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   3039篇
  免费   217篇
  国内免费   15篇
耳鼻咽喉   27篇
儿科学   68篇
妇产科学   71篇
基础医学   369篇
口腔科学   82篇
临床医学   253篇
内科学   668篇
皮肤病学   86篇
神经病学   171篇
特种医学   57篇
外科学   509篇
综合类   74篇
一般理论   1篇
预防医学   265篇
眼科学   65篇
药学   329篇
中国医学   12篇
肿瘤学   164篇
  2023年   43篇
  2022年   86篇
  2021年   168篇
  2020年   95篇
  2019年   127篇
  2018年   150篇
  2017年   102篇
  2016年   102篇
  2015年   92篇
  2014年   153篇
  2013年   150篇
  2012年   193篇
  2011年   231篇
  2010年   169篇
  2009年   108篇
  2008年   128篇
  2007年   149篇
  2006年   125篇
  2005年   135篇
  2004年   108篇
  2003年   113篇
  2002年   77篇
  2001年   48篇
  2000年   28篇
  1999年   25篇
  1998年   11篇
  1997年   19篇
  1996年   7篇
  1994年   9篇
  1993年   13篇
  1992年   25篇
  1991年   27篇
  1990年   14篇
  1989年   17篇
  1988年   17篇
  1987年   7篇
  1986年   19篇
  1985年   13篇
  1984年   9篇
  1983年   10篇
  1981年   7篇
  1979年   11篇
  1978年   7篇
  1977年   12篇
  1976年   9篇
  1974年   8篇
  1973年   16篇
  1972年   18篇
  1971年   11篇
  1967年   6篇
排序方式: 共有3271条查询结果,搜索用时 15 毫秒
71.
Sarcoidosis is thought to result from the interaction between an unknown environmental antigenic trigger and the host's genetic susceptibility. We hypothesized that sarcoidosis, or one of the disease subsets, could be associated with single nucleotide polymorphisms of C-C chemokine receptor 2 (CCR2) gene. Eight single-nucleotide polymorphisms in CCR2 were studied in a total of 304 Dutch individuals (90 non-L?fgren sarcoidosis, 47 L?fgren's syndrome, 167 control subjects). From the investigated CCR2 polymorphisms, nine haplotypes were deduced (haplotypes 1-9). In patients with L?fgren's syndrome, a strongly significant increase in the frequency of CCR2-haplotype 2, which includes four unique alleles (A at nucleotide position -6752, A at 3,000, T at 3,547, and T at 4,385), was observed compared with control subjects (74% vs. 38% respectively, p < 0.0001), whereas no difference was found between non-L?fgren sarcoidosis and control subjects (both 38%). The association between CCR2-haplotype 2 carriage frequency and L?fgren's syndrome (odds ratio, 4.4; p < 0.0001) remained significant after adjustment for human leukocyte antigen haplotype DRB1*0301-DQB1*0201 (odds ratio, 11.5; p < 0.0001) and female sex (odds ratio, 3.2; p = 0.003), two known risk factors for L?fgren's syndrome. In conclusion, this report describes a strong association between CCR2-haplotype 2 and L?fgren's syndrome. Further studies are needed to understand the molecular mechanisms underlying this association.  相似文献   
72.
73.

Background

The placement of a central venous catheter for the administration of vasopressors is still recommended and required by many institutions because of concern about complications associated with peripheral administration of vasopressors.

Objective

Our aim was to determine the incidence of complications from the administration of vasopressors through peripheral venous catheters (PVC) in patients with circulatory shock, and to identify the factors associated with these complications.

Methods

This was a prospective, observational study conducted in the emergency department (ED) of a tertiary care medical center. Patients presenting to the ED with circulatory shock and in whom a vasopressor was started through a PVC were included. Research fellows examined the i.v. access site for complications twice daily during the period of peripheral vasopressor administration, then daily up to 48 h after treatment discontinuation or until the patient expired.

Results

Of the 55 patients that were recruited, 3 (5.45% overall, 6% of patients receiving norepinephrine) developed complications; none were major. Two developed local extravasation and one developed local thrombophlebitis. All three complications occurred during the vasopressor infusion, none in the 48 h after discontinuation, and none required any medical or surgical intervention. Two of the three complications occurred in the hand, and all occurred in patients receiving norepinephrine and with 20-gauge catheters.

Conclusions

The incidence of complications from the administration of vasopressors through a PVC is small and did not result in significant morbidity in this study. Larger prospective studies are needed to better determine the factors that are associated with these complications, and identify patients in whom this practice is safe.  相似文献   
74.
In this study, we present a successful simple method for printing and finishing of polyester and cotton fabrics using gold and silver nanoparticles (Au-NPs and Ag-NPs, respectively) as stable, fast colorants and functional components. The surface plasmon resonance (SPR) bands of the colloidal gold and silver NPs were observed at λmax 520 nm and 450 nm, respectively, indicating the presence of spherical Au-NPs and Ag-NPs, which was further confirmed by TEM analysis. The printed samples were subjected to SEM, XRD and EDX analyses. The SEM images and EDX spectra unequivocally confirmed the existence of embedded NPs on the fabric surfaces. Both the cotton and polyester samples possessed excellent color fastness, as indicated from the color fastness test. The functional properties of the printed fabrics indicated that the incorporation of Au-NPs and Ag-NPs into the fabrics simultaneously imparted multifunctional properties such as stable brilliant colors, highly durable antimicrobial activity and very good UV-protection properties.

