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   19058篇
  免费   1378篇
  国内免费   44篇
耳鼻咽喉   180篇
儿科学   654篇
妇产科学   510篇
基础医学   2583篇
口腔科学   200篇
临床医学   2319篇
内科学   3544篇
皮肤病学   333篇
神经病学   1957篇
特种医学   539篇
外国民族医学   5篇
外科学   2135篇
综合类   151篇
一般理论   16篇
预防医学   2350篇
眼科学   273篇
药学   1220篇
中国医学   13篇
肿瘤学   1498篇
  2024年   34篇
  2023年   248篇
  2022年   460篇
  2021年   849篇
  2020年   445篇
  2019年   802篇
  2018年   878篇
  2017年   615篇
  2016年   659篇
  2015年   707篇
  2014年   948篇
  2013年   1108篇
  2012年   1704篇
  2011年   1682篇
  2010年   841篇
  2009年   714篇
  2008年   1174篇
  2007年   1151篇
  2006年   1042篇
  2005年   984篇
  2004年   895篇
  2003年   715篇
  2002年   649篇
  2001年   84篇
  2000年   91篇
  1999年   83篇
  1998年   134篇
  1997年   94篇
  1996年   72篇
  1995年   57篇
  1994年   56篇
  1993年   45篇
  1992年   41篇
  1991年   35篇
  1990年   20篇
  1989年   27篇
  1988年   38篇
  1987年   32篇
  1986年   21篇
  1985年   24篇
  1984年   26篇
  1983年   16篇
  1982年   12篇
  1981年   11篇
  1980年   14篇
  1979年   10篇
  1978年   18篇
  1977年   9篇
  1976年   18篇
  1973年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
PURPOSE: To assess the efficacy and toxicity of bortezomib (Velcade; Milennium Pharmaceuticals Inc, Cambridge, MA; formerly PS-341) in patients with metastatic renal cell carcinoma (RCC). PATIENTS AND METHODS: Thirty-seven patients with metastatic RCC were treated with bortezomib. The first 25 patients enrolled onto the trial were treated with a dose of 1.5 mg/m2. The dose was decreased to 1.3 mg/m2 for the subsequent 12 patients, because more than 50% of the patients treated at the higher dose required dose reductions. Bortezomib was given by intravenous administration on a twice-weekly schedule for 2 weeks followed by 1 week without treatment until progression or unacceptable toxicity occurred. Twenty-three patients (62%) previously had undergone nephrectomy, and 19 patients (51%) had previously been treated with cytokine therapy. RESULTS: Of the 37 assessable patients, the best response was a partial response in four patients (11%; 95% CI, 3% to 25%) and stable disease in 14 patients (38%; 95% CI, 23% to 55%). The four patients with partial response experienced response durations of 8, 8+, 15+, and 20+ months. Grade 2 or 3 sensory neuropathy was present in 10 patients (53%) overall. One patient in the 1.5 mg/m2 group had grade 3 sensory neuropathy; no grade 3 sensory neuropathy was seen in the 1.3 mg/m2 group. CONCLUSION: The results of this trial suggest that bortezomib has an antitumor effect in individual patients with metastatic RCC. The small proportion of patients who achieved a partial response does not support routine use in metastatic RCC. Efforts to identify the molecular profile associated with clinical response or combination therapy with interferon alfa or other novel agents, may be considered.  相似文献   
132.
PURPOSE: Recent studies have found an association between certain TP53 mutations and resistance to anthracycline-based primary medical therapy in breast cancer. The purpose of this study was to investigate whether TP53 mutational status also might influence the response to a non-anthracycline-containing regimen in primary breast cancer. EXPERIMENTAL DESIGN: Thirty-five patients with locally advanced breast cancer were investigated for TP53 mutations before receiving combination chemotherapy with 5-fluorouracil (1000 mg/m(2) on days 1 and 2) and mitomycin (6 mg/m(2) on day 2), administered every 3 weeks for 2-10 cycles in the neoadjuvant setting. RESULTS: Mutations in the TP53 gene, in particular those affecting loop domains L2 or L3 of the p53 protein, were associated with lack of response to chemotherapy (i.e., increase in the diameter product of tumor lesion by >/=25%; P = 0.177 for all mutations and P = 0.006 for those affecting L2/L3 domains, respectively). No statistically significant correlation between TP53 LOH and response to therapy was seen. CONCLUSION: This study revealed a significant association between lack of response to 5-fluorouracil and mitomycin and mutations affecting the L2/L3 domains of the p53 protein. Together with our previous finding that such mutations predict resistance to weekly doxorubicin, our data suggest that mutations affecting this particular domain of the p53 protein may cause resistance to several different cytotoxic compounds applied in breast cancer treatment.  相似文献   
133.
