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   784篇
  免费   42篇
  国内免费   9篇
耳鼻咽喉   8篇
儿科学   21篇
妇产科学   6篇
基础医学   105篇
口腔科学   41篇
临床医学   112篇
内科学   125篇
皮肤病学   7篇
神经病学   72篇
特种医学   46篇
外科学   139篇
综合类   2篇
预防医学   39篇
眼科学   4篇
药学   53篇
肿瘤学   55篇
  2024年   1篇
  2023年   4篇
  2022年   10篇
  2021年   15篇
  2020年   10篇
  2019年   11篇
  2018年   12篇
  2017年   9篇
  2016年   12篇
  2015年   12篇
  2014年   23篇
  2013年   48篇
  2012年   37篇
  2011年   36篇
  2010年   33篇
  2009年   30篇
  2008年   51篇
  2007年   49篇
  2006年   33篇
  2005年   48篇
  2004年   45篇
  2003年   55篇
  2002年   47篇
  2001年   23篇
  2000年   16篇
  1999年   12篇
  1998年   17篇
  1997年   13篇
  1996年   6篇
  1995年   9篇
  1994年   8篇
  1993年   10篇
  1992年   11篇
  1991年   11篇
  1990年   6篇
  1989年   14篇
  1988年   3篇
  1987年   4篇
  1986年   8篇
  1985年   4篇
  1984年   10篇
  1983年   7篇
  1982年   3篇
  1981年   2篇
  1978年   3篇
  1976年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有835条查询结果,搜索用时 15 毫秒
21.
We describe here the size and location of nephrin, the first protein to be identified at the glomerular podocyte slit diaphragm. In Western blots, nephrin antibodies generated against the two terminal extracellular Ig domains of recombinant human nephrin recognized a 180-kDa protein in lysates of human glomeruli and a 150-kDa protein in transfected COS-7 cell lysates. In immunofluorescence, antibodies to this transmembrane protein revealed reactivity in the glomerular basement membrane region, whereas the podocyte cell bodies remained negative. In immunogold-stained thin sections, nephrin label was found at the slit between podocyte foot processes. The congenital nephrotic syndrome of the Finnish type (NPHS1), a disease in which the nephrin gene is mutated, is characterized by massive proteinuria already in utero and lack of slit diaphragm and foot processes. These features, together with the now demonstrated localization of nephrin to the slit diaphragm area, suggests an essential role for this protein in the normal glomerular filtration barrier. A zipper-like model for nephrin assembly in the slit diaphragm is discussed, based on the present and previous data.  相似文献   
22.
Formation of the palate, the organ that separates the oral cavity from the nasal cavity, is a developmental process characteristic to embryos of higher vertebrates. Failure in this process results in palatal cleft. During the final steps of palatogenesis, two palatal shelves outgrowing from the sides of the embryonic oronasal cavity elevate above the tongue, meet in the midline, and rapidly fuse together. Over the decades, multiple mechanisms have been proposed to explain how the superficial mucous membranes disappear from the contact line, thus allowing for normal midline mesenchymal confluence. A substantial body of experimental evidence exists for cell death, cell migration, epithelial-to-mesenchymal transdifferentiation (EMT), replacement through new tissue intercalation, and other mechanisms. However, the most recent use of gene recombination techniques in cell fate tracking disfavors the EMT concept, and suggests that apoptosis is the major fate of the midline cells during physiological palatal fusion. This article summarizes the benefits and drawbacks of histochemical and molecular tools used to determine the fates of cells within the palatal midline. Mechanisms of normal disintegration of the midline epithelial seam are reviewed together with pathologic processes that prevent this disintegration, thus causing cleft palate.  相似文献   
23.
BACKGROUND: Airway inflammation is a characteristic feature of bronchial asthma. Previous studies have shown an increased local inflammatory activity in the airway mucosa of asthma patients. OBJECTIVES: To analyze the association of asthma with three sensitive markers of systemic inflammation, C-reactive protein, serum amyloid-A (SAA), and plasma fibrinogen. METHODS: A cross-sectional, population-based study including 1,513 Finnish men aged 45 to 74 years, who participated in a chronic disease risk factor survey in 1997. Of the participating men, 97 were classified as asthma patients. The odds ratios of asthma were analyzed by quartile of each inflammation marker. RESULTS: In logistic regression models the age-adjusted odds ratios (second, third, and fourth quartile as compared with the first quartile) of asthma increased gradually with increasing quartile of C-reactive protein (1.28, 1.19, 1.96, P for trend = 0.039), SAA (1.20, 3.00, 3.49, P for trend < 0.001), and fibrinogen (1.22, 1.79, 3.16, P for trend < 0.001). The associations were independent of smoking. Further adjustment for waist-to-hip ratio, a marker of central obesity, and symptoms of chronic bronchitis weakened the observed association, but the increasing trend in the association of SAA and fibrinogen with asthma remained highly significant. CONCLUSIONS: Sensitive markers of systemic inflammation, particularly SAA and fibrinogen, were positively and significantly associated with asthma prevalence. These findings support the hypothesis that not only local, but also systemic, inflammation exist in bronchial asthma.  相似文献   
24.
Arterial pressure fluctuates rhythmically in healthy supine resting humans, who, from all outward appearances, are in a 'steady-state'. Others have asked, If baroreflex mechanisms are functioning normally, how can arterial pressure be so variable? We reanalysed data from nine healthy young adult men and women and tested the hypotheses that during brief periods of observation, human baroreflex sensitivity fluctuates widely and rhythmically. We estimated vagal baroreflex sensitivity with systolic pressure and R–R interval cross-spectra measured over 15 s segments, moved by 2 s steps through 20-min periods of frequency- and tidal volume-controlled breathing. We studied each subject at the same time on three separate days, with fixed protocols that included two physiological states, supine and passive 40 deg upright tilt, before and after β-adrenergic, cholinergic, and angiotensin converting enzyme blockade. Minimum, mean and maximum (± s.d. ) supine control baroreflex sensitivities averaged 5 ± 3, 18 ± 6, and 55 ± 22 ms mmHg−1. In most subjects, moderate ongoing fluctuations of baroreflex sensitivity were punctuated by brief major peaks, yielding frequency distributions that were skewed positively. Fast Fourier transforms indicated that baroreflex sensitivity fluctuations (expressed as percentages of total power) concentrated more in very low, 0.003–0.04 Hz, than ultra low, 0.0–0.003 Hz, frequencies (77 ± 7 versus 11 ± 8%, P ≤ 0.001, rank sum test). Autoregressive centre frequencies averaged 0.012 ± 0.003 Hz. The periodicity of very low frequency baroreflex sensitivity fluctuations was not influenced significantly by upright tilt, or by variations of autonomic drive or angiotensin activity. Our analysis indicates that during ostensibly 'steady-state' conditions, human vagal baroreflex sensitivity fluctuates in a major way, at very low frequencies.  相似文献   
