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   9907篇
  免费   546篇
  国内免费   40篇
耳鼻咽喉   40篇
儿科学   182篇
妇产科学   193篇
基础医学   1324篇
口腔科学   445篇
临床医学   825篇
内科学   2681篇
皮肤病学   255篇
神经病学   998篇
特种医学   299篇
外科学   1200篇
综合类   27篇
一般理论   2篇
预防医学   463篇
眼科学   131篇
药学   570篇
中国医学   27篇
肿瘤学   831篇
  2024年   8篇
  2023年   73篇
  2022年   153篇
  2021年   293篇
  2020年   159篇
  2019年   232篇
  2018年   273篇
  2017年   219篇
  2016年   223篇
  2015年   278篇
  2014年   387篇
  2013年   482篇
  2012年   779篇
  2011年   795篇
  2010年   416篇
  2009年   374篇
  2008年   664篇
  2007年   680篇
  2006年   594篇
  2005年   647篇
  2004年   557篇
  2003年   500篇
  2002年   479篇
  2001年   105篇
  2000年   88篇
  1999年   93篇
  1998年   110篇
  1997年   76篇
  1996年   74篇
  1995年   68篇
  1994年   61篇
  1993年   44篇
  1992年   53篇
  1991年   50篇
  1990年   50篇
  1989年   46篇
  1988年   33篇
  1987年   37篇
  1986年   38篇
  1985年   24篇
  1984年   25篇
  1983年   26篇
  1982年   18篇
  1981年   8篇
  1980年   19篇
  1979年   9篇
  1976年   9篇
  1974年   8篇
  1970年   6篇
  1968年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Twenty patients with AIDS who had intracranial lesions underwent both brain biopsy and cerebro-spinal fluid (CSF) examination to compare histological diagnosis with the polymerase chain reaction (CSF-PCR) for the identification of infectious agents. CSF-PCR was performed for herpes simplex virus, varicella zoster virus, cytomegalovirus (CMV), JC virus (JCV), Epstein-Barr virus (EBV), Toxoplasma gondii and Mycobacterium tuberculosis. A definitive diagnosis was obtained by brain biopsy in 14 patients (2 with astrocytoma, 12 with brain infection). CSF-PCR was positive for EBV DNA in 3 of 3 cases of primary cerebral lymphoma, positive for JCV DNA in 6 of 7 biopsy-proven (and one autopsy-proven) cases of progressive multifocal leukoencephalopathy (PML). CSF-PCR was positive for CMV DNA in one biopsy-proven and one autopsy-proven case of CMV encephalitis (the former also had PML) and positive for M. tuberculosis DNA in one case of tuberculous encephalitis. None of the five toxoplasmic encephalitis cases (one definite, four presumptive) were T. gondii DNA positive. There was close correlation between histology and CSF-PCR for CMV encephalitis, PML and PCL. Antitoxoplasma therapy affected the sensitivity of both histological and CSF-PCR methods. Received: 8 November 1995 Received in revised form: 9 July 1996 Accepted: 19 July 1996  相似文献   
22.
Laryngotracheoesophageal cleft is an uncommon disease that is difficult to diagnose and treat. Repair of the cleft depends on length and localization of the defect as well as the associated anomalies. A successful repair of a type II cleft is reported in this paper. An anterior split of the larynx and trachea was used and provided excellent exposure and safe repair without injury to the neurovascular structures. This is the best approach and should be used to correct all type II defects.  相似文献   
23.
Summary Neo-vascularization and endothelial hyperplasia have been shown to be very active in malignant gliomas. In this contribution the vascularization of the cortex infiltrated by malignant gliomas is morphometrically studied and the endothelial proliferations are immunohistochemically investigated and reconstructed by a three-dimensional computer-assisted procedure. Vessel density increases after tumor infiltration in some cases only. The diameter of vessels increases and so does the number of nuclei/vessel after the complete invasion of the cortex when vascular glomeruli develop. In completely infiltrated cortex with development of glomeruli and circumscribed necroses, vessel density is very low. No neoformation of vessels takes place before the complete infiltration of the cortex by the tumor. The hyperplastic formations, usually arranged parallel to the deep or outer cortical layers, take origin from the radially penetrating vessels from the meninges and their lateral branching. The hyperplasia deforms the vascular network, making it often inadequate to supply tumor cells. Immunohistochemically, the cells composing the hyperplastic structures are variably positive for factor VIII/RAg and, at a lesser extent, for -smooth muscle actin. The poorness of the vascular network in many instances of completely infiltrated cortex is responsible for the development of circumscribed necroses.Supported by Grant 87.01446.44 CNR, Rome and by A. I. R. C., Milan. Presented in part at the 63rd Annual Meeting of the American Association of Neuropathologists, Seattle, Washington, June 11–14, 1987  相似文献   
24.