BACKGROUND/PURPOSE: Although the mortality, morbidity, and spectrum of associated injuries in children with pelvic fractures have been extensively studied, little is known about the functional outcomes in these patients. The authors examined retrospectively functional independence measurement (FIM) at discharge in children with pelvic fractures to determine how it should influence their management protocol. METHODS: The authors reviewed the records of all patients who sustained pelvic fractures between 1993 and 1998 in the trauma registry of a level I pediatric trauma center. Patients were stratified according to demographics, type of pelvic fracture, functional independence measurement, and discharge disposition. Fractures graded 1, 2, or 3 were defined as stable, whereas grade 4 fractures were deemed unstable. RESULTS: A total of 88 children sustained pelvic fractures. Seventy-four percent had stable fractures, whereas 26% sustained unstable fractures. There was no difference in age or sex between the groups; boys were more commonly injured than girls. Motor vehicle-related crashes accounted for most injuries. The mean injury severity score (ISS) for patients with a stable fracture was 17 +/- 14 and 20 +/- 13 for unstable fractures. There was no difference in overall hospitalization nor intensive care unit stay between the unstable and stable fracture patients. Eighty percent of the patients with unstable and 52% of the patients with stable pelvic fractures were dependent based on locomotion, and similar proportions were seen for the transfer category. CONCLUSIONS: Short-term function appears to be significantly impaired in a high percentage of children with stable and unstable pelvic fractures. Therefore, aggressive rehabilitation should be instituted early in all children with pelvic fractures to achieve optimal functional outcome.  相似文献   
134.
Law, which is a fundamental element of effective public health policy and practice, played a crucial role in many of public health's greatest achievements of the 20th century. Still, conceptual legal frameworks for the systematic application of law to chronic disease prevention and control have not been fully recognized and used to address public health needs. Development and implementation of legal frameworks could broaden the range of effective public health strategies and provide valuable tools for the public health workforce, especially for state and local health department program managers and state and national policy makers. In an effort to expand the range of effective public health interventions, the Centers for Disease Control and Prevention will work with its partners to explore the development of systematic legal frameworks as a tool for preventing chronic diseases and addressing the growing epidemic of obesity, heart disease, stroke, and other chronic diseases and their risk factors.  相似文献   
135.
OBJECTIVE: To describe clinician delivery of injury prevention anticipatory guidance and injury visits in a birth cohort, and to describe the association of injury prevention anticipatory guidance with subsequent injury visits. METHODS: We performed a prospective cohort study of 2610 infants born from July 1, 1998 to June 30, 1999, at an urban safety-net hospital and seen subsequently for well child care (WCC, visits = 10558) and/or injury by 16 months of age. Injury guidance was defined as the proportion of recommended injury prevention anticipatory guidance items delivered to those expected, given the WCC visits the child attended. The outcome was a first injury visit to a clinic, emergency department, or hospital. RESULTS: The injury prevention items most discussed were car seats (84%-95% of all WCC visits) and rolling over at the 2-month WCC visit (80%). Other items were addressed at 36%-69% of visits. A total of 1931 (74%) of children received > or = 50% expected injury guidance. A total of 277 children (11%) had an injury visit, primarily for minor injuries. In unadjusted analysis, children receiving < 25% expected injury guidance were more likely to have a subsequent injury visit (unadjusted odds ratio 6.2; 95% confidence interval [95% CI] 3.2-9.7). In adjusted analysis, children who received < 25% and 25%-49% expected injury guidance were more likely to have a subsequent injury visits (adjusted odds ratio [AOR] 6.6; 95% CI 3.8-11.2; and AOR 2.9, 95% CI 2.0-4.3, respectively). CONCLUSIONS: Disadvantaged children whose families received less injury guidance than other children in their cohort were more likely to have a subsequent injury visit. Further studies are needed to determine whether increased injury prevention counseling reduces injury visits.  相似文献   
136.
PURPOSE: We determined the maximum-tolerated dose (MTD) and the dose-limiting toxicities (DLT) of 17-allylamino-17-demethoxygeldanamycin (17-AAG) when infused on days 1, 8, and 15 of a 28-day cycle in advanced solid tumor patients. We also characterized the pharmacokinetics of 17-AAG, its effect on chaperone and client proteins, and whether cytochrome P450 (CYP) 3A5 and NAD(P)H:quinone oxidoreductase 1 (NQO1) polymorphisms affected 17-AAG disposition or toxicity. PATIENTS AND METHODS: An accelerated titration design was used. Biomarkers were measured in peripheral-blood mononuclear cells (PBMCs) at baseline and on days 1 and 15, and pharmacokinetic analysis was performed on day 1 of cycle 1. CYP3A5*3 and NQO1*2 genotypes were determined and correlated with pharmacokinetics and toxicity. RESULTS: Twenty-one patients received 52 courses at 11 dose levels. DLTs at 431 mg/m(2) were grade 3 bilirubin (n = 1), AST (n = 1), anemia (n = 1), nausea (n = 1), vomiting (n = 1), and myalgias (n = 1). No tumor responses were seen. 17-AAG consistently increased heat shock protein (Hsp) 70 levels in PBMCs. At the MTD, the clearance and half-life (t(1/2)) of 17-AAG were 11.6 L/h/m(2) and 4.15 hours, respectively; whereas the active metabolite 17-aminogeldanamycin had a t(1/2) of 7.63 hours. The CYP3A5*3 and NQO1*2 polymorphisms were not associated with 17-AAG toxicity. The CYP3A5*3 polymorphism was associated with higher 17-AAG clearance. CONCLUSION: The MTD of weekly 17-AAG is 308 mg/m(2). 17-AAG induced Hsp70 in PBMCs, indicating that Hsp90 has been affected. Further evaluation of 17-AAG is ongoing using a twice-weekly regimen, and this schedule of 17-AAG is being tested in combination with chemotherapy.  相似文献   
137.