25.
High intensity exercise decreases global brain glucose uptake in humans   总被引:3,自引:2,他引:3  
Physiological activation increases glucose uptake locally in the brain. However, it is not known how high intensity exercise affects regional and global brain glucose uptake. The effect of exercise intensity and exercise capacity on brain glucose uptake was directly measured using positron emission tomography (PET) and [18F]fluoro-deoxy-glucose ([18F]FDG). Fourteen healthy, right-handed men were studied after 35 min of bicycle exercise at exercise intensities corresponding to 30, 55 and 75% of     on three separate days. [18F]FDG was injected 10 min after the start of the exercise. Thereafter exercise was continued for another 25 min. PET scanning of the brain was conducted after completion of the exercise. Regional glucose metabolic rate (rGMR) decreased in all measured cortical regions as exercise intensity increased. The mean decrease between the highest and lowest exercise intensity was 32% globally in the brain (38.6 ± 4.6 versus 26.1 ± 5.0 μmol (100 g)−1 min−1, P < 0.001). Lactate availability during exercise tended to correlate negatively with the observed brain glucose uptake. In addition, the decrease in glucose uptake in the dorsal part of the anterior cingulate cortex (37% versus 20%, P < 0.05 between 30% and 75% of     ) was significantly more pronounced in subjects with higher exercise capacity. These results demonstrate that brain glucose uptake decreases with increase in exercise intensity. Therefore substrates other than glucose, most likely lactate, are utilized by the brain in order to compensate the increased energy needed to maintain neuronal activity during high intensity exercise. Moreover, it seems that exercise training could be related to adaptive metabolic changes locally in the frontal cortical regions.  相似文献   
26.
Recent genome-wide association studies identified 11 single nucleotide polymorphisms (SNPs) associated with breast cancer (BC) risk. We investigated these and 62 other SNPs for their prognostic relevance. Confirmed BC risk SNPs rs17468277 (CASP8), rs1982073 (TGFB1), rs2981582 (FGFR2), rs13281615 (8q24), rs3817198 (LSP1), rs889312 (MAP3K1), rs3803662 (TOX3), rs13387042 (2q35), rs4973768 (SLC4A7), rs6504950 (COX11) and rs10941679 (5p12) were genotyped for 25 853 BC patients with the available follow-up; 62 other SNPs, which have been suggested as BC risk SNPs by a GWAS or as candidate SNPs from individual studies, were genotyped for replication purposes in subsets of these patients. Cox proportional hazard models were used to test the association of these SNPs with overall survival (OS) and BC-specific survival (BCS). For the confirmed loci, we performed an accessory analysis of publicly available gene expression data and the prognosis in a different patient group. One of the 11 SNPs, rs3803662 (TOX3) and none of the 62 candidate/GWAS SNPs were associated with OS and/or BCS at P<0.01. The genotypic-specific survival for rs3803662 suggested a recessive mode of action [hazard ratio (HR) of rare homozygous carriers=1.21; 95% CI: 1.09-1.35, P=0.0002 and HR=1.29; 95% CI: 1.12-1.47, P=0.0003 for OS and BCS, respectively]. This association was seen similarly in all analyzed tumor subgroups defined by nodal status, tumor size, grade and estrogen receptor. Breast tumor expression of these genes was not associated with prognosis. With the exception of rs3803662 (TOX3), there was no evidence that any of the SNPs associated with BC susceptibility were associated with the BC survival. Survival may be influenced by a distinct set of germline variants from those influencing susceptibility.  相似文献   
27.
Preeclampsia is a common, pregnancy-specific vascular disorder characterised by hypertension and proteinuria. A recent report suggested association of the STOX1 gene on chromosome 10q22.1 with preeclampsia in the Dutch population. Here, we present a comprehensive assessment of STOX1 as a candidate gene for preeclampsia in the Finnish population by re-examining our previous genetic linkage analysis results for both chromosome 10 and paralogous loci, by genotyping representative markers in a nationwide data set, and by studying STOX1 expression in placentas from preeclamptic and uncomplicated pregnancies. In conclusion, we are unable to validate STOX1 as a common preeclampsia susceptibility gene.  相似文献   
28.
One group of fasting obese patients and one group of dieting obese patients were instructed to report their feelings of hunger and craving on a continuous basis before and during a three-week treatment period. Once a week they were also exposed to food slides to measure their reactivity to food stimuli. The frequency of hunger/craving responses and reactivity to food stimuli showed radically different changes over time in the fasting and dieting groups. During the last week of fasting, reactivity to food slides was completely abolished, and the frequency of hunger/craving responses was close to zero. Only slight changes of frequency of hunger/craving responses and reactivity to food stimuli were observed in the dieting group. The results suggest that the frequency of hunger/craving responses and reactivity to food stimuli show parallel decreases during fasting, but no changes during dieting.  相似文献   
29.
We studied the effects of the commonly used mu-opioid receptor agonists morphine, oxycodone, methadone and the enantiomers of methadone in thermal and mechanical models of acute pain and in the spinal nerve ligation model of neuropathic pain in rats. Subcutaneous administration of morphine, oxycodone, and methadone produced a dose-dependent antinociceptive effect in the tail flick, hotplate, and paw pressure tests. l-methadone, racemic methadone, and oxycodone had a similar dose-dependent antinociceptive effect, whereas the dose-response curve of morphine was shallower. In the spinal nerve ligation model of neuropathic pain, subcutaneous administration of morphine, oxycodone, methadone and l-methadone had antiallodynic effects in tests of mechanical and cold allodynia. l-methadone showed the strongest antiallodynic effect of the tested drugs. d-methadone was inactive in all tests. Morphine 5.0 mg/kg, oxycodone 2.5 mg/kg, and l-methadone 1.25 mg/kg decreased spontaneous locomotion 30 min after drug administration. In conclusion, in acute nociception all mu-opioid receptor agonists produced antinociception, with morphine showing the weakest effect. In nerve injury pain, l-methadone showed the greatest antiallodynic potency in both mechanical and cold allodynia compared with the other opioids. Opioids seem to have different profiles in different pain models. l-methadone should be studied for neuropathic pain in humans.  相似文献   
30.

