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   1091277篇
  免费   72343篇
  国内免费   1652篇
耳鼻咽喉   15777篇
儿科学   30125篇
妇产科学   27304篇
基础医学   156285篇
口腔科学   32584篇
临床医学   92638篇
内科学   211775篇
皮肤病学   23622篇
神经病学   87127篇
特种医学   44858篇
外国民族医学   104篇
外科学   177367篇
综合类   19057篇
现状与发展   1篇
一般理论   273篇
预防医学   69415篇
眼科学   25592篇
药学   83862篇
  3篇
中国医学   2505篇
肿瘤学   64998篇
  2018年   11606篇
  2017年   9175篇
  2016年   10748篇
  2015年   12195篇
  2014年   15581篇
  2013年   22536篇
  2012年   31748篇
  2011年   32294篇
  2010年   19149篇
  2009年   17938篇
  2008年   31620篇
  2007年   33523篇
  2006年   34266篇
  2005年   33577篇
  2004年   32351篇
  2003年   31421篇
  2002年   30797篇
  2001年   59734篇
  2000年   61630篇
  1999年   51497篇
  1998年   12274篇
  1997年   10729篇
  1996年   10572篇
  1995年   9775篇
  1994年   9039篇
  1993年   8317篇
  1992年   37670篇
  1991年   36022篇
  1990年   34895篇
  1989年   33852篇
  1988年   30752篇
  1987年   29977篇
  1986年   27958篇
  1985年   26768篇
  1984年   19107篇
  1983年   16187篇
  1982年   8518篇
  1981年   7431篇
  1979年   17171篇
  1978年   11621篇
  1977年   9923篇
  1976年   8609篇
  1975年   9705篇
  1974年   11566篇
  1973年   10868篇
  1972年   10368篇
  1971年   9841篇
  1970年   9300篇
  1969年   8741篇
  1968年   7982篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
994.
995.
BACKGROUND: Dialysis patient mortality remains high, and this high mortality may be due to many factors. In peritoneal dialysis (PD) patients, old age, co-morbid diseases, malnutrition, low residual renal function (RRF) and a high peritoneal transport rate have been shown to influence survival, but the relative importance of these factors may differ between different patient populations. Besides, centre practice patterns may differ between centres and may influence patient survival. In addition, the literature suggests that dialysis patient survival may be better in Asian than in Caucasian patients. METHODS: The influence of centre and patient characteristics on patient survival was investigated in 132 Korean and 106 Swedish incident PD patients, who underwent initial biochemical measurements and assessment of adequacy of dialysis, nutritional status, RRF and peritoneal transport characteristics. RESULTS: At the start of PD, Korean patients had a higher prevalence of diabetes, peritoneal Kt/V(urea), peritoneal creatinine clearance and peritoneal fluid removal, and lower body mass index, RRF and dialysate to plasma creatinine concentration ratio (D/P Cr) compared with Swedish patients. Significantly more patients from Korea were placed on temporary haemodialysis before PD (100 out of 132) when compared with Swedish patients (21 out of 106). During the follow-up, there was a significantly higher rate of transfer to other units in Korea and a significantly higher rate of kidney transplantation in Sweden. On Kaplan-Meier analysis, overall patient survival did not differ and relative risk for death was also not different between the two centres even after adjustment for age, diabetes, cardiovascular disease, RRF and D/P Cr. On Cox proportional hazards multivariate analysis, age, diabetes, RRF and D/P Cr were found to be independent predictors of mortality in the combined cohort of patients. While age, diabetes and D/P Cr were independent predictors of mortality in Korean patients, age and RRF independently predicted mortality in Swedish patients. CONCLUSION: Although there were significant differences in centre and patient characteristics, we were unable to confirm a survival advantage for Korean over Swedish PD patients. The results of this study suggest that the reported difference in survival between Asian and Caucasian dialysis patients may have been due, in part, to differences in centre and patient characteristics rather than to race as such. The genetic influence on patient characteristics remains, however, to be elucidated.  相似文献   
996.
