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   28454篇
  免费   3804篇
  国内免费   2082篇
耳鼻咽喉   188篇
儿科学   348篇
妇产科学   269篇
基础医学   3131篇
口腔科学   646篇
临床医学   4052篇
内科学   3867篇
皮肤病学   342篇
神经病学   1426篇
特种医学   1066篇
外国民族医学   23篇
外科学   2874篇
综合类   4985篇
现状与发展   6篇
一般理论   3篇
预防医学   2557篇
眼科学   796篇
药学   3069篇
  51篇
中国医学   2347篇
肿瘤学   2294篇
  2024年   217篇
  2023年   771篇
  2022年   1838篇
  2021年   2192篇
  2020年   1695篇
  2019年   1354篇
  2018年   1308篇
  2017年   1271篇
  2016年   1171篇
  2015年   1687篇
  2014年   1915篇
  2013年   1611篇
  2012年   1998篇
  2011年   2233篇
  2010年   1477篇
  2009年   1269篇
  2008年   1418篇
  2007年   1311篇
  2006年   1223篇
  2005年   1155篇
  2004年   723篇
  2003年   693篇
  2002年   585篇
  2001年   417篇
  2000年   429篇
  1999年   450篇
  1998年   261篇
  1997年   282篇
  1996年   169篇
  1995年   177篇
  1994年   150篇
  1993年   91篇
  1992年   107篇
  1991年   90篇
  1990年   99篇
  1989年   74篇
  1988年   90篇
  1987年   55篇
  1986年   49篇
  1985年   32篇
  1984年   13篇
  1983年   15篇
  1981年   13篇
  1979年   19篇
  1977年   10篇
  1975年   11篇
  1974年   12篇
  1973年   15篇
  1969年   14篇
  1966年   9篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
EBV-associated nasopharyngeal cancer (NPC) occurs with high frequency in China and is a major cause of morbidity and mortality. To explore the potential use of adenovirus-mediated tumor suppressor p53 gene therapy In NPC, we first examined the in vitro effects of p53 introduced into the NPC cell lines RPMI 2650, Fadu and Detroit 562. p21(WAF1/CIP1) induction by chemotherapy was used as a functional assay which revealed that RPMI 2650 expresses wild-type p53 whereas Fadu and Detroit 562 encode mutant p53. Infection with p53-expressing adenovirus (Ad-p53) induced apoptosis and inhibited cell growth in all three NPC cell lines, regardless of the endogenous p53 status. Adenovirus infectivity was greatest in RPMI 2650 cells, with 100% of the cells expressing beta-galactosidase following Ad-LacZ infection using an MOI of 100, as compared to 20-30% infectivity with the other NPC lines. Using RPMI 2650 cells injected into nude mice, we developed an animal model for nasopharyngeal cancer. Established tumors (0.6-0.8 cm) were injected with 5x10(9) PFU Ad-LacZ, Ad-p53 or PBS in a 100 mu l volume. We found evidence for in vivo expression of beta-galactosidase or p53 and p21 up to two weeks following Ad-LacZ or Ad-p53 virus injection respectively. Objective regression of tumor size was observed at two weeks in 4/6 Ad-p53-treated tumors, but not in Ad-LacZ or PBS-treated tumors. The results provide an animal model for human nasopharyngeal cancer, and indicate a potential use of p53 in its therapy in vivo.  相似文献   
32.
The present study was undertaken to clarify whether a correlation exists between the hepatic ratio of the -phosphorous moiety of ATP (-ATP) to inorganic phosphate (Pi), measured by 31P nuclear magnetic resonance spectroscopy 1 h after the reestablishment of portal blood flow, and the survival rate of rats following liver transplantation. This ratio was compared with the arterial ketone body ratio [AKBR (acetoacetate/3-hydroxybutyrate)], which is accepted as a reliable indicator of liver viability. After the transplantation of fresh livers, the 1-week survival rate was 92% and the -ATP/Pi ratio was 64% of the normal level. When the liver grafts were subjected to warm ischemia for 25 min or 45 min prior to harvesting, the 1-week survival rate decreased to 43% and 0%, respectively, and the -ATP/Pi ratio dropped to 31% and 18% of the normal level, respectively. On the other hand, the AKBR was about 25% of the normal level after transplantation of fresh livers, while it was 37% and 48% after transplantation with 25 min and 45 min of warm ischemia, respectively. However, 4h after the reestablishment of portal blood flow, the AKBR correlated with the -ATP/Pi ratio in both the fresh graft group and the 45-min warm ischemic damage group. These results show that the -ATP/Pi ratio provides an accurate evaluation of a graft viability even at an extremely early stage following liver transplantation, and should prove useful for the early diagnosis of primary graft nonfunction after liver transplantation.  相似文献   
33.
