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   11003篇
  免费   508篇
  国内免费   52篇
耳鼻咽喉   264篇
儿科学   235篇
妇产科学   120篇
基础医学   1426篇
口腔科学   255篇
临床医学   699篇
内科学   3174篇
皮肤病学   178篇
神经病学   676篇
特种医学   354篇
外科学   1880篇
综合类   43篇
预防医学   367篇
眼科学   117篇
药学   633篇
中国医学   19篇
肿瘤学   1123篇
  2023年   84篇
  2022年   164篇
  2021年   279篇
  2020年   171篇
  2019年   183篇
  2018年   204篇
  2017年   182篇
  2016年   218篇
  2015年   196篇
  2014年   272篇
  2013年   340篇
  2012年   449篇
  2011年   527篇
  2010年   267篇
  2009年   238篇
  2008年   430篇
  2007年   477篇
  2006年   466篇
  2005年   521篇
  2004年   520篇
  2003年   472篇
  2002年   545篇
  2001年   396篇
  2000年   397篇
  1999年   337篇
  1998年   164篇
  1997年   107篇
  1996年   88篇
  1995年   109篇
  1994年   87篇
  1993年   74篇
  1992年   255篇
  1991年   231篇
  1990年   225篇
  1989年   228篇
  1988年   199篇
  1987年   184篇
  1986年   162篇
  1985年   183篇
  1984年   102篇
  1983年   93篇
  1982年   45篇
  1981年   40篇
  1979年   88篇
  1978年   43篇
  1977年   56篇
  1975年   55篇
  1972年   37篇
  1971年   46篇
  1968年   38篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We compared two different types of postinfectious encephalopathy using magnetic resonance imaging (MRI), including diffusion-weighted images and MR spectroscopy. Acute disseminated encephalomyelitis (ADEM) and acute necrotizing encephalopathy (ANE) showed different distribution of abnormal intensity areas and different diffusion of water measured by diffusion-weighted imaging (DWI). Proton MR spectroscopy (MRS) showed lactate production in both cases, which returned to a normal range; the rate of increased lactate production was much lower in the ANE case. Water diffusion showed a difference in pathophysiological background between the two encephalopathies, but the lactate elevation observed by proton MRS did not correlate with clinical severity.  相似文献   
102.
The aromatization of testosterone into oestrogens plays a key role in the control of many behavioural and physiological aspects of reproduction. In the quail preoptic area (POA), aromatase activity and the number of aromatase-immunoreactive (ARO-ir) cells are sexually differentiated (males > females). This sex difference is implicated in the control of the sexually dimorphic behavioural response of quail to testosterone. We analysed the ontogenetic development of this sex difference by measuring aromatase activity and counting ARO-ir cells in the POA of males and females from day 1 post hatch to sexual maturity. We investigated in parallel another enzyme: tyrosine hydroxylase, the rate limiting step in catecholamine synthesis. Between hatching and 4 weeks of age, aromatase activity levels were low and equal in males and females. Aromatase activity then markedly increased in both sexes when subjects initiated their sexual maturation but this increase was more pronounced in males so that a marked difference in aromatase activity was present in 6 and 8 week-old subjects. Tyrosine hydroxylase activity progressively increased with age starting immediately after hatching and there was no abrupt modification in the slope of this increase when birds became sexually mature. No sex difference was detected in the activity of this enzyme. The number of ARO-ir cells in the POA progressively increased with age starting at hatching. No sex difference in ARO-ir cell numbers could be detected before subjects reached full sexual maturity. The analysis of the three-dimensional organization of ARO-ir cells in the POA revealed that, with increasing ages, ARO-ir cells acquire a progressively more lateral position: they are largely periventricular in young birds but they are found at higher density in the lateral part of the medial preoptic nucleus in adults. These data indicate that aromatase activity differentiates sexually when birds reach sexual maturity presumably under the activating effects of the increased testosterone levels in males. The number of ARO-ir cells, however, begins to increase in a non sexually differentiated manner before the rise in plasma testosterone in parallel with the increased tyrosine hydroxylase activity. Whether this temporal coincidence results from a general ontogenetic pattern or from more direct causal links remains to be established.  相似文献   
103.
