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   2020篇
  免费   211篇
  国内免费   57篇
耳鼻咽喉   17篇
儿科学   49篇
妇产科学   20篇
基础医学   234篇
口腔科学   42篇
临床医学   219篇
内科学   253篇
皮肤病学   50篇
神经病学   88篇
特种医学   98篇
外科学   320篇
综合类   343篇
预防医学   134篇
眼科学   20篇
药学   200篇
  2篇
中国医学   81篇
肿瘤学   118篇
  2024年   8篇
  2023年   12篇
  2022年   45篇
  2021年   71篇
  2020年   58篇
  2019年   46篇
  2018年   45篇
  2017年   54篇
  2016年   54篇
  2015年   104篇
  2014年   95篇
  2013年   118篇
  2012年   169篇
  2011年   168篇
  2010年   138篇
  2009年   126篇
  2008年   114篇
  2007年   110篇
  2006年   117篇
  2005年   96篇
  2004年   67篇
  2003年   59篇
  2002年   66篇
  2001年   35篇
  2000年   31篇
  1999年   26篇
  1998年   24篇
  1997年   20篇
  1996年   24篇
  1995年   17篇
  1994年   9篇
  1993年   16篇
  1992年   8篇
  1991年   6篇
  1990年   11篇
  1989年   18篇
  1988年   10篇
  1987年   6篇
  1986年   16篇
  1984年   5篇
  1983年   6篇
  1982年   7篇
  1981年   3篇
  1980年   8篇
  1978年   6篇
  1977年   5篇
  1976年   6篇
  1975年   4篇
  1974年   3篇
  1971年   3篇
排序方式: 共有2288条查询结果,搜索用时 15 毫秒
101.
室壁应力与应变的关系评价高血压病左室收缩功能   总被引:21,自引:7,他引:21  
目的 探索用室壁应力 (stress)与应变 (strain)的关系评价高血压病左室收缩功能的临床价值。方法 研究对象为 5 5例高血压病患者和 3 0例健康人。应用超声心动图计算左室射血分数 (EF)、心指数 (CI)、重量指数 (LVMI)和相对室壁厚度 (RWT) ,并联合袖带肱动脉血压值计算左心室收缩期室壁经线峰值应力 (Pσm)。根据LVMI和RWT将高血压病分为左室正常构型和左室重构两组。在数字化超声工作站中应用定量组织速度成像 (QTVI)获取左室前壁心肌 2个节段长轴应变曲线和峰值收缩应变值 (PSS)。结果 ①以EF ,CI表示的心脏收缩功能 ,在高血压病左室正常构型组值中无明显变化 ;而在高血压病左室重构组中下降 ,差异具有极显著意义 (P <0 .0 1)。②Pσm在高血压病两组中较对照组均有增高 (P <0 .0 5~ 0 .0 1) ,两组间比较差异具有极显著意义 (P <0 .0 1)。③高血压病两组左室前壁基底段 (Bas)和中段 (Mid)的 pSS值均显著下降 (P <0 .0 1) ,两组间比较差异具有极显著意义 (P <0 .0 1)。④直线相关分析结果显示高血压病两组Pσm与PSSBas和PSSMid均呈显著负相关。根据正常构型组Pσm与PSSBas直线回归方程计算 ,在相同Pσm水平 ,左室重构组PSSBas的实测值显著低于预测值及实测值与预测值的比值较正常构型组显著下降 ,差  相似文献   
102.
目的:系统评价自体骨移植与骨形成蛋白治疗成人长骨骨折不愈合相关指标,为成人长骨骨折不愈合治疗提供参考依据。方法:计算机检索PuMed、Embase、Cochrane图书馆、中国知网(CNKI)、万方数据期刊全文数据库及中国生物医学文献数据库(CBM)发表的对于自体骨移植与骨形成蛋白治疗成人长骨骨折不愈合的随机对照试验,检索时间从建库至2019年3月。由2名研究者按照纳入和排除标准独立进行筛选文献,提取资料,并采用Jadad评价量表对纳入的文献进行质量评价。采用RevMan 5.3统计学软件对两种方法的感染发生率、成功愈合率、二次手术率、住院时间及术中失血量进行Meta分析。结果:共纳入7个随机对照试验研究,共652例患者,自体骨移植组有410例,骨形成蛋白组有242例。Meta分析结果显示:自体骨移植组与骨形成蛋白组在感染发生率[RR=1.32,95%CI(0.90,1.93),P=0.16],成功愈合率[RR=0.95,95%CI(0.84,1.08),P=0.43],二次手术率[RR=1.16,95%CI(0.43,3.12),P=0.76]及住院时间[MD=0.69,95%CI(-0.38,1.75),P=0.21]方面比较差异无统计学意义。自体骨移植组术中失血量明显高于骨形成蛋白组[MD=223.00,95%CI(32.72,413.28),P=0.02]。结论:对于成人长骨骨折不愈合的治疗,骨形成蛋白可以获得和自体骨移植一样的骨折愈合率,同时可以明显减少术中失血量。骨形成蛋白可能更适合成人长骨骨折不愈合的治疗。  相似文献   
103.
Context: Marine cyanobacteria offer considerable potential to isolate new antimalarials to meet a pressing need of our times.

