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   3808篇
  免费   329篇
  国内免费   23篇
耳鼻咽喉   44篇
儿科学   58篇
妇产科学   36篇
基础医学   434篇
口腔科学   148篇
临床医学   353篇
内科学   872篇
皮肤病学   74篇
神经病学   232篇
特种医学   111篇
外科学   551篇
综合类   204篇
预防医学   260篇
眼科学   218篇
药学   186篇
中国医学   32篇
肿瘤学   347篇
  2023年   40篇
  2022年   63篇
  2021年   123篇
  2020年   96篇
  2019年   104篇
  2018年   164篇
  2017年   107篇
  2016年   102篇
  2015年   123篇
  2014年   161篇
  2013年   176篇
  2012年   229篇
  2011年   296篇
  2010年   147篇
  2009年   127篇
  2008年   209篇
  2007年   215篇
  2006年   236篇
  2005年   163篇
  2004年   205篇
  2003年   179篇
  2002年   120篇
  2001年   97篇
  2000年   87篇
  1999年   74篇
  1998年   23篇
  1997年   23篇
  1996年   21篇
  1995年   13篇
  1994年   10篇
  1993年   18篇
  1992年   39篇
  1991年   44篇
  1990年   37篇
  1989年   37篇
  1988年   43篇
  1987年   31篇
  1986年   32篇
  1985年   16篇
  1984年   11篇
  1983年   15篇
  1980年   8篇
  1979年   13篇
  1977年   10篇
  1976年   5篇
  1975年   8篇
  1974年   9篇
  1972年   7篇
  1971年   8篇
  1970年   6篇
排序方式: 共有4160条查询结果,搜索用时 15 毫秒
21.
Nitschke JE  Nattrass CL  Disler PB  Chou MJ  Ooi KT 《Spine》1999,24(3):262-268
STUDY DESIGN: Repeated measures design for intra- and interrater reliability. OBJECTIVES: To determine the intra- and interrater reliability of the lumbar spine range of motion measured with a dual inclinometer, and the thoracolumbar spine range of motion measured with a long-arm goniometer, as recommended in the American Medical Association Guides. SUMMARY OF BACKGROUND DATA: The American Medical Association Guides (2nd and 4th editions) recommend using measurements of thoracolumbar and lumbar range of movement, respectively, to estimate the percentage of permanent impairment in patients with chronic low back pain. However, the reliability of this method of estimating impairment has not been determined. METHODS: In all, 34 subjects participated in the study, 21 women with a mean age of 40.1 years (SD, +/- 11.1) and 13 men with a mean age of 47.7 years (SD, +/- 12.1). Measures of thoracolumbar flexion, extension, lateral flexion, and rotation were obtained with a long-arm goniometer. Lumbar flexion, extension, and lateral flexion were measured with a dual inclinometer. Measurements were taken by two examiners on one occasion and by one examiner on two occasions approximately 1 week apart. RESULTS: The results showed poor intra- and interrater reliability for all measurements taken with both instruments. Measurement error expressed in degrees showed that measurements taken by different raters exhibited systematic as well as random differences. As a result, subjects measured by two different examiners on the same day, with either instrument, could give impairment ratings ranging between 0% and 18% of the whole person (excluding rotation), in which percentage impairment is calculated using the average range of motion and the average systematic and random error in degrees for the group for each movement (flexion, extension, and lateral flexion). CONCLUSIONS: The poor reliability of the American Medical Association Guides' spinal range of motion model can result in marked variation in the percentage of whole-body impairment. These findings have implications for compensation bodies in Australia and other countries that use the American Medical Association Guides' procedure to estimate impairment in chronic low back pain patients.  相似文献   
22.
BACKGROUND: Tics are involuntary, brief, stereotyped motor and vocal behaviors often associated with irresistible urges. They are a defining symptom of the classic neuropsychiatric disorder, Tourette syndrome (TS), and constitute an example of disordered human volition. The neural correlates of tics are not well understood and have not been imaged selectively. METHODS: Event-related [(15)O]H(2)O positron emission tomography techniques combined with time-synchronized audio and videotaping were used to determine the duration of, frequency of, and radiotracer input during tics in each of 72 scans from 6 patients with TS. This permitted a voxel-by-voxel correlational analysis within Statistical Parametric Mapping of patterns of neural activity associated with the tics. RESULTS: Brain regions in which activity was significantly correlated with tic occurrence in the group included medial and lateral premotor cortices, anterior cingulate cortex, dorsolateral-rostral prefrontal cortex, inferior parietal cortex, putamen, and caudate, as well as primary motor cortex, the Broca's area, superior temporal gyrus, insula, and claustrum. In an individual patient with prominent coprolalia, such vocal tics were associated with activity in prerolandic and postrolandic language regions, insula, caudate, thalamus, and cerebellum, while activity in sensorimotor cortex was noted with motor tics. CONCLUSIONS: Aberrant activity in the interrelated sensorimotor, language, executive, and paralimbic circuits identified in this study may account for the initiation and execution of diverse motor and vocal behaviors that characterize tics in TS, as well as for the urges that often accompany them. Arch Gen Psychiatry. 2000;57:741-748  相似文献   
23.
