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   1695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   169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   41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1821条查询结果,搜索用时 15 毫秒
21.
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   
22.
Imatinib (imatinib mesylate, Gleevec? [formerly known as STI571], Novartis Pharmaceuticals, Basel, Switzerland) is a protein tyrosine kinase inhibitor that is approved by the US Food and Drug Administration for patients with all phases of chronic myeloid leukemia (CML). Imatinib is remarkably effective as treatment for CML in the chronic phase (at a dosage of 400 mg/d) and the accelerated phase (at 600 mg/d). At this time, it remains to be seen whether the chronic phase of CML can be extended sufficiently in some patients so that they are functionally "cured," and also whether the increased rate of major molecular response induced by doses of imatinib higher than 400 mg/d will further improve overall survival of patients with CML in the chronic phase. The value of molecular monitoring of response in patients with CML in the chronic phase is examined. Although imatinib 800 mg/d can induce dramatic responses in patients with myeloid blast crisis, lymphoid blast crisis, and Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL), the responses are usually incomplete and of short duration. We discuss the role of imatinib in relation to allogeneic stem cell transplantation (particularly in younger patients), recognizing that the data upon which any decisions can be made are relatively immature. Finally, recent data on new tyrosine kinase inhibitors capable of overcoming primary or acquired resistance to imatinib are reviewed.  相似文献   
23.
Taking advantage of the recently demonstrated presence of N-aminopeptidasesand the serine protease dipeptidyi aminopeptidase IV (DPP IV)at the surface of human myeloblastic HL-60 cells, the regulationof these protease activities in HL-60 cell differentiation hasbeen assessed using combined spectrophotometric and flow cytometricassays. Addition of human recombinant granulocyte macrophagecolony stimulating factor (rHu-GM-CSF) to HL-60 cells to inducedifferentiation into macrophages led to a time and dose-dependentincrease in both cell surface N-aminopeptidase and DPP IV activities.Protease up-regulation was due to an enhancement in cell surfaceprotease number, associated with a slight rise in apparent affinitiesof the enzymes for their substrates. In contrast, in HL-60 cellsinduced to differentiate into neutrophils in the presenceofretinoic acid, expression of cell surface N-amlnopeptidaseswas almost completely abolished in a time-and dose-dependentfashion, and this down-regulation was accompanied by a weakbut significant decrease in affinity. However, no noticeabledifference was seen in serine DPP IV expression between retinoicacid-treated and untreated HL-60 cells. Retinoic acid treatmentalso reduced soluble protease activity in vitro indicating thatdown-regulation of membrane aminopeptldases was not due to theirproteolytic clip. No modulation in the activity of any of theenzymes tested was seen with human recombinant tumor necrosisfactor- or retinol which do not induce HL-60 cell differentiation.The up-regulation of cell surface protease expression in HL-60cells differentiated into macrophages was similar to that observedin monocytes isolated from peripheral blood: both DPP IV andN-aminopeptidase activities strictly increased on cells thatundergo macrophage maturation (up to 5-fold) and independentlyof the nature of the differentiation inducer. Thus, the distinctivepatterns of N-aminopeptidase and DPP IV expression that areseen in differentiating neutrophils and macrophages appear tobe relatedto differences in stage of myeloid maturation. Becausecell surface proteases are crucially involved in leukocyte functions,the data presented suggest that alterations in cell surfaceprotease expression are associated with events controlling thedifferentiation of immature cells.  相似文献   
24.
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   
25.
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   
26.
PURPOSE: Imatinib mesylate is a tyrosine kinase inhibitor with high affinity for the BCR-ABL fusion protein expressed by the hematopoietic cells in chronic myelogenous leukemia (CML). Some patients with chronic-phase or accelerated-phase CML either relapse after an initial response or are refractory to imatinib, prompting us to evaluate the efficacy of dose increase in such patients. EXPERIMENTAL DESIGN: Twelve chronic-phase patients initially receiving 400 mg/day and 4 patients with accelerated phase initially receiving either 400 mg/day (two patients) or 600 mg/day (two patients) had their dose increased (14 to 800 mg/day and 2 to 600 mg/day) because of progressive disease (usually clonal evolution) or inadequate cytogenetic response after at least 1 year of therapy. RESULTS: Six patients had major cytogenetic responses after dose increase (3 complete and 3 partial). Two others had minor cytogenetic responses. Two patients with clonal evolution transiently lost the additional clonal aberrations. Almost all of the responses occurred within 6 months, and were typically 3-6 months in duration. However, 3 patients have continuing major cytogenetic responses of >18 months duration. Dose increase was well tolerated, with thrombocytopenia, mild leukopenia, and exacerbation of prior edema being the most common adverse events. CONCLUSIONS: Although increasing the dose of imatinib can benefit a subgroup of patients with CML with either an inadequate cytogenetic response or disease progression, our results suggest the majority will not have a sustained meaningful response, and that other options, such as allogeneic stem cell transplant or investigational therapies, also need to be considered at the time of dose increase.  相似文献   
27.
