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   6376篇
  免费   380篇
  国内免费   21篇
耳鼻咽喉   60篇
儿科学   222篇
妇产科学   61篇
基础医学   1116篇
口腔科学   280篇
临床医学   535篇
内科学   948篇
皮肤病学   238篇
神经病学   729篇
特种医学   266篇
外科学   796篇
综合类   35篇
一般理论   2篇
预防医学   247篇
眼科学   288篇
药学   465篇
中国医学   9篇
肿瘤学   480篇
  2023年   16篇
  2022年   49篇
  2021年   89篇
  2020年   83篇
  2019年   67篇
  2018年   105篇
  2017年   96篇
  2016年   131篇
  2015年   175篇
  2014年   188篇
  2013年   239篇
  2012年   367篇
  2011年   367篇
  2010年   253篇
  2009年   255篇
  2008年   463篇
  2007年   395篇
  2006年   413篇
  2005年   410篇
  2004年   459篇
  2003年   412篇
  2002年   378篇
  2001年   108篇
  2000年   89篇
  1999年   99篇
  1998年   97篇
  1997年   92篇
  1996年   71篇
  1995年   51篇
  1994年   42篇
  1993年   43篇
  1992年   35篇
  1991年   31篇
  1990年   32篇
  1989年   54篇
  1988年   33篇
  1987年   28篇
  1986年   23篇
  1985年   25篇
  1984年   17篇
  1983年   14篇
  1982年   23篇
  1981年   15篇
  1980年   17篇
  1979年   15篇
  1978年   15篇
  1977年   18篇
  1974年   13篇
  1973年   16篇
  1972年   18篇
排序方式: 共有6777条查询结果,搜索用时 15 毫秒
991.
BACKGROUND: This study aims to assess the psychiatric morbidity of persons at risk of homelessness and to analyze correlations and risk factors between homelessness and mental disorders. METHODS: The sample included 101 citizens of Mannheim, Germany, who were immediately threatened by eviction. Mental disorders were diagnosed using a standardized test, and other factors were also assessed. Data from August 2000 to June 2002 were collected. RESULTS: Acute mental disorders requiring treatment were determined in 79.3% of the study sample. Addiction disorders (alcoholism) played a major role. Personality, anxiety, and affective disorders were even more frequent than in a control group of homeless people in the same region, whereas schizophrenia and other mental disorders were similarly prevalent. Regression analyses confirmed unemployment, alcoholism, and male gender as the most important risk factors for homelessness among people threatened by eviction. CONCLUSIONS: The results suggest that prevention strategies should be multidimensional and interdisciplinary.  相似文献   
992.
993.
In rare cases, the diagnosis of hypertrophic and dilated cardiomyopathy (DCM) in children was established postmortem. Our case report deals with the sudden and unexpected death of an 8-year-old boy. The postmortem examination revealed non-obstructive hypertrophy with irregular arrangement of muscular fibers, dilatation of the ventricles, endocardial fibrosis, microfocal vacuolization with enlarged hyperchromatic nuclei, and signs of inflammation with interstitial fibrosis. We present an evolution from idiopathic cardiomyopathy to DCM. To some extent, there were morphologic signs of an inflammatory process that first led us to suspect a specific inflammatory DCM.  相似文献   
994.
Oral Langerhans cell histiocytosis.   总被引:1,自引:0,他引:1  
AIM: Our aim is to compare the different methods of treatment available for Langerhans cell histiocytosis (LCH) in the oral and maxillo-facial region. A classification based on clinical and immunohistochemical data is proposed and a grading for the severity of the disease is proposed. PATIENTS AND METHODS: Records and clinical data of 12 patients were evaluated retrospectively. The patients' ages ranged from 20 months to 47 years. Nine had manifestations in the maxillo-facial region, of which six had a single oral lesion only, with the three remaining patients having multiple lesions in this region. Three patients had lesions in the upper thorax in addition to their oral lesions. Eleven patients were treated surgically with one having been treated previously with steroid-therapy. One patient had already been treated with chemotherapy. The longest follow-up was 16 years. Immunohistochemical stains for antigen-CD-1a, antigen-S-100 and antigen-Ki-67 were performed. A proposal for staging the lesions in the oro-maxillo-facial region was made. The intensity of the antigen-Ki-67 stains was evaluated. RESULTS: Eleven patients exhibited no signs of recurrence whilst only one patient had a recurrence implying that surgical treatment was very effective in eradication and cure of the disorder. It is felt that the number of antigen-Ki-67 positive cells is related to the activity of the disease. CONCLUSION: Langerhans cell histiocytosis should be treated surgically. Only in very severe cases should surgical treatment be complemented with either radio-therapy or chemotherapy. Especially in disseminated cases, chemotherapy would appear to improve the outcome. The antigen Ki-67 as proliferation marker is suggested as a grading parameter of this disease.  相似文献   
995.
Purpose: Descemet‐stripping automated endothelial keratoplasty (DSAEK) is an advanced method of lamellar endothelial keratoplasty. In comparison with penetrating keratoplasty, visual rehabilitation seems to be faster. Final visual outcome of DSAEK, however, seems to be limited, especially in comparison with Descemet membrane endothelial keratoplasty (DMEK). DSAEK cases without graft failure often do not show any definite correlate for the reduced optical performance. In this study, we tried to correlate visual acuity following DSAEK with interface reflectivity as measured by a rotating Scheimpflug system. Methods: We examined 14 eyes of 13 patients with the pentacam for 2–11 months following DSAEK. Reflectivity of the interface region in the centre of the optical axis as well as central corneal thickness was determined. Statistical correlation between interface reflectivity and best spectacle‐corrected visual acuity, central corneal thickness and follow‐up time was drawn (multifactorial linear regression analysis). Results: Statistically significant correlation between interface reflectivity and BSCVA as well as follow‐up time was found. Reflectivity was highest in regions of interface (metal) particles. There was no statistically significant correlation between interface reflectivity and central corneal thickness. Conclusion: We present a measurable correlate for reduced visual outcome following DSAEK despite a clear graft. Inverse correlation between interface reflectivity and best spectacle‐corrected visual acuity (BSCVA) indicates that irregularities or scarring in the interface region may influence the optical quality following DSAEK.  相似文献   
996.

