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   6337篇
  免费   458篇
  国内免费   47篇
耳鼻咽喉   70篇
儿科学   209篇
妇产科学   89篇
基础医学   932篇
口腔科学   423篇
临床医学   539篇
内科学   1271篇
皮肤病学   161篇
神经病学   463篇
特种医学   293篇
外科学   818篇
综合类   53篇
一般理论   1篇
预防医学   643篇
眼科学   97篇
药学   476篇
中国医学   33篇
肿瘤学   271篇
  2023年   63篇
  2022年   132篇
  2021年   177篇
  2020年   139篇
  2019年   135篇
  2018年   222篇
  2017年   181篇
  2016年   184篇
  2015年   225篇
  2014年   299篇
  2013年   391篇
  2012年   465篇
  2011年   463篇
  2010年   278篇
  2009年   301篇
  2008年   350篇
  2007年   350篇
  2006年   317篇
  2005年   235篇
  2004年   185篇
  2003年   170篇
  2002年   168篇
  2001年   127篇
  2000年   111篇
  1999年   97篇
  1998年   129篇
  1997年   107篇
  1996年   109篇
  1995年   78篇
  1994年   86篇
  1993年   48篇
  1992年   35篇
  1991年   35篇
  1990年   31篇
  1989年   40篇
  1988年   35篇
  1987年   41篇
  1986年   40篇
  1985年   30篇
  1984年   19篇
  1983年   13篇
  1982年   28篇
  1981年   18篇
  1980年   21篇
  1979年   13篇
  1978年   12篇
  1977年   15篇
  1976年   18篇
  1975年   13篇
  1969年   21篇
排序方式: 共有6842条查询结果,搜索用时 15 毫秒
81.
82.
83.
This study investigated the prevalence of dental caries and periodontal condition in a population with sickle cell disease (SCD), analyzing some associations with disease severity. The Decayed, Missing and Filled Teeth index (DMFT) and Community Periodontal Index (CPI) were recorded for 99 individuals with SCD and 91 matched controls. Socio-demographic status, oral health behaviors, and history of clinical severity of SCD were assessed. Statistical comparisons were performed between the group with SCD and the control group, as well as multivariate logistic regression analyses with DMFT index and CPI as the dependent variables. The mean number of decayed teeth was significantly higher in individuals with HbSS. Older age, female gender, and daily smoking were identified as risk factors for higher DMFT, while older age and absence of daily use of dental floss were risk factors for the development of periodontal disease. In conclusion, risk factors known to cause caries and periodontal disease had more influence on oral health than the direct impact of SCD.  相似文献   
84.
Inflammation is part of the physiological process that aims at repairing the damage produced by different causes such as infection, trauma, and autoimmune disease. However, when this physiological process is not regulated, it can contribute to the increase in tissue damage. Chemokines and their receptors are major factors involved in the process of cell migration into inflamed tissues. In the ocular diseases, mainly in uveitis, such proteins have been identified as important mediators of the inflammation process. This review discusses the role of chemokines in several ocular diseases, with emphasis on the uveitic process.  相似文献   
85.
PURPOSE: To determine the incidence of hypotony and intraocular pressure (IOP) elevation in the immediate and early postoperative period after temporal posterior limbal phacoemulsification and intraocular lens (IOL) implantation. SETTING: Ambulatory surgical center. METHODS: This prospective analysis comprised 310 eyes that had temporal posterior limbal phacoemulsification with IOL implantation. Surgical parameters included keratome incision of 2.85 mm, incision length of 2.5 mm, peribulbar anesthesia, case-completion IOP of 20 mm Hg, and postoperative lid taping. The IOP measurements were collected preoperatively and 30 minutes and 1 day after surgery. RESULTS: Nineteen eyes (6.1%) had an IOP lower than 5 mm Hg 30 minutes postoperatively in the absence of incision leakage at the paracentesis or keratome sites. Eighteen of the 19 eyes with postoperative hypotony received hydroxypropyl methylcellulose 2% (OcuCoat) and 1 received hypromellose 2% (Cellugel). None of the 23 eyes with an acrylic IOL implanted via a cylindrical lens inserter had an IOP lower than 5 mm Hg postoperatively. Suturing did not significantly affect the incidence of hypotony, and there were no postoperative complications related to hypotony. The mean IOP at 30 minutes was lower than at 1 day in the normal, glaucoma, and glaucoma-suspect groups. Twenty-one normal eyes (8.1%), 5 glaucoma eyes (15.6%), and 1 glaucoma-suspect eye (5%) had an IOP greater than 30 mm Hg 1 day postoperatively. CONCLUSIONS: Postoperative hypotony (IOP <5 mm Hg) occurred in 19 (6.1%) of 310 eyes. At 1 day, IOP higher than 30 mm Hg was more frequent in glaucoma eyes than in normal eyes. Although there were no direct problems related to hypotony at 30 minutes or to elevated IOP (>30 mm Hg) at 1 day, surgeons should be aware of and check for IOP variability (low and high) that can occur in normal, glaucoma, and glaucoma-suspect eyes within the first 24 hours after surgery.  相似文献   
86.
The anatomic response to intravitreal bevacizumab injection in three patients with aggressive, posterior retinopathy of prematurity is described. In all cases, the worse eye was treated with a single intravitreal injection of 0.75 mg of bevacizumab as monotherapy or complementary to laser therapy. In 24 hours, all injected eyes showed regression of the tunica vasculosa lentis and iris vessel engorgement and disappearance of iris rigidity. In addition, plus disease and retinal proliferation began to regress. None of the eyes required additional treatment. Follow-up of up to 10 months  相似文献   
87.
