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   2761篇
  免费   191篇
  国内免费   25篇
耳鼻咽喉   63篇
儿科学   86篇
妇产科学   37篇
基础医学   393篇
口腔科学   218篇
临床医学   217篇
内科学   520篇
皮肤病学   69篇
神经病学   155篇
特种医学   187篇
外科学   344篇
综合类   46篇
一般理论   2篇
预防医学   288篇
眼科学   34篇
药学   178篇
中国医学   22篇
肿瘤学   118篇
  2023年   24篇
  2022年   45篇
  2021年   98篇
  2020年   71篇
  2019年   77篇
  2018年   106篇
  2017年   93篇
  2016年   91篇
  2015年   106篇
  2014年   147篇
  2013年   165篇
  2012年   215篇
  2011年   196篇
  2010年   157篇
  2009年   102篇
  2008年   121篇
  2007年   134篇
  2006年   124篇
  2005年   90篇
  2004年   84篇
  2003年   69篇
  2002年   49篇
  2001年   32篇
  2000年   28篇
  1999年   30篇
  1998年   52篇
  1997年   42篇
  1996年   39篇
  1995年   27篇
  1994年   34篇
  1993年   28篇
  1992年   18篇
  1991年   17篇
  1990年   17篇
  1989年   26篇
  1988年   22篇
  1987年   25篇
  1986年   12篇
  1985年   10篇
  1984年   7篇
  1983年   16篇
  1982年   22篇
  1981年   15篇
  1980年   18篇
  1979年   8篇
  1978年   7篇
  1977年   14篇
  1976年   10篇
  1975年   7篇
  1969年   5篇
排序方式: 共有2977条查询结果,搜索用时 812 毫秒
991.
992.
ObjectiveTo describe the clinical, laboratory, and radiological characteristics, as well as the outcomes of children with MIS-C.MethodMulticenter, prospective cohort study, conducted in 17 pediatric intensive care units in five states in Brazil, from March to July 2020. Patients from 1 month to 19 years who met the MIS-C diagnostic criteria were included consecutively.ResultsFifty-six patients were included, with the following conditions: Kawasaki-like disease (n = 26), incomplete Kawasaki disease (n = 16), acute cardiac dysfunction (n = 10), toxic shock syndrome (n = 3), and macrophage activation syndrome (n = 1). Median age was 6.2 years (IQR 2.4?10.3), 70% were boys, 59% were non-whites, 20% had comorbidities, 48% reported a contact with COVID-19 cases, and 55% had a recent SARS-CoV-2 infection confirmed by RT-PCR and/or serology. Gastrointestinal symptoms were present in 71%, shock symptoms in 59%, and severe respiratory symptoms in less than 20%. d-Dimer was increased in 80% and cardiac dysfunction markers in more than 75%. Treatment included immunoglobulin (89%); corticosteroids, antibiotics, and enoxaparin in about 50%; and oseltamivir and antifungal therapy in less than 10%. Only 11% needed invasive mechanical ventilation, with a median duration of five days (IQR 5–6.5). The median length of PICU stay was six days (IQR 5–11), and one death occurred (1.8%).ConclusionsMost characteristics of the present MIS-C patients were similar to that of other cohorts. The present results may contribute to a broader understanding of SARS-CoV-2 infection in children and its short-term consequences. Long-term multidisciplinary follow-up is needed, since it is not known whether these patients will have chronic cardiac impairment or other sequelae.  相似文献   
993.
994.
Cancer is the leading cause of death among Hispanics/Latinos, who represent the largest racial/ethnic minority group in the United States, accounting for 17.4% (55.4 million/318 million) of the total US population in 2014. Every 3 years, the American Cancer Society reports on cancer statistics for Hispanics based on incidence data from the National Cancer Institute, the Centers for Disease Control and Prevention, and the North American Association of Central Cancer Registries and mortality data from the National Center for Health Statistics. Among Hispanics in 2015, there will be an estimated 125,900 new cancer cases diagnosed and 37,800 cancer deaths. For all cancers combined, Hispanics have 20% lower incidence rates and 30% lower death rates compared with non‐Hispanic whites (NHWs); however, death rates are slightly higher among Hispanics during adolescence (aged 15‐19 years). Hispanic cancer rates vary by country of origin and are generally lowest in Mexicans, with the exception of infection‐associated cancers. Liver cancer incidence rates in Hispanic men, which are twice those in NHW men, doubled from 1992 to 2012; however, rates in men aged younger than 50 years declined by 43% since 2003, perhaps a bellwether of future trends for this highly fatal cancer. Variations in cancer risk between Hispanics and NHWs, as well as between subpopulations, are driven by differences in exposure to cancer‐causing infectious agents, rates of screening, and lifestyle patterns. Strategies for reducing cancer risk in Hispanic populations include increasing the uptake of preventive services (eg, screening and vaccination) and targeted interventions to reduce obesity, tobacco use, and alcohol consumption. CA Cancer J Clin 2015;65:457–480 . © 2015 American Cancer Society.  相似文献   
995.
996.