PURPOSE: To assess the maximum tolerated dose, toxicities, pharmacokinetics, and antileukemic activity of topotecan and carboplatin in adults with recurrent or refractory acute leukemias. EXPERIMENTAL DESIGN: Patients received topotecan and carboplatin by 5-day continuous infusion at nine dose levels. Patients achieving a complete remission received up to two additional courses for consolidation. Plasma topotecan and ultrafilterable platinum were assayed on days 1 to 5. In addition, pretreatment levels of various polypeptides in leukemic cells were examined by immunoblotting to assess possible correlations with response. RESULTS: Fifty-one patients received a total of 69 courses of therapy. Dose-limiting toxicity consisted of grade 4/5 typhlitis and grade 3/4 mucositis after one course of therapy or grade 4 neutropenia and thrombocytopenia lasting >50 days when a second course was administered on day 21. Among 45 evaluable patients, there were 7 complete remissions, 2 partial remissions, 1 incomplete complete remission, and 1 reversion to chronic-phase chronic myelogenous leukemia. Topotecan steady-state plasma concentrations increased with dose. No accumulation of topotecan or ultrafilterable platinum occurred between days 1 and 5 of therapy. Leukemic cell levels of topoisomerase I, checkpoint kinase 1, checkpoint kinase 2, and Mcl-1 correlated with proliferating cell nuclear antigen but not with response. In contrast, low Bcl-2 expression correlated with response (P = 0.014, Mann-Whitney U test). CONCLUSIONS: The maximum tolerated dose was 1.6 mg/m(2)/d topotecan plus 150 mg/m(2)/d carboplatin. The complete remission rate in a heavily pretreated population was 16% (33% at the highest three dose levels). Responses seem to correlate with low pretreatment blast cell Bcl-2 expression.  相似文献   
138.
139.
Cellulose-based composites have attracted interest given the shift towards ‘green’ materials, but achieving uniform dispersions of cellulose in polymer matrices and/or enhancement of interfacial interactions between components remains challenging. Herein we report the preparation of polypyrrole/cellulose nanocomposites in [Cu(NH3)4(H2O)2](OH)2 (Schweizer''s reagent/cuoxam)-based reaction media via in situ polymerization. The effect of cellulose template morphology and reaction media on the microstructure, electrical conductivity, and surface wettability was studied. Aqueous reaction media favored the formation of a uniform polypyrrole coating encapsulating the cellulose fibers; concentrated cuoxam solutions promoted inhomogeneity and exhibited a progressive decline in conductivity. The maximum conductivity attained was 3.08 S cm−1 from a bacterial cellulose-templated composite prepared in aqueous reaction media and afforded an approximately threefold increase in conductivity when compared with pure PPy at 1.14 S cm−1. Generally, the composites resembled wetting surfaces – with highly concentrated cuoxam solutions yielding improved hydrophilicity, while substitution of bacterial cellulose with nanocrystalline cellulose engendered a shift towards hydrophobicity. Most composites displayed a contact angle of less than 90° suggesting PPy/cellulose composites tended towards hydrophilic behavior. This study highlights investigations into the viability of cellulose solvents as a facile means to control the structure and performance of in situ functionalized cellulose nanocomposites.

The in situ polymerization of polypyrrole/cellulose nanocomposites using Schweizer''s reagent is demonstrated and measured against a number of structural, electrical, and colligative properties.  相似文献   
140.
We tested swab specimens from pets in households in Ontario, Canada, with human COVID-19 cases by quantitative PCR for SARS-CoV-2 and surveyed pet owners for risk factors associated with infection and seropositivity. We tested serum samples for spike protein IgG and IgM in household pets and also in animals from shelters and low-cost neuter clinics. Among household pets, 2% (1/49) of swab specimens from dogs and 7.7% (5/65) from cats were PCR positive, but 41% of dog serum samples and 52% of cat serum samples were positive for SARS-CoV-2 IgG or IgM. The likelihood of SARS-CoV-2 seropositivity in pet samples was higher for cats but not dogs that slept on owners’ beds and for dogs and cats that contracted a new illness. Seropositivity in neuter-clinic samples was 16% (35/221); in shelter samples, 9.3% (7/75). Our findings indicate a high likelihood for pets in households of humans with COVID-19 to seroconvert and become ill.  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