Lipid peroxidation and oxidative stress may play a certain role in the pathogenesis of pressure-induced atherosclerosis, and alcohol related diseases. Recently, 8-isoprostane in biological fluids has been reported to be a reliable marker for lipid peroxidation and oxidative stress in vivo. In the present study, we developed an ELISA method for 8-isoprostane which has high sensitivity, intra- and inter-assay reproducibility and wide dynamic assay range. Using this method, we examined the effects of drinking and smoking habits on plasma levels of 8-isoprostane in healthy subjects. A total of 157 apparently healthy volunteers was assayed for plasma 8-isoprostane. Subjects were divided into three groups according to their alcohol consumption. Group I is non- or few-drinkers, Group II includes subjects who drink once or twice a week, and subjects of Group III intake 3 to 5 times a week or almost every day. In addition, the same population was divided into two groups, 96 non-smokers and 61 smokers. Plasma 8-isoprostane was extracted with ODS gel followed by NH2 Sep-Pak column. The 8-isoprostane fractions thus separated were assayed by a commercial ELISA kit (Cayman Chemical). The plasma 8-isoprostane was estimated to be 20.9 +/- 93 pg/ml in a total of 157 volunteers (83 male, 74 female). The plasma 8-isoprostane levels were elevated in the Group III (26.6 +/- 9.5 pg/ml) compared with Group I (20.3 +/- 6.1 pg/mL, p<0.0001) and Group II (20.9 +/- 5.7 pg/ml, p<0.001). Significant increase of the plasma 8-isoprostane was observed only in habitual drinkers of females, but not in those of males. On the other hand, no significant difference of the plasma 8-isoprostane levels were observed between non-smokers (21.5 +/- 7.3 pg/ml) and smokers (22.8 +/- 7.4 pg/ml, p>0.05). We suppose that plasma 8-isoprostane may increase in the habitual drinkers due to the oxidization stress induced by alcohol intake, and it may become a useful marker to estimate drinking habit  相似文献   
104.
A 28-year-old Japanese woman had an invasive hydatidiform mole which was diagnosed by means of transvaginal ultrasonography. After the two initial courses of systemic methotrexate (MTX) therapy given over a period of weeks, the tumor was 14 mm in diameter and the surrounding blood supply remained rich. In addition to the two initial courses of systemic MTX therapy, local ultrasound-guided injection of MTX therapy was given three times, once per week. After the local MTX treatment, the betahCG level, which had been as high as 240 ng/mL, dropped to less than 0.1 ng/mL. We then gave two additional courses of systemic MTX therapy (once per week). More than 3 years have passed since the final systemic MTX therapy, and the patient's serum betahCG levels continue to be less than 0.1 ng/mL. An invasive mole can be treated with an ultrasound-guided local injection of MTX in addition to the established systemic MTX treatment.  相似文献   
105.
Orexin-A is a newly identified neuropeptide expressed in the lateral areas of the hypothalamus that plays a role in various physiological functions, including regulation of glucose metabolism. We have previously reported that the development of post-ischemic glucose intolerance is one of the triggers of ischemic neuronal damage. Therefore, the aim of this study was to determine the effects of orexin-A on the development of post-ischemic glucose intolerance and ischemic neuronal damage. Male ddY mice were subjected to middle cerebral artery occlusion (MCAO) for 2 h. Neuronal damage was estimated by histological and behavioral analysis after MCAO. Intracerebroventricular administration of orexin-A (2.5, 25, or 250 pmol/mouse) significantly and dose-dependently suppressed the development of post-ischemic glucose intolerance on day 1 after MCAO and neuronal damage on day 3 after MCAO. In the liver and skeletal muscle, the expression levels of insulin receptor were decreased, whereas those of gluconeogenic enzymes were increased on day 1 after MCAO. Furthermore, these expressions were completely recovered to normal levels by orexin-A and were reversed by the administration of SB334867, a specific orexin-1 receptor antagonist. These results suggest that regulation of post-ischemic glucose intolerance by orexin-A suppressed cerebral ischemic neuronal damage.  相似文献   
106.
