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   2005篇
  免费   107篇
  国内免费   6篇
耳鼻咽喉   6篇
儿科学   55篇
妇产科学   77篇
基础医学   297篇
口腔科学   39篇
临床医学   145篇
内科学   517篇
皮肤病学   67篇
神经病学   223篇
特种医学   59篇
外科学   120篇
综合类   10篇
预防医学   75篇
眼科学   13篇
药学   191篇
中国医学   1篇
肿瘤学   223篇
  2024年   6篇
  2023年   16篇
  2022年   33篇
  2021年   63篇
  2020年   34篇
  2019年   45篇
  2018年   50篇
  2017年   37篇
  2016年   66篇
  2015年   47篇
  2014年   68篇
  2013年   81篇
  2012年   141篇
  2011年   162篇
  2010年   91篇
  2009年   85篇
  2008年   130篇
  2007年   160篇
  2006年   153篇
  2005年   126篇
  2004年   114篇
  2003年   113篇
  2002年   99篇
  2001年   13篇
  2000年   10篇
  1999年   16篇
  1998年   17篇
  1997年   23篇
  1996年   11篇
  1995年   16篇
  1994年   19篇
  1993年   15篇
  1992年   3篇
  1991年   7篇
  1990年   4篇
  1989年   7篇
  1988年   7篇
  1986年   2篇
  1985年   5篇
  1984年   3篇
  1983年   3篇
  1982年   3篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1976年   1篇
  1975年   1篇
  1972年   1篇
  1965年   1篇
  1964年   1篇
排序方式: 共有2118条查询结果,搜索用时 15 毫秒
81.
82.
PURPOSE: Point mutations within the ABL kinase domain of the BCR-ABL gene have been associated with clinical resistance to imatinib mesylate in chronic myeloid leukemia (CML) patients. To shed further light on the frequency, distribution, and prognostic significance of ABL mutations, we retrospectively analyzed a homogeneous cohort of late chronic phase CML patients who showed primary cytogenetic resistance to imatinib. PATIENTS AND METHODS: Using denaturing high-performance liquid chromatography (D-HPLC) and sequencing, we screened for ABL mutations in a total of 178 bone marrow and/or peripheral blood samples from 40 late chronic phase CML patients homogeneously treated with imatinib 400 mg/d, who did not reach a major cytogenetic response at 12 months. RESULTS: Mutations were found in 19 of 40 patients (48%). Mutations were already detectable by D-HPLC at a median of 3 months from the onset of therapy. The presence of a missense mutation was significantly associated with a greater likelihood of subsequent progression to accelerated phase/blast crisis (P = .0002) and shorter survival (P = .001). Patients carrying mutations falling within the P-loop seemed to have a particularly poor outcome in terms of time to progression (P = .032) and survival (P = .045). CONCLUSION: Our results show that, irrespective of the hematologic response, monitoring for emerging mutations in the first months of therapy may play a role in detecting patients with worse prognosis, for whom a revision of the therapeutic strategy should be considered.  相似文献   
83.
BackgroundInfluenza is an important public health problem, with potential severe consequences among people with chronic diseases. The aim of this study was to obtain reliable measures of seasonal influenza vaccine uptake in this population, otherwise not available in Italy.MethodsProgressi delle Aziende Sanitarie per la Salute in Italia (PASSI) is a nationwide surveillance system of health-related behaviours and acceptance of preventive interventions (including influenza immunisation) offered by the Italian National Health Service. Data are collected with telephone interviews at local health unit level for supporting local activities. The survey sample is randomly selected from local health unit lists of adult residents. The trend of annual vaccine coverage since 2008 was estimated for people aged 18–64 years who reported having at least one chronic disease. To obtain a sufficient sample size in subgroups, we analysed the characteristics of vaccinated people in the 2010–13 cumulative dataset. Univariate, multivariate, and logistic regression analyses were undertaken.FindingsIn 2008–13, 13 659 individuals with at least one chronic disease were interviewed. Vaccination coverage fell significantly from 29·7% (95% CI 27·2–32·4) in 2007–08 to 19·9% (18·0–22·1) in 2012–13. During 2010–13, the overall proportion of vaccinated people with a chronic disease was 25·6% (24·5–26·7). Vaccine coverage of people with diabetes (34·3%, 31·7–36·9) or cardiovascular diseases (31·8%, 29·6–34·2) was greater than that of people affected by renal failure, respiratory diseases, tumours, or chronic liver diseases (26·5% [22·5–30·7], 24·9% [23·2–26·7], 22·2% [20·0–24·6], and 20·6% [17·5–24·6], respectively). Vaccination coverage increased with age (from 13·1% [11·0–15·5] in the 18–34 year age group to 33·4% [31·9–35·1] in people aged 50–64 years); it was higher among people with a low educational level than among those with a high educational level, higher in those having economic difficulties than in those with no economic difficulties, and higher among Italian citizens than among non-citizens.InterpretationIn the past few years, prevalence of influenza vaccination in Italian adults with at least one chronic disease was well below the Ministry of Health's goal (75% minimum) and showed a downward trend. A major reason of this evolution is probably the changing public perception of the benefits and risks of vaccines. PASSI is a source of useful data not otherwise available for public health intervention.FundingItalian Ministry of Health.  相似文献   
84.
