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   9771篇
  免费   765篇
  国内免费   33篇
耳鼻咽喉   53篇
儿科学   214篇
妇产科学   127篇
基础医学   1419篇
口腔科学   65篇
临床医学   1083篇
内科学   2618篇
皮肤病学   146篇
神经病学   791篇
特种医学   416篇
外科学   1471篇
综合类   21篇
一般理论   1篇
预防医学   530篇
眼科学   187篇
药学   708篇
中国医学   20篇
肿瘤学   699篇
  2024年   5篇
  2023年   57篇
  2022年   105篇
  2021年   286篇
  2020年   148篇
  2019年   275篇
  2018年   306篇
  2017年   218篇
  2016年   237篇
  2015年   294篇
  2014年   405篇
  2013年   508篇
  2012年   893篇
  2011年   900篇
  2010年   474篇
  2009年   402篇
  2008年   693篇
  2007年   669篇
  2006年   695篇
  2005年   640篇
  2004年   603篇
  2003年   561篇
  2002年   487篇
  2001年   74篇
  2000年   52篇
  1999年   77篇
  1998年   95篇
  1997年   62篇
  1996年   44篇
  1995年   34篇
  1994年   39篇
  1993年   30篇
  1992年   28篇
  1991年   16篇
  1990年   17篇
  1989年   13篇
  1988年   16篇
  1987年   9篇
  1986年   10篇
  1985年   13篇
  1984年   7篇
  1983年   9篇
  1982年   5篇
  1981年   7篇
  1980年   6篇
  1978年   6篇
  1975年   3篇
  1974年   4篇
  1972年   7篇
  1971年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
PURPOSE: This randomized, 2 x 2 factorial study compared a semimonthly (LVFU2) with a monthly (FULV) regimen of fluorouracil and leucovorin and 24 versus 36 weeks of each regimen as adjuvant treatment of patients with stage II (Dukes' B2) and III (Dukes' C) colon cancer. PATIENTS AND METHODS: LVFU2 was administered semi-monthly for 2 consecutive days as dl- or l-leucovorin (200 or 100 mg/m2, respectively) as a 2-hour infusion, followed by a 400 mg/m2 FU bolus and 600 mg/m2 of FU as a 22-hour continuous infusion. FULV was administered monthly for 5 consecutive days as a 15-minute infusion of dl- or l-leucovorin, followed by 400 mg/m2 of FU as a 15-minute infusion. RESULTS: A total of 905 patients were randomly assigned. The median follow-up was 41 months. Disease-free survival was similar between the LVFU2 and FULV groups (127 v 124 events; hazard ratio [HR] = 1.04; P =.74) and between 24 and 36 weeks of therapy (128 v 123 events; HR = 0.94; P =.63). Analysis of overall survival showed a slight excess in the number of deaths in LVFU2 compared with FULV (73 v 59), but this difference was not statistically significant (HR = 1.26; 95% confidence interval, 0.90 to 1.78; P =.18). The most commonly observed grade 3 to 4 toxicities were neutropenia, diarrhea, and mucositis. Toxicities were significantly lower in the LVFU2 group (all toxicities, P <.001). CONCLUSION: Our data confirm that LVFU2 is less toxic than FULV. At a median follow-up of 41 months, no statistically significant difference could be detected in disease-free or overall survival between the treatment groups or treatment durations.  相似文献   
82.
PURPOSE: Radiolabeled annexin V may allow for repetitive and selective in vivo identification of apoptotic cell death without the need for invasive biopsy. This study reports on the relationship between quantitative technetium-99m- (99mTc-) 6-hydrazinonicotinic (HYNIC) radiolabeled annexin V tumor uptake, and the number of tumor apoptotic cells derived from histologic analysis. PATIENTS AND METHODS: Twenty patients (18 men, two women) suspected of primary (n = 19) or recurrent (n = 1) head and neck carcinoma were included. All patients underwent a spiral computed tomography (CT) scan, 99mTc-HYNIC annexin V tomography, and subsequent surgical resection of the suspected primary or recurrent tumor. Quantitative 99mTc-HYNIC annexin V uptake in tumor lesions divided by the tumor volume, derived from CT, was related to the number of apoptotic cells per tumor high-power field derived from terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling (TUNEL) assays performed on sectioned tumor slices. RESULTS: Diagnosis was primary head and neck tumor in 18 patients, lymph node involvement of a cancer of unknown primary origin in one patient, and the absence of recurrence in one patient. Mean percentage absolute tumor uptake of the injected dose per cubic centimeter tumor volume derived from tomographic images was 0.0003% (standard deviation [SD], 0.0004%) at 1 hour postinjection (PI) and 0.0001% (SD, 0.0000%) at 5 to 6 hours PI (P =.012). Quantitative 99mTc-HYNIC annexin V tumor uptake correlated well with the number of apoptotic cells if only tumor samples with no or minimal amounts of necrosis were considered. CONCLUSION: In the absence of necrosis, absolute 99mTc-HYNIC annexin V tumor uptake values correlate well with the number of apoptotic cells derived from TUNEL assays.  相似文献   
83.
PURPOSE: The aim of this study was to investigate the hypothesis that, independent of other known prognostic factors, pessimistic head and neck (H&N) cancer patients have a greater risk of being dead 1 year after diagnosis than do optimistic patients. PATIENTS AND METHODS: A prospective observational study design was used with a cohort of H&N cancer patients diagnosed during the period from March 1, 1997, to August 31, 1998, at the Centre Hospitalier Universitaire, Clermont-Ferrand, France. Dispositional optimism (DO) was evaluated at baseline using a French version of the Life Orientation Test translated and validated for this study. One-year survival status was collected on all subjects. The analysis of the hypothesized association between DO and 1-year survival was performed using multiple logistic regression analysis, controlling for other