全文获取类型
收费全文 | 31521篇 |
免费 | 2985篇 |
国内免费 | 940篇 |
专业分类
耳鼻咽喉 | 241篇 |
儿科学 | 1358篇 |
妇产科学 | 420篇 |
基础医学 | 5173篇 |
口腔科学 | 686篇 |
临床医学 | 3132篇 |
内科学 | 4818篇 |
皮肤病学 | 561篇 |
神经病学 | 2485篇 |
特种医学 | 389篇 |
外国民族医学 | 6篇 |
外科学 | 1611篇 |
综合类 | 3414篇 |
现状与发展 | 7篇 |
预防医学 | 5432篇 |
眼科学 | 492篇 |
药学 | 1389篇 |
32篇 | |
中国医学 | 421篇 |
肿瘤学 | 3379篇 |
出版年
2024年 | 105篇 |
2023年 | 580篇 |
2022年 | 1144篇 |
2021年 | 1517篇 |
2020年 | 1396篇 |
2019年 | 1331篇 |
2018年 | 1183篇 |
2017年 | 1250篇 |
2016年 | 1240篇 |
2015年 | 1267篇 |
2014年 | 1979篇 |
2013年 | 2319篇 |
2012年 | 1770篇 |
2011年 | 1878篇 |
2010年 | 1481篇 |
2009年 | 1602篇 |
2008年 | 1667篇 |
2007年 | 1556篇 |
2006年 | 1350篇 |
2005年 | 1172篇 |
2004年 | 1049篇 |
2003年 | 936篇 |
2002年 | 795篇 |
2001年 | 725篇 |
2000年 | 572篇 |
1999年 | 561篇 |
1998年 | 538篇 |
1997年 | 428篇 |
1996年 | 336篇 |
1995年 | 323篇 |
1994年 | 229篇 |
1993年 | 189篇 |
1992年 | 144篇 |
1991年 | 137篇 |
1990年 | 95篇 |
1989年 | 92篇 |
1988年 | 80篇 |
1987年 | 50篇 |
1986年 | 40篇 |
1985年 | 76篇 |
1984年 | 49篇 |
1983年 | 33篇 |
1982年 | 38篇 |
1981年 | 34篇 |
1980年 | 27篇 |
1979年 | 22篇 |
1978年 | 15篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1970年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
This paper reports the prevalence of chronic esophagitis and nutritional status among 538 young persons aged 15 to 26 years from the high risk area for esophageal cancer. Of these subjects, 166 were from households with history of esophageal cancer and 372 were from households without history of esophageal cancer. The Incidences of chronic esophagltis among male and female adolescents were 37. 6% and 36% respectively, which was significantly higher than those in the low risk area (17%). The frequency of chronic esophagltis in the adolescents in the households with history of esophageal cancer was aiso higher than in those In the households without history of esophageal cancer. The deficiencies of vitamins, especially of riboflavin and ascorbate, are prevalent and severe among these adolescents. Ascorbate deficiency Is correlated with the severity of the chronic esophagltis. These results indicate that chronic esophagltis may be involved in the natural history of esophageal carclnogenesis. Nutrient defic 相似文献
32.
The normally expressed κ immunoglobulin light chain gene repertoire and somatic mutations studied by single-sided specific polymerase chain reaction (PCR); frequent occurrence of features often assigned to autoimmunity 下载免费PDF全文
L JUUL L HOUGS V ANDERSEN A SVEJGAARD T BARINGTON 《Clinical and experimental immunology》1997,109(1):194-203
The expressed human κ light chain gene repertoire utilized by healthy individuals was studied by two different single-sided specific PCR techniques to avoid bias for certain V genes. A total of 103 rearranged κ sequences from peripheral blood mononuclear cells from healthy individuals were cloned from cDNA and assigned to the Vκ and Jκ germ-line genes with the closest overall homology. The use of cDNA rather than genomic DNA focused the analysis on activated B cells rich in mRNA. Accordingly, the sequences represented the applied repertoire and almost all were somatically mutated. V genes from the Jκ-proximal duplication unit of the κ locus were almost exclusively used. A total of 65% of the sequences could be assigned to four or five genes: A27 (humkv325), L6 (Vg), L2 (humkv328), and A3 and/or A19. N additions and P nucleotides were quite common and found in 32% and 21% of the sequences, respectively. Extended CDR3s more than nine residues in length were found in 18% of the sequences, and in 71% of cases this was due to insertion of an extra proline residue. This proline was usually explained from the germ-line sequences involved. These results are in good agreement with those of previous repertoire studies using potentially V-gene-biased techniques. Thus, it is clear that restricted V-gene usage, common N and P additions, and extended CDR3 regions are normal features and not, as has been claimed, characteristics of pathological autoantibodies. 相似文献
33.
