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   4996篇
  免费   472篇
  国内免费   133篇
耳鼻咽喉   79篇
儿科学   68篇
妇产科学   97篇
基础医学   624篇
口腔科学   164篇
临床医学   547篇
内科学   548篇
皮肤病学   54篇
神经病学   193篇
特种医学   270篇
外科学   760篇
综合类   620篇
预防医学   358篇
眼科学   150篇
药学   618篇
  2篇
中国医学   231篇
肿瘤学   218篇
  2024年   20篇
  2023年   119篇
  2022年   261篇
  2021年   355篇
  2020年   254篇
  2019年   216篇
  2018年   222篇
  2017年   234篇
  2016年   200篇
  2015年   217篇
  2014年   372篇
  2013年   342篇
  2012年   257篇
  2011年   273篇
  2010年   206篇
  2009年   189篇
  2008年   201篇
  2007年   199篇
  2006年   171篇
  2005年   131篇
  2004年   102篇
  2003年   96篇
  2002年   86篇
  2001年   60篇
  2000年   73篇
  1999年   64篇
  1998年   60篇
  1997年   47篇
  1996年   53篇
  1995年   49篇
  1994年   46篇
  1993年   40篇
  1992年   40篇
  1991年   25篇
  1990年   25篇
  1989年   30篇
  1988年   27篇
  1987年   27篇
  1986年   28篇
  1985年   31篇
  1984年   29篇
  1983年   7篇
  1982年   26篇
  1981年   26篇
  1980年   13篇
  1979年   19篇
  1978年   9篇
  1977年   7篇
  1976年   5篇
  1973年   3篇
排序方式: 共有5601条查询结果,搜索用时 531 毫秒
21.
在实验室绝热反应器中进行了乙苯脱氢制苯乙烯的反应动力学研究。根据不同反应机理,提出五种反应模型,经残差分析及模拟计算规律与实验规律的比较,确定Carra双曲模型为最佳反应动力学模型。通过对实验数据的回归拟合,经参数估计求得了速率方程的频率因子和活化能。  相似文献   
22.
Abstract The purpose of this study was to determine the clinical response to local delivery of tetracycline in relation to clinical and microbiological conditions of the other teeth. 4 deep pockets were monitored in 19 subjects with multiple deep periodontal lesions and high counts of P. gingivalis. In 9 patients (XT) only 2 of the selected lesions were treated by placement of tetracycline fibers (Actisite®). while the rest of the dentition was left untreated. In the other 10 patients, all teeth were supragingivally scaled and then treated by application of polymeric tetracycline HCl containing fibers, the whole dentition was subject to full mouth scaling and root planing, and the patients rinsed with 0.2% chlorhexidine (FT). A significant reduction in mean PPD was observed in all treated sites after two months. This reduction was maintained over the following 4 months. The magnitude of the effect was significantly greater in the FT group (1.74 mm) than in the LT group (0.88 mm). The mean attachment level changes were similar after 2 months in locally and fully treated subjects. A tendency of relapse was noted for treated sites in LT patients from month 2 to 6. A level of statistical significance was not reached for this effect. Data from measurements recorded at 6 sites around all teeth in the full mouth treated patients were analyzed using multiple linear regression. This analysis showed local changes in PPD and AL were significantly and strongly correlated with the baseline value of the respective parameter at the same site. In addition, more pocket depth reduction was noted if a site was not bleeding on probing at 6 months, if the location of a site was not approximal and if the tooth was not a second molar. Sites located on second molars showed also less AL gain than sites located on other teeth. Smokers showed significantly less reduction in PPD and significantly less AL gain. Furthermore, if subjects had a high % of pockets deeper than 4 mm at baseline they showed significantly less attachment gain.  相似文献   
23.
Blood gas analysis can be used to reliably predict outcome in infants with congenital diaphragmatic hernia (CDH) both before and after surgical repair, providing these values are indexed to some measurement of alveolar ventilation. Until recently there has been difficulty in interpreting some of the published data because of differing sampling sites and the fact that ventilatory parameters, which have major influences on all blood gas values in this anomaly, were not included. Application of this information enables us to identify infants with similar degrees of severity of CDH in order to evaluate the efficacy of novel forms of therapy and to determine whether they represent a genuine advance in management where more conventional forms of treatment have failed.  相似文献   
24.
