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   2750篇
  免费   115篇
  国内免费   14篇
耳鼻咽喉   98篇
儿科学   138篇
妇产科学   97篇
基础医学   368篇
口腔科学   34篇
临床医学   178篇
内科学   528篇
皮肤病学   118篇
神经病学   220篇
特种医学   59篇
外科学   267篇
综合类   14篇
一般理论   1篇
预防医学   159篇
眼科学   91篇
药学   389篇
中国医学   5篇
肿瘤学   115篇
  2022年   14篇
  2021年   43篇
  2020年   18篇
  2019年   31篇
  2018年   50篇
  2017年   37篇
  2016年   41篇
  2015年   48篇
  2014年   83篇
  2013年   91篇
  2012年   149篇
  2011年   148篇
  2010年   79篇
  2009年   93篇
  2008年   182篇
  2007年   173篇
  2006年   198篇
  2005年   169篇
  2004年   161篇
  2003年   148篇
  2002年   157篇
  2001年   61篇
  2000年   50篇
  1999年   58篇
  1998年   25篇
  1997年   17篇
  1996年   10篇
  1995年   17篇
  1994年   11篇
  1993年   8篇
  1992年   34篇
  1991年   32篇
  1990年   29篇
  1989年   31篇
  1988年   35篇
  1987年   47篇
  1986年   31篇
  1985年   24篇
  1984年   35篇
  1983年   28篇
  1982年   16篇
  1981年   15篇
  1980年   7篇
  1979年   22篇
  1978年   10篇
  1977年   11篇
  1973年   11篇
  1972年   15篇
  1970年   10篇
  1968年   7篇
排序方式: 共有2879条查询结果,搜索用时 15 毫秒
1.
2.
AIM: The aim of the present study was to investigate the influence of endogenous estradiol and estrogen and estrogen-progestin therapies on concentration in pre- and postmenopausal women. MATERIALS AND METHODS: The study groups consisted of 26 women with surgical menopause (mean+/-standard deviation (SD): age 51.8+/-2.6 years, body mass index (BMI) 26.45+/-4.56 kg/m(2)), 54 with natural menopause (mean+/-SD: age 50.5+/-3.0 years, BMI 25.75+/-4.09 kg/m(2)) and 40 premenopausal controls (mean+/-SD: age 48.3+/-2.3 years, BMI 26.23+/-4.12 kg/m(2)). The group with surgical menopause received estradiol transdermally (50 microg/day) and those with natural menopause received additionally medroxyprogesterone acetate (5 mg/day) for the last 12 days of the cycle. Before and after 4 months of therapy, body weight, waist and hip circumferences and blood pressure were measured, and BMI and waist-to-hip ratio (WHR) were calculated. Serum leptin, follicle-stimulating hormone (FSH), estradiol (E(2)), testosterone, prolactin and dehydroepiandrosterone sulfate (DHEAS) were measured prior to and after treatment. RESULTS: Leptin concentrations did not differ statistically among the groups. No correlations between leptin and E(2), FSH, prolactin, testosterone and DHEAS concentrations were found in any of the groups before and after treatment. Leptin level correlated positively with body mass, BMI and hip and waist circumferences in all groups. There were no correlations between leptin and WHR in the pre- and postmenopausal groups. In the premenopausal group and in some postmenopausal groups, serum leptin level correlated with blood pressure. CONCLUSIONS: Endogenous E(2) and androgens in premenopausal women and estrogen and estrogen-progestin therapies in postmenopausal subjects do not influence serum leptin concentrations. Leptin level is related to body mass and BMI, but not to sex hormone status. The distribution of adipose tissue and the type of obesity (android or gynoid) have no influence on serum leptin concentration. The correlation between serum leptin level and blood pressure requires further investigation.  相似文献   
3.
Ultraviolet radiation B (UVB) on the skin induces erythema, inflammation and modifications of the immune system. These changes have been reported after excessive short-term or long-term exposure to broad spectrum UVB. In this study, we examined the effects of local repetitive UVB irradiation of 311 nm wavelength on the skin of seven young volunteers. Skin biopsies were taken before and after UVB irradiation, and we immunohistochemically analyzed the expression of CD1a and HLA-DR antigens of Langerhans cells (LC), the possible infiltration of dermis/epidermis by CD11b macrophages, the modifications or the induction of intercellular adhesion molecule-1 (ICAM-1), E-selectin and vascular cell adhesion molecule-1 (VCAM-1) involved in the binding of leukocytes to the endothelial surface and the development of perivascular infiltrates of LFA-1+ mononuclear cells. We also determined the expression of substance P receptors (SPR) using biotinylated substance P (SPB). Exposure of UVB 311 nm induced a drastic reduction of CD1a+ cells and a moderate increase of HLA-DR+ dendritic cells in the epidermis without infiltration by CD11b macrophages. An increase of the binding of SPB to upper layer epidermal cells was noted in five of seven biopsies. In the dermis, vessel-associated ICAM-1 expression increased and an induction of E-selectin occurred on nearly 20 to 40% of endothelial cells, but VCAM-1 expression remained undetectable. The percentage of LFA-1+ cells did not change significantly after irradiation. These observations may be compatible with a selective role of UVB 311 nm on the skin immune response.  相似文献   
4.
The cellular infiltrate present in human diseased gingiva was analyzed in biopsies from 12 patients with gingivitis or periodontitis. The samples studied had been obtained in the course of surgery at inflammatory sites remaining after institution of periodontal treatment. Histological and immunological techniques were used to identify macrophages, B-cells, plasma-cells, T-cells and T cell subsets, as well as cells expressing class II HLA membrane antigens. T-cells appeared as the predominant population, but plasma-cells were also visualized in nearly all samples. Both OKT4+ and OKT8+ cells were seen in all cases, the latter being more numerous in periodontitis patients. Interdigitating-like cells were observed, positively labelled for class II antigens, as well as macrophages which were more numerous in periodontitis patients. These results suggest the participation of all components of the immune response in gingival disease, in a way resembling chronic recurrent inflammatory diseases.  相似文献   
5.
