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   962篇
  免费   33篇
  国内免费   3篇
耳鼻咽喉   1篇
儿科学   73篇
妇产科学   11篇
基础医学   82篇
口腔科学   25篇
临床医学   84篇
内科学   225篇
皮肤病学   22篇
神经病学   17篇
特种医学   283篇
外科学   50篇
综合类   10篇
预防医学   32篇
眼科学   4篇
药学   28篇
中国医学   1篇
肿瘤学   50篇
  2023年   2篇
  2022年   2篇
  2021年   2篇
  2020年   1篇
  2018年   11篇
  2017年   9篇
  2016年   7篇
  2015年   10篇
  2014年   15篇
  2013年   17篇
  2012年   14篇
  2011年   6篇
  2010年   33篇
  2009年   38篇
  2008年   22篇
  2007年   14篇
  2006年   17篇
  2005年   13篇
  2004年   11篇
  2003年   18篇
  2002年   8篇
  2001年   9篇
  2000年   10篇
  1999年   14篇
  1998年   49篇
  1997年   66篇
  1996年   49篇
  1995年   41篇
  1994年   50篇
  1993年   51篇
  1992年   12篇
  1991年   13篇
  1990年   14篇
  1989年   39篇
  1988年   41篇
  1987年   32篇
  1986年   33篇
  1985年   27篇
  1984年   12篇
  1983年   24篇
  1982年   17篇
  1981年   19篇
  1980年   21篇
  1979年   14篇
  1978年   18篇
  1977年   17篇
  1976年   15篇
  1975年   19篇
  1973年   1篇
  1948年   1篇
排序方式: 共有998条查询结果,搜索用时 15 毫秒
1.
Epigastric impedance was used to measure the gastric emptying patterns of a liquid non-caloric meal (5 mL water kg−1) in 30 healthy newborn infants. Twenty-six mature infants were examined in the first eight days of life, and four preterm infants were examined within 6 weeks after birth. The recordings consisted of two components: the emptying signal (the DC component), and a phasic 3 cycles per minutes (CPM) signal (the AC component). In some of the infants the phasic 3 CPM signal was also seen during the fasting state.
For mature infants the median half emptying time (T50) was 6.9 min. For a second meal given within one hour after the first meal the half emptying time was 5.5 min ( P  < 0.01). In preterm infants the emptying times were not significantly different from mature infants.
Day-to-day variation was low with a coefficient of variation of 17% in nine infants.
A periodic change of the impedance signal, the phasic 3 CPM signal, was observed after a meal in 24 of the infants. The median frequency was 3.0 CPM in 20 mature and 2.9 CPM in four preterm infants. In nine infants a phasic 3 CPM signal was also observed during the fasting state, with a median frequency of 2.9 CPM.
Measurement of gastric emptying pattern with epigastric impedance is a simple investigation for the evaluation of gastric emptying time and phasic activity in mature and preterm infants. However, the method is sensitive to spontaneous movements of the children, resulting in non-valid measurements in around one fourth of the infants.  相似文献   
2.
3.
4.
OBJECTIVE: The aim was to establish the potential efficacy, tolerabilityand side-effect profile of electromagnetic therapy as an adjunctto conventional dressings in the treatment of venous leg ulcers. METHOD: A prospective, randomized, double blind controlled clinicaltrial was carried out in a dedicated leg ulcer clinic basedin one urban general practice. Nineteen patients with leg ulcersof confirmed venous aetiology were assessed. The main outcomemeasures were rate and scale of venous leg ulcer healing, changesin patient-reported pain levels, quality of life, degree ofmobility, side effect profile and acceptability to patientsand staff. RESULTS: Sixty-eight per cent of patients attending this dedicated clinicachieved improvements in the size of their ulcer (4, 21%, healedfully) and in reduced pain levels (P < 0.05) during the trial,despite the chronicity of ulcer histories. Patients treatedwith electromagnetic therapy at 800 Hz were found at day 50to have significantly greater healing (P < 0.05) and paincontrol (P < 0.05) than placebo therapy or treatment with600 Hz. All patients reported improved mobility at the end ofthe study. The electromagnetic therapy was well tolerated bypatients, with no differences between groups in reporting adverseevents, and proved acceptable to staff. CONCLUSION: Despite the small numbers in this pilot study, electromagnetictherapy provided significant gains in the healing of venousleg ulcers and reduction in pain. Keywords. Electromagnetic therapy, RCT, leg ulcers, primary care.  相似文献   
5.
