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   6102篇
  免费   375篇
  国内免费   42篇
耳鼻咽喉   30篇
儿科学   152篇
妇产科学   167篇
基础医学   1007篇
口腔科学   79篇
临床医学   506篇
内科学   1602篇
皮肤病学   276篇
神经病学   582篇
特种医学   142篇
外科学   460篇
综合类   12篇
一般理论   2篇
预防医学   355篇
眼科学   36篇
药学   374篇
  3篇
中国医学   26篇
肿瘤学   708篇
  2024年   14篇
  2023年   62篇
  2022年   150篇
  2021年   215篇
  2020年   127篇
  2019年   174篇
  2018年   199篇
  2017年   131篇
  2016年   151篇
  2015年   202篇
  2014年   257篇
  2013年   300篇
  2012年   465篇
  2011年   527篇
  2010年   287篇
  2009年   241篇
  2008年   399篇
  2007年   387篇
  2006年   424篇
  2005年   373篇
  2004年   350篇
  2003年   304篇
  2002年   292篇
  2001年   30篇
  2000年   23篇
  1999年   41篇
  1998年   57篇
  1997年   58篇
  1996年   49篇
  1995年   47篇
  1994年   34篇
  1993年   30篇
  1992年   17篇
  1991年   15篇
  1990年   12篇
  1989年   17篇
  1988年   13篇
  1987年   6篇
  1986年   6篇
  1985年   4篇
  1984年   7篇
  1983年   4篇
  1981年   6篇
  1980年   4篇
  1979年   3篇
  1977年   4篇
  1974年   1篇
排序方式: 共有6519条查询结果,搜索用时 0 毫秒
101.
This trial assessed the rate of virological failure at 48 weeks in adult human immunodeficiency virus (HIV) type 1-infected patients assigned indinavir/ritonavir (Idv/Rtv; 800/100 mg 2 times daily) or saquinavir/ritonavir (Sqv/Rtv; 1000/100 mg 2 times daily) in an open-label, randomized (1:1), multicenter, phase 4 design. Three hundred six patients began the assigned treatment. At 48 weeks, virological failure was seen in 43 (27%) of 158 and 37 (25%) of 148 patients in the Idv/Rtv and Sqv/Rtv arms, respectively. The time to virological failure did not differ between study arms (P=.76). When switching from randomized treatment was counted as failure, this was seen in 78 of 158 patients in the Idv/Rtv arm, versus 51 of 148 patients in the Sqv/Rtv arm (P=.009). A switch from the randomized treatment occurred in 64 (41%) of 158 patients in the Idv/Rtv arm, versus 40 (27%) of 148 patients in the Sqv/Rtv arm (P=.013). Sixty-four percent of the switches occurred because of adverse events. A greater number of treatment-limiting adverse events were observed in the Idv/Rtv arm, relative to the Sqv/Rtv arm. In conclusion, Rtv-boosed Sqv and Idv were found to have comparable antiretroviral effects in the doses studied.  相似文献   
102.
Both n-6 and n-3 polyunsaturated fatty acids are dietary fats important for cell function, being involved in several physiologic and pathologic processes, such as tumorigenesis. Linoleic acid and conjugated linoleic acid, its geometrical and positional stereoisomer, were tested on several human tumor cell lines originating from different tissues and with different degrees of malignancy. This was to provide the widest possible view of the impact of dietary lipids on tumor development. While linoleic acid exerted different effects, ranging from inhibitory to neutral, even promoting growth, conjugated linoleic acid inhibited growth in all lines tested and was particularly effective against the more malignant cells, with the exception of mammary tumor cells, in which behavior was the opposite, the more malignant cell line being less affected. The inhibitory effect of conjugated linoleic acid on growth may be accompanied by different contributions from apoptosis and necrosis. The effects of conjugated linoleic acid on growth or death involved positive or negative variations in PPARs. The important observation is that a big increase of PPARalpha protein occurred in cells undergoing strong induction of apoptosis, whereas PPARbeta/delta protein decreased. Although PPARalpha and PPARbeta/delta seem to be correlated to execution of the apoptotic program, the modulation of PPARgamma appears to depend on the type of tumor cell, increasing as protein content, when inhibition of cell proliferation occurred. In conclusion, CLA may be regarded as a component of the diet that exerts antineoplastic activity and its effect may be antiproliferative or pro-apoptotic.  相似文献   
103.
