全文获取类型
收费全文 | 820篇 |
免费 | 63篇 |
国内免费 | 15篇 |
专业分类
耳鼻咽喉 | 5篇 |
儿科学 | 49篇 |
妇产科学 | 16篇 |
基础医学 | 112篇 |
口腔科学 | 31篇 |
临床医学 | 94篇 |
内科学 | 174篇 |
皮肤病学 | 95篇 |
神经病学 | 18篇 |
特种医学 | 130篇 |
外科学 | 56篇 |
综合类 | 37篇 |
预防医学 | 24篇 |
眼科学 | 5篇 |
药学 | 34篇 |
中国医学 | 2篇 |
肿瘤学 | 16篇 |
出版年
2021年 | 14篇 |
2020年 | 14篇 |
2019年 | 21篇 |
2018年 | 14篇 |
2017年 | 17篇 |
2016年 | 19篇 |
2015年 | 25篇 |
2014年 | 35篇 |
2013年 | 33篇 |
2012年 | 20篇 |
2011年 | 15篇 |
2010年 | 58篇 |
2009年 | 37篇 |
2008年 | 22篇 |
2007年 | 26篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 7篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 44篇 |
1997年 | 38篇 |
1996年 | 36篇 |
1995年 | 23篇 |
1994年 | 33篇 |
1993年 | 28篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1978年 | 4篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1972年 | 4篇 |
1968年 | 3篇 |
1966年 | 4篇 |
1956年 | 3篇 |
排序方式: 共有898条查询结果,搜索用时 406 毫秒
101.
Detection of the Philadelphia chromosome in acute lymphoblastic leukemia by pulsed-field gel electrophoresis 总被引:1,自引:0,他引:1
The Philadelphia (Ph1) chromosome is an acquired abnormality in the malignant cells of 10% to 25% of patients with acute lymphoblastic leukemia (ALL). Unlike chronic myelogenous leukemia (CML), where the molecular detection of the Ph1 chromosome is relatively straightforward using conventional Southern hybridization analysis, the detection of the Ph1 chromosome in ALL is complicated by the existence of several molecular subtypes, and the fact that translocation breakpoints are dispersed over a large genomic area. To circumvent these difficulties, we investigated pulsed-field gel electrophoresis (PFGE) to determine if this method could be used directly on clinical samples to detect the Ph1 chromosome in ALL. We report that, in a study of seven patients with Ph1-positive ALL, we could easily detect the Ph1 using only a single PFGE analysis, regardless of the Ph1 subtype, and we could confirm that the translocations occur either within or very near the BCR gene in all seven. We conclude that PFGE is a useful technique for the detection of the Ph1 in ALL, which ultimately may find wide applicability in the detection of other chromosomal abnormalities in other malignancies. 相似文献
102.
Cardiac abnormalities such as mitral valve prolapse (MVP) are reported to
be common features of the Ehlers Danlos syndrome (EDS), and it has been
suggested that the majority of patients with type IV EDS will have cardiac
involvement and vascular aneurysms. However, the evidence for valve lesions
is inconsistent and often based on early clinical studies using mainly
M-mode echo. We studied 33 patients (six male, 27 female; median age 35 yr)
with EDS (30 type I, II or III, three type IV) and 30 age- and sex-matched
controls. The study assessed skin stretch and joint hypermobility using
Beighton and Contompasis scores. Echocardiographic examination included
standard two-dimensional views from the parasternal and apical windows, and
measurement of the aorta at four sites (annulus, sinotubular junction, arch
and abdominal aorta). Echocardiographic abnormalities were found in four
patients (12.1%) (one atrial septal aneurysm, one tricuspid prolapse, two
MVP) and two controls (6.7%). MVP was found in 6.1% of EDS patients and 7%
of controls. Seven patients had previously been diagnosed as having MVP;
only two were shown to have true MVP using current criteria. None of those
with type IV EDS had any echocardiographic abnormality. No patients with
EDS had mean aortic dimensions outside the normal range at any of the
points tested. Cardiac symptoms were more frequent amongst the patients
than controls (atypical chest pain 48%, P = 0.0001; palpitation 39%, P =
0.001; exertional dyspnoea 30%). A wide range of rheumatological complaints
were reported (current arthralgia 75%; recent back pain 72%, P = 0.005;
recurrent dislocation 72%). Contrary to earlier published observations, we
have not found an increased incidence of cardiac abnormalities in EDS. This
syndrome may be relatively more benign, from the cardiac point of view,
than was previously thought.
