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   2985篇
  免费   221篇
  国内免费   8篇
耳鼻咽喉   10篇
儿科学   105篇
妇产科学   72篇
基础医学   446篇
口腔科学   13篇
临床医学   395篇
内科学   633篇
皮肤病学   67篇
神经病学   256篇
特种医学   115篇
外国民族医学   9篇
外科学   412篇
综合类   29篇
一般理论   1篇
预防医学   203篇
眼科学   106篇
药学   163篇
中国医学   6篇
肿瘤学   173篇
  2022年   21篇
  2021年   62篇
  2020年   40篇
  2019年   54篇
  2018年   65篇
  2017年   43篇
  2016年   48篇
  2015年   43篇
  2014年   66篇
  2013年   104篇
  2012年   178篇
  2011年   173篇
  2010年   87篇
  2009年   70篇
  2008年   131篇
  2007年   154篇
  2006年   141篇
  2005年   137篇
  2004年   124篇
  2003年   84篇
  2002年   87篇
  2001年   100篇
  2000年   65篇
  1999年   58篇
  1998年   21篇
  1997年   24篇
  1996年   20篇
  1995年   23篇
  1994年   18篇
  1993年   18篇
  1992年   82篇
  1991年   62篇
  1990年   54篇
  1989年   63篇
  1988年   61篇
  1987年   52篇
  1986年   44篇
  1985年   64篇
  1984年   43篇
  1983年   40篇
  1982年   20篇
  1979年   45篇
  1978年   29篇
  1977年   16篇
  1976年   28篇
  1974年   25篇
  1973年   25篇
  1972年   27篇
  1971年   23篇
  1970年   21篇
排序方式: 共有3214条查询结果,搜索用时 15 毫秒
11.
The objective of this article is to summarize the diagnostic criteria recommended by the International Panel on the Diagnosis of Multiple Sclerosis in 2001. The recommendations of another working group, the Consortium of Multiple Sclerosis Centers Consensus Meeting, which met in Vancouver in 2001, concerning the diagnosis and follow-up of patients with multiple sclerosis are also presented in an effort to standardize the protocols for magnetic resonance imaging of these patients.  相似文献   
12.
Image quality and safety of magnetic resonance (MR) imaging were evaluated in vitro and in eight patients with the most commonly employed metallic biliary endoprosthesis. In vitro, the stent produced no tip deflection at 0.6 or 1.5 T. Trace magnetic susceptibility artifact, similar to artifact from a column of air, paralleled the stent. In patients, image degradation was minimal with conventional pulse sequences. Middle-field-strength spin-echo images revealed minimal artifacts indistinguishable from those produced by pneumobilia.  相似文献   
13.
The Symptom Checklist-90-Revised (SCL-90-R) has often been used in studies of alcoholic populations. Based on findings reported in the literature and data gathered on 712 alcoholics in treatment, this paper investigates the general trends in the responses of alcoholics to the SCL-90-R. On global measures as well as on each of the symptom scales, the scores of alcoholic groups reveal a symptomatology two to five times as severe as that observed in the general population. The Psychoticism dimension shows the most marked divergence with the general population. In almost each of the study groups, the Depression Scale registers the highest scores, followed by Obsessive-Compulsive, Interpersonal Sensitivity, and Anxiety.  相似文献   
14.
15.
We have studied the ability of synthetic analogs of lipid A to mimic lipopolysaccharide (LPS) for activation of 70Z/3 pre-B cells (expression of surface Igs) or to antagonize this effect. The results indicate that the presence of glucosamine (mono- or disaccharide) as a 'backbone' for the attachment of fatty acids is not necessary for activation of cells of the B lineage. Phosphate groups are not necessary either. Other structural features such as the configuration of particular asymmetric carbons, and the distance between an anionic group and an N-acyl chain, seem to be much more critical parameters for activation of B cells. Among the synthetic lipids which were unable to activate 70Z/3 cells, one compound, consisting of N,N-acylated and bisphosphorylated 2,3-dideoxy-2,3-diamino-D-glucose, behaved as a specific LPS antagonist and blocked also the activation triggered by the other synthetic inducers. The influence of the synthetic lipids on the entry of mature mouse B lymphocytes into the G1A phase of the cell cycle (cell enlargement) was also investigated. A high correlation was observed between the potency to activate pre-B cells and the ability to induce blast formation in mature B cells.  相似文献   
16.
