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   1081篇
  免费   20篇
  国内免费   48篇
耳鼻咽喉   2篇
儿科学   40篇
妇产科学   4篇
基础医学   90篇
口腔科学   23篇
临床医学   112篇
内科学   326篇
皮肤病学   21篇
神经病学   29篇
特种医学   147篇
外科学   57篇
综合类   24篇
预防医学   151篇
眼科学   14篇
药学   63篇
中国医学   3篇
肿瘤学   43篇
  2024年   2篇
  2023年   3篇
  2022年   15篇
  2021年   9篇
  2020年   7篇
  2019年   7篇
  2018年   8篇
  2017年   10篇
  2016年   9篇
  2015年   28篇
  2014年   26篇
  2013年   30篇
  2012年   33篇
  2011年   37篇
  2010年   38篇
  2009年   36篇
  2008年   35篇
  2007年   67篇
  2006年   30篇
  2005年   21篇
  2004年   21篇
  2003年   29篇
  2002年   40篇
  2001年   34篇
  2000年   20篇
  1999年   25篇
  1998年   51篇
  1997年   50篇
  1996年   58篇
  1995年   35篇
  1994年   34篇
  1993年   26篇
  1992年   15篇
  1991年   19篇
  1990年   13篇
  1989年   38篇
  1988年   33篇
  1987年   25篇
  1986年   22篇
  1985年   16篇
  1984年   15篇
  1983年   6篇
  1982年   16篇
  1981年   11篇
  1980年   14篇
  1979年   5篇
  1978年   5篇
  1977年   5篇
  1976年   6篇
  1975年   7篇
排序方式: 共有1149条查询结果,搜索用时 15 毫秒
41.
CD40 was originally described as a B-cell-restricted antigen and was subsequently found to be a member of the tumor necrosis factor (TNF) receptor superfamily. CD40 is also expressed on dendritic cells, thymic epithelium, monocytes, and some carcinoma cell lines, and plays a critical role in cell contact-dependent activation. Primary and cultured Hodgkin and Reed-Sternberg (H-RS) cells, the presumed malignant cells of Hodgkin's disease (HD); were found to express high levels of cell surface CD40. We found that recombinant CD40 ligand (CD40L) induced interleukin-8 (IL-8) secretion and enhanced IL-6, TNF, and lymphotoxin-alpha (LT-alpha/TNF-beta) release from cultured H-RS cells. These cytokines play a significant role in the clinical presentation and pathology of HD, a tumor of cytokine-producing cells. CD40L had no mitogenic activity for HD-derived cell lines. In contrast, CD40L enhanced expression of costimulatory molecules intracellular adhesion molecule-T and B7-1 on cultured H-RS cells, both of which are overexpressed on primary H-RS cells. In addition, CD40L induced a 40% to 60% reduction of the expression of the HD-associated CD30 antigen, another member of the TNF receptor superfamily. Primary and cultured H- RS cells express not only CD30, but also CD40. CD40L has pleiotropic biologic activities on H-RS cells, and the CD40-CD40L interaction might be a critical element in the deregulated cytokine network and cell contact-dependent activation cascade typical for HD.  相似文献   
42.
Previous work has shown failure of engraftment in lethally irradiated dogs when autologous marrow was depleted of Ia-positive cells with an anti-Ia antibody and complement before infusion. In the current study, we have utilized an avidin-biotin immunoadsorption procedure to obtain a population of highly enriched Ia-positive cells for autologous bone marrow transplantation in dogs given lethal irradiation. Dog marrow cells (2.4 to 7.0 X 10(9) cells) that contained 8.6% to 19.9% Ia- positive cells were