Menstrual cycle and appetite control: implications for weight regulation   总被引:1,自引:0,他引:1  
Hormonal fluctuations associated with the menstrual cycle influence appetite control and eating behaviour. Energy intake varies during the reproductive cycle in humans and animals, with a periovulatory nadir and a luteal phase peak. Patterns of macronutrient selection show less consistency but a number of studies report carbohydrate cravings in the premenstrual phase, particularly in women with premenstrual syndrome. The cyclical nature of food cravings are frequently, but not invariably, associated with depression. Fluctuations in appetite, cravings and energy intake during the menstrual cycle may occur in parallel with cyclical rhythms in serotonin, which can be accompanied by affective symptoms. The premenstrual phase can be considered as a time when women are especially vulnerable to overconsumption, food craving and depression; this is often associated with low serotonin activity.   相似文献   
6.
Superoxide, an agent which attenuates the half-life of nitric oxide, is metabolized and synthesized by superoxide dismutase (SOD) and xanthine oxidase, respectively. Over the last few years much work has focused on the role of nitric oxide in human parturition. The aim of this study was to determine whether the onset of human parturition is associated with a change in the expression of copper/zinc superoxide dismutase (Cu/Zn SOD), manganese superoxide dismutase (Mn SOD) or xanthine oxidase within the uterus. Samples of myometrium, placenta, decidua and fetal membranes were obtained from women before and after the onset of labour at term. Immunocytochemistry was used to localize Cu/Zn SOD, Mn SOD and xanthine oxidase and measure SOD enzyme activity. Cu/Zn and Mn SOD-like immunoreactivity was detected in syncytiotrophoblast cells, villous stromal cells and endothelial cells of blood vessels in the placenta. In the myometrium Cu/Zn and Mn SOD were localized to myocytes and endothelial cells and to some vascular smooth muscle cells. In the fetal membranes we observed staining for Cu/Zn SOD and Mn SOD in the amnion, chorion, extravillous trophoblast and decidua. There was no difference in SOD enzyme activity or staining intensity for SOD between different cell types before and during labour. Xanthine oxidase immunoreactivity was identified in each of the tissues examined and again there was no difference in immunostaining in tissues obtained from women delivered before or after the onset of labour. These results show that the pregnant uterus is capable of both synthesizing and degrading superoxide and suggest that superoxide dismutase and xanthine oxidase may play a role in the maintenance of uterine quiescence during pregnancy, but not in the initiation of parturition.   相似文献   
7.
