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   13734篇
  免费   1010篇
  国内免费   70篇
耳鼻咽喉   105篇
儿科学   382篇
妇产科学   238篇
基础医学   2268篇
口腔科学   380篇
临床医学   1217篇
内科学   3140篇
皮肤病学   306篇
神经病学   1673篇
特种医学   284篇
外科学   1331篇
综合类   60篇
一般理论   9篇
预防医学   1056篇
眼科学   148篇
药学   1026篇
中国医学   50篇
肿瘤学   1141篇
  2024年   19篇
  2023年   137篇
  2022年   328篇
  2021年   633篇
  2020年   351篇
  2019年   451篇
  2018年   510篇
  2017年   398篇
  2016年   445篇
  2015年   484篇
  2014年   580篇
  2013年   719篇
  2012年   1115篇
  2011年   1189篇
  2010年   676篇
  2009年   551篇
  2008年   861篇
  2007年   901篇
  2006年   775篇
  2005年   756篇
  2004年   723篇
  2003年   602篇
  2002年   569篇
  2001年   103篇
  2000年   81篇
  1999年   89篇
  1998年   114篇
  1997年   108篇
  1996年   71篇
  1995年   69篇
  1994年   51篇
  1993年   39篇
  1992年   46篇
  1991年   38篇
  1990年   32篇
  1989年   17篇
  1988年   19篇
  1987年   10篇
  1986年   18篇
  1985年   25篇
  1984年   12篇
  1983年   15篇
  1982年   13篇
  1981年   13篇
  1980年   4篇
  1979年   6篇
  1978年   9篇
  1975年   4篇
  1974年   8篇
  1973年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Pulmonary sequestration is a congenital malformation characterised by cystic, non-functioning embryonic lung tissue with vascularisation of an abnormal systemic artery. They are classified as intralobar (75%) and extralobar (25%) and are more common in the left lung and lower lobes (60-90%). We report two cases of intralobar pulmonary sequestration located in the lower lobe of the left lung which were subjected to video-assisted thoracoscopic surgery (VATS). Both patients had recurrent infections for which, after performing imaging tests, they were diagnosed with intralobar pulmonary sequestration in the left lower lobe, with an afferent arterial branch to the malformation from the aorta. A lower lobectomy was performed by video-assisted surgery, dividing the aberrant aortic artery with an endostapler. A single thoracic chest tube was placed and removed on postoperative day 2 and the patients were discharged on the same day. In both cases, the pathology examination revealed intralobar pulmonary sequestration. Pulmonary sequestrations are uncommon malformations that can be operated on using minimally invasive techniques, thereby permitting early discharge and a low rate of complications.  相似文献   
92.

OBJECTIVE

The gut environment modulates the pathogenesis of type 1 diabetes (T1D), but how it affects autoimmunity toward pancreatic β-cells, a self-tissue located outside the intestine, is still unclear. In the small intestine, lamina propria dendritic cells (LPDCs) induce peripheral differentiation of FoxP3+ regulatory T (Treg) cells. We tested the hypothesis that the intestinal milieu impinges on human T1D by affecting differentiation of FoxP3+ Treg cells.

RESEARCH DESIGN AND METHODS

We collected duodenal biopsies of 10 T1D patients, 16 healthy subjects, and 20 celiac individuals and performed a fluorescent-activated cell sorter analysis to measure percentages of various immune cell subsets, including CD4+ and CD8+ T cells, NK cells, γδ T cells, CD103+CD11c+ LPDCs, and CD4+CD25+FoxP3+CD127 Treg cells. In parallel, we assessed the tolerogenic function (i.e., capacity to induce differentiation of FoxP3+ Treg cells) by LPDCs of T1D patients and control subjects.

RESULTS

Our analysis revealed a significant reduction in the percentage of intestinal CD4+CD25+FoxP3+CD127 Treg cells in T1D patients compared with healthy subjects (P = 0.03) and celiac individuals (P = 0.003). In addition, we found that LPDCs from T1D patients completely lacked their tolerogenic function; they were unable to convert CD4+CD25 T cells into CD4+CD25+FoxP3+CD127 Treg cells.