treated successively with monoclonal antibody 7.2, which reacts with a framework determinant of Ia-antigen, and biotin- conjugated goat antimouse immunoglobulin. These treated cells were passed over a column of avidin-Biogel (polyacrylamide) and the adherent cells removed by mechanical agitation. Seven lethally irradiated dogs were transplanted with 5.9 to 33.4 X 10(6) recovered adherent cells per kilogram of which 69.0% to 88.0% were Ia-positive. All dogs had hematologic recovery; six are alive and well with durable engraftment and one died on day 15 posttransplant. They are immunologically normal as determined by lymph node and bone marrow biopsies, lymphocyte function, and immunophenotyping of peripheral blood and bone marrow cells. These data provide further evidence that canine hematopoietic stem cells express Ia-like antigens and that these cells are capable of complete hematopoietic and immunologic reconstitution in an autologous model.  相似文献   
43.
AIM:To investigate whether celiac disease(CD)patients with tissue-transglutaminase antibody(tTGA)≥100 U/mL are different from patients with lower tTGA levels.METHODS:Biopsy-proven(MarshⅢ)pediatric CD patients(n=116)were prospectively included between March 2009 and October 2012.The biopsies were evaluated by a single pathologist who was blinded to all of the patients’clinical data.The patients were distributed into 2 groups according to their tTGA level,which was measured using enzyme-linked immunoassay:tTGA≥100 U/mL and Ttga<100 U/mL.The patients’characteristics,symptoms,human leukocyte antigen(HLA)genotype and degree of histological involvement were compared between the 2 groups.RESULTS:A total of 34(29.3%)children had tTGA values<100 U/mL and 82(70.7%)tTGA levels of≥100 U/mL.Patients with high tTGA levels had lower average body weight-for-height standard deviation scores(SDS)than did patients with tTGA<100 U/mL(-0.20±1.19 SDS vs 0.23±1.03 SDS,P=0.025).In the low tTGA group,gastrointestinal symptoms were more common(97.1%vs 75.6%,P=0.006).More specifically,abdominal pain(76.5%vs 51.2%;P=0.012)and nausea(17.6%vs 3.7%,P=0.018)were more frequent among patients with low tTGA.In contrast,patients with solely extraintestinal manifestations were only present in the high tTGA group(18.3%,P=0.005).These patients more commonly presented with aphthous stomatitis(15.9%vs 0.0%,P=0.010)and anemia(32.9%vs 11.8%,P=0.019).In addition,when evaluating the number of CD-associated HLA-DQ heterodimers(HLA-DQ2.5,HLA-DQ2.2 and HLA-DQ8),patients with low tTGA levels more commonly had only1 disease-associated heterodimer(61.8%vs 31.7%,P=0.005),while patients with high tTGA more commonly had multiple heterodimers.Finally,patients with tTGA≥100 U/mL more often had a MarshⅢc lesion(73.2%vs 20.6%,P≤0.001)while in patients with low tTGA patchy lesions were more common(42.4%vs6.8%,P≤0.001).CONCLUSION:Patients with tTGA≥100 U/mL show several signs of more advanced disease.They also carry a larger number of CD  相似文献   
44.

