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   1623篇
  免费   112篇
  国内免费   5篇
耳鼻咽喉   11篇
儿科学   60篇
妇产科学   20篇
基础医学   168篇
口腔科学   94篇
临床医学   153篇
内科学   293篇
皮肤病学   13篇
神经病学   81篇
特种医学   211篇
外科学   161篇
综合类   82篇
预防医学   137篇
眼科学   18篇
药学   147篇
中国医学   24篇
肿瘤学   67篇
  2023年   11篇
  2022年   20篇
  2021年   26篇
  2020年   22篇
  2019年   23篇
  2018年   34篇
  2017年   24篇
  2016年   27篇
  2015年   23篇
  2014年   40篇
  2013年   72篇
  2012年   78篇
  2011年   68篇
  2010年   57篇
  2009年   50篇
  2008年   87篇
  2007年   103篇
  2006年   52篇
  2005年   47篇
  2004年   45篇
  2003年   43篇
  2002年   42篇
  2001年   40篇
  2000年   31篇
  1999年   33篇
  1998年   65篇
  1997年   52篇
  1996年   52篇
  1995年   28篇
  1994年   36篇
  1993年   30篇
  1992年   19篇
  1991年   18篇
  1990年   13篇
  1989年   30篇
  1988年   39篇
  1987年   31篇
  1986年   23篇
  1985年   36篇
  1984年   18篇
  1983年   18篇
  1982年   14篇
  1981年   9篇
  1980年   11篇
  1979年   12篇
  1978年   14篇
  1977年   9篇
  1976年   13篇
  1975年   10篇
  1972年   10篇
排序方式: 共有1740条查询结果,搜索用时 15 毫秒
101.
Levin  DC; Gardiner  GA  Jr 《Radiology》1987,164(3):675-680
For many years, atherosclerotic coronary artery lesions have been described by angiographers only in terms of location and degree of narrowing. However, it has become apparent that coronary stenoses generally have distinct morphologic features that can be recognized at angiography and that allow them to be classified as either "simple" or "complex" plaques. Complex plaques are those characterized by ulcerated or ruptured surfaces, subintimal hemorrhage, superimposed partially occluding thrombi, recanalized thrombi, or some combination. Pathologic studies have shown a very high frequency of these lesions at sites of total thrombotic occlusion of coronary arteries. Clinical and angiographic studies have demonstrated a high frequency of such lesions in living patients with both unstable angina and acute myocardial infarction. The presence of complex stenoses has also been found to increase the risk of future myocardial infarction. Plaque morphology thus appears to significantly affect the prognosis of patients with coronary disease and should be carefully evaluated in interpretation of all coronary angiograms.  相似文献   
102.
目的建立四川若尔盖地区产麻花艽Gentiana straminea Maxim.药材HPLC指纹图谱。方法以龙胆苦苷为内参照物,分析10批麻花艽药材的HPLC色谱行为,同时以当地产近缘种黄管秦艽Gentiana officinalisH.Smith及国家药典品种粗茎秦艽Gentiana crassicaulis Duthie ex Burk.为外类群进行比对。色谱条件:UltimateXB-C18(250 mm×4.6 mm,5μm);流动相:乙腈-0.02%乙酸水梯度洗脱;体积流量:1 mL/min;检测波长:240 nm;柱温:30℃;进样量:10μL。结果标定16个共有峰,确定其中2个峰的归属,建立了可与上述2个外类群相区别的麻花艽指纹图谱。结论该图谱基本反映了四川若尔盖地区产麻花艽化学背景特征,可为道地药材评价及相关中藏药品种鉴定提供基础资料。  相似文献   
103.
