全文获取类型
收费全文 | 1029篇 |
免费 | 44篇 |
国内免费 | 15篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 67篇 |
妇产科学 | 13篇 |
基础医学 | 131篇 |
口腔科学 | 14篇 |
临床医学 | 91篇 |
内科学 | 209篇 |
皮肤病学 | 9篇 |
神经病学 | 66篇 |
特种医学 | 155篇 |
外科学 | 49篇 |
综合类 | 60篇 |
预防医学 | 83篇 |
眼科学 | 3篇 |
药学 | 66篇 |
中国医学 | 1篇 |
肿瘤学 | 68篇 |
出版年
2021年 | 11篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 35篇 |
2012年 | 32篇 |
2011年 | 27篇 |
2010年 | 19篇 |
2009年 | 23篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 36篇 |
2005年 | 27篇 |
2004年 | 14篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 14篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 27篇 |
1997年 | 41篇 |
1996年 | 48篇 |
1995年 | 33篇 |
1994年 | 33篇 |
1993年 | 30篇 |
1992年 | 24篇 |
1991年 | 22篇 |
1990年 | 29篇 |
1989年 | 33篇 |
1988年 | 43篇 |
1987年 | 38篇 |
1986年 | 32篇 |
1985年 | 25篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1971年 | 5篇 |
1968年 | 5篇 |
1967年 | 5篇 |
1961年 | 5篇 |
排序方式: 共有1088条查询结果,搜索用时 0 毫秒
81.
Diagnosis of the thoracic outlet syndrome is often difficult, particularly in patients without osseous abnormalities on plain radiographs. The radiographic and computed tomographic (CT) findings were reviewed from 27 patients with thoracic outlet syndrome and 21 normal subjects. The plain radiographs and CT scans were assessed by two independent observers without awareness of the clinical history. Fifteen patients with thoracic outlet syndrome had osseous abnormalities (anomalous cervical ribs; abnormally long, drooping C-7 transverse processes) identifiable on plain radiographs. CT did not provide further diagnostic information in the patients with abnormal radiographs. Eight of 12 patients (66%) with normal plain radiographs had abnormal findings on CT scans, consisting of impingement of the C-7 transverse process on the scalene triangle or anteromedial aspect of the middle scalene muscle. Only two of 21 control patients (9.5%) displayed this CT abnormality (P less than .01). CT may be useful in patients with symptoms suggestive of thoracic outlet syndrome and no osseous abnormalities on plain radiographs. 相似文献
82.
Tongue and oropharynx: findings on MR imaging 总被引:6,自引:0,他引:6
Lufkin RB; Wortham DG; Dietrich RB; Hoover LA; Larsson SG; Kangarloo H; Hanafee WN 《Radiology》1986,161(1):69-75
Ten healthy subjects and 44 patients with diseases of the tongue or oropharynx were studied with magnetic resonance (MR) imaging. Axial, coronal, and sagittal images with a thickness of 4 mm were obtained with a pixel size of 0.75 X 0.75 mm on a 256 matrix. Nineteen of the patients underwent computed tomography (CT). Nine of those patients later had surgery, and the specimens were obtained for organ sectioning. These three studies as well as clinical history and physical examination findings were correlated. MR imaging was equal to or better than CT in those patients having both examinations. However, neither CT nor MR allowed recognition of histologic features or detection of microscopic spread of disease. Direct coronal and sagittal imaging planes on MR imaging allowed visualization of intrinsic tongue musculature, not possible with CT; this was important in recognizing subtle tumor extension. For these reasons, MR is the imaging method of choice for studying diseases of the tongue and oropharynx. 相似文献
83.