Background

Through effects on nitric oxide (NO) bioavailability, endothelial function is improved after the intake of beetroot juice–which is rich in inorganic nitrate-, but decreased after the intake of a meal.

Objective

The objective of this study was to examine if beetroot juice could counteract the impairment of endothelial function associated with the ingestion of a mixed meal.

Methods

Twenty healthy overweight and slightly obese men with a BMI between 28 and 35 kg/m2 received in random order a mixed meal providing 56.6 g of fat with beetroot juice or a control drink. The beetroot juice (140 mL) provided approximately 500 mg dietary nitrate. Flow-mediated dilation (FMD) of the brachial artery was measured before and 2 h after meal consumption. Blood was sampled at regular intervals.

Results

Postprandial changes in serum triacylglycerol (TAG) (P = 0.69), plasma glucose (P = 0.84) and insulin (P = 0.67) concentrations were comparable between the meals. After consumption of beetroot juice, the postprandial impairment in FMD following a standardized mixed meal was improved (P = 0.030) compared with the control drink (−0.37 ± 2.92% versus −1.56 ± 2.90%). Following beetroot juice consumption, plasma concentrations of the circulating NO pool were higher at T60, T120, and T240 (P < 0.001 at all time points).

Conclusion

In healthy overweight and slightly obese men a single dose of beetroot juice attenuates the postprandial impairment of FMD following a mixed meal, possibly through increases in plasma NO concentrations.  相似文献   
45.
AIM: To demonstrate the range of applying laser angioplasty after unsuccessful recanalization of the superficial femoral artery (SFA) with conventional interventional techniques. MATERIALS AND METHODS: In a prospective trial in 94 cases with occlusion of the SFA and formerly unsuccessful conventional percutaneous transluminal angioplasty, laser angioplasty for recanalization was applied. The average length of the SFA was 17.5 cm (range 4–36 cm). The recanalization attempt was made using the crossover technique in 78 patients, in eight patients with the antegrade technique and in another eight patients using the transpopliteal technique. The primary recanalization attempt was performed with Terumo wires (curved and straight) as well as different catheters (Multipurpose/Vertebralis/Cobra). the unsuccessful recanalization attempt the laser catheter was applied. RESULTS: The application of laser angioplasty demonstrated a successful recanalization of the SFA in 76/94 patients (80.9%). In 18 patients (19.1%) the recanalization was not possible even with percutaneous transluminal laser angioplasty (PTLA). The reason for the unsuccessful PTLA was in 10 cases due to obstructing calcified material, which was resistant to PTLA application. In four cases obstructing calcifications caused the laser catheter to be positioned in subintimal tissue, resulting in perforation occlusion of the SFA. In another four patients there was an aberrant anatomy of the SFA which resulted in a direct vessel injury after advancing the laser catheter. After a follow-up period of 12 months primary, primary-assisted and secondary patency rates were 50.0%, 65.8% and 73.7%, respectively. DISCUSSION: In primarily unsuccessful recanalization of the SFA, PTLA allows in After 80% of cases a successful recanalization of the SFA. The technical success rate and the patency rate support the application of PTLA. (Int J Cardiovasc 2000; 3: 153–160)  相似文献   
46.
BACKGROUND AND AIM: Common variations in genes, such as apolipoprotein E (apo E) and cholesteryl ester transfer protein (CETP), are major determinants of plasma lipid and lipoprotein levels. As both apo E and CETP contribute to the reverse transport of cholesterol to the liver, the effects of variations at the CETP locus may very well interact with the apo E genotype. METHODS AND RESULTS: As part of an ongoing study, the combined effects of the apo E genotype and heterogeneity at the CETP gene locus on plasma lipids and lipoproteins were studied in a birth cohort sample of 257 Dutch prepubescent boys and girls (aged 6.7-8.1 years). The children with an apo E2E3 genotype (carrying the epsilon 2 allele; arg158-->cys) had lower concentrations of low-density lipoprotein cholesterol (LDL-C) and apolipoprotein B (apo B) than those with an apo E4E3 (carrying the epsilon 4 allele; cys112-->arg) or apo E3E3 genotype (homozygous for the parent epsilon 3 allele). These associations were statistically significant in children who were homozygous (p = 0.004 for LDL; p = 0.002 for apo B) or heterozygous (p < 0.0001 for LDL and apo B) for the absence of the Taq-IB polymorphism at the CETP gene locus (B2 allele), but not in those homozygous for the presence of this variant (B1B1). The highest plasma high-density lipoprotein cholesterol (HDL-C) concentrations were observed in children with the CETP B2B2 genotype. The difference in HDL-C levels between the CETP genotype groups was statistically significant only in E2E3 carriers (p = 0.01). The LDL/HDL ratio was significantly lower in E2E3 carriers, but not when combined with a CETP B1B1 genotype. CONCLUSION: These findings indicate that the apo E genotype and heterogeneity at the CETP gene locus have an additive and interactive influence on plasma lipid and lipoprotein levels in children.  相似文献   
47.