Summary The pharmacokinetics of the anticancer agent p-(3,3-dimethyl-1-triazeno) benzoic acid (pCOOH-DMT), a drug now in phase I clinical trial in Europe, was investigated in C57 Bl female mice with M5076 reticulum-cell sarcoma that were treated i.v. with 200 mg/kg pCOOH-DMT. The drug disappeared from plasma with a terminal half-life of about 2.5 h. Plasma clearance was approximately 6 ml/min per kg. Distribution studies showed some differences in drug levels in different tissues. The highest levels were found in the tumor, liver, kidney and lung; lower levels were found in the spleen and gut, and the lowest, in the brain. The N-desmethyl derivative of pCOOH-DMT was not detectable in plasma or tissues of mice treated with the drug. Therefore, the previous evidence of low N-demethylation of pCOOH-DMT was confirmed. pCOOH-DMT glucuronide was identified by mass spectrometry and quantified by high-performance liquid chromatography (HPLC) in plasma, tissues and urine samples. pCOOH-DMT glucuronide appears to be the major urinary metabolite of pCOOH-DMT in mice. Another metabolite identified by mass spectrometry and quantified by HPLC in some tissues and urine was pCOOH-DMT glycinate.Abbreviations DTIlC 5-(3,3-dimethyl-l-triazeno)imidazole-4-carboxamide - pCOOH-DMT p-(3,3-dimethyl-l-triazeno)benzoic acid - pCOOH-MMT p-(3-methyl-l-triazeno)benzoic acid - pCONH2-DMT p-(3,3-dimethyl-l-triazeno)carboxamide - BSTFA N,O-bis(trimethylsilyl)trifluoroacetamide - TMCS trimethylchlorosilane - TLC thin-layer chromatography - FAB fast atom bombardment - EI electron impact - M5 M5076 reticulum-cell sarcoma - t1/2 beta-half-life - C0 concentration time 0 - AUC area under the concentration vs time curve - Cl total clearance - V volume of distribution  相似文献   
25.
The traditional algorithms (Marinelli-Quimby and MIRD) used for the absorbed dose calculation in radionuclide therapy generally assume that the mass of the target organs does not change with time. In radioiodine therapy for Graves' disease this approximation may not be valid. In this paper a mathematical model of thyroid mass reduction during the clearance phase (30-35 days) after 131I administration to patients with Graves' disease is presented. A new algorithm for the absorbed dose calculation is derived, taking into account the reduction of the mass of the gland resulting from the 131I therapy. It is demonstrated that thyroid mass reduction has a considerable effect on the calculated radiation dose. Either the model of the thyroid mass reduction or the new equation for the absorbed dose calculation depend on a parameter k for each patient. This parameter can be calculated after the administration of a diagnostic amount of radioiodine activity (0.37-1.85 MBq). Thus, thyroid absorbed dose and thyroid mass reduction during the first month after therapy can be predicted before therapy administration. The absorbed dose values calculated by the new algorithm are compared to those calculated by the traditional Marinelli-Quimby and MIRD algorithms.  相似文献   
26.
Increased urinary excretion of urinary trypsin inhibitor (UTI) has been reported in various inflammatory conditions and in Alzheimer's subjects, but its diagnostic potential remains to be elucidated. A reliable and specific enzyme-linked immunosorbent assay (ELISA) test for the determination of the UTI in human urine was developed. This assay was performed using 96-well microtiter plates. The plate surface is coated with an anti-UTI polyclonal antibody, the urine sample was added in a dilution range, and the detection was achieved using the enzyme-conjugated antibody. The assay was quantified by the build-up of colored product upon the addition of the substrate. Recoveries were 93%, and the intra- and inter-assay CVs were 4.25% and 21%, respectively. The ELISA showed parallelism of standard and urine samples and no significant interference by the biological matrix. The usefulness of the assay has been demonstrated by applying it to urine samples from Alzheimer's disease patients, and comparing with negative controls. UTI urinary levels are significantly increased in Alzheimer's subjects.  相似文献   
27.
28.
In 239 torquetenovirus-positive people, multiple-genogroup infections were common and associated with higher viral loads than would be expected from simple additive effects. The latter observation was restricted to the infections which included both genogroups 1 and 3, pointing to the possible existence of some kind of infection facilitation between these genogroups.  相似文献   
29.
Neoplastic cells generally present profound changes in glucose metabolism. The mechanisms underlying such process are numerous and all may involve altered cellular hormonal responses. Here we report the first evidence that cellular location of phosphofructokinase activity in human breast cancer tissues is different from the one observed in control tissues and that this phenomenon may be involved in the increased glycolytic flux observed in those cells. Through co-sedimentation techniques, we observed that 60% of phosphofructokinase activity in neoplastic tissues is located in an actin-enriched fraction, against 36% in control tissues. Additionally, metastatic tumor tissues presented a two fold increase in this particulate activity when compared to non-metastatic tumor samples. We propose that the alteration in cellular distribution of phosphofructokinase activity in human breast cancer tissues is a mechanism associated to the process of cell transformation and may be a consequence of the altered hormonal milieu observed in several types of cancer.  相似文献   
30.
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