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   10457篇
  免费   497篇
  国内免费   56篇
耳鼻咽喉   115篇
儿科学   182篇
妇产科学   221篇
基础医学   1196篇
口腔科学   258篇
临床医学   787篇
内科学   2849篇
皮肤病学   148篇
神经病学   1173篇
特种医学   298篇
外科学   1335篇
综合类   24篇
一般理论   3篇
预防医学   458篇
眼科学   204篇
药学   733篇
中国医学   14篇
肿瘤学   1012篇
  2024年   9篇
  2023年   65篇
  2022年   150篇
  2021年   270篇
  2020年   165篇
  2019年   213篇
  2018年   246篇
  2017年   214篇
  2016年   242篇
  2015年   267篇
  2014年   358篇
  2013年   530篇
  2012年   772篇
  2011年   787篇
  2010年   423篇
  2009年   416篇
  2008年   725篇
  2007年   767篇
  2006年   753篇
  2005年   711篇
  2004年   699篇
  2003年   617篇
  2002年   559篇
  2001年   80篇
  2000年   61篇
  1999年   56篇
  1998年   110篇
  1997年   76篇
  1996年   78篇
  1995年   76篇
  1994年   74篇
  1993年   64篇
  1992年   45篇
  1991年   34篇
  1990年   38篇
  1989年   30篇
  1988年   22篇
  1987年   23篇
  1986年   21篇
  1985年   20篇
  1984年   19篇
  1983年   18篇
  1982年   17篇
  1981年   24篇
  1980年   11篇
  1979年   7篇
  1978年   8篇
  1977年   5篇
  1972年   5篇
  1966年   4篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
91.
Few epidemiologic studies have investigated the potential relation between flavonoids and breast cancer risk. We have applied recently published data on the composition of foods and beverages in terms of six principal classes of flavonoids (i.e., flavanones, flavan-3-ols, flavonols, flavones, anthocyanidines, and isoflavones) on dietary information collected in a large-case control study of breast cancer conducted in Italy between 1991 and 1994. The study included 2,569 women with incident, histologically confirmed breast cancer, and 2,588 hospital controls. Odds ratios (OR) and 95% confidence intervals were estimated by multiple logistic regression models. After allowance for major confounding factors and energy intake, a reduced risk of breast cancer was found for increasing intake of flavones (OR, 0.81, for the highest versus the lowest quintile; P-trend, 0.02), and flavonols (OR, 0.80; P-trend, 0.06). No significant association was found for other flavonoids, including flavanones (OR, 0.95), flavan-3-ols (OR, 0.86), anthocyanidins (OR, 1.09), as well as for isoflavones (OR, 1.05). The findings of this large study of an inverse association between flavones and breast cancer risk confirm the results of a Greek study.  相似文献   
92.
Dietary folate and risk of prostate cancer in Italy.   总被引:2,自引:0,他引:2  
Folate status may affect cancer risk through its role in both methylation and nucleotide synthesis of DNA. A low dietary intake of folate has been linked to risk of several cancers, but epidemiologic studies with reference to prostate cancer are scanty. We therefore analyzed data from a case-control study of prostate cancer conducted between 1991 and 2002 in various areas of Italy. Cases were 1,294 patients with incident, histologically confirmed prostate cancer and controls were 1,451 patients admitted to the same network of hospitals of cases for acute, nonneoplastic conditions. All subjects were < 75 years old. Intake of folate and other nutrients was computed from a validated food frequency questionnaire. We adjusted for energy intake using the residual method, and calculated multivariate odds ratios (OR) and 95% confidence intervals (CI) using unconditional logistic regression. The OR of prostate cancer was 0.66 (95% CI, 0.51-0.85) for the highest versus the lowest quintile of folate intake. The relation between dietary folate and prostate cancer was consistent across strata of age, methionine, vitamin B6, and alcohol intake, and did not vary substantially according to Gleason score of prostate cancer. The combined OR for high-folate and low-alcohol intake versus low-folate and high-alcohol intake was 0.46 (95% CI, 0.29-0.75). Therefore, this study supports a favorable role of dietary folate on prostate cancer risk.  相似文献   
93.
PURPOSE: Between September 1991 and May 1997, within the International Berlin-Frankfurt-Muenster Study Group (I-BFM-SG), a randomized study was performed aimed at assessing the efficacy of prolonged use of high-dose l-asparaginase (HD-l-ASP) during continuation therapy in children with standard risk (SR) acute lymphoblastic leukemia (ALL), treated with a reduced BFM-type chemotherapy. PATIENTS AND METHODS: The Italian, Dutch, and Hungarian groups participated in this study denominated IDH-ALL-91, and 494 children were enrolled. Treatment consisted of a BFM-type modified backbone with omission of the IB part in induction and elimination of two doses of anthracyclines during reinduction in both arms at the beginning of continuation therapy. Patients were randomly assigned to receive (YES-ASP) or not (NO-ASP) 20 weekly HD-l-ASP (25,000 IU/m2). RESULTS: The event-free-survival and overall survival probabilities at 10 years for the entire group were 82.5% (1.8) and 90.3% (1.3), respectively. Of the 490 patients eligible for random assignment, 355 (72.4%) were randomly assigned (178 YES-ASP and 177 NO-ASP). After a median follow-up of 9 years, the probability of disease-free survival at 10 years was 87.5% (SE, 2.5) for YES-ASP arm versus 78.7% (SE, 3.3) for NO-ASP arm (P = .03). In multivariate analysis, NO-ASP arm (P = .03), male sex (P = .004), and age older than 10 years (P = .0003) had a significantly adverse impact on outcome. CONCLUSION: In this subset of patients, selected with criteria not including monitoring of minimal residual disease, application of extended HD-l-ASP may improve prognosis, compensating reduced leukemia control that results from adoption of a reduced-intensity BFM-backbone for treatment of children with SR ALL.  相似文献   
94.

