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   13176篇
  免费   829篇
  国内免费   352篇
耳鼻咽喉   49篇
儿科学   352篇
妇产科学   77篇
基础医学   1168篇
口腔科学   289篇
临床医学   2279篇
内科学   4799篇
皮肤病学   26篇
神经病学   259篇
特种医学   405篇
外科学   1178篇
综合类   1882篇
现状与发展   1篇
预防医学   212篇
眼科学   48篇
药学   848篇
  3篇
中国医学   400篇
肿瘤学   82篇
  2024年   16篇
  2023年   166篇
  2022年   315篇
  2021年   468篇
  2020年   432篇
  2019年   382篇
  2018年   403篇
  2017年   319篇
  2016年   374篇
  2015年   415篇
  2014年   892篇
  2013年   873篇
  2012年   769篇
  2011年   907篇
  2010年   778篇
  2009年   815篇
  2008年   774篇
  2007年   858篇
  2006年   748篇
  2005年   632篇
  2004年   499篇
  2003年   357篇
  2002年   292篇
  2001年   270篇
  2000年   224篇
  1999年   198篇
  1998年   127篇
  1997年   145篇
  1996年   96篇
  1995年   110篇
  1994年   79篇
  1993年   74篇
  1992年   70篇
  1991年   48篇
  1990年   45篇
  1989年   39篇
  1988年   34篇
  1987年   37篇
  1986年   29篇
  1985年   38篇
  1984年   37篇
  1983年   19篇
  1982年   26篇
  1980年   22篇
  1979年   14篇
  1978年   16篇
  1977年   13篇
  1976年   13篇
  1975年   15篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
51.
目的 :探讨比索洛尔对冠心病心力衰竭患者心室重塑及心功能的影响。方法 :冠心病心力衰竭患者 12 0例 ,左室射血分数≤ 45 % ,心功能 (NYHA)Ⅱ -Ⅳ级 ,常规治疗基础上随机分为比索洛尔治疗组和对照组。治疗 6个月 ,观察比索洛尔对心室重塑、心功能的影响。应用心脏彩色超声仪测定基线值及 1个月、3个月、6个月左室结构及功能指标变化。结果 :比索洛尔平均用量为 (7 5 0± 2 5 0 )mg/d ,经过 6个月治疗 ,比索洛尔治疗组症状和心功能改善 ,与对照组比较左室射血分数上升 [(4 9 2± 2 8) %VS(3 9 6± 3 6) % ,P <0 0 5 ] ,左室收缩末容积下降[(15 7 7± 42 6)mlVS(180 9± 3 9 6)ml] ;与基线比较左室舒张末容积下降 (P <0 0 5 )。结论 :在强心、利尿、血管紧张素转化酶抑制剂基础上 ,应用比索洛尔能显著改善冠心病心力衰竭患者的心功能 ,改善心室重塑。长期应用可改善衰竭心脏心肌细胞的生物学效应 ,这种有益的作用在不同心功能级别间无显著性差异  相似文献   
52.
Moderate increases in ``classical' biochemical markers of bone turnover have been described only in some patients with Camurati–Engelmann disease. However, the determination of the following ``new' markers has not been previously performed: serum osteocalcin (BGP), bone alkaline phosphatase (BAP), carboxyterminal propeptide of type I procollagen (PICP), aminoterminal propeptide of type I procollagen (PINP), tartrate-resistant acid phosphatase (TRAP), telopeptide carboxyterminal of type I collagen (ICTP), urinary pyridinoline (PYR), crosslinked N-telopeptides of type I collagen (NTX), and Crosslaps (CL). Such a determination may improve the evaluation of the disease activity. To evaluate the usefulness of biochemical markers of bone turnover reflecting Camurati–Engelmann disease activity we measured the levels of all these markers in four affected patients. The results were compared with bone scintigraphic indices of disease activity. Except for PICP and TRAP, bone formation and resorption markers were abnormal in all patients and were related to bone scan indices of disease activity. Among the markers of bone formation PINP, BAP, and BGP showed the highest values, whereas NTX and CL were the most sensitive markers of bone resorption. These results suggest that the determination of NTX or CL, and PINP or either BAP and BGP, associated with bone scan evaluation, provides the best assessment of Camurati–Engelmann disease activity. Received: 14 June 1996 / Accepted: 31 December 1996  相似文献   
53.
