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   5872篇
  免费   389篇
  国内免费   54篇
耳鼻咽喉   31篇
儿科学   186篇
妇产科学   124篇
基础医学   864篇
口腔科学   257篇
临床医学   437篇
内科学   1578篇
皮肤病学   129篇
神经病学   594篇
特种医学   154篇
外科学   499篇
综合类   8篇
一般理论   1篇
预防医学   277篇
眼科学   27篇
药学   368篇
中国医学   5篇
肿瘤学   776篇
  2024年   8篇
  2023年   52篇
  2022年   57篇
  2021年   183篇
  2020年   120篇
  2019年   142篇
  2018年   164篇
  2017年   114篇
  2016年   148篇
  2015年   173篇
  2014年   254篇
  2013年   310篇
  2012年   484篇
  2011年   453篇
  2010年   271篇
  2009年   224篇
  2008年   418篇
  2007年   410篇
  2006年   389篇
  2005年   381篇
  2004年   317篇
  2003年   313篇
  2002年   320篇
  2001年   47篇
  2000年   34篇
  1999年   37篇
  1998年   53篇
  1997年   52篇
  1996年   32篇
  1995年   41篇
  1994年   31篇
  1993年   16篇
  1992年   30篇
  1991年   32篇
  1990年   27篇
  1989年   20篇
  1988年   19篇
  1987年   5篇
  1986年   22篇
  1985年   14篇
  1984年   17篇
  1983年   14篇
  1982年   13篇
  1981年   15篇
  1980年   6篇
  1979年   4篇
  1978年   3篇
  1977年   4篇
  1976年   5篇
  1974年   3篇
排序方式: 共有6315条查询结果,搜索用时 15 毫秒
51.
52.
Background: Coronavirus disease 2019 (COVID-19) causes not only severe illness but also detrimental effects associated with the lockdown measures. The present study aimed to evaluate reported lifestyle changes in a cohort of adults in Italy, including physical exercise, food choices, and psychological wellbeing, after two months of lockdown. Methods: A web survey on social media (Facebook and LinkedIn) of 32 multiple-choice questions aiming to evaluate the impact of the national COVID-19 lockdown in a sample of Italian adults. Results: We received 1378 complete responses (women 68.3%, mean age 39.5 ± 12.5 years). The percentage of participants reporting regular exercise decreased during lockdown (52 vs. 56.5%). The vast majority of people continued to consume the three traditional meals per day, but the consumption of meat, fish, and eggs significantly decreased. Women reported more frequent anxiety, sadness, fear, and feelings of insecurity than men. The factors predicting the worst outcome during the lockdown were being a woman, low education and income, gastrointestinal diseases. Conclusion: The lockdown has had a limited impact on food choices and physical exercise in Italian adults of our series, since most of them made an effort to improve their lifestyle. However, women with gastrointestinal diseases reported more frequent negative feelings and poor adaptation to the lockdown.  相似文献   
53.
Individual differences in the chronotype, an attitude that best expresses the individual circadian preference in behavioral and biological rhythms, have been associated with cardiometabolic risk and gut dysbiosis. Up to now, there are no studies evaluating the association between chronotypes and circulating TMAO concentrations, a predictor of cardiometabolic risk and a useful marker of gut dysbiosis. In this study population (147 females and 100 males), subjects with the morning chronotype had the lowest BMI and waist circumference (p < 0.001), and a better metabolic profile compared to the other chronotypes. In addition, the morning chronotype had the highest adherence to the Mediterranean diet (p < 0.001) and the lowest circulating TMAO concentrations (p < 0.001). After adjusting for BMI and adherence to the Mediterranean diet, the correlation between circulating TMAO concentrations and chronotype score was still kept (r = −0.627, p < 0.001). Using a linear regression analysis, higher chronotype scores were mostly associated with lower circulating TMAO concentrations (β = −0.479, t = −12.08, and p < 0.001). Using a restricted cubic spline analysis, we found that a chronotype score ≥59 (p < 0.001, R2 = −0.824) demonstrated a more significant inverse linear relationship with circulating TMAO concentrations compared with knots <59 (neither chronotype) and <41 (evening chronotype). The current study reported the first evidence that higher circulating TMAO concentrations were associated with the evening chronotype that, in turn, is usually linked to an unhealthy lifestyle mostly characterized by low adherence to the MD.  相似文献   
54.
