reperfusion were measured. Retrograde hyperthermic perfusion (42 °C) for 5 min improved the recovery of cardiac function, decreased the release of CK and elevated the content of CGRP-LI in the coronary effluent. CGRP8–37 (10–7 mol/l), a selective CGRP receptor antagonist, abolished the cardioprotection by heat stress. Pretreatment with capsaicin (50 mg/kg s.c.), which specifically depletes sensory nerve transmitter content, abolished both the cardioprotection and the increased release of CGRP-LI. Whole-body hyperthermia (42 °C for 15 min) caused an increase in the plasma concentration of CGRP-LI. Early or delayed protection was shown in the hearts obtained from the animals subjected to whole-body hyperthermia 10 min or 48 h before the experiments. The early or delayed protection by heat stress was also abolished by pretreatment with capsaicin. The present study suggests that, in the rat, the early and delayed cardioprotection induced by heat stress involves endogenous CGRP. Received: 31 December 1998 / Accepted: 6 April 1999  相似文献   
48.
The causes of Datura intoxication include medication overdose, misuse of edible vegetables, deliberate abuse as a hallucinogen, homicidal or robbery and accidental intoxication from contaminated food. We report an incident of 14 people with Datura intoxication caused by ingesting wild Datura suaveolans for food. The incubation period was 15 to 30 min. The symptoms/signs were dizziness, dry mouth, flushed skin, palpitation, nausea, drowsiness, tachycardia, blurred vision, mydriasis, hyperthermia, disorientation, vomiting, agitation, delirium, urine retention, hypertension and coma. Three patients were hospitalized for 2-3 days. Thirteen persons received supportive fluid therapy. One patient did not receive medical therapy, he induced vomiting and drank a lot of water. Four patients presented with delirium/coma and 3 received physostigmine therapy with good response. One patient was intubated because of coma and respiratory depression. Three persons needed Foley catheterization for urine retention or coma status. One patient had a complication of urinary tract infection and antibiotic management. All patients recovered with no sequelae.  相似文献   
49.
Transgenic mouse models and human neurodegenerative disorders   总被引:1,自引:0,他引:1  
  相似文献   
50.
控制性超排卵长、短方案在IVF-ET中的疗效比较   总被引:1,自引:0,他引:1  
目的:比较促性腺激素释放激素激动剂(GnRHa)长、短方案控制性超排卵在体外受精-胚胎移植(IVF-ET)中的疗效。方法:将2001年7月-2002年4月因双侧输卵管梗阻IVF-ET的患者100人随机分为长方案组(50人)和短方案组(50人)进行超排卵。长方案组从使用促性腺激素(Gn)治疗前1月经周期黄体期(月经21天)使用GnRHa 0.3mg/d,至垂体完全降调节后加用Gn;短方案组从月经周期第2天开始用GnRHa0.1mg/d,同时加用Gn。当患者有3个以上卵泡直径>18mm时肌肉注射人绒毛膜促性腺激素(HCG),36小时后取卵行IVF,取卵48小时后行ET。结果:两组患者平均获卵数、受精率、卵裂率、优质胚胎率、移植胚胎数、临床妊娠率、胚胎种植率及流产率差异无显著性。而两者的Gn使用量有差别,短方案组少于长方案组,两组差异有显著性。两组用Gn第7天雌激素水平不同,短方案组明显高于长方案组,两者差异有显著性。结论:GnRHa长、短方案在IVF-ET中控制性超排卵效果相同,但所需Gn数量不同。  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