首页 | 官方网站   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   992篇
  免费   88篇
  国内免费   23篇
医药卫生   1103篇
  2024年   10篇
  2023年   23篇
  2022年   37篇
  2021年   50篇
  2020年   16篇
  2019年   41篇
  2018年   32篇
  2017年   20篇
  2016年   31篇
  2015年   28篇
  2014年   52篇
  2013年   55篇
  2012年   45篇
  2011年   63篇
  2010年   32篇
  2009年   28篇
  2008年   27篇
  2007年   32篇
  2006年   33篇
  2005年   27篇
  2004年   28篇
  2003年   29篇
  2002年   26篇
  2001年   21篇
  2000年   19篇
  1999年   18篇
  1998年   8篇
  1997年   8篇
  1996年   5篇
  1994年   5篇
  1993年   8篇
  1992年   17篇
  1991年   26篇
  1990年   25篇
  1989年   6篇
  1988年   21篇
  1987年   10篇
  1986年   10篇
  1985年   18篇
  1984年   7篇
  1983年   13篇
  1982年   10篇
  1981年   10篇
  1979年   11篇
  1977年   7篇
  1974年   5篇
  1971年   8篇
  1970年   6篇
  1968年   5篇
  1967年   6篇
排序方式: 共有1103条查询结果,搜索用时 15 毫秒
1.
目的总结75例不同病因引起脑积水的3种分流方法,以评价其临床疗效。方法分析75例脑积水形成的病因手术方法、手术结果、术后并发症等。结果除颅内肿瘤(5例)及术后癫痫致颅内出血(2例)共死亡7例外,手术疗效满意。但术后并发症以脑室心房分流术及脑室腹腔分流术后分流管堵塞的发生率较高。结论根据不同手术指征,选择不同分流方法,改进分流管,可减少手术损伤及术后分流管堵塞引流不畅等并发症。  相似文献   
2.
Cholinergic amacrine cells of the chicken retina were detected by immunohistochemistry using an antiserum against affinity-purified chicken choline acetyltransferase. Three populations of cells were detected: type I cholinergic amacrine cells had cell bodies on the border of the inner nuclear and inner plexiform layers and formed a prominent laminar band in sublamina 2 of the inner plexiform layer, while type II cholinergic amacrine cells had cell bodies in the ganglion cell layer, and formed a prominent laminar band in sublamina 4 of the inner plexiform layer. Type III cholinergic amacrine cell bodies were located towards the middle of the inner nuclear layer, and their processes were more diffusely distributed in sublaminas 1 and 3-5 of the inner plexiform layer. Type I and type II cells were present at densities of over 7000 cells/mm2 in central areas declining to less than 2000 cells/mm2 in the temporal retinal periphery. The cells were organized locally in a non-random mosaic, with regularity indices ranging from 3 peripherally to over 5 centrally. Neither at the light nor electron microscopic levels was a lattice of cholinergic dendrites of the kind reported by Tauchi and Masland [J. Neurosci. 5, 2494-2501 (1985)] detectable. Within the two prominent dendritic plexuses, a major feature of the synaptic interactions of the type I and type II cholinergic cells was extensive synaptic interaction between cholinergic processes. Apart from this, there was little, if any, input to cholinergic processes from non-cholinergic amacrine cells, but there was input from bipolar cells. Output from the cholinergic amacrine cell processes was directed towards non-cholinergic amacrine cells as well as other cholinergic amacrine cells, and ganglion cells.  相似文献   
3.
Histological and histochemical analyses were performed on the anterior latissimus dorsi muscle (ALD, red muscle) and the posterior latissimus dorsi muscle (PLD, white muscle) in normal (line 412) and dystrophic chickens (line 413) from 19 day embryos to 6 weeks of age. PLD, the white muscle, in dystrophic chickens showed higher percentages of red and intermediate fibres than those of normal chickens during the early development of muscles. Increases of the oxidative enzyme activities and the numbers of NADH--TR formazan granules in the white fibres of PLD were already found at 1 week of age in dystrophic chicken. Fibre types, oxidative enzyme activities and NADH--TR formazan granules showed no differences in ALD between normal and dystrophic chickens. These results suggest that increases of oxidative enzyme activities and formazan granule numbers and incomplete fibre type differentiation in PLD of dystrophic chickens are early pathological processes in such birds.  相似文献   
4.
Summary. XC cells are highly susceptible to syncytium formation by infection of ecotropic murine leukemia viruses (MLVs) and by expression of their envelope protein (Env). By this property, XC cells are widely used to determine titers of ecotropic MLVs. Number of plaques resulted from the syncytium formation in XC cells by ecotropic MLV infection is corresponding to number of the viral particles. XC cells had been established from a v-src-induced rat tumor. It has been reported that transformed cells are more sensitive to Mo-MLV-induced syncytium formation than non-transformed cells. To assess whether the transformation by v-src oncogene in XC cells is involved in the high sensitivity to ecotropic MLV-induced syncytium formation, XC cells were treated with genistein, a protein tyrosine kinase inhibitor. Genistein suppressed the syncytium formation between XC cells and ecotropic Env-expressing 293T cells. This result indicates that protein tyrosine kinase activity is associated with the high sensitivity of XC cells to ecotropic Env-induced syncytium formation.Received January 8, 2003; accepted May 26, 2003  相似文献   
5.
6.
