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   5412篇
  免费   316篇
  国内免费   52篇
耳鼻咽喉   51篇
儿科学   93篇
妇产科学   277篇
基础医学   563篇
口腔科学   92篇
临床医学   557篇
内科学   1202篇
皮肤病学   59篇
神经病学   413篇
特种医学   177篇
外科学   681篇
综合类   96篇
一般理论   2篇
预防医学   250篇
眼科学   304篇
药学   466篇
中国医学   30篇
肿瘤学   467篇
  2023年   26篇
  2022年   74篇
  2021年   155篇
  2020年   60篇
  2019年   118篇
  2018年   165篇
  2017年   100篇
  2016年   120篇
  2015年   160篇
  2014年   199篇
  2013年   257篇
  2012年   416篇
  2011年   383篇
  2010年   287篇
  2009年   217篇
  2008年   308篇
  2007年   326篇
  2006年   328篇
  2005年   283篇
  2004年   244篇
  2003年   210篇
  2002年   191篇
  2001年   166篇
  2000年   161篇
  1999年   132篇
  1998年   27篇
  1997年   38篇
  1996年   27篇
  1995年   26篇
  1994年   25篇
  1993年   14篇
  1992年   79篇
  1991年   55篇
  1990年   66篇
  1989年   40篇
  1988年   27篇
  1987年   39篇
  1986年   27篇
  1985年   26篇
  1984年   18篇
  1983年   9篇
  1981年   9篇
  1980年   16篇
  1979年   20篇
  1978年   16篇
  1977年   9篇
  1975年   10篇
  1973年   8篇
  1972年   12篇
  1971年   8篇
排序方式: 共有5780条查询结果,搜索用时 0 毫秒
11.
To determine whether there are specific cytologic features associated with primary Sj?gren's syndrome (SS), the authors evaluated impression cytology specimens from three conjunctival sites (temporal bulbar [TB], inferior bulbar [IB], and inferior tarsal [IT]) from 38 SS eyes, 34 eyes of aqueous tear-deficient patients without SS, 35 eyes of seborrheic blepharitis patients, and 17 eyes of normal controls in a masked fashion. The following features were observed more frequently in SS eyes than in the eyes of the other groups: squamous metaplasia of the TB and IB (P less than 0.05), extensive (greater than 75%) goblet cell loss of the TB (P less than 0.05), mucous aggregates of the bulbar conjunctiva (P less than 0.05), and inflammatory cells intercalated with epithelial cells on the IT conjunctiva (P less than 0.06). The conjunctival inflammatory cell infiltrate correlated with the presence of extensive squamous metaplasia (P less than 0.01) in SS specimens. The inflammatory cells on the IT conjunctival epithelium were found to consist predominantly of T-lymphocytes by immunofluorescent staining of cytologic specimens from six eyes. Based on these findings, the authors speculated that conjunctival squamous metaplasia, in addition to aqueous tear deficiency, may be due to primary involvement of the dysfunctional immune system of SS.  相似文献   
12.
Gene amplification allows transformed cells to overexpress specific genes and gain a survival advantage. For this reason, cloning and characterization of amplified genes can improve our understanding of the biology of transformed cells. The techniques of in-gel renaturation and chromosome microdissection can enrich for amplified DNA sequences, but both are labor intensive and have other drawbacks. We have developed an alternative strategy of enriching for amplified DNA sequences that involves two-directional agarose gel electrophoresis of extrachromosomal circular DNA. Extrachromosomal circles can be detected with repetitive DNA probes and can be used to produce DNA probes suitable for fluorescence in situ hybridization for location of genomic origin. The ability to enrich for amplified DNA without specialized equipment or transformed cell metaphases should prove useful in the search for new genes which are important in tumor cell progression.  相似文献   
13.
We present two case studies, one of generalized chorea and one of hemichorea, both after severe hypoglycemia episodes. Both cases showed hyperperfusion in their SPECT scans. The MRI and SPECT findings serve as clues regarding the role of basal ganglion dysfunction associated with chorea.  相似文献   
14.
The in vitro DNA amplification technique of polymerase chain reaction was used to evaluate the possible presence of human papillomavirus (HPV) in small cell carcinoma of the uterine cervix. None of the 12 cases examined contain detectable amounts of either HPV type 16, 18, 31, or 33 DNA. On the other hand, HPV types 16 and 18 DNA were found in 14 (93.3%) and 9 (60.0%) of 25 invasive cervical squamous carcinoma tissues. The results seem to suggest that these types of HPV are not present or are present in extremely small quantities in cervical small cell carcinoma. Such an absence of HPV DNA makes it unlikely that these types of HPV play any etiological role in the pathogenesis of cervical small cell carcinoma.  相似文献   
15.