Objective: To explore the antiplasmodial properties of marine cyanobacteria.

Materials and methods: Cyanobacterial samples collected from the coastal regions of Tamil Nadu were identified using light microscopy, and the strains were cultivated in ASN-III medium. Organic extracts (0–100?µg?mL?1) of 25 in vitro mass-cultivated cyanobacteria, prepared using methanol: chloroform mixture (1:1?v/v) were evaluated for their antiplasmodial activity against chloroquine-sensitive and -resistant strains of Plasmodium falciparum by fluorescence-based SYBR Green I assay where chloroquine was used as a control. To detect the toxic effects of cyanobacterial extracts against red blood cells, the invasion, maturation, and growth rate of malarial parasites in cyanobacterial extracts pre-treated versus untreated erythrocytes were quantified microscopically. Mammalian cell line (HeLa) was used to determine cyanobacterial extract toxicity using the MTT assay.

Results: The extracts of Lyngbya aestuarii Liebm. ex Gomont CNP 1005 (C12) Oscillatoria boryana BDU 91451 (C22) and Oscillatoria boryana Bory ex Gomont BDU 141071 (C18) showed promising antiplasmodial activity (IC50?=?18, 18, and 51?μg?mL?1 respectively) against Pf3D7. Pretreatment of red blood cells with IC100 of C12, C18, and C22 (40, 100, and 40?µgmL?1, respectively) did not significantly influence the invasion, maturation, and growth rate of malarial parasites in comparison with untreated RBC controls suggesting a lack of toxicity to host cells. MTT assay based IC50 (>200?μg?mL?1) of these extracts against HeLa cell line also indicates their high selectivity against the malaria parasite.

Discussion and conclusion: These exploratory studies suggest the possibilities of development of new antimalarial compounds from marine cyanobacteria.  相似文献   
104.
We describe a case of 64-year-old female patient with ventricular tachycardia intractable to medical treatment and acute heart failure following myocardial infarction. Emergency surgical ventricular reconstruction and subendocardial resection was undertaken. We discuss the option of surgical intervention in this difficult and unusual clinical scenario.  相似文献   
105.
高效液相色谱法测定多维元素片中泛酸的含量   总被引:2,自引:0,他引:2  
目的建立复合多维元素片中泛酸的含量测定方法。方法高效液相色谱法,C18色谱柱(250mm×4.6mm,5μm);流动相:乙腈-1mL·L-1磷酸水溶液(5∶95);流速:1.0mL·min-1;柱温:25℃;检测波长:200nm。结果泛酸质量浓度在1.32132.32μg·mL-1范围内具有良好的线性关系,相关系数r=0.999 9,平均回收率为99.3%,RSD为1.4%(n=12)。结论该方法快速简便,结果准确,适用于多维元素片中泛酸含量测定。  相似文献   
106.
生物化学是医学院校学生一门重要的公共基础课。大多数学生认为生物化学这门课程内容庞杂、名词术语繁多、抽象难懂、学习难度大,尤其对于生物学科与化学学科基础薄弱的文科生来讲,学习过程吃力,学习效果不理想,期末挂科率较高。本研究从文科生学习生物化学遇到的困难及教师面临的教学现状出发,找出问题,探讨具体应对策略,旨在提高学生学习生物化学课的兴趣和效果。  相似文献   
107.
An intimate physical mixture of graphene oxide (GO) and semiconducting organic molecules like bromophenathrene (BrPh) and bromopyrene (BrPy) was prepared by using a ball milling technique. The structural, microstructural, physical and chemical properties of the mixtures (20 wt% of GO) were analyzed by X-ray diffraction, SEM, FT-IR, TGA and TCSPC studies. Furthermore, the electrochemical properties like AC electrical conductivity, transient photocurrent response (PCTR) and open circuit voltage (OCVD) of the samples were analyzed. It has been observed from TCSPC and OCVD measurements that 20 wt% of GO in the semiconductor composite leads to an enhanced life-time of photo-generated charge carriers. The physical mixture composites exhibit a higher photocurrent than pure BrPh and BrPy.

