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   5244篇
  免费   387篇
  国内免费   23篇
耳鼻咽喉   9篇
儿科学   136篇
妇产科学   102篇
基础医学   884篇
口腔科学   97篇
临床医学   490篇
内科学   966篇
皮肤病学   168篇
神经病学   770篇
特种医学   170篇
外科学   506篇
综合类   31篇
一般理论   1篇
预防医学   456篇
眼科学   65篇
药学   326篇
中国医学   13篇
肿瘤学   464篇
  2023年   37篇
  2022年   70篇
  2021年   134篇
  2020年   89篇
  2019年   135篇
  2018年   137篇
  2017年   136篇
  2016年   140篇
  2015年   190篇
  2014年   194篇
  2013年   286篇
  2012年   391篇
  2011年   408篇
  2010年   236篇
  2009年   217篇
  2008年   383篇
  2007年   374篇
  2006年   318篇
  2005年   275篇
  2004年   260篇
  2003年   206篇
  2002年   233篇
  2001年   57篇
  2000年   38篇
  1999年   54篇
  1998年   44篇
  1997年   30篇
  1996年   24篇
  1995年   16篇
  1994年   22篇
  1993年   22篇
  1992年   28篇
  1991年   23篇
  1990年   34篇
  1989年   23篇
  1988年   26篇
  1987年   32篇
  1986年   25篇
  1985年   20篇
  1984年   22篇
  1983年   21篇
  1979年   18篇
  1978年   14篇
  1976年   18篇
  1975年   13篇
  1974年   15篇
  1973年   13篇
  1972年   13篇
  1970年   14篇
  1969年   16篇
排序方式: 共有5654条查询结果,搜索用时 250 毫秒
61.
62.
New data regarding the incidence of oesophageal and other cancers during the period 1985-1990 are reported for all clinics and hospitals in four selected districts of Transkei, Southern Africa i.e Kentani, Butterworth, Lusikisiki and Bizana. Active and passive methods were used to obtain the hospital-based cancer registry data. The mean annual number of cancer cases recorded for the period 1985-1990 was 292. Age-standardized incidence rates (ASIIR, African Standard) for all recorded cancers were 81.4 and 52.6/100,000 for males and females, respectively. Histopathogical examination of 52.6% of recorded tumours revealed that 67.3% were squamous carcinomas, 21.7% adenocarcinomas and the remainder non-epithelial neoplasms. Cancer of the oesophagus (EC) was the most frequently recorded cancer and accounted for 46.5% of the cases with mean ASIR of 46.7 and 19.2/100,000 for males and females, respectively. The male/female ratio was 2:4:1. The highest mean ASIR per annum for OC in males (55.6/100,000) occurred in Kentani and in females (22.3/100,000) in Lusikisiki, whereas the lowest rates in both sexes (37.0 and 11.7/100,000 respectively) occurred in Bizana. Comparison of the OC rates in the four districts of Transkei during 1985-1990 with previously reported trends, confirms a consistently high rate in the south-western district of Kentani during the past 35 years and progressively increasing rates in the north-eastern districts of Bizana and Lusikisiki. These results have profound implications for further epidemiological and aetiological studies on OC in Transkei, but need to be corroborated by data from other sources such as statistics on histologically diagnosed cancer in Transkei by district in the South African National Cancer Registry. The second most frequently recorded cancer among males was liver cancer with a mean annual ASIR of 6.0/100,0000 and a male: female ratio of 3:1. The most frequently recorded cancer with a mean annual AISR of 20.9/100,000 followed by OC (19.2/100,000) and breast cancer (5.8/100,000).  相似文献   
63.
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   
64.
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   
65.
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   
66.
Summary After i.p. injection of 3-14C-antipyrine (10 mole=1.9 mg with 10 Ci per 10 g of body weight) to mice radioactivity was irreversibly bound to liver proteins. The irreversible binding reached maximal values of 0.15 nmole/mg protein in liver microsomes after 30–60 min.During 60 min incubation with liver microsomes of mice and rabbits (phenobarbital pretreated) and a NADPH-regenerating system 3-14C-antipyrine was irreversibly bound to microsomal protein at a rate of 1.5 nmole/mg protein (mouse) and 3 nmole/mg protein (rabbit).In identical incubates with rabbit liver microsomes the 4-hydroxylation of antipyrine was 24 nmole/mg protein in 60 min and formaldehyde production from antipyrine 3 nmole/mg protein in 60 min.In incubates with rabbit liver microsomes the binding rate was 80–90% inhibited by 1mM metyrapone, SKF 525-A and trichloropropene epoxide respectively; 4-hydroxylation was 70–80% inhibited by the same substances. In the presence of 1 mM GSH, cysteine or ethylene diamine binding was 30–40% inhibited, whereas 4-hydroxylation showed no inhibition.Some of the results were presented at the 17th Spring Meeting of the Deutsche Pharmakologische Gesellschaft, Mainz, March 1976  相似文献   
67.
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   
68.
69.
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   
70.
PURPOSE: Bone marrow neoangiogenesis plays an important pathogenetic and possible prognostic role in acute myeloid leukemia (AML). Members of the vascular endothelial growth factor (VEGF) and angiopoietin family represent the most specific inducers of angiogenesis secreted by AML blasts. We therefore correlated expression of angiogenic factors with clinical variables. PATIENTS AND METHODS: We investigated the expression of VEGF-A, VEGF-C, angiopoietin-1 (Ang1), angiopoietin-2 (Ang2), and the receptor Tie2 by quantitative polymerase chain reaction in a cohort of 90 patients younger than 61 years with de novo AML entered into the German AML Süddeutsche H?moblastose Gruppe Hannover 95 trial. Uni- and multivariate analyses were performed using clinical and gene expression variables. RESULTS: Univariate analysis of overall survival indicated the following variables as prognostic factors: good response on a day-15 bone marrow examination after initiation of induction chemotherapy, karyotype, and high Ang2 expression. In multivariate analysis, only bad response and log Ang2 expression remained of statistical significance, with a hazard ratio of 3.51 (95% CI, 1.91 to 6.47) and 0.75 (95% CI, 0.61 to 0.91), respectively. Subgroup analysis suggested that the prognostic impact of Ang2 expression was especially evident in cohorts with low VEGF-C and Ang1 mRNA levels. CONCLUSION: These results show that expression of Ang2 represents an independent prognostic factor in AML. Additional research into interactions of angiogenic cytokines in the pathogenesis of bone marrow angiogenesis in AML is warranted.  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