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   19842篇
  免费   1771篇
  国内免费   93篇
耳鼻咽喉   225篇
儿科学   569篇
妇产科学   576篇
基础医学   2391篇
口腔科学   285篇
临床医学   2820篇
内科学   4727篇
皮肤病学   283篇
神经病学   1321篇
特种医学   888篇
外科学   2850篇
综合类   321篇
一般理论   9篇
预防医学   1356篇
眼科学   634篇
药学   1141篇
中国医学   50篇
肿瘤学   1260篇
  2023年   125篇
  2022年   133篇
  2021年   286篇
  2020年   217篇
  2019年   371篇
  2018年   416篇
  2017年   387篇
  2016年   377篇
  2015年   427篇
  2014年   601篇
  2013年   850篇
  2012年   1101篇
  2011年   1091篇
  2010年   739篇
  2009年   725篇
  2008年   1106篇
  2007年   1175篇
  2006年   1192篇
  2005年   1113篇
  2004年   1080篇
  2003年   1044篇
  2002年   966篇
  2001年   334篇
  2000年   300篇
  1999年   295篇
  1998年   296篇
  1997年   295篇
  1996年   251篇
  1995年   285篇
  1994年   214篇
  1993年   169篇
  1992年   228篇
  1991年   190篇
  1990年   180篇
  1989年   192篇
  1988年   202篇
  1987年   181篇
  1986年   170篇
  1985年   153篇
  1984年   143篇
  1983年   151篇
  1982年   153篇
  1981年   133篇
  1980年   131篇
  1979年   102篇
  1978年   114篇
  1977年   123篇
  1976年   96篇
  1975年   74篇
  1974年   68篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
52.
53.
In July 1986, a provisional clinical case definition of AIDS in children, developed by the World Health Organization (WHO) for surveillance purposes in Africa, was tested on 159 patients hospitalized in the Department of Pediatrics at Mama Yemo Hospital, Kinshasa, Zaire. Twenty-one (13%) of these children were seropositive for HIV. In this population, the clinical case definition of pediatric AIDS was found to be fairly specific (87%) but lacked sensitivity (35%). The positive predictive value for HIV seropositivity was 25%. This study suggests that it is more difficult to define AIDS clinically in children than in adults and that the utility of the proposed WHO clinical case definition for pediatric AIDS for surveillance of children's AIDS in Africa is limited.  相似文献   
54.
The xanthine oxidase catalysed release of superoxide free radicals (O2-) from endogenous hypoxanthine was determined in homogenates of synovium obtained from three groups of patients, those undergoing primary or revision total hip replacement (THR) for osteoarthritis and those undergoing arthroscopy of the knee for semilunar disc injuries. The concentrations of hypoxanthine in homogenates obtained during THR were found to be significantly higher than those in the group with semilunar disc injuries. The results suggest that there is a greater predisposition to free radical release and tissue damage in osteoarthritis.  相似文献   
55.
AIM: The aim of this study was to investigate the nature and organization of maternal needs and priorities in a neonatal unit. BACKGROUND: The relationship between maternal needs and priorities appears to be an under studied area in neonatal nursing. METHODS: A quantitative survey was carried out based on 209 mothers with premature infants. Two self-assessment schedules were used: critical care maternal needs inventory (J. Leske, Heart and Lung 15, 27-42) and a ranking scale. The data were analysed with multivariate analysis. FINDINGS: Data analysis revealed clear priorities in maternal needs. In particular the need for accurate infant related information was a priority for 93% of the mothers. Good communication practices with professionals were also valued. The mothers displayed altruistic behaviour, and self-related needs took second place. It is proposed that maternal needs demonstrate a hierarchical organization. CONCLUSION: It is important for nurses to consider the individual needs of the mothers, simply because the satisfaction of these needs is essential for maternal well-being.  相似文献   
56.
