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   8810篇
  免费   647篇
  国内免费   23篇
耳鼻咽喉   47篇
儿科学   253篇
妇产科学   247篇
基础医学   1344篇
口腔科学   192篇
临床医学   1046篇
内科学   1684篇
皮肤病学   240篇
神经病学   1153篇
特种医学   240篇
外科学   724篇
综合类   67篇
一般理论   9篇
预防医学   800篇
眼科学   301篇
药学   553篇
中国医学   20篇
肿瘤学   560篇
  2023年   74篇
  2022年   101篇
  2021年   211篇
  2020年   187篇
  2019年   215篇
  2018年   275篇
  2017年   214篇
  2016年   225篇
  2015年   272篇
  2014年   304篇
  2013年   459篇
  2012年   740篇
  2011年   733篇
  2010年   381篇
  2009年   349篇
  2008年   653篇
  2007年   604篇
  2006年   568篇
  2005年   524篇
  2004年   487篇
  2003年   453篇
  2002年   439篇
  2001年   68篇
  2000年   45篇
  1999年   64篇
  1998年   84篇
  1997年   75篇
  1996年   69篇
  1995年   48篇
  1994年   51篇
  1993年   43篇
  1992年   30篇
  1991年   27篇
  1990年   18篇
  1989年   16篇
  1988年   17篇
  1987年   22篇
  1986年   19篇
  1985年   19篇
  1984年   24篇
  1983年   17篇
  1982年   24篇
  1980年   17篇
  1979年   13篇
  1978年   23篇
  1977年   14篇
  1976年   12篇
  1975年   12篇
  1971年   12篇
  1968年   11篇
排序方式: 共有9480条查询结果,搜索用时 203 毫秒
21.
Zusammenfassung Aus Leichenbränden werden einige Skelettelemente mit Verformungen vorgelegt, die durch äußere Einwirkungen während des Festigkeitsminimums der Knochensubstanz zwischen 400–500°C entstanden sein müssen. Derartige Belastungsdeformationen konnten bisher in einigen Fällen an Gelenkregionen verschiedener Langknochen sowie häufiger an Arcusteilen größerer Wirbel beobachtet werden. Als Ursache wäre eine beabsichtigte Beschwerung der Gelenkregionen zu ihrer Fixierung während der Kremation denkbar sowie aufgrund der an den Corpus vertebrae herangedrückten Arcusteile nur der unterern (!) Wirbel eine Rückenlage des Leichnams auf der Verbrennungsstelle. Experimentelle Verbrennungen, um den erforderlichen Gewichtsdruck zur Erzeugung von Belastungsdeformationen zu ermitteln, wären wünschenswert.  相似文献   
22.
23.
Patients after kidney, heart and lung transplantation differ in their immunosuppressive drug regimens and in susceptibility to infectious complications with cytomegalovirus (CMV). In this study, CMV-specific T-cell responses were characterized in long-term transplant recipients and associated with the frequency of infectious complications. CMV-reactive CD4 T cells from 50 healthy controls, 68 renal, 14 heart and 24 lung transplant recipients were flow cytometrically quantified by the induction of cytokines after specific stimulation. Moreover, the immunosuppressive effect of calcineurin inhibitors on specific T-cell reactivity was quantified in vitro and compared with responses in vivo. Median CMV-specific T-cell frequencies in long-term renal (1.48%; range 0.06-17.26%) and heart transplant recipients (0.90%; 0.13-12.49%) did not differ from controls (1.82%; 0.26-21.00%). In contrast, CMV-specific T-cell levels were significantly lower in lung transplant recipients (0.50%; <0.05-4.98%) and showed a significant correlation with the frequency of infectious episodes (r =-0.57, p = 0.005). The differences within the groups were associated with increasing dosages of immunosuppressive drugs, as exemplified for calcineurin inhibitors that dose dependently reduced specific T-cell reactivity in vitro. In conclusion, monitoring CMV-specific CD4 T cells may serve as a measure for long-term disease susceptibility and may contribute to an improved management of CMV complications after lung transplantation.  相似文献   
24.
25.
Use of antibiotic and analgesic drugs during lactation.   总被引:2,自引:0,他引:2  
During lactation, multiple situations can arise that require maternal pharmacological treatment. Because of the many health advantages of human milk to infants, breast feeding should be interrupted only when the needed drug might be harmful to the nursing child and exposure via the breast milk will be sufficient to pose a risk. Since the majority of drugs have not been shown to cause adverse effects when used during lactation, and even temporary interruption of breast feeding can be difficult for the nursing dyad, decisions regarding maternal medication use during breast feeding should be based on accurate and up-to-date information. This article reviews available data on the most commonly used antibiotics and analgesics. The use of most antibiotics is considered compatible with breast feeding. Penicillins, aminopenicillins, clavulanic acid, cephalosporins, macrolides and metronidazole at dosages at the low end of the recommended dosage range are considered appropriate for use for lactating women. Fluoroquinolones should not be administered as first-line treatment, but if they are indicated, breast feeding should not be interrupted because the risk of adverse effects is low and the risks are justified. Paracetamol (acetaminophen), low-dose aspirin (acetylsalicylic acid) [up to 100 mg/day] and short-term treatment with NSAIDs, codeine, morphine and propoxyphene are considered compatible with breast feeding. Safer alternatives should be considered instead of dipyrone, aspirin at a dosage >100 mg/day and pethidine (meperidine). In the light of the many safe alternatives for pain control, breast-feeding mothers should not be allowed to experience pain or be made to feel that they must choose between analgesia and breast feeding.  相似文献   
26.