Purpose

The role of various foods and nutrients, and their combinations, on prostate cancer risk remains largely undefined. We addressed therefore the issue of complex dietary patterns.

Methods

We analyzed data from an Italian case–control study, including 1,294 men with prostate cancer and 1,451 hospital controls. We carried out an exploratory principal component factor analysis on 28 selected nutrients in order to identify dietary patterns. We estimated odds ratios (ORs) and corresponding confidence intervals (CIs) using logistic regression models on quintiles of factor scores, adjusting for major confounding variables.

Results

We identified five dietary patterns, labeled “Animal Products,” “Vitamins and Fiber,” “Starch-rich,” “Vegetable Unsaturated Fatty Acids (VUFA),” and “Animal Unsaturated Fatty Acids (AUFA).” We found positive associations between prostate cancer and “Animal Products” (OR for the highest vs. the lowest score quintile: 1.51, 95 % CI 1.16–1.96), “Starch-rich” (OR 1.50, 95 % CI 1.16 1.93), and “AUFA” (OR 1.32, 95 % CI 1.02–1.70) patterns. No significant associations emerged with “Vitamins and Fiber” (OR 0.93) and “VUFA” (OR 1.16) patterns.

Conclusions

Our findings suggest that a diet rich in animal products, including several types of meat and dairy products, as well as of (refined) cereals and sugars has an unfavorable role on prostate cancer.  相似文献   
95.
Purpose: To evaluate whether or not an intermediate dose of preoperative external radiation therapy intensified by systemic chemotherapy could improve the tumor response, sphincter preservation, and tumor control.

Methods and Materials: Between March 1990 and December 1995, 83 consecutive patients with resectable extraperitoneal adenocarcinoma of the rectum were treated with preoperative chemoradiation: bolus i.v. mitomycin C (MMC), 10 mg/m2, Day 1 plus 24-h continuous infusion i.v. 5-fluorouracil (5FU) 1000 mg/m2, Days 1–4, and concurrent external beam radiotherapy (37.8 Gy). All but 2 patients had T3 disease. Surgery was performed 4–6 weeks after the end of chemoradiation.