The classical complement activation cascade of the immune system is initiated by multivalent binding of its first component, C1q, to the Fc region of immunoglobulins in immune complexes. The C1q binding site on mouse IgG2b has been shown to contain the amino acids Glu 318, Lys 320 and Lys 322 in the C(H)2 domain (Duncan, A.R., Winter, G.,1988. The binding site for C1q on IgG. Nature 322 738-740). Identical or closely related motifs are found on all IgGs in all species, and the binding site has therefore been thought to be universal. However, the results from another study indicate that the site is different in human IgG1 molecules (Morgan, A., Jones, N.D., Nesbitt, A.M., et al., 1995. The N-terminal end of the C(H)2 domain of chimeric human IgG1 anti-HLA-DR is necessary for C1q, Fc gamma RI and Fc gamma RIII binding. Immunology 86 319-324). To determine the site(s) responsible for complement activation in anti-NIP-mouse/human IgG3 antibodies, we have mutated amino acids Lys 276, Tyr 278, Asp 280, Glu 318, Lys 320 and Lys 322 in two beta-strands in the C(H)2 domains of human IgG3. In addition, we mutated the Glu 333, which resides in close proximity to the postulated C1q-binding site of mouse IgG2b, as well as Leu 235 in the lower hinge region. All mutants were tested in Antibody Dependent Complement Mediated Lysis (ADCML)(4) assays, where the antigen concentration on target cells was varied and human serum was complement source. Only the mutants that lacked the positively charged side chain of lysine in position 322 showed strong reduction in ADCML, particularly at low antigen density on target cells. Alanine scanning of positions 318 and 320 did not affect ADCML, contrary to what was observed for mouse IgG2b. Neither did a leucine to glutamic acid mutation in position 235 have the effect that has been reported for human IgG1. These results suggest that the complement binding site on human IgG3 molecules is different from that found on mouse IgG2b, and possibly on human IgG1 as well. Thus the contact site may not be conserved.  相似文献   
8.
Hydrosalpinges adversely affect markers of endometrial receptivity   总被引:22,自引:10,他引:22  
While in-vitro fertilization (IVF) was initially developed in women with tubal factor infertility, recent clinical studies have suggested that the presence of hydrosalpinges lowers implantation and pregnancy rates. We postulated that these hydrosalpinges cause impaired endometrial receptivity. A total of 103 women with hydrosalpinges were prospectively evaluated, and compared with 55 infertile and 44 fertile controls. All women had endometrial biopsies during the window of implantation, analysed by conventional histological criteria, and also stained for three integrin markers of endometrial receptivity (alpha1beta1, alpha4beta1 and alpha vbeta3). Women with hydrosalpinges (cases) expressed significantly less of the alpha vbeta3 integrin compared with controls. There was no difference in expression of alpha1beta1 or alpha4beta1 among groups. A significantly greater number of cases had out of phase histology and missing alpha vbeta3 (type I defects) and absent integrin expression despite normal histological maturation (type II) defects, compared with controls. Of 20 women with impaired endometrial receptivity who were also biopsied after hydrosalpinx surgery, 70% demonstrated increased alpha vbeta3 expression. Seventy-seven percent of type I and 57% of type II defects were corrected postoperatively. Using markers of endometrial receptivity, this study demonstrates that inflammatory hydrosalpinges have an adverse effect on endometrial receptivity, which in some cases may be overcome by surgical treatment of the hydrosalpinx.   相似文献   
9.
Summary This study investigated the effect of tilt and observer reliability on radiographic measurements of the position of a prosthetic acetabular cup in seven dry bone pelves using the teardrop as a landmark. Coronal or sagittal tilt of more than five degrees was easily recognisable and there was effectively no observer variation in the measurements up to this limit. In addition, 90 out of 100 randomly selected antero-posterior pelvic radiographs from an outpatient department were not significantly rotated and 93 demonstrated a clearly defined teardrop. Measurements about the teardrop on routine radiographs are therefore sufficiently accurate to allow assessment of prosthetic position.
La valeur du sourcil cotyloidien comme repère d'analyse radiologique
Résumé Cette étude, conduite sur 7 bassins secs, apprécie l'effet de l'inclinaison du bassin sur la qualité de l'analyse radiographique de la position d'une cupule prothétique de hanche en utilisant le sourcil cotyloïdien comme repère. Une inclinaison du bassin dans les plans coronal et sagittal est aisément détectable et il n'existe pas de variation d'analyse entre les différents observateurs en dessous de 5° d'inclinaison. De plus, sur 100 radiographies antéro-postérieures de bassin choisies au hasard dans les dossiers de consultation, 90 avaient été réalisées sans incidence particulièrement adaptée et l'on pouvait repérer facilement le sourcil sur 93% d'entre elles. Les mesures faites sur des radios de routine sont donc suffisamment précises pour permettre l'évaluation de la position d'une prothèse à partir du sourcil cotyloïdien.
  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