相似文献
103.
To determine the prevalence and significance of a systolic mitralmurmur heard after a first acute myocardial infarction (MI),we studied 186 consecutive patients in the coronary care unit(CCU) during a one-year period. Fifteen patients had a murmuras a result of mitral regurgitation (MR) (prevalence 8%) documentedby colour Doppler flow imaging. It was heard before the thirdday of hospitalization in 10 (67%) patients, and on the thirdday itself in the remainder. The severity of MR was graded semi-quantitatively:moderate in 12 (80%) patients, and mild, moderate to severeand severe in three respectivety. The direction of the MR jet,determined by colour flow imaging, improved the informationobtained by two-dimensional echocardiography (2D echo) thatcould only diagnose mitral leaflet abnormality in seven (47%)patients. in 10 of 15 (67%) patients, the 2D echo ejection fractionwas 40% and in eight (53%) the wall motion score obtained byanalysing 11 left ventricular (LV) segments was $$$8. Two (13%)patients died in tile CCU, four (27%) had LV failure, one anginaand eight (53%) remained asymptomaric in the hospital. Of 171patients without a systolic murmur, 22 (13%) had LV failure,13 (8%) angina and 25 (15%) died during the in-hospital stay(P-NS for these complications between patients with and withoutMR murmur). During a follow-up of 1224 months, one MRpatient died, and seven (47%) remained asymptomatic. We conclude that the prevalence of MR systolic murmurs in acuteMI patients is low. The LV function and the prognosis of a majorityof these patients is rather good. 相似文献
104.
Interleukin-3, GM-CSF, and TPA induce distinct phosphorylation events in an interleukin 3-dependent multipotential cell line 总被引:9,自引:0,他引:9
The mechanism of action of the hemopoietic growth factor, murine interleukin-3 (mIL-3), was investigated using an mIL-3-dependent multipotential hematopoietic cell line, B6SUtA1. Murine granulocyte- macrophage colony-stimulating factor (mGM-CSF) was as potent as mIL-3 in stimulating these cells. In addition, sodium orthovanadate, an inhibitor of phosphotyrosine phosphatase, and 12-O-tetradecanoyl- phorbol-13-acetate (TPA), a known activator of protein kinase C, also stimulated DNA synthesis in these cells, suggesting that protein phosphorylation might be involved in the mechanism of action of mIL-3 and mGM-CSF. To assess this possibility, intact B6SUtA1 cells exposed for brief periods to mIL-3, mGM-CSF, and TPA were analyzed for changes in phosphorylation patterns using metabolic 32P-labeling and antibodies to phosphotyrosine. Both mIL-3 and mGM-CSF induced the serine-specific phosphorylation of a 68-Kd cytosolic protein, whereas all three agents stimulated the serine-specific phosphorylation of a 68-Kd membrane protein. Furthermore, mIL-3 stimulated tyrosine phosphorylation of the 68-Kd membrane protein, as well as of 140-, 90-, 55, and 40-Kd proteins. The 90-Kd protein was also tyrosine phosphorylated in response to mGM-CSF. These phosphotyrosine containing proteins were not detected in TPA-treated cells. These results indicate that protein phosphorylations on tyrosine and serine residues occur in B6SUtA1 cells following short-term incubation with mIL-3 or mGM-CSF and that most of these phosphorylation events are mediated by kinases other than protein kinase C (PkC). 相似文献
105.