A 3-dose (0, 1, and 6 months) intramuscular (3-IM) priming series of a human dose (HuAVA) and dilutions of up to 1:10 of anthrax vaccine adsorbed (AVA) provided statistically significant levels of protection (60 to 100%) against inhalation anthrax for up to 4 years in rhesus macaques. Serum anti-protective antigen (anti-PA) IgG and lethal toxin neutralization activity (TNA) were detectable following a single injection of HuAVA or 1:5 AVA or following two injections of diluted vaccine (1:10, 1:20, or 1:40 AVA). Anti-PA and TNA were highly correlated (overall r2 = 0.89 for log10-transformed data). Peak responses were seen at 6.5 months. In general, with the exception of animals receiving 1:40 AVA, serum anti-PA and TNA responses remained significantly above control levels at 28.5 months (the last time point measured for 1:20 AVA), and through 50.5 months for the HuAVA and 1:5 and 1:10 AVA groups (P < 0.05). PA-specific gamma interferon (IFN-γ) and interleukin-4 (IL-4) CD4+ cell frequencies and T cell stimulation indices were sustained through 50.5 months (the last time point measured). PA-specific memory B cell frequencies were highly variable but, in general, were detectable in peripheral blood mononuclear cells (PBMC) by 2 months, were significantly above control levels by 7 months, and remained detectable in the HuAVA and 1:5 and 1:20 AVA groups through 42 months (the last time point measured). HuAVA and diluted AVA elicited a combined Th1/Th2 response and robust immunological priming, with sustained production of high-avidity PA-specific functional antibody, long-term immune cell competence, and immunological memory (30 months for 1:20 AVA and 52 months for 1:10 AVA). Vaccinated animals surviving inhalation anthrax developed high-magnitude anamnestic anti-PA IgG and TNA responses.  相似文献   
28.
Dimethyl sulfoxide (DMSO) is an organic solvent with several biological applications. It is extensively used to dissolve compounds that hardly dissolve in water to detect their genotoxic activity in vitro. In this study DMSO will be tested to determine its genotoxic potential. The effect of DMSO on the frequency of chromosomal aberrations in anaphase as well as DNA fragmentation through the comet assay has been evaluated in the meristematic cells of the root tips of Vicia faba. It has been observed that the frequency of chromosomal aberrations increases when the concentration of DMSO increases, reaching its maximum value with 20% of DMSO and decreasing at 30 and 40% of DMSO, in comparison to this maximum value, but significantly higher than the values observed in the control. Similarly, the percentage of fragmentation and damage index evaluated through the comet assay showed the same behavior; some of the possible mechanisms of action are discussed.  相似文献   
29.
The epidemiological cycle of zoonotic phlebotomine‐borne Leishmania infantum is a complex system in which domestic animals and wildlife interact and participate in its maintenance and transmission. In this study, we combined entomological surveillance, xenomonitoring of L. infantum and identification of host feeding sources of engorged females to investigate the potential contribution of a periurban wildlife park to leishmaniosis in neighbouring residential areas. Overall, 7,309 sand flies were collected in 111 trap‐days during the summers of 2016–2018 in an endemic area in south‐east Spain. Five different sand fly species were captured, with Phlebotomus perniciosus, the main L. infantum vector in this region, representing the most common species. Sand fly distribution was spatially heterogeneous in terms of species, sexes and female physiological stage (unfed, gravid and engorged females) and related to host distribution and management, and environmental features. None of the 602 sand flies analysed for L. infantum infection by kinetoplast real‐time PCR were positive. We used molecular tools to identify the vertebrate hosts of sand flies and identified 17 host species, mainly mammals. Human DNA was not identified in engorged sand flies. This study provides evidence that wildlife parks in south‐east Spain are ideal grounds for sand fly vectors but do not necessarily increase L. infantum infection risk to humans and dogs living in surrounding residential areas. This is probably because vectors feed mostly on non‐L. infantum competent hosts and this should be investigated for a better understanding of the contribution of wildlife parks to the local epidemiology of L. infantum.  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