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   1277篇
  免费   81篇
  国内免费   7篇
耳鼻咽喉   3篇
儿科学   29篇
妇产科学   6篇
基础医学   191篇
口腔科学   15篇
临床医学   129篇
内科学   354篇
皮肤病学   42篇
神经病学   85篇
特种医学   22篇
外科学   132篇
综合类   5篇
预防医学   147篇
眼科学   17篇
药学   123篇
中国医学   2篇
肿瘤学   63篇
  2024年   1篇
  2023年   11篇
  2022年   5篇
  2021年   32篇
  2020年   12篇
  2019年   37篇
  2018年   58篇
  2017年   25篇
  2016年   30篇
  2015年   39篇
  2014年   34篇
  2013年   70篇
  2012年   143篇
  2011年   111篇
  2010年   66篇
  2009年   39篇
  2008年   92篇
  2007年   74篇
  2006年   92篇
  2005年   100篇
  2004年   84篇
  2003年   90篇
  2002年   70篇
  2001年   7篇
  2000年   5篇
  1999年   9篇
  1998年   2篇
  1997年   3篇
  1996年   2篇
  1995年   2篇
  1993年   1篇
  1992年   2篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1987年   1篇
  1986年   1篇
  1984年   1篇
  1983年   2篇
  1980年   1篇
  1977年   1篇
  1974年   2篇
  1973年   1篇
排序方式: 共有1365条查询结果,搜索用时 15 毫秒
81.
This study was designed to investigate the possible effects of consuming Na-rich carbonated mineral water on bone remodelling and urinary mineral excretion in postmenopausal women. Women (n 18) included were amenorrhoeic (>1 year), healthy and not obese (BMI <30 kg/m2). No woman was taking oestrogen replacement therapy, mineral and vitamin supplements, phyto-oestrogens or medications known to affect bone and lipid metabolism. In two consecutive interventions that lasted 8 weeks each, women drank 1 litre of control mineral water daily and 1 litre of carbonated mineral water, rich in Na, HCO3- and Cl-, daily. Body weight and height were measured, BMI was calculated and blood pressure was measured. Blood samples were taken from fasting subjects and serum obtained to analyse the biochemical bone markers, procollagen I amino-terminal propeptide (PINP) and beta-carboxy-terminal telopeptide of collagen (beta-CTX). At the end of each period, 24 h urine samples were collected to determine Ca, Mg, P, Na+, K+, Cl-, urine excretion and urinary pH. No changes in body weight, BMI or blood pressure were observed during the experimental period. Ca excretion was lower after the intake of carbonated water than after intake of the control water (P=0.037) while P excretion was higher (P=0.015). Total urine, Na and Cl- excretion did not differ between the two periods but urinary pH was increased after the intake of carbonated mineral water. PINP and beta-CTX did not differ between the two periods. Daily consumption of 1 litre of Na-rich carbonated mineral water for 8 weeks does not affect bone remodelling in healthy postmenopausal women.  相似文献   
82.
We investigated the intestinal transport of D-glucose (D-Glc) and 3 essential amino acids in a model of intestinal inflammation, and the effects of dietary supplementation with animal plasma proteins on this function. Wistar Lewis rats were fed a diet containing an isonitrogenous amount of milk protein (control group) or a diet supplemented with either spray-dried animal plasma (SDAP) or immunoglobulin concentrate (IC) from porcine plasma, from d 21 of life (weaning) until d 35. On d 30 and 33, rats were challenged intraperitoneally with Staphylococcus aureus enterotoxin B (SEB; groups SEB, SEB-SDAP, and SEB-IC) and on d 35, brush border membrane vesicles (BBMVs) were prepared and used for transport and binding studies. Administration of SEB reduced D-Glc transport across sodium glucose transporter 1 [SGLT1; 20% reduction in maximal transport rate (Vmax); P < 0.05], without affecting the Michaelis constant (Km). The results from specific phlorizin binding, Western blot, and immunohistochemistry supported the view that the effects of SEB are due to reduced expression of D-Glc transporters in the apical membrane. SEB increased the passive diffusion constant (Kd) for D-Glc 3-fold (P < 0.05). SEB did not affect mediated or passive amino acid fluxes of L-leucine, L-methionine, or L-lysine. Dietary SDAP increased the D-Glc Vmax in the SEB group without affecting the passive component. Changes in d-Glc Vmax due to SEB and to the dietary treatments were correlated with changes in the number of SGLT1 transporters present in the BBMVs (r = 0.9468; P < 0.05). Dietary IC had no observed effect. We estimate that, in rats challenged with SEB, SDAP supplementation can increase glucose absorption by 8-9% during the interdigestive periods.  相似文献   
83.