The maintenance of total ventilatory requirements through a chronic bronchopleural cutaneous fistula
D J Prezant T K Aldrich S C Fell S Heller S L Kamholz 《The American review of respiratory disease》1987,136(4):1001-1002
In patient with a chronic post-tuberculous bronchopleural cutaneous fistula (BPCF), minute ventilation, dead space, flow rates, arterial blood gas tensions, and oxygen consumption were measured during mouth breathing and after 30 min of steady-state breathing solely through the BPCF. Despite a 390-ml (18%) decrease in dead space when breathing took place through the BPCF, there were no significant changes in minute ventilation or respiratory rate. BPCF breathing was also associated with an increase in airways resistance as reflected by a 300-ml (35%) decrease in the FEV1 and a 16% decrease in the FEV1/FVC ratio. The increased resistance resulted in a 20 ml/min (18%) increase in oxygen consumption. Arterial blood gas tensions remained constant. We conclude that although ventilatory efficiency was not improved, this patient was able to satisfy his total minute ventilatory requirements, for the 30-min period, solely through BPCF breathing. 相似文献
84.
85.
A human monocyte-like cell line, U937, when grown in continuous culture, does not secrete lysosomal enzymes or migrate towards chemotactic factors. When the cells are stimulated by lymphokines, however, they develop the ability both to migrate directionally and to secrete enzymes in response to several types of chemoattractants. The development, by stimulated cells, of chemotactic and secretory responses to one class of chemoattractants, the N- formylated peptides, is accompanied by the appearance on the cells of specific binding sites for these substances. Using tritiated N-formyl- methionyl-leueyl-phenylalanine (fMet-Leu-[(3)H]Phe) as a ligand, it was determined that unstimulated U937 cells possess no detectable binding sites. However, after stimulation with lymphocyte culture supernates for 24, 48, and 72 h, they developed 4,505 (+/-) 1,138, 22,150(+/-) 4,030, and 37,200 (+/-) 8,000 sites/cell, respectively. The dissociation constants for the interaction of fMet-Leu-[SH]Phe with the binding sites were approximately the same regardless of stimulation time and ranged between 15 and 30 nM. The binding of fMet-Leu-[(3)H]Phe by stimulated U937 cells was rapid and readily reversed by the addition of a large excess of unlabeled peptide. The affinity of a series of N-formylated peptides for binding to U937 cells exactly reflected the potency of the peptides in inducing lysosomal enzyme secretion and chemotaxis. The availability of a continuous human monocytic cell line that can be induced to express receptors for N-formylated peptides will provide a useful tool not only for the characterization of such receptors but also for the delineation of regulatory mechanisms involved in cellular differentiation and the chemotactic response. 相似文献
86.
Plasma homocysteine, a risk factor for cardiovascular disease, is lowered by physiological doses of folic acid 总被引:9,自引:0,他引:9
Ward M; McNulty H; McPartlin J; Strain JJ; Weir DG; Scott JM 《QJM : monthly journal of the Association of Physicians》1997,90(8):519-524
Elevated plasma homocysteine, an independent risk factor for cardiovascular
disease (CVD) can be lowered by administration of pharmacological doses of
folic acid. The effect of lower doses in apparently normal subjects is
currently unknown but is highly relevant to the question of food
fortification. Healthy male volunteers (n = 30) participated in a chronic
intervention study (26 weeks). Folic acid supplements were administered
daily at doses increasing from 100 micrograms (6 weeks), to 200 micrograms
(6 weeks), to 400 micrograms (14 weeks). Fasting blood samples collected
before, during and 10 weeks post intervention were analysed for plasma
homocysteine, serum and red- cell folate levels. Results, expressed as
tertiles of baseline plasma homocysteine concentration, showed significant
(p < or = 0.001) homocysteine lowering in the top (10.90 +/- 0.83
mumol/l) and middle (9.11 +/- 0.49 mumol/l) tertiles only. In the low
tertile, where the mean baseline homocysteine level was 7.07 +/- 0.84
mumol/l, no significant response was observed. Of the three folic acid
doses, 200 micrograms appeared to be as effective as 400 micrograms, while
100 micrograms was clearly not optimal. There is thus a minimal level of
plasma homocysteine below which folic acid has no further lowering effect,
probably because an optimal folate status has been reached. A dose as low
as 200 micrograms/day of folic acid is effective in lowering plasma
homocysteine concentrations in apparently normal subjects. Any public
health programme for lowering homocysteine levels, with the goal of
diminishing CVD risk, should not be based on unnecessarily high doses of
folic acid.
相似文献
87.
