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   1184篇
  免费   101篇
  国内免费   1篇
耳鼻咽喉   11篇
儿科学   88篇
妇产科学   43篇
基础医学   216篇
口腔科学   15篇
临床医学   92篇
内科学   277篇
皮肤病学   18篇
神经病学   185篇
特种医学   35篇
外科学   86篇
综合类   2篇
预防医学   93篇
眼科学   15篇
药学   39篇
中国医学   1篇
肿瘤学   70篇
  2023年   5篇
  2022年   8篇
  2021年   25篇
  2020年   13篇
  2019年   27篇
  2018年   20篇
  2017年   22篇
  2016年   28篇
  2015年   18篇
  2014年   36篇
  2013年   35篇
  2012年   77篇
  2011年   65篇
  2010年   43篇
  2009年   34篇
  2008年   78篇
  2007年   75篇
  2006年   66篇
  2005年   79篇
  2004年   56篇
  2003年   50篇
  2002年   67篇
  2001年   54篇
  2000年   46篇
  1999年   29篇
  1998年   14篇
  1997年   10篇
  1996年   12篇
  1995年   15篇
  1994年   5篇
  1993年   11篇
  1992年   19篇
  1991年   13篇
  1990年   13篇
  1989年   6篇
  1988年   12篇
  1987年   14篇
  1986年   10篇
  1985年   13篇
  1984年   6篇
  1983年   9篇
  1981年   5篇
  1980年   6篇
  1979年   8篇
  1978年   4篇
  1977年   3篇
  1973年   5篇
  1972年   5篇
  1968年   2篇
  1967年   2篇
排序方式: 共有1286条查询结果,搜索用时 343 毫秒
1.
Our objectives were to study the prevalence, risk factors for carriage, and transmission dynamics of extended-spectrum-β-lactamase (ESBL)-producing Enterobacteriaceae (ESBLPE) in a national survey of cattle. This was a point prevalence study conducted from July to October 2013 in Israel. Stool samples were collected from 1,226 cows in 123 sections on 40 farms of all production types. ESBLPE were identified in 291 samples (23.7%): 287 contained Escherichia coli and 4 contained Klebsiella pneumoniae. The number of ESBLPE-positive cows was the highest in quarantine stations and on fattening farms and was the lowest on pasture farms (P = 0.03). The number of ESBLPE-positive cows was the lowest in sections containing adult cows (age, >25 months) and highest in sections containing calves (age, <4 months) (P < 0.001). Infrastructure variables that were significant risk factors for ESBLPE carriage included crowding, a lack of manure cleaning, and a lack of a cooling (P < 0.001 for each), all of which were more common in sections containing calves. Antimicrobial prophylaxis was given almost exclusively to calves and was associated with a high number of ESBLPE carriers (P < 0.001). The 287 E. coli isolates were typed into 106 repetitive extragenic palindromic (REP)-PCR types and mostly harbored blaCTX-M-1 or blaCTX-M-9 group genes. The isolates on the six farms with ≥15 isolates of ESBLPE were of 4 to 7 different REP-PCR types, with one dominant type being harbored by about half of the isolates. Fourteen types were identified on more than one farm, with only six of the farms being adjacent to each other. The prevalence of ESBLPE carriage is high in calves in cowsheds where the use of antimicrobial prophylaxis is common. ESBLPE disseminate within cowsheds mainly by clonal spread, with limited intercowshed transmission occurring.  相似文献   
2.
3.
4.
ImmunoCyt/uCyt is a fluorescent test combining three monoclonal antibodies. In this study, it has been tested as a complement to cytology in the detection of urothelial carcinoma in urine. It has been performed simultaneously with standard cytology and cystoscopy on 870 urine analyses from one hospital. In 136 cases, one or more bladder tumors were found. Overall sensitivity of cytology, ImmunoCyt/uCyt and combined analyses reached 29, 74 and 84%, respectively, and overall specificity was 98, 62 and 61%. The negative predictive value of cytology, ImmunoCyt/uCyt and both analyses was 88, 93 and 95%, respectively, and the positive predictive value was 70, 26 and 29%. The sensitivity of cytology for low malignant potential neoplasms, low- and high-grade papillary carcinomas was 6, 18 and 53%, while it reached 71, 79 and 93% when combined with ImmunoCyt/uCyt. The sensitivity of cytology for stages Ta, T1, T2 and over and Tis tumors was 12, 67, 47 and 50%, while it reached 78, 83, 79 and 100% when combined with ImmunoCyt/uCyt. In the absence of tumor on cystoscopy but with positive ImmunoCyt/uCyt, 18% of patients developed a tumor, 2-6 months later. Of the 109 cases diagnosed as suspicious for malignancy by cytology, a tumor was present in 30 cases and ImmunoCyt/uCyt was positive in 22 (73%) of them. In conclusion, ImmunoCyt/uCyt may be used to postpone cystoscopies in patients followed for bladder cancer and may help to save cytologist and pathologist screening time.  相似文献   
5.
