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   7142篇
  免费   505篇
  国内免费   21篇
耳鼻咽喉   72篇
儿科学   165篇
妇产科学   146篇
基础医学   696篇
口腔科学   145篇
临床医学   637篇
内科学   1609篇
皮肤病学   71篇
神经病学   567篇
特种医学   151篇
外科学   1378篇
综合类   84篇
一般理论   4篇
预防医学   602篇
眼科学   119篇
药学   509篇
中国医学   5篇
肿瘤学   708篇
  2023年   29篇
  2022年   51篇
  2021年   175篇
  2020年   95篇
  2019年   138篇
  2018年   202篇
  2017年   122篇
  2016年   126篇
  2015年   135篇
  2014年   202篇
  2013年   296篇
  2012年   457篇
  2011年   500篇
  2010年   285篇
  2009年   248篇
  2008年   441篇
  2007年   447篇
  2006年   416篇
  2005年   376篇
  2004年   392篇
  2003年   406篇
  2002年   360篇
  2001年   119篇
  2000年   119篇
  1999年   131篇
  1998年   93篇
  1997年   78篇
  1996年   61篇
  1995年   61篇
  1994年   58篇
  1993年   39篇
  1992年   58篇
  1991年   82篇
  1990年   70篇
  1989年   53篇
  1988年   53篇
  1987年   52篇
  1986年   43篇
  1985年   38篇
  1984年   41篇
  1983年   38篇
  1982年   32篇
  1981年   36篇
  1980年   40篇
  1979年   35篇
  1978年   34篇
  1977年   31篇
  1976年   27篇
  1973年   30篇
  1968年   24篇
排序方式: 共有7668条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
ObjectiveTo examine the variability in the cesarean delivery (CD) rates of individual labor and delivery nurses compared with physicians at three attribution time points.Data SourcesMedical record data from nine hospitals in Washington State from January 2016 through September 2018.Study DesignRetrospective, observational cohort design using an aggregated database of birth records.Data Collection/Extraction MethodsChart‐abstracted clinical data from a subset of nulliparous, term, singleton, vertex births attributed at admission, labor management, and delivery to nurses and physicians. Two classification methods were used to categorize nurse‐ and physician‐level CD rates at three attribution time points and the reliability of these methods compared.Principal FindingsThe sample included 12 556 births, 319 nurses, and 126 physicians. Overall, variation in nurse‐level CD rates did not differ significantly across the three attribution time points, and the extent of variation was similar to that observed in physicians. However, agreement between attribution time points varied between 35 percent and 65 percent when classifying individual nurses into the top and bottom deciles. The average reliability of nurse‐level CD rates was 32 percent at admission (IQR 22.0 percent to 38.7 percent), 32.6 percent at labor (IQR 23.1 percent to 40.9 percent), and 29.3 percent (IQR 20.9 percent to 35.8 percent) at delivery. The average reliability of physician‐level CD rates was higher: 54.2 percent (IQR 38.7 percent to 71.4 percent) at admission, 62.5 percent (IQR 49.0 percent to 79.6 percent) at labor management, and 66.1 percent (IQR 53.7 percent to 81.2 percent) at delivery.ConclusionFeedback on nurse‐level CD rates as part of routine clinical quality audits can provide insight into nurse performance in the context of other individual‐level and unit‐level information. To reliably distinguish individual nurse performance, larger sample sizes are needed.  相似文献   
25.
