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   1952924篇
  免费   131980篇
  国内免费   3838篇
耳鼻咽喉   28425篇
儿科学   58453篇
妇产科学   52732篇
基础医学   278256篇
口腔科学   57289篇
临床医学   165687篇
内科学   383015篇
皮肤病学   42555篇
神经病学   158054篇
特种医学   79181篇
外国民族医学   433篇
外科学   310844篇
综合类   36141篇
现状与发展   1篇
一般理论   542篇
预防医学   132904篇
眼科学   45382篇
药学   144870篇
  3篇
中国医学   4171篇
肿瘤学   109804篇
  2018年   21494篇
  2017年   17111篇
  2016年   19390篇
  2015年   21380篇
  2014年   28306篇
  2013年   43106篇
  2012年   58860篇
  2011年   61654篇
  2010年   36612篇
  2009年   33888篇
  2008年   59991篇
  2007年   63563篇
  2006年   64048篇
  2005年   63041篇
  2004年   60303篇
  2003年   58753篇
  2002年   57633篇
  2001年   95307篇
  2000年   99049篇
  1999年   82612篇
  1998年   21593篇
  1997年   19260篇
  1996年   18775篇
  1995年   17397篇
  1994年   16454篇
  1993年   15249篇
  1992年   61383篇
  1991年   58791篇
  1990年   57177篇
  1989年   55479篇
  1988年   50740篇
  1987年   49971篇
  1986年   47012篇
  1985年   45088篇
  1984年   33013篇
  1983年   28041篇
  1982年   15992篇
  1981年   13998篇
  1979年   30117篇
  1978年   20819篇
  1977年   17825篇
  1976年   16055篇
  1975年   17892篇
  1974年   21362篇
  1973年   20174篇
  1972年   19223篇
  1971年   17979篇
  1970年   17220篇
  1969年   16146篇
  1968年   15039篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
Endothelial cell seeding may improve the patency of synthetic vascular grafts provided that platelet reactivity of nonendothelialized sites is not increased. We have investigated if surface-adsorbed monoclonal antibodies directed against endothelial cell membrane proteins and against extracellular matrix proteins promote the adhesion and proliferation of cultured human endothelial cells, without causing platelet deposition at non-endothelialized sites. Adhesion of endothelial cells onto polyethylene coated with monoclonal antibodies directed against endothelial cell-specific membrane antigens, integrin receptors and glycoprotein CD31 was equal to or higher than adhesion onto fibronectin-coated polyethylene. Endothelial cells did not proliferate on these surface-adsorbed antibodies. However, pre-coating of polyethylene with mixtures of endothelial cell-specific monoclonal antibodies and monoclonal antibodies directed against fibronectin or von Willebrand factor, resulted in relatively high adhesion and optimal proliferation. Platelet reactivity of the polyethylene surface was found to significantly increase after adsorption of fibronectin, endothelial cell-specific monoclonal antibody or its Fc fragments. In contrast, adsorption of F(ab')2 fragments of endothelial cell-specific monoclonal antibody did not promote platelet deposition. Therefore, it is concluded that coating of vascular graft materials with mixtures of F(ab')2 fragments of monoclonal antibodies specifically directed against endothelial cells and against extracellular matrix proteins may be an effective way to both promote the growth of seeded endothelial cells and limit platelet-graft interaction.  相似文献   
992.
Acupuncture analgesia (AA) caused by low frequency stimulation of the acupuncture point (AP) was abolished by hypophysectomy and adrenalectomy. Termination of the AA producing pathway from the AP to the pituitary gland was in the medial hypothalamic arcuate nucleus (M-HARN). The origin of the descending pain inhibitory system associated with AA was in the posterior HARN (P-HARN). AA in the hypophysectomized rats, and enhanced neuronal activity in the P-HARN that were abolished during acupuncture stimulation, were both restored by intraperitoneal microinjection of 0.5 mg/kg morphine or 0.1 micrograms beta-endorphin into the P-HARN during acupuncture stimulation. Of the analgesia produced by dopamine or beta-endorphin injected into the P-HARN, that caused by beta-endorphin disappeared after denervation of the M-HARN. The P-HARN neurons that responded to acupuncture stimulation also responded to iontophoretic dopamine, but not to iontophoretic morphine nor ultramicroinjected beta-endorphin. The transmission between the M-HARN and P-HARN may be dopaminergic, and beta-endorphin might presynaptically modulate this transmission. Reduction of sodium ions may have been the reason for abolition of AA after adrenalectomy.  相似文献   
993.