目的 探讨脑积水的治疗方法和疗效。方法 62例均行侧脑室-腹腔分流术。脑室端从枕角穿入10cm接引流泵,再从皮下隧道引至上腹或左下腹放入腹腔。结果 1~4周后复查,症状完全消失56例,部分改善5例,无变化1例。57例复查CT示:52例脑室恢复正常,4例脑室较前缩小,1例无变化。堵管9例。低颅内压2例,硬膜下血肿2例,经保守治疗痊愈。49例随访1~8年,41例能正常工作学习,5例生活自理,1例植物生存,2例死亡。结论 明确诊断,掌握手术适应症及手术技巧是成功的关键。  相似文献   
34.
对不用贴附基质和生长因子情况下原代培养72h的人脐动脉内皮细胞(HUAEC)进行了透射电镜观察。电镜下HUAEC形态不规则,细胞器丰富。核周有散在的滑面内质网、粗面内质网及较多的线粒体,后者有些为板层状嵴,另一些为管泡状嵴。细胞膜下可见微管,胞质内有大量循同一方向排列的微丝。Weibel Palade小体内含涡旋状排列的细管。胞质内含丰富的糖原颗粒。细胞核内常染色质较多,异染色质主要分布于核膜下。有时可见处于无丝分裂状态的细胞,核已分裂为二,但二者间仍有核膜相连。内皮细胞间以紧密连接或中间连接的方式相连。以上结果表明:人脐动脉内皮细胞在体外培养条件下代谢功能旺盛,且具有参与脂类代谢的细胞器,细胞以无丝分裂方式增殖。  相似文献   
35.
评价低温保存板层角膜移植材料的效果。方法将15只人尸角膜分三组保存2年:4℃甘油脱水法,角膜液氮冷冻法,全眼球液氮冷冻法。并做透射电镜观察。结果第一组中,角膜胶原纤维排列紊乱,疏松,缺乏连续性,可见广纤维变性,纤维间可见极低电子密度灶。  相似文献   
36.
α-细辛脑对气管纤毛运动的影响   总被引:44,自引:0,他引:44  
目的:研究α-细辛脑对气管纤毛运动的影响,探讨其祛痰作用机理。方法:采用鸽子在体气管和家兔离体气管试验:设空白、阳性对照组及α-细辛脑高、中、低剂理组,以墨汁走距和运行速度作为气管纤毛运动指标,各试验组与空白对照组进行t检验。比较其组间差异。结果:给浅度麻醉的鸽子静脉注射α-细辛脑32mg/kg、16mg/kg、8mg/kg,墨汁走距分别为(1.17±0.12)cm,(1.15±0.17)cm和(  相似文献   
37.
目的 :研究 Opalescence脱色方法对色素牙脱色的疗效。方法 :将 Opalescence脱色剂涂于个别托模唇、颊侧内 ,病人每晚睡前刷牙后擦干牙面 ,戴上托模 ,晨起摘下冲洗干净 ,每天 1次 ,疗程一般为 2周 ,视疗效及患者反应增减用药时间。结果 :1 1 2例患者脱色治疗后氟斑牙的显效率( 80 .8%)高于四环素牙的显效率 ( 66.7%)。有 2 3例病人疗效不甚满意。结论 :应用 Opalescence脱色治疗活髓色素牙效果明显 ,脱色后牙体呈自然色泽 ,透明感好 ,特别适用于年龄较轻、无牙体缺损的氟斑牙及四环素牙的脱色。  相似文献   
38.