New organic materials with longer life-times of the charge carrier and enhancement of photocurrent generation were developed.  相似文献   
108.
Figari  IS; Mori  NA; Palladino  MA Jr 《Blood》1987,70(4):979-984
We compared the ability of recombinant human tumor necrosis factor- alpha (rHuTNF-alpha) and tumor necrosis factor-beta (rHuTNF-beta) to stimulate polymorphonuclear neutrophil (PMN) migration and superoxide production. Significant PMN migration occurred across polycarbonate filters after stimulation with rHuTNF-alpha at concentrations ranging from 10(-7) to 10(-10) mol/L and at 10(-7) to 10(-8) mol/L for rHuTNF- beta and N-formylmethionyl-leucyl phenylalanine (FMLP), whereas recombinant human interferon-gamma was only minimally active at 10(-7) mol/L and recombinant human interleukin-1 alpha was inactive at the doses tested. In addition, antibodies to rHuTNF-alpha completely inhibited rHuTNF-alpha but not rHuTNF-beta or FMLP-induced PMN migration. Combinations of rHuTNF-alpha and rHuTNF-beta (at similar molar concentrations) stimulated PMN migration levels comparable to that obtained with rHuTNF-alpha alone. Checkerboard analyses performed by placing different concentrations of rHuTNF-alpha and rHuTNF-beta above and below polycarbonate filters of microchemotaxis chambers demonstrated that rHuTNF-alpha and rHuTNF-beta stimulated both chemotactic and chemokinetic responses by PMN. Additional studies demonstrated that 1 X 10(-8) mol/L rHuTNF-alpha and 3 X 10(-9) mol/L rHuTNF-beta (which represents 10(4) U/mL of each cytokine) were similar in their ability to induce superoxide production by PMNs; however, at ten- to 100-fold lower molar concentrations (10(3) and 10(2) units), rHuTNF-alpha was significantly more active than rHuTNF-beta. At the doses tested, both cytokines were less active than phorbol myristate acetate at stimulating O2- release. The results demonstrate that rHuTNF- alpha and rHuTNF-beta differ quantitatively but not qualitatively in their effects on PMN functions in vitro and suggest that rHuTNF-beta may be less toxic than rHuTNF-alpha in vivo.  相似文献   
109.
那君 《现代保健》2014,(5):23-25
目的:探讨美托洛尔缓释片治疗原发性高血压(EH)并舒张压性心力衰竭(DHF)患者的临床疗效。方法:选取2010年7月-2013年4月本院就诊的126例EH合并DHF患者作为研究对象,所有患者给予美托洛尔缓释片治疗12个月。分别观察治疗前后患者的血压、心率、VEGF和hs-CRP水平的变化,同时观察心脏结构、左室功能参数变化及心功能分级的变化情况。结果:治疗后,左室舒张末径(LVEDD)和左室收缩末径(LVESD)显著减小,二尖瓣返流现象显著减轻,左室射血分数(LVEF)、左室高峰充盈数(LVPFR)显著增加,收缩压、舒张压、脉压和心率以及VEGF和hs-CRP、N末端钠肽原(NT-proBNP)均显著降低,上述指标治疗前后比较差异均具有统计学意义(P&lt;0.05)。结论:美托洛尔缓释片治疗EH并DHF患者,能显著改善患者的心脏功能,治疗效果显著,值得在临床上进一步推广。  相似文献   
110.
Multiple primary malignant neoplasm is the occurrence of a second primary malignancy in the same patient within 6 months of the detection of first primary (synchronous), or 6 months or more after primary detection (metachronous). Multiple primary malignant neoplasms are not very frequently encountered in clinical practice. The relative risk for a second primary malignancy increases by 1.111-fold every month from the detection of the first primary malignancy in any individual. We present 2 patients treated for carcinoma of the breast who developed a metachronous primary malignancy in the stomach to highlight the rare occurrence of multiple primary malignant neoplasms. These tumors were histologically dissimilar, with distinct immunohistochemical parameters. The importance lies in carefully identifying the second primary malignancies, not dismissing them as metastases, and treating them accordingly.Key words: Breast neoplasms, Stomach neoplasms, Neoplasms, Second primaryBreast cancer is the most common malignancy among women worldwide. With proper screening, earlier detection, and improved treatment, survival has greatly increased, with the result that there is now a large population of women with a present or past history of breast cancer. This has led to an increased detection of second primary malignancies among these women. The relative risk for a second primary malignancy increases by 1.111-fold every month from the detection of the first primary malignancy in any individual.1 Several authors have reported on a lesion in the stomach being labeled as a second primary malignancy and subsequently found to be metastasis. When the primary breast tumor is positive for estrogen and progesterone receptors (ER/PRs) and the stomach tumor is ER/PR negative, the diagnosis is established easily.2 However, studies have shown that some primary gastric cancers can have ER/PR positivity. Further, if the primary breast lesion is ER/PR negative, the same cannot be used as a marker. Here, we present 2 breast cancer patients who developed second primary malignancies in the stomach and the final diagnosis was established based on histopathology and immunohistochemistry.  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