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   129002篇
  免费   11261篇
  国内免费   6691篇
耳鼻咽喉   1225篇
儿科学   1962篇
妇产科学   2931篇
基础医学   13469篇
口腔科学   2679篇
临床医学   16039篇
内科学   20187篇
皮肤病学   1593篇
神经病学   6402篇
特种医学   4211篇
外国民族医学   40篇
外科学   13353篇
综合类   19320篇
现状与发展   20篇
一般理论   18篇
预防医学   9435篇
眼科学   3449篇
药学   13515篇
  115篇
中国医学   6565篇
肿瘤学   10426篇
  2024年   347篇
  2023年   1716篇
  2022年   4018篇
  2021年   5457篇
  2020年   4061篇
  2019年   3705篇
  2018年   3943篇
  2017年   3708篇
  2016年   3310篇
  2015年   5240篇
  2014年   6736篇
  2013年   6949篇
  2012年   10130篇
  2011年   10874篇
  2010年   7489篇
  2009年   6158篇
  2008年   7784篇
  2007年   7775篇
  2006年   7320篇
  2005年   6691篇
  2004年   4842篇
  2003年   4402篇
  2002年   3652篇
  2001年   3095篇
  2000年   2847篇
  1999年   2644篇
  1998年   1326篇
  1997年   1233篇
  1996年   993篇
  1995年   962篇
  1994年   889篇
  1993年   514篇
  1992年   894篇
  1991年   804篇
  1990年   674篇
  1989年   575篇
  1988年   535篇
  1987年   453篇
  1986年   357篇
  1985年   286篇
  1984年   184篇
  1983年   167篇
  1982年   95篇
  1981年   94篇
  1979年   140篇
  1978年   111篇
  1977年   83篇
  1974年   94篇
  1973年   72篇
  1972年   87篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Background and Aim Results after curative liver resection in hepatocellular carcinoma are unsatisfactory with regard to high postoperative intrahepatic recurrence and liver failure. This study evaluates telomerase activity in liver with and without tumor as a predictor of recurrence and survival. Materials and Methods Liver tissue with and without tumor from 53 hepatocellular carcinoma patients receiving curative resection during the period of 1998–2000 was used for detecting telomerase activity by PCR-ELISA. Clinicopathological data were compared to identify predictors of recurrence and survival. Results Telomerase activity was detected in 98% of liver tissue with tumor and 70% liver tissue without. Telomerase activity in cancerous liver correlated significantly with HCV infection (P = 0.012) and cirrhotic change in liver parenchyma (P = 0.006). Telomerase activity in non-cancerous liver correlated with high serum AFP level (P = 0.002). The telomerase activity of liver tissue with and without tumor is significant higher in patients with recurrence than in those without recurrence, 413.7 ± 100.5 versus 110.8 ± 32.7, P = 0.006, and 34.7 ± 14.2 versus 4.2 ± 1.4, P = 0.039. Recurrence could be predicted by abnormally high tumor telomerase activity (P = 0.026) or by advanced TNM stage (P = 0.001). TNM stage or high serum ALT level could predict multinodular intrahepatic recurrence (P = 0.028 and P = 0.030). High serum AFP combined with high telomerase activity in liver without tumor had a significant ability to predict poor survival (OR: 11.19, CI: 1.95–64.12, P = 0.007). Conclusion Tumor telomerase is an independent predictor of recurrence. Simultaneous high remnant liver telomerase and high serum AFP is a strong negative predictor of survival.  相似文献   
982.
Background Fine-needle aspiration biopsy (FNAB) and frozen-section analysis of managing solitary thyroid nodules continue to generate considerable controversy. Methods This study was a retrospective review of 619 patients with solitary thyroid nodules who underwent thyroidectomy. Results Of 540 FNABs, 35 (6.5%) were positive for malignancy, 276 (51.1%) were benign, and 229 (42.4%) were suspicious. Only 5.1% were false negative, and 11.4% were false positive. Diagnostic FNAB sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy for malignancy were 86.1%, 59.7%, 33.0%, 94.9%, and 64.6%, respectively. Of 569 patients analyzed by frozen section, diagnosis was deferred in 86 (15.1%) patients, and results were positive for malignancy in 92 (16.2%) and benign in 391 (68.7%). No false-positive results were noted, but 2.3% (391) were false negative. Of 86 deferred frozen sections, 11 (12.8%) patients had malignant tumors confirmed by permanent section. Diagnostic frozen-section sensitivity, specificity, PPV, NPV, and accuracy for carcinoma were 82.1%, 100%, 100%, 95.8%, and 96.5%, respectively. Sensitivity, specificity, PPV, NPV, and accuracy for frozen-section analysis for diagnosis of carcinoma in patients with suspicious FNAB were 83.9%, 100%, 100%, 94.9%, and 96.0%, respectively. Conclusions FNAB is a sensitive diagnostic modality in selecting patients who require surgery. Routine use of frozen-section analysis is unwarranted for benign FNAB results. Frozen section is specific and cost-effective in determining the extent of surgery in patients with suspicious or malignant FNABs.  相似文献   
983.