BACKGROUND: Past receiver operating characteristic (ROC) studies have demonstrated that single photon emission computed tomography (SPECT) perfusion imaging by use of iterative reconstruction with combined compensation for attenuation, scatter, and detector response leads to higher area under the ROC curve (A(z)) values for detection of coronary artery disease (CAD) in comparison to the use of filtered backprojection (FBP) with no compensations. A new ROC study was conducted to investigate whether this improvement still holds for iterative reconstruction when observers have available all of the imaging information normally presented to clinical interpreters when reading FBP SPECT perfusion slices. METHODS AND RESULTS: A total of 87 patient studies including 50 patients referred for angiography and 37 patients with a lower than 5% likelihood for CAD were included in the ROC study. The images from the two methods were read by 4 cardiology fellows and 3 attending nuclear cardiologists. Presented for the FBP readings were the short-axis, horizontal long-axis, and vertical long-axis slices for both the stress and rest images; cine images of both the stress and rest projection data; cine images of selected cardiac-gated slices; the CEQUAL-generated stress and rest polar maps; and an indication of patient gender. This was compared with reading solely the iterative reconstructed stress slices with combined compensation for attenuation, scatter, and resolution. With A(z) as the criterion, a 2-way analysis of variance showed a significant improvement in detection accuracy for CAD for the 7 observers (P = .018) for iterative reconstruction with combined compensation (A(z) of 0.895 +/- 0.016) over FBP even with the additional imaging information provided to the observers when scoring the FBP slices (A(z) of 0.869 +/- 0.030). When the groups of 3 attending physicians or 4 cardiology fellows were compared separately, the iterative technique was not statistically significantly better; however, the A(z) for each of the 7 observers individually was larger for iterative reconstruction than for FBP. Compared with results from our previous studies, the additional imaging information did increase the diagnostic accuracy of FBP for CAD but not enough to undo the statistically significantly higher diagnostic accuracy of iterative reconstruction with combined compensation. CONCLUSIONS: We have determined through an ROC investigation that included two classes of observers (experienced attending physicians and cardiology fellows in training) that iterative reconstruction with combined compensation provides statistically significantly better detection accuracy (larger A(z)) for CAD than FBP reconstructions even when the FBP studies were read with all of the extra clinical nuclear imaging information normally available.  相似文献   
997.
Abstrakt Nach § 13 Abs. 2 S. 1 BPflV 1995 ist als Entgelt für ?rztliche und pflegerische T?tigkeit und die dadurch veranlassten Leistungen für jede organisatorisch selbstst?ndige bettenführende Abteilung, die von einem fachlich nicht weisungsgebundenen Arzt mit entsprechender Fachgebietsbezeichnung geleitet wird, ein Abteilungspflegesatz zu vereinbaren und bei Nichtvereinbarung durch die Schiedsstelle festzusetzen (§ 18 Abs. 4 KHG). Der Bildung eines Abteilungspflegesatzes steht nicht entgegen, dass keine dem Leistungsspektrum der Abteilung deckungsgleiche Facharztbezeichnung existiert, sofern der Leiter der Abteilung über eine Facharztbzw. Fachgebietsbezeichnung verfügt (hier: Fach?rztin für Psychiatrie und Psychotherapie), die die in der Abteilung zu bew?ltigenden Aufgaben (hier: Gerontopsychiatrie) umfasst. (Leits?tze des Bearbeiters)  相似文献   
998.
999.
The pathophysiology of akathisia still remains controversial. Iron deficiency was proposed to be an important factor in the development of akathisia. In the present study, it was aimed to compare levels of serum iron and linked variables in chronic akathisic (n=30), and non-akathisic patients (n=30) with schizophrenia and healthy controls (n=30) because of the controversy in the association of iron and akathisia. The Barnes Akathisia Scale for akathisia and Simpson-Angus Rating Scale for extrapyramidal side effects were used. Serum iron and linked variables and hematological profile of the patients and control subjects were determined. Serum iron levels were significantly lower both in akathisic and non-akathisic groups compared to the control group (P<0.001). Moreover, akathisic patients had significantly lower iron levels than non-akathisic patients (P<0.05). Total iron binding capacity was significantly higher in patients with akathisia compared to the control group (P<0.01). Although non-akathisic patients had a mild increase in total iron binding capacity, it was not statistically significant compared to the control group (P>0.05). Ferritin levels were determined to be significantly lower in both groups compared to the control group (P<0.01). In addition, there was a significant difference in ferritin levels between the patients with and without akathisia (P<0.05). In conclusion, our results support the hypothesis that an association between akathisia and iron metabolism exists.  相似文献   
1000.
The objective of this study was to investigate the swelling characteristics of various swellable polymers in swelling layers that induce the rupturing of an outer polymer coating in pulsatile drug delivery systems (DDS). An apparatus was designed to measure simultaneously the swelling energy/force and water uptake of discs, made of polymers. The swelling energy of several excipients decreased in the following order: croscarmellose sodium (Ac-Di-Sol) > low-substituted hydroxypropyl cellulose (L-HPC) > sodium starch glycolate (Explotab) > crospovidone (Kollidon CL) > hydroxypropyl methylcellulose (Methocel K100M). A linear correlation existed between the swelling energy and the water uptake. The swelling behavior of Ac-Di-Sol depended on the ionic strength and the pH of the medium due to a competition for free water and the acidic nature of this polymer. Analysis of the time-dependent swelling force data with a previously developed exponential equation confirmed a diffusion-controlled swelling force development, predominantly controlled by the penetration rate of the medium. The swelling behavior and the rupture of the outer polymeric coating of a pulsatile DDS were demonstrated in simulation tests.  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