The value of cross-sectional echocardiography in the diagnosisof tricuspid valve stenosis is not clearly established. We prospectivelystudied by cardiac catheterization 42 consecutive patients,with a mean age of 29 ± 11 years, who exhibited the cross-sectionalechocardiographic features of tricuspid valve stenosis, definedas: diastolic doming of all three tricuspid leaflets and leafletthickening with restrictive motion. To expose occult and amplifyborderline tricuspid diastolic gradients, simultaneous rightatrial and right ventricular pressures were recorded in thebasal state, after incremental infusions of normal saline to200,400,500, 700 or 1000 ml until a mean right atrial pressureof 12 mmHg was achieved, and finally after intravenous administrationof 0.6 mg of atropine. Eighteen patients, Group 1, (43%) exhibitedmean tricuspid diastolic gradients >2mmHg after saline infusion,increasing from a mean of4 ± 2 to 9 ± 3 mmHg,(P <0.001), 14 (33%) having gradients <2mmHg in the basalstate, together with four (10%) increasing from 1.7 ±0.2 to 4.5 ± l.2 mmHg (P <0.01) after provocationwith fluid challenge. In the remaining 24 patients, Group 2,(57%) the mean tricuspid diastolic gradient was <2 mmHg,both at rest and after provocative manoeuvres. We conclude thatthe cross-sectional echocardiographic features of tricuspidvalve stenosis are not a precise indicator of tricuspid valvestenosis. Provocative manoeuvres during haemodynamic studiesare required to expose occult or amplify borderline tricuspiddiastolic gradients in a minority of patients with the cross-sectionalechocardiographic features of tricuspid stenosis. 相似文献
106.
Interaction of high molecular weight kininogen, factor XII, and fibrinogen in plasma at interfaces 总被引:5,自引:0,他引:5
Using ellipsometry, anodized tantalum interference color, and Coomassie blue staining in conjunction with immunologic identification of proteins adsorbed at interfaces, we have previously found that fibrinogen is the main constituent deposited by plasma onto many man- made surfaces. However, the fibrinogen deposited from normal plasma onto glass and similar wettable materials is rapidly modified during contact activation until it can no longer be identified antigenically. In earlier publications, we have called this modification of the fibrinogen layer "conversion," to indicate a process of unknown nature. Conversion of adsorbed fibrinogen by the plasma was not accompanied by marked change in film thickness, so that we presumed that this fibrinogen was not covered but replaced by other protein. Conversion is now showen to be markedly delayed in plasma lacking high molecular weight kininogen, slightly delayed in plasma lacking factor XII, and normal in plasma that lack factor XI or prekallikrein. We conclude that intact plasma will quickly replace the fibrinogen it has deposited on glass-like surfaces by high molecular weight kininogen and, to a smaller extent, by factor XII. Platelets adhere preferentially to fibrinogen-coated surfaces; human platelets adhere to hydrophobic nonactivating surfaces, since on these, adsorbed firbinogen is not exchanged by the plasma. The adsorbed fibrinogen will be replaced on glass-like surfaces during surface activation of clotting, and platelets failing to find fibrinogen will not adhere. 相似文献
107.
A comparative analysis of enzymatic activities has been performed on 47 human continuous lymphoid lines: 22 tumors derived from Burkitt's lymphoma lines, 6 other lymphomatous long-term cultures, and 19 nonmalignant ties determined on the cell extracts. 4 showed no significant differences between the various lines. They included adenosine diphosphoribose incorporation, glucose-6-phosphate dehydrogenase, cyclic-AMP phosphodiesterase, and glutathione reductase. However, striking differences of activity were found for the enzyme, NAD(P) glycohydrolase (EC 3.2.2.6). Activity levels were, as a mean, four times higher in Burkitt's lymphoma-derived cell lines than in nonmalignant control lines, and the difference was highly significant (p less than 0.02). All Burkitt cell lines containing translocations of chromosome 8 with either chromosomes 2, 14 or 22 showed an increased activity. The specificity and significance of this possible enzymatic marker of Burkitt's lymphoma cells is discussed. 相似文献
108.
