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   2394篇
  免费   89篇
  国内免费   11篇
耳鼻咽喉   98篇
儿科学   161篇
妇产科学   119篇
基础医学   198篇
口腔科学   102篇
临床医学   208篇
内科学   474篇
皮肤病学   47篇
神经病学   111篇
特种医学   85篇
外科学   539篇
综合类   29篇
预防医学   58篇
眼科学   37篇
药学   76篇
中国医学   1篇
肿瘤学   151篇
  2024年   1篇
  2023年   17篇
  2022年   27篇
  2021年   49篇
  2020年   27篇
  2019年   51篇
  2018年   63篇
  2017年   60篇
  2016年   70篇
  2015年   84篇
  2014年   98篇
  2013年   148篇
  2012年   195篇
  2011年   177篇
  2010年   110篇
  2009年   84篇
  2008年   158篇
  2007年   192篇
  2006年   170篇
  2005年   193篇
  2004年   159篇
  2003年   115篇
  2002年   95篇
  2001年   29篇
  2000年   34篇
  1999年   23篇
  1998年   10篇
  1997年   10篇
  1996年   11篇
  1995年   2篇
  1994年   6篇
  1993年   6篇
  1992年   1篇
  1991年   6篇
  1990年   3篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1972年   1篇
  1969年   2篇
  1961年   1篇
排序方式: 共有2494条查询结果,搜索用时 31 毫秒
991.
Purpose We compared the effects of different doses of intrathecal sufentanil when administered together with hyperbaric bupivacaine for elective caesarean section. Methods This was a prospective, randomized, double-blind, controlled trial involving 100 pregnant women, American Society of Anesthesiologists (ASA) I-II, who were scheduled for elective caesarean section under spinal anesthesia. The patients were assigned to four groups according to the dose of sufentanil used: no sufentanil (group I; placebo) or 1.5, 2.5, or 5.0 μg sufentanil (groups 2–4, respectively). In every group, the local anesthetic used was hyperbaric bupivacaine 0.5% (12.5 mg), and the total volume of the solution was 3.5 ml. The duration of complete analgesia, maternal side effects, and maternal/fetal outcomes were recorded. The duration of complete analgesia was defined as the time from intrathecal injection to a vernal analogue score (VAS) of more than 0. Results No patient experienced intraoperative pain. The duration of complete analgesia was prolonged in all groups receiving opioids. The duration of the analgesia and the 0- to 6-h intravenous analgesic requirements were similar in the sufentanil groups. Moreover, the sufentanil groups had longer durations of complete analgesia than the placebo group. Pruritus was more frequent in the 2.5- and 5-μg sufentanil groups than in the 1.5-μg sufentanil and placebo groups. There were no differences among the groups in umbilical cord blood gases on in neonatal Apgar scores. Conclusion The addition of sufentanil 1.5 and 2.5 μg to hyperbaric bupivacaine provided adequate anesthesia for caesarean delivery and good postoperative analgesia. In addition, the incidence of pruritus was significantly lower in the 1.5-μg sufentanil group when compared with that in the 2.5- and 5-μg groups.  相似文献   
992.
The aim of this article is to review possible cranio-maxillofacial deformative consequences associated with hypohidrotic ectodermal dysplasia and embryonic malformations, which include dental ageneses, and describe the oral habilitation. Hypohidrotic ectodermal dysplasia patients had a clinical examination and underwent radiographic and Steiner's analyses and a respiratory capability test before assessment and treatment. Fifteen patients (eight males and seven females, aged 5-45 years) had tooth ageneses (from hypodontia to anodontia) associated with cutaneous dyshydrosis and hair and nail dystrophy. Most patients had sparse or absent hair, a short face with an unusual facial concavity, a maxillary retrusion and a relative mandibular protrusion. Dentists must conduct a comprehensive and multidisciplinary approach to these patients in order to improve their dental, masticatory, growth and orthognathic conditions.  相似文献   
993.
