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   21386篇
  免费   5665篇
  国内免费   127篇
耳鼻咽喉   625篇
儿科学   634篇
妇产科学   692篇
基础医学   315篇
口腔科学   2664篇
临床医学   4151篇
内科学   5127篇
皮肤病学   454篇
神经病学   1830篇
特种医学   1012篇
外科学   3779篇
综合类   55篇
现状与发展   12篇
预防医学   2698篇
眼科学   339篇
药学   198篇
中国医学   6篇
肿瘤学   2587篇
  2024年   163篇
  2023年   1092篇
  2022年   357篇
  2021年   636篇
  2020年   1214篇
  2019年   488篇
  2018年   1330篇
  2017年   1292篇
  2016年   1509篇
  2015年   1575篇
  2014年   1964篇
  2013年   2360篇
  2012年   770篇
  2011年   723篇
  2010年   1357篇
  2009年   1944篇
  2008年   742篇
  2007年   504篇
  2006年   643篇
  2005年   447篇
  2004年   327篇
  2003年   281篇
  2002年   253篇
  2001年   385篇
  2000年   282篇
  1999年   385篇
  1998年   504篇
  1997年   481篇
  1996年   536篇
  1995年   387篇
  1994年   301篇
  1993年   260篇
  1992年   176篇
  1991年   155篇
  1990年   138篇
  1989年   143篇
  1988年   126篇
  1987年   122篇
  1986年   100篇
  1985年   100篇
  1984年   75篇
  1983年   90篇
  1982年   82篇
  1981年   67篇
  1980年   45篇
  1979年   33篇
  1978年   32篇
  1977年   43篇
  1976年   31篇
  1975年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Hypertrophic scars (HS) are a consequence of abnormal wound healing. We examined fatty acids that are contained within, and participate in, every reaction through the membrane; then, we analyzed the percentage composition of the fatty acids in deepithelialized normal dermis (ND) and HS. In vivo HS samples were obtained from six patients undergoing surgical excision, and ND samples from five patients undergoing skin grafting surgery for excess. In vitro, cultured fibroblasts from HS and ND were also analyzed. The percentage composition of fatty acids extracted from all the samples was analyzed. In vivo, arachidonic acid (20:4) was significantly more abundant in HS than in ND, in the phospholipids from both whole tissue and cell membranes. In vitro, there were no significant differences among ND, HS, and 10% fetal calf serum. The results suggest that HS formation does not necessarily involve simple excess of 20:4; however, there are considerable differences in the percentage composition of 20:4 between ND and HS. Arachidonic acid probably participates in the formation and maintenance of HS, whereas in vitro cultured fibroblasts are affected largely by fetal calf serum.  相似文献   
72.
73.
The popularity of vital tooth whitening has increased significantly over the past two decades. Professionally supervised "in-office" and "at-home" tooth whitening methods have been documented in the literature with evidence of safety and effectiveness. Although the literature includes considerable information about vital tooth whitening in adults, minimal information is available concerning vital tooth whitening in children and adolescents.
The need to provide vital tooth whitening for children might be infrequent owing to the natural whiteness of children's teeth. However, there are circumstances when tooth whitening can be desirable for children, such as fluorosis discoloration, generalized tooth darkening, post-traumatic injury discoloration, and postorthodontic tooth discoloration.
Few well-controlled clinical trials evaluating the safety and effectiveness of vital tooth whitening in children are available in the literature, Furthermore, these published clinical trials were carried out by the same principal investigator. This review examines these trials and offers recommendations accordingly.  相似文献   
74.
Keloid formation has been linked to aberrant fibroblast activity, exacerbated by growth factors and inflammatory mediators. Prostaglandin E2 (PGE2), synthesized from arachidonic acid by cyclooxygenases (COX) and synthases (PGES), acts as both an inflammatory mediator and fibroblast modulator. Although PGE2 has known antifibrotic effects in the lower airway, its role in dermal fibrosis in general, and keloid formation in particular, remains unclear. This study focused on: (1) the effects of PGE2 on keloid fibroblast migration, contraction, and collagen synthesis and (2) endogenous PGE2 synthesis in response interleukin-1beta. PGE2 decreased keloid fibroblast migration and contraction via an EP2/EP4-cAMP mechanism that disrupted actin cytoskeletal dynamics and reversed transforming growth factor-beta1-induced collagen I and III synthesis. Impaired fibroblast PGE2 production has been linked to lower airway fibrosis and recently to keloid formation. Here, we showed that interleukin-1beta stimulation leads to nuclear factor-kappaB translocation to the nucleus, resulting in up-regulation of COX-2 and microsomal PGE2 synthase 1. Up-regulation of COX-2 in, and secretion of PGE2 by keloid fibroblasts are diminished compared with their normal fibroblast counterparts. We suggest that the antifibrotic effects of PGE2 during keloid formation are potentially diminished due to aberrant paracrine fibroblast signaling. Exogenous PGE2 may supplement decreased endogenous levels and inhibit keloid formation or progression.  相似文献   
75.
