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   8183篇
  免费   433篇
  国内免费   45篇
耳鼻咽喉   28篇
儿科学   124篇
妇产科学   106篇
基础医学   1268篇
口腔科学   311篇
临床医学   882篇
内科学   1656篇
皮肤病学   309篇
神经病学   1016篇
特种医学   520篇
外科学   923篇
综合类   52篇
一般理论   4篇
预防医学   347篇
眼科学   120篇
药学   465篇
中国医学   16篇
肿瘤学   514篇
  2023年   39篇
  2022年   56篇
  2021年   124篇
  2020年   83篇
  2019年   103篇
  2018年   139篇
  2017年   120篇
  2016年   105篇
  2015年   175篇
  2014年   236篇
  2013年   354篇
  2012年   504篇
  2011年   545篇
  2010年   338篇
  2009年   323篇
  2008年   536篇
  2007年   538篇
  2006年   567篇
  2005年   585篇
  2004年   509篇
  2003年   516篇
  2002年   495篇
  2001年   114篇
  2000年   76篇
  1999年   100篇
  1998年   128篇
  1997年   103篇
  1996年   91篇
  1995年   75篇
  1994年   58篇
  1993年   58篇
  1992年   42篇
  1991年   40篇
  1990年   25篇
  1989年   24篇
  1988年   28篇
  1987年   22篇
  1986年   21篇
  1985年   32篇
  1984年   19篇
  1983年   18篇
  1982年   43篇
  1981年   30篇
  1980年   21篇
  1978年   27篇
  1977年   20篇
  1973年   18篇
  1970年   20篇
  1913年   25篇
  1912年   19篇
排序方式: 共有8661条查询结果,搜索用时 31 毫秒
981.
Treatment of in-stent restenosis remains a therapeutic challenge. Twenty-seven lesions with in-stent restenosis were treated with non-polymer-based paclitaxel-eluting stents. At 6-month follow-up, in-stent late loss was 0.44 +/- 0.54 mm and the restenosis rate was 20%, indicating effective treatment for reduction of recurrent restenosis.  相似文献   
982.
AIMS: The increasing number of adults with congenital heart disease (CHD) has prompted the development of recommendations for the management of these patients and for the organization of their healthcare. The aim of this report is to describe the delivery of care in Europe for adults with congenital cardiac anomalies. METHODS AND RESULTS: As part of the Euro Heart Survey on Adult Congenital Heart Disease, we obtained data from 71 voluntarily participating centres that detailed their care practices for these patients. Forty-eight of these centres were specialist centres and 23 were non-specialist centres. We found that only 19% of the specialist centres complied with defined standards for optimal care structure. The criteria that appeared to be most difficult for all centres to achieve were performing 50 congenital heart operations or more per year and involving nurse specialists in the care of these patients. CONCLUSION: This survey indicated that the provision of care in Europe for adults with congenital heart defects is suboptimal. To fully realize the benefits of cardiac surgery performed in infants and children, continuous effort must be applied by healthcare professionals in order to implement the recommendations on the organization of care for these patients.  相似文献   
983.
There are contradictory reports whether exercise capacity is reduced in patients on long-term follow-up after coarctation repair. Data from unselected patient groups are missing. In a cross-sectional, long-term follow-up study of a tertiary congenital cardiology referral center, 260 patients (30.2+/-11.4 years old, 84 women), after surgical repair for isolated aortic coarctation (age at surgery 11.5+/-11.2 years), underwent a symptom-limited exercise test. Peak workload was 180+/-52 W, significantly less than the age- and height-related reference values (p<0.0005). A peak workload under 80% of expected was found in 200 patients (77%). Exercise performance of the patients was independent from age at surgery, type of surgery, or the systolic brachial-ankle blood pressure difference. The only exercise-limiting factor found was the chronic administration of diuretics to treat hypertension (p=0.005). Exercise hypertension, defined as a systolic blood pressure >2 SD above the load-dependent reference value, was found in 73 patients (28%). It was independently related to the systolic brachial-ankle blood pressure difference (p<0.0005) and diuretics administration (p=0.037). In conclusion, most patients after coarctation repair have a reduced exercise performance. This reduction is not related to the surgical results. Particularly, as these patients are at risk of early atherosclerosis, exercise should be promoted as primary prevention after restenosis, aortic or cerebral aneurysms, and severe exercise hypertension are ruled out.  相似文献   
984.
