全文获取类型
收费全文 | 51671篇 |
免费 | 3157篇 |
国内免费 | 246篇 |
专业分类
耳鼻咽喉 | 645篇 |
儿科学 | 1188篇 |
妇产科学 | 1234篇 |
基础医学 | 7157篇 |
口腔科学 | 1515篇 |
临床医学 | 5650篇 |
内科学 | 11099篇 |
皮肤病学 | 804篇 |
神经病学 | 5150篇 |
特种医学 | 1790篇 |
外科学 | 6429篇 |
综合类 | 327篇 |
一般理论 | 47篇 |
预防医学 | 3661篇 |
眼科学 | 809篇 |
药学 | 3495篇 |
1篇 | |
中国医学 | 59篇 |
肿瘤学 | 4014篇 |
出版年
2023年 | 323篇 |
2022年 | 634篇 |
2021年 | 1146篇 |
2020年 | 749篇 |
2019年 | 988篇 |
2018年 | 1205篇 |
2017年 | 1080篇 |
2016年 | 1266篇 |
2015年 | 1321篇 |
2014年 | 1753篇 |
2013年 | 2528篇 |
2012年 | 3826篇 |
2011年 | 4009篇 |
2010年 | 2380篇 |
2009年 | 2171篇 |
2008年 | 3331篇 |
2007年 | 3621篇 |
2006年 | 3238篇 |
2005年 | 3300篇 |
2004年 | 3027篇 |
2003年 | 2828篇 |
2002年 | 2590篇 |
2001年 | 454篇 |
2000年 | 376篇 |
1999年 | 520篇 |
1998年 | 574篇 |
1997年 | 477篇 |
1996年 | 419篇 |
1995年 | 365篇 |
1994年 | 319篇 |
1993年 | 318篇 |
1992年 | 266篇 |
1991年 | 255篇 |
1990年 | 232篇 |
1989年 | 251篇 |
1988年 | 228篇 |
1987年 | 189篇 |
1986年 | 193篇 |
1985年 | 234篇 |
1984年 | 201篇 |
1983年 | 176篇 |
1982年 | 212篇 |
1981年 | 165篇 |
1980年 | 146篇 |
1979年 | 129篇 |
1978年 | 134篇 |
1977年 | 140篇 |
1976年 | 100篇 |
1975年 | 116篇 |
1974年 | 90篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Heart puncture-induced hemopericardium is a serious complication of the pericardiocentesis. Two-dimensional echocardiographic examination performed in two patients just before and after the development of hemopericardium revealed a unique image in which pericardial bleeding manifested itself by an echodensity thrombus appearance adjacent to the cardiac chambers. With appropriate differentiation to some other intrapericardial echodensity masses, such distinctive images can be highly specific for active bleeding into the pericardial sac. 相似文献
993.
Is CEA analysis of value in screening for recurrences after surgery for colorectal carcinoma? 总被引:2,自引:3,他引:2
Ulf Carlsson M.D. Jan Stewénius M.D. Dr. Göran Ekelund M.D. Lennart Leandoer M.D. Bertil Nosslin M.D. 《Diseases of the colon and rectum》1983,26(6):369-373
The progress of 139 patients operated upon for cure of colorectal carcinoma, was followed postoperatively with a standardized
protocol. A CEA test was performed for comparison with other parameters. Median observation time was four years. When an upper
limit for CEA of 7.5 μg/l was allowed, sensitivity was found to be 78 per cent, specificity 91 per cent, and predictive value
of an elevated CEA concentration, 83 per cent. In general, CEA measurement traced, recurrence six months before clinical diagnosis.
In only a few cases was recurrence first heralded by an abnormality in other blood chemistry test results. CEA may thus be
used in postoperative screening for recurrence even though most recurrences, when detected, are not curable.
Read at the meeting of the American Society of Colon and Rectal Surgeons, Boston, Massachusetts, June 5–9, 1983
Presented in part at The World Congresses of Gastroenterology (OMGE) and Coloproctology, Stockholm, Sweden, June 14–19, 1982. 相似文献
994.
Reviews in Endocrine and Metabolic Disorders - 相似文献
995.
