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   214351篇
  免费   18789篇
  国内免费   4696篇
耳鼻咽喉   3335篇
儿科学   4139篇
妇产科学   3587篇
基础医学   16799篇
口腔科学   7256篇
临床医学   20096篇
内科学   20656篇
皮肤病学   2394篇
神经病学   10581篇
特种医学   6131篇
外国民族医学   12篇
外科学   22094篇
综合类   34618篇
现状与发展   10篇
一般理论   24篇
预防医学   27904篇
眼科学   2279篇
药学   20533篇
  339篇
中国医学   25898篇
肿瘤学   9151篇
  2024年   806篇
  2023年   4130篇
  2022年   7565篇
  2021年   10519篇
  2020年   10181篇
  2019年   11509篇
  2018年   10210篇
  2017年   8836篇
  2016年   7947篇
  2015年   7460篇
  2014年   14705篇
  2013年   14827篇
  2012年   13105篇
  2011年   14033篇
  2010年   11295篇
  2009年   9735篇
  2008年   8967篇
  2007年   9094篇
  2006年   7740篇
  2005年   6555篇
  2004年   5402篇
  2003年   4805篇
  2002年   3727篇
  2001年   3075篇
  2000年   2751篇
  1999年   2228篇
  1998年   1782篇
  1997年   1618篇
  1996年   1294篇
  1995年   1237篇
  1994年   1138篇
  1993年   1007篇
  1992年   908篇
  1991年   835篇
  1990年   742篇
  1989年   702篇
  1988年   665篇
  1987年   594篇
  1986年   541篇
  1985年   1789篇
  1984年   2059篇
  1983年   1298篇
  1982年   1716篇
  1981年   1191篇
  1980年   1018篇
  1979年   907篇
  1978年   743篇
  1977年   557篇
  1976年   702篇
  1975年   477篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
ADM对LNNA诱导的高血压心肌肥大的作用及机制探讨   总被引:1,自引:0,他引:1  
本工作在LNNA经慢性NO封闭诱导的大鼠高血压心肌肥大模型上研究了ADM对其心肌肥大和M5LV钠一钙交换功能损伤的作用。结果:一、较之对照组,LNNA组MAO和LVI分别增加57.4%和18。0%(P<0.01).其MSLV经钠-钙交换蛋白的钙摄取则明显降低(P<0.01或0.05):二.ADM组的MAP和LVI则分别较LNNA组降低19.6%和11.3%,而其MSLV的钙摄取则高于LNNA组(P<0.05);三、对照组、LNNA组和ADM组钠-钙交换蛋白摄取钙的Km值分别为7.51.7.04和7.57uM,而Vmax则分别为6.38,4.32和5.45nmol/。mgpr/min。表明:ADM能拮抗LNNA诱导的高血压心肌肥大和减轻其MSllV钠-钙交换功能的损伤,并且后者可能是ADM拮抗心肌肥大的机制之一。揭示内源性ADM的诱导和外源性给予ADM可能有预防和/或延缓高血压心肌肥大发生发展的作用。  相似文献   
992.
槐耳的研制及临床应用   总被引:4,自引:0,他引:4  
槐耳是一种人药1500余年但已湮没300余年的重要药用真菌。它和其原料药材槐耳菌质近年来已被批准为中药国家一类新药,就有关槐耳的研制及其在肿瘤疾病方面的应用作一综述。  相似文献   
993.
Two recently discovered genes, the recombination activating genes 1 and 2 (RAG-1 and RAG-2), are necessary to perform variable (V), diversity (D), and joining (J) recombination. They synergistically activate VDJ recombination to generate immunocompetent lymphocytes. Disruption of either gene results in a maturation arrest at a very early B and T cell progenitor stage. Expression and downregulation of RAG's are closely associated with interleukin 7, sIgM and TCR-CD3 complex, respectively. Assessment of RAG mRNA expression is a valuable marker in identifying the genotypic maturation status of leukemias and lymphomas. Persistent RAG expression in otherwise mature lymphoid proliferations may explain puzzling biological and clinical observations such as multiple rearrangements in lymphomas with a mature phenotype. Lack of RAG expression in Hodgkin's disease with abundant Reed-Stern-berg cells is consistent with a mature phenotype of the latter. Availability of a anti-RAG-1 monoclonal antibody in the near future will facilitate RAG analysis of lymphomas.  相似文献   
994.