Abstract: Blast cells derived from peripheral blood of patients with acute myelogenous leukaemia (AML) were cultured in vitro and interleukin 1 receptor antagonist (IL1RA) concentrations determined in culture supernatants. AML blasts derived from patients classified as AML-M4 and AML-M5 subtype showed an increased release of IL1RA. IL1α and IL1β caused a similar increase in AML blast release of IL1RA, and addition of anti-ILl antibodies decreased IL1RA release. IL1RA release from AML blasts was also increased by stem cell factor, tumour necrosis factor α (TNFα), granulocyte-macrophage colony-stimulating factor and macrophage colony-stimulating factor, whereas interleukin 3, interleukin 6, leukaemia inhibitory factor and granulocyte colony- stimulating factor did not significantly alter IL1RA release. When investigating IL1RA serum levels, serum concentrations were decreased in acute leukaemia patients with chemotherapy-induced cytopenia compared with healthy controls. Serum levels of both IL1RA as well as IL1β and soluble TNFα receptors increased when the leucopenic patients developed complicating bacterial infections.  相似文献   
27.
Serum Carnitine During Valproic Acid Therapy   总被引:12,自引:7,他引:5  
This study was initiated to examine the influence of valproic acid (VPA) on serum carnitine, as well as the possible etiological role of carnitine in VPA-induced fatal hepatotoxicity. Free, total, and short-chain acylcarnitine were measured in the serum of 21 pediatric patients receiving VPA therapy, 21 healthy matched controls, and 21 patients receiving various antiepileptic drugs other than VPA. The free carnitine level was lowest in the VPA group (p less than 0.05), and the short-chain acylcarnitine/free carnitine ratio was highest in the VPA group (p less than 0.01). Patients receiving VPA polytherapy had lower total carnitine values than patients receiving VPA monotherapy (p less than 0.05). No correlation was found between serum ammonia and VPA drug levels. A 3 1/2-year-old girl developed hepatic failure under VPA therapy. Her serum carnitine values were normal. Despite the oral intake of L-carnitine this patient died. In this case, apparently VPA-induced hepatotoxicity was not associated with carnitine deficiency. The reduction of carnitine in the serum of VPA-treated patients is most probably due to alterations of fatty acid metabolism. However, neither primary carnitine deficiency nor VPA-induced secondary carnitine deficiency can be the only reason for the VPA-induced fatal hepatotoxicity.  相似文献   
28.
29.
We studied vascular endothelial growth factor (VEGF) expression in bone marrow sections obtained from 3 healthy donors and 41 patients with acute myeloid leukemia (AML) of various French-American-British (FAB) subtypes by immunohistochemical analysis using an anti-VEGF antibody. In normal bone marrow, the anti-VEGF antibody reacted with myeloid progenitor cells and megakaryocytes but not with erythroid cells or mature granulocytic cells. High levels of VEGF were found in the bone marrow in patients with AML-M1, -M2, -M3, -M4, -M4Eo, and -M5. In these leukemias, the vast majority of myeloblasts (> 90%) expressed VEGF. By contrast, in AML-M0, the percentage of VEGF-positive blasts was lower in most cases (median, 42%), and if at all detectable, these blast cells contained only trace amounts of VEGF. In AML-M3 and -M4Eo, maturing granulocytes failed to express VEGF similar to granulocytes in normal bone marrow. In AML-M6, myeloblasts exhibited VEGF, whereas erythroid cells did not. In AML-M7, blast cells and megakaryocytes were identified as major sources of VEGF. In summary, VEGF expression in the bone marrow is restricted to certain stages of differentiation and maturation of myeloid cells and correlates with the FAB category.  相似文献   
30.
Falk I  Eichmann K 《Immunology letters》2002,82(1-2):123-130
Recent studies have shown that apoptotic cell death associated with selection for thymocytes that express clonotypic TCRbeta or TCRgammadelta proteins takes place in the DN4 (CD44-CD25-) subset of CD4-CD8- double negative (DN) thymocytes. A detailed analysis of the DN4 subset is therefore of interest. Using intracellular (IC) staining for clonotypic TCR and CD3varepsilon proteins we find that DN4 cells consist of five subpopulations: TCRbetaIC(high)/CD3varepsilonIC(high)/TCRgammadeltaIC-, TCRbetaI-C-/CD3varepsilonIC(high)/TCRgammadeltaIC(+), TCRbetaIC(high)/CD3varepsilonIC(high)/TCRgammadeltaIC(+), TCRbetaIC(low)/CD3varepsilonIC(low)/TCRgammadeltaIC(-), and TCRbetaIC(-)/CD3varepsilonIC(-)/TCRgammadeltaIC(-). Expression levels of IC TCRbeta/CD3varepsilon, and of Thy1.2, CD2, and CD69 at the cell surface suggest that the TCRbetaIC(low)/CD3varepsilonIC(low)/TCRgammadeltaIC(-) subset harbors the direct precursors of DP cells, and is critical for life/death decisions in early thymic selection. TCRbeta/CD3varepsilon downregulation is less pronounced in DN4 and DP cells of mice deficient for CD3zeta or for p56(lck), suggesting that the dynamics of TCR protein regulation in the DN4 subset is dependent on CD3 signaling.  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