Mörner A Björndal A Leandersson AC Albert J Björling E Jansson M 《AIDS research and human retroviruses》2002,18(3):193-200
Primary human immunodeficiency virus type 2 (HIV-2) isolates are characterized by their ability to use a broad range of coreceptors, including CCR5, CXCR4, and several alternative coreceptors. However, the in vivo relevance of this in vitro promiscuity in coreceptor usage remains unclear. We set out to evaluate the relative importance of CCR5 and CXCR4 for infection of activated peripheral blood mononuclear cells (PBMC). PBMC from donors homozygous for wild-type CCR5 (CCR5(+/+) or CCR5Delta32 (CCR5(-/-)) were tested for their susceptibility to infection with 10 primary HIV-2 isolates with known coreceptor usage by parallel 50% tissue culture infectious dose (TCID50) titrations. Although all isolates, except one, were able to establish productive infection in CCR5(-/-) PBMC, the infection of these cells was inefficient for all isolates that were unable to use CXCR4. For CXCR4-using isolates there were only minor differences in TCID50 between CCR5(+/+) and CCR5(-/-) PBMC. When we compared the replication kinetics in PBMC from donors of the two genotypes we observed an average delay in replication onset of 9 days in the CCR5(-/-) PBMC. This study shows that HIV-2 can use alternative coreceptors for infection of PBMC, but that this infection is much less efficient than infection mediated by CCR5 or CXCR4. Thus, CCR5 and CXCR4 appear to be the major coreceptors for HIV-2 infection of PBMC. 相似文献
996.
Hoffmann R Radke PW Ortlepp JR Haager PK Blindt R Iofina E Franke A Langenberg R Weber C Hanrath P 《The American journal of cardiology》2004,94(12):1548-1550
Intravascular ultrasound studies were performed at angiographic follow-up on 121 native coronary lesions treated with 1 bare metal stent (n = 50), high-dose dexamethasone-eluting stents (n = 18), non-polymer-based paclitaxel-eluting stents (n = 18), or sirolimus-eluting stents (n = 35). Paclitaxel- and sirolimus-eluting stents reduced mean intimal hyperplasia thickness compared with bare metal stents by 49% and 90% (p = 0.048 and p <0.001), respectively, whereas mean intimal hyperplasia thickness treated with dexamethasone-eluting stents was similar to those lesions treated with bare metal stents. 相似文献
997.
Eriksson P Andersson C Ekerfelt C Ernerudh J Skogh T 《The Journal of rheumatology》2004,31(4):729-735
OBJECTIVE: To measure in vitro cytokine release from peripheral blood mononuclear cells (PBMC) and serum cytokines in patients with primary Sj?gren's syndrome (SS) with and without myalgia, compared to patients with rheumatoid arthritis (RA) and healthy controls. METHODS: Sixteen women with SS (8 with myalgia, 8 without pain), 15 women with RA, and 14 healthy women were studied. PBMC were isolated and cultured. Secretion of interleukin 1 beta (IL-1 beta), IL-6, IL-10, and tumor necrosis factor-alpha (TNF-alpha) was measured in cell supernatants with or without stimulation with phytohemagglutinin, tetanus toxoid, or purified protein derivative (PPD). Enzyme-linked immunospot was used to enumerate interferon-gamma (IFN-gamma) and IL-4-secreting cells. Serum concentrations of IL-8 and IL-18 were analyzed by ELISA. RESULTS: PPD-stimulated PBMC from SS patients responded with less production of IL-10, TNF-alpha, and IFN-gamma compared to controls. Patients with SS and pain were hyporesponsive also with respect to IL-1 beta and IL-6. The generally subnormal cytokine release was statistically significant in myalgic patients with SS compared to healthy controls. Serum IL-18 was increased in both SS groups as well as in patients with RA, and the highest levels were found in myalgic patients with SS. Serum IL-8 was increased in RA but not in SS. CONCLUSION: Patients with SS, especially those with myalgia, had diminished PBMC cytokine release and increased serum IL-18. This finding suggests that impaired cytokine regulation may have pathogenetic importance for myalgia in SS. 相似文献
998.
Although in many cardiac surgery centers pharmacological strategies based on fibrinolytic inhibitors are used on a routine basis, detailed knowledge of fibrinolysis during various settings of coronary surgery is still limited. Sixty-five patients scheduled for coronary surgery were randomized into 3 groups: group A--conventional coronary artery bypass grafting, group B--off-pump surgery, and group C--coronary artery bypass grafting with modified, rheoparin coated cardiopulmonary bypass with the avoidance of reinfusion of cardiotomy blood into the circuit. The sampling time points for rotation thromboelastographic evaluations were as follows: preoperatively, 15 minutes after sternotomy, on the completion of peripheral bypass anastomoses, at the end of the procedures, and 24 hours after the end of surgery. D-dimer levels were evaluated before surgery, at the end of procedures, and 24 hours after surgery. Thromboelastographic signs of fibrinolysis (evaluated by Lysis Onset Time-intergroup differences at 60 and 150 minutes of assessment: P = 0.003 and P < 0.001, respectively) were clearly detectable during cardiopulmonary bypass in group A, but not at any time in groups B and C. At the other sampling times all thromboelastographic parameters were similar in all groups. In group A, no exceptional bleeding tendency (during 24 hours), as compared to groups B and C (geometric means and 95% confidence intervals: group A: 686.7 [570.8; 826.1] mL, group B: 555.3 [441.3; 698.9] mL, group C: 775.6 [645.1; 932.3] mL, P = 0.157), and no significant correlations between Lysis Onset Time, postoperative blood loss, and D-dimer levels were found. No significant differences in postoperative blood loss related to cardiac surgeons and assistant surgeons were detected. Thromboelastographic signs of increased fibrinolysis were detectable in the important proportion of coronary surgery patients operated on with the use of conventional cardio-pulmonary bypass, but not in off-pump patients and those operated on with the biocompatible surface-modified circuit without reinfusion of cardiotomy suction blood. These signs resolved spontaneously at the end of surgery and were not associated with increased postoperative bleeding. No significant correlation with D-dimer levels was found. 相似文献
999.