Background

Pancreas transplantation is a treatment for advanced type 1 diabetes and offers significant improvement in quality of life. Recent advances in surgical techniques and immunosuppression regimes lead to good outcomes. However, despite significant higher rates of multiorgan donors in Brazil, pancreas transplantation seems to have remained stable. This study aimed to investigate the acceptance rate of potential pancreas donors in the past 10 years in São Paulo State.

Methods

We retrospectively evaluated potential pancreas donors characteristics and its acceptance rate in São Paulo State in the past 10 years. We divided this period into 2 eras: 1st era from January 2003 to January 2008; and 2nd era from January 2008 to January 2013. Data were obtained from São Paulo's government official website.

Results

During the whole period, 5,005 deceased donors of all ages were available for pancreas transplantation. According to eras, we had 1,588 donors in the 1st and 3,417 in the 2nd era. In the 2nd era, donors >49 years old were significantly more common (P < .001). Blood test abnormalities, donor comorbidities, and high dosage of vasopressors also were significantly higher in the 2nd era. Rate of graft acceptance had a significant decrease in the 2nd era, from 46.4% to 25% (P < .05).

Conclusions

Despite greater organ availability, pancreas transplantations performed in São Paulo State remained stable. Rate of graft acceptance is dramatically lower in more recent years.  相似文献   
997.
The aim of the present study was to evaluate the feasibility of applying Raman spectroscopy in probing the molecular changes in terms of collagen deposition and tissue remodeling associated with two well-established experimental models of osteoarthritis (OA) in knee of rats. In order to evaluate alterations in the articular surface area, the menisci-covered tibial region was assessed into three groups as follows: control (joint preserved) and two models of experimental knee OA: collagenase-induced model (n?=?8) and treadmill exercise-induced model (n?=?8). Each group was examined for molecular changes using spectral parameters related to cartilage, subchondral bone, and bone tissues. A significant increase of Raman ratios related to mineralization and tissue remodeling was found (p?<?0.05), suggesting that both models were successful for inducing OA in rats. The significantly lower phenylalanine content and higher crystallinity in the treadmill exercise-induced model of OA than collagenase-induced model of OA (p?<?0.05) indicated that the OA pathogenesis was model-dependent. Thus, this work suggests that the Raman spectroscopy technique has potential for the diagnosis and detection of cartilage damage and monitoring of subchondral bone and bone in OA pathogenesis at the molecular level.  相似文献   
998.
Osteoporosis is a disease characterized by the reduction of bone mineral density. LED wavelengths seem to have similar photo-stimulating effects to laser light. The aim of this study was to assess the Raman shifts: ~960 (phosphate hydroxyapatite), ~1,070 (carbonate hydroxyapatite), and ~1,454 cm ?1 (lipids and proteins) on bone defects of ovariectomized rats treated or not with LED phototherapy (LED-PT). Thirty female rats were divided into four groups (Basal, OVX, OVX+Clot, and OVX+Clot+LED), then subdivided into two subgroups (15 and 30 days after surgery). Osteoporosis induction by ovariectomy (OVX) was performed in all groups, except for the normal basal group. Following development of osteoporosis, one surgical bone defect (5 mm2) was created on the femur of each animal. Defects were irradiated with LED light (λ?=?850?±?10 nm, P?=?150 mW, CW, Ф?=?0.5 cm2, 20.4 J/cm2 per session, t?=?128 s, 163.2 J/cm2 per treatment) at 48 h interval during 2 weeks. Raman measurements were taken at the surface of the defects 30 days after surgery. Significant difference between groups Basal, OVX+Clot, and OVX+Clot+LED for the peaks at ~960 (p?≤?0.001; 15 and 30 days), ~1,070 (p?≤?0.001; 15 and 30 days), and ~1,450 cm?1 (p?=?0.002; 15 days; p?=?0.004; 30 days) were detected. In addition, statistical differences were obtained between groups OVX, OVX+Clot, and OVX+Clot+LED for these same peaks at all time points (p?≤?0.001). At 15 and 30 days, there were statistical differences between groups OVX+Clot and OVX+Clot+LED for the peaks at ~960 (p?≤?0.001), ~1,070 (p?≤?0.001; p?=?0.003), and ~1,450 cm?1 (p?≤?0.001; p?=?0.002). The results of this study are indicative that infrared LED-PT improved the deposition of HA on bone defects of ovariectomized rats.  相似文献   
999.