In this investigation, we studied the importance of cellular glutathione (GSH) in the hexose monophosphate shunt (HMPS) activity of unstimulated human erythrocytes and the mechanism by which pyruvate stimulates the HMPS. The rate of HMPS activity was measured by the production of radioactive CO2 from 14C-1-glucose or 14C-1-ribose using a vibrating reed electrometer and ionization chamber. HMPS activity was not significantly impaired by N-ethylmaleimide (NEM) in concentrations which bound all red cell GSH. Red cells incubated under carbon monoxide (CO), an experimental condition which eliminates peroxide production, still had HMPS activity which was 44% of the value under air. Pyruvate stimulation of the HMPS was unaffected by doses of NEM which bound all cellular GSH or by incubation under CO. These data indicated that pyruvate stimulation of the HMPS occurs by pathways which do not involve peroxide formation, GSH, or oxygen. This study indicates that sulfhydryl blockade of GSH does not necessarily inhibit HMPS activity and that HMPS activity in red cells may respond to reactions not linked directly to glutathione reduction. 相似文献
109.
Interstitial lung fibrosis and rheumatic disorders in patients with hepatitis C virus infection 总被引:4,自引:1,他引:4
Ferri C; La Civita L; Fazzi P; Solfanelli S; Lombardini F; Begliomini E; Monti M; Longombardo G; Pasero G; Zignego AL 《Rheumatology (Oxford, England)》1997,36(3):360-365
A possible aetiopathogenetic role of hepatitis C virus (HCV) has been
reported in various immune-mediated disorders, such as mixed
cryoglobulinaemia, which may be complicated by interstitial lung
involvement; moreover, different viruses, including HCV, have been
correlated with idiopathic pulmonary fibrosis. Here, a cohort of eight
HCV-positive patients (M/F = 4/4, mean age 61 +/- 8 S.D. yr) with
interstitial lung fibrosis and a variable number of rheumatic disorders are
described. Interstitial lung involvement appeared medially 4.5 +/- 3.2 S.D.
yr after the clinical onset of chronic hepatitis. During the clinical
follow-up, some rheumatic symptoms were also recorded: articular
involvement (four patients): mild sicca syndrome (one patient); severe
polymyositis and cranial neuropathy (one patient); serum cryoglobulins
and/or autoantibodies (eight patients). In all patients, a moderate (four
patients) or severe (four patients) lung fibrosis was evaluated by means of
high-resolution computed tomography. The presence of parenchymal
radiotracer uptake on 67Ga scan (7/7 patients) and increased percentages of
neutrophils (4/4 patients) and lymphocytes (2/4) at bronchoalveolar lavage
suggested an active lung involvement. Different degrees of reduction of
single breath diffusing capacity for carbon monoxide (DLco) (mean value
57.6 +/- 15%, range 37- 80) were observed in all cases, while spirometric
abnormalities, consistent with a global restrictive pattern, were less
frequently found. In all cases, anti-HCV antibodies and HCV viraemia were
demonstrated: viral genome was also detected in peripheral lymphocytes from
4/4 subjects and in one case in lung biopsy specimens. A desquamative
interstitial pneumonia pattern was demonstrated in two cases by lung
biopsy. The present work supports the hypothesis that HCV chronic infection
could represent a trigger factor for interstitial lung fibrosis and various
rheumatic disorders.
相似文献
110.
O Falusi AL French EC Seaberg PC Tien DH Watts H Minkoff E Piessens A Kovacs K Anastos MH Cohen 《Clinical infectious diseases》2002,35(11):1414-1417
We assessed the prevalence and predictors of latent Toxoplasma infection in a large group of human immunodeficiency virus (HIV)-infected and HIV-uninfected at-risk US women. The prevalence of latent Toxoplasma infection was 15% (380 of 2525 persons) and did not differ by HIV infection status. HIV-infected women aged > or =50 years and those born outside of the United States were more likely to have latent Toxoplasma infection, with prevalences of 32% and 41%, respectively. 相似文献