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   363043篇
  免费   32516篇
  国内免费   22545篇
耳鼻咽喉   3115篇
儿科学   4753篇
妇产科学   6143篇
基础医学   39126篇
口腔科学   6605篇
临床医学   47898篇
内科学   53565篇
皮肤病学   4294篇
神经病学   17555篇
特种医学   12680篇
外国民族医学   133篇
外科学   35797篇
综合类   61458篇
现状与发展   75篇
一般理论   51篇
预防医学   27127篇
眼科学   9929篇
药学   38309篇
  379篇
中国医学   21007篇
肿瘤学   28105篇
  2024年   1199篇
  2023年   5229篇
  2022年   13131篇
  2021年   17045篇
  2020年   13032篇
  2019年   10889篇
  2018年   11525篇
  2017年   10954篇
  2016年   9974篇
  2015年   15671篇
  2014年   19579篇
  2013年   19103篇
  2012年   28282篇
  2011年   30622篇
  2010年   20731篇
  2009年   16940篇
  2008年   20965篇
  2007年   20713篇
  2006年   19383篇
  2005年   18574篇
  2004年   12720篇
  2003年   11465篇
  2002年   9740篇
  2001年   8451篇
  2000年   8141篇
  1999年   7915篇
  1998年   4508篇
  1997年   4557篇
  1996年   3447篇
  1995年   3133篇
  1994年   2753篇
  1993年   1791篇
  1992年   2574篇
  1991年   2263篇
  1990年   1899篇
  1989年   1637篇
  1988年   1441篇
  1987年   1329篇
  1986年   1041篇
  1985年   825篇
  1984年   534篇
  1983年   416篇
  1982年   236篇
  1981年   210篇
  1980年   196篇
  1979年   253篇
  1978年   143篇
  1977年   113篇
  1974年   119篇
  1973年   100篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
目的 揭示大脑中动脉闭塞(MCAO)后丘脑钙调磷酸酶(CaN)的时空变化规律,探讨CaN的作用机制。方法 制备大鼠大脑中动脉永久性闭塞模型,分别测定缺血后不同时间点病灶侧丘脑CaN的活性和含量。结果 缺血后24h始丘脑CaN的含量下降且不恢复;CaN的活性在缺血后2h和4h减弱,6h始恢复至正常水平。可见,CaN的活性与含量分离。结论 大脑中动脉闭塞后丘脑CaN活性独特的时间变化规律显示其参与介导继发性丘脑损伤,可能具有毒性作用。  相似文献   
92.
OBJECTIVES: To compare the sensitivity of rotational chair (ROTO) versus electronystagmography (ENG) in peripheral vestibular pathology. METHODS: Retrospective chart review. RESULTS: One thousand consecutive patients undergoing evaluation for dizziness and imbalance at a tertiary care referral balance center were reviewed. ROTO was the primary vestibular study used in all patients with ENG used as a confirmatory test at the discretion of the treating physician. A subgroup of 478 patients underwent both ROTO and ENG. Among the patients diagnosed with peripheral vestibulopathy, sensitivity for peripheral vestibulopathy was 71% for ROTO and 31% for ENG. However, specificity was 54% for ROTO and 86% for ENG. CONCLUSIONS: We conclude that in this retrospective cohort with the authors' clinical diagnoses, ROTO is a more sensitive diagnostic study of peripheral vestibular pathology. The higher sensitivity of ROTO and the higher specificity of ENG may support the use of ROTO as the primary vestibular study and ENG as a supplemental vestibular study. Prospective analysis with distinct diagnostic criteria and defined inclusion criteria are necessary before these results can be widely extrapolated.  相似文献   
93.
The aim of this study was to compare the demographic and clinical characteristics of individuals with affective disorders who had attempted suicide at some time in their lives and those who had not made a suicide attempt. In a Chinese rural community, individuals with suicide attempt (N = 30) and those without suicide attempt (N = 166) were assessed with Present State Examination (PSE). Attempters had a significantly higher level of family economic status, higher rate of lifetime depressed mood and hopelessness, and delusions than nonattempters. The logistic regression models also indicated that depressed mood and hopelessness were the most important predictors of suicide attempts. No significant difference in treatment condition was found between attempters and non-attempters. Early identification and interventions focusing on reducing depressed mood, hopelessness, and controlling psychotic symptoms may be helpful in reducing the risk of suicide attempts among individuals with affective disorders residing in the community.  相似文献   
94.
Objectives: To determine interobserver agreement between radiologists for computed tomography (CT) angiography and venography. CT venography of the lower extremities combined with standard CT angiography of the chest may result in an increased overall diagnosis rate of venous thromboembolism (pulmonary embolism or deep venous thrombosis).
