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   10313篇
  免费   492篇
  国内免费   56篇
耳鼻咽喉   115篇
儿科学   178篇
妇产科学   221篇
基础医学   1187篇
口腔科学   258篇
临床医学   775篇
内科学   2803篇
皮肤病学   148篇
神经病学   1113篇
特种医学   298篇
外科学   1332篇
综合类   24篇
一般理论   3篇
预防医学   458篇
眼科学   204篇
药学   723篇
中国医学   14篇
肿瘤学   1007篇
  2024年   9篇
  2023年   64篇
  2022年   144篇
  2021年   264篇
  2020年   164篇
  2019年   211篇
  2018年   241篇
  2017年   213篇
  2016年   241篇
  2015年   260篇
  2014年   352篇
  2013年   525篇
  2012年   758篇
  2011年   783篇
  2010年   420篇
  2009年   409篇
  2008年   714篇
  2007年   761篇
  2006年   748篇
  2005年   701篇
  2004年   693篇
  2003年   615篇
  2002年   554篇
  2001年   69篇
  2000年   59篇
  1999年   54篇
  1998年   109篇
  1997年   75篇
  1996年   78篇
  1995年   76篇
  1994年   73篇
  1993年   63篇
  1992年   42篇
  1991年   31篇
  1990年   35篇
  1989年   29篇
  1988年   18篇
  1987年   20篇
  1986年   21篇
  1985年   17篇
  1984年   19篇
  1983年   18篇
  1982年   17篇
  1981年   24篇
  1980年   11篇
  1979年   7篇
  1978年   8篇
  1977年   6篇
  1972年   5篇
  1971年   5篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
71.
The aim of this study was to investigate the ability of epoxides of styrene (styrene-7,8-oxide; SO) and 1,3-butadiene (3,4-epoxy-1-butene; 1,2:3,4:-diepoxybutane) to cause oxidative stress and oxidative DNA damage on human peripheral blood mononuclear cells (PBMCs) and whether a complex mixture of olive oil phenols (OOPE) could prevent these effects. The DNA damage was measured by the single-cell gel electrophoresis (SCGE; comet assay). We found that the DNA damage induced by alkene epoxides could be prevented by N-acetyl-cysteine (10 mM) and catalase (100 U/ml). Alkene epoxides caused a significant (P < 0.05) increase of both peroxide concentration in extra- and intracellular environment and formamidopyrimidine DNA glycosylase (FPG)- and Endonuclease III (ENDO III)-sensitive sites in PBMCs, demonstrating the presence of oxidized bases. OOPE (1 μg of total phenols/ml) was able to prevent the alkene epoxide induced DNA damage both after 2 and 24 h of incubation. In addition, OOPE completely inhibited the SO-induced intracellular peroxide accumulation in PBMCs and prevented the oxidative DNA damage induced by SO, as evidenced by the disappearance of both FPG- and ENDO III-sensitive sites. This is the first study demonstrating the ability of OOPE to prevent the DNA damage induced by alkene epoxides providing additional information about the chemopreventive properties of olive oil.  相似文献   
72.
73.
74.
Telomerase is considered a universal tumor-associated antigen (TAA) due to its high rate of expression by cancers (approximately 90%), and clinical trials are in progress to test the immunotherapeutical efficacy of antitelomerase immunization in patients with cancer. However, the data concerning frequency and functional activity of telomerase-specific cytotoxic T lymphocytes (CTLs) in patients with cancer are few and conflicting, although their knowledge would be mandatory to predict the efficacy of telomerase-specific immunotherapy in selected patients. We performed this study to analyze frequency and cytolytic function of circulating CD8+ T lymphocytes specific for the p540 telomerase peptide in a series of human leukocyte antigen (HLA)-A2+ cancer patients. The results show that most patients with cancer have circulating telomerase-specific CD8+ T lymphocytes, but a high frequency of telomerase-specific CTLs are present only in a fraction of them. Furthermore, CTL lines able to kill telomerase-positive tumor cells, including autologous cancer cells, can be expanded ex vivo from some, but not all, patients with cancer. In conclusion, the results of the study support the development of clinical protocols using telomerase peptides as an immunizing agent. However, they underline the necessity to study single patients immunologically before undergoing vaccination, to select the patients adequately, and to eventually adapt the immunization schedule to the patient's immunologic status.  相似文献   
75.