Acquired cystic disease of the kidney and renal cell carcinoma are associated with chronic renal failure. In recent years, there has been increased incidental detection of renal tumours through the liberal use of ultrasonography (US) and computed tomography (CT). A 40-year-old man suffering from chronic renal failure and who was being treated with haemodialysis for six years, was found to have a complex cystic lesion on US and CT. Nephrectomy was performed and the lesion was confirmed to be renal cell carcinoma associated with acquired cystic kidney disease. The current role of imaging in the management of affected patients are discussed.  相似文献   
24.
Transabdominal duplex Doppler ultrasonography (TDDU) is commonly used for measuring hepatic blood flow (HBF) in clinical practice. Flow velocity and the cross-sectional area (CSA) of vessels are obtained separately and used to compute blood flow. Respiration and changes in portal pressure are known to cause variations in the CSA of the portal vein, but the impact of these parameters on TDDU measurement of portal blood flow is unclear. Eight Yorkshire pigs (20.7-25.1 kg) were used for the study. TDDU determination of portal blood flow was carried out using CSA of the portal vein obtained at inspiration (maximal) and at expiration (minimal) for computation, and the differences obtained were compared. Determination of HBF was carried out simultaneously on the same animals using diisopropyliminodiacetic acid (DISIDA) clearance. A physiological increase in portal pressure was then created by 50% hepatectomy and TDDU measurement similarly carried out on the second postoperative day. Computing portal blood flow in the intact liver using maximal and minimal CSA gave rise to a mean difference of 7.0 ml kg(-1) min(-1) (P < 0.001). A significant correlation was obtained between HBF and portal flow computed from maximal CSA (Pearson's correlation = 0.85, P < 0.033). The respiratory index of the portal vein (maximal CSA/minimal CSA) decreased from 1.5 to 1.2 after hepatectomy, which also caused a 90% increase in portal pressure. Respiration and portal pressure thus significantly impact on TDDU determination of HBF, and in this porcine model, computation using maximal CS more accurately reflects HBF.  相似文献   
25.
PURPOSE: In the present study, we investigated the degree of protein expression and gene amplification of HER-2 in esophageal squamous cell carcinoma (SCC) cell lines and freshly isolated tumors, and trastuzumab-mediated biological activity, in particular antibody-dependent cellular cytotoxicity (ADCC) against HER-2-expressing esophageal SCC cell lines. EXPERIMENTAL DESIGN: Ten different SCC cell lines with various levels of HER-2 status evaluated by flow cytometry, immunocytochemistry (HercepTest), and fluorescence in situ hybridization were evaluated for ADCC, growth inhibitory, or apoptosis-inducing activities mediated by trastuzumab. RESULTS: Trastuzumab induced ADCC against HER-2-expressing esophageal SCC and the activities reflected the degree of HER-2 expression analyzed by flow cytometric analysis, but not by HercepTest nor fluorescence in situ hybridization analysis. Furthermore, trastuzumab-mediated ADCC against transforming growth factor-beta-producing SCC was enhanced by the treatment with SB-431542, which is a selective inhibitor of the phosphorylation induced by transforming growth factor-beta. There were very marginal effects of anti-proliferative or apoptosis-inducing activities mediated by trastuzumab for HER-2-expressing esophageal SCC. CONCLUSION: HER-2-expressing esophageal SCC cells could be killed by trastuzumab-mediated ADCC and the activity reflected the degree of HER-2 expression detected by flow cytometry.  相似文献   
26.
