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   14342篇
  免费   680篇
  国内免费   118篇
耳鼻咽喉   95篇
儿科学   276篇
妇产科学   416篇
基础医学   1785篇
口腔科学   355篇
临床医学   976篇
内科学   4055篇
皮肤病学   221篇
神经病学   1327篇
特种医学   585篇
外科学   2183篇
综合类   37篇
一般理论   1篇
预防医学   509篇
眼科学   156篇
药学   730篇
中国医学   25篇
肿瘤学   1408篇
  2024年   12篇
  2023年   90篇
  2022年   206篇
  2021年   418篇
  2020年   210篇
  2019年   298篇
  2018年   396篇
  2017年   292篇
  2016年   330篇
  2015年   371篇
  2014年   561篇
  2013年   715篇
  2012年   994篇
  2011年   1020篇
  2010年   650篇
  2009年   590篇
  2008年   1016篇
  2007年   1011篇
  2006年   922篇
  2005年   969篇
  2004年   869篇
  2003年   805篇
  2002年   719篇
  2001年   122篇
  2000年   90篇
  1999年   116篇
  1998年   148篇
  1997年   110篇
  1996年   131篇
  1995年   88篇
  1994年   98篇
  1993年   79篇
  1992年   73篇
  1991年   60篇
  1990年   61篇
  1989年   44篇
  1988年   32篇
  1987年   24篇
  1986年   37篇
  1985年   35篇
  1984年   34篇
  1983年   26篇
  1982年   34篇
  1981年   34篇
  1980年   31篇
  1979年   22篇
  1977年   9篇
  1976年   10篇
  1974年   9篇
  1964年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Unregulated or increased expression of epidermal growth factor receptor (EGF-R) is a common event in neoplastic transformation; modulation of such a receptor by physiological agents could be, therefore, of clinical interest. We have studied the binding ability, the availability at cell surface, and the synthesis of EGF-R in the A431 and KB human epidermoid cancer cell lines after treatment with recombinant alpha-interferon (IFN-alpha). After 48 h of treatment, IFN-alpha induces, in both cell lines, growth inhibition and enhances class I major histocompatibility HLA complex expression, which is a common marker of IFN action. [125I]EGF total binding assessed after 48 h of treatment with IFN-alpha shows a dose-dependent upregulation of EGF-R binding capacity. Saturation plots of the binding data show that IFN-alpha treatment does not dramatically alter the affinity of the EGF-R and indicate that IFN-alpha only increases the number of low affinity receptors. We show that this effect is due to a specific increase in the synthesis of the receptor protein, as assessed by immunoprecipitation of [35S]methionine-labeled cell extracts. Electron microscopy analysis has confirmed an increase of EGF-R proteins at cell surface without major changes in the morphology of the cells. Taken together, these results indicate that IFN-alpha consistently induces both the binding capacity and the synthesis of EGF-R in human epidermoid cancer cells and suggest the use of such a mechanism for new anticancer therapies.  相似文献   
12.
Prevalence of isolated left ventricular (LV) diastolic dysfunction has been reported to be as high as one-third of all heart failure (HF) cases, with an increasing prevalence in the elderly population. However, there is a paucity of prospective data about the prevalence and prognosis of isolated LV diastolic dysfunction in an unselected population of patients hospitalized with HF. Therefore, we prospectively evaluated 179 consecutive patients discharged from our hospital with HF to assess the prevalence of systolic versus diastolic LV dysfunction among patients hospitalized with HF and to compare their demographics, clinical features, self-perceived quality of life (QOL), and 6-month readmission rate and mortality. Among them, 133 (59% men, median age 74 years) showed in sinus rhythm and had no significant primary valvular disease. LV diastolic dysfunction was diagnosed on the basis of the European Study Group on Diastolic HF echocardiographic criteria. QOL was assessed at hospital discharge and 6-month follow-up visit using the Minnesota Living with HF questionnaire. Survival of patients with HF was compared with that of age- and sex-matched general population. In all, 29 patients (22%) had isolated LV diastolic dysfunction and 102 (78%) had prevalent LV systolic dysfunction (ie, LV ejection fraction 相似文献   
13.