目的:系统评价我国小切口复位内固定术(MIPPO)与切开复位内固定治疗胫骨远端骨折的疗效与安全性。方法计算机检索中国知网(CNKI:2003年9月-2013年5月)、万方数据库(2003年9月-2013年5月)、维普数据库(2003年9月-2013年5月),中国生物医学数据库及超星电子图书。手工检索国内近五年来发表于《中华骨科杂志》、《中国矫形外科杂志》及《临床骨科杂志》等各骨科杂志及相关杂志的相关文献。收集所有相关 MIPPO与切开复位内固定治疗胫骨远端骨折的随机对照试验及半随机对照试验,采用 Cochrane协作网提供的软件 RevMan5.0进行系统评价。结果共纳入12篇随机对照试验及半随机对照试验,共733例患者,纳入研究质量评价结果为 B级10篇,C级2篇。系统评价结果显示,与切开复位内固定组相比,MIPPO 组术中失血量少[SMD=-4.46,95%CI(-5.87,-3.05),P <0.05];骨折愈合时间短[SMD=-1.54,95%CI(-2.02,-1.06),P<0.05];术后优良率高[RR=1.22,95%CI(1.13,1.32),P <0.05],但两组手术时间比较差异无统计学意义。结论采用 MIPPO术治疗胫骨远端骨折具有明显的优势,值得临床推广。但由于该系统评价尚存在一定的局限性,故需要大量严格的、大样本量的、多中心性的,并且采用正确的随机、盲法、分配隐藏以及对失访与退出的患者进行正确的意向性分析(ITT分析)等文献研究来进一步论证。  相似文献   
104.
A partial blockade of the multiple actions of cocaine is one strategy by which cocaine dependence may be treated. Risperidone, a 5-hydroxytryptamine and dopamine D2 antagonist, is an atypical antipsychotic and was a candidate medication for the treatment of cocaine dependence. One hundred ninety-three cocaine-dependent subjects were enrolled in a 12-week, randomized, double-blind, placebo-controlled trial. Subjects initially received either placebo or 4 or 8 mg of risperidone, with a subsequent change to active doses of 2 mg and 4 mg. Subjects attended the clinic twice each week, provided urine samples, obtained medication, and underwent one behavioral therapy session per week. The study was terminated at the interim analysis. Retention was worse for the 4- and 8-mg active medication groups. Side effects were primarily associated with the 8-mg dose, although neither 2 mg nor 4 mg was well accepted by subjects. There was no reduction in cocaine use associated with risperidone. The results suggest that although antagonists might be a useful treatment approach, such as in the treatment of opiate dependence, risperidone is unlikely to find broad acceptance with the treatment-seeking population.  相似文献   
105.
Tumor cell resistance due to enhanced efflux of drugs with diverse structures and/or mechanisms of action is termed multidrug resistance (MDR), and modulation of the MDR phenotype by calcium blockers or calmodulin inhibitors is suggested to involve P-glycoprotein. In drug-sensitive (S) and 5-fold doxorubicin (DOX)-resistant (R0) L1210 mouse leukemia cells, no obvious differences in mdr mRNA or P-glycoprotein expression or alterations in cellular uptake, retention, or cytotoxicity of vincristine (VCR) were observed. However, in the 10-fold (R1) and 40-fold (R2) DOX-resistant sublines, expression of P-glycoprotein was correlated with the level of resistance (R2 greater than R1). An RNase protection assay revealed that elevated levels of mdr1 and mdr2 mRNA were detected in R1 and R2 cells, with an additional increase in mdr3 mRNA in the R2 subline. Further, in the R1 and R2 sublines, no VCR dose-dependent cytotoxicity was apparent, and cell kill of greater than 40% was not achievable following a 3-hr drug exposure. Cellular uptake and retention of VCR were 2- to 4-fold lower in the R1 and R2 sublines, compared with similarly treated S or R0 cells. Potentiation of VCR cytotoxicity by a noncytotoxic concentration of 5 microM trifluoperazine (TFP) was greater than 2-fold in S and R0 cells and less than 1.3-fold in the R1 and R2 sublines. Modulation of VCR uptake by 5 microM TFP in the S and R0 cells was 2-fold and it was 4- to 7-fold in the R1 and R2 sublines. The presence of 5 microM TFP, by competing for efflux, enhanced VCR retention 1.5-fold in S and R0 cells and 2- to 4-fold in the R1 and R2 sublines. In contrast to these results with VCR, dose-dependent cytotoxicity of DOX was apparent in all the resistant sublines, and modulation of DOX cytotoxicity by 5 microM TFP was dependent on the level of resistance. Cellular accumulation of DOX was 20 and 50% lower in the R1 and R2 sublines, respectively, compared with similarly treated S or R0 cells. Marked increases (greater than 1.5-fold) in cellular accumulation of DOX by TFP were apparent only in the R2 subline. Results suggest that a relationship between overexpression of P-glycoprotein isoforms and their role in affecting cellular drug levels and consequent cytotoxicity in MDR L1210 cells determines resistance to VCR but not DOX.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
106.