Results: Total Grade 3–4 acute toxicity during chemoradiation was observed in 11 (13%) patients: hematological Grade 3 toxicity was recorded in 8 (10%) patients, and Grade 4 toxicity was recorded in 2 (2%) patients. Grade 3 diarrhea was seen in 2 (2%) patients. No patient had major skin or urological acute toxicity. Two patients had no surgery: 1 died before surgery from septic complications after Grade 4 hematological toxicity; 1 refused surgery and is still alive after 6 years. There was no postoperative mortality and the overall perioperative morbidity rate was 25%. The analysis of tumor response involved 81 patients. Overall, 9% [7] of 81 patients had a complete pathologic response. Comparing the stage at the diagnostic workup with the pathologic stage, tumor downstaging was observed in 46 (57%) patients. We had 7 (9%) pT0, 5 (6%) pT1, 33 (41%) pT2, and 36 (44%) pT3. Nodal status downstaging was detected in 46 patients (57%). No evidence of nodal involvement was observed in 59 patients (73%). The incidence of tumor response was affected significantly by the number of quarters of rectal circumference involved (p = 0.03) and, marginally, by the length of the tumor (p = 0.09). The distance between the lower pole of the tumor and the anorectal ring had no influence. Of the patients, 63 (78%) had a sphincter-saving surgical procedure. In 12 (44%) of 27 patients candidate for an APR, the sphincter was preserved, as it was in 19 (95%) of 20 probable candidates. Lengthening of the distance between the anorectal ring and the lower pole of the tumor > 20 mm was observed in 21 patients (26%). Of 63 patients, 4 (6%) had moderate soilage after the sphincter-saving procedure.

Conclusion: Preoperative combined modality therapy seems to afford some potential advantages in nonrandomized trials: patients are able to tolerate higher chemotherapy doses and they experience a lower acute toxicity. Tumor downstaging and resectability rates are high; sphincter preservation is feasible. Larger T3 tumors remained less influenced by this treatment; thus, taking into account the low toxicity rate recorded, a more aggressive schedule should be applied in these resectable tumors.  相似文献   