A study was carried out to evaluate the andrological parameters in 540 human semen specimens divided into groups according to sperm counts. The parameters were: motility percentage and grade, percentage of viability and of morphologically normal sperm and immature cells. The Duncan multiple range test and the Kruskal-Wallis test with multiple comparison of ranks were used in the statistical analyses. Of particular interest, among other our findings, were the significant differences obtained by comparing the group with sperm counts up to 5 x 10(6) per ml semen and that with counts ranging from 5.1 to 10 x 10(6) per ml semen. This was true for all parameters with the exception of semen volume. Comparison of the oligozoospermic groups (up to 20 x 10(6)/ml) with those having higher sperm counts also showed significant differences. There was a trend towards improvement of the examined parameters with the increase in sperm density, but with a remarkable heterogeneity particularly within the oligozoospermic groups. In all groups motility, viability and morphological normality of sperm showed a positive correlation with each other. "Normal values" of the parameters studied could be derived from scatterplot charts over the entire range of sperm counts and from the statistical evaluation of the grouped material.  相似文献   
25.
本文用OMEGA 500型Υ相机和MCS 560计算系统,即SPECT,R波门控采集心血池图象,在此基础上进行曲线分析,编制BASIC程序计算11项心功能指标。临床应用结果表明:PFR、LVFF、FFR是舒张期功能的优选指标,其它指标对心功能评价也都有显著意义。  相似文献   
26.
目的:观察病房康复延伸护理对脑卒中迟缓性偏瘫患者三维步态时空参数的影响。方法:将60例脑卒中迟缓性偏瘫患者随机分为常规护理组(A组,n=30)、病房康复延伸护理组(B组,n=30)两组,予以相应的方法治疗8周,评估治疗前后两组患者三维步态时空参数。结果:与治疗前相比,治疗后两组患者的步长、步幅、步速、步频、支撑相、双支撑相等参数及B组摆动相均有不同程度的改善(P<0.05); A组摆动相和步宽及B组步宽的变化差异无统计学意义(P>0.05)。与治疗后A组比较,治疗后B组的步长、步幅、步速、步频、支撑相、双支撑相等参数改善较为明显(P<0.05),步宽和摆动相的改善差异无统计学意义(P>0.05)。结论:病房康复延伸护理能改善脑卒中迟缓性偏瘫患者三维步态时空参数,具有临床意义。  相似文献   
27.
[目的] 介绍方剑乔教授针药结合治疗类风湿性关节炎的临床思辨特色及其临证经验。[方法] 通过整理、回顾、分析方教授治疗类风湿性关节炎的相关文献及医案,从中医病因病机和治则治法等方面,总结归纳方教授治疗类风湿性关节炎的学术经验,并列举医案一则予以佐证。[结果] 临床思辨上,方教授认为“痰、瘀、虚交错”为该病的基本病机,治疗宜针药结合,主要起到同效相须、异效互补和反效制约的作用。临证治疗上,方教授强调,针刺宜整体治疗与局部穴位兼顾,须重视经络辨证。合理应用电针,疼痛急性发作期电针频率多选择“先高后低”,先100 Hz/10~15 min,后2 Hz/30 min;慢性疼痛期电针治疗多选择疏密波(2/100 Hz)。用药强调精准辨证,在该病四种基本证型的基础上提出了阴虚湿热兼证的概念,确立了滋阴清热、通络止痛的治疗大法。倡导适时采用经皮穴位电刺激治疗,其操作简单,携带方便,在镇痛方面具有明显的优势。所举病案采用西药甲氨蝶呤片抑制免疫,稳定病情;中药以祛风除湿为主,佐以藤类药通络行窜、祛风止痛;电针治疗选择频率为2/100 Hz的疏密波调和气血、通络止痛。经治疗后,患者症状缓解,相关指标趋于正常。[结论] 方剑乔教授根据本病的病因病机及临床特点进行辨证论治,针药并重,中西医取长补短,临床特色鲜明,治疗效果显著,值得临床借鉴和推广。  相似文献   
28.