PURPOSE: There is a paucity of data describing female lower limb biomechanics during "high risk" movements linked to noncontact ACL injury. This study compared, across gender, knee kinematics associated with sidestepping maneuvers to provide insight into why women display a significantly higher incidence of this injury than do men. METHODS: Thirty participants (16 men, 14 women) had bilateral knee joint kinematic data recorded while sidestepping. A custom software package (JTMOTION) quantified maximum, minimum, and range of motion during stance for each of the three clinical knee joint rotations (flexion/extension, adduction/abduction and external/internal rotation) over 20 (leg x condition x trial (5)) trials. RESULTS: Gender differences possessed limited clinical significance with all maximum values well within safe ranges of knee motion. Women did, however, display increased intertrial variability for axial rotation patterns during cutting compared with men. This variability was thought to be unaffected by gender, with experience level found statistically (P < 0.01) to be the major determinant of knee kinematic variability during sidestepping. Hence, the level of exposure to sidestep cutting may have a large impact on the subsequent risk of ACL injury when when one performs these maneuvers. CONCLUSIONS: Gender differences in knee motions during cutting did not contribute to the increased risk of noncontact ACL injury in women compared with men. The reasons for this increased incidence, therefore, remain unclear. The potential relationship between gender and other parameters linked to ACL injury such as joint geometry, ligament morphology, and physical conditioning requires further investigation.  相似文献   
26.
The host response to urinary tract infections is directed against both bacterial surface antigens, as well as bacterial products. The local response is perhaps the most important, with prevention of binding and tissue invasion as the hallmarks. Once an infection is established, the humoral immune system is most active in curtailing the damage and clearing the infecting organism. The prostate has a specialized complex of defenses that serves to reduce the incidence of infections in males.  相似文献   
27.
Invasive meningococcal disease (IMD) is thought to occur within a few days of pharyngeal acquisition of Neisseria meningitidis. During a longitudinal study of carriage and acquisition among 2453 first-year undergraduates we identified a male student from whom N. lactamica was isolated in October 1997 followed by N. meningitidis in December 1997. In mid-January 1998 this student suffered a mild episode of IMD (meningitis) during which N. meningitidis was isolated from his CSF. The meningococcus carried in December 1997 was phenotypically and genotypically indistinguishable from the invading organism, suggesting the possibility that the organism may have been carried for 7 weeks prior to the onset of invasive disease. Further studies are needed to assess more accurately the range of asymptomatic carriage prior to disease onset.  相似文献   
28.
Two methods of recruiting fertile male controls were evaluated and compared. The first group was recruited from the partners of women attending an antenatal clinic without obtaining details of their reproductive history. The second group was recruited after obtaining a detailed reproductive history from the couple and employing stringent entry criteria. Entry criteria for the second group included a length of exposure to the risk of pregnancy of not more than 12 months and no previous episode of involuntary infertility for either partner. There were significant differences between the distributions of semen parameters obtained from the two groups, indicating that the selection criteria for "fertile" men significantly influence results obtained and therefore that it is important to employ stringent criteria for the recruitment of fertile male controls. The group which was recruited by stringent criteria (mean length of exposure to the risk of pregnancy of 3 months) was characterised by a significantly higher median concentration of spermatozoa which exhibited slow linear or nonlinear motility. This confirms the findings of a previous study which suggested that slow linear or nonlinear motility are superior forms of spermatozoal motion.  相似文献   
29.
Intravenous THC, 30–44.8 g/kg, was administered to four subjects. Each received THC on four occasions preceded by either i.v. saline, 0.04 mg/kg atropine sulfate, 0.2 mg/kg propranolol, or both drugs together. Heart rates, subjective intoxication and symptom ratings, time productions, and EEG activity were measured. In the absence of autonomic blocking drugs, THC produced characteristic tachycardia, subjective intoxication, and EEG effects. After combined autonomic blockade, THC had no effect on heart rate, while subjective and EEG changes remained as intense. These findings argue against the hypothesis that the subjective and EEG effects of THC are mediated by autonomic receptors or by interoception of peripheral autonomic actions of THC.To whom offprint requests should be sent  相似文献   
30.
Summary Varying doses of TCDD ranging from 25 to 1000 g/kg were administered to the larval and adult forms of the American bullfrog,Rana catesbeiana. Doses of TCDD as high as 1 mg/kg failed to have any significant effect upon survival or completion of metamorphosis in tadpole and doses of up to 500 g/kg had no effect on survival of adult frogs. Histopathological examination of various tissues from the metamorphosed tadpoles and adult frogs failed to show any abnormalities.This work was supported by USPHS Grant ES00267. The Training support of ES 07028 is also gratefully acknowledged.  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