T K Aldrich A B Fisher E Cadenas B Chance 《The Journal of laboratory and clinical medicine》1983,101(1):66-73
In order to evaluate the effect of paraquat on oxidative radical reactions in the lung, we studied MDA production and chemiluminescence (spontaneous and tBuOOH-induced) in the isolated rat lung. After 2 hr of perfusion with 3.0 mM paraquat, MDA content in lung homogenates was 16 +/- 7 nmol/gm dry weight higher than in control lungs (mean +/- S.E., n = 7, p less than 0.05 by paired test); during 30 min of perfusion, malondialdehyde efflux was 33 +/- 15 nmol/gm dry weight higher than in control perfusates (n = 6, p less than 0.05). Spontaneous chemiluminescence was not augmented by 2 hr of perfusion with concentrations of paraquat ranging from 0.75 to 6.0 mM. On the other hand, tBuOOH-induced chemiluminescence was 17% +/- 3 higher immediately after the addition of hydroperoxide and reached a 16% +/- 6 higher plateau for the paraquat-perfused lungs than for control lungs (n = 10, p less than 0.05). Spectral analysis of the light emitted during induced chemiluminescence demonstrated peak intensity between 630 and 730 nm for both control and paraquat-treated lungs. Increased MDA production and increased induced chemiluminescence indicate that perfusion with paraquat enhances lipid peroxidation in the isolated rat lung. 相似文献
88.
89.
World Trade Center "sarcoid-like" granulomatous pulmonary disease in New York City Fire Department rescue workers 总被引:1,自引:0,他引:1
Izbicki G Chavko R Banauch GI Weiden MD Berger KI Aldrich TK Hall C Kelly KJ Prezant DJ 《Chest》2007,131(5):1414-1423
BACKGROUND: Previous reports suggest that sarcoidosis occurs with abnormally high frequency in firefighters. We sought to determine whether exposure to World Trade Center (WTC) "dust" during the collapse and rescue/recovery effort increased the incidence of sarcoidosis or "sarcoid-like" granulomatous pulmonary disease (SLGPD). METHODS: During the 5 years after the WTC disaster, enrollees in the Fire Department of New York (FDNY) WTC monitoring and treatment programs who had chest radiograph findings suggestive of sarcoidosis underwent evaluation, including the following: chest CT imaging, pulmonary function, provocative challenge, and biopsy. Annual incidence rates were compared to the 15 years before the WTC disaster. RESULTS: After WTC dust exposure, pathologic evidence consistent with new-onset sarcoidosis was found in 26 patients: all 26 patients had intrathoracic adenopathy, and 6 patients (23%) had extrathoracic disease. Thirteen patients were identified during the first year after WTC dust exposure (incidence rate, 86/100,000), and 13 patients were identified during the next 4 years (average annual incidence rate, 22/100,000; as compared to 15/100,000 during the 15 years before the WTC disaster). Eighteen of 26 patients (69%) had findings consistent with asthma. Eight of 21 patients (38%) agreeing to challenge testing had airway hyperreactivity (AHR), findings not seen in FDNY sarcoidosis patients before the WTC disaster. CONCLUSION: After the WTC disaster, the incidence of sarcoidosis or SLGPD was increased among FDNY rescue workers. This new information about the early onset of WTC-SLGPD and its association with asthma/AHR has important public health consequences for disease prevention, early detection, and treatment following environmental/occupational exposures. 相似文献
90.
We report a patient with a clinical and molecular diagnosis of LEOPARD syndrome (LS) associated with multiple granular cell tumors (MGCT). Bidirectional sequencing of exons 7, 12, and 13 of the PTPN11 gene revealed the T468M missense mutation in exon 12. This mutation has been previously reported in patients with LS. To our knowledge, this is the first report of MGCT associated with molecularly characterized LS and provides the first molecular evidence linking granular cell tumors (GCT) to the Ras/mitogen-activated protein (MAP) kinase pathway. We propose that MGCT can be associated with LS. Analysis of GCT from this case tested negatively for loss of heterozygosity (LOH) at the PTPN11 and NF1 loci and did not show deletions of the PTEN gene. The absence of LOH of PTPN11 supports published functional data that T468M is a dominant-negative mutation. 相似文献