88.
BACKGROUND AND PURPOSE:Primary posterior fossa tumors comprise a large group of neoplasias with variable aggressiveness and short and long-term outcomes. This study aimed to validate the clinical usefulness of a radiologic decision flow chart based on previously published neuroradiologic knowledge for the diagnosis of posterior fossa tumors in children.MATERIALS AND METHODS:A retrospective study was conducted (from January 2013 to October 2019) at 2 pediatric referral centers, Children''s Hospital of Philadelphia, United States, and Great Ormond Street Hospital, United Kingdom. Inclusion criteria were younger than 18 years of age and histologically and molecularly confirmed posterior fossa tumors. Subjects with no available preoperative MR imaging and tumors located primarily in the brain stem were excluded. Imaging characteristics of the tumors were evaluated following a predesigned, step-by-step flow chart. Agreement between readers was tested with the Cohen κ, and each diagnosis was analyzed for accuracy.RESULTS:A total of 148 cases were included, with a median age of 3.4 years (interquartile range, 2.1–6.1 years), and a male/female ratio of 1.24. The predesigned flow chart facilitated identification of pilocytic astrocytoma, ependymoma, and medulloblastoma sonic hedgehog tumors with high sensitivity and specificity. On the basis of the results, the flow chart was adjusted so that it would also be able to better discriminate atypical teratoid/rhabdoid tumors and medulloblastoma groups 3 or 4 (sensitivity = 75%–79%; specificity = 92%–99%). Moreover, our adjusted flow chart was useful in ruling out ependymoma, pilocytic astrocytomas, and medulloblastoma sonic hedgehog tumors.CONCLUSIONS:The modified flow chart offers a structured tool to aid in the adjunct diagnosis of pediatric posterior fossa tumors. Our results also establish a useful starting point for prospective clinical studies and for the development of automated algorithms, which may provide precise and adequate diagnostic tools for these tumors in clinical practice.

In the past 10 years, there has been an exponential increase in knowledge of the molecular characteristics of pediatric brain tumors, which was only partially incorporated in the 2016 World Health Organization Classification of Tumors of the Central Nervous System.1 The main update in the 2016 Classification was the introduction of the molecular profile of a tumor as an important factor for predicting different biologic behaviors of entities which, on histology, look very similar or even indistinguishable.2 A typical example is the 4 main groups of medulloblastoma: wingless (WNT), sonic hedgehog (SHH) with or without the p53 mutation, group 3, and group 4. Although they may appear similar on microscopy, these categories have distinct molecular profiles, epidemiology, prognosis, and embryologic origin.3Subsequent to the publication of the 2016 World Health Organization Classification, further studies have identified even more molecular subgroups of medulloblastoma with possible prognostic implications4 and also at least 3 new molecular subgroups of atypical teratoid/rhabdoid tumor (AT/RT)5 and several subgroups of ependymoma.6 MR imaging shows promise as a technique for differentiating histologic tumors and their molecular subgroups. This capability relies on not only various imaging characteristics but also the location and spatial extension of the tumor, evident on MR imaging, which can be traced to the embryologic origin of the neoplastic cells.5,7-10One approach to the challenge of identifying imaging characteristics of different tumors in children is to use artificial intelligence. Yet despite this exciting innovation, correctly identifying the location of the mass and its possible use as an element for differential diagnosis still requires the expertise of an experienced radiologist. Previously, D''Arco et al11 proposed a flow chart (Fig 1) for the differential diagnosis of posterior fossa tumors in children based on epidemiologic, imaging signal, and location characteristics of the neoplasm. The aims of the current study were the following: 1) to validate, in a retrospective, large cohort of posterior fossa tumors from 2 separate pediatric tertiary centers, the diagnostic accuracy of that flow chart, which visually represents the neuroadiologist''s mental process in making a diagnosis of posterior fossa tumors in children, 2) to describe particular types of posterior fossa lesions that are not correctly diagnosed by the initial flow chart, and 3) to provide an improved, clinically accessible flow chart based on the results.Open in a separate windowFIG 1.Predesigned radiologic flow chart created according to the literature before diagnostic accuracy analysis. The asterisk indicates brain stem tumors excluded from the analysis. Double asterisks indicate relative to gray matter. Modified with permission from D''Arco et al.11  相似文献   
89.
Necrotizing sarcoid granulomatosis (NSG) is a rare entity mainly characterized by a prominent granulomatous vasculitis affecting middle-aged or old individuals and with a favorable prognosis. Although many believe it is a variant of sarcoidosis, the proper classification is still a matter of debate as some of its features are found in sarcoidosis but also in Churg-Strauss syndrome, Wegener's disease and hypersensitivity pneumonitis. In this paper, we described for the first time a case of NSG in a family with several cases of sarcoidosis, reinforcing the relationship between NSG and sarcoidosis. Additional interesting findings were the young age of the patient (15 years old), the symptoms limited to the respiratory tract (uncommon when NSG affects youngsters) and the increase in serologic markers of autoimmune disease. Though complete criteria for autoimmune disease were not present, systemic lupus erythematosus and Sjogren's syndrome are possible candidates. As sarcoidosis is described to be associated with several autoimmune diseases, this finding is an additional suggestion of the relationship between both entities.  相似文献   
90.
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