Summary Intraperitoneal (i.p.) 5-fluoro-2-deoxyuridine (Floxuridine, FUdR, FdUrd) was evaluated in a phase I study at a starting level of 500 mg given on 1 day in 2 I 1.5% dialysate. Escalations within patients were allowed every other cycle. A total of 23 patients (age, 32–78 years) received 108 treatment courses. Local tolerance at all dose levels was excellent, with no cases of drug-related peritonitis being observed. Nausea and vomiting increased in severity in relation to dose and was universal at >3,000 mg ×3 days. One patient each developed grade 1 mucositis as well as diarrhea at a dose of 3,000 mg×3 days and leukopenia and thrombocytopenia at 5,000 mg×3 days. Peritoneal fluid (PF) and plasma (PL) FdUrd profiles were monitored by an HPLC method in 13 subjects, with 7 being studied serially at 2–4 increment doses for up to 6 h. Profiles that exhibited apparent linear pharmacokinetics gave PF drug levels 2–4 logs higher than the PL counterparts, with the latter essentially declining in parallel to the former, indicating that the disposition of FdUrd from the peritoneal compartment is rate-determining. The mean terminal half-life for PF FdUrd was found to be 115 min and mean peritoneal clearance was 25 ml/min. The vast differences in drug levels and AUC found between the PF and the PL profiles suggests a high systemic clearance of FdUrd, which was confirmed in two patients receiving 2 g FdUrd by short i.v. infusion. A disproportionate increase in the plasma FdUrd levels and the corresponding AUC values was found with increasing dose, suggesting a disproportionate increase in the systemic partitioning of FdUrd when doses were escalated within a patient. Substantial levels of peritoneal 5-fluorouracil (FUra) were also detected in most of the subjects. Thus, FdUrd was found to have several desirable properties for i.p. administration: (1) a 2- to 4-log pharmacologic advantage, (2) the absence of local toxicities, and (3) a favorable antitumor spectrum and some evidence of antitumor effects in this phase I and pharmacology study. A 3,000-mg dose given in 2 l 1.5% dialysate for 3 consecutive days exhibited antitumor activity and produced no systemic toxicity except nausea and vomiting, which was controlled by antiemetics. This dose schedule is therefore recommended for phase II trials directed against small-volume disease in the peritoneal cavity, such as may be found in some stages of ovarian and gastrointestinal cancers. In addition, it is suitable for further exploration as a part of regimens including systemic therapy or drugs that modulate the action of fluoropyrimidines.Supported in part by Cancer Center Core Grant CA 14089, by ROI CA 50 412, by an ACS Institutional Grant (IN21Z, to C. R.) and by the Italian-American Foundation award (to N. C.)Deceased  相似文献   
85.
86.
HIV coreceptor tropism (CTR) testing is a prerequisite for prescribing a coreceptor antagonist. CTR is increasingly deduced by analyzing the V3 loop sequence of gp120. We investigated the impact of mutations outside V3 on CTR as determined by the enhanced-sensitivity Trofile assay (ESTA). Paired ESTA and gp120 sequencing (population sequencing; from codon 32 of the conserved C1 to the variable V5 domains) were obtained from 60 antiretroviral treatment (ART)-naïve patients (15 with AIDS) infected with subtype B HIV-1. For gp120 sequence analysis, nucleotide mixtures were considered when the second highest electropherogram peak was >25%; sequences were translated into all possible permutations and classified as X4, dual/mixed (DM), and R5 based on coincident ESTA results. ESTA identified R5 and DM viruses in 72 and 28% of patients, respectively; no pure X4 was labeled. Forty percent of AIDS patients had R5 strains. Thirty-two positions, mostly outside V3, were significantly (P < 0.05) different between R5 and DM sequences. According to multivariate analysis, amino acid changes at 9 and 7 positions within the C1 to C4 and V1 to V5 regions, respectively, maintained a statistical significance, as did the net charge of V3 and C4. When analyzing only R5 sequences, 6 positions in the variable regions were found which, along with the V4 net charge, were significantly different for sequences from early- and end-stage disease patients. This study identifies specific amino acid changes outside V3 which contribute to CTR. Extending the analysis to include pure X4 and increasing the sample size would be desirable to define gp120 variables/changes which should be included in predictive algorithms.  相似文献   
87.