6.
Autologous bone marrow transplantation (BMT) is a therapeutic option for the treatment of lymphohematopoietic malignancies and solid tumors. Despite the intensive cytoreductive therapy, however, the rates of tumor recurrence after autologous BMT remain unacceptably high. Current studies suggest that the administration of cyclosporine (CsA) disrupts the reconstitution of self-tolerance following autologous BMT leading to the induction of an autoimmune graft-versus-host disease (GVHD). Studies in a rat tumor model and preliminary clinical trials suggest that this autoimmune or autologous GVHD provides a significant antitumor effect. Moreover, the antitumor effect of autologous GVHD can be enhanced by administration of gamma-interferon, which upregulates the antigen recognized by the autoreactive effector cells of autologous GVHD. These studies indicate that the induction of an autoimmune GVHD after autologous BMT may be a promising immunotherapeutic approach for treatment of certain neoplastic diseases.  相似文献   
7.
The effects of anesthesia on otoacoustic emissions   总被引:4,自引:0,他引:4  
We have measured transient-evoked and distortion-product otoacoustic emissions (OAEs) in the chinchilla and compared them in the awake and anesthetized animal (using either ketamine or barbiturate agents). We report a significant increase in OAE amplitudes during anesthesia, particularly using ketamine. These effects are most evident for transient-evoked otoacoustic emissions (TEOAEs) as measured in the non-linear mode. Our data support the hypothesis that tonic activity levels in cochlear efferents may be reduced by anesthetic effects, either directly or indirectly (e.g., by general reductions in descending pathway activity), and that reduced cochlear efferent activity will result in the observed increase of OAE amplitudes.  相似文献   
8.
A diagnostic algorithm was developed to differentiate between human infections of West Nile virus (WNV) and St. Louis encephalitis virus (SLEV) using positive-to-negative (P/N) ratios derived from the immunoglobulin M capture enzyme-linked immunosorbent assay (MAC-ELISA). To validate this algorithm, we tested 1,418 serum and cerebrospinal fluid (CSF) samples from confirmed WNV and SLEV infections collected during the WNV epidemic of 2002 in the United States. WNV P/N-to-SLEV P/N ratios (W/S ratios) were calculated and used to identify the infecting virus. These results were compared to results from the plaque reduction neutralization test (PRNT), which is currently the standard assay used to discriminate between closely related flavivirus infections. If the W/S ratio was ≥1, the predictive value positive (PNP) for WNV was 97.8%, where 95% of flavivirus cases were due to WNV infection and only 3.7% of specimens would require PRNT to differentiate WNV from SLEV infection. Use of the W/S ratio as part of the testing algorithm to interpret MAC-ELISA results generates reportable probable cases quickly, alleviating the need for PRNT in most instances.  相似文献   
9.
10.
The virulence genotype profile and presence of a pathogenicity island(s) (PAI) were studied in 18 strains of F165-positive Escherichia coli originally isolated from diseased calves or piglets. On the basis of their adhesion phenotypes and genotypes, these extraintestinal pathogenic strains were classified into three groups. The F165 fimbrial complex consists of at least two serologically and genetically distinct fimbriae: F165(1) and F165(2). F165(1) is encoded by the foo operon (pap-like), and F165(2) is encoded by fot (sfa related). Strains in group 1 were foo and fot positive, strains in group 2 were foo and afa positive, and strains in group 3 were foo positive only. The strains were tested for the presence of virulence genes found mainly in extraintestinal pathogenic E. coli (ExPEC) strains. Although all the strains were positive for the papA variant encoding F11 fimbriae incD, traT, and papC, the prevalence of virulence genes commonly found in PAIs associated with ExPEC strains was highly variable, with strains of group 2 harboring most of the virulence genes tested. papG allele III was detected in all strains in group 1 and in one strain in group 3. All other strains were negative for the known alleles encoding PapG adhesins. The association of virulence genes with tRNA genes was characterized in these strains by using pulsed-field gel electrophoresis and DNA hybridization. The insertion site of the foo operon was found at the pheU tRNA locus in 16 of the 18 strains and at the selC tRNA locus in the other 2 strains. Furthermore, 8 of the 18 strains harbored a high-pathogenicity island which was inserted in either the asnT or the asnV/U tRNA locus. These results suggest the presence of one or more PAIs in septicemic strains from animals and the association of the foo operon with at least one of these islands. F165-positive strains share certain virulence traits with ExPEC, and most of them are pathogenic in piglets, as tested in experimental infections.  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