985.
Although the expression patterns of the members of the tumour necrosis factor receptor and ligand families have extensively been studied by flow-cytometry on stimulated peripheral blood mononuclear cells (PBMNC), little or no flow-cytometric or immunohistological data exist about their expression in lymphoid tissue. According to the data obtained from stimulated PBMNC, several members of these molecule families (e.g. CD40 ligand [CD40L], CD30, CD27, hOX40) have been considered to be either T-cell restricted or strongly T-cell associated. The present study on samples from palatine tonsils revealed that most of these molecules are also expressed by tonsillar B cells. The additional analysis of the co-expression of these molecules also disclosed the existence of CD40+/CD40L+ and CD27+/CD70+ (CD27L+) lymphoid cells in tonsillar tissue.  相似文献   
986.
S ummary . Platelet-associated IgG (PAIgG) was studied by a quantitative platelet radioactive anti-IgG test (PRAT) in 298 patients. At the time of investigation, 171 patients were thrombocytopenic (platelet count <100 × 109/1), 127 had normal platelet counts. Patients fell into the following disease categories: Idiopathic thrombocytopenic purpura (ITP) ( N =81), possible ITP (19), acute ITP (9), systemic lupus erythematosus (22), autoimmune haemolytic anaemia of warm-type (18), systemic blood disease (65), liver diseases (35), others (49). A significant elevation of PAIgG was found in all disease categories. There was a significant correlation between PAIgG and the reciprocal values of platelet counts for most disease groups. No relationship was discernible between PAIgG and hypergammaglobulinaemic states (serum IgG >1.8 g/l), Platelet survival studies ( N=30 ) revealed that normal and increased values of PAIgG were associated with normal or shortened platelet mean life span. It is concluded that an elevated PAIgG is only one of several factors involved in the development of immunologically mediated thrombocytopenia.  相似文献   
987.
Cineangiograms of 138 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) were analyzed with a computer-based coronary angiography analysis system. The results before and after dilatation are presented. In a first study group (120 patients), the severity of the obstructive lesions derived from the automatically detected contours was evaluated in absolute terms and in percent-diameter reduction. In a second group of patients, 18 coronary lesions were selected for their extreme severity and symmetric aspect before angioplasty as assessed from multiple views. In the second group, the densHometric percent-area stenosis was used to assess the changes in cross-sectional area after PTCA and was compared with the circular percent-area stenosis computed from the diameter measurements. Before PTCA, a good agreement exists between the densitometric percent-area stenosis and the circular percent-area stenosis. After PTCA, important discrepancies between these 2 types of measurements are observed. It is suggested that these discrepancies in results after PTCA can be accounted for by asymmetric morphologic changes in luminal cross section, which cannot be assessed accurately from diameter measurements in a single-plane view.  相似文献   
988.
Summary Lymphocyte kinetics was studied in 4 patients withHodgkin's disease (Stage III A and IV B) by means of a single i. v. injection of3H-thymidine (0.15 Ci/g body weight) and autoradiographic analysis of the labelling pattern of blood and tissue lymphocytes over a period of 7–25 days.The cause of the blood lymphocytopenia in the three lymphopenic patients was the accelerated turnover of the majority of the blood lymphocytes. The average turn-over time of the blood lymphocytes in these patients was about 5 days as compared to 27 days in aHodgkin patient without lymphopenia and to 50 days in non-lymphopenic tumour patients. The turnover times of the small blood lymphocytes were about 14 days in the lymphopenic Hodgkin patients and 70–115 days in hematologically normal patients. Lymphocytopoiesis seemed to be increased in the lymph nodes and in the blood inHodgkin's disease. The blood lymphocyte production index was was 61–259 lymphocytes/mm3/day as compared to 40–50 lymphocytes/mm3/day in hematologically normal patients. The generation time of the lymphopoietic cells was estimated to be approximately 24 hours.Our data suggest that the activity of the disease was correlated with accelerated turnover of lymphocytes and increased lymphocytopoiesis.
