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   913篇
  免费   96篇
  国内免费   7篇
耳鼻咽喉   7篇
儿科学   48篇
妇产科学   9篇
基础医学   120篇
口腔科学   20篇
临床医学   76篇
内科学   179篇
皮肤病学   9篇
神经病学   24篇
特种医学   96篇
外科学   188篇
综合类   77篇
预防医学   89篇
眼科学   8篇
药学   27篇
肿瘤学   39篇
  2022年   12篇
  2021年   15篇
  2020年   13篇
  2019年   9篇
  2018年   19篇
  2017年   10篇
  2016年   20篇
  2015年   29篇
  2014年   23篇
  2013年   42篇
  2012年   27篇
  2011年   39篇
  2010年   26篇
  2009年   44篇
  2008年   23篇
  2007年   39篇
  2006年   49篇
  2005年   19篇
  2004年   21篇
  2003年   12篇
  2002年   13篇
  2001年   14篇
  2000年   15篇
  1999年   22篇
  1998年   49篇
  1997年   32篇
  1996年   41篇
  1995年   20篇
  1994年   18篇
  1993年   23篇
  1992年   6篇
  1991年   22篇
  1990年   8篇
  1989年   14篇
  1988年   29篇
  1987年   21篇
  1986年   13篇
  1985年   26篇
  1984年   17篇
  1983年   11篇
  1982年   8篇
  1981年   7篇
  1980年   7篇
  1979年   13篇
  1978年   9篇
  1977年   6篇
  1976年   10篇
  1975年   8篇
  1972年   7篇
  1970年   8篇
排序方式: 共有1016条查询结果,搜索用时 15 毫秒
11.
The aims of this work were to measure the accuracy of one continuous speech recognition product and dependence on the speaker's gender and status as a native or nonnative English speaker, and evaluate the product's potential for routine use in transcribing radiology reports. IBM MedSpeak/Radiology software, version 1.1 was evaluated by 6 speakers. Two were nonnative English speakers, and 3 were men. Each speaker dictated a set of 12 reports. The reports included neurologic and body imaging examinations performed with 6 different modalities. The dictated and original report texts were compared, and error rates for overall, significant, and subtle significant errors were computed. Error rate dependence on modality, native English speaker status, and gender were evaluated by performing ttests. The overall error rate was 10.3 +/- 3.3%. No difference in accuracy between men and women was found; however, significant differences were seen for overall and significant errors when comparing native and nonnative English speakers (P = .009 and P = .008, respectively). The speech recognition software is approximately 90% accurate, and while practical implementation issues (rather than accuracy) currently limit routine use of this product throughout a radiology practice, application in niche areas such as the emergency room currently is being pursued. This methodology provides a convenient way to compare the initial accuracy of different speech recognition products, and changes in accuracy over time, in a detailed and sensitive manner.  相似文献   
12.
Precursor lesions of ovarian epithelial malignancy   总被引:10,自引:0,他引:10  
Most ovarian carcinomas arise from the mesothelial surface lining of the ovaries, or from invaginations of this lining into the superficial ovarian cortex to form cortical inclusion cysts. The native ovarian surface mesothelium is of an 'uncommitted' phenotype, and has potential to modulate to epithelial or mesenchymal phenotypes in response to signals such as those associated with ovulation. The exposure of the mesothelial lining of an inclusion cyst to the ovarian stromal microenvironment may be responsible for the phenotypic change to Müllerian epithelium so commonly seen in these cysts. Müllerian metaplasia is usually to a serous phenotype, and it is possible that undefined molecular events occurring in an inclusion cyst that has undergone Müllerian metaplasia may initiate neoplastic change in these cysts. This may be the developmental pathway of most invasive serous carcinomas. Occasional rare cases of ovarian intraepithelial neoplasia, manifested by epithelial atypia in an inclusion cyst or on the surface epithelium without invasive carcinoma, are identified histologically. Serous borderline tumours represent a separate category and in most cases probably do not progress to frank carcinoma. Mucinous carcinomas may in some cases have arisen from pre-existing benign and borderline mucinous tumours. Endometriosis of the ovary is associated with genetic abnormalities and is frequently found in association with clear cell and endometrioid carcinomas, suggesting that in many cases these latter two types of carcinoma may have arisen directly from endometriotic deposits. Ovaries removed prophylactically from women with a family history of ovarian carcinoma or with a mutation in one of the genes predisposing to ovarian carcinoma should be processed in their entirety, and examined closely not just for obviously neoplastic lesions, but also for more subtle morphological abnormalities of the surface epithelium or the epithelium lining cortical inclusion cysts.  相似文献   
13.
Acute porphyria is rare in orientals. We describe a Chinese woman with recurrent generalised tonic-clonic seizures and abdominal pain. Genomic DNA studies identified a heterozygous base substitution from guanine to adenine at nucleotide position 503, resulting in substitution of arginine by histidine at position 168 of the protein (R168H). This genetic abnormality is similar to the mutation reported in Caucasians with variegate porphyria. To the best of our knowledge, this is the first report in the English literature a Chinese patient with variegate porphyria with an identifiable mutation. A brief review of porphyria is presented.  相似文献   
14.
