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   8671篇
  免费   443篇
  国内免费   40篇
耳鼻咽喉   136篇
儿科学   520篇
妇产科学   229篇
基础医学   900篇
口腔科学   209篇
临床医学   695篇
内科学   1970篇
皮肤病学   152篇
神经病学   609篇
特种医学   265篇
外科学   1751篇
综合类   170篇
一般理论   2篇
预防医学   373篇
眼科学   191篇
药学   498篇
中国医学   32篇
肿瘤学   452篇
  2023年   71篇
  2022年   219篇
  2021年   332篇
  2020年   201篇
  2019年   233篇
  2018年   271篇
  2017年   180篇
  2016年   243篇
  2015年   250篇
  2014年   365篇
  2013年   496篇
  2012年   650篇
  2011年   657篇
  2010年   383篇
  2009年   316篇
  2008年   502篇
  2007年   560篇
  2006年   543篇
  2005年   488篇
  2004年   445篇
  2003年   385篇
  2002年   317篇
  2001年   140篇
  2000年   127篇
  1999年   88篇
  1998年   44篇
  1997年   28篇
  1996年   34篇
  1995年   39篇
  1994年   34篇
  1993年   31篇
  1992年   59篇
  1991年   55篇
  1990年   32篇
  1989年   46篇
  1988年   34篇
  1987年   24篇
  1986年   27篇
  1985年   20篇
  1984年   23篇
  1983年   15篇
  1982年   8篇
  1981年   21篇
  1980年   14篇
  1979年   10篇
  1978年   10篇
  1977年   10篇
  1973年   7篇
  1971年   7篇
  1967年   14篇
排序方式: 共有9154条查询结果,搜索用时 0 毫秒
71.
72.
PURPOSE: To determine the efficacy and safety of a newly developed concomitant administration of fludarabine and alemtuzumab (FluCam) in patients with relapsed or refractory B-cell chronic lymphocytic leukemia (B-CLL). PATIENTS AND METHODS: A total of 36 patients were treated in this phase II study (median age, 61.47 years; mean number of prior chemotherapies, 2.6; Binet stage C, n = 28). After an initial dose escalation of alemtuzumab over 3 days, alemtuzumab 30 mg and fludarabine 30 mg/m2 were administered on 3 consecutive days. Treatment was repeated after 28 days for up to six cycles. Restaging (following National Cancer Institute criteria) was carried out after cycles 2 and 4 and 1 month after the end of treatment. RESULTS: The overall response rate was 83% (11 complete responses, 19 partial responses, one stable disease, and five progressive diseases). Two patients with progressive disease developed fungal pneumonias, and one patient died as a result of Escherichia coli sepsis. Two subclinical cytomegalovirus reactivations occurred. CONCLUSION: The new FluCam regimen is effective and feasible in patients with relapsed and refractory B-CLL.  相似文献   
73.
BACKGROUND: In previous experiments, we showed that heparin oligosaccharides inhibit the angiogenic cytokine fibroblast growth factor-2. Here, we present the first in vivo study of size-fractionated heparin oligosaccharides in four models of angiogenesis that are progressively less dependent on fibroblast growth factor-2. EXPERIMENTAL DESIGN: Heparin oligosaccharides were prepared using size-exclusion gel filtration chromatography and characterized through depolymerization and strong anion exchange high-performance liquid chromatography. Size-defined oligosaccharides (20 mg/kg/d) were given to mice bearing s.c. sponges that were injected with fibroblast growth factor-2 (100 ng/d). After 14 days, octasaccharides and decasaccharides reduced the microvessel density to levels below control. In a second experiment, HEC-FGF2 human endometrial cancer cells that overexpress fibroblast growth factor-2 were implanted in a hollow fiber placed s.c. in vivo. Oligosaccharides were given at 20 mg/kg/d for 2 weeks and the data again showed that octasaccharides significantly reduced microvessel density around the fiber (P = 0.03). In a more complex model, where angiogenesis was induced by a broad spectrum of growth factors, including vascular endothelial growth factor, we implanted H460 lung carcinoma cells in hollow fibers and treated the animals with oligosaccharides at 20 mg/kg/d over 3 weeks. Octasaccharides reduced the microvessel density to that of control. Preliminary investigation of 6-O-desulfated heparins showed that these also had antiangiogenic activity. RESULTS: Finally, we examined the inhibitory potential of hexasaccharides and octasaccharides given at 20 mg/kg/d and these inhibited the growth of H460 lung carcinoma in vivo. At clinically attainable concentrations, significant anticoagulation (activated partial thromboplastin time, anti-factor Xa, and anti-factor IIa) was not observed in vitro unless species containing > or =16 saccharide residues were investigated. CONCLUSIONS: Thus, our preclinical data show that heparin octasaccharides represent novel antiangiogenic compounds that can be given without the anticoagulant effects of low molecular weight heparin.  相似文献   
74.