BACKGROUND/AIM: Pterygium is a relatively frequent ocular surface disease with an unexplained etiopathogenesis. Our study was carried out with the aim to identify the presence of inflammatory cells and mediators such as T-lymphocyte subgroups (CD4 and CD8), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and human leukocyte antigen-DR (HLA-DR) in pterygium tissue. METHODS: Pterygium tissue, obtained from 24 patients, and normal conjunctival tissue, from the nasal bulbar conjunctiva obtained from 14 patients operated for ocular perforations or vitrectomy, were separated into epithelial and stromal components under the microscope and suspended with phosphate-buffered saline solution to form a suspension. Cell suspensions were treated with specific antibodies for ICAM-1, VCAM-1, and HLA-DR and T-lymphocyte subgroups and evaluated with flow cytometry. The obtained data were compared statistically. RESULTS: When compared to the control tissue samples, higher rates of ICAM-1-positive cells, VCAM-1-positive cells and HLA-DR-positive cells were recorded in pterygium tissue samples. CD4 and CD8 lymphocytes were also found to be at higher levels when compared to the control group. There was a statistically significant difference between the two groups. CONCLUSION: When compared with normal conjunctival tissue, pterygium tissue had increased levels of T-lymphocyte infiltration and inflammatory markers demonstrating the possible contribution of cellular immunity to the pathogenesis.  相似文献   
994.
Squamous cell carcinoma of the hypopharynx is extremely rare in children. We present a 13-year-old girl with squamous cell carcinoma of the hypopharynx whose father was a coal-miner and a heavy smoker.  相似文献   
995.
We report a brother and a sister with Vogt-Koyanagi-Harada syndrome. The girl had all the manifestations of this condition; her brother was less severely affected. Both showed mental and growth retardation. The literature on this syndrome is reviewed.  相似文献   
996.
Modified methylotrophic yeast Hansenula polymorpha (HP A16) was used in this study, which was obtained with recrossing a leucine oxotrophic yeast and a wild type Hansenula polymorpha CB4732 and was discovered by Ogata et al. The yeast is grown with methanol as a sole carbon source in which methanol oxidase (MOX) is a key enzyme of methanol metabolism. Because of its stability and low substrate specificity, alcohol oxidase is of considerable interest for a range of biotechnological processes. Various methanol feeding regimes were evaluated in an effort to increase the biomass concentration and productivity that could be achieved from fermentations using the other Hansenula polymorpha species. This yeast was grown by batch fermentation. The effects of conditions of inoculation media for increasing amount of MOX enzyme in peroksizomes of yeast with MOX activity were observed. The highest MOX activity of yeast was found within optic density of grown media of OD600 1.5, at 0.35 microM of methanol as used an oxotrophic substrate, at 35 degrees C temperature, at pH 7.0 of 0.1 M potassium phosphate buffer (KPB), at 40 microL of buffered yeast cell volume and at the incubation time of 50 minutes. Whole yeast cells were cultivated at above optimized incubation conditions. The cells were immobilized within the polyacyrlamide gels by entrapment method. Free whole cells and immobilized whole cells were compared using bioconversion percentages of methanol to formaldehyde.  相似文献   
997.
OBJECTIVES: As acylation stimulating protein (ASP) acts on adipocytes mainly as a paracrine factor to increase triglyceride synthesis and storage; hypothetically, it may play a similar role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). METHODS: Forty-six male patients with NAFLD (group A), age-matched 30 male patients with chronic viral hepatitis (group B) and 30 age-matched and body mass index (BMI)-matched healthy male subjects were enrolled in the study. RESULTS: Among the NAFLD patients, 10 patients (24.4%) had simple steatosis and 36 patients (69.6%) had nonalcoholic steatohepatitis (NASH). The mean levels of ASP, complement 3, insulin, C-peptide, HOMA-IR, triglyceride, and very low-density lipoprotein (VLDL) were significantly higher in group A patients than both controls and group B. ASP levels correlated significantly in a positive manner with BMI, insulin, and HOMA-IR. CONCLUSIONS: Dysregulation of the ASP pathway may have important metabolic consequences in NASH and is associated with insulin resistance.  相似文献   
998.
BACKGROUND: Metastasis of extragenital neoplasms to an endometrial polyp is rare and until now, only 6 cases of such involvement has been described. CASE: A 58-year-old woman, who had been diagnosed 4 years ago with infiltrating ductal breast carcinoma and treated with surgery and tamoxifen therapy, was admitted to the gynecology clinic because of endometrial thickening observed during a routine abdominal ultrasonographic examination. A total hysterectomy with bilateral salpingo-oophorectomy was performed. Pathological examination of the specimen showed a large polyp which microscopically showed clusters of cells with signet ring morphology within the polyp stroma. The positivity of tumor cells for GCDFP-15 supported the diagnosis of metastatic breast carcinoma to endometrial polyp. CONCLUSION: Metastatic breast carcinoma should be considered in the differential diagnosis of carcinomas with signet ring cell morphology involving uterus.  相似文献   
999.
