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   115082篇
  免费   6993篇
  国内免费   795篇
耳鼻咽喉   1255篇
儿科学   3746篇
妇产科学   2849篇
基础医学   15468篇
口腔科学   2517篇
临床医学   9702篇
内科学   25233篇
皮肤病学   2365篇
神经病学   10749篇
特种医学   4386篇
外国民族医学   24篇
外科学   15558篇
综合类   1830篇
一般理论   71篇
预防医学   7106篇
眼科学   1840篇
药学   9038篇
  3篇
中国医学   547篇
肿瘤学   8583篇
  2023年   535篇
  2022年   1194篇
  2021年   2232篇
  2020年   1440篇
  2019年   2053篇
  2018年   2480篇
  2017年   1899篇
  2016年   2037篇
  2015年   2314篇
  2014年   3114篇
  2013年   4520篇
  2012年   6125篇
  2011年   6446篇
  2010年   4066篇
  2009年   3586篇
  2008年   5557篇
  2007年   5901篇
  2006年   5485篇
  2005年   5260篇
  2004年   5523篇
  2003年   5310篇
  2002年   5318篇
  2001年   4084篇
  2000年   4063篇
  1999年   3380篇
  1998年   1327篇
  1997年   1041篇
  1996年   959篇
  1995年   920篇
  1994年   800篇
  1993年   778篇
  1992年   2051篇
  1991年   2004篇
  1990年   1753篇
  1989年   1689篇
  1988年   1512篇
  1987年   1342篇
  1986年   1335篇
  1985年   1250篇
  1984年   884篇
  1983年   796篇
  1982年   534篇
  1981年   441篇
  1979年   681篇
  1978年   473篇
  1977年   439篇
  1975年   489篇
  1974年   531篇
  1973年   524篇
  1972年   461篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
PurposeTo analyze the electroclinical features, aetiology and outcome in patients with normal neurological examination and psychomotor development who presented seizures during a mild gastroenteritis (MG).Patients and methodsEvaluation of the clinical charts of 22 patients who were assessed in the Neurology Department, Hospital Nacional de Pediatría Prof. Dr. JP Garrahan between 1999 and 2007.ResultsTwelve patients were boys and 10 were girls, the age of onset ranged from 5 to 26 months, and the median age was 10 months. Rotavirus antigen test in stool was positive in 9 of 18 studied patients. The seizures were brief, focal with secondary generalization in 15 patients (68.5%), apparently generalized in 5 (22.5%) and focal in two (9%). Seven of the patients (35%) had more than one seizure in 24 h. The interictal EEG was normal in all patients. Neuroradiological studies were performed in 19 patients with a normal result. No patient was put on long-term treatment with antiepileptic drugs. Four patients had subsequent mild gastroenteritis and two of them presented convulsions during the disease. After between 12 and 67 months of follow-up, all patients had normal psychomotor development and neurological examination.ConclusionsIn this study we confirmed the association of benign infantile seizures (BIS) and MG with or without rotavirus. The identification of this entity allows avoiding unnecessary complementary studies and treatment with antiepileptic drugs.  相似文献   
22.
Five 3'-fluorinated ribonucleosides were prepared and evaluated for their inhibitory properties against different viruses. The synthesis of these compounds was achieved by treatment of 2',5'-di-O-tritylated nucleoside analogues possessing a xylo-configuration with diethylaminosulfur trifluoride, followed by deprotection. 3'-Fluoro-3'-deoxyadenosine was active against a broad range of viruses, encompassing both DNA viruses [pox (vaccinia)], single-stranded (+) RNA viruses [picorna (polio, Coxsackie B), toga (sindbis, Semliki Forest)] and double-stranded RNA viruses (reo). In its antiviral activity spectrum 3'-fluoro-3'-deoxyadenosine clearly differed from those adenosine analogues that are known as inhibitors of S-adenosylhomocysteine hydrolase. 3'-Fluoro-3'-deoxyadenosine also proved effective in vivo, in inhibiting tail lesion formation in mice inoculated intravenously with vaccinia virus.  相似文献   
23.
Clinical and biological data were evaluated using Desu univariate analyses or Cox multivariate analyses in a series of 1,777 chronic lymphocytic leukemia (CLL) patients from an Italian Cooperative Group. In univariate analyses, age and sex of patients, presence of bone marrow (BM; greater than or equal to 50%), and peripheral blood (PB; greater than or equal to 60,000/microL) lymphocytosis, anemia (hemoglobin [Hb] less than 11 g/dL), thrombocytopenia (less than 100,000/microL), direct Coombs' test positivity, hepatomegaly, splenomegaly, and extent of lymph node involvement were shown to be of significant prognostic value. Multivariate analyses, through a stepwise procedure, showed that the most important prognostic variables are Hb, hepatomegaly, lymph node involvement, PB lymphocytosis, and age and sex of patients. Further covariates would produce an improvement having a nonsignificant P value. Based on the results of multivariate analyses, a four-step staging using the significant variables of the Cox model is proposed.  相似文献   
24.
