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   56439篇
  免费   4541篇
  国内免费   153篇
耳鼻咽喉   511篇
儿科学   1510篇
妇产科学   1082篇
基础医学   7480篇
口腔科学   954篇
临床医学   6257篇
内科学   10813篇
皮肤病学   804篇
神经病学   4865篇
特种医学   2196篇
外科学   9413篇
综合类   782篇
一般理论   57篇
预防医学   5599篇
眼科学   1263篇
药学   4049篇
  1篇
中国医学   56篇
肿瘤学   3441篇
  2023年   321篇
  2022年   452篇
  2021年   1157篇
  2020年   655篇
  2019年   1088篇
  2018年   1311篇
  2017年   956篇
  2016年   1028篇
  2015年   1233篇
  2014年   1801篇
  2013年   2499篇
  2012年   3812篇
  2011年   3907篇
  2010年   2114篇
  2009年   1874篇
  2008年   3400篇
  2007年   3651篇
  2006年   3545篇
  2005年   3444篇
  2004年   3185篇
  2003年   3031篇
  2002年   2864篇
  2001年   888篇
  2000年   845篇
  1999年   839篇
  1998年   642篇
  1997年   517篇
  1996年   488篇
  1995年   515篇
  1994年   431篇
  1993年   405篇
  1992年   546篇
  1991年   490篇
  1990年   507篇
  1989年   474篇
  1988年   435篇
  1987年   378篇
  1986年   388篇
  1985年   434篇
  1984年   372篇
  1983年   305篇
  1982年   257篇
  1981年   233篇
  1980年   215篇
  1979年   242篇
  1978年   234篇
  1974年   210篇
  1973年   194篇
  1972年   188篇
  1968年   185篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
BACKGROUND CONTEXT: The injection of various solutions aimed at producing a sclerosing effect has been used to treat soft tissues injuries (eg, inguinal hernia) for more than 100 years. In the 1930s, this treatment approach was applied to injured joints in an attempt to stimulate connective tissue repair. Although several studies have been published about this method of treatment for various orthopedic and spinal indications (termed prolotherapy), its use remains controversial. PURPOSE: To conduct a critical review of the literature on prolotherapy for spinal pain. STUDY DESIGN/SETTING: Critical review of the literature. METHODS: Computerized medical literature databases (Medline, CINAHL, Mantis, Cochrane Central Register of Controlled Trials) were searched to uncover all published information about the use of sclerosing injections in humans with spinal pain disorders. Search results were reviewed for relevance, and information was abstracted from full-text articles. RESULTS: Our search uncovered almost 200 reference materials in various media related to prolotherapy, including 31 clinical studies related to spinal pain. There were 26 observational cohorts and 5 randomized clinical trials (RCTs). Indications in these studies were low back pain (22), neck pain (3), cervical headaches (3) and dorsal or thoracic pain (3). A total of 20 sclerosing solutions were used in these studies; the most common was a mixture of dextrose 12.5%, glycerin 12.5%, phenol 1.25% and lidocaine 0.25%. Wide variations were found in treatment protocols, such as dose, number of treatments and use of adjunct therapies. Most cohort studies were only of moderate quality and varied greatly in the substances injected and the use of co-interventions. Most clinical studies reported positive results such as decreased pain or disability, although differences between treatment and control groups did not always reach statistical significance. Commonly reported adverse reactions to this treatment include temporary postinjection pain and stiffness. A handful of more serious adverse events were reported in the 1950s and 1960s with stronger or unknown solutions. CONCLUSION: Prolotherapy describes a variety of treatment approaches rather than a specific protocol. Results from clinical studies published to date indicate that it may be effective at reducing spinal pain. Great variation was found in the injection and treatment protocols used in these studies that preclude definite conclusions. Future research should focus on those solutions and protocols that are most commonly used in clinical practice and have been used in trials reporting effectiveness to help determine which patients, if any, are most likely to benefit from this treatment.  相似文献   
52.
<正> KEY POINTS  Accurate body composition assessments are vital to monitoring growth, training outcomes, health, and nutritional status of athletes.  Body composition assessment in athletes and other relies on non-invasive indirect methods that are based on theoretical models. Any errors in the theoretical models will produce errors in the indirect methods. performance.  相似文献   
53.
Two fatal cases of thermal injury are described, one of which was the result of heat stroke and the other was the result of the uncommon condition, neuroleptic malignant syndrome. The clinical profiles, management and post-mortem findings of these two separate conditions are compared to highlight their important differences.  相似文献   
54.
Chiari II malformation: MR imaging evaluation   总被引:4,自引:0,他引:4  
The purpose of this study was to explore the value of high-detail MR imaging in the diagnosis of the Chiari II malformation. Twenty-four patients with known Chiari II malformation as diagnosed by CT scanning were evaluated with cranial MR scans. Two patients also had spine scans. The sagittal-plane images were the most informative, and abnormalities of the telencephalon, diencephalon, mesencephalon, rhomboencephalon, upper spinal cord, and mesencephalon were shown extremely well. We found MR to be an easy and accurate method for demonstrating the abnormalities of the Chiari II malformation, and it is our procedure of choice.  相似文献   
55.