sociodemographic and clinical variables. RESULTS: The sample size was 101 patients, representing all but one of those patients fitting the inclusion criteria who were diagnosed during the recruitment period. Of these, 51 were alive at 1 year after diagnosis, 45 were dead, and five were lost to follow-up. The multivariate analysis was performed on the data from the 96 subjects in whom 1-year survival status was known. Controlling for known predictors of H&N cancer survival, pessimistic subjects (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.01 to 1.24) and those living alone (OR, 4.14; 95% CI, 1.21 to 14.17) were more likely than optimistic subjects and those living with others to be dead at 1 year. CONCLUSION: The results of this study of a cohort of French H&N cancer patients indicate that dispositional optimism predicts 1-year survival independent of other sociodemographic and clinical variables.  相似文献   
84.
In order to compare phylogenetic methods and to reconstruct the evolutionary history of the tubercle bacilli, a set of macro-array-based genotyping data of Mycobacterium tuberculosis clinical isolates (called spoligotyping for spacer oligonucleotide typing, which assays the variability of the Direct Repeat -DR- locus), was analyzed in four settings of the Caribbean region (Guadeloupe, Martinique, Cuba and Haiti). A set of 47 alleles, split into 26 shared and 21 unique alleles) representative of 321 individual M. tuberculosis clinical isolates from patients residing in the above regions was studied. The following methods (and software in brackets) were investigated: numerical taxonomy distance methods (TAXOTRON), maximum parsimony procedure (PAUP), median-joining networks (NETWORK), and nested clade analysis (GEODIS). Results using these methods were analyzed, compared and discussed. The latter method (GEODIS) was investigated in detail by introducing geographical data together with genetic variability results to detect a link between population structure and population history, and to test the null hypothesis of no association between geography and genotypes. Irrespective of the methods used, our findings demonstrate that a core structure of four families (or clades) of M. tuberculosis strains is highly prevalent within the islands studied, indirectly reflecting passed colonization history of these different settings. Specificity of M. tuberculosis genotypes in each of the islands is discussed in the light of their respective colonial and contemporary histories.  相似文献   
85.
Epoxide hydrolases play an important role in detoxifying epoxides that arise from the metabolism of xenobiotic and endogenous compounds. Both the soluble and microsomal forms of epoxide hydrolase (sEH and mEH, respectively) have been detected in the rat testis. Because of the important role the epididymis plays in sperm maturation and protection, the present study evaluated the presence and activity of these two epoxide hydrolases in the rat epididymis. Using Western blotting, protein bands consistent in size with both mEH and sEH were detected in the caput, corpus, and cauda of the epididymis. The mEH immunoreactive bands in the epididymis ( approximately 50 kDa) were consistent with mEH detected in the liver and kidney. The sEH immunoreactive bands in the epididymis ( approximately 65 kDa) were consistent with a recombinant sEH standard and sEH detected in the liver, kidney, and testis. The presence of mEH and sEH in the epididymis was supported by observations from substrate-based enzyme assays. Results indicated that epididymal mEH can hydrolyze [(3)H]-cis-stilbene oxide to the corresponding diol at levels approximately 9% of the kidney. Epididymal sEH hydrolyzed the substrate [(3)H]-trans-diphenylpropene oxide to the corresponding diol and this activity was inhibited by cyclohexyl-dodecyl urea. Arachidonic acid epoxygenase activity was detected in epididymal S9 fractions, suggesting that fatty acid metabolism by epididymal cytochrome P450s can form epoxides that subsequently become substrates for epididymal sEH. Results from the present study indicate that the epididymis contains at least two active forms of epoxide hydrolase. The role of these enzymes in the detoxification of xenobiotic epoxides is well known, although it is unclear what cellular role they may play in the formation of biologically active metabolites in the epididymis.  相似文献   
86.
87.
Plant-derived polyphenols flavonoids are increasingly being recognized for their medicinal potential. These bioactive compounds derived from plants are gaining more interest in ameliorating adverse health risks because of their low toxicity and few side effects. Among them, therapeutic approaches demonstrated the efficacy of catechins, a major group of flavonoids, in reverting several aspects of Down syndrome, the most common genomic disorder that causes intellectual disability. Down syndrome is characterized by increased incidence of developing Alzheimer’s disease, obesity, and subsequent metabolic disorders. In this focused review, we examine the main effects of catechins on comorbidities linked with Down syndrome. We also provide evidence of catechin effects on DYRK1A, a dosage-sensitive gene encoding a protein kinase involved in brain defects and metabolic disease associated with Down syndrome.  相似文献   
88.