96.
Due to climate change and population expansion, concrete structures are progressively being subjected to more extreme environments. As the environment affects plastic shrinkage directly, there is a need to understand the effect of environmental changes on plastic shrinkage cracking. This paper examines the plastic shrinkage crack development parametrically at low, mid, and high drying environmental conditions, corresponding to different environments in three Saudi cities. The effects of water-cement ratios and quantities of recycled tire steel fibers (RTSF) in concrete are also investigated. The different environmental conditions for the plastic shrinkage tests were simulated in a specially designed chamber as per ASTM C1579, 2006. A digital image processing (DIP) technique was used to monitor crack initiation and development. Through the use of the crack reduction ratio (CRR), it was found that 30 kg/m3 of RTSF can control plastic shrinkage cracks at low and mid conditions. For the more extreme (high) conditions, the use of 40 kg/m3 of RTSF fiber was sufficient to completely eliminate surface plastic shrinkage cracks. This work can help develop more sustainable concrete structures in a wider set of environmental conditions and help mitigate the impact of climate change on concrete infrastructure.  相似文献   
97.
Background: During the COVID-19 pandemic, the risk of SARS-CoV-2 infection, the public health measures of social distancing, the freedom limitations, quarantine, and the enforced homeworking under the lockdown period, as well as medical causes including COVID-19 infection per se, may have caused major emotional distress, especially in the most vulnerable patients. We aimed to evaluate the variations in the number of admissions due to Takotsubo syndrome (TTS) during the COVID-19 pandemic in the Veneto region. Methods: We retrospectively reviewed and analyzed the number of admissions because of TTS in 13 Divisions of Cardiology located in the Veneto region, the northeastern area of Italy, covering a population of more than 2.5 million inhabitants, during the two major pandemic waves of COVID-19 (the first between 15 March and 30 April 2020 and the second between 15 November and 30 December 2020) that occurred in 2020. Results: In total, 807 acute coronary syndromes were admitted in the 13 enrolling hospitals. Among these, 3.9% had TTS. Compared to the corresponding 2018 and 2019 time periods, we observed a significant increase in the number of TTS cases (+15.6%, p = 0.03 and +12.5%, p = 0.04, comparing 2018 to 2020 and 2019 to 2020, respectively). Geographical distribution of the TTS cases reflected the broad spread of the SARS-CoV-2 infection with a significant direct relationship between TTS incidence and the number of COVID-19 infections according to Pearson’s correlation (r = 0.798, p < 0.001). Conclusions: The higher incidence of TTS during the 2020 COVID-19 pandemic waves, especially in the areas that were hit hardest in terms of morbidity and mortality by the SARS-CoV-2 infection, suggest a strong direct and/or indirect role of COVID-19 in the pathogenesis of TTS.  相似文献   
98.
The effects of different cholecalciferol supplementation regimens on serum inflammatory cytokines in healthy subjects with vitamin D deficiency are still lacking. This is a single-center, open-label, randomized, parallel group study involving healthy subjects deficient in vitamin D (baseline 25OHD < 20 ng/mL) receiving oral cholecalciferol with three different dosing regimens: Group A: 10,000 IU/day for 8 weeks followed by 1000 IU/day for 4 weeks; Group B: 50,000 IU/week for 12 weeks and Group C: 100,000 IU every other week for 12 weeks. IL-17A, IL-6, IL-8, IL-10, IL-23 and TNFα were measured at baseline and at week 4, 8, 12, and 16. 75 healthy subjects were enrolled (58.7% female), with an average age of 34.1 ± 10.2 years. No statistical differences were observed among groups at baseline for either IL-6, IL-17A, IL-23, IL-8 or IL-10 at any time point; TNFα was indetectable. Concerning the whole sample, the time trend analysis showed a statistically significant linear trend for decreasing values over the treatment period for IL-6 (p = 0.016) and IL-17A (p = 0.006), while no significant time trends were observed for the other teste cytokines. No significant differences were found in the serum concentrations of the tested cytokines between week 12 and week 16. In young healthy individuals deficient in vitamin D, cholecalciferol administration showed a decrease in the serum IL-6 and IL-17A concentrations, without marked differences using the three regimens.  相似文献   
99.
BackgroundThe itAlian pRospective Study on CANGrELOr (ARCANGELO) was aimed to assess the safety of using cangrelor during percutaneous coronary intervention (PCI) in patients with acute coronary syndromes (ACS) in the daily practice.HypothesisThe safety of cangrelor after the transition to oral P2Y12 inhibitors was evaluated as the incidence of bleeding outcomes in the 30 days following PCI according to postauthorization safety study guidelines.MethodsAdults with ACS who were treated with cangrelor in one of the 28 centers involved in the study. Patients who consented to participate were followed in the 30 days following their PCI. Bleedings (Bleeding Academic Research Consortium [BARC] classification), major adverse cardiac events (MACEs), and adverse events were recorded. The interim results at two‐thirds of the enrollment period are presented.ResultsA total of 17 bleedings were observed in the 320 patients who completed the study at this stage. All bleedings were classified as BARC Type 1–2, except for one case of Type 3a (vessel puncture site hematoma). Four patients experienced MACEs (2 acute myocardial infarctions, 1 sudden cardiac death, 1 noncardiovascular death due to respiratory distress, and multiorgan failure). None of the bleedings was rated as related to cangrelor.ConclusionsThe interim results of the ARCANGELO study provide a preliminary confirmation that the use of cangrelor on patients with ACS undergoing PCI is not associated with severe bleedings.  相似文献   
100.
Collision metastasis is a rare phenomenon of concomitant localization of 2 or more different tumors in the same lymph node. In most cases, primary malignancies are synchronous carcinomas arising in the same organ or area of the body. A 82-year-old man presented with hematuria and acute renal failure; he had undergone dermatological consultation ten months ago because of a large deep brown skin lesion in his dorso-lumbar region, which was not excised upon patient’s request. He underwent radical cystectomy with extended pelvic lymphadenectomy due to nonpapillary high-grade urothelial carcinoma, with focal squamous features, infiltrating the bladder wall and prostate gland. In one left iliac lymph node, small foci of metastatic urothelial carcinoma (positive for P63 and CK34betaE12) were close to melanoma cells (positive for HMB45). The patient refused further treatment and died of metastatic disease 12 months after cystectomy. There is no specific clinical feature for nodal collision metastasis. A polymorphic histologic appearance poses the suspect, but immunohistochemical stains are needed to define the primary tumors. Collision metastases are thought to carry a poor prognosis. Their clinical relevance is linked to the fact that the patient faces 2 different metastatic tumors that may require specific multidisciplinary approach once diagnosed as metastatic. We present, to the best of our knowledge, the first case of collision nodal metastasis from bladder cancer and melanoma, and describe its clinical and histopathological characteristics to raise awareness on this rare occurrence, which portends a poorer prognosis than each single tumor.  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