转化生长因子-β在哮喘气道炎症与重塑中的作用   总被引:4,自引:0,他引:4       下载免费PDF全文
Transforming growth factor-β(TGF-β) was reported to be increased in asthma in some studies. Accumulation of TGF-β in airway promotes smooth muscle cell mitogenesis and hyperplasia, and in-duces fibroblast and myofibroblast and smooth muscle proliferation as well as increase in protein synthesis in connective tissue(such as collagen deposition on the reticular basement membrane). The autocrine induction of collagen expression by smooth muscle may contribute to the thickening of the reticular basement membrane, irre-versible f‘throsis and remodeling seen in the airways in some asthmatics. TGF-β is considered to be a major fi-brogenic cytokine. It can increase smooth muscle mass and lead to severe bronchial obstruction in an asthma at-tack.  相似文献   
54.
Objective To investigate the morphological changes of heart in viral myocarditis caused by repetitive infection of CVB3m. Methods 4-week-old mice were infected four times intraperitoneally with a timedependent dose and killed at the 10th, 30th and 60th day after the final infection respectively, then we examined the heart changes and collagen hyperplasia by HE, VG stain and 1HC. Results Heart damage appeared very serious at the tenth day, even there were small necrotic foci at the day of 30th, but we could not see any injury of heart 2 months later after final infection. Collagen turned up at the tenth day and there was much more collagen in heart and increased PCVA, CVF index at the sixtieth day. The 1HC of collagen demonstrated the collagen I hyperplasia was much obvious compared to collagen Ⅲ. Conclusion It strongly indicated that repetitive infection of CVB3m could lead to heart fibrosis and ventricular remodeling, which resulted in decreased systolic and diastolic function of heart.  相似文献   
55.
目的观察麝香酮对易卒中型肾血管性高血压大鼠(RHRSP)血浆内皮素(ET)和脑动脉结构改变的影响。方法雄性RHRSP自术后第9周始分成两组:高血压组(n=12)和麝香酮治疗组(n=12),并以年龄、性别、数量相同的正常假手术组作对照,测量收缩压(SBP)和血浆ET含量,显微镜下观察血管形态改变,计算机图像分析血管外径、中膜厚度、管腔内径、中膜面积和壁腔比。结果12周时麝香酮组的SBP、ET水平比高血压组低(P<0.05)。镜下观察发现麝香酮组血管形态损害比高血压组轻。麝香酮组血管外径、血管内径、管壁厚度均大于高血压组(P<0.05),壁腔比则小于高血压组(P<0.05)。大脑中动脉平滑肌细胞面积较高血压组大,但两者间差异无统计学意义(P>0.05)。结论麝香酮治疗可轻度降低RHRSP的SBP和血浆ET水平,并能一定程度上改善其血管重塑。  相似文献   
56.
目的本文利用离体结合在体实验探讨心肌营养素-1(CT-1)在高血压心室重塑中的作用。方法离体实验用160 mm Hg的高静水压刺激原代培养的心肌成纤维细胞,同时用心肌营养素-1的反义寡核苷酸进行干预。分别用MTT法检测心肌成纤维细胞的增殖,放免法检测血管紧张素Ⅱ的浓度,Western blotting检测CT-1蛋白的表达。以L-NAME诱导的一氧化氮缺乏性高血压大鼠作为在体实验模型。用卡托普利进行干预。12周后处死动物,取材观察心肌组织病理变化,检测心肌中血管紧张素Ⅱ及羟脯氨酸的浓度,同时检测心肌中CT-1的表达。结果高静水压能明显促使心肌成纤维细胞增殖,血管紧张素Ⅱ分泌增加,CT-1合成上调(光密度值1.56±0.24 vs 0.95±0.19,P<0.01),而CT-1的反义寡核苷酸能抑制高静水压诱导的细胞增殖和血管紧张素Ⅱ分泌。而进行在体实验的大鼠给予L-NAME后血压明显升高,心肌组织中血管紧张素Ⅱ和羟脯氨酸分泌增加,CT-1表达上调(光密度值1.79±0.21vs 1.02±0.12,P<0.01),经卡托普利干预后,与L-NAME组相比,血压明显下降,心肌组织中羟脯氨酸浓度降低,血管紧张素Ⅱ分泌减少,CT-1表达下调(1.12±0.15 vs 1.79±0.21,P<0.05)。结论从在体和离体实验证明CT-1在高血压心室重塑中发挥着重要的调节作用,且这一作用与肾素血管紧张素系统有关。  相似文献   
57.