BACKGROUND: Tumor necrosis factor alpha (TNF-alpha) is an important mediator of septic shock. Endotoxin (LPS) signal transduction in human monocytes leads to activation of nuclear factor-kappa B (NF-kappaB) and TNF-alpha release. Previous studies have implicated activation of both protein kinase C (PKC) and protein tyrosine kinases (PTK) in LPS-induced NF-kappaB activation and TNF-alpha production. We hypothesized that inhibition of either PKC or PTK would decrease LPS-induced NF-kappaB DNA binding and TNF-alpha release in human monocytes. MATERIALS AND METHODS: Human monocytes were stimulated with PMA (50 ng/ml) alone or LPS (100 ng/ml) with and without a nonspecific serine/threonine protein kinase inhibitor staurosporine (Stauro), a specific pan-PKC inhibitor bisindolylmaleimide (Bis), or an inhibitor of PTK genistein (Gen). TNF-alpha release in culture supernatants was measured by an ELISA. NF-kappaB DNA binding was evaluated by electrophoretic mobility shift assay. RESULTS: LPS increased NF-kappaB DNA binding and TNF-alpha release in human monocytes. Nonspecific protein kinase inhibition inhibited NF-kappaB activation and TNF-alpha release, while specific PKC inhibition with Bis had no effect on LPS-induced NF-kappaB DNA binding or TNF-alpha release. PTK inhibition with Gen attenuated both LPS-induced NF-kappaB DNA binding and TNF-alpha production in human monocytes. Direct activation of PKC with PMA induced both NF-kappaB activation and TNF-alpha production by human monocytes. CONCLUSIONS: These results suggest that LPS-induced NF-kappaB activation and TNF-alpha release in human monocytes are independent of PKC activity. Furthermore, our results provide evidence that PTK plays a role in LPS-induced NF-kappaB activation and TNF-alpha release in human monocytes and thus could be a potential therapeutic target in inflammatory states.  相似文献   
39.
To understand further the role of trace elements in the pathogenesis of febrile convulsions, serum zinc (Zn), copper (Cu), magnesium (Mg) and CSF Zn, Cu, Mg and protein levels were measured by spectrometry in patients with febrile convulsion (n=19), bacterial meningitis (n=9), viral CNS infection (n=16) and in the control groupn=10) which consisted of children with signs of meningeal irritation due to upper respiratory tract infection but normal CSF findings. Samples were obtained within 6 h after admission to hospital. Mean serum and CSF Zn levels in the febrile convulsion group were significantly lower than in the other groups (for serum Zn: 0.66±0.03 mg/l vs 0.98±0.07 mg/l, 1.06±0.08 mg/l, 1.05±0.09 mg/lP<0.05; for CSF Zn: 22.96±1.62 g/l vs 75.47 ±6.9 g/l, 50.32±5.235 g/l, 39.85 ±2.81 g/lP<0.05). A linear relationship was established between serum Zn and CSF Zn levels (P<0.001). Mean CSF Zn, Cu and protein levels in the bacterial meningitis group were significantly higher than in the other groups (for CSF Cu 63.94±6.33 g/l vs 38.77±2.70 g/l, 35.84±3.48 g/l, 33.86±2.88 g/lP<0.05; for CSF protein 0.80 ± 0.12 g/l vs 0.22±0.02 g/l, 0.53±0.08 g/l, 0.19±0.01 g/lP<0.05). In children with meningitis, the elevation of the mean CSF Zn and Cu levels may result from the breakdown of the blood-brain barrier and subsequent leakage of trace elements and protein from serum to CSF. There was no significant difference between the four groups in terms of mean serum Mg and mean CSF Mg levels.Conclusion Serum and CSF Zn levels are decreased in children with febrile seizures. Zinc deprivation may play a role in the pathogenesis of febrile seizures.  相似文献   
40.
针灸按摩治疗慢性疲劳综合征研究进展   总被引:4,自引:2,他引:4  
王京京  孟宏  文娜  图娅 《中国针灸》2003,23(4):243-245
目的:通过综述近15年来针灸按摩治疗慢性疲劳综合征的文献,为临床治疗该病提供相应的参考资料。方法:共综合了盟篇相关文献的内容,从辨证分型、治疗方法、疗程、疗效4个方面进行了归纳总结。结论:针灸按摩治疗慢性疲劳综合征具有疗效肯定、无副作用、经济安全的特点。  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