984.
目的观察美托康注射液与都可喜联合治疗椎基底动脉供血不足的临床疗效。方法随机将87例病人分为治疗组(45例)和对照组(42例),治疗组应用美托康注射液250ml静滴,1a/d,同时加服都可喜1片,2次/d;对照组应用复方丹参注射液30m1加入5%葡萄糖注射液500ml静滴,1次/d;两组均连用10d,其余常规治疗相同。结果治疗组痊愈26例,有效18例,总有效率98%;对照组痊愈15例,有效24例,总有效率93%。治疗组疗效优于对照组(P〈0.05)。结论美托康注射液与都可喜联合治疗椎基底动脉供血不足有良好临床疗效,可于临床广泛应用。  相似文献   
985.
The impact of synapsins on synaptic plasticity and cognitive behaviors   总被引:1,自引:0,他引:1  
Synapsins are a family of phosphoproteins specifically associated with the cytoplasmic surface of the synaptic vesicle membrane, appearing to regulate neurotransmitter release, the formation and maintenance of synaptic contacts. They could induce the change of the synaptic plasticity to regulate various adaptation reactions, and change the cognitive behaviors. So we presume that if some cognitive behavior are damaged, synapsins would be changed as well. This gives us a new recognition of better diagnosis and therapy of cognitive disorder desease.  相似文献   
986.
目的观察中成药天智颗粒对血管性痴呆大鼠学习记忆能力和神经前体细胞与星形胶质细胞增殖水平的影响。方法老年雄性SD大鼠192只,随机分为治疗组、模型组、假手术组和正常对照组,每组48只。治疗组、模型组采用双侧颈总动脉结扎方法建立血管性痴呆大鼠模型,于造模60d后治疗组大鼠应用天智颗粒5g/(kg·d)治疗30d。采用三等分Y型电迷宫测试各组大鼠的学习记忆能力,应用免疫组织化学尿嘧啶脱氧核苷(BrdU)和胶质纤维酸性蛋白(GFAP)染色方法标记并观察神经细胞增殖变化,以比较各组大鼠学习记忆能力和神经细胞增殖的变化规律和差异。结果与正常对照组相比,假手术组大鼠的学习记忆能力和免疫组织化学检测结果无明显变化。经天智颗粒治疗30d后,治疗组大鼠学习记忆能力明显改善,与模型组相比差异有统计学意义(P<0.05),BrdU阳性细胞显著增加(P<0.05),而星形胶质细胞明显减少(P<0.05);但与正常对照组相比,其学习记忆能力、BrdU阳性细胞和星形胶质细胞数量仍未恢复至正常水平(P<0.05)。结论天智颗粒可通过促进神经前体细胞的增殖而抑制星形胶质细胞的增殖,从而改善血管性痴呆大鼠的学习记忆能力。  相似文献   
987.
Lin EJ  Young D  Baer K  Herzog H  During MJ 《Epilepsia》2006,47(4):773-780
PURPOSE: Neuropeptide Y (NPY) has been shown to modulate seizure activities. To provide further understanding of the involvement of two of the most abundantly expressed NPY receptors, Y1 and Y2, we assessed the effect of Y1 and Y2 gene deletion on systemic kainic acid-induced seizures. We also examined the effect of rAAV-mediated hippocampal NPY overexpression on seizure susceptibility in these receptor knockout mice. METHODS: Recombinant adeno-associated viral vector overexpressing NPY (rAAV-NPY) or an empty vector control (rAAV-Empty) was injected into the hippocampus of adult C57BL/6-129/SvJ wild-type male mice and mice deficient of Y1 or Y2 receptors on the same background. Four weeks after vector injection, mice were subjected to systemic kainic acid-induced seizures, and the seizure behaviors were scored. RESULTS: The rAAV-mediated hippocampal overexpression of NPY led to a twofold reduction in seizures induced by systemic kainic acid in wild-type mice and Y1 receptor knockout mice but not in mice deficient of Y2 receptors. A differential action by the receptors was observed in the seizure-induced mortality rate, with increased fatality in Y2-/- mice. In addition, although NPY overexpression did not significantly affect the mortality rate in Y2-/- and wild-type mice, it abolished KA-induced mortality in Y1-/-mice. CONCLUSIONS: This study shows for the first time an altered susceptibility to chemically induced seizures in Y1 and Y2 knockout mice and demonstrates a differential seizure modulation mediated by these receptors via a genetic approach.  相似文献   
988.