We report herein the case of a 70-year-old man in whom a chest wall implantation of adenocarcinoma of the lung at the drainage tube site was found 4 months after a right lower lobectomy with mediastinal lymph node dissection had been performed for adenocarcinoma of the right lower lobe. The lesion was successfully treated by tumor extirpation. We believe that tumor seeding to the chest wall occurred at the time of thoracotomy. To prevent such tumor seeding, the pleural cavity should be washed out routinely with a massive volume of physiological saline solution prior to closure of the chest wall.  相似文献   
995.
Background: We describe a technique of laparoscopic cecal ligation and puncture (CLP) in the rat analogous to open CLP which may facilitate the study of minimally invasive surgery (MIS) and peritonitis. Methods: Forty-four rats were randomized to either laparoscopic or open CLP and their 3-day mortality was recorded. Autopsies were performed for peritoneal fluid cultures, measurement of the length of ligated cecum, and scoring of the degree of cecal necrosis. Results: Laparoscopic CLP required slightly longer operating times compared to open CLP (average 15.6 vs 13.1 min, p= 0.002). Three-day postoperative mortality was 36.4% and 22.7% for open and laparoscopic CLP, respectively (p= NS). There were no differences in the length of ligated cecum or the cecal necrosis score between the open and laparoscopic CLP groups. Conclusion: Laparoscopic CLP is feasible and produces a fecal peritonitis with similar characteristics to those of traditional open CLP. Received: 3 July 1996/Accepted: 7 January 1997  相似文献   
996.
目的:探讨体外循环(cardiopulmonarybypass,CPB)术中采用低温洗涤红细胞肺保护液实施肺动脉灌注对肺的保护效果。方法:随机选取20例风湿性单纯二尖瓣病变合并中度肺动脉高压的患者,分为肺动脉灌注组和对照组(每组各10例)。灌注组在主动脉阻断后,经肺动脉根部间断灌注低温洗涤红细胞肺保护液,测定两组患者围术期的机械通气时间、肺血管阻力、白细胞比值(静脉血/动脉血)、肺循环血浆MDA含量。结果:体外循环术后灌注组机械通气时间显著低于对照组(P<0.05);各时点肺血管阻力、白细胞比值(静脉血/动脉血)、肺循环血浆MDA含量均显著低于对照组(P<0.01)。结论:低温洗涤红细胞肺保护液肺动脉灌注对体外循环术后肺损伤有明显的保护作用.  相似文献   
997.
A historical mortality study of a cohort of employees of a gold mining and refining company was carried out in Salsigne, France. A major goal of the study was to investigate the relationship between lung cancer mortality and exposure to arsenic, radon, silica, and other contaminants of the working environment. A twofold excess of lung cancer was found both among miners and smelters, mainly concentrated among workers who had experienced exposure to past levels of arsenic, radon, and silica. The consistency of the results in the mine and the refinery are suggestive of a carcinogenic risk from both soluble and insoluble arsenic, although the potential role of other factors cannot be dismissed. © 1994 Wiley-Liss, Inc.  相似文献   
998.