Epithelial proliferation,cell death,and gene expression in experimental colitis: alterations in carbonic anhydrase I,mucin MUC2, and trefoil factor 3 expression 总被引:12,自引:0,他引:12
Renes IB Verburg M Van Nispen DJ Taminiau JA Büller HA Dekker J Einerhand AW 《International journal of colorectal disease》2002,17(5):317-326
BACKGROUND AND AIMS: To gain insight in intestinal epithelial proliferation, cell death, and gene expression during experimental colitis rats were treated with dextran sulfate sodium (DSS) for 7 days. MATERIALS AND METHODS: Proximal and distal colonic segments were excised on days 2, 5, 7, and 28. Epithelial proliferation, cell death, enterocyte gene expression (carbonic anhydrase I (CA I) and goblet cell gene expression (mucin, MUC2; trefoil factor 3, TFF3) were studied immunohistochemically and biochemically. RESULTS: Proliferative activity was decreased in the proximal and distal colon at the onset of disease (day 2). However, during active disease (days 5-7) epithelial proliferation was increased in the entire proximal colon and in the proximity of ulcerations in the distal colon. During DSS treatment the number of apoptotic cells in the epithelium of both colonic segments was increased. In the entire colon surface enterocytes became flattened and CA I negative during active disease (day 5-7). Additionally, CA I levels in the distal colon significantly decreased during this phase. In contrast, during the regenerative phase (day 28) CA I levels were restored in the distal colon and up-regulated in the proximal colon. During all disease phases increased numbers of goblet cells were observed in the surface epithelium of the entire colon. In the distal colon TFF3 expression extended to the bottom of the crypts during active disease. Finally, MUC2 and TFF3 expression was increased in the proximal colon during disease. CONCLUSION: DSS affected the epithelium by inhibiting proliferation and inducing apoptosis. DSS-induced inhibition of CA I expression indicates down-regulation of specific enterocyte functions. Accumulation of goblet cells in the surface epithelium and up-regulation of MUC2 and TFF3 expression in the proximal colon underline the importance of goblet cells in epithelial protection and repair, respectively. 相似文献
1000.
Cavelaars M Tulen JH van Bemmel JH van den Meiracker AH 《Journal of hypertension》2004,22(12):2303-2309
OBJECTIVE: To determine the effect of physical activity on diurnal blood pressure (BP) and haemodynamic variation. METHODS: Ambulatory measurements were performed during 24 h in 36 subjects (18 hypertensive, 13 male), aged 49.7 +/- 13.5 years. BP was recorded in the brachial artery. Physical activity and posture were measured with five acceleration sensors. RESULTS: Of the subjects 50% were dippers (nocturnal decrease in systolic or diastolic BP >/= 10%). Dippers and non-dippers had similar daytime BP, daytime, night-time, and day-night difference in physical activity, subjective sleep quality, and nocturnal cardiac output decrease (14.9 +/- 9.6 and 16.0 +/- 5.9%). In non-dippers vascular resistance increased from day to night by 9.7 +/- 8.3%, while it remained unchanged (-1.0 +/- 13.9%) in dippers. Day-night changes in heart rate and cardiac output were correlated with day-night changes in physical activity (r = 0.39 and 0.43), whereas day-night changes in systolic BP were correlated with night-time activity (r = -0.34). By selection of the active (i.e. walking) and inactive (i.e. not walking) periods during the day, we showed that physical activity has a large potential effect on dipping status and diurnal haemodynamic variation underlying BP variation. Depending on the BP taken (systolic or diastolic, respectively) the proportion of dippers increased to 81% or decreased to 25% if only the walking period was considered, whereas it decreased to 36% or increased to 53% if only the non-walking period was considered. CONCLUSIONS: Non-dippers differ from dippers by an increase of vascular resistance during the night. The degree of physical activity normally encountered during ambulatory monitoring has little influence on the diurnal BP profile or dipping status, but significantly influences underlying haemodynamics. Related to the different effects of posture and activity on systolic and diastolic BP, dipping classification may vary with the BP index taken. 相似文献