A plasma factor displaying permeability activity in vitro and possibly determining proteinuria has been hypothesized in idiopathic focal segmental glomerulosclerosis (FSGS). In vitro permeability activity (P(alb)) was determined in sera of five patients with autosomal recessive steroid-resistant nephrotic syndrome (NPHS2), an inherited condition indistinguishable from idiopathic FSGS on clinical grounds, but in which proteinuria is determined by homozygous mutations of podocin, a key component of the glomerular podocyte. All patients had presented intractable proteinuria with nephrotic syndrome; four developed renal failure and received a renal allograft. For comparison, sera from 31 children with nephrotic syndrome were tested. Pretransplant P(alb) was high in all cases (mean 0.81 +/- 0.06), equivalent to levels observed in idiopathic FSGS. Overall, P(alb) did not correlate with proteinuria. The posttransplant outcome was complicated in two patients by recurrence of proteinuria after 10 and 300 d, respectively, that responded to plasmapheresis plus cyclophosphamide. P(alb) levels were high at the time of the recurrence episodes and steadily decreased after plasmapheresis, to reach normal levels in the absence of proteinuria after the seventh cycle. In an attempt to explain high P(alb) in these patients, putative inhibitors of the permeability activity were studied. Coincubation of serum with homologous nephrotic urine reduced P(alb) to 0, whereas normal urine did not determine any change, which suggests loss of inhibitory substances in nephrotic urine. The urinary levels of the serum P(alb) inhibitors apo J and apo E were negligible in all cases, thus suggesting that other urinary inhibitors were responsible for the neutralizing effect. These data indicate that P(alb) is high in NPHS2, probably resulting from loss of inhibitors in urine. Lack of correlation of P(alb) with proteinuria suggests a selective loss of inhibitors. As in idiopathic FSGS, proteinuria may also recur after renal transplantation in NPHS2 patients, and post-transplant proteinuria is associated with high P(alb). The relationship between elevated P(alb) and proteinuria in NPHS2 remains to be determined.  相似文献   
76.
Case reports The authors report their experience about three children (two girls, one boy; average age 1.6 years) with a spontaneous regression of optic gliomas. All of them had a previous diagnosis of neurofibromatosis type 1 (NF 1). None of them underwent surgery or biopsy nor received chemotherapy or radiotherapy. The complete regression was documented by MRI scans performed during a mean follow-up of 6.3 years.Literature review Moreover, the authors analyze the features of the 16 cases previously reported in English literature of spontaneously regressed optic gliomas with an overview of the different therapeutic strategies. The knowledge that this kind of tumor, particularly in young patients, may regress is important in the decision of the best therapeutic approach.  相似文献   
77.
BACKGROUND: The purpose of this paper is to use demographic and clinical data from a large diverse group of outpatients diagnosed with non-psychotic major depression to investigate the validity of the DSM-IV concept of melancholic depression. METHODS: Baseline clinical and demographic data were collected on 1500 outpatients (1456 of whom melancholia could be determined) with non-psychotic major depressive disorder (MDD) participating in the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Depressive symptom severity was assessed by clinical telephone interview using the 17-item Hamilton Rating Scale for Depression (HRS-D17) and the 30-item Inventory of Depressive Symptomatology (IDS-C30). The types and degrees of concurrent psychiatric symptoms were measured using a self report, the Psychiatric Diagnostic Screening Questionnaire (PDSQ), by recording the number of items relevant to each diagnostic category endorsed by study participants. RESULTS: Adjusting for severity of depression (as measured by the total HRS-D17 scores), no differences were found in the rate of melancholic depression by race, marital status, education, employment status, family history of depression, primary care versus specialty care, monthly income, and degree of psychiatric and medical co-morbidity. Melancholic depression was significantly more likely in men than women. Melancholic depression after adjustment for severity was associated with a slightly younger age at study entry, as well as with greater illness severity, and slightly shorter duration of current episode. Hispanic ethnicity was associated with lower melancholic depression rates at the .06 level of significance. CONCLUSIONS: Among outpatients with MDD, melancholic features were less likely in Hispanic patients, but more likely in slightly younger patients and in men. Melancholic features were also related to a slightly shorter current episode. These findings are consistent with the notion that external socio-demographic factors do not play an important role in the pathophysiology of melancholic depression.  相似文献   
78.