Background

Despite advances in diagnosis and surgical strategies, up to 70 % of patients will develop recurrence of the disease after resection of colorectal cancer liver metastases (CRCLM). The purpose of our study was to determine the frequency of four different mechanisms of intrahepatic dissemination, and to evaluate the impact of each mechanism on patient outcomes.

Methods

The medical records of 118 patients who underwent a first resection of CRCLM during the period between 2000 and 2010 were reviewed. Clinicopathologic variables and outcome parameters were examined. Resected specimens were submitted to routine histological evaluation, and immunohistochemical staining with D2-40 (lymphatic vessels), CD34 (blood vessels), CK-7 (biliary epithelium), and CK-20 (CRC cells).

Results

The mean follow-up after resection was 38 months. Tumor recurrence was observed in 76 patients, with a median interval of 13 months after resection. Overall survival and disease-free survival (DFS) rates after hepatectomy were 62 and 56 %, and 26 and 24 % at 3 and 5 years, respectively. Intrahepatic microscopic invasion included portal venous in 49 patients, sinusoidal in 43 patients, biliary in 20 patients, and lymphatic in 33 patients. Intra-hepatic lymphatic invasion was the only mechanism of dissemination independently associated with the risk of hepatic recurrence (odds ratio 2.75) and shorter DFS (p = 0.006).

Conclusion

Intrahepatic lymphatic invasion is a significant prognostic factor. Other mechanisms of invasion, although frequently observed, are not related to recurrence or survival, suggesting that the lymphatic system is the main route for dissemination of CRCLM. Furthermore, immunohistochemical detection of intrahepatic lymphatic invasion might be of value in clinical practice.  相似文献   
1000.

Objective

To estimate the prevalence of lifetime use of crack cocaine and to assess associations with violent and sexual behaviors in young adults selected from the general population of Pelotas, Southern Brazil.

Methods

This cross-sectional population-based study included 1,560 participants aged 18–24 years. The use of alcohol and other substances, including crack cocaine, was assessed using the alcohol, smoking and substance involvement screening test. Other variables included violent behaviors, firearm possession, and sexual risk behaviors. The frequency of antisocial personality disorder was also investigated. Associations were analyzed using a crude model and models adjusted for sex, social class, and the use of snorted cocaine.

Results

Lifetime prevalence of crack cocaine use was 2.51 %, and it was higher among males and individuals coming from more vulnerable social classes (D or E). In the final multivariate models, lifetime use of crack cocaine was associated with episodes of aggression and firearm possession, as well as with a higher chance of not having used condom in the last sexual intercourse. In less conservative models, crack cocaine use was associated with other violent and sexual risk behaviors.

Discussion

The strong association observed between lifetime use of crack cocaine and different violent and sexual risk behaviors underscores relevant characteristics of people who use crack cocaine. Improving our understanding of possible causal chains leading to such associations should be a priority in future studies.  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