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   4514篇
  免费   311篇
  国内免费   6篇
耳鼻咽喉   66篇
儿科学   180篇
妇产科学   202篇
基础医学   693篇
口腔科学   70篇
临床医学   432篇
内科学   934篇
皮肤病学   141篇
神经病学   422篇
特种医学   243篇
外科学   558篇
综合类   31篇
预防医学   201篇
眼科学   83篇
药学   316篇
中国医学   1篇
肿瘤学   258篇
  2022年   30篇
  2021年   41篇
  2020年   35篇
  2019年   53篇
  2018年   56篇
  2017年   61篇
  2016年   72篇
  2015年   79篇
  2014年   94篇
  2013年   128篇
  2012年   152篇
  2011年   185篇
  2010年   152篇
  2009年   137篇
  2008年   187篇
  2007年   201篇
  2006年   200篇
  2005年   170篇
  2004年   178篇
  2003年   146篇
  2002年   159篇
  2001年   149篇
  2000年   183篇
  1999年   135篇
  1998年   67篇
  1997年   89篇
  1996年   74篇
  1995年   73篇
  1994年   48篇
  1993年   74篇
  1992年   108篇
  1991年   100篇
  1990年   100篇
  1989年   92篇
  1988年   75篇
  1987年   58篇
  1986年   64篇
  1985年   75篇
  1984年   41篇
  1983年   61篇
  1982年   28篇
  1981年   44篇
  1980年   29篇
  1979年   44篇
  1978年   33篇
  1977年   34篇
  1976年   33篇
  1975年   27篇
  1973年   30篇
  1972年   30篇
排序方式: 共有4831条查询结果,搜索用时 15 毫秒
81.
Computed tomography can be very useful in the assessment of mediastinal masses in children. In this case, it provided for the specific diagnosis of a pericardial cyst in a young child, obviating the need for invasive evaluation or surgery.  相似文献   
82.
Summary Twenty-nine patients with advanced Parkinson's disease were treated with subcutaneous lisuride infusion in addition to a basic therapy consisting of levodopa + PDI in all, and deprenyl in some patients. At the time of the report, 13 patients are still receiving lisuride infusion after 5–36 months, while 16 have dropped out after 0.5–30 months one because of psychosis, three because of insufficient efficacy, three due to death unrelated to treatment, three because of difficulties in handling the pump as outpatients, and six for other reasons. Off-periods and parkinsonian disability in off and in on were reduced significantly. These improvements remained constant throughout the observation period. Once the optimal dose regimen is established, only minor adjustments of the doses of lisuride and levodopa are required in the individual case.  相似文献   
83.
From 1987 through 1990, the Health Care Financing Administration (HCFA) evaluated variations in the mortality rates experienced by patients admitted to hospitals participating in the Medicare program. This study was conducted to evaluate the adequacy of the model used for that purpose. Detailed clinical data were gathered on 42,773 patients admitted to 84 statistically selected hospitals. The effect of risk adjustment using the HCFA model, which is based on claims data, was compared to a risk-adjustment model based on physiologic and clinical data. Models that include claims data were markedly superior to those containing only demographic characteristics in predicting the probability of patient death, and the addition of clinical data resulted in further improvement. The correlation of ranks of hospitals based on a model that uses only the claims data and on one that uses, in addition, clinical data, was .91. As a screen for the identification of "high (mortality) outlier" hospitals, the claims model had moderate sensitivity (81 percent) and specificity (79 percent), a high negative predictive value (90 percent), and a low positive predictive value (64 percent) when compared to the clinical model. The two mortality models gave similar results when used to determine which structural characteristics of hospitals were related to mortality rates: hospitals with a higher proportion of registered nurses or board-certified physician specialists, or with a greater level of access to high-technology equipment had lower risk-adjusted mortality rates. These data suggest that the current claims-based risk-adjustment procedure may satisfactorily be used to characterize variations in mortality rates associated with hospitalization. The procedure could also be used as a basis for further epidemiological analyses of factors that affect the probability of patient death. However, it does not positively identify outlier hospitals as providers of problematic care.  相似文献   
84.
85.
The distribution of the calcium-binding protein calretinin was studied in peripheral and central parts of the main olfactory system (MOS) and the vomeronasal system (VNS) of adult tree shrew Tupaia belangeri. The calretinin immunoreaction was carried out with a peroxidase-coupled polyclonal antibody. In the VNS, complete labeling of all receptor cells and vomeronasal nerve fibers was observed, whereas only a subset of the somata and dendrites of receptor cells and of the olfactory nerve fibers of the MOS was immunoreactive. From the immunoreactive dendritic clubs of vomeronasal receptor cells, calretinin-labeled structures, presumably clumps of microvilli, arose that terminated within immunopositive portions of the mucus. In the main olfactory bulb, the neuropil of some of the glomeruli was immunoreactive. All periglomerular and many mitral cells were labeled. The external plexiform layer was subdivided into a faintly immunoreactive superficial half and a strongly immunoreactive deep half. Immunoreactive basal dendrites of mitral cells could be followed into either the deep half or the superficial half. In the laminated internal granular layer, a subset of immunopositive granule cells extended dendrites into the external plexiform layer. Mitral cells and granule cells with dendrites ascending to different levels of the external plexiform layer may represent functional subclasses. In the accessory olfactory bulb, all vomeronasal nerve fibers, glomeruli, and mitral/tufted cells were labeled, whereas immunoreactive periglomerular cells and internal granule cells were only scattered. In Tupaia, calretinin immunoreactivity is a more general property of the primary projecting neurons of the VNS than of the MOS and possibly indicates the involvement of calretinin in the perception of certain of the olfactory qualities.  相似文献   
86.