We reviewed retrospectively 126 (5 male, 121 female) patients suffering from Takayasu arteritis who had been treated in our clinics from 1971 to 1990. The patients' ages ranged from 19 to 80yrs old (1990) with a mean age of 48.7 ± 11.8 years. HLA typing analysis in 98 patients revealed that 45 patients (47%) were confirmed as carrying the Bw52 antigen, a high result that is statistically significant as compared with that in healthy Japanese. Arteriograms (performed in 75 patients) revealed that 28 patients (37%) were affected in the aorta and its main branches by this disease (type IV by Nasu's classification) and 23 patients (31%) were affected only in the main branches (type I). The C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) improved significantly from 2.55 ± 0.28(+) and 57.0 ± 5.69 mm/hr to 0.53 ± 0.12(+) and 31.2 ± 3.45 mm/hr, respectively after treatment including steroid and antiplatelet therapy (P < 0.01).=" patients=" with=" bw52=" exhibited=" more=" severe=" inflammatory=" conditions=" than=" those=" without=" bw52.=" lung=" scintillations=" performed=" in=" 81=" patients=" showed=" pulmonary=" arterial=" lesions=" in=" 50=" patients=" (62%).=" echocardiograms=" revealed=" aortic=" regurgitation=" (ar)=" in=" 44=" patients=" (35%),=" with=" a=" significant=" difference=" noted=" between=" the=" bw52=" positive=" group=" and=" the=" bw52=" negative=" group=" [29/40=" (73%)=" versus=" 11/47=" (23%),=">P < 0.001].=" patients=" with=" bw52=" were=" prescribed=" higher=" doses=" of=" steroids=">P < 0.05)=" for=" longer=" periods=">P < 0.01)=" than=" those=" without=" bw52.=" of=" 11=" patients=" who=" died=" during=" our=" study=" period,=" 7=" died=" of=" cardiac=" complications,=" all=" of=" whom=" were=" suffering=" from=" ar.=" hla=" analysis=" performed=" in=" 6=" of=" these=" 7=" patients=" revealed=" that=" all=" carried=" the=" bw52=" antigen.=" in=" conclusion,=" the=" retrospective=" survey=" revealed=" that=" patients=" carrying=" the=" bw52=" antigen=" showed=" more=" severe=" inflammatory=" conditions=" and=" progressed=" more=" rapidly=" to=" complications=" and=" the=" fatal=" morbid=" condition,=" as=" compared=" with=" those=" without=" bw52.=" this=" suggests=" the=" important=" role=" of=" gene=" disequilibrium=" with=" this=" hla=">  相似文献   
29.
New methods for the detection of ECG and EOG artefacts in the EEG are introduced, which can also be used for the evaluation of the quality of the elimination procedure. These algorithms are based on the estimation of the power or coherence spectrum by means of FFT. The advantage of this method is that the EEG spectrum is monitored by the test algorithm. The spectrum will be plotted if no influence of the ECG and EOG can be found. On the other hand, if artefacts are detected the correction of the EEG time series will be carried out and the spectrum of the corrected EEG time series will be plotted after repeated monitoring by the test algorithm.  相似文献   
30.
This surgical anatomy study aimed to evaluate the possibility of identifying the external laryngeal nerve during thyroid surgery and the possible variations of nerves at risk. Fifty patients underwent total thyroidectomies during a period of 12 months. Using a neurostimulator, the distal motor branch of the external laryngeal nerve was searched. Electrical stimulation of a nervous branch aimed to provoke a global contraction of the cricothyroid in order to identify with certitude the external laryngeal nerve. The external laryngeal nerve was identified in 20% of cases. Its course was, with almost equal frequency, either (1) between the vessels of the superior thyroid pedicle or (2) superficial and anterior to the fascia of the cricothyroid muscle. The external laryngeal nerve is hard to find during thyroid surgery, even with a neurostimulator. It can be vulnerable during thyroid surgery but only in cases of anatomic variations. Searching for the nerve systematically during thyroid surgery does not seem to be useful. Several precautions when dissecting the superior pole of the thyroid gland seem to be necessary and sufficient to respect the external laryngeal nerve.  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