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   4041篇
  免费   154篇
  国内免费   34篇
耳鼻咽喉   70篇
儿科学   100篇
妇产科学   38篇
基础医学   446篇
口腔科学   44篇
临床医学   277篇
内科学   1028篇
皮肤病学   34篇
神经病学   206篇
特种医学   319篇
外科学   681篇
综合类   19篇
预防医学   177篇
眼科学   89篇
药学   280篇
中国医学   5篇
肿瘤学   416篇
  2022年   44篇
  2021年   75篇
  2020年   19篇
  2019年   39篇
  2018年   51篇
  2017年   44篇
  2016年   44篇
  2015年   55篇
  2014年   79篇
  2013年   100篇
  2012年   148篇
  2011年   171篇
  2010年   104篇
  2009年   93篇
  2008年   163篇
  2007年   206篇
  2006年   149篇
  2005年   184篇
  2004年   129篇
  2003年   148篇
  2002年   166篇
  2001年   180篇
  2000年   180篇
  1999年   134篇
  1998年   67篇
  1997年   90篇
  1996年   58篇
  1995年   49篇
  1994年   40篇
  1993年   33篇
  1992年   105篇
  1991年   89篇
  1990年   92篇
  1989年   112篇
  1988年   116篇
  1987年   81篇
  1986年   86篇
  1985年   95篇
  1984年   60篇
  1983年   53篇
  1982年   32篇
  1981年   20篇
  1980年   24篇
  1979年   35篇
  1978年   17篇
  1977年   19篇
  1976年   24篇
  1975年   23篇
  1973年   13篇
  1968年   13篇
排序方式: 共有4229条查询结果,搜索用时 0 毫秒
81.
Objectives. Twin to twin transfusion syndrome (TTTS) is one of the most important problems for perinatal management of monochorionic twins. Since TTTS is deeply related to the prognoses of both fetuses, fetal circulation and placental blood flow of monochorionic twins were studied with the purpose of clarifying characteristic features.

Methods. The patterns and numbers of vascular anastomoses were checked on the placental surface, arterio-arterial (A-A) anastomosed vessels by ultrasound, and circulatory changes were studied with relation to uterine contraction.

Results. The high risk of monochorionic twin pregnancies was largely related to the patterns of vascular anatomy of the placenta and numbers of anastomosed vessels. The first placental vascular connection detected in vivo was the A-A anastomosis characterized by the bidirectional flow waveform in pulsed Doppler velocimetry.

Conclusion. TTTS is related to anastomosed vessels on the surface of placenta. To manage and prevent TTTS, fetal circulation and placental blood flow should be carefully observed.  相似文献   
82.
Long-term results of bilateral internal thoracic artery grafting   总被引:3,自引:0,他引:3  
Background. Little is known about the long-term results of the uniform group of patients who had bilateral internal thoracic artery (ITA) grafting with the method of left ITA-to-left anterior descending coronary artery and right ITA-to-circumflex artery.

Methods. Late follow-up study was performed in the first consecutive 203 patients (mean age, 62.6 ± 9.1 years) who underwent isolated coronary artery bypass grafting with the left ITA anastomosed to the left anterior descending coronary artery and the right ITA to major branches of the circumflex artery. The patients were grouped according to the patency of ITA grafts demonstrated by early postoperative angiography (Both patent (BP) group, 168 patients: both ITAs showed complete patency; Not patent (NP) group, 23 patients: at least one ITA was dysfunctional).

Results. Actuarial 7-year survival in all patients was 89.3% ± 3.1%. The cumulative probability of event-free survival for cardiac death, myocardial infarction, intervention, and angina at 7 years was 96.6% ± 1.8%, 98.0% ± 1.5%, 86.7% ± 3.2%, and 90.7% ± 2.9%, respectively. NP group had more myocardial infarction and angina than the BP group, but was not statistically significant. Because of failed grafts at the early angiography, intervention was performed more frequently in NP group (p < 0.01).