Facial hemiatrophies are anomalies of the first branchial arch and affect one in 4000-5000 newborns. Bone distraction is the technique of choice for the treatment of these dysmorphoses. Mandibular osteodistraction requires prior determination of the characteristics of the distraction vector whose three components will serve to activate the distractor. The patient, aged 5 years, presented with a right facial hemiatrophy, Grade IB according to the classification of Pruzansky. Tomodensitometric acquisition was obtained with a CT scanner. Software specifically designed for this application allows segmentation of the anatomical elements by a region-growing algorithm. The 3D representation of each element is added to a 3D scene, in which are placed the built-up landmarks necessary for the surgical simulation after 3D cephalometric analysis. The surgical cleavage plane is oriented according to the surgeon's requirements while preserving the predominant anatomical elements. The software allows performance of rotations and translations of the bone segments rendered independently from the cleavage plane. The distances and angles covered during the virtual movement are measured at its conclusion. The aim of moving the bone segments is to render the mandibular occlusion plane parallel to the reference occlusion plane. The vertical growth of the maxilla is realized by secondary recuperation. The distractor used was of an external multidirectional type allowing elongation of the mandibular ramus and mandibular corpus, closure of the goniac angle, and lateralization or medialization of the ramus. On the 15th day, the mandibular angle was reduced by 10 degrees, which allowed closure of the anterior gap and recentering of the incisive areas by a half-cuspid. The patient presented with a complex bone deficit in the three spatial directions, which allowed the development of software for modeling the distraction. Other clinical cases will be necessary to validate this 3D imaging-based technique.  相似文献   
6.
Several studies have been performed to examine the problem of diagnosing gastroduodenal reflux (GDR). No single method is widely accepted. The aim of this work was to evaluate the diagnostic value of gastric pHmetry in this regard. A gastric aspiration probe attached to a combined glass electrode was placed in the stomach of 24 patients, with its distal tip located between 9 and 12 cm below the cardia. One ml samples of gastric juice were taken from 8 of the patients every 30 min for 15 h and as well as, every time a spontaneous alkalinization (SA) (defined by a pH greater than or equal to 4 for at least 1 min) was observed. The pH of each sample was measured by colorimetry whereas the concentration of total biliary acids (CTBA) was evaluated by the fluorimetric method (Kit Sterognost 3 alpha Flu); pH value measured via the intragastric electrode during aspiration was also recorded (protocol A). Continuous gastric aspiration was carried out in the remaining 16 patients for the entire duration of the test (6 h) which was divided into periods of 20 min. Apart from the parameters evaluated during protocol A, the percentage of time during which the stomach had a pH greater than or equal to 4 was recorded, as well as the quantity of total biliary acids collected over the 20 min periods (protocol B). Correlation studies were carried out using the Kendall tau and Spearman tests. Percentages were compared using the chi 2 test.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
7.
Congenital disorders of glycosylation type I (GDG-I) is a class of genetic multisystem disorders characterised by defective glycosylation of glycoproteins. The characteristics and mechanisms of failure to thrive and intestinal diseases present in CDG-I are anectodal. PATIENTS AND METHODS: The aim of this study was to analyse 7 CDG-I (4 CDG-Ia, 2 CDG-Ib and 1 CDG-Ix) with important digestive symptoms and failure to thrive in order to characterise the mechanisms implied. RESULTS: Four children had no skin abnormality or dysmorphia (1 CDG-Ia, 2 CDG-Ib, 1 CDG-Ix). An encephalopathy with cerebellar hypoplasia was present only in the 4 CDG-Ia. Failure to thrive and diarrhea were present during the first month of life in 6 and appeared at 5 years in one CDG-Ia associated to mild or severe hepatopathy in all patients. One CDG-Ia, 1 CDG-Ib, 1 CDG-Ix had an exsudative enteropathy. A positive steatorrhea was present in 3 patients. Five patients had an abnormal small bowel biopsy. Abnormalities were variable: moderate inflammation of the chorion without villous atrophy in 2, intra-enterocyte fat accumulation without villous atrophy in 2, and partial villous atrophy with lymphangectasia in 1. In 2 CDG-Ia the intestinal biopsy was normal. Enteral nutrition in 4 and parenteral nutrition in 2 were effective in 4 patients and 1 patient with an exsudative enteropathy respond to a free fat diet (CDG-Ix). CONCLUSION: The digestive symptoms with failure to thrive is a common feature of CDG-I and could be the first symptoms. The diagnostic should be suspected if no other cause is found. Mechanisms of the intestinal symptoms appear to be multiple such as inflammation, abnormal enterocyte lipid transport or intestinal permeability related to the abnormal glycosylation of intestinal mucosa glycoproteins.  相似文献   
8.
9.
10.
We examined 83 mothers from Szczecin (north-west part of Poland) and their 83 neonates. Concentrations of total and ionized magnesium in maternal and cord serum, as well as total magnesium in hair were determined. Higher levels of total magnesium were noted in neonates (cord serum, hair) than mothers. A positive correlation was ascertained between total magnesium in maternal and cord serum. Magnesium in maternal hair correlated negatively with ionized magnesium in cord serum. Male neonates demonstrated higher levels of magnesium in cord blood and hair than females. There was no effect of maternal age, education level, or number of past pregnancies on the concentration of magnesium in mothers or neonates.  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