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   1792篇
  免费   265篇
  国内免费   10篇
耳鼻咽喉   17篇
儿科学   123篇
妇产科学   15篇
基础医学   203篇
口腔科学   43篇
临床医学   301篇
内科学   428篇
皮肤病学   13篇
神经病学   139篇
特种医学   186篇
外科学   229篇
综合类   40篇
预防医学   109篇
眼科学   15篇
药学   126篇
中国医学   5篇
肿瘤学   75篇
  2021年   21篇
  2020年   11篇
  2019年   16篇
  2018年   44篇
  2017年   45篇
  2016年   48篇
  2015年   45篇
  2014年   52篇
  2013年   88篇
  2012年   50篇
  2011年   46篇
  2010年   78篇
  2009年   70篇
  2008年   48篇
  2007年   53篇
  2006年   40篇
  2005年   44篇
  2004年   32篇
  2003年   33篇
  2002年   41篇
  2001年   38篇
  2000年   33篇
  1999年   39篇
  1998年   68篇
  1997年   68篇
  1996年   58篇
  1995年   62篇
  1994年   32篇
  1993年   47篇
  1992年   54篇
  1991年   43篇
  1990年   43篇
  1989年   33篇
  1988年   50篇
  1987年   40篇
  1986年   35篇
  1985年   38篇
  1984年   48篇
  1983年   42篇
  1982年   13篇
  1981年   32篇
  1980年   22篇
  1979年   28篇
  1978年   26篇
  1977年   20篇
  1976年   25篇
  1975年   26篇
  1974年   13篇
  1972年   18篇
  1971年   12篇
排序方式: 共有2067条查询结果,搜索用时 31 毫秒
1.
The effect of olestra on vitamin D status was assessed in a 6-wk, double-blind, placebo-controlled study involving 202 free-living adults. Subjects consumed a total of 20 g/d of olestra or triglycerides in cookies eaten at each meal. A 20-micrograms ergocalciferol capsule was taken with each morning meal. Serum 25-hydroxyergocalciferol (25-OHD2) concentrations rose from approximately 5.7 to 39.0 and 31.7 nmol/L in the placebo and olestra groups, respectively, at week 6. At week 6, 25-OHD2 contributed 46-54% to total serum 25-OHD concentration compared with 11% at baseline. The 19% decrease in serum 25-OHD2 concentrations produced by olestra in this study is equivalent to a decrease of approximately 1.2 nmol/L under nonsupplemented dietary conditions. Ingesting 20 g olestra/d in the diet is thus not expected to affect vitamin D nutritional status.  相似文献   
2.
Tuberous sclerosis is an inherited disorder characterized by a triad of signs--mental retardation, seizures and adenoma sebaceum. The hamartomas that commonly affect multiple organ systems can be seen on plain film radiography. Computed tomography and ultrasonography are useful for assessing whether lesions are present in the abdomen, kidneys and brain. The hamartomas tend to bleed, causing symptoms and prompting the need for evaluation.  相似文献   
3.
Benign intracranial hypertension (BIH) is reported in three children from Australia and one from New Zealand, who were being treated with recombinant human growth hormone (rhGH). Three males and one female, aged between 10.5 and 14.2 y, developed intracranial hypertension within 2 weeks to 3 months of starting treatment. A national database, OZGROW, has been prospectively collecting data on all 3332 children treated with rhGH in Australia and New Zealand from January 1986 to 1996. The incidence of BIH in children treated with growth hormone (GH) is small, 1.2 per 1000 cases overall, but appears to be greater with biochemical GHD (<10IUml -1), i.e. 6.5/1000 (3 in 465 cases), relative risk 18.4, 95% confidence interval 1.9-176.1, than in all other children on the database. The incidence in patients with Turner's syndrome was 2.3/1000 (1 in 428 cases). No cases in patients with partial GHD (10–20 IUml -1) or chronic renal failure were identified. Possible causative mechanisms are discussed. The authors'practice is now to start GH replacement at less than the usual recommended dose of 14IUm-2 week-1 in those children considered to be at high risk of developing BIH. Ophthalmological evaluation is recommended for children before and during the first few months following commencement of rhGH therapy and is mandatory in the event of peripheral or facial oedema, persistent headaches, vomiting or visual symptoms. The absence of papilledema does not exclude the diagnosis.  相似文献   
4.
Paget's disease   总被引:1,自引:0,他引:1  
  相似文献   
5.