BackgroundRenal cell carcinoma (RCC) is the most common form of kidney cancer. Surgery is a standard procedure to resect the tumor during total (TN) or partial (nephron-sparing) nephrectomy (PN). Ciprofloxacin is most often administered at the usual intravenous dose of 100–400 mg/12 h. The application of such low doses of ciprofloxacin as 200 mg/24 h carries the risk of achieving subtherapeutic concentrations even in patients with limited renal function. The aim of the study was a comparison of concentrations and pharmacokinetics for ciprofloxacin at steady-state in patients after total and partial nephrectomy and evaluation of the effectiveness of the iv dose 200 mg/24 h against the theoretical value of MIC, 0.5 μg/ml.MethodsThe research was carried out on two groups of patients after nephrectomy: total (group 1, n = 21; mean [SD], age, 62.9 [14.4] years; weight, 76.0 [14.6] kg; creatinine clearance, clcr, 90.7 [22.2] ml/min) and partial (group 2, n = 15; 61.7 [9.3] years; 87.8 [16.4] kg; CLCR, 107.8 [36.4] ml/min). The patients were treated with ciprofloxacin in the dose of 200 mg/24 h (iv). Plasma concentrations of ciprofloxacin at steady state were measured with validated HPLC method with UV detection.ResultsThe mean values of plasma concentrations of ciprofloxacin at steady state in group 1 and 2 were: Cssmax, 2.012 and 1.345; Cssmin, 0.437 and 0.244 μg/ml, respectively. The main pharmacokinetic parameters for ciprofloxacin in group 1 and 2 were as follows: AUC(0–last), 30.9 [17.9] and 19.5 [8.7] μg h/ml; AUMC(0–last), 177.91 [11.1] and 91.9 [66.5] μg h2/ ml; t1/2β, 13.9 [7.7] and 9.8 [3.3] h; MRT, 16.5 [12.1] and 9.77 [5.4] h; Vd, 115.0 [67.2] and 142.2 [78.7] l; CL, 6.2 [3.3] and 10.8 [5.7] l/h, respectively. With the assumed MIC = 0.5 μg/ml, the values of Cssmax/MIC < 10 and AUC/MIC < 125 were obtained in all the patients.ConclusionIn our patients we observed significant differences in some pharmacokinetic parameters of ciprofloxacin after two types of nephrectomy.  相似文献   
107.
目的 探讨应用非每日千伏级锥形束CT(KVCBCT)校位能否改善摆位误差对鼻咽癌调强放疗(IMRT)剂量分布影响。方法 对14例行根治性IMRT的鼻咽癌患者治疗开始后连续5次用KVCBCT检测摆位误差,并将其均值作为系统误差预测值,若其>1.5 mm则在第6次离线校位。假设通过移床能完全校正系统误差,那么从第6次起实际各方向摆位误差值加上离线校位值可得到未行校位时的摆位误差值,在治疗计划系统中通过等中心移位重新计算剂量来模拟应用非每日校位策略前后摆位误差所致的剂量变化。结果 对10例系统误差预测值>1.5 mm者摆位误差明显降低了靶区剂量:98%大体肿瘤体积(GTV)所接受剂量(GTV-D98)平均减少3.8Gy(Z=-2.81,P=0.005),原发灶临床靶体积(CTVns) D95( CTVns-D95)平均减少4.8Gy(Z=-1.96,P=0.050),高危CTV1 -D95平均减少1.0Gy(Z=-2.82,P=0.005),低危CTV2-D95减少不明显(Z=-0.13,P=0.900)。应用非每日校位后明显减少了摆位误差的三维方向位移总量,均值从3.6 mm减少为2.6mm(t=2.00,P=0.000),GTV-D98平均增加3.8 Gy(Z=-2.70,P=0.007),CTVns-D95平均增加5.0Gy(Z=-2.15,P=0.030),CTV1 -D95平均增加0.9Gy(Z=-2.80,P=0.005),减少了危及器官剂量增加>3%、5%患者比例。结论 应用非每日KVCBCT校位能有效减少摆位误差对鼻咽癌IMRT剂量分布的不利影响。  相似文献   
108.