CONCLUSIONS

Our data indicate that T1D patients have a reduced number of intestinal FoxP3+ Treg cells as a result of their defective differentiation in the gut. These findings suggest that intestinal immune regulation is not only calibrated to tolerate commensal bacteria and food components but also is instrumental in maintaining immune tolerance toward pancreatic β-cells and preventing T1D.Type 1 diabetes (T1D) is a destructive islet β-cell specific autoimmune disease resulting from a yet undefined interaction between genetic and environmental factors (1). A dramatic increase in T1D incidence was recorded in most developed countries in the past 40 years (e.g., a threefold increase in Western countries) (2,3). The steady and rapid increase in T1D incidence cannot be ascribed to genetic variations and, thus, it must be related to environmental changes. Environmental agents such as viral infections (i.e., enteroviruses and rotaviruses) (4,5), reactions to dietary antigens (i.e., cow’s milk and gluten) (68), and microbiota alterations (9) that act at the intestinal level have been observed in association with, or as risk factors for, the development of T1D. The observation that development of clinical diabetes in patients is preceded by intestinal alterations such as increased permeability, immune activation, and ultrastructural abnormalities of the epithelium (1016) provides additional evidence on the crucial role of the gut environment in human T1D. Although existing evidence is suggestive of a causative link between the gut milieu and the pathogenesis of T1D, it is still unclear whether and by which mechanism(s) a dysfunction in the intestine promotes autoimmunity elsewhere (i.e., in the pancreatic β-cells) and if it does, how this process occurs.Important immune regulatory mechanisms reside in the intestinal mucosa. FoxP3+ regulatory T (Treg) cells, a Treg cell subset that is instrumental to controlling T1D (17), arise centrally in the thymus and peripherally in the gut (18). Specifically, lamina propria CD103+CD11c+ dendritic cells (LPDCs) are responsible for extrathymic FoxP3+ Treg cell development and expansion (18,19). Considering the key immune regulatory role of FoxP3+ Treg cells, it is clear that their defective peripheral differentiation in the gut could lead to failure of self-tolerance and autoimmune disease, particularly in tissues such as pancreatic islets and lymph nodes that are directly connected to the intestinal mucosa and gut-associated lymphoid tissue (20).Here we demonstrate that the extrathymic differentiation of FoxP3+ Treg cells by gut-resident CD103+CD11c+ dendritic cells (DCs) is selectively impaired in humans affected by T1D. Our findings indicate that organ-specific autoimmune diseases such as T1D could be initiated and possibly maintained by virtue of changes in peripheral FoxP3+ Treg cell differentiation and/or expansion in the gut.  相似文献   
93.
Chronic tubulo-interstitial disease, an important cause of end-stage renal disease, often results from the combined effects of a disturbed urinary outflow tract and urinary tract infection. Acute unilateral ureteral obstruction in rats rapidly induces foci of medullary necrosis, confined to the region of the papilla and fornices. This injury may provide a nidus for bacterial invasion and may invoke reactive and regenerative changes, ultimately leading to chronic pyelonephritis and tubulo-interstitial nephropathy. To explore this possibility, adult rats underwent renal morphological evaluation 2–7 days following transient 24-h unilateral ureteral obstruction. In some experiments the bladder was inoculated with bacteria (108–109 cfu/ml Escherichia coli in 0.5 ml) after release of ureteral obstruction, with subsequent cultures obtained from the pelvis of both kidneys and from the urinary bladder. Morphologic evaluation of perfusion-fixed kidneys, 2–7 days after the release of 24-h ureteral obstruction disclosed papillary necrosis, urothelial proliferation, marked inner-stripe interstitial expansion, and fibrosis and proximal tubular (S3) dilatation. The lateral (perihilar region) was predominantly affected, with lesions spreading from the fornices. There was some progression of interstitial fibrosis during the postobstructive time course or following more prolonged ureteral obstruction. By contrast, infection hardly contributed to the tubulointerstitial changes. In rats subjected to infection, cultures were positive in all 15 postobstructive kidneys, as opposed to five contralateral kidneys (P < 0.0001). Viable counts from the postobstructive kidney were also higher than those from the contralateral side (79,000 ± 12,000 vs 2900 ± 1600 cfu/ml, mean ± SEM, P < 0.0001), and were comparable to those obtained from the bladder (77,000 ± 13,000 cfu/ml). We conclude that transient ureteral obstruction predisposes to ascending pyelonephritis and to tubulointerstitial disease. This vulnerability may relate to altered urodynamics and medullary tissue destruction. Received: 28 December 1999 / Accepted: 28 September 2000  相似文献   