The emergence of clonal chromosomal abnormalities in Philadelphia-negative cells during treatment with imatinib in patients with Philadelphia-positive chronic myeloid leukemia has been reported. We add information to this issue presenting a series of 29 patients in complete cytogenetic response after imatinib treatment, three of whom developed clonal aberrations.  相似文献   
84.
According to some authors the obsessive-compulsive (OC) spectrum includes on one extreme, the Obsessive-Compulsive Disorder (OCD) and on the other extreme the most impulsive behaviors. This is a controversial idea and other authors define the OC spectrum in different ways. The serotonin transporter (5-HTT) gene is one of the main genes that control serotonergic function. A polymorphism in the promoter area of this gene classifies subjects with low expression as S individuals (s/s or s/l) and subjects with high expression as L individuals (l/l). This polymorphism was studied in female OCD patients (n = 24), non-impulsive controls (n = 112) and impulsive suicidal patients (n = 118) to support the OC spectrum hypothesis from a genetic perspective. A linear association exists among the serotonin transporter promoter functional genotypes (S versus L individuals) (chi2 linear by linear association = 8.9; df = 1; p = 0.003). The frequency of S individuals (s/l or s/s) was lowest in OCD (54%, 13/24); intermediate in non-impulsive controls (71%, 80/112) and highest in impulsive suicide attempters (82%, 96/117). More importantly, future studies need to consider that genetics may be related to behavioral dimensions (compulsivity to impulsivity) instead of to specific psychiatric disorders defined in clinical terms.  相似文献   
85.
86.
87.
BACKGROUND: Bone loss occurs during the first 6 months after renal transplantation (RT), and corticosteroid therapy plays an important role. Although calcium plus vitamin D administration prevents corticosteroid-induced osteoporosis, its use in RT recipients is limited by the risk of hypercalcemia. METHODS: This double-blind, randomized, and controlled prospective intervention trial examined the effect of intermittent calcitriol (0.5 microg/48 h) during the first 3 months after RT, plus oral calcium supplementation (0.5 g/day) during 1 year with calcium supplementation alone. The primary outcome measure was the change in bone mineral density (BMD) at 3 and 12 months after RT; we also explored whether the effect of calcitriol on BMD was different among vitamin D receptor (VDR) genotypes (BsmI). Forty-five recipients were randomized to calcitriol therapy (CT) and 41 were randomized to placebo (PL). RESULTS: Both groups had a similar degree of pre-existing hyperparathyroidism (197 +/- 229 vs. 191 +/- 183 pg/mL), but a more pronounced decrease of parathyroid hormone (PTH) levels after RT was observed in CT patients (at 3 months: 61.4 +/- 42.2 vs. 85.7 +/- 53.1 pg/mL, P= 0.02; at 12 months: 67.3 +/- 33.7 vs. 82.6 +/- 37 pg/mL; P= 0.08). CT patients preserved their BMD at the total hip significantly better than those on PL (3 months: 0.04 +/- 3.3 vs. -1.93 +/- 3.2%, P= 0.01; 12 months: 0.32 +/- 4.8 vs. -2.17 +/- 4.4%, P= 0.03); significant differences were noted at the intertrochanter, trochanter, and Ward's triangle. Differences did not reach significance at the femoral neck. Two CT patients (4.4%) and 4 PL patients (9.8%) developed a hypercalcemic episode during the first 3 months after RT. The effect of CT on BMD at 3 months was more prominent in recipients with the at-risk allele of the VDR gene (P= 0.03). CONCLUSION: Therapy with low-dose calcium supplements during 1 year, plus intermittent calcitriol for 3 months after RT, is safe, decreases PTH levels more rapidly, and prevents bone loss at the proximal femur; a more pronounced effect is seen in recipients with at least one at-risk allele of the VDR genotype.  相似文献   
88.