A quantitative assessment of cross-sectional cortical bone remodeling in the femoral diaphysis following hip arthroplasty was made by direct in vitro measurements of cross-sectional geometric properties. We obtained eight femora from four female cadavers ranging in age from 77 to 96 years. In three cases unilateral uncemented Austin Moore implants were used, and in one case a unilateral cemented Thompson prosthesis had been implanted. The time of implantation in the two specimens where this information could be obtained was greater than 40 months. Sections were made at 12 diaphyseal locations from the superior aspect of the lesser trochanter through the distal diaphysis. Section properties (areas and second moments of area, or area moments of inertia) were determined by tracing photographs of the cross-sections with a digitizer. In this sample of prosthetic femora, we found reductions in both total subperiosteal area (TA) and endosteal area (ENDA) relative to the contralateral unoperated side in most sections distal to the lesser trochanter. The average pairwise reduction in ENDA for this region was 21.1 mm2, reaching statistical significance in one distal diaphyseal section. The average decline in TA in this region was 10.2 mm2. Because the reduction in endosteal dimensions was generally greater than the reduction in subperiosteal dimensions, cortical area (CA) was maintained or increased throughout the distal 80% of this region in prosthetic femora with an average increase in CA of 9.3 mm2, reaching statistical significance in one mid-diaphyseal section. A completely different pattern of remodeling occurred in the two most proximal sections through the lesser trochanter and base of the femoral neck.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
58.
目的研究房性、室性早搏联律间期缩短与桡动脉图的关系,探讨早搏对血流动力学的影响。方法经心电图诊断为房性早搏48例及室性早搏51例,再应用心功能仪检查,通过信号处理技术对早搏桡动脉图形进行面积积分。结果①早搏桡动脉图积分面积提前率〉40%时最小,20%-40%时居中,〈20%时最大(P〈0.05)。②提前率相同情况下,左房与右房的早搏桡动脉图积分面积比较差异无统计学意义(P〉0.05);左室与右室的早搏桡动脉图积分面积比较差异有统计学意义(P〈0.05)。③早搏时的桡动脉图积分面积最小,早搏前第一个窦性心搏居中,早搏后第一个窦性心搏最大(P〈0.05)。结论早搏对血流动力学的影响主要与早搏的联律间期长短有关,室性早搏还与其发生部位有关,早搏的代偿间歇,不能改善对血流动力学的影响。  相似文献   
59.
Clinical symptoms and findings in cranial computed tomography (CT) were evaluated in 326 patients with intracerebral hemorrhage (ICH). Localizations of ICH were the lobes (n = 254), the basal ganglia (n = 46), the pons and brain stem (n = 13) and the cerebellum (n = 8). Multiple hematomas were present in nine patients. An initial coma (n = 225) was most frequent in ICH of the pons (n = 7), cerebellum (n = 6), and the frontal (n = 71) and temporal (n = 66) lobes. Epileptic seizures (n = 70) were most common in hematomas of the frontal (n = 24), temporal (n = 19) and parietal (n = 12) lobes and the basal ganglia (n = 6). A history of hypertension was given in 140 patients; 119 of these had an ICH with a size of ≥3 cm. Mortality (n = 162) was high with ICH in the pons and brain stem (10 out of 13), in the frontal (54 out of 98) and parietal (32 out of 58) lobes and the basal ganglia (n = 23). A size of the ICH of 3 cm or more in cranial CT and an associated ventricular hemorrhage were associated with a bad outcome. An initial disturbance of consciousness was the only reliable clinical predictor of outcome (chi-square, p < 0.001). Katamnestic evaluation of 66 of the 164 survivors after 5.2 years revealed seizures in 20 patients and mild neurological deficits in 41. Another 14 patients were partially, and nine totally dependent Nineteen patients had died in between; there was only one death attributable to another ICH.  相似文献   
60.
We evaluated the effects of allogeneic bone marrow stromal cell treatment of stroke on functional outcome, glial–axonal architecture, and immune reaction. Female Wistar rats were subjected to 2 h of middle cerebral artery occlusion. Rats were injected intravenously with PBS, male allogeneic ACI – or syngeneic Wistar –bone marrow stromal cells at 24 h after ischemia and sacrificed at 28 days. Significant functional recovery was found in both cell-treated groups compared to stroke rats that did not receive BMSCs, but no difference was detected between allogeneic and syngeneic cell-treated rats. No evidence of T cell priming or humoral antibody production to marrow stromal cells was found in recipient rats after treatment with allogeneic cells. Similar numbers of Y-chromosome+ cells were detected in the female rat brains in both groups. Significantly increased thickness of individual axons and myelin, and areas of the corpus callosum and the numbers of white matter bundles in the striatum were detected in the ischemic boundary zone of cell-treated rats compared to stroked rats. The areas of the contralateral corpus callosum significantly increased after cell treatment compared to normal rats. Processes of astrocytes remodeled from hypertrophic star-like to tadpole-like shape and oriented parallel to the ischemic regions after cell treatment. Axonal projections emanating from individual parenchymal neurons exhibited an overall orientation parallel to elongated radial processes of reactive astrocytes of the cell-treated rats. Allogeneic and syngeneic bone marrow stromal cell treatment after stroke in rats improved neurological recovery and enhanced reactive oligodendrocyte and astrocyte related axonal remodeling with no indication of immunologic sensitization in adult rat brain.  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