目的:观察复方土牛膝糖浆剂在体外和动物模型上的抗病毒作用。方法:用细胞培养法,通过观察细胞病变评价复方土牛膝糖浆剂对常见的致上呼吸道感染的柯萨奇B族病毒4型(CoxB4)、副流感病毒(HVJ)、呼吸道合胞病毒(RSV)、单纯疱疹病毒(HSV-Ⅰ)所致的细胞病变(CPE)的抑制作用;通过用流感病毒滴鼻感染小鼠来研究复方土牛膝糖浆剂对病毒感染小鼠所引起的死亡保护作用。结果:复方土牛膝糖浆在体外对CoxB4、RSV病毒的致细胞病变作用有明显抑制作用,其IC50分别为2.0、2.8μL糖浆/mL,TI分别为5.6和4,对HSV-1、副流感-1型病毒的致细胞病变有一定的抑制作用。其IC50分别为4.0、5.0μL糖浆/mL,TI分别为2.8和2.24。在小鼠感染病毒15天内,复方土牛膝糖浆5mL/(kg.d)剂量组动物的死亡率为55%;死亡保护率分别为38.39%,与感染对照组相比有显著差异(P<0.05),复方土牛膝糖浆10mL/(kg.d)、5mL/(kg.d)两个剂量组小鼠的存活天数较感染组明显延长,与对照组比较有显著性差异。生命延长率分别为17.67%和22.22%。结论:复方土牛膝糖浆剂无论在体内或是体外均有较明显的抗病毒作用。  相似文献   
109.
息风化痰通腑汤合醒脑静注射液治疗急性脑出血疗效观察   总被引:1,自引:0,他引:1  
目的观察息风化痰通腑汤合醒脑静治疗急性脑出血的临床疗效。方法将53例中小量脑出血(≤30 ml)患者随机分成2组。治疗组29例在常规西医综合治疗基础上,加用息风化痰通腑汤合醒脑静注射液治疗;对照组24例仅采用常规西医综合治疗。2组均14日为1个疗程,判定疗效。结果:治疗组有效率93.1%,对照组83.3%,2组比较有显著性差异(P<0.05),治疗组疗效显著优于对照组。2组治疗前后昏迷情况比较、血肿吸收情况及神经功能缺损积分对比,均有显著性差异(P<0.01),且治疗组疗效明显优于对照组(P<0.01)。结论息风化痰通腑汤合醒脑静注射液治疗中小量急性脑出血,能提高治愈率,降低病死率,缩短治疗时间,提高生存质量,无明显毒副作用。  相似文献   
110.
污水中汞的微波消解冷原子吸收测定法   总被引:3,自引:0,他引:3  
目的 改进冷原子吸收法测定污水中汞的消解方法。方法 采用王水(1+1)微波消解法代替KMnO4-K2S2O8消解法测定污水中的汞。结果 王水(1+1)微波消解水样测定污水中汞,方法的线性范围为0~10.0μg/L,检出限为0.25μg/L,相对标准偏差小于2.7%,加标回收率为95.0%-102.0%。结论 与KMnO4-K2S2O8消解法相比,该方法具有较高的灵敏度和精密度,操作简单,结果可靠,适用于环境监测分析。  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