Background

Since it has been observed that melanocytic lesions can alter their appearance during pregnancy, we analyzed whether hormone receptors are expressed in conjunctival nevi as well as conjunctival melanoma. We further analyzed whether the number of estrogen (ER) or progesterone receptors (PR) might be associated with the disease course in conjunctival melanoma.

Methods

Twenty-seven paraffin-embedded samples of conjunctival nevi and 27 conjunctival melanoma specimens were examined using immunohistological analysis with antibodies against PR and ER. The percentage of stained cells were analyzed, taking into account patient gender and age. Out of the melanoma group, all patients with complete data for tumor thickness, tumor localization, age at diagnosis, gender, and follow-up including recurrence, metastasis and tumor-related death were included in the second part of the study (n?=?15), where hormone receptor rates were associated with tumor outcome, regarding recurrences, metastasis or death. Written consent was received from all included patients.

Results

Both nevi and melanomas showed high rates of PR- and ER-positive cells. In Nevi, 64?±?25 % of cells stained positive for PR and 35?±?34 % for ER. In melanoma specimens, 68?±?30 % showed PR and 44?±?34 % ER expression. Differences between men and women in expression rates were not statistically significant. Out of 15 melanoma patients (nine female, six male), 53 % (five women and three men) experienced 1—4 recurrences, and four patients developed metastases. The median estimated survival time was 12.2 years. A multivariate survival model taking into account known risk factors for prognosis in conjunctival melanoma confirmed tumor location to be an important predictive factor for outcome (p?=?0.05). The rate of PR or ER did not show a statistically significant correlation with the disease course in our cohort.

Conclusions

We observed that conjunctival melanocytic lesions express hormone receptors, which could explain why these tumors can alter their appearance under hormonal changes. Regarding the prognosis of conjunctival melanoma, no statistically significant correlation between hormone receptor expression and event-free survival was found in this analysis.  相似文献   
997.

Ethnopharmacological relevance

This analysis of documented medicinal plants of the Swiss Flora over the last two millennia provides a rich source of knowledge on earlier uses of plants and use patterns of the local flora. We ask which local plant species were used during different time periods of the last 2000 years and how the numbers of species and the use intensity of specific plant families, growth forms and habitats changed over time.

