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   16005篇
  免费   1008篇
  国内免费   76篇
耳鼻咽喉   92篇
儿科学   293篇
妇产科学   212篇
基础医学   2306篇
口腔科学   139篇
临床医学   2057篇
内科学   3939篇
皮肤病学   332篇
神经病学   1382篇
特种医学   669篇
外国民族医学   3篇
外科学   2524篇
综合类   60篇
一般理论   6篇
预防医学   757篇
眼科学   242篇
药学   1077篇
中国医学   25篇
肿瘤学   974篇
  2023年   91篇
  2022年   96篇
  2021年   457篇
  2020年   231篇
  2019年   356篇
  2018年   431篇
  2017年   292篇
  2016年   308篇
  2015年   405篇
  2014年   574篇
  2013年   740篇
  2012年   1226篇
  2011年   1336篇
  2010年   682篇
  2009年   657篇
  2008年   1074篇
  2007年   1072篇
  2006年   1026篇
  2005年   1018篇
  2004年   936篇
  2003年   877篇
  2002年   825篇
  2001年   196篇
  2000年   179篇
  1999年   180篇
  1998年   184篇
  1997年   152篇
  1996年   111篇
  1995年   84篇
  1994年   79篇
  1993年   89篇
  1992年   118篇
  1991年   96篇
  1990年   81篇
  1989年   84篇
  1988年   87篇
  1987年   73篇
  1986年   74篇
  1985年   62篇
  1984年   50篇
  1983年   48篇
  1982年   33篇
  1981年   33篇
  1980年   38篇
  1979年   24篇
  1978年   22篇
  1976年   20篇
  1975年   31篇
  1973年   18篇
  1967年   20篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
51.
OBJECTIVE: To report on the high incidence of anatomical variants of the origin and course of the internal spermatic vein (ISV) discovered at the time of percutaneous embolization of left varicoceles in a pediatric population. METHODS: We reviewed retrospectively the 65 cases of left varicocele treated by percutaneous embolization (grade II and III) in our institution between 1990 and 2000. The course of the left renal vein (LRV), the origin of the ISV, and the number of ISVs and their pathway were recorded in all cases, according to the B?hren classification. RESULTS: In 37/65 (57%), the ISV was single and arose from a normal LRV (type I). The following variants were encountered: type V--circumaortic LRV 9/65 (14%); type IVb--intrarenal origin of ISV 8/65 (12%); type II--multiple ISV 5/65 (8%); and pelvic collaterals 6/65 (9%). CONCLUSION: Venous anatomical variants are frequently encountered (43%) at the time of left varicocele embolization in children. Such variants often impose some adjustments to the technique of embolization and, at times, hamper the procedure.  相似文献   
52.
Recently, an 86-amino acid polypeptide with high affinity for diazepam binding sites, termed diazepam-binding inhibitor (DBI), has been found in the rat brain. DBI, as well as a peptide derived from DBI, the octadecaneuropeptide DBI[33–50] (ODN), interacts with the GABAA receptor complex. To investigate the role of these endogenous ligands for GABAA receptors on prolactin gene expression, we studied the effects of acute intracerebroventricular administration (4  h before sacrifice) of ODN on prolactin mRNA levels in the male rat. Because, in some neuropeptidergic systems, glucocorticoids play a role in the response to ODN, we also studied the influence of adrenal glands and the effect of dexamethasone administration in the response of prolactin gene expression to ODN. ODN injection produced an increase in prolactin mRNA levels. Adrenalectomy performed 5 days before sacrifice resulted in an increase in prolactin gene expression and also potentiated the stimulating effect of ODN. Because castration has been shown to decrease prolactin gene expression in the male rat, we used castrated and adrenalectomized animals to study the role of dexamethasone in the response of lactotrophs to ODN. In these steroid-deprived animals, dexamethasone treatment (for 4 days) decreased prolactin mRNA levels but did not modify the response to ODN. These data indicate that an endogenous neuropeptide interacting with the GABAA receptor complex can stimulate prolactin gene expression and suggest that the adrenal glands may produce factor(s) capable of decreasing prolactin mRNA. On the other hand, it does not appear that glucocorticoid hormones play a role in the effect of ODN on lactotroph activity.  相似文献   
53.