Insomnia in psychiatric patients is frequently underestimated in clinical practice. Usually drugs are prescribed for the treatment of this disorder but non-pharmacological intervention can be successfully used. The present study aimed at evaluating the efficacy of a two-session psychoeducational intervention in improving persistent non-organic insomnia and reducing the administration of PRN therapy in severely mentally ill patients. A pre-post study was performed on 36 psychiatric patients admitted to a residential psychiatric unit. The Nocturnal Sleep Onset Scale (NSOS) and Daytime Sleepiness Scale (DSS), the sleep onset latency, the time awake after sleep onset and the numbers of awakenings were gathered 2 weeks before the intervention (T0), immediately prior the intervention (T1), 2 weeks after the last session of the intervention (T2) and a 3-month follow-up (T3). The total number of administrations of PRN therapy from T0 to T1 and from T1 to T2 were also examined. A significant reduction was shown on the NSOS, the sleep onset latency and in the time awake after sleep onset from T1 to T2 and from T1 to T3, while no significant difference was found between T0 and T1. A significant decrease on the mean number of administrations of PRN therapy was also found between 15 days before the intervention (T0-T1) and 15 days after intervention (T1-T2). The initial results of this study seems to suggest the possible efficacy of a short-term psychoeducational intervention on improving persistent non-organic insomnia in severely mentally ill patients. Further control studies are necessary to confirm these findings.  相似文献   
14.
Results of a recent study have demonstrated that exposure to multiple ethanol concentrations and repeated ethanol deprivation periods in Indiana ethanol-preferring (P) rats resulted in the development of an alcohol deprivation effect (ADE; the temporary increase in voluntary ethanol intake after a period of deprivation from ethanol) characterized by consumption of intoxicating amounts of ethanol. The current study was designed to possibly extend these results to Sardinian alcohol-preferring (sP) rats, generated with the same selective program previously used for P rats. To this aim, ethanol-naive sP rats were exposed initially to the home cage four-bottle choice [10%, 20%, and 30% (vol./vol.) ethanol solutions and water] for eight consecutive weeks. Subsequently, rats were divided into two groups: The first group had continuous access to the four-bottle regimen (nondeprived rats), and the second group was exposed to five cycles of 14-day periods of deprivation from ethanol and 14-day periods of reexposure to the four-bottle regimen. An ADE developed after each deprivation period. However, the extra intake of ethanol was limited to the first hour of each reaccess period. Magnitude of ADE did not change with repeated periods of deprivation. However, a shift in preference toward the two highest concentrations of ethanol solutions was evident from the first reexposure to ethanol and was maintained throughout the study. These results provide further evidence on the heterogeneity of ethanol-drinking behavior among rat lines selectively bred for high ethanol preference and consumption.  相似文献   
15.
Bone scintigraphy plays a major role in the diagnosis of bone metastases. The clinical utility of new biochemical markers of bone metabolism has recently been investigated in various bone diseases. This study evaluated the role of some bone metabolism markers in comparison with bone scan in the follow-up of breast cancer patients. We studied 149 patients with breast cancer, 33 (22%) of whom had bone metastases. IRMAs were used for the evaluation of blood levels of osteocalcin, bone alkaline phosphatase (BAP), the C-terminal propeptide of type I procollagen and the C-terminal cross-linked telopeptide of type I collagen (ICTP). Multivariate regression analysis showed that menopausal status (P=0.007) and metastatic bone lesions (P=0.001) affected bone marker levels. When considering post-menopausal women, the only subset in which bone metabolism marker behaviour could be reliably investigated, we found a high degree of overlap in marker distribution for scan-positive and scan-negative patients. Discrimination between scan-negative and scan-positive patients based on the above markers, taken singly or jointly, was assessed by means of logistic discriminant analysis. The best discrimination was achieved with BAP, closely followed by ICTP. BAP and ICTP together gave a slight improvement over the use of the two markers separately. However, even in this case the degree of discrimination was poor and its clinical utility was limited. In fact, to achieve a specificity of 95%, the sensitivity of the test was about 20%; conversely, with a sensitivity of 95%, the specificity was below 10%. In conclusion, based on our findings, we believe that blood levels of the investigated markers cannot replace bone scintigraphy in the follow-up of breast cancer patients for the early detection of bone metastases. Received 14 April and in revised form 5 July 1997  相似文献   
16.
Empty Sella and Headache   总被引:2,自引:0,他引:2  
SYNOPSIS
Empty sella is an anatomical condition caused by herniation of the subarachnoid space into the pituitary fossa through an incompetent seller diaphragm. Headache seems to be one of the most frequently reported symptoms. We studied 13 headache patients (12 females, 1 male) presenting with primary empty sella (PES) on CT scan. The characteristics of the headache were analyzed and plasma levels of pituitary hormones or cortisol assessed. We confirmed the nonspecific nature of the headache in PES even though the majority of our patients complained of daily headache, mostly localized anteriorly. Hormone plasma levels were within normal range in all the patients assessed. However, four patients reported earlier endocrine disorders and more than half of the patients presented with obesity.
