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   8343篇
  免费   762篇
  国内免费   259篇
耳鼻咽喉   55篇
儿科学   134篇
妇产科学   268篇
基础医学   1053篇
口腔科学   119篇
临床医学   925篇
内科学   1344篇
皮肤病学   72篇
神经病学   413篇
特种医学   198篇
外国民族医学   3篇
外科学   1122篇
综合类   957篇
现状与发展   3篇
预防医学   552篇
眼科学   32篇
药学   483篇
  7篇
中国医学   236篇
肿瘤学   1388篇
  2024年   24篇
  2023年   120篇
  2022年   252篇
  2021年   335篇
  2020年   312篇
  2019年   275篇
  2018年   259篇
  2017年   304篇
  2016年   368篇
  2015年   328篇
  2014年   656篇
  2013年   648篇
  2012年   431篇
  2011年   553篇
  2010年   414篇
  2009年   424篇
  2008年   434篇
  2007年   445篇
  2006年   371篇
  2005年   307篇
  2004年   261篇
  2003年   230篇
  2002年   191篇
  2001年   173篇
  2000年   143篇
  1999年   127篇
  1998年   108篇
  1997年   76篇
  1996年   89篇
  1995年   81篇
  1994年   83篇
  1993年   55篇
  1992年   57篇
  1991年   47篇
  1990年   45篇
  1989年   42篇
  1988年   32篇
  1987年   39篇
  1986年   25篇
  1985年   44篇
  1984年   32篇
  1983年   29篇
  1982年   25篇
  1981年   22篇
  1980年   12篇
  1979年   15篇
  1978年   12篇
  1977年   5篇
  1976年   2篇
  1974年   1篇
排序方式: 共有9364条查询结果,搜索用时 15 毫秒
31.
Parental origin of de novo deletions in the short arm of chromosome 9 in patients with a clinical diagnosis of del(9p) syndrome was assessed in 13 patients using polymerase chain reaction (PCR) analysis of highly polymorphic dinucleotide repeat micro-satellite markers located in the putative deleted region. The deletion was found to be of paternal origin in 9 cases and of maternal origin in the remaining 4 cases, suggesting that the molecular event resulting in the deletion occurs in both male and female gametogenesis and that genomic imprinting does not appear to play a role in the patho-genesis of del(9p) syndrome. © 1995 Wiley-Liss, Inc.  相似文献   
32.
A new bacterial rosette technique for enumerating T lymphocytes is described. E. coli (strain B; ATCC 11303), fixed in formaldehyde after overnight growth in thioglycolate medium, are mixed with washed whole blood cells (100 μl) and after incubation at 4°C, slides are made, stained and counted. The nature of the lymphocytes forming E. coli rosettes was demonstrated by comparing their cytochemical staining characteristics with those of E rosetted lymphocytes, and by mixed E. coli and E, mouse E rosette and Fc receptor tests, and by mixed E. coli rosette tests and anti-Ig staining. E. coli and E rosette tests in controls and pediatric patients were also compared. The results show that Tμ and Tγ cells rosette with E. coli.  相似文献   
33.
Serological markers of hepatitis B virus (HBV) replication were assessed in a randomized, controlled trial of prednisone withdrawal followed by α -interferon in the treatment of chronic hepatitis B. HBV DNA levels in more than 700 serial serum samples from 41 patients were determined by a sensitive and quantitative solution hybridization assay. Results were compared with HBV DNA polymerase (DNAp) activity and hepatitis B e antigen (HBeAg) in 21 untreated controls and 20 treated patients. Among treated patients, the mean pretherapy HBV DNA values were higher in nonresponders than in responders. During prednisone treatment, DNA levels increased an average of 2.1-fold in responders and 1.4-fold in nonresponders. During the 2-week rest interval between prednisone and interferon, DNA values fell an average of 57% in responders. In contrast, the mean DNA values in nonresponders did not change during the same interval. This early distinction between responders and nonresponders was not apparent from DNAp or HBeAg results. During interferon treatment, HBV DNA became undetectable in responders and remained negative during a 1-year follow-up. DNA in nonresponders declined to 14% of baseline during interferon treatment but increased to pretherapy levels after treatment. DNAp values generally paralleled HBV DNA values, but DNAp activity showed more variability and lower sensitivity than did the hybridization assay results. HBeAg values varied independently of HBV DNA and DNAp with a much delayed decline in responders. These results indicate that HBV DNA, when measured quantitatively by a sensitive solution hybridization assay, is an early predictor of the effects of antiviral agents on replication.  相似文献   
34.