The myocardial uptake of fatty acids labeled with radioactive iodine and injected i.v. can only be evaluated with SPECT if their oxidation kinetics is slow enough. For this reason, we evaluated different iodomethylated fatty acids in mice and dogs to determine which of them shows the highest myocardial uptake and the slowest oxidation. The most suitable was found to be 16-iodo-3-methyl hexadecanoic acid (mono ) since its myocardial fixation was the same as that of the reference, i.e. 16-iodo-9-hexadecenoic acid (IHA), whereas it was degraded more slowly. Thirty min after injection of mono into dogs, the decrease in myocardial activity with respect to the maximum was two fold less than after IHA injection. The myocardial uptake of the two dimethylated fatty acids studied, i.e. 16-iodo-2,2-methyl hexadecanoic acid and 16-iodo-3,3-methyl hexadecanoic acid, was less than that of IHA in mice and dogs. In the latter, the myocardial uptake was so small that we were unable to study the time course of its activity. Consequently, these dimethylated fatty acids are not suitable for the study of the myocardial uptake of fatty acids in man.  相似文献   
54.
Conventional suture repair of peripheral nerves results in a fibrotic reaction that is detrimental to nerve regeneration. As an alternative procedure known as "laser-assisted" repair, a laser can be used, along with a reduced number of sutures, to reanastomose served peripheral nerves. To explore the long-term implications of this technique, the right sciatic nerves of Sprague-Dawley rats were surgically cut and reanastomosed either by means of four epineurial sutures or two epineurial sutures and CO2 laser welds. Tensile strength, electrophysiology, histology, and functional studies were performed up to 11 months postoperatively. Tensile strength measurements indicate no long-term disadvantage with the laser-assisted technique, although the short-term tensile strength is lower than with conventional suture repair. The conduction velocities of the repaired nerves were similar for both techniques; however, laser-assisted repaired nerves were found to have lower stimulation thresholds and reduced branching compared to the suture repaired nerves. The measured functional recovery was similar for both repair techniques.  相似文献   
55.
Members of the epidermal growth factor (EGF) family and their receptors are involved in many cellular processes, including proliferation, migration, and differentiation. We have previously reported that these growth factors are expressed and have specific regulatory functions in an organ-like culture model of normal human urothelial cells. Here, we used this model to investigate the involvement of EGF receptor (EGFR) in human urothelial regeneration. Three 4-mm-diameter damaged areas were made in confluent normal human urothelial cell cultures with a biopsy punch. Regeneration was measured, on fixed stained cultures, with an image analyzer, at 4, 24, and 48 hours after injury. Cell proliferation was assessed by 5-bromo-2-deoxyuridine incorporation. To identify EGF family factors potentially involved in the healing process, we studied the effect of these factors on damaged confluent cultures and the level of expression of mRNAs extracted from these cultures. EGFR inhibition of the proliferation and migration of urothelial cells was tested with (1). a specific tyrosine kinase inhibitor (AG1478) and (2). a blocking anti-EGFR antibody (LA22). Exogenously added amphiregulin, EGF, transforming growth factor-alpha and heparin-binding EGF (HB-EGF) stimulated urothelial regeneration. The damaged areas were repaired by regrowth within 48 hours. Both AG1478 and LA22 inhibited the repair (by 50% and 30%, respectively), as well as proliferation and migration. This regeneration was accompanied by increased HB-EGF mRNA expression in cultures of cells from four of six subjects, but no corresponding change in EGFR protein level was observed. These results indicate that the EGFR signaling pathway is involved in urothelial regeneration. Our data support an autocrine role of HB-EGF in this process and suggest that the EGFR pathway is a potential therapeutic target for modulating urothelial cell proliferation.  相似文献   
56.
BACKGROUND: Sj?gren's syndrome (SS) is an autoimmune exocrinopathy associated with multiple autoantibodies, lymphocyte infiltration of various organs, and functional deficiency of T cells. Several viruses have been implicated by PCR based studies, but their contribution to the pathophysiology of SS is still controversial. OBJECTIVES: In an attempt to explore the presence of human herpesviruses DNA sequences in salivary glands biopsies from patients suffering of SS, a recently developed strategy based on PCR with consensus degenerated primers that allowed to detect known and eventually unknown herpesviruses was used. STUDY DESIGN: Salivary glands biopsies from 55 patients suffering of primary and SS syndrome were explored by herpesviruses consensus PCR primers and all the PCR products were sequenced. RESULTS: Nine out of 55 salivary glands were positive by PCR and sequence analyses allowed to identify Epstein-Barr virus (EBV) in 6 cases and herpes simplex virus (HSV)-1 in 3 cases. We did not detect any sequences that could be related to a new herpesvirus. CONCLUSION: In view of the good sensitivity of the technique used, our study is not consistent with SS being associated with an unknown herpesvirus. However, our results suggest that EBV and HSV-1 could be implicated in a subset of SS cases and this possibility needs to be explored, to assess the potential benefit of antiviral drugs in some cases.  相似文献   
57.
58.