Conclusions. Our results of actuarial 7-year survival and the cumulative probability of event-free survival were at least comparable to the results of other similar studies using bilateral ITA. The freedom from angina appeared to be better than in the previous study. Overall our study supports the continued use of this method of ITA grafting.  相似文献   

83.
OBJECTIVE To investigate the expression of Coxsackie and Adenovirus receptor (CAR) in renal-cell carcinoma and the relationship of the CAR to the biological behavior of the carcinomas.METHODS The immunohistochemical SP method was used to detect the expression of Coxsaekie and Adenovirus receptor in 48 cases of renalcell carcinoma and in 12 cases of normal renal tissue 2 cm away from the tumor tissue.RESULTS The positive rates of CAR were 100% in 12 cases of para-tumcr normal renal tissue and 35.4% in 48 cases of renal-cell carcinoma respectively. The difference of CAR expression between them was significant (P<0.05). The grades of the tumor were as follows: 22 in Grade Ⅰ, 17in Grade Ⅱ and 9 in Grade Ⅲ with the CAR positive rate being 54.5%,23.5% and 11.1%, respectively. There was a negative correlation between CAR expression and tumor grading (P<0.05). In addition, the number of the cases in stages Ⅰ to ⅣV were 19, 13, 11 and 5 respectively, with the respective positive rates being 57.9%, 30.8%, 18.2% and 0.0%, i.e. there also was a negative relationship between CAR expression and the stage (P<0.05).CONCLUSION CAR expression is down-regulated in renal-cell carcinoma compared with normal tissue. The level of CAR may be a sensitive predictor of differentiation, invasion and metastasis. Loss of CAR expression correlates with the invasive phenotype in our analysis of renal-cell carcinoma.  相似文献   
84.
The impact of changes in nutritional status during hospitalization on prognosis in patients with heart failure with preserved ejection fraction (HFpEF) remains unknown. We examined the association between changes in the Geriatric Nutritional Risk Index (GNRI) and prognosis during hospitalization in patients with HFpEF stratified by nutritional status on admission. Nutritional status did and did not worsen in 348 and 349 of 697 patients with high GNRI on admission, and in 142 and 143 of 285 patients with low GNRI on admission, respectively. Kaplan–Meier analysis revealed no difference in risk of the composite endpoint, all-cause death, or heart failure admission between patients with high GNRI on admission whose nutritional status did and did not worsen. In contrast, patients with low GNRI on admission whose nutritional status did not worsen had a significantly lower risk of the composite endpoint and all-cause death than those who did. Multivariable analysis revealed that worsening nutritional status was independently associated with a higher risk of the composite endpoint and all-cause mortality in patients with low GNRI on admission. Changes in nutritional status during hospitalization were thus associated with prognosis in patients with malnutrition on admission, but not in patients without malnutrition among those with HFpEF.  相似文献   
85.
Phospholamban p.Arg14del is reported to cause hereditary cardiomyopathy with malignant ventricular tachycardia (VT) and advanced heart failure. However, the clinical courses of Japanese cardiomyopathy patients with phospholamban p.Arg14del remain uncharacterized. We identified five patients with this variant. All patients were diagnosed with dilated cardiomyopathy (DCM), developed end-stage heart failure and experienced VT requiring implantable cardioverter defibrillator discharge. Four patients survived after implantation of a left ventricular assist device (LVAD), while one patient who refused LVAD implantation died of heart failure. Based on the severe course of the disease, we propose genetic screening for phospholamban p.Arg14del in DCM patients.  相似文献   
86.
Objectives:  To prospectively examine the association of cigarette smoking and alcohol drinking with oral and pharyngeal carcinogenesis, we analyzed data from a nation-wide large-scale cohort study in Japan.
Methods:  A total of 34 136 men and 43 711 women aged 40–79 years were included in the study. The Cox proportional hazard model was used to estimate the relative risk (RR) and 95% confidence interval (95% CI) of oral and pharyngeal cancer for smoking and drinking by sex, while adjusting for age, consumption of green tea, preference for salty foods, and consumption of green yellow vegetables.
Results:  Current smokers were found to have a higher risk of death caused by oral and pharyngeal cancer compared with non-smokers in both sexes: the RR was 2.6 (95% CI: 1.0–6.7) in men and 8.2 (95% CI: 2.1–32.1) in women. Men who drank more than 46 g ethanol per day had an approximately threefold increased risk of oral and pharyngeal cancer. Simultaneous exposure to both factors was significantly associated with an elevated risk of oral and pharyngeal cancer (RR: 3.3, 95% CI: 1.1–9.6).
Conclusions:  The result supports the carcinogenic effect of cigarette smoking and alcohol drinking on the oral cavity and pharynx.  相似文献   
87.
88.
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