Zusammenfassung Bei 4 Patienten mit Lymphogranulomatose (Stadium III A und IV B) wurde die Kinetik von Blut- und Gewebslymphozyten nach einer Einzelinjektion von3H-Thymidin autoradiographisch untersucht.Bei den 3 lymphopenischen Patienten war die Lymphopenie des Blutes durch einen gesteigerten Umsatz der Blutlymphozyten bedingt. Die mittlere Umsatzzeit der Blutlymphozyten betrug bei diesen Patienten 5 Tage, verglichen mit einer mittleren Umsatzzeit von 27 Tagen bei einem Lymphogranulom-Patienten ohne Lymphopenie und von etwa 50 Tagen bei nicht-lymphopenischen Tumorpatienten. Die mittlere Umsatzzeit der kleinen Blutlymphozyten wurde bei den lymphopenischen Lymphogranulomatose-Patienten mit 14 Tagen und bei nicht-lymphopenischen Tumorpatienten mit 70–115 Tagen berechnet. Die Lymphozytopoese bei den Lymphogranulomatose-Patienten war erhöht. Das galt gleichermaßen für die vergrößerten Lymphknoten und das Blut. Der Blutlymphozyten-Produktionsindex betrug 61-259 Lymphozyten/mm3/Tag im Vergleich zu 40–50 Lymphozyten/mm3/Tag bei hämatologisch normalen Patienten. Die Generationszeit der lymphopoetischen Zellen ließ sich auf 24 Stunden schätzen.Die Befunde weisen darauf hin, daß bei der Lymphogranulomatose die Aktivität des Krankheitsprozesses mit gesteigertem Lymphozytenumsatz und stimulierter Lymphozytopoese korreliert ist.


Research carried out in the Forschergruppe für Experimentelle und Klinische Leukämieforschung, supported by the Deutsche Forschungsgemeinschaft.  相似文献   
989.
990.
The inward rectifier K+ current (K(ir)) determines the resting membrane potential of endothelial cells. Basic fibroblast growth factor (bFGF) has been shown to activate K(ir) and acts as angiogenic factor and vasodilator. In contrast, nicotine has been demonstrated to reduce endothelium-dependent vasorelaxation by increasing radical formation. Aim of the present study was to investigate whether nicotine modulates K(ir) and if this plays a role in bFGF-mediated proliferation, migration and nitric oxide (NO)-formation of endothelial cells. Using the patch-clamp technique in cultured endothelial cells of human umbilical cord veins (HUVEC), we found characteristic K(ir), which were blocked by extracellular barium (100 micromol/l). Perfusion with nicotine (1 nmol/l-10 micromol/l) revealed a dose-dependent reduction of K(ir). The simultaneous perfusion with bFGF (50 ng/ml) and nicotine (10 micromol/l) still significantly reduced K(ir) (n = 8; P < 0.01). Cell counts revealed that bFGF-mediated proliferation of HUVEC was significantly inhibited when using 1-10 micromol/l nicotine (n = 8, P < 0.01). The bFGF-induced endothelial cell migration--examined using the "Fences-Migration-Assay"--was significantly reduced by 10 mumol/l nicotine (n = 12; P < 0.05). NO-production was examined using a cGMP-Radioimmunoassay. The significant bFGF-induced increase of cGMP-levels was reduced by nicotine (n = 10; P < 0.05). Our data indicate that the modulation of K(ir) seems to be an essential pathway in the antagonistic effects of nicotine on bFGF-mediated endothelial cell growth, migration and NO-formation.  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