E. coli was found to grow anaerobically on lactate in the presence of trimethylamine N-oxide (TMANO), reducing it to trimethylamine. Anaerobic growth on glucose was promoted in the presence of TMANO. When a culture grown in complex medium was transferred to defined medium, growth on glucose and ammonia took place in the presence of TMANO after consumption of complex nutrients introduced with the preculture, in contrast to growth in nitrate respiration. The amounts of ethanol, succinate, and lactate among the fermentation products were decreased and that of acetate was increased in the presence of TMANO. Formate generation was much reduced at pH 7.4, whereas stoichiometric formation of formate was observed in the absence of TMANO. Cells grown anaerobically in the presence of TMANO had a higher activity of amine N-oxide reductase than cells grown under other conditions. The content of cytochrome-558 was elevated in the presence of TMANO during growth in complex medium. Cytochrome c-552 found in cells grown in diluted complex medium or defined medium in the presence of TMANO was oxidized by TMANO in cell extracts. The molar growth yield on glucose was higher in the presence of TMANO than in its absence and lower than that in the presence of nitrate.  相似文献   
7.
鼻腔、咽部非霍奇金氏淋巴瘤   总被引:2,自引:0,他引:2  
目的 :探讨鼻腔、咽部非霍奇金氏淋巴瘤 ( NHL)的临床特征、诊断要点及误诊原因。方法 :对1 986年~ 1 996年住院的 2 4例鼻腔、咽部非霍奇金氏淋巴瘤的患者作一回顾性分析。结果 :2 4例临床表现差异较大 ,缺乏特征性的表现。首次诊断 NHL6例 ,其余 1 8例初诊时诊断 :慢性鼻炎 8例 ,恶性肉芽肿3例 ,鼻息肉 2例 ,鼻中隔粘膜肥厚 2例 ,扁桃体炎 2例 ,慢性咽炎 1例。 2 4例均经病理切片及免疫组化确诊。结论 :鼻腔、咽部非霍奇金氏淋巴瘤临床表现复杂 ,缺乏特征性 ,早期易误诊。提高临床医师对本病的认识 ,反复活检及免疫组化等方法有利于本病的确诊。  相似文献   
8.
STUDY OBJECTIVE--Intracoronary or intravenous adenosine during reperfusion in combination with lignocaine may attenuate "reperfusion injury" and limit myocardial infarct size in the canine heart. The aim of this study was to test whether intravenous adenosine also protects myocardium in the rabbit heart, which lacks xanthine oxidase and significant coronary collaterals in contrast to the canine heart. DESIGN--Five groups of rabbits underwent a 30 min occlusion of the circumflex coronary artery, followed by reperfusion. In adenosine treated groups, either a high dose of adenosine (0.37 mg.kg-1.min-1) with lignocaine treatment (5 mg intravenously 1 min before coronary occlusion and before reperfusion) or a low dose (0.15 mg.kg-1.min-1) of adenosine with or without lignocaine was infused for 60 min starting 5 min before the onset of reperfusion. Group 1 was untreated, while group 2 received a high dose of adenosine with lignocaine. These groups were reperfused for 3 h. Group 3 was untreated, group 4 received a low dose of adenosine, and group 5 a low dose of adenosine and lignocaine. These groups were reperfused for 72 h. EXPERIMENTAL MATERIAL--60 anaesthetised open chest rabbits were used. Groups 1 and 2 were killed after 3 h coronary reperfusion. Groups 3, 4, and 5 recovered from surgery for 72 h and were then killed for further study. MEASUREMENTS AND MAIN RESULTS--The high dose of adenosine reduced mean blood pressure to 44% of baseline value and diminished reactive hyperaemia in the area at risk by "coronary steal". The low dose of adenosine did not significantly alter systemic blood pressure or heart rate. Infarct size did not differ between groups 1 and 2, at 39.7(SD 20.1)% of area at risk v 33.2(15.9)% (by tetrazolium staining), nor between groups 3, 4, and 5: 50.3(12.6)% v 52.7(15.6)% v 47.8(9.3)% (by histology). CONCLUSION--Neither a high dose nor a low dose of adenosine limited myocardial infarct size in the rabbit heart even when adenosine was combined with lignocaine treatment.  相似文献   
9.
Cancer‐associated fibroblasts (CAFs) are reportedly involved in invasion and metastasis in several types of cancer, including gastric cancer (GC), through the stimulation of CXCL12/CXCR4 signaling. However, the mechanisms underlying these tumor‐promoting effects are not well understood, which limits the potential to develop therapeutic targets against CAF‐mediated CXCL12/CXCR4 signaling. CXCL12 expression was analyzed in resected GC tissues from 110 patients by immunohistochemistry (IHC). We established primary cultures of normal fibroblasts (NFs) and CAFs from the GC tissues and examined the functional differences between these primary fibroblasts using co‐culture assays with GC cell lines. We evaluated the efficacy of a CXCR4 antagonist (AMD3100) and a FAK inhibitor (PF‐573,228) on the invasive ability of GC cells. High CXCL12 expression levels were significantly associated with larger tumor size, increased tumor depth, lymphatic invasion and poor prognosis in GC. CXCL12/CXCR4 activation by CAFs mediated integrin β1 clustering at the cell surface and promoted the invasive ability of GC cells. Notably, AMD3100 was more efficient than PF‐573,228 at inhibiting GC cell invasion through the suppression of integrin β1/FAK signaling. These results suggest that CXCL12 derived from CAFs promotes GC cell invasion by enhancing the clustering of integrin β1 in GC cells, resulting in GC progression. Taken together, the inhibition of CXCL12/CXCR4 signaling in GC cells may be a promising therapeutic strategy against GC cell invasion.  相似文献   
10.
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-23

京公网安备 11010802026262号