T. Ariga Y. Sakiyama K. Tomizawa S. Imajoh-Ohmi S. Kanegasaki S. Matsumoto 《European journal of pediatrics》1993,152(6):469-472
Molecular genetic analysis was performed in a patient with cytochrome b positive X-linked chronic granulomatous disease. A previous Southern blot study, using a cytochrome b heavy chain cDNA as probe, revealed a Pst I restriction fragment pattern for the cytochrome b heavy chain gene (CYBB) different to that of normal individuals. Since restriction length polymorphism with Pst I has never been observed in control individuals and no abnormal restriction fragment patterns in the patient's CYBB was detected with seven other enzymes used, we focussed on the single Pst I site in the CYBB cDNA as being the only mutation site responsible for his disease. A fragment of the patient's cDNA which included the Pst I site was amplified by reverse polymerase chain reaction, and loss of the Pst I site in the fragment was confirmed by incubation with Pst I. Subsequent sequence analysis of the fragment revealed a point mutation in the Pst I site (cytosine to adenine), substituting glutamic acid for alanine at position 57. 相似文献
34.
A significant minority of medical and dental students fail their undergraduate courses. Early warning systems (EWSs) have been developed in some areas of higher education to predict 'at-risk' students at an early remedial stage. An attempt is made to develop an EWS to predict failure in the bacteriology component of the Batchelor of Dental Surgery course at Manchester Dental School. A system based on class tests and previous end-of-year performance is derived which is used to predict those students likely to fail or fall in the bottom 20-25% in their finals examination. The predictors are combined by a simple equal weights method, which is found to have the same predictive power as using multiple regression. Failure was correctly predicted in 60% of cases, at the expense of 71% false alarms. The high number of false alarms reflects the low failure rate rather than the lack of predictive information. The need for effective cross-validation of EWSs is discussed; many previous studies have not been tested on independent data. 相似文献
35.
Linda S. Scheirton Ph.D. 《HEC forum》1992,4(6):342-359
In December 1990, an empirical study assessing hospital ethics committee (HEC) success was completed. Success was measured in terms of the number of interventions undertaken by the committees in four functional areas: education, guidelines development, prospective and retrospective case review. Some commonly quoted success determinants, such as multidisciplinarity, physician chairpersons, and a high institutional status of the chairperson were found not to foster success; the latter two, actually decreased committee success. 相似文献
36.
37.
Summary;To investigate the distribution of possible novel mutations from parkin gene in variant sub-set of patients with Parkinson’s disease(PD)in China and explore whether parkin gene plays an im-portant role in the pathogenesis of PD,70 patients were divided into early-onset group and late-onsetgroup; 70 healthy subjects were included as controls.Genomic DNA from 70 normal controls andfrom those of PD patients were extracted from peripheral blood leukocytes by using standard proce-dures.Mutations of parkin gene(exon 1—12)in all the subjects were screened by PCR-single strandconformation polymorphism(SSCP),and further sequencing was performed in tue samples with ab-normal SSCP results,in order to confirm the mutation and its location.A new missense mutationGly284Arg in a patient and 3 abnormal bands in SSCP electrophoresis from samples of another 3 pa-tients were found.All the DNA variants were sourced from the samples of the patients with early-on-set PD.It was concluded that Parkin point mutation a 相似文献
38.
39.
Dietary intake in the elderly estimated by a 24 hour recall and a food frequency questionnaire 总被引:1,自引:0,他引:1
P. Caughey C. E. A. Seaman† D. A. Parry† D. L. Farquhar‡ W. J. MacLennan§ R. Prescott§ 《Journal of human nutrition and dietetics》1994,7(3):209-213
Two hundred and thirty-five tenants living in sheltered housing in Scotland were surveyed to identify the extent of under-nutrition and the social factors which contribute to its development. A validated 24 h recall and the nutrient checklist published by NAGE were used to evaluate patterns of dietary intake. A questionnaire was developed which included scales designed to measure depression, social engagement, cognitive function, mobility and functional ability. The results show considerable evidence of a number of major nutrients in which there were low intakes. In order to express the extent of poor nutrition, a nutrient score was developed where points are awarded based on the number of nutrients falling below the Lower Reference Nutrient Intake, the Estimated Average Requirement or below half the daily Estimated Average Requirement. 相似文献
40.
使用赤灵芝的水提取液、乙醇(30%)提取液进行鼠伤寒沙门氏菌回复、小鼠骨髓多染红细胞微核和雄小鼠精子畸变等三种致突变试验。剂量为1000μg.皿^-1和5000μg/皿^-1的鼠伤寒沙门氏菌回复试验的结果为阴性。小鼠在服用7500mg.kg^-1的水提取液或2500mg.kg^-1的醇提取液时,微核试验和精子畸变试验结果均为阴性。 相似文献