CD16, the type III receptor for IgG, is expressed on neutrophils, natural killer cells, and some T lymphocytes, mast cells, and activated monocytes but not on cells of the B-lymphocyte lineage including plasma cells. It is also produced in a soluble form found in serum. We analyzed sera from 165 multiple-myeloma patients, 29 patients with monoclonal gammopathies of unknown significance, and 20 normal disease-free donors. We found that the level of soluble CD16 was significantly decreased in sera from patients with multiple myeloma compared to sera from healthy and monoclonal gammopathies of unknown significance donors (P=0.0001). In addition, a stage-dependent decrease in soluble CD16 was observed, with a highly significant difference (P=0.004) between stage I and stage II+III myeloma patients. The correlation between the myeloma stage and the serum level of soluble CD16, which is related to the host response, was found to be more sensitive than that of 2-microglobulin, which reflects the tumor burden. The concomitant evaluation of the serum levels of these two markers allows better staging and therefore has a more precise prognostic value.  相似文献   
35.
Summary Southern blot analysis of AvaI-digested total cellular DNA from the interfertile species Chlamydomonas eugametos and Chlamydomonas moewusii with a coxI mitochondrial gene probe from Chlamydomonas reinhardtii revealed single hybridizing fragments of 5.0 and 3.5 kb, respectively. The transmission of these mitochondrial DNA physical markers along with that of chloroplast genetic markers for resistance to streptomycin and resistance to erythromycin was studied in the fourth backcrosses of F1 hybrids to one or the other parent. Viability in these backcrosses is high in contrast to the cross C. eugametos x C. moewusii and its reciprocal which are associated with considerable meiotic product lethality. The resulting zygospores were found to transmit the mitochondrial and chloroplast genome markers uniparentally or preferentially from the mating-type-plus parent. Thus the species pair C. eugametos and C. moewusii differs from the pair Chlamydomonas reinhardtii and Chlamydomonas smithii in which mitochondrial genome markers are transmitted uniparentally by the mating-type minus parent, while the chloroplast genome markers are transmitted uniparentally by the opposite parental mating-type (Boynton et al. 1987).  相似文献   
36.
Intraductal papillary growth of mucin producting hypersecreting, columnar cells characterizes a group of rare pancreatic exocrine neoplasms which we propose to call intraductal papillary-mucinous tumors (IPMT). We analysed the histopathology of 26 IPMT in relation to gastro-enteropancreatic marker expression, genetic changes and biology. Four IPMT showing only mild dysplasia were considered to be adenomas. Nine tumours displayed moderate dysplasia and were regarded as borderline. Severe dysplasia-carcinoma in situ changes were found in 13 IPMT which were therefore classified as intraductal carcinomas. Six of these carcinomas were frankly invasive and two of these had lymph node metastases. The invasive component resembled mucinous noncystic carcinoma in all but one tumour which showed a ductal invasion pattern. Immunohistochemically, an intestinal marker type was found in most carcinomas, while gastric type differentiation prevailed among adenomas or borderline tumours. K-ras mutations (seven at codon 12 and one at codon 13) were found in 31% of IPMT (2 adenomas, 1 borderline, 5 carcinomas). Nuclear p53 overexpression was detected in 31% of IPMT (6 carcinomas and 2 borderline IPMT) and correlated with p53 mutations (one at exon 8 and the other at exon 5) in two carcinomas. p53 abnormalities were unrelated to K-ras mutation. c-erbB-2 overexpression was observed in 65% of IPMT, with various grades of dysplasia. Twenty-two of 24 patients are alive and well after a mean post-operative follow-up of 41 months. Only two patients, both with invasive cancer at the time of surgery, died of tumour disease. It is concluded that pancreatic IPMT encompass neoplasms which, in general, have a favorable prognosis, but are heterogeneous in regard to grade of dysplasia and marker expression. Adenoma, borderline tumour, intraductal carcinoma and invasive carcinoma can be differentiated. p53 changes but not K-ras mutation or c-erbB-2 overexpression are related to the grade of malignancy. Most IPMT differ in histological structure, marker expression and behaviour from ductal adenocarcinoma.  相似文献   
37.