Photocatalytic water splitting has garnered tremendous attention for its capability to produce clean and renewable H2 fuel from inexhaustible solar energy. Until now, most research has focused on scarce pure water as the source of H2, which is not consistent with the concept of sustainable energy. Hence, the importance of photocatalytic splitting of abundant seawater in alleviating the issue of pure water shortages. However, seawater contains a wide variety of ionic components which have unknown effects on photocatalytic H2 production. This work investigates photocatalytic seawater splitting conditions using environmentally friendly amorphous carbon nitride (ACN) as the photocatalyst. The individual effects of catalyst loading (X1), sacrificial reagent concentration (X2), salinity (X3), and their interactive effects were studied via the Box–Behnken design in response surface modeling towards the H2 evolution reaction (HER) from photocatalytic artificial seawater splitting. A second-order polynomial regression model is predicted from experimental data where the variance analysis of the regressions shows that the linear term (X1, X2), the two-way interaction term X1X2, and all the quadratic terms (X12, X22, X23) pose significant effects towards the response of the HER rate. Numerical optimization suggests that the highest HER rate is 7.16 µmol/h, achievable by dosing 2.55 g/L of ACN in 45.06 g sea salt/L aqueous solution containing 17.46 vol% of triethanolamine. Based on the outcome of our findings, an apparent effect of salt ions on the adsorption behavior of the photocatalyst in seawater splitting with a sacrificial reagent has been postulated.  相似文献   
27.
Two new antiviral flavan derivatives were isolated from a methanol extract of leaves of Pithecellobium clypearia as guided by antiviral assays. The structures were characterized, by spectroscopic analyses, as 7-O-galloyltricetifavan (1) and 7,4'-di-O-galloyltricetifavan (2). Cytopathic effect (CPE) reduction assay showed that both compounds 1 and 2 possess antiviral activity against respiratory syncytial virus (RSV), with 50% inhibition concentration (IC(50)) values of 5 and 10 microg/mL, respectively; influenza A (H1N1) virus, with IC(50) values of 15.7 and 30 microg/mL; Coxsackie B3 (Cox B3) virus, with IC(50) values of 12.5 and 25 microg/mL, respectively; and Herpes simplex virus type 1 (HSV-1) with IC(50) values of 30 and 20 microg/mL, respectively. Cytotoxicity evaluation using the MTT assay showed that both compounds 1 and 2 were also moderately toxic to several cultured cell lines.  相似文献   
28.
[Purpose] To consider the effective rehabilitation approaches for locomotive syndrome (LS) and pre-frailty, we examined the characteristics of physical function and health-related quality of life (HRQoL) in community-dwelling older adults. [Participants and Methods] Eighty-three individuals (age 71.8 ± 5.5 years, 29 males and 54 females) were divided into robust (R), LS, and locomotive syndrome with pre-frailty (LSP) groups. We compared the subscale and summary scores of the 36-Item Short-Form Health Survey (SF-36) as HRQoL indices. The grip strength, five-chair stand up test (SS-5), and normal walking speed were the physical function indices. [Results] The LS group had lower two-step scores and normal walking speed but there was no significant difference in the SF-36. The two-step score and 25-question geriatric locomotive function scale, SS-5, seven SF-36 subscales, and mental component summary (MCS) scores were lower in the LSP group. Compared to that of the LS group, the LSP group did not show significant difference in physical function but showed lower values in overall health, vitality, mental health, and MCS in the SF-36 subscales. [Conclusion] The subjective evaluation of one’s health was lower than that of the deterioration of physical function as a characteristic of the LSP.  相似文献   
29.
Using a feminist approach, we examined the menopausal symptom experience of Hispanic midlife women in the United States This was a qualitative online forum study among 27 Hispanic midlife women in the United States. Seven topics related to menopausal symptom experience were used to administer the 6-month online forum. The data were analyzed using thematic analysis. Four themes were identified: (a) “Cambio de vida (change of life),” (b) “being silent about menopause,” (c) “trying to be optimistic,” and (d) “getting support.” More in-depth studies with diverse groups of Hispanic women are needed while considering family as a contextual factor.  相似文献   
30.
Our purpose in this study was to identify differences in menopausal symptom management among four major ethnic groups in the United States. This was a secondary analysis of the qualitative data from a larger Internet-based study. We analyzed data from 90 middle-aged women in the United States using thematic analysis. We extracted four themes during the data analysis process: (a) “seeking formal or informal advice,” (b) “medication as the first or final choice,” (c) “symptom-specific or holistic,” and (d) “avoiding or pursuing specific foods.” Health care providers need to develop menopausal symptom management programs while considering ethnic differences in menopausal symptom management.  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