Purpose

To compare the effects of 2 different media on embryo morphology and development at days 2/3.

Method

Six hundred seventy-six attempts from 512 couples were included in this prospective auto-controlled study. Sibling oocytes of all couples undergoing an IVF (n?=?286) or ICSI (n?=?390) attempt were randomly assigned to either GIII series (Vitrolife) or ISM (Medicult) media. Primary end points were fertilization and embryo morphology rates.

Results

Fertilization rates in GIII series and ISM (IVF: 59.9 vs 62.0% and ICSI: 65.7 vs 66.8%) respectively were not different. GIII series showed an increase, compared to ISM, of early cleavage rate, (IVF: 25.8 vs 16.2% (p?=?0.005); ICSI: 40.8 vs 25.5% (p?<?0.0001), and good embryo morphology rate at day 2 [IVF: 64.6 vs 57.3% (p?=?0.01); ICSI: 74.2 vs 69.4 (p?=?0.03)] and at day 3 [IVF: 57.5 vs 49.0% (p?=?0.02); ICSI: 67.2 vs 61.6% (p?=?0.01)].

Conclusions

Embryo morphology at days 2/3 was significantly enhanced when the embryos were cultured in GIII series.  相似文献   
89.
90.
Recently the two vesicular-glutamate-transporters VGLUT1 and VGLUT2 have been cloned and characterized. VGLUT1 and VGLUT2 together label all glutamatergic neurons, but because of their distinct expression patterns in the brain they facilitate our ability to define between a VGLUT1-positive cortical and a VGLUT2-positive subcortical glutamatergic systems. We have previously demonstrated an increased cortical VGLUT1 expression as marker of antidepressant activity. Here, we assessed the effects of different psychotropic drugs on brain VGLUT2 mRNA and protein expression. The typical antipsychotic haloperidol, and the atypicals clozapine and risperidone increased VGLUT2 mRNA selectively in the central medial/medial parafascicular, paraventricular and intermediodorsal thalamic nuclei; VGLUT2 protein was accordingly amplified in paraventricular and ventral striatum and in prefrontal cortex. The antidepressants fluoxetine and desipramine and the sedative anxiolytic diazepam had no effect. These results highlight the implication of thalamo-limbic glutamatergic pathways in the action of antipsychotics. Increased VGLUT2 expression in these neurons might constitute a marker for antipsychotic activity and subcortical glutamate neurotransmission might be a possible novel target for future generation antipsychotics.  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