The Dunning H rat prostate tumor (R3327H) is a widely used experimental model of human prostatic adenocarcinoma (CaP). The Dunning H tumor has been characterized as androgen-sensitive, androgen-receptor (AR) positive, prostate-specific antigen and prostatic acid phosphatase (PAP) positive. To date, the tumor has been maintained by serial passage in vivo because of the lack of an in vitro cell line that retains the characteristics of the in vivo tumor. The objective of the present study was to establish a propagable cell line from R3327H adenocarcinoma that maintained androgen sensitivity and expression of AR, PSA and PAP. Tissue harvested from an in vivo R3327H tumor was dissociated with collagenase and placed into Richter's improved media (with supplements). A cytokeratin-positive epithelial cell line (HUNC- E) and a vimentin-positive stromal cell line (HUNC-S) were generated from the primary culture, subcultured continuously for >300 days, and passaged >50 times. Survival of the HUNC-E cell line in vitro depended on several media supplements, including nicotinamide, insulin, transferrin, selenium and epidermal growth factor (EGF). HUNC-E cells expressed AR and produced PSA and PAP throughout the culture period, as confirmed by immunocytochemistry and Western blot analyses. Addition of 14 nM testosterone (T) or dihydrotestosterone (DHT) to HUNC-E cells, stimulated DNA synthesis as well as anchorage-independent growth and PSA production, which demonstrated the androgen-sensitive nature of the cells in vitro. When HUNC-E and HUNC-S cells were combined in a 3:1 ratio and introduced subcutaneously into syngeneic male hosts, tumors formed in 2/3 animals with an average latency of 7 months. RT-PCR and immunocytochemical characterization of the HUNC cell lines revealed that the cells expressed several growth factors and their cognate receptors, including HGF, TGF-alpha and the TGF-betas, indicating the establishment of potential autocrine loops in the neoplastic cells. The HUNC-E and HUNC-S CaP cell lines, which retain the characteristics of the epithelial and stromal components of the in vivo R3327H tumor, will allow a more thorough and informative molecular and biological analysis of prostatic adenocarcinoma.   相似文献   
15.
Contamination with Bacillus anthracis spores is a serious environmental hazard in textile mills where imported raw goat hair is used. While a plant in which haircloth had been produced was being converted for synthetic fiber production, formaldehyde vapor was introduced into the sealed buildings at a final concentration of 1.38 to 1.62 ml/cu ft (18 to 21 mg/liter). Pretreatment rates of surface contamination with anthrax spores were 37% in the initial processing area and 12.5% in the spinning area. Contamination dropped to 8% and 1% immediately after formaldehyde treatment, and to 1% and 0 six months later. Test suspensions of B anthracis spores placed in the plant before it was treated showed 99.998% loss of viability and recovery of all bacterial flora had been reduced tenfold to 100-fold after treatment.  相似文献   
16.
17.
18.
Young  JC; Bruno  E; Luens  KM; Wu  S; Backer  M; Murray  LJ 《Blood》1996,88(5):1619-1631
Thrombopoietin (TPO) or MpI ligand is known to stimulate megakaryocyte (MK) proliferation and differentiation. To identify the earliest human hematopoietic cells on which TPO acts, we cultured single CD34+Thy- 1+Lin- adult bone marrow cells in the presence of TPO alone, with TPO and interleukin-3 (IL-3), or with TPO and c-kit ligand (KL) in the presence of a murine stromal cell line (Sys1). Two distinct growth morphologies were observed: expansion of up to 200 blast cells with subsequent differentiation to large refractile CD41b+ MKs within 3 weeks or expansion to 200-10,000 blast cells, up to 25% of which expressed CD34. The latter blast cell expansions occurred over a 3- to 6-week period without obvious MK differentiation. Morphological staining, analysis of surface marker expression, and colony formation analysis revealed that these populations consisted predominantly of cells committed to the myelomonocytic lineage. The addition of IL-3 to TPO-containing cultures increased the extent of proliferation of single cells, whereas addition of KL increased the percentage of CD34+ cells among the expanding cell populations. Production of multiple colony- forming unit-MK from single CD34+Thy-1+Lin- cells in the presence of TPO was also demonstrated. In limiting dilution assays of CD34+Lin- cells, TPO was found to increase the size and frequency of cobblestone areas at 4 weeks in stromal cultures in the presence of leukemia inhibitory factor and IL-6. In stroma-free cultures, TPO activated a quiescent CD34+Lin-Rhodamine 123lo subset of primitive hematopoietic progenitor cells into cycle, without loss of CD34 expression. These data demonstrate that TPO acts directly on and supports division of cells more primitive than those committed to the MK lineage.  相似文献   
19.
20.
Rotator cuff pathology is the most common shoulder problem seen by orthopedic surgeons. Rotator cuff muscle fatty infiltration and muscle atrophy are common in larger tears and are considered predicting factors for the prognosis of cuff repair. Clinically, MRI is the gold standard in determining fatty infiltration and muscle atrophy; however, analysis for MRI imaging is primarily qualitative in nature with the results lacking further validation. We have recently developed a mouse model of rotator cuff tears. The goal of this study is to quantify and verify rotator cuff muscle atrophy and fatty infiltration using high‐resolution MRI in our mouse model. The rotator cuff muscles were analyzed for fat using a triglyceride quantification assay (TQA), muscle volume was measured through water displacement (WD), and histology. The study revealed that MRI had a high correlation with fat as measured with histology and TQA (R2 = 098). MRI also correlated well with atrophy measured with WD and wet weight. This suggests that MRI is a reliable modality in evaluating the progression of fatty infiltration and muscle atrophy following rotator cuff tears in a small animal model. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 421–426, 2013  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