A 39-year-old woman was hospitalized for nephrotic syndrome. Laboratory test results showed increased serum creatinine levels and urinary excretions of beta-2-microglobulin, and N-acetyl-beta-D-glucosaminidase. A renal biopsy revealed collapsing focal segmental glomerulosclerosis (FSGS) and acute interstitial nephritis. Despite treatment with pulse steroid followed by oral high-dose glucocorticoids and cyclosporines, heavy proteinuria persisted. After low-density lipoprotein apheresis (LDL-A) therapy was initiated, her proteinuria gradually decreased, leading to complete remission. A repeat renal biopsy after treatment revealed no collapsing glomeruli. Immediate LDL-A should be performed to treat cases of collapsing FSGS poorly responding to other treatments.  相似文献   
107.
The dosimetric effect of set-up error in boron neutron capture therapy (BNCT) for head and neck cancer remains unclear. In this study, we analyzed the tendency of dose error by treatment location when simulating the set-up error of patients. We also determined the tolerance level of the set-up error in BNCT for head and neck cancer. As a method, the distal direction was shifted with an interval of 2.5 mm, from 0.0 mm to +20.0 mm and compared with the dose at the reference position. Similarly, the horizontal direction and vertical direction were shifted, with an interval of 5.0 mm, from −20.0 mm to +20.0 mm. In addition, cases with 3.0 mm and 5.0 mm simultaneous shifts in all directions were analyzed as the worst-case scenario. The dose metrics of the minimum dose of the tumor and the maximum dose of the mucosa were evaluated. From unidirectional set-up error analysis, in most cases, the set-up errors with dose errors within ±5% were Δdistal < +2.5 mm, Δhorizontal < ±5.0 mm and Δvertical < ±5.0 mm. In the simulation of 3.0 mm shifts in all directions, the errors in the minimum tumor dose and maximum mucosal dose were −3.6% ±1.4% (range, −5.4% to −0.6%) and 2% ±1.4% (range, 0.4% to 4.5%), respectively. From these results, if the set-up error was within ±3.0 mm in each direction, the dose errors of the tumor and mucosa could be suppressed within approximately ±5%, which is suggested as a tolerance level.  相似文献   
108.
The irradiation field of boron neutron capture therapy (BNCT) consists of multiple dose components including thermal, epithermal and fast neutron, and gamma. The objective of this work was to establish a methodology of dosimetric quality assurance (QA), using the most standard and reliable measurement methods, and to determine tolerance level for each QA measurement for a commercially available accelerator-based BNCT system. In order to establish a system of dosimetric QA suitable for BNCT, the following steps were taken. First, standard measurement points based on tissue-administered doses in BNCT for brain tumors were defined, and clinical tolerances of dosimetric QA measurements were derived from the contribution to total tissue relative biological effectiveness factor-weighted dose for each dose component. Next, a QA program was proposed based on TG-142 and TG-198, and confirmed that it could be assessed whether constancy of each dose component was assured within the limits of tolerances or not by measurements of the proposed QA program. Finally, the validity of the BNCT QA program as an evaluation system was confirmed in a demonstration experiment for long-term measurement over 1 year. These results offer an easy, reliable QA method that is clinically applicable with dosimetric validity for the mixed irradiation field of accelerator-based BNCT.  相似文献   
109.
Although nasal septal abscess (NSA) was formerly common, it has become rare since the development of antibiotics. NSA, if left untreated, can lead to intracranial complications such as meningitis and eventually result in saddle-nose deformity. NSA often occurs after injury, and indigenous skin bacteria such as Staphylococcus aureus are frequently detected. We treated a patient who had injured the upper alveolus in a fall on the stairs and developed NSA two weeks later. Anaerobic bacteria, including Veillonella parvula and Peptostreptococcus sp., were detected. Symptoms were relieved by needle and incisional drainage. Our patient represents a very rare case of NSA in terms of the cause of onset and the detected bacteria. Early drainage can result in good outcomes.  相似文献   
110.
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