17.
STUDY OBJECTIVE: To determine, during heparin therapy, the embolic risk associated with acute inferior vena cava thrombosis compared with noncaval thrombosis. DESIGN: Prospective controlled study. SETTING: University-affiliated general hospital. PATIENTS: Of 68 consecutive patients considered, 18 with cavographically proved inferior vena cava thrombosis and 45 with phlebography-proved noncaval proximal thrombosis met all other eligibility criteria and completed the study. INTERVENTIONS: All patients received adjusted continuous IV heparin therapy for ten days. MEASUREMENTS AND RESULTS: All 63 patients underwent systematic baseline and "day 10" perfusion lung scanning and phlebocavography. None suffered pulmonary embolism within the ten days, but 11/63 patients showed thrombus extension on day 10 phlebocavograms. Retrospectively, no significant difference could be found between the groups with and without extension. CONCLUSIONS: (a) The early embolic risk associated with heparin-treated venous thromboses appears low and does not seem to depend on the location (caval or more peripheral) of venous clots. (b) Thrombus extension may occur in spite of apparently "adequate" anticoagulation with heparin.  相似文献   
18.
Summary Genetic analysis of 25 nuclear mutants defective in the chlorophyll-protein complex CP1 was undertaken. The mutants belong to 13 complementation groups scattered throughout the nuclear genome. All these mutants lack the apoprotein of CP1 and, in addition, a specific set of six low molecular weight thylakoid polypeptides. System I particles obtained by treating WT thylakoid membranes with detergent specifically contain those polypeptides which the mutants lack. These observations suggest that a particular sub-structure of the thylakoid membrane associated with the photosystem I activity is missing from all 25 mutants studied, and that this general phenotype can result from mutation at any one of several unlinked Mendelian loci.  相似文献   
19.
Parental origin of de novo MECP2 mutations in Rett syndrome   总被引:6,自引:0,他引:6  
Rett syndrome (RTT) is a neurodevelopmental disorder occurring almost exclusively in females as sporadic cases. Recently, DNA mutations in the MECP2 gene have been detected in approximately 70% of patients with RTT. To explain the sex-limited expression of RTT, it has been suggested that de novo X-linked mutations occur exclusively in male germ cells resulting therefore only in affected daughters. To test this hypothesis, we have analysed 19 families with RTT syndrome due to MECP2 molecular defects. In seven informative families we have found by DHPLC a nucleotide variant which could be used to differentiate between the maternal and the paternal allele. In each subject investigated from these families, we have amplified specifically each allele and sequenced allele-specific PCR products to identify the allele bearing the mutation as well as the parental origin of each X chromosome. This approach allowed us to determine the parental origin of de novo mutations in all informative families. In five cases, the de novo MECP2 mutations have a paternal origin and in the two other cases a maternal origin. In all transitions at CpG, the de novo mutation observed was of paternal origin. The high frequency of male germ-line transmission of the mutation (71% of RTT informative cases) is consistent with a predominant occurrence of the disease in females.  相似文献   
20.
In chronic beryllium disease (CBD), a granulomatous lung disease characterized by hypersensitivity to beryllium salts (BE), BE challenge of bronchoalveolar lavage cells induces IFNgamma. Although nitric oxide (NO) is elevated in CBD airways, the effects of NO on CBD IFNgamma responses are unknown. Here we report that BE-stimulated IFNgamma production in CBD lavage cells was markedly reduced (74%) by the NO generator DETA NONOate. Investigation of IFNgamma-stimulatory cytokine involvement indicated that lavage cell IL-18 was significantly increased (fourfold) by BE and reduced (64%) by DETA NONOate but IL-12 was undetectable. IL-18 production was caspase-1-dependent but caspase 1 inhibition reduced IFNgamma only partially (43%). Specific antibody depletion of lavage cell IL-18 yielded marginal reduction (19%) of IFNgamma. Data are the first to show that: (1) BE stimulates IL-18 as well as IFNgamma in CBD; (2) BE cytokine responses are NO-sensitive; and (3) NO down-regulation of IFNgamma involves other sites in addition to IL-18.  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