BACKGROUND: Insomnia and major depressive disorder (MDD) can coexist. This study evaluated the effect of adding eszopiclone to fluoxetine. METHODS: Patients who met DSM-IV criteria for both MDD and insomnia (n = 545) received morning fluoxetine and were randomized to nightly eszopiclone 3 mg (ESZ+FLX) or placebo (PBO+FLX) for 8 weeks. Subjective sleep and daytime function were assessed weekly. Depression was assessed with the 17-item Hamilton Rating Scale for Depression (HAM-D-17) and the Clinical Global Impression Improvement (CGI-I) and Severity items (CGI-S). RESULTS: Patients in the ESZ+FLX group had significantly decreased sleep latency, wake time after sleep onset (WASO), increased total sleep time (TST), sleep quality, and depth of sleep at all double-blind time points (all p < .05). Eszopiclone co-therapy also resulted in: significantly greater changes in HAM-D-17 scores at Week 4 (p = .01) with progressive improvement at Week 8 (p = .002); significantly improved CGI-I and CGI-S scores at all time points beyond Week 1 (p < .05); and significantly more responders (59% vs. 48%; p = .009) and remitters (42% vs. 33%; p = .03) at Week 8. Treatment was well tolerated, with similar adverse event and dropout rates. CONCLUSIONS: In this study, eszopiclone/fluoxetine co-therapy was relatively well tolerated and associated with rapid, substantial, and sustained sleep improvement, a faster onset of antidepressant response on the basis of CGI, and a greater magnitude of the antidepressant effect.  相似文献   
79.
In patients with primary hyperparathyroidism (PHPT) not suitable for surgical correction, a skeletal protection with bisphosphonates is considered a reasonable option, but the long-term effects after treatment discontinuation are not well known. Sixty postmenopausal women with PHPT were given 400–600 IU vitamin D3 daily and 100 mg neridronate IV every 2 months for 2 years with 2 additional years of follow-up without antiresorptive therapies. Bone mineral density (BMD) progressively rose by 6.7 ± 7.6% (SD) and by 2.9 ± 4.5% at the spine and femoral neck, respectively. During follow-up, mean BMD progressively fell, but after 2 years it was still 3.9 ± 5.5% higher than baseline values at the spine. Bone alkaline phosphatase and serum C-telopeptide of type I collagen decreased significantly within 6 months (28 and 49% versus baseline, respectively) and rose to baseline values within 6–12 months during follow-up. Serum PTH significantly rose from baseline during treatment, but it remained significantly higher than baseline during follow-up. The PTH changes were significantly correlated with serum 25-hydroxyvitamin D (25OHD) levels. In conclusion, in this study we observed that in patients with mild PHPT treatment with bisphosphonates is associated with the expected changes in bone-turnover markers and that the significant increases of both hip and spine BMD are partially maintained for at least 2 years after treatment discontinuation at the vertebral site. The marked increases in serum PTH levels, particularly in subjects with low 25OHD levels, persist after treatment discontinuation and this raises the suspicion that this might reflect a worsening of PHPT.  相似文献   
80.
Clinical risk factors are associated with increased probability of fracture in postmenopausal women. We sought to compare prediction models using self‐reported clinical risk factors, excluding BMD, to predict incident fracture among postmenopausal women. The GLOW study enrolled women aged 55 years or older from 723 primary‐care practices in 10 countries. The population comprised 19,586 women aged 60 years or older who were not receiving antiosteoporosis medication and were followed annually for 2 years. Self‐administered questionnaires were used to collect data on characteristics, fracture risk factors, previous fractures, and health status. The main outcome measure compares the C index for models using the WHO Fracture Risk (FRAX), the Garvan Fracture Risk Calculator (FRC), and a simple model using age and prior fracture. Over 2 years, 880 women reported incident fractures including 69 hip fractures, 468 “major fractures” (as defined by FRAX), and 583 “osteoporotic fractures” (as defined by FRC). Using baseline clinical risk factors, both FRAX and FRC showed a moderate ability to correctly order hip fracture times (C index for hip fracture 0.78 and 0.76, respectively). C indices for “major” and “osteoporotic” fractures showed lower values, at 0.61 and 0.64. Neither algorithm was better than the model based on age + fracture history alone (C index for hip fracture 0.78). In conclusion, estimation of fracture risk in an international primary‐care population of postmenopausal women can be made using clinical risk factors alone without BMD. However, more sophisticated models incorporating multiple clinical risk factors including falls were not superior to more parsimonious models in predicting future fracture in this population. © 2011 American Society for Bone and Mineral Research  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