目的 建立2型糖尿病大鼠动物模型,探讨晚期糖基化终末产物及其受体在实验性2型糖尿病大鼠种植体骨整合过程中的变化及表达.方法 45只3个月龄SD健康雄性大鼠,将大鼠随机分为糖尿病模型组25只和正常对照组20只.首先建立2型糖尿病大鼠模型,建模成功后将模型大鼠随机分为DM组和DM种植组,每组10只.将20只正常组大鼠随机分为正常对照组和正常种植组,每组10只.分别于正常种植组和DM种植组的胫骨近骺端植入纯钛种植体,植入10周后于下腔静脉采血,保存所采集标本,用RF-5301PC型荧光分光光度计测定血清中AGEs含量的变化.硬组织标本采用不带种植体脱钙切片,以正常组为对照,HE染色后用免疫组织化学方法检测种植体周围RAGE的表达.结果 10周后,DM种植组和DM组与正常对照组和正常种植组相比,血清中AGEs的变化差异有统计学意义(P <0.05),正常种植组和DM种植组与正常对照组的种植体周围骨组织RAGE表达比较,差异均有统计学意义(P <0.05);DM种植组与DM组比较,差异亦有统计学意义(P <0.05).结论 种植体骨组织愈合过程中AGEs和RAGE相互作用是影响2型糖尿病种植体骨结合的机制之一.  相似文献   
989.
Alzheimer's disease (AD), one of the most dreaded neurodegenerative disorders, is characterized by cortical and cerebrovascular amyloid β peptide (Aβ) deposits, neurofibrillary tangles, chronic inflammation, and neuronal loss. Increased bone fracture rates and reduced bone density are commonly observed in patients with AD, suggesting one or more common denominators between both disorders. However, very few studies are available that have addressed this issue. Here, we present evidence for a function of amyloid precursor protein (APP) and Aβ in regulating osteoclast (OC) differentiation in vitro and in vivo. Tg2576 mice, which express the Swedish mutation of APP (APPswe) under the control of a prion promoter, 1 exhibit biphasic effects on OC activation, with an increase of OCs in younger mice (< 4 months old), but a decrease in older Tg2576 mice (> 4 months old). The increase of OCs in young Tg2576 mice appears to be mediated by Aβ oligomers and receptor for advanced glycation end products (RAGE) expression in bone marrow macrophages (BMMs). However, the decrease of OC formation and activity in older Tg2576 mice may be due to the increase of soluble rage (sRAGE) in aged Tg2576 mice, an inhibitor of RANKL‐induced osteoclastogenesis. These results suggest an unexpected function of APPswe/Aβ, reveal a mechanism underlying altered bone remodeling in AD patients, and implicate APP/Aβ and RAGE as common denominators for both AD and osteoporosis. © 2011 American Society for Bone and Mineral Research.  相似文献   
990.
Objectives: To investigate how hyaluronic acid (HA) affects nerve growth factor (NGF) production and bladder overactivity in a cyclophosphamide (CYP)‐induced cystitis rat model. Methods: Female Sprague–Dawley rats received three intermittent intraperitoneal injections of CYP (75 mg/kg) or saline. Before or after CYP injection, HA was given intravesically and urine NGF was checked with creatinine correction. Bladder function was evaluated by cystometrograms under Zoletil anesthesia. Furthermore, the effect of HA was counteracted with hyaluronidase (HYAL). Bladder structural change was compared among groups with trichrome stain. Results: The intercontraction interval (ICI) significantly decreased in CYP‐injected rats in comparison to the saline‐injected controls. In the CYP‐injected groups, bladder HA instillation significantly increased the ICI, but did not change the maximum voiding pressure in comparison to the saline instillation. NGF production significantly increased in CYP‐injected rats, but decreased significantly with HA treatment. Treatment with HA had a more significant effect on urine NGF and the use of HYAL would eliminate this effect. Specific staining showed mucosa swelling after CYP treatment. Little HA coating on bladder mucosa could be found in HA‐treated rats. Conclusions: Present findings raise the possibility that HA could be an effective treatment for CYP‐related bladder overactivity through the involvement of NGF signaling.  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