Materials and methods

Totally 25 herbals from the antiquity, monastic medicine, Renaissance, early modern era and the contemporary time as well as five recent ethnobotanical studies were considered. Use patterns were analysed with the Bayesian approach.

Results

A total of 768 species, i.e. 32% of the vascular plants of the Swiss Flora have been documented as medicinal plants. Numbers increase until the monastic period (366 spp.) and the Renaissance (476) and remain relatively stable since then (modern and contemporary era: 477). But, 465 formerly documented species do not occur in the ethnobotanical studies and thus seem not to be used any more. Overall, 104 species are documented through all time periods. Archeophytes, trees and forest plants are generally overrepresented in herbals from all time periods while plants from above the timberline are generally underrepresented. Most widely used are the Lamiaceae and Apiaceae.

Conclusion

A constant body of medicinal plant knowledge in Switzerland exists since ancient time. This knowledge was always influenced by knowledge from neighboring countries and no “typical Swiss specialties” seem to exist. Medicinal plants are not randomly chosen from the available flora. Certain species are deliberately introduced others are neglected. This process, which is still ongoing, can be traced back with the help of herbals to the antiquity.  相似文献   
998.
999.

Purpose

Increased arterial ammonia levels are associated with high mortality in patients with acute liver failure (ALF). Data on the prognostic impact of arterial ammonia is lacking in hypoxic hepatitis (HH) and scarce in critically ill patients with cirrhosis.

Methods

The patient cohort comprised 72 patients with HH, 43 patients with ALF, 100 patients with liver cirrhosis and 45 patients without evidence for liver disease. Arterial ammonia concentrations were assessed on a daily basis in all patients and the results were compared among these four patient groups and between 28-day survivors and 28-day non-survivors overall and in each group.

Results

Overall 28-day mortality rates in patients with HH, ALF and cirrhosis and in the control group were 54, 30, 49 and 27 %, respectively. Peak arterial ammonia levels differed significantly between transplant-free 28-day survivors and non-survivors in the HH and ALF groups (p < 0.01 for both). Multivariate regression identified peak arterial ammonia concentrations as an independent predictor of 28-day mortality or liver transplantation in patients with HH and ALF, respectively (p < 0.01). There was no association between mortality and arterial ammonia in patients with liver cirrhosis and in the control group. Admission arterial ammonia levels were independently linked to hepatic encephalopathy grades 3/4 in patients with HH (p < 0.01), ALF (p < 0.05) and cirrhosis (p < 0.05), respectively.

Conclusions

Elevated arterial ammonia levels indicate a poor prognosis in acute liver injury and are associated with advanced HE in HH, ALF and cirrhosis. Arterial ammonia levels provide additional information in the risk assessment of critically ill patients with liver disease.  相似文献   
1000.
Septic shock is characterized by increased vascular permeability and hypotension despite increased cardiac output. Numerous vasoactive cytokines are upregulated during sepsis, including angiopoietin 2 (ANG2), which increases vascular permeability. Here we report that mice engineered to inducibly overexpress ANG2 in the endothelium developed sepsis-like hemodynamic alterations, including systemic hypotension, increased cardiac output, and dilatory cardiomyopathy. Conversely, mice with cardiomyocyte-restricted ANG2 overexpression failed to develop hemodynamic alterations. Interestingly, the hemodynamic alterations associated with endothelial-specific overexpression of ANG2 and the loss of capillary-associated pericytes were reversed by intravenous injections of adeno-associated viruses (AAVs) transducing cDNA for angiopoietin 1, a TIE2 ligand that antagonizes ANG2, or AAVs encoding PDGFB, a chemoattractant for pericytes. To confirm the role of ANG2 in sepsis, we i.p. injected LPS into C57BL/6J mice, which rapidly developed hypotension, acute pericyte loss, and increased vascular permeability. Importantly, ANG2 antibody treatment attenuated LPS-induced hemodynamic alterations and reduced the mortality rate at 36 hours from 95% to 61%. These data indicate that ANG2-mediated microvascular disintegration contributes to septic shock and that inhibition of the ANG2/TIE2 interaction during sepsis is a potential therapeutic target.  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