Background: Voiding before discharge is usually required after outpatient epidural or spinal anesthesia because of concern about bladder overdistention and dysfunction. Shorter duration spinal and epidural anesthesia may allow return of bladder function before overdistention occurs in low-risk patients (those younger than age 70, not having hernia, rectal, or urologic surgery, and without a history of voiding difficulty), and predischarge voiding may not be necessary.

Methods: After institutional review board approval and informed consent, 201 low-risk ambulatory patients were prospectively studied in either a standard or accelerated pathway after undergoing spinal or epidural anesthesia with procaine, lidocaine, 2-chloroprocaine, or less than 7 mg bupivacaine; epinephrine was not used in any anesthetic. Standard pathway patients (n = 70) were required to void before discharge. Accelerated pathway (n = 131) patients were not required to void. (After randomization of an initial 163 patients to one of the two tracks, 38 additional patients were assigned to the accelerated pathway.) If accelerated pathway patients voided, they were discharged when all other discharge criteria were met. If they did not spontaneously void after block resolution, a bladder ultrasound (BUS) was performed. If the BUS indicated a urine volume of less than 400 ml, the patients were discharged and instructed to return to the emergency department if they were unable to void within 8 h of discharge. If the BUS indicated a urine volume of greater than 400 ml, the patients were reassessed in 1 h and were discharged if they could void spontaneously. If they could not void spontaneously, they were catheterized to facilitate discharge. All patients were contacted the next day to assess the return of normal bladder function.

Results: All standard pathway patients voided without difficulty, and were discharged in 153 +/- 49 (SD) min. 62 patients in the accelerated pathway voided spontaneously after resolution of their block and were discharged in 127 +/- 41 min. 46 patients were discharged with a BUS less than 400 ml in 120 +/- 42 min. 23 patients had a BUS greater than 400 ml: of these, 20 patients voided within an hour and were discharged in 162 +/- 45 min. Three were catheterized after 1 h, and were discharged in 186 +/- 61 min. Mean discharge time for all patients in the accelerated pathway was 22 min shorter than the standard pathway (P = 0.002). No patients had difficulty voiding or returned to the hospital for urinary problems. None reported new urologic symptoms.  相似文献   

57.
BACKGROUND: Pravastatin and simvastatin prolong survival and reduce transplant-related coronary vasculopathy, although low-density lipoprotein (LDL) lowering with these agents is only modest. The objective of this study was to assess the safety of moderate dose atorvastatin and its efficacy when prior treatment with another statin had failed to lower LDL to < 100 mg/dl. METHODS: Data from 185 patients were retrospectively evaluated for adverse events, duration of exposure (person-days), and the mean atorvastatin dose exposure. Changes in lipid parameters, and prednisone and cyclosporine doses were determined. RESULTS: Safety: 48 patients received atorvastatin for 24,240 person-days at a mean dose exposure of 21 +/- 10 mg. Rhabdomyolysis, myositis, myalgias, and hepatotoxicity occurred in 0, 2, 2, and 0 patients, respectively. All events occurred at the 10-mg dose, within the first 3 months, and were rapidly reversible with atorvastatin discontinuation. Efficacy: Thirty-four patients evaluable for efficacy analyses had a pre-atorvastatin LDL of 145 +/- 38 mg/dl on the following statins: pravastatin (n = 30, 40 +/- 0mg), fluvastatin (n = 3, 33 +/- 12 mg), simvastatin (n = 1, 40 mg). After atorvastatin (21 +/- 9 mg/day) for 133 +/- 67 days, LDL was reduced to 97 +/- 24 mg/dl (relative reduction 31 +/- 20%, p < 0.0001). At the end of the observation period (418 +/- 229 days, atorvastatin final dose 24 +/- 14 mg/day), LDL was further decreased to 88 +/- 23 mg (relative reduction 37 +/- 17%, p < 0.0001). CONCLUSION: Atorvastatin, when used at moderate doses and with close biochemical and clinical monitoring, appears to be safe and is effective in aggressively lowering LDL in heart transplant recipients when treatment with other statins has failed to achieve LDL goals.  相似文献   
58.