Background

Recent studies have suggested that stent-grafting may improve the treatment outcome of patients with esophageal perforation, but evidence on this is still lacking.

Methods

Data on 194 patients who underwent conservative (43 patients), endoclip (4 patients) stent-grafting (63 patients) or surgical treatment (84 patients) for esophageal perforation were retrieved from nine medical centers.

Results

In-hospital/30-day mortality was 17.5 %. Three-year survival was 67.1 %. Age, coronary artery disease, and esophageal malignancy were independent predictors of early mortality. Chi squared automatic interaction detection analysis showed that patients without coronary artery disease, without esophageal malignancy and younger than 70 years had the lowest early mortality (4.1 %). Surgery was associated with slightly lower early mortality (conservative 23.3, endoclips 25.0 %, stent-grafting 19.0 %, surgery 13.1 %; p = 0.499). One center reported a series of more than 20 patients treated with stent-grafting which achieved an early mortality of 7.7 % (2/26 patients). Stent-grafting was associated with better survival with salvaged esophagus (conservative 76.7 %, endoclips 75.0 %, stent-grafting 77.8 %, surgery 56.0 %; p = 0.019). Propensity score adjusted analysis showed that stent-grafting achieved similar early mortality (p = 0.946), but significantly higher survival with salvaged esophagus than with surgical treatment (p = 0.001, OR 0.253, 95 % CI 0.110–0.585). Primary surgical repair was associated with somewhat lower early mortality (14.6 vs. 19.0 %; p = 0.561) and better survival with salvaged esophagus (85.4 vs. 77.8 %; p = 0.337) than stent-grafting.

Conclusions

Esophageal perforation was associated with a rather high mortality rate in this all-comers population. Stent-grafting failed to decrease operative mortality, but it improved survival with salvaged esophagus. The results of one of the centers indicate that increasing experience with this less invasive procedure may possibly improve the outcome of these patients.  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