Recently, we identified 2-styrylchromones as a new class of antirhinovirus flavonoids with moderate activity against both rhinovirus groups A and B. In order to improve the antiviral effect of the first series of tested 2-styrylchromones, a hydroxy or methoxy group was introduced in position 3 of the chromone ring. Cytotoxicity and antiviral activity of the new synthesized compounds were evaluated in HeLa cell cultures infected with rhinoviruses 1B and 14, selected as representative serotypes for viral groups B and A of human rhinoviruses (HRVs), respectively. These antiviral results compared to those obtained for 3-unsubstituted 2-styrylchromones indicate the greater potency of 3-hydroxy and 3-methoxy derivatives against both serotypes.  相似文献   
88.
Two new quinolizidinyl-alkyl derivatives of 7-chloro-4-aminoquinoline, named AM-1 and AP4b, which are highly effective in vitro against both the D10 (chloroquine [CQ] susceptible) and W2 (CQ resistant) strains of Plasmodium falciparum and in vivo in the rodent malaria model, have been studied for their ability to bind to and be internalized by normal or parasitized human red blood cells (RBC) and for their effects on RBC membrane stability. In addition, an analysis of the heme binding properties of these compounds and of their ability to inhibit beta-hematin formation in vitro has been performed. Binding of AM1 or AP4b to RBC is rapid, dose dependent, and linearly related to RBC density. Their accumulation in parasitized RBC (pRBC) is increased twofold compared to levels in normal RBC. Binding of AM1 or AP4b to both normal and pRBC is higher than that of CQ, in agreement with the lower pKa and higher lipophilicity of the compounds. AM1 or AP4b is not hemolytic per se and is less hemolytic than CQ when hemolysis is accelerated (induced) by hematin. Moreover, AM-1 and AP4b bind heme with a stoichiometry of interaction similar to that of CQ (about 1:1.7) but with a lower affinity. They both inhibit dose dependently the formation of beta-hematin in vitro with a 50% inhibitory concentration comparable to that of CQ. Taken together, these results suggest that the antimalarial activity of AM1 or AP4b is likely due to inhibition of hemozoin formation and that the efficacy of these compounds against the CQ-resistant strains can be ascribed to their hydrophobicity and capacity to accumulate in the vacuolar lipid (elevated lipid accumulation ratios).Chloroquine (CQ) has been effectively used for decades as an antimalarial drug for its efficacy, safety, and stability but is now largely ineffective because of widespread parasite resistance. This has led to the necessity of utilizing artemisinin-based combination therapy as a first-line treatment for uncomplicated malaria (20). However, the recent reports of artemisinin-based combination therapy treatment failure in southeast Asia and the potential emergence of artemisinin resistance (26) indicate that the search for new drugs or new drug combinations is still highly necessary (40, 41). Quinoline-type antimalarials remain an attractive class of compounds because their mechanism of action and resistance are unrelated (14) and resistance has emerged very slowly over time. CQ and quinoline antimalarial drugs are thought to kill parasites by inhibiting the process of crystallization necessary to detoxify ferriprotoporphyrin IX (FP) into hemozoin (HZ) (5, 30, 34). This process is vital for Plasmodium falciparum and can be reproduced in vitro with hematin under acidic conditions, leading to the formation of beta-hematin (BH), a crystal product showing physicochemical properties identical to those of HZ (29).FP in the food vacuole of the parasite is considered the target of quinoline antimalarials (6, 15). The inhibition of HZ formation leads to the accumulation of free FP, potentially toxic for its prooxidant and lytic activities (7, 27). The resistance mechanism of CQ is based on the reduced drug accumulation at the site of action, the food vacuole, due to mutation of PfCRT (P. falciparum CQ resistance transporter) (5, 16, 39) and does not involve modification of the target.In the last few years, the research of our group has been directed to the study of new quinolizidinyl and quinolizidinyl-alkyl derivatives of 7-chloro-4-aminoquinoline (33). The terminal quinolizidine ring (octahydro-2H-quinolizine) confers basicity and lipophilicity to the molecules and prevents the metabolic oxidative dealkylation known to limit the usefulness of quinoline derivatives (28). Lead candidates have been obtained that are very stable and highly effective in vitro against both the D10 (CQ susceptible [CQ-S]) and W2 (CQ resistant [CQ-R]) strains of P. falciparum (33) and in vivo in the murine Plasmodium berghei model (23). Two of these compounds, named AM-1 and AP4b, have been selected for further characterization (Fig. (Fig.1):1): AM-1, a pure enantiomer, is semisynthetic and derives from l-lupinine, a natural alkaloid extracted from the seeds of Lupinus luteus; AP4b is synthetic and a racemate.Open in a separate windowFIG. 1.Molecular structures of the compounds used in the study.For the present article, we evaluated the binding of these compounds to human red blood cells (RBC), normal or parasitized by the P. falciparum strain D10 or W2. In addition, an analysis of the heme binding properties of these compounds and of their ability to affect RBC membrane stability and inhibit FP crystallization in vitro has been performed.  相似文献   
89.
90.
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