Non-occlusive mesenteric ischaemia is characterized by gastrointestinal ischaemia with normal vessels. In gastroenterology it is recognized as rare disease occasionally causing acute bowel infarction or ischaemic colitis. From intensive care literature this disorder is recognized as an early phenomenon during circulatory stress. This early mucosal ischaemia then leads to increased permeability, bacterial translocation, and further mucosal hypoperfusion. The damage is produced mainly during reperfusion following ischaemia with fresh inflow of oxygen and outflow of waste products into the systemic circulation.The mechanisms underlying non-occlusive mesenteric ischaemia include macrovascular vasoconstriction, hypoperfusion of the tips of the villi and shunting. It is very common in critically ill and perioperative patients, but also occurs in pancreatitis, renal failure and sepsis.Treatment options include aggressive fluid resuscitation and careful choice of vasoactive drugs. Control of reperfusion damage and new endothelin-antagonists are potentially useful new treatment options.  相似文献   
48.
Background and aimsExtensive research showed a diurnal rhythm of endogenous cholesterol synthesis, whereas recent research reported no diurnal rhythm of intestinal cholesterol absorption in males who consumed low-fat meals. Little is known about the acute effect of macronutrient consumption on cholesterol metabolism, and hence if meal composition may explain this absence of rhythmicity in cholesterol absorption. Therefore, we examined the effect of a high-fat, high-carbohydrate, and high-protein meal on postprandial intestinal cholesterol absorption and endogenous cholesterol synthesis in apparently healthy overweight and slightly obese males.Methods and resultsEighteen males consumed in random order an isoenergetic high-fat, high-carbohydrate, and high-protein meal on three occasions. Serum total cholesterol concentrations, cholesterol absorption markers (campesterol, cholestanol, and sitosterol), and cholesterol synthesis intermediates (7-dehydrocholesterol, 7-dehydrodesmosterol, desmosterol, dihydrolanosterol, lanosterol, lathosterol, zymostenol, and zymosterol) were measured at baseline (T0) and 240 min postprandially (T240). Meal consumption did not significantly change total cholesterol concentrations and cholesterol absorption marker levels (all p > 0.05). Serum levels of 7-dehydrocholesterol, lanosterol, lathosterol, zymostenol, and zymosterol decreased significantly between T0 and T240 (all p < 0.05). These decreases were not significantly different between the three meals (all p > 0.05), except for a larger decrease in dihydrolanosterol levels after the high-fat versus the high-carbohydrate meal (p = 0.009).ConclusionThe high-fat, high-carbohydrate, and high-protein meal did not significantly influence postprandial intestinal cholesterol absorption. Several cholesterol synthesis intermediates decreased postprandially, but the individual macronutrients did not differentially affect these intermediates, except for a possible effect on dihydrolanosterol.Trial registrationClinicalTrials.gov, NCT03139890.  相似文献   
49.
Plat J  Mensink RP 《Atherosclerosis》2000,148(1):101-112
A pine wood based stanol ester mixture-composed of sitostanol (92%) and campestanol (8%) effectively lowers cholesterol absorption and consequently LDL-cholesterol concentrations. It has been postulated that the less absorbable plant sterols reduce cholesterol absorption more effectively. As sitostanol is absorbed less than campestanol, we decided to examine if a vegetable oil based stanol ester mixture with 68% sitostanol and 32% campestanol is less effective than the wood based stanol ester mixture. For this, 112 non-hypercholesterolemic men and women consumed for 4 weeks a rapeseed oil (LEAR) based margarine and shortening. For the next 8 weeks, 42 subjects continued with these products, while the other subjects received products with a vegetable oil (n=36) or a pine wood based stanol ester mixture (n=34). Consumption of 3.8 g vegetable oil based stanols (2.6 g sitostanol plus 1.2 g campestanol) lowered LDL cholesterol 14.6+/-8.0% (-0.37 mmol/l; vs. the control group; P<0.001; 95% CI for the difference, -0.22 to -0. 51 mmol/l). Four grams pine wood based stanols (3.7 g sitostanol plus 0.3 g campestanol) showed a comparable decrease of 12.8+/-11.2% (-0.34 mmol/l; P<0.001; 95% CI-0.18 to-0.51 mmol/l). Decreases in LDL cholesterol were not different between the two experimental groups (P=0.793), while apoE genotype did not have a major impact on this hypocholesterolemic response. Serum HDL cholesterol and triacylglycerol concentrations were not changed. The decreases in apo B in both experimental groups differed significantly (P<0.001) from changes in the control group. Coagulation and fibrinolytic parameters were not affected. We therefore conclude that vegetable oil and wood based stanol ester mixtures, with a different sitostanol/campestanol ratio, have similar LDL cholesterol lowering effects in a non-hypercholesterolemic population.  相似文献   
50.
Ehninger  G; Schuler  U; Renner  U; Ehrsam  M; Zeller  KP; Blanz  J; Storb  R; Deeg  HJ 《Blood》1995,85(11):3247-3249
In a canine model we investigated the toxicity and pharmacokinetics of a water soluble busulfan preparation. Busulfan was dissolved in dimethylsulfoxide (DMSO) and administered either orally or intravenously in a single dose of 1 mg/kg. The application in either preparation was well tolerated. In seven dogs, peak levels in the range of 730 ng/mL to 1,000 ng/mL were measured after intravenous injection with an area under curve (AUC) of 75 ng.h/kg.mL to 146 ng.h/kg.mL. It was of note that even the oral administration of the same busulfan preparation resulted in AUC values in the same range as observed after parenteral application. The absorption rate of busulfan tablets in our model was as unpredictable as documented in clinical trials. On the basis of the present study, clinical trials using busulfan dissolved in DMSO given either intravenously or orally appear warranted. This approach should lead to predictable blood levels, reduced toxicity, and increased efficacy of busulfan-containing regimens.  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