A new mutant, the Eisai hyperbilirubinemic (EHB) rat, shows no inherent expression of the canalicular isoform of the multidrug resistance protein (cMrp) in the liver. It has defective biliary secretion of organic anions such as bilirubin glucuronides, bromosulfophthalein (BSP), cysteinyl leukotrienes, glutathione (GSH) and bile acid sulfate and glucuronides. When rats were injected intravenously with CdCl2, biliary excretion of Cd over 30 min was 0.28% and 0.004% of the total dose in Sprague-Dawley (SD) and EHB rats, respectively. Six SD rats and five EHB rats were fed a diet containing Cd. Bile Cd was detected at the level of 2 ng/20 min in SD rats, but not in EHB rats. There was no significant difference of hepatic Cd concentration between SD and EHB rats. Furthermore, there were no significant differences of renal and intestinal Cd, and hepatic and renal metallothionein (MT) concentrations between the SD and EHB groups. Biliary excretion of reduced-GSH for 20 min was 1.3 ± 0.3 mg and 3.6 ± 0.9 μg in SD and EHB rats, respectively. Our results suggest that hepatobiliary excretion of exogenous Cd is mediated mainly via carrier transport, including a cMrp or GSH carrier, but that the lack of the transport pathway does not contribute to abnormal accumulation of Cd in the liver. Received: 12 August 1996 / Accepted 7 November 1996  相似文献   
999.
Previous study has shown that α2D-adrenoceptors are involved in modulation of peristalsis in the rat ileum. The aim of the present study was to determine the tissue location of α-adrenoceptors in the rat ileum by using a recently devised method. The pre-synaptic α-adrenoceptors were characterised by measuring the potencies of agonists to inhibit transmurally-evoked (1 ms pulses, 10 Hz, 8-10 s trains) contractions of the longitudinal and circular muscles and the affinities of antagonists. Post synaptic α-adrenoceptors were identified by screening agonists and antagonists in carbachol-contracted tissues. In the circular muscle the order of potencies for inhibiting transmurally-induced contraction was: clonidine ≥ oxymetazoline ≥ UK 14,304 ≥ guanfacine > talipexole > phenylephrine > azepexole. The potency ratios relative to clonidine correlated to those previously derived using the rat ileum peristaltic reflex preparation. Most of the α-adrenoceptor agonists, however, caused only small inhibitions of the longitudinal muscle contraction in response to transmural stimulation, except phenylephrine and azepexole. RX 821002, yohimbine, rauwolscine, BRL 44408, phentolamine, idazoxan, ARC 239, and prazosin inhibited the effect of clonidine on the circular muscle response with apparent pKB values best correlated with pKB or pKi values derived from the rat ileum peristaltic reflex preparation and other tissues known to have the α2D-subtype. The rank order of potencies at inhibiting carbachol-induced responses of both muscle layers was: phenylephrine ≥ oxymetazoline > clonidine ≥ talipexole > azepexole >> guanfacine. UK 14,304 was inactive up to 10 μM. The EC50 value of each agonist on the longitudinal muscle was not significantly different to the corresponding value on the circular muscle. Prazosin was more potent than yohimbine at inhibiting the relaxant effect of phenylephrine in both muscle layers of carbachol-contracted tissues. It is concluded that the recently identified α2D-adrenoceptors of the rat ileum are located on cholinergic neurons controlling circular muscle contraction. The study also demonstrated the presence of postsynaptic α1-adrenoceptors involved in mediating relaxation in both muscle layers. Received: 4 November 1996 / Accepted: 10 April 1997  相似文献   
1000.
天麻素对缺血再灌注神经细胞膜的保护作用   总被引:36,自引:0,他引:36  
用新生Wistar大鼠大脑皮层进行神经细胞培养 ,将培养 8d的神经细胞置于模拟“缺血”状态下 ,5h后神经细胞发生肿胀 ,胞内乳酸脱氢酶 (LDH)漏出增加 ,膜流动性下降、脂质过氧化(LPO)含量增加 ;将经过“缺血”损伤神经细胞置 1 8h模拟“再灌注” ,“再灌注”后细胞数目明显减少 ,LDH的漏出、膜流动性下降和LPO增加继续加重 ,说明细胞损伤进一步加重。经过天麻素孵育后的神经细胞“缺血”或“再灌注”后LDH的漏出及LPO含量明显低于损伤组 ,而膜流动性则明显高于损伤组。表明 :天麻素对体外培养神经细胞的缺血再灌注损伤有保护作用  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