A single retrocardiac air-fluid level on a chest radiograph typically implies the presence of a sliding hiatal hernia. A differential retrocardiac fluid level (two air-fluid interfaces at different heights) suggests not a simple sliding hiatal hernia but rather an intrathoracic gastric volvulus. Simultaneous fluid levels above and below the diaphragm are not required to make the diagnosis. We have seen four patients with chronic gastric volvulus confirmed by upper gastrointestinal barium examination. Each case was diagnosable on the basis of the chest radiographs obtained on admission, using the radiographic sign described above. We draw attention to this sign because chronic gastric volvulus has the potential to progress to acute volvulus and gastric ischemia or infarction.  相似文献   
56.
57.
We identified 18 patients with double-orifice mitral valve (DOMV) and intact atrioventricular (AV) septum out of 40,179 echocardiographic studies performed between 1997 and 2002 at Children's Hospital, Denver, CO. In this study we describe (1) the anatomic characteristics of the DOMV in the absence of AV septal defect, (2) the function of the mitral valve by spectral and color Doppler flow mapping, and (3) associated lesions. The topographic location of the orifices in the leaflets suggests possible embryologic mechanisms of DOMV. In this series, DOMV was most commonly associated with left-sided obstructive lesions (in 39% of patients). Spectral and color Doppler interrogation demonstrated a normal flow profile in most cases; only 2 patients had significant mitral regurgitation or stenosis. Therefore, due to the uncertain natural history of this lesion and the potential need for endocarditis prophylaxis, careful imaging of the mitral valve is recommended, particularly in the presence of left-sided obstructive lesions.  相似文献   
58.
BACKGROUND: Interferon-gamma, produced by T-helper cells, activates macrophages and increases expression of major histocompatibility complex (MHC) products in acute and chronic rejection. We investigated the role of interferon-gamma in murine heterotopic tracheal allografts. METHODS: Tracheas from BALB/c mice were heterotopically transplanted to BALB/c (12 isografts: 2 weeks [n = 6] and 4 weeks [n = 6], C57BL/6 (12 allografts: 2 weeks [n = 6] and 4 weeks [n = 6]) and C57BL/6 interferon-gamma knockout mice (12 interferon-gamma knockout allografts: 2 weeks [n = 4] and 4 weeks [n = 8]). BALB/c interferon-gamma knockout tracheas were transplanted to C57BL/6 mice (reverse knockout: 4 weeks [n = 6]) and BALB/c interferon-gamma knockout mice (4 weeks [n = 2]). C57BL/6 tracheas were transplanted to Bm12 mice (MHC Class II mismatch allografts: 4 weeks [n = 6]). Conventional histology and immunohistochemistry for CD4, CD8 and CD11b were performed. RESULTS: Minimal (<20%) obliteration was seen at 2 weeks in the allograft groups. No obliteration was seen in the isograft groups. However, all allografts were completely obliterated at 4 weeks. Interferon-gamma knockout allograft combinations displayed severe rejection characterized by intense intra- and extraluminal infiltration by CD4-, CD8- and CD11b-labeled cells. The MHC Class II mismatch allograft group showed normal epithelium and mild sub-epithelial infiltration by CD4+ cells at 4 weeks (CD8-, CD11b-). CONCLUSIONS: Absence of interferon-gamma does not protect the allograft from obliteration. Epithelial destruction by cytotoxic T cells appears to be an important mechanism in the development of obliteration in murine heterotopic tracheal allografts.  相似文献   
59.
60.
Bone metastases develop in approximately 30% of patients with RCC, and the mechanisms responsible for this phenomenon are unknown. We found that TGF-beta1 stimulation of RCC bone metastasis cells promotes tumor growth and bone destruction possibly by stimulating paracrine interactions between tumor cells and the bone. INTRODUCTION: Bone metastasis is a frequent complication and causes marked morbidity in patients with renal cell carcinoma (RCC). Surprisingly, the specific mechanisms of RCC interaction with bone have been scarcely studied despite the inability to prevent or effectively treat bone metastasis. Bone is a reservoir for various growth factors including the pleiotropic cytokine TGF-beta1. TGF-beta1 has been shown to have tumor-supportive effects on advanced cancers and evidence suggests its involvement in promoting the development of breast cancer bone metastasis. Here, we studied the potential role of TGF-beta1 in the growth of RCC bone metastasis (RBM). MATERIALS AND METHODS: To inhibit TGF-beta1 signaling, RBM cells stably expressing a dominant-negative (DN) TGF-betaRII cDNA were generated. The in vivo effect of TGF-beta1 on RBM tumor growth and osteolysis was determined by histological and radiographic analysis, respectively, of athymic nude mice after intratibial injection of parental, empty vector, or DN RBM cells. The in vitro effect of TGF-beta1 on RBM cell growth was determined after TGF-beta1 treatment by MTT assay. RESULTS: TGF-beta1 and the TGF-beta receptors I and II (TGF-betaRI/II) were consistently expressed in both RBM tissues and cell lines. Inhibition of TGF-beta1 signaling in RBM cells significantly reduced tumor establishment and osteolysis observed in vivo after injection into the murine tibia, although no effect on tumor establishment was observed after injection of RBM cells subcutaneously or into the renal subcapsule. Treatment of five RBM cell lines with TGF-beta1 in vitro either had no effect (2/5) or resulted in a significant inhibition (3/5) of cell growth, suggesting that TGF-beta1 may promote RBM tumor growth indirectly in vivo. CONCLUSIONS: TGF-beta1 stimulation of RBM cells plays a role in promoting tumor growth and subsequent osteolysis in vivo, likely through the initiation of tumor-promoting paracrine interactions between tumor cells and the bone microenvironment. These data suggest that inhibition of TGF-beta1 signaling may be useful in the treatment of RBM.  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