Acute bacterial sinusitis is usually a clinical diagnosis. Orbital complications require emergent evaluation with computed tomography. Using the orbital septum as an anatomic landmark, such infections can be classified as pre- or postseptal and treated with the most adequate therapy, ie, oral or intravenous antibiotics or surgical endonasal drainage. Intracranial complications can be seen in 3.7% to 11% of these patients, often with subtle clinical symptoms and signs. Radiologists play a decisive role in the final management of these patients and should be familiar with the most relevant complications. In this article, we present a retrospective review of all pediatric patients referred to our department for paranasal sinuses and orbital computed tomography because of acute complicated bacterial sinusitis. They were studied with an emergent enhanced facial and cranial computed tomography within 24 hours of admission, followed by magnetic resonance imaging when intracranial complications were suspected. Particular emphasis is placed on the imaging algorithm and the most relevant complications; we correlate imaging findings with clinical and bacteriological data.  相似文献   
89.
An ultrastructural and quantitative study of the age-related changes occurring in the relay neurons of the dorsal lateral geniculate nucleus (dLGN) was carried out using male Wistar rats aged 3, 18, 24, and 28 months. Morphometric techniques were used to obtain data regarding cellular activity including soma, nuclear, and nucleolar size. Volume fractions for rough endoplasmic reticulum (RER), mitochondria, and lipofuscin, as well as numbers and sizes of mitochondria and dense bodies (DB) was also calculated. Among the few alterations found in the perikaryon, we can highlight the redistribution and fragmentation of RER and an increase and progressive aggregation of lipofuscin. Quantitative data show a significant decrease in the volume of the soma (-42.77%) and the nucleus (-33.66%), and in the volume fraction of the RER (-18.81%) and mitochondria (-10.16%). A significant increase in lipofuscin (+213.29%), and variations in size and number of mitochondria and dense bodies were also found. Some histophysiological considerations about the findings are discussed. The findings lead to the conclusion that a relative degree of morphological stability is exhibited by relay neurons, although the quantitative data show evident intracellular changes, especially from 24 to 28 months. These changes suggest that accompanying physiological alterations may occur, with putative effects on visual function during ageing.  相似文献   
90.
The aim of this study was to determine the potential modulatory effects of diets supplemented with spray-dried animal plasma (SDAP) or immunoglobulin concentrates (IC) on the immune response of rats challenged with Staphylococcus aureus enterotoxin B (SEB). Lewis rats were fed diets containing 80 g of SDAP/kg diet, 22.7 g of IC/kg diet, or milk proteins (Control diet) from postnatal d 21 (weaning) for 14 d. On d 30 and 33, rats were given SEB (0.5 mg/kg body weight; i.p.). Organized gut-associated lymphoid tissue (GALT) populations, intestinal secretion, mucosal and serum immunoglobulin concentrations, and neutrophil infiltration were studied. On d 35, blood was collected under anesthesia and samples of intestinal mucosa, Peyer's patches, mesenteric lymph nodes (MLN), and spleen were taken. SEB increased the water content of feces, which was prevented by diets containing either SDAP (P < 0.002) or IC (P < 0.001), indicating that plasma protein-supplemented diets can reverse the SEB-induced secretory response. In Peyer's patches, the diet containing SDAP partially prevented the SEB-induced increase in T lymphocytes (P < 0.1) and reduced the percentage of activated T helper cells (P < 0.05). In MLN, activated T lymphocytes were increased by SEB but they were not affected by diet. No effects of SEB or dietary supplementation on mucosal IgA and serum IgA and IgG were observed. The effects of SDAP supplementation on the lymphocyte populations of GALT in rats challenged with SEB support the view that SDAP can modulate the immune response and suggest that plasma protein supplementation can prevent GALT from possible activation by luminal bacterial superantigens.  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