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   394370篇
  免费   36739篇
  国内免费   27506篇
耳鼻咽喉   3148篇
儿科学   5126篇
妇产科学   4336篇
基础医学   42754篇
口腔科学   6506篇
临床医学   55196篇
内科学   52752篇
皮肤病学   4322篇
神经病学   19010篇
特种医学   14473篇
外国民族医学   225篇
外科学   35010篇
综合类   74888篇
现状与发展   90篇
一般理论   31篇
预防医学   29517篇
眼科学   10953篇
药学   43049篇
  467篇
中国医学   26129篇
肿瘤学   30633篇
  2024年   1388篇
  2023年   5756篇
  2022年   15092篇
  2021年   19284篇
  2020年   15175篇
  2019年   12375篇
  2018年   12709篇
  2017年   12317篇
  2016年   11273篇
  2015年   17666篇
  2014年   22031篇
  2013年   20250篇
  2012年   29986篇
  2011年   33504篇
  2010年   22875篇
  2009年   18582篇
  2008年   22578篇
  2007年   22293篇
  2006年   21183篇
  2005年   20174篇
  2004年   13472篇
  2003年   13075篇
  2002年   10849篇
  2001年   9212篇
  2000年   8743篇
  1999年   8724篇
  1998年   5475篇
  1997年   5248篇
  1996年   4096篇
  1995年   3840篇
  1994年   3244篇
  1993年   2072篇
  1992年   2486篇
  1991年   2180篇
  1990年   1837篇
  1989年   1588篇
  1988年   1313篇
  1987年   1207篇
  1986年   985篇
  1985年   692篇
  1984年   373篇
  1983年   276篇
  1982年   147篇
  1981年   172篇
  1980年   118篇
  1979年   154篇
  1978年   73篇
  1977年   53篇
  1974年   42篇
  1972年   37篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
163.
本文报告了两例脊髓萎缩,并结合文献复习讨论了该病的好发部位、病因、临床表现、诊断和治疗。脊髓萎缩的病因多为继发性,也可为特发性。根据临床表现结合脊髓CT造影及MRI检查,可以明确诊断。  相似文献   
164.
肢体不同延长速度对局部血流量的影响   总被引:1,自引:1,他引:0  
本文报告20只兔胫骨以不同速度延长时用末梢微循环测定系统动态连续监测局部血流量变化的结果,发现一次延长>1 mm时,局部肌肉血流量开始急骤下降,恢复延长前血流量所需的时间>8 h。作者认为肢体的血管、肌肉等组织对1 mm/次/d延长速度有相当大的生物适应性。延长速度>1 mm/次/d易造成局部血流量大幅度减少。延长肢肌肉萎缩、肌力减弱可能与血流量减少有关。  相似文献   
165.
We describe here 9 patients with somatotroph adenomas associated with mild features of acromegaly and basal plasma GH levels in the normal range. In 5 women and 4 men, 26 to 61 yrs old, the diagnosis of prolactinoma or non-secreting pituitary adenoma had been previously made on the basis of amenorrhea-galactorrhea or tumoral symptoms. However, they had discrete signs of coarsening of the facial features and moderate but evolutive changes of hand and foot sizes. Basal GH levels were in the normal range (0.4 to 4.5 micrograms/l, N less than 5 micrograms/l) but unaffected by oral glucose and insulin tolerance tests while IGF-I concentrations were elevated in all the cases (range 1.7 to 5.8 U/ml, N: 0.37-1.41 U/ml). Plasma PRL concentrations were elevated in 5 patients (range 16 to 80 micrograms/l, N less than 13 micrograms/l in men and N less than 19 micrograms/l in women). The 9 patients had a macroadenoma with an extrasellar extension in 8 of them and all were operated on by the transsphenoidal route. Immunocytochemical studies demonstrated IRGH-cells in all the adenomas and IRPRL-cells in 5 of them. Electron microscopic analysis of 3 tumors showed that the secretory granules were sparse and the Golgi apparatus poorly developed. Molecular biology of 7 tumors showed the presence of small amounts of GH mRNA. This result was in agreement with the morphological aspect, suggesting a low rate of GH synthesis. Thanks to these different approaches the diagnosis of silent somatotroph adenoma should sometimes be reconsidered.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
166.
167.
从1例膀胱癌患者的癌组织培养中,分离得到2个不同生长特性的悬浮生长型细胞系,定名为TSB-90和TSB-91。在培养过程中,对其生物学特性进行了细胞和亚细胞水平的探讨,并进行了核型分析。发现2个细胞系核型的演化趋势有明显差异,生物学特性也不尽相同。这可能与膀胱癌组织中细胞的遗传异质性和分化程度有关。对其机制和细节有待进一步深入研究。  相似文献   
168.
抗体阴性重症肌无力发病与凝集素之间关系研究   总被引:2,自引:0,他引:2  
借助研究抗体阴性重症肌无力(MG)发病与凝集素之间的关系,以阐明其发病过程是否与凝集素有关。方法观察伴刀豆球蛋白A(ConA)和麦胚凝集素(Triticum)及其凝集素-糖复合物对TE671细胞表达的乙酰胆碱受体(AChR)功能的作用,以及对α-BuTx结合试验的影响。结果有两种凝集素对AChR功能均有抑制作用,抑制率(%)分别为54±14(n=11)和47±16(n=10),此作用可被3种糖抑制,抑制率(%)分别为:95±5(n=5)和84±8(n=5);69±6(n=4)和65±5(n=4);39±4(n=5)和57±6(n=5);ConA抑制α-BuTx结合试验,而Triticum则不能。结论Triticum和抗体阴性MG患者非IgG部分对AChR功能和α-BuTx结合试验的作用类同或一致,表明抗体阴性MG患者非IgG部分中的内源性Triticum样糖蛋白在其发病过程中起重要作用。  相似文献   
169.