Pericardial fluid reflect the composition of cardiac interstitium in myocardial ischemia. This study investigated the value of the pericardial and serum myoglobin (MG) measurements for the diagnosis of perioperative myocardial infarction (MI) after coronary artery bypass grafting (CABG). Postoperative arterial and pericardial blood samples were taken in 64 subjects undergoing elective CABG allocated to two groups according to the 12-lead electrocardiogram (ECG) abnormalities observed during the first postoperative 24h. Group 1=normal and nonspecific ECG abnormalities, and Group 2=perioperative Q-wave MI. The occurrence of perioperative MI was associated with a dramatic increase in both serum and pericardial cardiac troponin I (CTnI) and MG concentrations. Pericardial concentrations were higher than serum concentrations during the first postoperative 24h in all subject. However, pericardial/serum CTnI ratio in subjects in Group 2 was not statistically different from Group 1 at the time of admission to the intensive care unit (ICU) and did not significantly change at time intervals. On the other hand, more than two-fold increase in the pericardial/serum MG ratio was determined for all patients who experienced perioperative Q-wave MI with the lowest value as 2.75, whereas only 1 of 59 patients in group 1 had the ratio higher than 2 with the highest value as 2.15 at the time of admission to the ICU. In conclusion, determination of pericardial/serum MG ratio may be a useful tool for the early diagnosis of the perioperative MI after CABG.  相似文献   
75.
A recently independent state, Timor-Leste, is progressing towards socioeconomic development, prioritizing women empowerment while its increased fertility rate (4.1) could hinder the growth due to an uncontrolled population. Currently, limited evidence shows that indicators of women''s empowerment are associated with fertility preferences and rates. The objective of this study was to assess the association between women empowerment and fertility preferences of married women aged 15 to 49 years in Timor-Leste using nationally representative survey data. The study was conducted using the data of the latest Timor-Leste Demographic and Health Survey 2016. The study included 4040 rural residents and 1810 urban residents of Timor-Leste. Multinomial logistic regression has been performed to assess the strength of association between the exposures indicating women''s empowerment and outcome (fertility preference). After adjusting the selected covariates, the findings showed that exposures that indicate women empowerment in DHS, namely, the employment status of women, house and land ownership, ownership of the mobile phone, and independent bank account status, contraceptive use, and the attitude of women towards negotiating sexual relations are significantly associated with fertility preferences. The study shows higher the level of education, the less likely were the women to want more children, and unemployed women were with a higher number of children. Our study also found that the attitude of violence of spouses significantly influenced women''s reproductive choice. However, employment had no significant correlation with decision-making opportunities and contraceptive selection due to a lack of substantial data. Also, no meaningful data was available regarding decision-making and fertility preferences. Our findings suggest that women''s empowerment governs decision-making in fertility preferences, causing a decline in the fertility rate.  相似文献   
76.
77.