BACKGROUND: The time required for incisional healing accounts for the majority of postoperative pain and convalescence. Impaired healing prolongs the process further. If a method for accelerating acute incisional wound healing could be developed, patients would benefit from decreased wound failure and an earlier return to their premorbid condition. MATERIALS AND METHODS: In a rat dermal model, cytokine or vehicle infiltration prior to incision was performed using a single dose or four daily doses preincision. Planned incision sites were primed with the proinflammatory cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) or platelet-derived growth factor BB (PDGF-BB) in an effort to activate the inflammatory phase of healing prior to wounding. At the time of incision closure, one half of the incisions were treated with transforming growth factor beta(2) (TGF-beta(2)). Incisional sites were biopsied and stained with hematoxylin and eosin and immunohistochemistry for inflammatory cells and fibroblast populations and breaking strength was measured. RESULTS: Priming skin with GM-CSF or PDGF-BB mimicked the early inflammatory phase of wound healing. Macrophage staining (EB1) and fibroblast staining (vimentin) were significantly increased prior to incision. Inflammatory priming as well as priming coupled with TGF-beta(2) at the time of the incision closure synergistically improved breaking strength. CONCLUSION: This study demonstrates that sequential therapy consisting of priming of tissue with an inflammatory cytokine followed by application of a proliferative cytokine at the time of incision closure nearly doubles the breaking strength of an acute wound. By manipulating the inflammatory and early proliferative phases of wound healing with tissue growth factors, it may be possible to accelerate acute wound repair and shift the wound healing trajectory to the left.  相似文献   
87.
PURPOSE: To evaluate the toxicity, antileukemic activity, and pharmacology of raltitrexed administered weekly for 3 weeks to patients with refractory or recurrent leukemia. EXPERIMENTAL DESIGN: Raltitrexed was administered as a 15-minute infusion for 3 consecutive weeks every 5 weeks, at doses ranging from 1.3 to 2.8 mg/m(2). The first course was used to determine the dose-limiting toxicities and maximum tolerated dose. Correlative studies included an assessment of raltitrexed pharmacokinetics and measurement of plasma 2'-deoxyuridine concentrations, a surrogate measure of thymidylate synthase inhibition. RESULTS: Twenty-one children (18 evaluable) with refractory leukemia received 25 courses of raltitrexed. The dose-limiting toxicity was reversible elevation in liver transaminases at the 2.8-mg/m(2) dose level and the maximum tolerated dose was 2.1 mg/m(2) per dose. Pharmacokinetics were best characterized by a two-compartment model with a clearance of 139 mL/min/m(2) (8.3 L/h/m(2)), a 2.4-L volume of distribution, an initial half-life (t(1/2alpha)) of 6 minutes, and a terminal half-life (t(1/2beta)) of 45 minutes. There were three objective responses. CONCLUSIONS: Raltitrexed was well tolerated when administered as a single agent to children with recurrent or refractory leukemia. We observed preliminary evidence of antileukemia activity using this weekly dosing schedule and these observations support further evaluation of raltitrexed in this population.  相似文献   
88.
PURPOSE: To determine the maximum-tolerated dose (MTD), toxicities, and clinical effect of tipifarnib, a farnesyltransferase (FTase) inhibitor, in patients with recurrent malignant glioma taking enzyme-inducing antiepileptic drugs (EIAEDs). This study compares the pharmacokinetics and pharmacodynamics of tipifarnib at MTD in patients on and off EIAEDs. PATIENTS AND METHODS: Recurrent malignant glioma patients were treated with tipifarnib using an interpatient dose-escalation scheme. Pharmacokinetics and pharmacodynamics were assessed. RESULTS: Twenty-three assessable patients taking EIAEDs received tipifarnib in escalating doses from 300 to 700 mg bid for 21 of 28 days. The dose-limiting toxicity was rash, and the MTD was 600 mg bid. There were significant differences in pharmacokinetic parameters at 300 mg bid between patients on and not on EIAEDs. When patients on EIAEDs and not on EIAEDs were treated at MTD (600 and 300 mg bid, respectively), the area under the plasma concentration-time curve (AUC)(0-12 hours) was approximately two-fold lower in patients on EIAEDs. Farnesyltransferase inhibition was noted at all tipifarnib dose levels, as measured in peripheral-blood mononuclear cells (PBMC). CONCLUSION: Toxicities and pharmacokinetics differ significantly when comparing patients on or off EIAEDs. EIAEDs significantly decreased the maximum concentration, AUC(0-12 hours), and predose trough concentrations of tipifarnib. Even in the presence of EIAEDs, the levels of tipifarnib were still sufficient to potently inhibit FTase activity in patient PBMCs. The relevance of these important findings to clinical activity will be determined in ongoing studies with larger numbers of patients.  相似文献   
89.
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