94.
Mandibulofacial dysostosis (Treacher Collins Syndrome) is an autosomal dominant genetic disorder that probably derives from inhibition of the facial structures from the first and second branchial arches. The facial pattern of the syndrome is a convex facial profile with a prominent nose above a retruded chin. The eyes are deformed by antimongoloid slant of the palpebral fissures and facial bones are hypoplastic. The alterations are caused by mutation in gene 5q32-33.1, which encodes the nucleolar phosphoprotein treacle. Computed tomography images are able to demonstrate craniofacial bones, allowing the morphological analysis of these bones in individuals with complex deformities. The purpose of this paper is to present the results of a clinical and computed tomography investigation of two patients with Treacher Collins syndrome.  相似文献   
95.
Activation of AMP-activated protein kinase (AMPK) by exercise induces several cellular processes in muscle. Exercise activation of AMPK is unaffected in lean (BMI approximately 25 kg/m(2)) subjects with type 2 diabetes. However, most type 2 diabetic subjects are obese (BMI >30 kg/m(2)), and exercise stimulation of AMPK is blunted in obese rodents. We examined whether obese type 2 diabetic subjects have impaired exercise stimulation of AMPK, at different signaling levels, spanning from the upstream kinase, LKB1, to the putative AMPK targets, AS160 and peroxisome proliferator-activated receptor coactivator (PGC)-1alpha, involved in glucose transport regulation and mitochondrial biogenesis, respectively. Twelve type 2 diabetic, eight obese, and eight lean subjects exercised on a cycle ergometer for 40 min. Muscle biopsies were done before, during, and after exercise. Subjects underwent this protocol on two occasions, at low (50% Vo(2max)) and moderate (70% Vo(2max)) intensities, with a 4-6 week interval. Exercise had no effect on LKB1 activity. Exercise had a time- and intensity-dependent effect to increase AMPK activity and AS160 phosphorylation. Obese and type 2 diabetic subjects had attenuated exercise-stimulated AMPK activity and AS160 phosphorylation. Type 2 diabetic subjects had reduced basal PGC-1 gene expression but normal exercise-induced increases in PGC-1 expression. Our findings suggest that obese type 2 diabetic subjects may need to exercise at higher intensity to stimulate the AMPK-AS160 axis to the same level as lean subjects.  相似文献   
96.
A controversy exists over whether the outcome of a hepatitis C virus (HCV)-infection-related liver transplant differs based on the calcineurin inhibitor (CNI) used. We have performed a systematic review and a subsequent meta-analysis evaluating tacrolimus (Tac)-based vs. cyclosporine A-based immunosuppression in HCV-infected liver transplant recipients. Searches were conducted to locate randomized controlled trials comparing Tac vs. cyclosporine A. Data on HCV liver transplant recipients were obtained, independently of whether the study was specifically designed for patients with this disease or not. A fixed effects model was used for statistical pooling of the relative risks (RR) for the different outcomes. A total of 5 articles (366 patients) fulfilled the inclusion criteria. Statistically significant differences between Tac-based vs. cyclosporine A-based therapies were not found for mortality (P = 0.11; RR = 0.72; 95% confidence interval [CI], 0.49-1.08), graft survival (P = 0.37; RR = 0.86; 95% CI, 0.61-1.21), biopsy-proven acute rejection (P = 0.65; RR = 0.91; 95% CI, 0.61-1.36), corticoresistant acute rejection (P = 0.26; RR = 2.25; 95% CI, 0.55-9.29), and fibrosing cholestatic hepatitis (P = 0.92; RR = 0.96; 95% CI, 0.41-2.26). In 1 study, no differences were detected regarding severe fibrosis at 1 yr. In conclusion, patient and graft survivals in HCV-positive liver transplant patients are similar independently of the CNI selected as basic immunosuppressant. Unfortunately, data on the severity of recurrence and effect on viremia are scarce. Well-designed randomized prospective studies are needed to determine whether there are differences between the 2 CNIs regarding these specific variables.  相似文献   
97.