Methods: The study had a retrospective cohort design. The population consisted of emergency department patients who were evaluated for suspected pulmonary embolism. A random sample of 50 patients diagnosed and treated for venous thromboembolism and 50 age- and gender-matched patients whose CT angiograms and venograms were read as negative were enrolled. The original reading (R1) was compared with readings of two study radiologists: R2, a general radiologist, and R3, a radiologist with fellowship training in cross-sectional imaging. All readers were blinded to each other.
Results: Both R2 and R3 found both CT angiogram and venogram components technically adequate in 95% (95% CI = 89% to 98%) and 86% (95% CI = 78% to 92%) of studies, respectively. The agreement was very good for CT angiography (lowest agreement = 92%; lowest κ = 0.83) and was good for CT venography (85%, κ = 0.65). In nine cases, R1 read the CT angiogram as negative but the venogram as positive for DVT, whereas both R2 and R3 read both components as negative in four of these nine, suggesting a false-positive isolated DVT rate of 44% (95% CI = 19% to 73%). In no case did R1 read both scan components as negative when R2 and R3 agreed on presence of pulmonary embolism or DVT.
Conclusions: Diagnosis of pulmonary embolism on CT angiography is more reliable than diagnosis of isolated DVT on CT venography.  相似文献   
95.
In this work the feasibility of separating fat and water signals using the balanced steady-state free precession (SSFP) technique is demonstrated. The technique is based on the observation (Scheffler and Hennig, Magnetic Resonance in Medicine 2003;49:395-397) that at the nominal values of TE = TR/2 in SSFP imaging, phase coherence can be achieved at essentially only two orientations (0 degrees and 180 degrees ) relative to the RF pulses in the rotating frame, under the assumption of TR < T2, and independently of the SSFP angle. This property allows in-phase and out-of-phase SSFP images to be obtained by proper choices of the center frequency offset, and thus allows the Dixon subtraction method to be utilized for effective fat-water separation. The TR and frequency offset for optimal fat-water separation are derived from theories. Experimental results from healthy subjects, using a 3.0 Tesla system, show that nearly complete fat suppression can be accomplished.  相似文献   
96.
目的 研究利福昔明对比环丙沙星治疗急性肠炎的有效性和安全性。 方法 采用随机对照方法 ,共治疗 5 1例急性肠炎。利福昔明治疗 2 5例 ,环丙沙星 2 6例 ,用药时间方法相同。观察治疗前后临床症状、大便性状、大便次数、便常规、血常规、尿常规及肝肾功能 ,以了解其疗效及不良反应情况。 结果 利福昔明组 (治疗组 )与环丙沙星组 (对照组 )相比 ,显效率分别为 92 .0 %和 80 .8% ,总有效率分别为 92 .0 %和 96 .2 % ,止泻时间治疗组 2 8.6 7± 15 .92h ,对照组 36 .12± 2 0 .70h ,均未见明显毒副作用。以上各项指标及两组在治疗过程中大便次数变化、大便常规复常率经统计学处理均无显著性差异 (P >0 0 5 )。 结论 利福昔明可用于治疗急性肠炎 ,与环丙沙星比较 ,疗效相仿 ,但耐受性好 ,口服不吸收 ,故值得推广  相似文献   
97.
①目的 观察盐酸丁咯地尔对椎 基底动脉供血不足的治疗作用。②方法 将 82例椎 基底动脉供血不足病人随机分为两组 ,治疗组 4 2例 ,给予盐酸丁咯地尔 2 5 0mL静滴 ,每日 1次 ;对照组 4 0例 ,给予维脑路通0 .5g、胞二磷胆碱 0 .5 g静滴 ,每日 1次 ,均治疗 7d。检测两组治疗前后血液流变学和血流动力学指标的变化。 ③结果 治疗后治疗组全血高切黏度明显低于对照组 ,椎动脉平均血流速度 (VA)明显快于对照组 ,差异均有显著性(t=3.96 0 ,P <0 .0 1 ;t=2 .0 92 ,P <0 .0 5 )。治疗组治疗后全血高切、低切和血浆黏度明显低于治疗前 ,差异有显著性 (t=2 .74 6~ 2 .95 1 ,P <0 .0 1 ) ;VA、基底动脉平均血流速度 (BA)和外周血管阻力指数 (PI)高于治疗前 ,差异有显著性 (t=2 .732~ 5 .1 0 4 ,P <0 .0 1 )。对照组治疗后血浆黏度、PI明显低于治疗前 ,VA高于治疗前 ,差异均有显著性 (t=2 .1 6 8~ 2 .732 ,P <0 .0 5 ) ;全血高切、低切黏度、BA治疗前后差异无显著性 (t=0 .346~ 2 .0 0 8,P >0 .0 5 )。④结论 盐酸丁咯地尔对椎 基底动脉供血不足有良好的改善作用 ,其疗效明显优于维脑路通加胞二磷胆碱的治疗效果  相似文献   
98.
99.
100.
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