Follicular fluids from eight patients with one ovary and from ten patients with two ovaries were investigated for bioactive inhibin, total renin, oestradiol (E2) and progesterone (P4) concentrations. Four follicular fluids were pooled per patient before assessment. All women had been stimulated similarly using a protocol including a GnRH agonist, HMG and HCG. Renin levels were significantly lower and P4 significantly higher in pools of follicular fluid from patients with one ovary, whereas inhibin and E2 concentrations were similar in both patient groups. A significant negative correlation was found in the pools of follicular fluid between inhibin and E2 in both groups. These results suggest a role for inhibin and renin in the paracrine and autocrine control of stimulated follicular development.  相似文献   
25.
This study compared the predictive value of the theory of planned behavior in university students in South Africa (N = 251) and the United States (N = 160) who completed an anonymous self-administered questionnaire. Multiple regression analyses revealed that condom use and intention were significantly predicted by positive condom attitude, subjective norm, self-efficacy, and attending university in South Africa. Significant interactions between country and predictors indicated that subjective norm predicted condom use and intention more strongly in the American sample than in the South African sample; attitude predicted intention more strongly in the American sample than in the South African sample; but self-efficacy predicted intention more strongly in the South African sample than in the American sample. The theory of planned behavior may provide a useful framework for interventions to reduce South African students' risk of HIV/and sexuality transmitted diseases. Such interventions should especially focus on building self-efficacy to use condoms.  相似文献   
26.
Following the outbreak of poliomyelitis in Gazankulu in 1982, the immunisation services in Gazankulu were thoroughly examined. As a result of this, a comprehensive immunisation policy for Gazankulu was accepted in November 1986. The broad aim of the policy is to provide effective immunisation to all Gazankulu residents against tuberculosis, diphtheria, pertussis, tetanus, poliomyelitis and measles. A specific objective is that by the end of 1987, 85% of under-5s should have been vaccinated against these six diseases and by the end of 1990 this percentage should be 97%. The detailed strategies to reach these objectives are highlighted. Within the framework of the objectives, the policy allows different areas to formulate individual strategies. Programme monitoring and community involvement are two crucial aspects of the policy and these are discussed in detail. The early successes and difficulities in implementing this policy are discussed.  相似文献   
27.
Information regarding breast feeding practices of 600 children below 3 years of age attending hospital OPDs and private clinics during 1984-85 were collected. 51.3% received breast milk within 24 hrs. of birth, mean duration of breast feeding being 6 months. 68% of Infants had been given prelacteal feeds. 34% children were exclusively breast fed till 1 month. Insufficient milk was an important reason for discontinuation before 6 months.  相似文献   
28.
29.
The aim of the present study was to assess retrospectively the additional value of positron emission tomography (PET)/computed tomography (CT) in the detection of unexpected extrapulmonary lesions in the staging of patients with a malignant pulmonary lesion in comparison with CT and PET used alone. A total of 217 patients with a pathologically proven lung tumour underwent PET/CT. CT, PET and PET/CT were evaluated in the detection of extrapulmonary lesions. These abnormalities were compared with the final diagnosis obtained from the medical records and statistical analysis was carried out. In total, 108 lesions were clinically detected. PET/CT showed a sensitivity, specificity, positive and negative predictive values and accuracy of 100, 81, 71, 100 and 87%, respectively, for the detection of extrapulmonary lesions and 92, 98, 89, 98 and 97%, respectively, for the detection of malignant extrapulmonary lesions. PET/CT was significantly better than CT and PET used alone. Conventional staging work-up has a poor sensitivity in detecting second primary cancers or unexpected metastases. The detection of malignant extrapulmonary lesions is necessary for correct tumour staging. By combining both metabolic and anatomical information, positron emission tomography/computed tomography is able to depict more unexpected extrapulmonary lesions than computed tomography and positron emission tomography used alone, and positron emission tomography/computed tomography provides more additional information of malignancy or benignancy of lesions detected with one of the two imaging modalities alone.  相似文献   
30.
We describe a modified keyhole laminoforaminotomy (LF) using anatomic landmarks on the posterior aspect of the cervical vertebral body to decompress the intervertebral foramen with minimal bone removal. Twenty-four procedures were performed at C3-4, C4-5, and C5-6; 12 at C6-7; and 3 at C7-Tl. Facets and laminae structures were identified based on relative surgical perspectives. Bony resection was limited as follows: 1) inferior limit; inferior border of the superior facet; 2) superior limit, superior border of the superior facet; 3) lateral limit, a vertical line linking the junction of the lamina-facet to the lateral end of the superior limit; and 4) lateral aspect of the dural sac. Fluoroscopy was used to confirm that the intervertebral space was reached. The amount of bony removal was quantified for the superior and inferior laminae and facets. The length of the exposed nerve root was measured. The intervertebral foramen was exposed and the intervertebral disc reached in all specimens. Fluoroscopy showed that the center of the exposure remained at the same height with the intervertebral space. The mean length of the nerve root was 4.6 mm; the mean percentage of bony resection was 21.8%, 7.5%, 11.3%, and 11.5% for the superior and inferior laminae and facets, respectively. Opening the intervertebral foramen posteriorly consistently exposed sufficient nerve root length and allowed access to the intervertebral disc. The technique offers the most direct and safest method of decompressing the intervertebral foramen while minimizing bony resection. This simple surgical procedure may help reduce postoperative morbidity.  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