BACKGROUND: To the authors' knowledge, no effective medical therapy currently is available for advanced chordoma. Imatinib mesylate is a tyrosine kinase inhibitor targeting platelet-derived growth factor receptor-beta (PDGFRB), BCR-ABL, and KIT. METHODS: Six patients with advanced chordoma were treated with imatinib mesylate at a dose of 800 mg daily. In all patients, the tumor was found to be positive for PDGFRB, and in four patients PDGFRB was shown to be phosphorylated/expressed. RESULTS: After a treatment period of > or = 1 year, overt tumor liquefaction was evident on computed tomography (CT) scan in the first patient. In previous months, a decrease in contrast enhancement on magnetic resonance imaging (MRI) and a decrease in glucose uptake on positron emission tomography (PET) were detected. Similar signs on MRI and PET were observed in subsequent patients, who had a shorter treatment period. One of these patients initially was removed from therapy and then was readmitted to therapy because of difficulties with regard to tumor response assessment; 1 month after the reinitiation of therapy, an overt decrease in tumor density was visible on CT scan in this patient. In four of five symptomatic patients, a subjective improvement was observed early in the course of treatment. The first patient died after 17 months, with a sizeable, mostly liquefied mass. Another patient died early, apparently of unrelated causes. The remaining patients were on therapy at the time of last follow-up. CONCLUSIONS: Imatinib mesylate has been found to have antitumor activity in patients with chordoma. This activity might be mediated by inactivation of PDGFRB. Tumor response manifests through patterns that are similar to those observed in patients with gastrointestinal stromal tumors who respond to molecular-targeted therapy, but evolves more slowly. The benefit to the patient entailed by this pattern of tumor response in chordoma needs to be elucidated, but may be limited in the presence of significant local disease.  相似文献   
104.
Since 2001, 50 breast cancer patients, for whom extensive lung/heart involvement was expected from the use of conventional tangential 2-field technique (2F) owing to complex anatomies, were irradiated using a 3-field conformal technique (3F). Dose plans were designed for both 3F and 2F and a dose volume histogram analysis on ipsilateral lung, heart, and target was conducted. The 3F technique allowed a significant reduction in ipsilateral lung irradiation: mean dose dropped from 16.0±3.8 (2F) to 12.0±2.7 Gy (3F) and V45Gy from 20.7±6.8 (2F) to 3.2±2.9% (3F). Similarly, in patients irradiated to the left breast, heart mean dose was reduced from 8.1 Gy (2F) to 6.8 Gy (3F) and D15% from 19.0 Gy to 14.0 Gy. All differences reached a high degree of significance. The target coverage was not clinically compromised since the slight reduction using 3F compared with 2F is limited to V95% while V90% difference, even if statistically significant, is small: 98.2±1.8% (3F) and 98.8±1.6 (2F). A preliminary report on clinical follow up is also included; with a mean follow up of 15.8 months, no pulmonary or cardiac complications were observed.  相似文献   
105.
106.
107.
108.
109.
OBJECTIVE: To demonstrate that thorough antenatal and postnatal investigations are helpful in any genetic syndrome. CASE REPORT: A woman without a specific risk had a finding of hyperechogenic foci at ultrasound. Karyotype on fetal blood was 47, XY+21 and extensive biochemical investigation revealed abnormal liver function. Given the suspicion of a coincidental hepatic compromise, targeted postmortem examination was performed, which showed hepatic fibrosis, megakaryocytes proliferation and invasion of sinusoid capillaries, all suggestive of a transient myeloproliferative disorder. CONCLUSION: When compared with chorionic villous and amniotic fluid sampling, fetal blood allows the collection of additional data, which may help in understanding the pathological process behind an apparently serendipitous association.  相似文献   
110.
OBJECTIVE: To investigate whether levels of plasma tyrosine and tryptophan, precursors of brain catecholamine and serotonin neurotransmitters, respectively, and other essential amino acids (EAA) may return to normal in patients with severe traumatic brain injury (TBI) after 2 months in a hospital rehabilitation center. DESIGN: Peripheral plasma concentrations of tyrosine, tryptophan, and other EAAs in subjects with severe TBI, both at admission (44+/-11d postinjury) and at discharge from the center (110+/-15d after acute event) were compared with concentrations in control subjects. SETTING: Tertiary care rehabilitation setting in Italy. PARTICIPANTS: Ten men (26.6+/-12.6y) with TBI and 6 healthy subjects (controls) matched for age, sex, voluntary loss of body weight, and sedentary lifestyle. INTERVENTIONS: Not applicable. Main Outcome Measures: Concentrations of brain neurotransmitter precursor amino acids and of EAA. RESULTS: On admission, patients had lower plasma tyrosine, leucine, valine, methionine, and phenylalanine concentrations than did control subjects. The plasma concentrations of tryptophan were similar in the 2 groups. These amino acid abnormalities were still present at discharge. CONCLUSION: The levels of plasma tyrosine and many EAA in patients with TBI did not recover by discharge (110+/-15d) from rehabilitation. Plasma tryptophan concentrations were similar in patients and controls.  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