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   280647篇
  免费   7553篇
  国内免费   654篇
耳鼻咽喉   2159篇
儿科学   10043篇
妇产科学   5441篇
基础医学   31976篇
口腔科学   5465篇
临床医学   22032篇
内科学   54809篇
皮肤病学   3446篇
神经病学   26726篇
特种医学   11211篇
外国民族医学   1篇
外科学   37965篇
综合类   2708篇
一般理论   51篇
预防医学   28590篇
眼科学   4487篇
药学   16886篇
中国医学   1077篇
肿瘤学   23781篇
  2024年   88篇
  2023年   1026篇
  2022年   1935篇
  2021年   3873篇
  2020年   2394篇
  2019年   3238篇
  2018年   24937篇
  2017年   19661篇
  2016年   22181篇
  2015年   4414篇
  2014年   5433篇
  2013年   6818篇
  2012年   16011篇
  2011年   30148篇
  2010年   23587篇
  2009年   15663篇
  2008年   26624篇
  2007年   28754篇
  2006年   7441篇
  2005年   8559篇
  2004年   9135篇
  2003年   9417篇
  2002年   7099篇
  2001年   810篇
  2000年   785篇
  1999年   753篇
  1998年   1004篇
  1997年   869篇
  1996年   651篇
  1995年   565篇
  1994年   529篇
  1993年   421篇
  1992年   338篇
  1991年   280篇
  1990年   319篇
  1989年   266篇
  1988年   228篇
  1987年   190篇
  1986年   187篇
  1985年   146篇
  1984年   155篇
  1983年   153篇
  1982年   194篇
  1981年   125篇
  1980年   170篇
  1979年   83篇
  1978年   89篇
  1977年   78篇
  1976年   71篇
  1974年   72篇
排序方式: 共有10000条查询结果,搜索用时 318 毫秒
151.
Objective: To study the diagnostic value of T2^*-weighted first-pass perfusion imaging in breast tumors. Methods: We analyzed the magnetic resonance imaging (MRI) information along with the pathological and immunohistochemistry results. Magnetic resonance imaging was performed in 28 patients with breast tumor. The time to signal intensity curves were generated according to the T2^*-weighted first-pass perfusion imaging. The curve's maximal signal intensity drop rate and maximal signal intensity decrease time were analyzed and compared with the pathological diagnoses after surgery. Results: Malignant breast lesions showed higher maximal signal intensity drop rate (44.69% ± 17.07 vs. 17.22% ±7.49, P 〈 0.001) than benign lesions, but there was no significant difference of maximal signal decrease time between those two lesions (23.94 s ± 4.92 vs. 20.02 s ± 6.83, P 〉 0.05). Conclusion: The T2^*-weighted first-pass perfusion imaging has enough sensitivity and specificity in breast tumor diagnosis.  相似文献   
152.
153.
To evaluate the impact of pregnancy on bone, we studied bone turnover at the first (T1) and third (T3) trimester of gestation in 58 adolescents and 28 healthy adolescents who had never been pregnant. Total body (TB) and lumbar spine (LS) bone mineral density (BMD) and body composition were evaluated by dual-energy X-ray absorptiometry in all control patients (C) and after parturition in 28 pregnant patients (G). Paired and unpaired t tests, Mann-Whitney and Pearson correlation tests were used. Bone turnover markers were above the reference range for adult women in more than 80% of the adolescents, with no difference between C and G patients at T1. Increase in urinary N-telopeptide crosslinks of type I collagen and serum bone-specific alkaline phosphatase, markers of bone turnover, was seen during pregnancy ( p < 0.0001). Body composition did not differ between groups, but LS BMD, percentage of expected LS BMD, LS Z-score, percentage of expected TB BMD and TB Z-score were lower in G than C patients ( p < 0.05). TB BMD was positively correlated with LS BMD (r2 = 0.52). The inverse correlations between bone markers and LS BMD suggest that the increased bone turnover during pregnancy probably explains the low bone density after parturition. The impact on future peak bone mass must be studied.  相似文献   
154.
155.
We found multimolecular antigenic mimicry of arthritogenic autoantigens and peptides from several other “self” or foreign antigens sharing amino acid sequence homologies. Many of these new mimotopes induced arthritis and/or uveitis upon immunization in Lewis rats, indicating a role for multiple antigens in the initiation of a certain autoimmune disease.  相似文献   
156.
During May 1986, a survey to assess the frequency of allergic disorders was conducted among primary school children of Alghero, Sardinia, using a structured self-administered questionnaire. The following problems were investigated: allergic conjunctivitis, asthma, wheezing, allergic rhinitis, urticaria and eczema. Of the original 1823 questionnaires distributed, 1961 (92.8%) were completed by parents and returned. Overall, 238 children (14.1%) were reported to have shown at least one episode of one or more of the above and were regarded as 'allergic'. Among the potential risk factors investigated, statistically significant differences (P less than 0.05) between allergic and non-allergic children were only found for history of allergy in at least one parent (odds ratio, OR = 2.2) and exposure to passive smoking (OR = 1.4).  相似文献   
157.
Monoamine oxidase A gene promoter (MAOA-uVNTR) and catechol-O-methyltransferase V158M (COMT-V158M) gene functional polymorphisms are reported to be associated with impulsive-aggression, but a biological intermediate effect remains to be determined. This study assessed the association of these polymorphisms with cerebrospinal fluid (CSF) monoamine metabolites as endophenotypes. Ninety-eight Caucasian psychiatric subjects were assessed for Axis I and II diagnosis. Subjects were genotyped for the functional polymorphisms, MAOA-uVNTR and COMT-V158M. CSF was obtained by lumbar puncture. Relationships of the two polymorphism to monoamine metabolites: HVA, 5-HIAA, and MHPG were examined. The higher-expressing MAOA-uVNTR genotype was associated with higher CSF-HVA levels in males only (n = 46) (195.80 pmol/ml, SD = 61.64 vs. 161.13, SD = 50.23, respectively; P = 0.042). No association was found with diagnosis. COMT-V158M had no association with CSF monoamine metabolites. The association of MAOA-uVNTR with dopaminergic activity in males is a preliminary finding that needs to be replicated in a larger sample of Caucasian males and relationships sought with clinical phenotypes. This article contains supplementary material, which may be viewed at the American Journal of Medical Genetics website at http://www.interscience.wiley.com/jpages/0148-7299:1/suppmat/index.html.  相似文献   
158.
159.
160.
Abstract We report a case of SMV injury in a critically ill patient. The patient was a 19-year-old woman involved in a motor vehicle collision. Her injuries included grade II splenic and renal lacerations, devascularized and lacerated right and transverse colon, a transected transverse mesocolon, a massive shear injury of her abdominal wall, and two partial SMV transections. At initial damage control laparotomy, the SMV was ligated, the devascularized bowel resected and a temporary abdominal closure applied. At re-operation, a mesocaval shunt using saphenous vein was employed. The shunt failed and the patient required a saphenous vein jump graft. Although visceral vascular injuries are rare, ligation of the SMV in a damage control situation is acceptable. This case study is the first to discuss appropriate treatment when interruption to a patient's collateral visceral venous drainage limits the surgeon’s ability to ligate. In these situations, bypass shunts may be successful.  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