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   9011篇
  免费   458篇
  国内免费   75篇
耳鼻咽喉   116篇
儿科学   181篇
妇产科学   321篇
基础医学   896篇
口腔科学   209篇
临床医学   758篇
内科学   2371篇
皮肤病学   126篇
神经病学   547篇
特种医学   359篇
外科学   1764篇
综合类   39篇
预防医学   366篇
眼科学   181篇
药学   431篇
中国医学   4篇
肿瘤学   875篇
  2023年   54篇
  2022年   155篇
  2021年   279篇
  2020年   160篇
  2019年   236篇
  2018年   258篇
  2017年   179篇
  2016年   205篇
  2015年   207篇
  2014年   369篇
  2013年   438篇
  2012年   712篇
  2011年   761篇
  2010年   440篇
  2009年   427篇
  2008年   697篇
  2007年   703篇
  2006年   598篇
  2005年   509篇
  2004年   458篇
  2003年   411篇
  2002年   365篇
  2001年   124篇
  2000年   74篇
  1999年   101篇
  1998年   67篇
  1997年   43篇
  1996年   42篇
  1995年   37篇
  1994年   34篇
  1993年   22篇
  1992年   43篇
  1991年   25篇
  1990年   50篇
  1989年   42篇
  1988年   25篇
  1987年   28篇
  1986年   20篇
  1985年   19篇
  1984年   13篇
  1983年   9篇
  1982年   13篇
  1981年   9篇
  1980年   7篇
  1977年   6篇
  1976年   7篇
  1974年   11篇
  1973年   8篇
  1970年   7篇
  1966年   5篇
排序方式: 共有9544条查询结果,搜索用时 15 毫秒
71.
Diagnostic nuclear medicine procedures in a large hospital in northern Greece during 1984–1988 have been surveyed in order to estimate the radiation burden to the patients. The mean effective dose equivalent (EDE) was found to be 1.96 mSv/examination and 2.46 mSv/patient, allowing for the fact that a number of patients underwent more than one examination. Apart from EDE, absorbed dose has been calculated for bone marrow, thyroid, gonads, kidneys and bladder. Patients undergoing multiple examinations have been used to calculate true patient dose distribution as well as patient time-weighted dose distribution. Because of the predominance of renal examinations, 8.5 fatal renal malignancies are expected per 100000 patients.  相似文献   
72.
Human pulmonary adenocarcinomas (AC) can be divided into two types with special morphologic and immunohistologic properties and a different number of tumor-infiltrating cells as shown by previous investigations. In the present study the relevance of this subdivision for patients' survival was investigated. 42 surgically resected pulmonary AC of stage I and II were subclassified using light and electron microscope. For immunohistologic phenotypization, reactions with monoclonal antibodies against HLA-DR, CD1 and CD3 were studied on fresh tumor specimens. Postoperative survival was evaluated after at least 24 months. AC of type I (N=23) with mucin production and ultrastructural properties of goblet cells showed almost no HLA-DR expression. Infiltration by CD1-positive dendritic cells Langerhans cells and CD3-positive T lymphocytes was significantly lower than in AC of type II (N=19), which expressed HLA-DR homogeneously and showed, ultrastructurally, Clara cell and/or type II pneumocyte properties. Patients' outcome was similar in stage I AC of both types: about 70% of patients were still alive after 24 months. However, significant differences were found between the two types in stage II AC with regional lymph node metastases: survival of patients with AC of type II corresponded roughly with stage I tumors (67%) but only 20% of patients with type I AC were still alive after 24 months. These results indicate that postoperative prognosis for patients with pulmonary AC of type II is more favourable than for mucinous AC of type I. This may be due to the homogeneous HLA-DR expression and higher number of immunologically competent tumor-infiltrating cells which possibly results in better tumor surveillance.  相似文献   
73.
Previous studies have shown that cortical interneurons, presumably GABAergic, are among the targets of the noradrenaline (NA)-containing cortical afferents and that NA interacts with neuropeptides at various cellular levels. The present study attempts to characterize further the cortical targets of the NA afferents by examining, at the light and the electron microscopic level, the anatomical relationships of the NA fibers with three subpopulations of cortical interneurons, those containing somatostatin (SRIF), neuropeptide Y (NPY) or vasoactive intestinal polypeptide (VIP). For this purpose, a double preembedding immunoprocedure with antibodies against NA and SRIF, NPY or VIP was combined with the gold-substituted silver peroxidase method. Light microscopic examination showed that NA fibers contact perikarya and proximal dendrites of the SRIF, NPY and VIP neurons. However, NA fibers, while found to form pericellular arrays around NPY neurons and, to a lesser extent, around SRIF neurons, were seen to target VIP cortical cells with single terminal varicosities. Electron microscopy revealed that all peptidergic populations examined represent synaptic targets for the NA fibers. The NAergic synapses, localized onto the cell body and proximal dendrites of the peptidergic neurons, were always of the symmetrical variety. Results of the present study provide the morphological basis for the explanation of the functional interaction between the NA cortical afferent system and the intrinsic cortical elements.  相似文献   
74.