Bronchoalveolar lavage fluid neutrophils were studied by the cytologic methods in 58 patients with chronic bronchitis, 63 ones with bronchiectasis, and 8 normal controls. The study included cytospectrophotometry of myeloperoxidase and alkaline phosphatase activity and estimation of active oxygen-producing cells in the NBT test. Neutrophilic functional activity was different in the patients with chronic bronchitis and bronchiectasis. Neutrophilic myeloperoxidase and alkaline phosphatase activities were lower in the patients with chronic bronchitis than in those with bronchiectasis, whereas the counts of cells active in the NBT test were low in both patient populations.  相似文献   
994.
995.
Intrahepatic shunt ratio was calculated from the fraction of the uptake constant and the blood background, analyzing the data of 99mTc-(Sn)-N-pyridoxyl-5-methyltryptophan (99mTc-PMT) hepatobiliary imaging by Rutland method. Shunt flow and total hepatic blood flow (THBF) were also calculated from the values for the effective hepatic blood flow (EHBF) estimated from the blood clearance technique. In 15 cases of normal volunteer, the average of the shunt ratio, shunt flow, and THBF were 18.4 +/- 5.4 (S.D.)%, 137.8 +/- 49 ml/min, and 753 +/- 83.2 ml/min, respectively. In 8 cases of chronic hepatitis, the values were 35.2 +/- 2.6%, 276 +/- 55.4 ml/min, and 794.1 +/- 119.4 ml/min, respectively. In 12 cases of liver cirrhosis, the values were 51.4 +/- 12.6%, 353.9 +/- 141.3 ml/min, and 685.6 +/- 174.8 ml/min, respectively. In cases of chronic hepatitis and liver cirrhosis, in comparison with normal cases, the values for the shunt ratio and shunt flow were significantly increased (p less than 0.001) and those for EHBF were significantly decreased (p less than 0.001), but those for THBF were not significantly altered. There was a significant inverse correlation between the shunt ratio and EHBF (r = -0.842) in all 35 cases. This method is considered to be useful for differential diagnosis, estimation of the grade of the diseases, and evaluation of pathophysiology of various diffuse liver diseases.  相似文献   
996.
This article describes the outcomes of a study involving family members of communication-impaired long-term care residents in a collaborative nursing/speech language pathology intervention designed to increase the residents' communication ability. Family members provided memorabilia and artifacts or produced audio or video tapes, for use in conjunction with a speech therapy enhancement program (STEP). Findings revealed that, despite a minimal improvement in speech ability, there was a dramatic increase in family members' satisfaction.  相似文献   
997.
Carotid sonography is being performed on more than 5,000 participants in the Cardiovascular Health Study, a prospective, multicenter study of cardiovascular disease in men and women aged 65 years and older. The sonographic methods used to examine and measure the extracranial carotid arteries are described. Initial validation studies were performed on 61 subjects with a mean age of 68.6 years. Analysis of within- and between-sonographer differences and between-reader differences were performed for selected variables. In general, the mean absolute differences for within- and between-sonographer comparisons were small, with even less variability between readers. Variability was less for the common carotid artery than for the internal carotid artery. These data suggest that carotid sonography is a reliable and reproducible method for use in the study of carotid atherosclerosis in population studies.  相似文献   
998.
A 43-year-old woman suffered a blast-type injury to the head and neck. She subsequently developed bilateral internal carotid artery occlusion and bilateral anterior cerebral artery infarction not demonstrated by magnetic resonance imaging scan 24 hours after the explosion, but confirmed by a second scan 8 days after the explosion. In patients with blast-type injury to the head and neck who develop coma with a nonfocal neurological exam, the possibility of bilateral carotid artery occlusion and bilateral ischemic infarction should be considered.  相似文献   
999.
1000.
Balloons     
F Robicsek 《Chest》1989,95(4):936-937
  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