Predictive factors of the virologic success of the use of lopinavir/ritonavir (LPV/r) in HIV-infected children are unknown, especially in children who have been pretreated with protease inhibitors (PIs). This longitudinal, single-center, observational study included 69 children (21 PI-naive and 48 PI-experienced) who had received LPV/r for at least 3 months. The mean (+/- SD) age was 10.3 +/- 4.8 years, and the mean baseline of CD4 percentage and HIV-1 RNA was 14.9% +/- 9.8% and 4.8 +/- 1.05 log10 copies/mL, respectively. The mean duration of follow-up was 16.5 +/- 8.3 months. At 6, 12, and 18 months, 52%, 57%, and 49% of all children, respectively, had a viral load less than 50 copies/mL. The risk of virologic failure, defined as 2 consecutive viral loads greater than 1000 copies/mL, was significantly higher when the children were previously treated with PIs and when the baseline LPV mutation score exceeded 3 mutations. In the pretreated children, the ratio of the plasma LPV maximal concentration to the baseline LPV score mutation was also associated with failure, independently of resistance score. Finally, in children failing an LPV-containing regimen, accumulation of additional PI-associated resistance mutations was evidenced in viral isolates from children with prior PI treatment, even with viral replication levels less than 10,000 copies/mL. In pretreated children, LPV plasma levels should be optimized in an attempt to achieve sufficient drug concentrations to overcome the resistance level.  相似文献   
59.
Immunodeficiency related to HIV may increase the incidence of EBV-associated lymphomas, by altering EBV-specific immune control and consequently favoring EBV reactivation. The aim of the present study was to assess the relationship between the decrease of EBV-specific cellular immunity and the increase of EBV reactivation in a prospective cohort of 72 unselected HIV-infected individuals. EBV-specific immunity was evaluated by a highly sensitive IFN-gamma ELISPOT assay using 22 peptides mimicking latent and lytic antigens, and circulating mononuclear (PBMC) EBV DNA load was quantified by real-time quantitative PCR. The mean circulating cell-associated EBV DNA load was higher in HIV-infected patients (639 copies/10(6) PBMC) than in healthy controls (21, n = 14) ( P = 0.005) and was higher in patients with CD4(+) T-cell count below 350/microL than that in patients harboring higher CD4(+) T-cell count (1112 vs. 389, P = 0.003). The mean intensity of EBV-specific cellular responses was lower in HIV-infected patients than in controls ( P = 0.001), even in patients with CD4(+) T-cell count above 350/-microL ( P = 0.007). The number of EBV peptides recognized was lower in HIV-infected patients than in controls (frequency: 0.44 vs. 0.67; P = 0.02), indicating reduced polyclonality in HIV-infected patients. The polyclonality was 1.5-fold lower in HIV-infected patients with CD4(+) T-cell count below 350/-microL ( P =0.007). For EBV load >1000 copies/10(6) PBMC, the levels of cell-associated EBV DNA and those of EBV-specific cellular immunity, either in intensity or in polyclonality, or both, were inversely correlated. These findings demonstrate early impairment of the EBV-specific cellular immune control with progressive increase of EBV reactivation in the course of HIV infection. These observations likely provide a basis for appreciating the risk to develop non-Hodgkin's lymphomas in HIV-infected individuals.  相似文献   
60.
In order to examine the immunopathogenesis of hepatitis C virus (HCV)-related liver injury in renal-transplant patients, intra-hepatic cytokine profiles were examined in 38 liver biopsies from 38 patients by measuring messenger RNA (mRNA) concentrations by a real-time PCR method of a Th1 cytokine (i.e., interferon (IFN)-gamma), a Th2 cytokines (i.e., interleukine (IL)-10), a proinflammatory cytokine (i.e., IL-8), and a potent fibrogenic factor (transforming growth factor [TGF]-beta). There was no significant difference in TGF-beta, IFN-gamma, IL-10, or IL-8 levels of expression according to liver-activity grade, liver-fibrosis stage, the concentration of HCV RNA at liver biopsies, or the HCV genotype. However, IFN-gamma/beta-actin mRNA concentration was higher than the IL-10/beta-actin mRNA concentration in patients with F3 Metavir score. Median IFN-gamma/beta-actin mRNA concentration tended to be higher in patients with A3 and A4 Metavir activity grades compared with those with A0 and A1 activity grades. There was a significant correlation between the duration of HCV infection and both TGF-beta/beta-actin (r(2)=0.19, P=0.04) and IL-8/beta-actin mRNA concentrations (r(2)=0.19, P=0.03). IFN-gamma/beta-actin mRNA concentration also increased according to the duration of HCV (r(2)=0.19, P=0.07). Finally, there was a significant correlation between the duration of HCV infection and liver fibrosis stage (r(2)=0.17, P=0.045). Intrahepatic Th1 cytokine profile seems to be predominant in patients with extensive fibrosis and activity scores, suggesting that it might be responsible for liver injury in renal transplant patients.  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