75.
OBJECTIVE: To classify the white senile cataracts and report the results of phacoemulsification of white cataracts. DESIGN: Prospective, noncomparative case series. PARTICIPANTS: One hundred eyes were included. INTERVENTION: White cataracts were examined biomicroscopically before surgery, and their acoustic structure was analyzed with standardized A-scan echography. White cataract surgery was performed with phacoemulsification via a superior temporal near-limbus corneal approach using a bimanual divide-and-conquer or stop-and-chop technique. Patients were followed after surgery for a period of 9 months. MAIN OUTCOMES MEASURES: The A-scan acoustic structure of white cataracts; successful accomplishment of capsulorrhexis; mean phacoemulsification time, power, and energy; intraoperative and postoperative complications of phacoemulsification; and visual acuity at 9 months after surgery. RESULTS: White senile cataracts were categorized into three different types. Type I included intumescent, white cataracts with cortex liquefaction and high internal acoustic reflections (44 eyes), type II included white cataracts with voluminous nuclei, little amount of whitish solid cortex, and low internal acoustic reflections (49 eyes), and type III included white cataracts with fibrosed anterior capsule and low internal echospikes (7 eyes). Circular capsulorrhexis was completed in 79 eyes and was significantly less successful in eyes with type I intumescent, white cataracts compared with type II white cataracts (P = 0.0034). Mean phacoemulsification time and energy were higher in type II and type III white cataracts. Posterior capsule rupture occurred in ten eyes, and three of these eyes were complicated by vitreous loss. In 95 eyes, the posterior chamber lens was implanted in the capsular bag and in five eyes in the sulcus. After surgery, a transient corneal edema developed in 31 eyes. At the final 6-month examination, the mean postoperative visual acuity was 20/30. CONCLUSION: Current phacoemulsification techniques can safely manage eyes with senile white cataracts. The increased risk of difficulty with continuous capsulorrhexis in type-I and type-III white cataracts and the substantial nuclear hardness in type-II and mainly type-III white cataracts would suggest that current phacoemulsification techniques might not be as successful in these patients as they are in ordinary earlier cataracts.  相似文献   
76.
To evaluate the prognostic value of ERG in cases of central retinal vein occlusion (CRVO) regarding the development of neovascularisation (NV), we studied 20 patients with unilateral CRVO. Half of them were allocated in the perfused group and the other 10 finally developed NV and were allocated in the non-perfused group. Flash ERG was recorded from all patients. Our findings suggest that b-wave latency is the most reliable parameter in predicting NV, followed by the a-wave latency. The b/a wave amplitude of ERG ratio does not seem to be suitable for clinical use. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
77.
78.
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   
79.
80.
PURPOSE: The purpose of this study was to establish the feasibility and efficacy of preoperative radiotherapy (RT) with concurrent capecitabine and oxaliplatin (XELOX-RT) in patients with rectal cancer. PATIENTS AND METHODS: Thirty-two patients with locally advanced (T3/T4) or low-lying rectal cancer received preoperative RT (total dose, 50.4 Gy). Capecitabine was administered concurrently at 825 mg/m2 bid on days 1 to 14 and 22 to 35, with oxaliplatin starting at 50 mg/m2 on days 1, 8, 22, and 29 with planned escalation steps of 10 mg/m2. End points of the phase II study included downstaging, histopathologic tumor regression, resectability of T4 disease, and sphincter preservation in patients with low-lying tumors. RESULTS: Dose-limiting grade 3 gastrointestinal toxicity was observed in two of six patients treated with 60 mg/m2 of oxaliplatin. Thus, 50 mg/m2 was the recommended dose for the phase II study. Toxicities observed at this dose level were generally mild, with only two cases of short-lived grade 3 diarrhea. Myelosuppression, mainly leukopenia, was restricted to grade 2 in 19% of patients. T-category downstaging was achieved in 17 (55%) of 31 operated patients, and 68% of patients had negative lymph nodes. Pathologic complete response was found in 19% of the resected specimens. Radical surgery with free margins could be performed in 79% of patients with T4 disease, and 36% of patients with tumors < or = 2 cm from the dentate line had sphincter-saving surgery. CONCLUSION: Preoperative XELOX-RT is a feasible and well tolerated treatment. This regimen is proposed for phase III evaluation comparing standard fluorouracil-based therapy with XELOX chemoradiotherapy.  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