BACKGROUND: Patients with primary axillary hyperhidrosis experience substantial functional impairment and reduced health-related quality of life (HRQOL). Few studies have comprehensively evaluated the effects of botulinum toxin type A (BoNT-A) on these symptoms. OBJECTIVE: To prospectively assess the effects of BoNT-A on functional impairment associated with primary axillary hyperhidrosis. METHODS: Patients treated with BoNT-A 50 U per axilla at baseline were assessed 4 and 12 weeks later. Outcome measures included functional impairment as assessed by the Hyperhidrosis Disease Severity Scale and the Hyperhidrosis Impact Questionnaire and dermatology-specific HRQOL as assessed by the Dermatology Life Quality Index. RESULTS: At weeks 4 and 12 after BoNT-A treatment, 85% and 90% of patients achieved the a priori definition of treatment responder. Patients reported less occupational and emotional impairment, spent less time managing their hyperhidrosis, and had fewer difficulties in social situations. Adverse events were uncommon (5.5%), were mild, and did not require treatment. At study end, 53% of patients reported no dermatology-specific HRQOL impairment and 90% were satisfied with treatment. CONCLUSIONS: Significant, meaningful, rapid, and durable reductions in disease severity and functional impairment, as well as improvements in HRQOL, were seen following BoNT-A treatment. BoNT-A was safe and well tolerated, producing high levels of patient satisfaction.  相似文献   
76.
BACKGROUND: The results from four phase III, randomized, vehicle-controlled studies showed that imiquimod 5% cream (imiquimod) was safe and effective in the treatment of actinic keratosis (AK). Patients applied imiquimod or vehicle cream to AK lesions on the face or balding scalp, dosing three times per week or two times per week for 16 weeks. OBJECTIVE: To obtain long-term safety follow-up data and estimate AK recurrence in patients who completely cleared their AK lesions in the treatment area at the 8-week post-treatment visit in the phase III studies. METHODS: One hundred forty-six patients from 30 study centers in the United States were evaluated for clinical evidence of AK, and safety data were collected. RESULTS: After a median follow-up period of 16 months, 24.7% (19 of 77) of the patients administered imiquimod three times per week and 42.6% (23 of 54) of the patients administered imiquimod two times per week had a recurrence of AK (the appearance of at least one AK lesion) in the original treatment area. The median number of AK lesions present was one lesion for both patients receiving imiquimod three times and those receiving imiquimod two times per week compared with a median of six lesions at baseline in the combined three times per week and two times per week phase III studies. There were no long-term safety issues, and the skin quality seen in the imiquimod-treated patients at the end of the phase III studies was maintained. CONCLUSION: One and a half years following treatment, imiquimod continued to provide a long-term clinical benefit in a majority of patients who experienced complete clearance of their AK lesions.  相似文献   
77.
This self-instructional guide is designed for the nurse who works primarily in an adult patient setting but occasionally cares for a pediatric client. Although proficient in nursing skills, this nurse might experience anxiety when assigned a pediatric client. It is hoped that having this information will replace anxiety with confidence.  相似文献   
78.
79.
80.
OBJECTIVES: Brain edema occurs following clinical as well as experimental cardiac arrest (CA) and predicts a poor neurologic outcome. The objective of this study was to determine the expression of cerebral cortex aquaporin (AQP)-4, a member of a family of membrane water-channel proteins, in brain edema formation following normothermic or hypothermic CA. METHODS: Twenty-four rats were subjected to time-matched normothermic (N-Sham, 37.5 degrees C +/- 0.5 degrees C, n = 6) or hypothermic (H-Sham, 34 degrees C +/- 0.5 degrees C, n = 6) sham experiments and normothermic (N-CA, n = 6) or hypothermic (H-CA, n = 6) CA induced by asphyxiation for 8 minutes. Hypothermia was induced before CA. The animals were resuscitated with cardiopulmonary resuscitation, ventilation, and epinephrine administration. Brain edema was determined by brain wet-to-dry weight ratio at one hour of resuscitation. AQP4 immunoactivity in the cerebral cortex was determined using immunohistochemical staining and was semiquantified as an intensity of staining with an automated cell imaging system. RESULTS: Mild hypothermia in the sham experiments did not alter cerebral cortex AQP4 immunoactivity (mean +/- SD) (55.0 +/- 3.7 in H-Sham vs. 53.3 +/- 1.7 in N-Sham, p > 0.05). N-CA resulted in a significant increase in AQP4 immunoactivity (61.8 +/- 4.5) compared with N-Sham (p = 0.01) and H-Sham (p = 0.03). H-CA attenuated AQP4 compared with N-CA (53.4 +/- 1.3, p = 0.01). Brain wet-to-dry weight ratios were 4.41 +/- 0.07 in N-Sham, 4.40 +/- 0.08 in H-Sham (p > 0.05 vs. N-Sham), 4.55 +/- 0.04 in N-CA (p = 0.004 vs. N-Sham; p = 0.005 vs. H-Sham), and 4.43 +/- 0.09 in H-CA (p = 0.02 vs. N-CA; p > 0.05 vs. N-Sham and H-Sham). CONCLUSIONS: Cerebral cortical AQP4 expression is up-regulated after normothermic CA, which is attenuated by hypothermia induced before CA.  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