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   8455篇
  免费   473篇
  国内免费   133篇
耳鼻咽喉   54篇
儿科学   213篇
妇产科学   650篇
基础医学   967篇
口腔科学   136篇
临床医学   985篇
内科学   1765篇
皮肤病学   92篇
神经病学   533篇
特种医学   327篇
外科学   1089篇
综合类   195篇
预防医学   438篇
眼科学   76篇
药学   625篇
中国医学   116篇
肿瘤学   800篇
  2023年   40篇
  2022年   97篇
  2021年   177篇
  2020年   94篇
  2019年   154篇
  2018年   255篇
  2017年   170篇
  2016年   165篇
  2015年   217篇
  2014年   263篇
  2013年   404篇
  2012年   577篇
  2011年   591篇
  2010年   397篇
  2009年   336篇
  2008年   518篇
  2007年   587篇
  2006年   550篇
  2005年   449篇
  2004年   387篇
  2003年   322篇
  2002年   318篇
  2001年   270篇
  2000年   275篇
  1999年   215篇
  1998年   86篇
  1997年   92篇
  1996年   80篇
  1995年   53篇
  1994年   73篇
  1993年   45篇
  1992年   133篇
  1991年   101篇
  1990年   70篇
  1989年   60篇
  1988年   64篇
  1987年   55篇
  1986年   48篇
  1985年   37篇
  1984年   41篇
  1983年   15篇
  1982年   17篇
  1981年   25篇
  1980年   14篇
  1979年   16篇
  1978年   12篇
  1977年   13篇
  1976年   15篇
  1975年   8篇
  1971年   10篇
排序方式: 共有9061条查询结果,搜索用时 15 毫秒
31.
32.
33.
Balloon angioplasty is a standard treatment for artherosclerotic coronary artery disease. However, its clinical value is reduced by a high restenosis rate. A new concept in preventing restenosis is the use of a liquid-filled balloon containing a beta-emitting radioisotope. In this study, we performed biodistribution studies of Re-188 perrhenate and Re-188 diethylenetriaminopentaacetate (DTPA) to assess the resulting organ dose values in the event of balloon rupture if these agents are used for the clinical inhibition of restenosis after percutaneous transluminal coronary angioplasty (PTCA). After injecting Re-188 preparations intravenously, rats were killed at 10 min, 30 min, 60 min, 2 h, and 6 h ( n =5 per group). Tissue concentrations were calculated and expressed as percent injected dose per gram or per milliliter (%ID/g or %ID/mL). In addition, urine excretion and thyroid gland uptake were evaluated in rats ( n=5 per group) with a gamma camera after administration of 37 MBq (1 mCi) of each agent. Our data showed that both agents were excreted primarily via urine. However, the excretion of Re-188 DTPA was much faster than that of Re-188 perrhenate via the urinary system. The biodistribution data revealed that radioactivity levels in the stomach and the thyroid gland were high in the perrhenate group but low in the Re-188 DTPA group. The concentration levels in other tissues including lung, liver, testis, muscle, and blood were low throughout this study for both agents. The thyroid radiation value in the Re-188 perrhenate group was 0.163 mGy/MBq, which was much higher than that of the Re-188 DTPA group (0.0167 mGy/MBq). The stomach radiation value was as high as 0.127 mGy/MBq for Re-188 perrhenate, compared with 0.013 mGy/MBq for Re-188 DTPA. In conclusion, in the event of balloon rupture, the release of Re-188 DTPA results in lower radiation doses than Re-188 perrhenate, especially to the thyroid gland and the stomach. Our data suggest that Re-188 DTPA is a useful radiopharmaceutical for endovascular irradiation.  相似文献   
34.
The safety and efficacy of flomoxef and latamoxef were compared in the treatment of hospitalized patients with sepsis and/or Gram-negative bacteremia in a prospective, open-labelled clinical trial. Patients were randomized to receive 1 to 2 g intravenous doses of either flomoxef every 6 to 12 h, or latamoxef every 8 to 12 h. Data from 21 patients given flomoxef and 23 patients given latamoxef were included in the evaluation of efficacy. Flomoxef produced clinical cure and satisfactory microbiological responses in 85.7% and 100% of patients, respectively. These results were similar to those obtained with latamoxef (87% and 100%, respectively). In addition, no significant difference was found in mean age, sex, severity of infection, distribution of pathogens and focus of infection between the two groups. However, the flomoxef group included more patients with ultimately fatal diseases. Six patients given flomoxef and two patients given latamoxef developed superinfections caused by yeast, enterococci and Pseudomonas aeruginosa in the urinary tract. Mild and reversible adverse reactions probably related to flomoxef and latamoxef were noted in 14.3% and 13% of patients, respectively. The results of this study demonstrated that flomoxef is a safe and effective antimicrobial agent in the treatment of patients with sepsis and/or Gram-negative bacteremia.  相似文献   
35.