59.
The antigenic relationships among different hepatitis B virus (HBV) isolates were investigated by using monoclonal antibodies (MAbs) specific for HBs, preS2 (pHSA binding site), and preS1 (hepatocyte receptor-binding site) epitopes in a double immunoradiometric assay. In order to define possible functional differences resulting from structural and antigenic differences in the HBV env protein, the HBV isolates were compared in an in vitro cell-binding assay based on the attachment of 125I-labeled HBV to human hepatoma HepG2 cells. We provided evidence for a variability of the expression of preS1 and preS2 specificities in the peplomer (glyco)protein of HBV depending on d/ysubtype of HBsAg, which could affect the viral infectivity. We showed that the integrity of the HBV envelope structure associated with a large expression of preS1(21–47) epitopes is an essential factor for effective binding to HepG2 cells. Interestingly, the HBs-specific MAbs directed to disulfide-bond-dependent epitopes were found to be the best inhibitors of the preS1-HepG2 cell interaction (>50% at the final concentration of 0.5 μg/ml). The MAb F35.25 directed to the preS1(21–47) sequence corresponding to the hepatocyte receptor recognition site was, however, also found to inhibit binding. Thus, our results demonstrate the abilities of both anti-HBs and anti-preS(21–41) to block the attachment of complete HBV particles to HepG2 cells, suggesting that these antibodies should be virus neutralizing and would be expected to confer protection against reinfection.  相似文献   
60.
Chronic bronchitis in textile workers   总被引:4,自引:0,他引:4       下载免费PDF全文
BACKGROUND: Exposure to cotton is known to produce a specific occupational disease known as byssinosis. A large population of textile workers was investigated to determine whether such exposure was also associated with chronic bronchitis once other possible aetiological factors had been accounted for. METHODS: A total of 2991 workers were investigated for the presence of symptoms compatible with chronic bronchitis. An MRC adapted respiratory questionnaire and MRC definition of chronic bronchitis were used for diagnostic labelling. Current and lifetime exposure to dust was estimated by personal and work area sampling, and the use of records of retrospective dust levels previously measured over the preceding 10 years. Airborne endotoxin exposure was measured using a quantitative turbidometric assay. Lung function tests were performed to measure forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). A control group of workers exposed to man-made fibre textiles was identified. The comparative prevalence of chronic bronchitis in the two populations was assessed, allowing for sex, age, smoking habit, and ethnic origin. Two case referent studies were also performed; cases of chronic bronchitis were separately matched with controls from the cotton and control populations to determine the effect of the symptomatic state on lung function. RESULTS: After controlling for smoking (pack years), workers in a cotton environment were significantly more likely to suffer from chronic bronchitis and this was most marked in workers over 45 years of age (odds ratio 2.51 (CI 1.3 to 4.9); p < 0.01). Regression analysis of all possible influencing parameters showed that cumulative exposure to cotton dust was significantly associated with chronic bronchitis after the effects of age, sex, smoking, and ethnic group were accounted for (p < 0.0005). In the intra-cotton population case control study a diagnosis of chronic bronchitis was associated with a small decrement in lung function compared with controls: percentage predicted FEV1 in cases 81.4% (95% CI 78.3 to 84.6), controls 86.7% (84.9 to 88.5); FVC in cases 89.9% (95% CI 87.0 to 92.9), controls 94.6% (92.8 to 96.4). After controlling for cumulative past exposure and pack years of smoking the effect of the diagnostic state remained significant for both FEV1 (p < 0.01) and FVC (p < 0.05). CONCLUSIONS: Chronic bronchitis is more prevalent in cotton workers than in those working with man-made fibre and exposure is additive to the effect of smoking. The diagnosis of chronic bronchitis is associated with a small but significant decrement in lung function.


  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