Changes in serum ovarian hormone and gonadotrophine levels and ovarian artery blood flow rate by Doppler ultrasonography following laparoscopic tubal sterilization were evaluated. Forty-seven cases of laparoscopic tubal sterilization by electrocoagulation were included in the study. Forty-two women who used nonhormonal contraceptive methods were randomized as a control group. Serum concentrations of estradiol, FSH, LH, progesterone and bilateral ovarian artery pulsatility indexes were measured at baseline and at three, six and 12 months. In the study group, the mean value of midluteal progesterone was significantly decreased three months postoperatively 3. and bilateral ovarian artery pulsatility indexes were increased three and six months postoperatively, compared to their preoperative values. However, there was no statistical difference between bilateral ovarian PI values calculated preoperatively and at 12 months. Laparoscopic tubal ligation by electrocoagulation may temporarily cause reduced bilateral ovarian artery flow and corpus luteum dysfunction proven by low mid-luteal progesterone levels.  相似文献   
1000.
Ependymal tumors in childhood   总被引:1,自引:0,他引:1  
BACKGROUND: Ependymal tumors are classified as ependymoma (benign or low grade) versus anaplastic ependymoma (malignant or high grade). Ependymomas represent 5-10% of intracranial neoplasm in children. In this study, demographic data and the treatment results of pediatric patients with ependymal tumors, treated in a single institute, is reported. PATIENTS AND METHODS: Between 1989 and 2001, 40 (22 M/18 F) previously untreated patients with a median age of 5.5 years (3 months-15 years), of histologically proven ependymal tumors (except ependymoblastomas) were referred to the Institute of Oncology, University of Istanbul. The localization was supratentorial in 18, infratentorial in 20, both supra and infratentorial in two patients. Histologic subgroups were 18 ependymomas (43.6%), and 22 anaplastic ependymomas (56.4%). Total tumor resection was performed in 20 patients (50%), subtotal in 18 patients (45%), and biopsy only in 2 patients (5%). Postoperative treatment consisted of regional (8 patients) or craniospinal (CSI) (9 patients) radiotherapy (RT) in patients with ependymoma; regional (7 patients) or CSI RT (14 patients) with chemotherapy (ChT) in patients with anaplastic ependymoma; ChT only (1 patient) in patients less than 3 years of age. The standard technique for posterior fossa irradiation was parallel-opposed lateral fields and total dose was 45-54 Gy. Between September 1989 and May 1991 patients received regimen A, which consisted of RT followed by eight-in-one ChT, given every 4 weeks for eight courses. Patients who were treated between June 1991 and July 1994, received regimen B, which included two courses of postoperative "VEC" (vincristine, etoposide, cisplatin) ChT, administered every 3 weeks, followed by RT applied with low dose concomitant cisplatin used as a radiosensitizer. Patients with objective response to postoperative "VEC" continued to have "VEC" after completion of RT for six more courses. From August 1994 on, patients received regimen C, consisting of RT and concomitant infusion of cisplatin followed by "VCPCU" (vincristine, cyclophosphamide, procarbazine, lomustine) administered every 4 weeks for eight courses. RESULTS: A total of 40 patients were included in the outcome and survival data. The 5-year overall survival (OS) rate was 64.9%, and the 5-year progression-free survival rate was 50.8% for the whole series. Median time for progression or relapse was 24.3 months and there were 19 patients (43.6%) with relapse or progression. Non-metastatic patients (P = 0.0008, 5-year OS rate was 82% vs. 29%), and totally resected patients (P = 0.01, 5-year OS rate was 80% vs. 55%), and > or =3 years of age (P = 0.04, 5-year OS rate was 75% vs. 38%) had significantly better outcome. CONCLUSIONS: The majority of complete responders were patients who had total tumor removal. Treatment failure occurred mainly within the first 2 years, and outcome was dismal for patients who relapsed or had progressive disease. The median age at diagnosis is 6 years in our patient group; younger children (less than 3 years old) have less favorable outcome. There was no significant difference in survival or progression-free survival between the two histologic subtypes.  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