The association between multiple births and subsequent maternal breast cancer risk was explored in a nested case-control study in Sweden encompassing 19,368 parous women with breast cancer diagnosed up to age 65 years, and 100,459 parous controls. Among cases and controls, there were 329 and 2,031 women, respectively, with a history of at least one live multiple birth. Compared with singleton mothers, breast cancer risk was 12 percent lower (odds ratio=0.088, 95 percent confidence interval=0.78–0.99) in women who had had a multiple birth. After stratification for age at diagnosis, evidence of a significant inverse association was found only in women aged 54 years or younger. Birth order of the multiple pregnancy had no apparent risk-modifying effect. Age at earliest multiple birth was unrelated to breast cancer risk. The inverse association between twinning and breast cancer risk may reflect protective physiological features of twin pregnancies. Further research is needed to investigate the role, if any, of in creased levels of steroid hormone-binding globulins in mothers of twins and the proposed inhibitory effects of human chorionic gonadotropin and -fetoprotein, both of which are increased during multiple gestations, on breast carcinogenesis. Breast feeding patterns in mothers of twins also may modify their risk of developing breast cancer.Ambors are with the Department of Cancer Epidemiology (Drs Lambe Ekbom, Adami) and Department of Social Medicine (Lambe), University Hospital, Uppsala, Sweden: Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA (Drs Hsieb, Tsilib, Adami, Ekbom, Trichopoulos); UMASS Cancer Center, Worcester, MA, USA (Dr Hsieb). Address correspondece to Dr Lambe, Department of Cancer Epidemiology, University Hospital, S-751 85 Uppsala, Sweden. This project is funded by grants from the Swedish Cencer Societv. the Swedish Societv of Medicine. and the Wahlmarks Fund at Uppsala City Council.  相似文献   
36.
We report a "stuck" twin, in which a reverse blood shunt from the recipient to the donor was detected by Doppler sonography after death of the donor. This acute reverse transfusion caused intrauterine fetal distress and severe neonatal anemia of the surviving recipient. We believe that acute hemodynamic change after death of one fetus, in addition to causing a derangement in coagulation, causes immediate danger or subsequent organ damage for the surviving co-twin.  相似文献   
37.
38.
Doppler velocimetry of the umbilical and intraplacental fetal arteries was studied by color flow mapping in 39 normal pregnancies. The systolic-diastolic ratio (S/D) and pulsatility index of the intraplacental fetal artery downstream to the umbilical artery decreased significantly with advancing gestational age, and its S/Ds were persistently lower than those of the umbilical artery. The difference in the S/D between the umbilical artery and its intraplacental downstream branches decreased with advancing gestational age and approached zero as the pregnancy progressed to term. We conclude that intraplacental fetal arteries, possibly fetal arteries in main stem villi, can be imaged by color flow mapping and that there is a significant "resistance gradient" between the intraplacental fetal artery and the umbilical artery. Intraplacental fetal artery velocimetry using color flow mapping may give further insights into the umbilical-placental circulation.  相似文献   
39.
Although there were some studies on clinicopathologic characteristics, operative morbidity, and mortality in elderly patients with gastric cancer, no reports have specifically focused on survival and quality of life after resection. A total of 433 patients aged ≥ 65 years (1987–1994) who underwent gastric resection for gastric adenocarcinoma were studied. Two groups were considered: patients aged 65 to 74 years and those > 74 years. Most of the patients (78.1%) had advanced diseases, and nearly half (41.3%) had associated chronic disease(s). Resections with curative intention were performed in 362 patients (83.6%). The overall operative morbidity rate was 21.7% and mortality rate 5.1%. Although operative procedures were similar in both groups, patients aged >74 years had a higher mortality rate than those aged 65 to 74 years (10.1% vs. 3.5%; p= 0.034). Age and extent of gastric resection were two independent factors negatively affecting mortality. The cumulative survival rates for patients who underwent curative resection were 86.2%, 72.4%, 67.2%, 62.9%, and 60.0% at 1, 2, 3, 4, and 5 years, respectively. Nearly all patients (96%) after surgery had normal work and daily activities. Some patients appeared to lack energy (16%) or experienced a period of anxiety or depression. There was no statistical difference in survival and quality of life assessed by the Spitzer index after curative resection between the two groups. Therefore resection with curative intention can be performed for the elderly with acceptable morbidity and mortality rates, possible long-term survival, and good quality of life, but a limited operation should be considered in the very elderly patients.  相似文献   
40.
BACKGROUND AND PURPOSE: Primary angle-closure glaucoma (PACG) is the predominant form of glaucoma among Asians. Although numerous studies have been done to describe the characteristic optic disc changes in patients with primary open angle glaucoma (POAG) which is the predominant form of glaucoma among Western populations, few studies have evaluated the optic disc changes in patients with PACG. The aim of this study was to elucidate the characteristic intrapapillary and parapapillary disc changes in PACG in a cross-sectional study and to develop a practical approach to the detection of glaucomatous optic disc changes in PACG by ophthalmoscopic examination. METHODS: A total of 103 eyes in 103 PACG patients were studied. Forty one eyes of 41 age- and sex-matched healthy subjects served as controls. Three glaucoma-trained subspecialists examined stereophotographs of optic discs to evaluate the intrapapillary and parapapillary changes. The differences in PACG and control group eyes were compared. RESULTS: Concentric steep enlargement of the optic disc was found in 99 PACG eyes (96%). Local notching was noted in only 3 eyes, and vertically oval-shaped cupping of the optic disc in only 1 eye. Disc hemorrhage was not detected in any eye. Parapapillary atrophy of the alpha zone involving both temporal and nasal side of the optic disc and parapapillary atrophy of beta zone were significantly more frequent in the PACG group. The presence of an alpha zone or a beta zone simultaneously involving both the temporal and nasal side of the optic disc was associated with more severe optic nerve head damage. CONCLUSIONS: The intrapapillary change in the PACG group eyes reflected the development of cupping in PACG patients with small and compact optic discs. The parapapillary atrophy paralleled the intrapapillary optic disc cupping in eyes of the PACG group.  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