In this study, we present a successful simple method for printing and finishing of polyester and cotton fabrics using gold and silver nanoparticles (Au-NPs and Ag-NPs, respectively) as stable, fast colorants and functional components.  相似文献   
75.
Copper oxide (CuO) nanoparticles have received considerable interest as active and inexpensive catalysts for various gas–solid reactions. The CuO reducibility and surface reactivity are of crucial importance for the high catalytic activity. Herein, we demonstrate that the reducibility and stability of CuO nanoparticles can be controlled and tailored for the high catalytic activity of CO oxidation. The synthesized CuO nanoparticles possessed enhanced reducibility in CO atmosphere at lower reduction temperature of 126 °C compared to 284 °C for that of reference CuO particles. Moreover, the CuO catalysts with tailored reducibility demonstrated a reaction rate of 35 μmol s−1 g−1 and an apparent activation energy of 75 kJ mol−1. Furthermore, the tailored catalysts exhibited excellent long-term stability for CO oxidation for up to 48 h on stream. These readily-reducible CuO nanoparticles could serve as efficient, inexpensive and durable catalysts for CO oxidation at low temperatures.

Copper oxide (CuO) nanoparticles of tailored reducibility could be used as inexpensive, efficient and durable catalysts for CO oxidation at low temperature.  相似文献   
76.
PURPOSE: The aim of this study was to determine the epidemiological and the clinical characteristics of post-transplant lymphoproliferative disease (PTLD) and to evaluate its impact on patients' and grafts' survival. PATIENTS AND METHODS: Three hundred and sixteen adult kidney recipients, transplanted between June 1986 and May 2006, were included. The incidence rates were calculated by dividing the number of different events (PTLD, death and graft-loss) by the total duration of follow-up. The survival rates and the cumulated frequency of PTLD were calculated according to the actuarial method. RESULTS: Seven recipients developed PTLD during a cumulated follow-up of 2202 years. The annual incidence was of 0.32% (95% CI : 0.30-0.34). It was of 0.81% (0.70-0.92) in recipients of kidneys from deceased donors, and of 0.25% (0.23-0.27) in patients transplanted from living donors (NS). The delay after transplantation for the diagnosis of PTLD ranged from 7.4 months to 7.7 years. PTLD was a B cell lymphoma in six cases and affected extra nodal sites in most of the cases. The treatment, comprising the cessation of immunosuppressive therapy in all cases, resulted in complete remission in four patients. Three patients died, representing an annual death rate of 6.1%, versus 2.8% in patients without PTLD (NS). The annual incidence of graft loss was 6.1% versus 3.2% among patients without PTLD (NS). CONCLUSION: PTLD was observed in 2.2% of our patients, with an annual incidence of 0.32%. It resulted in a decrease of both patients' and grafts' survivals. Preventive measures, including the improvement of the monitoring of immunosuppressive drugs and the prevention of viral infections, should be considered to reduce the risk of PTLD.  相似文献   
77.
The relationship between substance use disorders and comorbid psychiatric conditions was investigated among 425 persons in drug treatment who met DSM-III-R criteria for drug dependence. Using the NIMH Diagnostic Interview Schedule to ascertain DSM-III-R psychiatric disorders among these drug dependent subjects, lifetime prevalence rates were 64% for alcohol abuse/dependence, 44% for antisocial personality disorder, 39% for phobic disorders, 24% for major depression, 12% for dysthymia, and 10% for generalized anxiety disorder. We found that antisocial personality disorder and phobias generally had onsets prior to the onset of drug dependence (that is, they were primary disorders). The majority of drug dependent persons with generalized anxiety disorder reported an onset after the onset of drug dependence (that is, they had secondary generalized anxiety). Alcohol dependence, depression, and dysthymia were divided nearly evenly between earlier (primary disorder) and later (secondary disorder). These results are consistent with the body of literature indicating the importance of antisocial syndromes in the etiology of substance abuse and the literature indicating the complex, varying nature of the relationship of psychiatric disorders to substance dependence. Finally, a precise nomenclature for "age of onset," "primary," and "secondary" was developed for this study that is critical to understanding these issues and is recommended for other studies.  相似文献   
78.
Spontaneous rupture of the spleen is a rare complication of chronic calcifying pancreatitis. Anemia and hemorrhagic shock may not occur, making diagnosis more difficult. Favourable response to conservative treatment does not prevent the need for splenectomy, as calcifiying chronic pancreatitis may progress locally. We report three cases of spontaneous rupture of the spleen. In two cases, splenic rupture revealed calcifying chronic pancreatitis and both patients underwent urgent splenectomy. In the third case, the patient was known to have calcifying chronic pancreatitis, and splenectomy was performed because of unsuccessful conservative treatment. We discuss the role of distal pancreatectomy during splenectomy to reduce the rate of postoperative complications and additional surgery. We also discuss the role of arterial embolisation and laparoscopy in the management of this rare condition.  相似文献   
79.
Multiple randomized trials support the treatment of patients with multivessel coronary artery disease (CAD) and relatively normal left ventricular (LV) ejection fraction (EF) by either percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG). However, there has been a paucity of trials in the recent literature that have compared the outcomes of patients with multivessel CAD and low EF who undergo PCI or CABG. This review examines some of the clinical trials and series in this subgroup of patients and also compares the outcome of patients undergoing either procedure in the absence and presence of LV dysfunction. These trials and series support the notion that PCI can be successfully performed in patients with low EF with relatively low mortality, but that CABG is associated with greater freedom from repeat revascularization and from angina or congestive heart failure symptoms. In addition, most of the data published thus far indicate a long-term survival advantage among patients with ventricular dysfunction who have undergone CABG. Further studies, including randomized trials incorporating the evolving techniques of CABG and the recent advances in PCI, will be needed to assess the proper role and outcome of these two interventions.  相似文献   
80.
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