55.
Background: Conflicting data have been reported about the associationbetween glutathione S-transferase (GST), a family of proteins implicated indetoxification of cytotoxic drugs in human ovarian in vitro models, andresponse to chemotherapy and prognosis in ovarian cancer patients. The aim ofthis study was to analyze the possible clinical role of GST activity in alarge series of primary ovarian cancer patients.Patients and methods: The study included a large series of primaryuntreated ovarian cancer patients who underwent cytoreductive surgery andchemotherapy and who were followed up in a single institution. GST activitylevels were assessed in tumor extracts by using a biochemical assay. A cut-offof 250 units of enzymatic activity was chosen according to the receiveroperating characteristics (ROC) curve.Results: GST activity levels were distributed in an asymmetrical manner(median: 266 units; range: 4–918 units) and did not seem to beassociated with stage, histopathological grading, ascites, or residual tumorafter surgery. Higher GST activity levels were found in patients who respondedto chemotherapy (median: 298 units, range: 50–691) than in those whoresponded only partially (median: 227 units, range: 19–747) or not atall to chemotherapy (median: 246 units, range: 4–811) (H = 7.02, P =0.029). Moreover, the percentage of cases with >250 units was significantlyhigher among complete responders (66%) than partial responders(37%) or non-responders (48%) (2 = 7.32;P = 0.025). When multivariate analysis, including clinico-pathologicalparameters and GST activity status as predictors of response to chemotherapy,was carried out, residual tumor, stage and GST status retained independentpredictive value. Patients with high GST activity had more favourableprognosis than those with low GST activity. The median PFS was 42 months forpatients with high GST activity compared to 17 months for those with low GSTactivity (P = 0.037). The median overall survival was 72 months forhigh-GST-activity and42 months for low-GST-activity patients (P = 0.043). Substantially similarresults were obtained in the subgroup of stage II–III–IV ovariancancer patients. Multivariate analysis including the clinico-pathologicalparameters and GST activity status was performed in stage III–IV ovariancancer patients: Stage IV disease, residual tumor >2 cm, the presence ofascites and low GST activity status retained independent negative prognosticroles.Conclusion: A direct association between high GST activity and a betterclinical outcome in terms of response to chemotherapy and survival has beenobserved in a large series of primary untreated ovarian cancer patients. Theseresults, which are contrary to the expectations raised by in vitro studies,emphasize the need for caution when translating in vitro-generated hypothesesto the clinical setting.  相似文献   
56.
The effect of early splenectomy and of polychemotherapy with hydroxyurea, busulfan, and alternate bimonthly courses of arabinosyl cytosine and vincristine plus prednisone, was evaluated in 139 previously untreated patients with chronic myeloid leukemia (CML), consecutively admitted to 18 hospitals from March 1973 to October 1974. Fifty-six patients were splenectomized and 83 patients were not splenectomized. Splenectomy did not influence the duration of chronic and blastic phase, and did not prolong survival. The prognosis of high risk patients was not improved. During the chronic phase, high platelet counts were more frequent in splenectomy group, and five patients developed thrombotic or thromboembolic complications, 5 to 19 months after the operation. The median survival of the whole group was 50 months, with 32 of 139 patients (actuarial proportion 30%) remaining alive 72 months after diagnosis, but the slope of the survival curve was similar to that of historical controls. The results of this trial suggests that new strategies should be developed for the therapy of CML.  相似文献   
57.
We measured, by immunohistochemistry, HMGA1 protein expression in 212 breast tissue specimens: 6 normal samples, 28 hyperplastic lesions (13 with cellular atypia), 11 fibroadenomas, 10 in situ ductal carcinomas, 144 ductal carcinomas, and 13 lobular carcinomas. HMGA1 was not expressed in normal breast tissue; HMGA1 staining was intense in 40% of hyperplastic lesions with cellular atypia and in 60% of ductal carcinomas and weak in fibroadenomas and in hyperplastic lesions without cellular atypia. Because HMGA1 expression was similar among ductal breast carcinomas with different histologic grading, we evaluated the association between HMGA1 expression and that of other markers of breast carcinoma invasion (estrogen and progesterone receptors, Ki-67 antigen, and ErbB2) in 21 cases of grade 3 breast ductal carcinomas and 7 cases of breast lobular carcinomas. We found that HMGA1 expression tended to be associated only with c-erbB-2 expression (Spearman rho: 0.36; P=0.065). Taken together, these results suggest that HMGA1 expression might be a novel indicator for the diagnosis and prognosis of human breast cancer.  相似文献   
58.
