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   1694篇
  免费   117篇
  国内免费   9篇
耳鼻咽喉   10篇
儿科学   24篇
妇产科学   49篇
基础医学   217篇
口腔科学   9篇
临床医学   158篇
内科学   393篇
皮肤病学   18篇
神经病学   309篇
特种医学   25篇
外科学   168篇
综合类   5篇
一般理论   1篇
预防医学   116篇
眼科学   34篇
药学   81篇
中国医学   3篇
肿瘤学   200篇
  2022年   20篇
  2021年   45篇
  2020年   13篇
  2019年   23篇
  2018年   40篇
  2017年   31篇
  2016年   29篇
  2015年   37篇
  2014年   53篇
  2013年   57篇
  2012年   83篇
  2011年   112篇
  2010年   51篇
  2009年   66篇
  2008年   89篇
  2007年   92篇
  2006年   90篇
  2005年   70篇
  2004年   57篇
  2003年   77篇
  2002年   71篇
  2001年   36篇
  2000年   22篇
  1999年   34篇
  1998年   15篇
  1997年   15篇
  1996年   13篇
  1994年   15篇
  1993年   18篇
  1992年   23篇
  1991年   26篇
  1990年   29篇
  1989年   21篇
  1988年   22篇
  1987年   28篇
  1986年   24篇
  1985年   18篇
  1984年   13篇
  1983年   18篇
  1981年   12篇
  1979年   17篇
  1978年   12篇
  1976年   17篇
  1975年   11篇
  1974年   13篇
  1973年   11篇
  1972年   12篇
  1971年   11篇
  1970年   13篇
  1969年   16篇
排序方式: 共有1820条查询结果,搜索用时 15 毫秒
1.
2.
Several neurodegenerative diseases, including motor neuron disease (MND), are characterized by formation of abnormal cytoskeleton-derived inclusions which contain ubiquitin (Ubq). We have studied the distribution of Ubq in 26 cases of MND with light and electron microscopic immunocytochemistry. Ubiquitin-positive inclusions were found in neurons of anterior horns in most cases of amyotrophic lateral sclerosis (ALS) but were not present in other forms of MND. Ubiquitin immunoreactivity was observed in 10-15 nm intraneuronal filaments, which were not stained by antibodies to neurofilaments, and on dense bodies of dystrophic neurites throughout the neuropil of anterior horns and pyramidal tracts. Data analysis showed a trend toward lower percentage of Ubq-positive neurons in cases with longer duration of illness or lower number of neurons. A high percentage of Ubq-positive inclusions occurred in cases with an aggressive clinical course, suggesting that ubiquitination takes place at early stages of the disease.  相似文献   
3.
Brain-tumor cell kinetics correlated with survival   总被引:1,自引:0,他引:1  
In a review of 38 glioblastoma patients for whom fresh tissue kinetic data were available before any therapy was instituted, no correlation between the labeling index and survival time could be statistically determined. This relationship seems entirely consistent with the published theoretical determinants of tumor behavior: that is, altered ability for growth arrest and differentiation, constantly evolving mutant sublines, genetic instability, and an ever-changing metabolic and vascular environment.  相似文献   
4.
Multiple sclerosis and the workplace: report of an industry-based cluster   总被引:2,自引:0,他引:2  
E C Stein  R B Schiffer  W J Hall  N Young 《Neurology》1987,37(10):1672-1677
Eleven cases of MS occurred within a 10-year period in a zinc-related manufacturing plant. The observed disease incidence was greater than expected from population data, using multiple approaches to statistical analysis (p less than or equal to 0.01). A case-control study, performed to examine several zinc parameters in blood, failed to indicate specific abnormalities among the MS patients, but all subjects (both MS and controls) working in the plant demonstrated higher serum zinc levels than all subjects (MS and controls) not working there.  相似文献   
5.
Editorial comment   总被引:1,自引:0,他引:1  
  相似文献   
6.
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   
7.