38.
Genotyping with flanking DNA markers was used to ascertain Treacher Collins Franceschetti syndrome (TCOF1) in a subject affected by tetralogy of Fallot and cryptorchidism. The proband's family consisted of a father and sister who were affected by the disease, and a healthy mother. Since cardiac malformation and cryptorchidism have been associated with the TCOF1 syndrome, the proband was suspected to be a carrier of the mutated gene. Microsatellite markers D5S527, SPARC and D5S519, which previously mapped the TCOF1 gene within a 2.1-cM interval on chromosome 5 (5q32–33.1), were used to follow the transmission of the TCOf 1 mutated locus. Flanking markers D5S519 and D5S527 were informative and enabled us to exclude inheritance of a TCOF1 mutation to the proband, while showing that cardiac malformation and cryptorchidism were unrelated in mis patient.  相似文献   
39.
Two polymeric autosomal loci, Ten1 and Ten2, regulate thymus enlargement in BUF/Mna (B) rats. Previously, we mapped Ten1 on chromosome (Chr) 1 to a 20 cM region between Myl2 and D1Mgh11, and Ten2 on Chr 13. To further characterize the precise position of Ten1, 34 and 37 microsatellite markers, that have a polymorphism between the B and WYK (W) and between the B and MITE (M) strains, were used for linkage analysis of thymus enlargement in 105 (WBF1 x B) blackcross (BC) and 78 (B x BMF1) BC rats, respectively. Our data showed that the D1Rat168, D1Rat112, D1Rat323, D1Got186, D1Got187 and D1Got188 markers each gave a peak logarithm of odds (LOD) score of 10.68 for linkage to the thymus ratio in (WBF1 x B) BC rats, and that the D1Rat168, D1Rat197, D1Got184, D1Got186 and D1Got188 markers each gave a peak LOD score of 7.82 in (B x BMF1) BC rats. The two LOD score peaks are coincident in the position of the rat genetic map. All of the markers mentioned above are located in the region between Igf2 and D1Mgh11, in which synteny is conserved with human 11q15.5 and the distal end of mouse Chr 7 or with human 11q13 and the proximal end of mouse Chr 19. Genes existing in these regions are discussed as candidate genes for Ten1.  相似文献   
40.
肺癌患者血清TSGF、CEA、CYFRA21—1和NSE水平的临床价值   总被引:1,自引:2,他引:1  
目的:探讨血清TSGF、CEA、CYFRA21-1和NSE水平的临床价值。方法:采用放射免疫分析测定了179例肺癌、48例肺良性病变和51例正常对照组的血清TSGF、CEA、CYFRA21-1和NSE的水平。结果:在NSCLC中,37例I~II期鳞癌血清中TSGF、CEA和NSE水平与肺良性病变无明显差异(P均>0.05),32例I~II期腺癌血清中NSE也与肺良性病变无明显差异(P>0.05);其余,NSCLC和SCLC血清中TSGF、CEA、CY-FRA21-1和NSE水平明显增高,均与肺良性病变具有明显差异(P<0.05~0.01),从总体而言,随着病变的严重程度增加,肺癌标志物水平也增高。51例正常对照组血清TSGF、CEA、CYFRA21-1和NSE水平分别为(64.1±14.8)U/ml,(3.51±1.1)ng/ml,(2.6±1.4)ng/ml和(5.1±3.6)ng/ml。结论:肺癌的诊断中,以血清CY-FRA21-1测定为最佳,其次为TSGF和CEA,最差NSE,故肺癌标志物的联检是诊断肺癌的最佳选择。  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