In a prospective, randomized, double-blind study, 49 patients underwent lumbar myelography using iotrol (24 patients) or metrizamide (25 patients). The diagnostic imaging adequacy of iotrol was comparable with that of metrizamide. After iotrol myelography, adverse reactions were fewer, less severe, and of shorter duration than were those following metrizamide myelography. Thirteen of 24 patients (54%) receiving iotrol reported some adverse reactions compared with 24 of 25 patients (96%) receiving metrizamide. Five moderate and one severe adverse reaction occurred in the group receiving iotrol. Fourteen moderate and eight severe adverse reactions occurred in the group receiving metrizamide. Thirty-eight patients underwent electroencephalography both before and after myelography (19 iotrol and 19 metrizamide). None of the EEGs obtained after iotrol myelography changed from baseline, while seven of the EEGs obtained after metrizamide myelography showed changes from baseline. Iotrol was judged superior to metrizamide as a contrast medium in this patient population.  相似文献   
6.
Mapping brain size and cortical gray matter changes in elderly depression.   总被引:1,自引:0,他引:1  
BACKGROUND: In elderly depression, volumetric brain imaging findings suggest abnormalities of the frontal lobe, particularly the orbitofrontal cortex, and the hippocampus. No studies to date have mapped cortical abnormalities over the entire brain surface in major depression. Here, we conducted detailed spatial analyses of brain size and gray matter within the cortical mantle in elderly patients with major depression. METHODS: High-resolution, three-dimensional, structural magnetic resonance imaging data and cortical pattern matching methods were used in 24 depressed elderly patients and 19 group-matched controls to measure local brain size and proportions of gray matter at thousands of homologous cortical surface locations. RESULTS: Prominent brain size reductions were observed in the depressed subjects in the orbitofrontal cortex bilaterally. Cortical gray matter measurements revealed significant gray matter increases in the orbitofrontal cortex, adjacent to focal trend level significant decreases of gray matter in the same region. Depressed patients also exhibited significant gray matter increases in parietal cortices, as well as the left temporal cortex. CONCLUSIONS: Complex cortical changes may contribute to the brain size reduction of the orbitofrontal cortex and to the gray matter abnormalities detected in orbitofrontal cortex and temporoparietal cortices, thereby providing a potentially new window into the pathophysiology of elderly depression.  相似文献   
7.
Purpose. The interaction of salmon calcitonin (sCT) and poly (d,l-lactide-co-glycolide) was detected during preparation and evaluation of microspheres. The purpose of this study was to quantitate the extent and nature of the interaction. Methods. Blank microspheres were prepared by an aqueous emulsification solvent extraction technique. Adsorption studies were carried out at six concentrations of sCT and three concentrations of microspheres. Adsorption isotherms were constructed using the Langmuir and Freundlich treatments. Results. Adsorption at 1 mg/ml sCT concentration resulted in almost complete depletion of the peptide from the adsorption medium with the time to reach maximum adsorption decreasing with increasing microsphere concentration. At sCT concentrations below 100 µg/ml, a true equilibrium occurred in 1 hour or less while at higher concentrations (up to 350 µg/ml), a transient equilibrium was reached in 1 to 2 hours, followed by further adsorption of the peptide. The adsorption followed the Langmuir isotherm at concentrations below 200 µg/ml, indicating formation of a monolayer. Multilayer interaction, described by the Freundlich isotherm, occurred at higher concentrations and resulted in complete depletion of sCT from the adsorption medium. The affinity constant during monolayer formation was 0.09 and the plateau surface concentration was 5.1 µg/mg. The multilayer peptide-peptide adsorption showed a lower affinity (0.025) but higher capacity (24 µg/mg) than the monolayer peptide-polymer adsorption. Conclusions. The results show that poly (d,l-lactide-co-glycolide) microspheres have a high adsorption capacity for sCT which must be considered in formulating a controlled delivery product of this peptide.  相似文献   
8.
Bottomley  PA; Lee  Y; Weiss  RG 《Radiology》1997,204(2):403
  相似文献   
9.
Yucatan Pig: An Optimal Hairless Model for a True Random Cutaneous Flap   总被引:1,自引:0,他引:1  
Porcine models have been used extensively for skin flap research because of the established similarity between the cutaneous blood supply of the swine and humans. The Yucatan minipig provides an excellent model for researching the properties of random cutaneous flaps, offering several advantages over other breeds of swine. In this study, a total of 67 random cutaneous dorsal flank flaps measuring 4 × 14 cm were raised on nine Yucatan minipigs. The mean survival length (10.03 ± 1.60 cm) of the nondelayed flaps was greater than others reported in the literature. The well-defined plane between the subcutaneous tissue and the panniculus carnosus facilitated flap elevation consistently above the level of the panniculus carnosus thereby ensuring the creation of a true random cutaneous flap. Furthermore, the hairless nature of the skin, particularly beneficial in studying chemical peels, permits easy visualization and monitoring of any external skin changes. These advantages make the Yucatan minipig a more desirable alternative to other breeds of swine for use in skin flap research.  相似文献   
10.
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