Multiple sclerosis. The problem of incorrect diagnosis   总被引:1,自引:0,他引:1  
Various neurologic disorders may be diagnosed incorrectly as multiple sclerosis (MS) since there is no test that is entirely specific for the disease. We report ten patients who met clinical criteria for probable or definite MS and who were given incorrect diagnoses. All of the patients were subsequently shown to have alternative diagnoses, three of which were directly treatable. From these illustrative cases, five characteristics were identified that alerted us to the possibility of an alternative diagnosis. We have called these characteristics "red flags," and suggest that they may be useful as features casting doubt on the diagnosis of MS if used judiciously in conjunction with clinical diagnostic criteria.  相似文献   
8.
BACKGROUND: Glatiramer acetate (Copaxone) therapy reduces clinical disease activity in relapsing-remitting multiple sclerosis (MS). OBJECTIVE: To study the effect of glatiramer therapy on neuropsychologic function as part of a randomized, placebo-controlled, multicenter trial. METHODS: Two hundred forty-eight patients with relapsing-remitting MS and mild to moderate disability (Expanded Disability Status Scale score, <5.0) were tested before and 12 and 24 months after randomization to administration of glatiramer acetate, 20 mg/d, or matching placebo. Neuropsychologic tests examined 5 cognitive domains most often disrupted in patients with MS: sustained attention, perceptual processing, verbal and visuospatial memory, and semantic retrieval. RESULTS: Baseline neuropsychologic test performance was similar in both treatment groups and was within normal range, except for impaired semantic retrieval. Mean neuropsychologic test scores were higher at 12 and 24 months than at baseline, and no differences were detected between treatment groups over time. No significant interactions were detected between treatment and either time or baseline impairment. CONCLUSIONS: Our 2-year longitudinal study showed no effect of glatiramer therapy on cognitive function in relapsing-remitting MS. Although it is possible that glatiramer therapy has no effect on cognitive function, the lack of measurable decline in cognitive function in both patient groups for 2 years limits the opportunity for glatiramer to demonstrate a therapeutic effect by minimizing such decline. Emerging treatments for MS should continue to be examined for their effect on cognitive impairment because it can be a critical determinant of disability. A greater understanding of the natural history of cognitive decline in MS is essential for a rational design of these drug trials.  相似文献   
9.
Summary Experimental cerebral tumors have been induced by transplacental ENU. The morphologic study of the brains of treated rats revealed that cellular hyperplasias appear at the 30th day of extrauterine life in the paraventricular white matter, i.e., before the already known early neoplastic proliferations. Cytofluorimetric investigations failed to demonstrate differences between treated and control rats during the 1st month. On the contrary, adenylate cyclase activity is very high in that period. The duration of the latency period is discussed.This research was supported by Grants No. 79.00678.96 and No. 79.00664.96 of Progetto Finalizzato Control of Neoplastic Growth, Consiglio Nazionale delle Ricerche (C.N.R.), Rome  相似文献   
10.
Summary In a case of congenital paramyotonia a muscle biopsy was performed and studied morphologically, histochemically and ultrastructurally. A clearcut pattern of changes has been observed with ATPase and oxidative enzymes. On electron microscopy special changes known as tubular aggregates were found. The relationship between the two findings, as well as the significance of such alterations in the range of periodic paralyses and myotonic phenomena, are discussed.
Zusammenfassung Bei einem Fall von kongenitaler Paramyotonie wurde eine Muskelbiopsie lichtmikroskopisch, histochemisch und elektronenoptisch untersucht. Typische Veränderungen ergaben sich in der ATPase-Färbung und in bezug auf oxydative Enzyme. Bei der elektronenoptischen Untersuchung wurden sogenannte tubuläre Aggregate festgestellt. Es wird die Beziehung der zwei Gruppen von Veränderungen zueinander diskutiert sowie auch die Bedeutung derselben im Rahmen der periodischen Lähmungen und der myotonen Phänomene.
  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