To investigate the association between pre-walking locomotor strategies and psychomotor developments in children with mental retardation (MR), 50 children with non-specific MR were included in this study. There were 29 boys and 21 girls, 96% of whom had moderate to severe MR. They were followed from 4-53 months to 25-99 months of age, and their follow-up periods ranged from 10 to 48 months (mean 30 months). According to the pre-walking locomotor strategies, these children were categorized into three groups: the crawling group (n = 34) who used crawling or creeping as their main locomotion pattern before independent walking; the shuffling group (n = 9) who used shuffling prior to independent walking; and the direct-walking group (n = 7) who did not have any other locomotor strategies except rolling. In almost all motor developmental milestones, children in the direct-walking group developed earlier than those in the crawling and shuffling groups. Children in the crawling group had more advanced developments than those in the shuffling group. The difference in the mean ratio developmental quotients of the Bayley Mental Scale among the three groups was not significant. The present study showed that crawling may not be a necessary prerequisite for early ambulation or better cognitive function in MR children.  相似文献   
16.
Delayed traumatic intracerebral hemorrhage: a study of prognostic factors.   总被引:4,自引:0,他引:4  
S H Tseng 《台湾医志》1992,91(6):585-589
Experience in the management of 32 patients with delayed traumatic intracerebral hemorrhage (DTICH) is presented with emphasis on the incidence, clinical significance and factors affecting the outcome. The incidence was 1.4% of all hospitalized head-injury patients, or 5.9% of only those patients with neurologic signs or abnormal findings on computed tomography (CT) identified on admission. After an injury, every patient had an immediate CT scan to diagnose intracranial pathology. Initially, nine patients underwent a craniotomy for intracranial hematomas, and 23 patients had nonoperative treatment. CT follow-up was carried out in 10 patients due to clinical deterioration and on 22 patients due to failure to recover neurologically. The delayed hemorrhage was found after a time interval varying from seven hours to 10 days (average, three days and seven hours). Six patients underwent operations for DTICH, and 26 were treated conservatively. Twenty-four patients (75%) were functional (good or moderately disabled condition) after one year of follow-up treatment, as measured on the Glasgow Outcome Scale. The mortality was 16%. The patients were predicted to have a poor prognosis if associated with an earlier occurrence, the hematoma was large, the patient had a poor Glasgow Coma Scale score at the time of CT follow-up, clinical deterioration was noted, or partial or complete effacement of the suprachiasmatic cistern was noted on the CT scan. The results indicate that the prognosis of DTICH is not as poor as it was previously thought to be, and the factors affecting the outcome in this study seem to justify a more vigilant approach.  相似文献   
17.
Hyperoxaluria is frequently seen in patients with inflammatory bowel disease, or after resection of the ileum. It is assumed to be responsible for the development of nephrolithiasis, nephrocalcinosis (oxalate nephrosis) and progressive renal impairment in these patients. Steatorrhea may aggravate the severity of hyperoxaluria. A 60-year-old male underwent massive resection of the jejunum and ileum 10 years prior to admission, due to strangulation of the small bowel, with occlusion of the superior mesenteric artery. He remained well except for steatorrhea which developed two-and-a-half years prior to admission, when microhematuria, proteinuria and oxaluria developed progressively. Since that time, the nephrolithiasis, nephrocalcinosis and renal failure have continued to worsen despite therapy with oxalate restriction and oxalate-binding agents. A renal biopsy, performed late in the clinical course, showed severe changes in the renal parenchyma. The decline in renal function proved irreversible. The unusual metabolic consequences of massive resection of the small intestine and their mechanisms are discussed.  相似文献   
18.
PURPOSE: Various types of temporary implants have been introduced to serve as orthodontic anchorage. The hypothesis of this study is that microimplants of 1.2 mm diameter can be used as orthodontic anchors, and that their success is related to their length. The aim of this study is to determine the incidence of anchor retention after orthodontic force application for moving teeth, and to determine the relationship of microimplant length to retention rate. METHODS: Fifty-nine microimplants (diameter: 1.2 mm) were placed in 29 patients as orthodontic anchorages. After 2 weeks of microimplant placement, a force of 100 to 200 g was loaded with an elastometric chain or NiTi coil spring. Risk factors were characterized as to why a microimplant may fail, and Fisher's exact test was used for statistical analysis. RESULTS: Nine microimplants were removed and the overall success rate was 84.7%. Exploring the causes for failure, we found significant differences between the length of microimplants and success rate; 6 mm was 72.2% and 8 mm was 90.2%. CONCLUSIONS: The results suggest that microimplants are suited as an alternative orthodontic anchorage. We recommend that 8-mm microimplants are preferable to 6-mm.  相似文献   
19.
20.
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