BACKGROUND: It has been demonstrated that mild hypothermia has obvious protective effect on both whole and local cerebral ischemia. However, the definite mechanism is still unclear for the brain protection of mild hypothermia on cerebral edema, inhibiting inflammatory reaction, stabilizing blood brain barrier, etc. OBJECTIVE: To investigate the effect of mild hypothermia on the expression of vascular endothelial growth factor and the infarct volume after cerebral ischemia in rats, and analyze the brain protective mechanism of mild hypothermia. DESIGN: A randomized grouping and controlled animal trial. SETTING: Department of Neurology, People's Hospital of Yunyang Medical College. MATERIALS: Twenty adult male SD rats of clean degree, weighing (250±30) g, were provided by the animal experimental center, School of Medicine, Wuhan University. The kits for SP immunohistochemistry were purchased from Beijing Zhongshan Golden Bridge Biotechnology Co., Ltd. METHODS: The experiments were carried out in the laboratory of Department of Neurology, Renmen Hospital of Wuhan University from May to July 2005. ① The 20 rats were divided randomly into normal temperature group (n =10) and mild hypothermia group (n =10). Models of permanent middle cerebral artery occlusion were established with modified nylon suture embolization. The rats were assessed with the Longa standards: 0 point for without nerve dysfunction; 1 for mild neurological deficit (fore claws could no extend completely); 2 for moderate neurological deficit (circling towards the affected side); 3 for severe neurological deficit (tilting towards the affected side); 4 for coma and unconscious; 1-3 points represented that models were successfully established. The rats of the normal temperature group were fed at room temperature, and those in the mild hypothermia group were induced by hypothermia from 2 hours postoperatively, and the rectal temperature was kept at 34-35 ℃ for 72 hours. ② Measurement of infarct volume: All the rats were anesthetized by intraperitoneal injection overdose sodium pentobarbital 7 days postoperatively, and then the heads were cut down to harvest brain. The brain tissues were placed into -20 ℃ refrigerator for 20 minutes, coronal sections of 2 mm were prepared. The infarct sites were not stained, whereas normal brain tissues were stained as red. The infarct volumes were calculated by using MPLAS-500 multimedia color pathological image&&word analytical system. ③ Counting positive cells of vascular endothelial growth factor protein: The brains were harvested by cutting heads, then coronal sections of 2 mm were prepared. Routine dehydration, hyalinization, wax immersion and embedding were performed, then the detected with SP immunohistochemistry, the kits were purchased from Beijing Zhongshan Golden Bridge Biotechnology Co., Ltd. The cells whose cytoplasm was yellow-brown were positive ones, a single sample as a unit, peri-ischemic site and ischemic core were selected, and the corresponding sites in controlateral hemisphere were taken as controls. Five visual fields were selected from each site to be observed under microscope, the cells were counted, and the average number of positive cells was calculated in each group. The numbers of positive cells were determined with the image analytical apparatus. MAIN OUTCOME MEASURES: Number of the positive cells of vascular endothelial growth factor protein; Infarct volume of rat brain tissue. RESULTS: All the 20 rats were involved in the analysis of results. ① Number of positive cells of vascular endothelial growth factor protein in brain tissue: It was obviously lower in the mild hypothermia group than in the normal temperature group [(24.02±5.05), (36.07±2.69) cells/high power visual field, P < 0.01]. ② Comparison of infarct volume of brain tissue: After MCAO, it was obviously smaller in the mild hypothermia group than in the normal temperature group [(153.25±23.14), (253.45±36.21) mm3, P < 0.01]. CONCLUSION: Mild hypothermia can inhibit the expression of vascular endothelial growth factor and decrease the volume of cerebral infarction. The inhibition of mild hypothermia on the expression of vascular endothelial growth factor may be one of the brain protective mechanisms.  相似文献   
170.
Bal Ram Singh  Bilian Li  Dorothy Read 《Toxicon》1995,33(12):1541-1547
Botulinum and tetanus neurotoxins, produced by Clostridium botulinum and Clostridium tetani, respectively, are the most poisonous poisons known to mankind. Although botulinum and tetanus neurotoxins share several characteristics, such as similar mol. wts, similar macrostructure, virtually identical mode of action, and a strong amino acid sequence homology, the two neurotoxins differ in one very significant way; only botulinum neurotoxin is a food poison. Factors responsible for the food poisoning potential of botulinum neurotoxins seem to be a group of complexing proteins that are also produced by C. botulinum, and are known to associate with the neurotoxin. Translation products of nucleotide sequences upstream to the neurotoxin genes of serotypes A, B, C, D, E and F botulinum neurotoxin reveal the location of genes for one of the complexing proteins that could be transcribed as polycistronic mRNA to include neurotoxin sequences. No such protein seems to be present in C. tetani, suggesting that the lack of complexing proteins might be responsible for tetanus not being a food poison.  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