In our opinion, PES should be suspected in middle-aged overweight women with daily headache even in the absence of endocrine symptomatology.  相似文献   
17.
This article is a retrospective study comparing the efficacy of Regnauld arthroplasty to first ray osteotomies for the treatment of hallux valgus. One hundred consecutive cases of Regnauld arthroplasties were compared with 100 consecutive first ray osteotomies. One hundred fourty-one patients were available for follow-up, and based on clinical/radiographic examinations, 72 were treated with the osteotomy protocol (group A) and 69 with Regnauld arthroplasty (group B). Age at surgery, clinical symptoms, and preoperative radiologic findings were similar for the 2 groups; there was a preponderance of female patients (90%). The average follow-up was 49 months in group A and 51 months in group B. Clinical evaluation showed in the osteotomy group a more stable correction (79% v 49%), greater pain reduction (measured in a visual analog scale from 0 = pain free to 10 = deep intolerable pain), increased residual articular excursion of the first metatarsophalangeal joint (27 degrees of active dorsiflexion from neutral position v 8 degrees ), and less presence of central metatarsalgia (15% v 34%) (P <.05). The radiographic evaluation expressed more stable correction values in group A for the following parameters: joint preservation, sesamoid position, intermetatarsal angle (7 degrees v 12 degrees ), abduction angle of the hallux (14 degrees v 20 degrees ), and proximal articular set angle (8 degrees v 18 degrees ) (P <.05).  相似文献   
18.
The clinical and biochemical presentation of carcinoma of the pancreas (PC) and of the papilla of Vater (CPV) are very similar, and, consequently, detailed investigations are required to correctly distinguish between them. The aim of the present study was to select the clinical and biochemical variables that would most efficiently discriminate the precise site of tumor origin. The study group consisted of 72 patients with PC and 22 patients with CPV consecutively hospitalized in our department. The following clinical parameters were considered: age, asthenia, anorexia, vomiting, weight loss, pain, fever, pruritis, and constipation; the biochemical parameters considered were total, direct, and indirect bilirubin, glucose, alkaline phosphatase, gamma glutamy transferase, transaminase, total protein, amylase, and occult blood in stools. The results indicated that in the initial phase of PC the most frequent clinical parameters were weight loss (P<0.0001), anorexia (P<0.02), constipation (P<0.001), and pruritus (P<0.01). In contrast, in CPV, fever (P<0.003) was most frequent in the same phase. There was a statistically significant difference in occult blood in stools (P<0.0001), total (P<0.03) and direct bilirubin (P<0.02), alkaline phosphatase (P<0.05), and transaminase (P<0.002) values in the two groups. On discriminant analysis, weight loss, constipation, pruritus, nausea, anorexia, and fever were the variables which best discriminated between the two types of tumors. In fact, the presence of weight loss, anorexia, asthenia, constipation, and pruritus correctly classified 87.5% of the patients with PC, while the presence of fever and nausea correctly classified 72.7% of the patients with CPV.  相似文献   
19.
20.
The results of the first 3 year' collaboration of the Italian Registry of Paediatric Chronic Peritoneal Dialysis (CPD) (1986–1988) are presented. This Registry acquired data on the majority of the paediatric patients treated with CPD in Italy, thus providing a national picture in a field where few nationwide surveys are available. Patients of less than 15 years of age at the start of dialysis were enrolled and clinical data collected until the age of 19 years. The number of nephrological paediatric centres participating in the Registry increased from 7 in 1986 to 11 in 1988. The total number of patients on CPD was 70 and the percentage of dialysed children treated with CPD ranged from 40.2% to 43.6%. Data on 89 peritoneal catheters were collected: during 1417 dialysis-months 70 catheter-related complications were observed (1:20.8 dialysis-months); actuarial catheter survival was 92.7% at 6 months, 84.8% at 1 year and 68.8% at 2 years. The incidence of peritonitis changed from 1 episode every 10.9 patient-months in 1986 to 1 every 19.8 in 1988. Abdominal hernias were the other main clinical complication observed. The survival of patients was 92.5% at 3 years, while the technique survival at the same time was 84%.  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