PURPOSE: To evaluate clinical and lung dose-volume histogram based factors as predictors of radiation pneumonitis (RP) in lung cancer patients (PTs) treated with thoracic irradiation. METHODS AND MATERIALS: Records of all lung cancer PTs irradiated at our Institution between 1994 and 2000 were retrospectively reviewed. Eighty-four PTs with small or non-small-cell lung cancer, irradiated at >40 Gy, with full 3D dosimetry data and a follow-up time of >6 months from start of treatment, were analysed for RP. Pneumonitis was scored on the basis of SWOG toxicity criteria and was considered a complication when grade> or =II. The following clinical parameters were considered: gender, age, surgery, chemotherapy agents, presence of chronic obstructive pulmonary disease (COPD), performance status. Dosimetric factors including prescribed dose (Diso), presence of final conformal boost, mean lung dose (Dmean), % of lung receiving > or =20, 25, 30, 35, 40, and 45 Gy (respectively V20-->V45), and normal tissue complication probability (NTCP) values were analysed. DVHs data and NTCP values were collected for both lungs considered as a paired organ. Median and quartile values were taken as cut-off for statistical analysis. Factors that influenced RP were assessed by univariate (log-rank) and multivariate analyses (Cox hazard model). RESULTS: There were 14 PTs (16.6%) who had > or =grade II pulmonary toxicity. In the entire population, the univariate analysis revealed that many dosimetric parameters (Diso, V20, V30, V40, V45) were significantly associated with RP. No significant correlation was found between the incidence of RP and Dmean or NTCP values. Multivariate analysis revealed that the use of mitomycin (MMC) (P=0.005) and the presence of COPD (P=0.026) were the most important risk factor for RP. In the group without COPD (55 PTs, seven RP) a few dosimetric factors (Dmean, V20, V45) and NTCP values (all models) were associated with RP in the univariate analysis (P< or =0.06). According to the multivariate analysis, the use of MMC was independently associated with RP (P=0.007), while Dmean approached statistical significance (P=0.082). CONCLUSIONS: In this study the use of mitomycin or the presence of COPD is associated with a higher risk of RP. In the entire population NTCP values were not significantly correlated with the incidence of RP. Mean lung dose shows a clear trend toward statistical significance in the patient group without COPD.  相似文献   
59.
There is evidence that food consistency may influence postprandial physiological responses. Recently we found that homogenization of a vegetable-rich meal significantly delayed the gastric emptying rate and was more satiating than the same meal in solid-liquid form. In this present study we investigated whether homogenization also influences endocrine and metabolic responses to the meal. Eight healthy men, aged 21-28 (mean 24.5) years, were given the meal (cooked vegetables 250 g, cheese 35 g, croutons 50 g and olive oil 25 g, with water 300 ml; total energy 2.6 MJ) in both solid-liquid (SM) and homogenized (HM) form, in random order, at 1-week intervals. Variables assayed were plasma glucose, insulin and glucose-dependent insulinotropic peptide (GIP) levels for 2 h and diet-induced thermogenesis (DIT) for 5 h. Plasma glucose pattern was similar after both meals. However, HM induced significantly greater insulin, GIP and DIT responses than SM. Mean integrated areas under the curves (AUC) were 1.7 (SEM 0.38) v. 1.2 (SEM 0.33) U/l per 120 min (P = 0.005) for insulin, 19.9 (SEM 2.44) v. 16 (SEM 1.92) nmol/l per 120 min (P = 0.042) for GIP, and 237.7 (SEM 16.32) v. 126.4 (SEM 23.48) kJ/300 min (P = 0.0029) for DIT respectively. Differences between GIP-AUC after HM and SM correlated significantly with differences between insulin-AUC after HM and SM (r2 0.62, P = 0.021). These findings demonstrate that homogenization of a meal results in a coordinated series of changes of physiological gastroentero-pancreatic functions and confirm that the physical state of the meal plays an important role in modulating endocrine and metabolic responses to food.  相似文献   
60.
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   

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