病例介绍患者,男,47岁,由于精神状态改变合并急性肾衰于6月初的一天早上10点送入我院急诊科。该患者在前一天晚上8点与家人共进晚餐时出现行为异常,餐后又开车外出。根据其妻子的描述,当晚回到家时,患者说话含糊不清并出现嗜睡。到晚9点出现呕吐并且昏睡。凌晨3点其妻子叫他无反应,遂拨打急诊中心电话,将患者送至当地医院急诊科。该患者最近没有发热、患病以及抑郁症状。曾患有肠易激综合征(服用了阿托品与地芬诺酯治疗)、慢性背部疼痛和焦虑,对青霉素过敏,没有个人或者家族重要疾病史。患者有吸烟和酗酒史,但近年无饮酒,其妻子确认其没有使…  相似文献   
78.
Zinc nanoparticles (ZnNPs) are among the least investigated NPs and thus their toxicological effects are not known. In this study, tilapia (Oreochromis niloticus) were exposed to 1 and 10 mg/L suspensions of small size (SS, 40–60 nm) and large size (LS, 80–100 nm) ZnNPs for 14 days under semi‐static conditions. Total Zn levels in the intestine, liver, kidney, gill, muscle tissue, and brain were measured. Blood serum glucose (GLU), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and lactate dehydrogenase (LDH) were examined to elucidate the physiological disturbances induced by ZnNPs. Organ pathologies were examined for the gills, liver, and kidney to identify injuries associated with exposure. Significant accumulation was observed in the order of intestine, liver, kidney, and gills. Zn levels exhibited time‐ and concentration‐dependent increase in the organs. Accumulation in kidney was also dependent on particle size; NPs SS‐ZnNPs were trapped more effectively than LS‐ZnNPs. No significant accumulation occurred in the brain (p > 0.05) while Zn levels in muscle tissue increased only marginally (p ≥ 0.05). Significant disturbances were noted in serum GOT and LDH (p < 0.05). The GPT levels fluctuated and were not statistically different from those of controls (p > 0.05). Histopathological tubular deformations and mononuclear cell infiltrations were observed in kidney sections. In addition, an increase in melano‐macrophage aggregation intensity was identified on the 7th day in treatments exposed to LS‐ZnNPs. Mononuclear cell infiltrations were identified in liver sections for all treatments. Both ZnNPs caused basal hyperplasia in gill sections. Fusions appeared in the gills after the 7th day in fish treated with 10 mg/L suspensions of SS‐ZnNPs. In addition, separations in the secondary lamella epithelia were observed. The results indicated that exposure to ZnNPs could lead to disturbances in blood biochemistry and cause histopathological injuries in the tissues of O. niloticus. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1213–1225, 2017.  相似文献   
79.
Pomegranate is a well known fruit for its unique flavor, taste and health benefits. The medicinal properties of this fruits directly associated with the phenolic content present, with great anti-oxidant potential. The research is intended to develop matrix solid phase dispersion method (MSPD) and HPLC quantification of four major anti-oxidant marker constituents (vitamin C, gallic acid, rutin & ellagic acid) in pomegranate molasses samples. The effects of several important experimental parameters like type of dispersant, sample-dispersant ratio, solvents and its volume, time of extraction were investigated. A C18 column with the specification (5?µm, 250?×?4.0?mm) was used for the separation. A gradient flow of mobile phase was selected after many trials containing 0.1%, v/v solution of orthophosphoric acid and acetonitrile. The flow rate was 1.0?mL/min; and the chromatograms were recorded at 254?nm. The validation parameters, like linearity (r2?=?0.9985, 0.9965, 0.9925 & 0.9986), accuracy (100.3, 99.5, 100.9 & 101.9%), intra-day precision (%RSD?=?1.09, 1.02, 1.26 & 0.97), inter-day precision (%RSD?=?1.32, 0.83, 1.07, & 1.15) LOD (0.07, 4.50, 0.45 & 0.40?µg/mL), LOQ (0.095, 9.50, 0.85 & 9.5?µg/mL) and robustness (% RSD?=?0.92, 0.76, 0.81 & 0.83) respectively for vitamin C, gallic acid, rutin & ellagic acid, were found satisfactory as per ICH guidelines.  相似文献   
80.
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