Recurrent herpes labialis is a worldwide life-long oral health problem that remains unsolved. It affects approximately one third of the world population and causes frequent pain and discomfort episodes, as well as social restriction due to its compromise of esthetic features. In addition, the available antiviral drugs have not been successful in completely eliminating the virus and its recurrence. Currently, different kinds of laser treatment and different protocols have been proposed for the management of recurrent herpes labialis. Therefore, the aim of the present article was to review the literature regarding the effects of laser irradiation on recurrent herpes labialis and to identify the indications and most successful clinical protocols. The literature was searched with the aim of identifying the effects on healing time, pain relief, duration of viral shedding, viral inactivation, and interval of recurrence. According to the literature, none of the laser treatment modalities is able to completely eliminate the virus and its recurrence. However, laser phototherapy appears to strongly decrease pain and the interval of recurrences without causing any side effects. Photodynamic therapy can be helpful in reducing viral titer in the vesicle phase, and high-power lasers may be useful to drain vesicles. The main advantages of the laser treatment appear to be the absence of side effects and drug interactions, which are especially helpful for older and immunocompromised patients. Although these results indicate a potential beneficial use for lasers in the management of recurrent herpes labialis, they are based on limited published clinical trials and case reports. The literature still lacks double-blind controlled clinical trials verifying these effects and such trials should be the focus of future research.  相似文献   
98.
The optimal immunosuppressive regimen for recipients of expanded criteria donor (ECD) kidneys has not been identified. In this single‐center study, 171 recipients of ECD kidney transplants were randomized to receive antithymocyte globulin induction, and delayed introduction of reduced dose tacrolimus, prednisone and everolimus (r‐ATG/EVR, n = 88), or mycophenolate (r‐ATG/MPS, n = 83). No cytomegalovirus (CMV) pharmacological prophylaxis was used. The primary endpoint was the incidence of CMV infection/disease at 12 months. Secondary endpoints included treatment failure [first biopsy‐proven acute rejection (BPAR), graft loss, or death] and safety. Patients treated with EVR showed a 89% risk reduction (13.6 vs. 71.6%; HR 0.11, 95% CI 0.06–0.220, P < 0.001) in the incidence of first CMV infection/disease. Incidences of BPAR (16% vs. 5%, P = 0.021), graft loss (11% vs. 1%, P = 0.008), death (10% vs. 1%, P = 0.013), and treatment discontinuation (40% vs. 28%, P = 0.12) were higher in the r‐ATG/EVR, leading to premature study termination. Mean glomerular filtration rate was lower in r‐ATG/EVR (31.8 ± 18.8 vs. 42.6 ± 14.9, P < 0.001). In recipients of ECD kidney transplants receiving no CMV pharmacological prophylaxis, the use of everolimus was associated with higher treatment failure compared with mycophenolate despite the significant reduction in the incidence of CMV infection/disease (ClinicalTrials.gov.NCT01895049).  相似文献   
99.
Brochures are a useful supplement to patient education. There is increasing evidence that they are an effective medium to support patient satisfaction, adherence, and empowerment. This study aims to produce reliable data on how much patients with venous leg ulcer (VLU) may profit from a brochure that focuses on VLU and on measures and aims of the related compression therapy. The evaluation took part from October 2018 until March 2019 and included 136 patients with VLU and related compression therapy. They were randomly sorted into a case group and a control group of 68 patients each. The case group received a brochure about venous disease and compression therapy and filled in a questionnaire after reading. The questions ranged from basic knowledge about VLU and compression therapy to aspects of self‐care. The control group answered the same questions without previous reading of the brochure. The results show that in almost every aspect, the patients in the case group were better informed about their diseases, the compression therapy, and how they may support the measures adequately. This study suggests that patients with VLU may profit from a brochure that explains their disease and the related compression therapy. Better knowledge and understanding may strengthen their empowerment and adherence.  相似文献   
100.
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