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   11591篇
  免费   834篇
  国内免费   27篇
耳鼻咽喉   118篇
儿科学   238篇
妇产科学   267篇
基础医学   1416篇
口腔科学   171篇
临床医学   1475篇
内科学   2474篇
皮肤病学   125篇
神经病学   966篇
特种医学   446篇
外科学   1961篇
综合类   130篇
一般理论   26篇
预防医学   909篇
眼科学   178篇
药学   910篇
中国医学   8篇
肿瘤学   634篇
  2024年   11篇
  2023年   116篇
  2022年   190篇
  2021年   439篇
  2020年   238篇
  2019年   430篇
  2018年   480篇
  2017年   320篇
  2016年   376篇
  2015年   347篇
  2014年   542篇
  2013年   627篇
  2012年   957篇
  2011年   1032篇
  2010年   579篇
  2009年   495篇
  2008年   783篇
  2007年   790篇
  2006年   711篇
  2005年   705篇
  2004年   667篇
  2003年   529篇
  2002年   497篇
  2001年   66篇
  2000年   54篇
  1999年   67篇
  1998年   83篇
  1997年   67篇
  1996年   41篇
  1995年   28篇
  1994年   44篇
  1993年   24篇
  1992年   14篇
  1991年   6篇
  1990年   16篇
  1989年   6篇
  1988年   3篇
  1987年   4篇
  1986年   3篇
  1984年   10篇
  1983年   4篇
  1982年   8篇
  1981年   4篇
  1980年   5篇
  1979年   4篇
  1978年   6篇
  1977年   3篇
  1965年   2篇
  1964年   2篇
  1963年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
OBJECTIVE: To examine psychosocial predictors of distress (mood disturbance, perceived stress, caregiver burden) in parents of children undergoing stem cell or bone marrow transplantation (BMT). METHOD: Measures of prior illness experiences, premorbid child behavior problems, family environment, social support, and parental coping behavior were obtained from the resident parents of 151 children prior to the children's admission for BMT. Parents subsequently completed assessments of their mood disturbance, perceived stress, and caregiving burden on a weekly basis through week +6 post-BMT, and then monthly through month +6 post-BMT. RESULTS: Significant changes were observed in parental distress across the course of BMT. After correcting for demographic and medical factors, several significant predictors of parental distress trajectories were identified, including prior parent and patient illness-related distress, premorbid child internalizing behavior problems, the family relationship dimensions of the family environment, and parental avoidant coping behaviors. Multivariable models were developed using a hierarchical modeling approach. The best-fit model accounted for approximately 50% of the variance in parental global distress. CONCLUSIONS: Subgroups of parents at higher risk for increased distress during the acute phase of transplant have been identified. These findings can help target parents who may be in greater need of intervention aimed at reducing transplant-related distress.  相似文献   
42.
Group B streptococci (GBS) usually behave as commensal organisms that asymptomatically colonize the gastrointestinal and urogenital tracts of adults. However, GBS are also pathogens and the leading bacterial cause of life-threatening invasive disease in neonates. While the events leading to transmission and disease in neonates remain unclear, GBS carriage and level of colonization in the mother have been shown to be significant risk factors associated with invasive infection. Surface antigens represent ideal vaccine targets for eliciting antibodies that can act as opsonins and/or inhibit colonization and invasion. Using a genetic screen for exported proteins in GBS, we identified a gene, designated lrrG, that encodes a novel LPXTG anchored surface antigen containing leucine-rich repeat (LRR) motifs found in bacterial invasins and other members of the LRR protein family. Southern blotting showed that lrrG was present in all GBS strains tested, representing the nine serotypes, and revealed the presence of an lrrG homologue in Streptococcus pyogenes. Recombinant LrrG protein was shown in vitro to adhere to epithelial cells in a dose-dependent manner, suggesting that it may function as an adhesion factor in GBS. More importantly, immunization with recombinant LrrG elicited a strong immunoglobulin G response in CBA/ca mice and protected against lethal challenge with virulent GBS. The data presented in this report suggest that this conserved protein is a highly promising candidate antigen for use in a GBS vaccine.  相似文献   
43.
IMMUNOHISTOCHEMICAL DISTRIBUTION OF CANNABINOID CB 1 RECEPTOR IN THE RAT CENTRAL NERVOUS SYSTEM@邹冈  相似文献   
44.
Teleradiology allows contemporaneous interpretation of imaging exams performed at some distance from the interpreting radiologist. The transmitted images are usually static. However, there is benefit to real-time review of full-motion ultrasound (US) exams as they are performed. Telesonography is transmission of full-motion sonographic data to a remote site. We hypothesize that US exams, read after having been compressed utilizing Motion Picture Experts Group version 4 (MPEG-4) compression scheme, transmitted over the Internet as streaming multimedia, decompressed, and displayed, are equivalent in diagnostic accuracy to reading the examinations locally. MPEG-4 uses variable compression on each image frame to achieve a constant output bit rate. With less compression, the bit rate rises, and the only way the encoder can contain bit rate within the set bandwidth is by lowering frame rate or reducing image quality. We review the relevant technologies and industry standard components that will enable low-cost telesonography.  相似文献   
45.
Staphylococcus epidermidis has been reported to bind to a number of host cell extracellular matrix proteins, including fibronectin. Here we report the identification of a fibronectin-binding protein from S. epidermidis. A phage display library of S. epidermidis genomic DNA was constructed and panned against immobilized fibronectin. A number of phagemid clones containing overlapping inserts were identified, and one of these clones, pSE109FN, contained a 1.4-kb insert. Phage pSE109FN was found to bind to fibronectin but not to collagen, fibrinogen, laminin, or vitronectin. However, pSE109FN also bound to heparin, hyaluronate, and plasminogen, although to a lesser extent than it bound to fibronectin. Analysis of The Institute for Genomic Research S. epidermidis genome sequence database revealed a 1.85-kb region within a putative 30.5-kb open reading frame, to which the overlapping DNA inserts contained within the fibronectin-binding phagemids mapped. We have designated the gene encoding the fibronectin-binding domain embp. A recombinant protein, Embp32, which encompassed the fibronectin-binding domain of Embp, blocked the binding of S. epidermidis, but not the binding of Staphylococcus aureus, to fibronectin. In contrast, a recombinant protein, FnBPB[D1-D4], spanning the fibronectin-binding domain of the S. aureus fibronectin-binding protein FnBPB, blocked binding of S. aureus to fibronectin but had a negligible effect on the binding of S. epidermidis.  相似文献   
46.
BACKGROUND: The role of CD8+ T cells in the immune response to airway challenge with an allergen is poorly understood. OBJECTIVE: The aim of this study was to test the hypothesis that resident naive CD8+ T cells modulate the magnitude of CD4+ T cell-dependent allergic airway responses. METHODS: Cervical lymph node CD4+ T cells (2 x 10(6)) were harvested from ovalbumin (OVA)- or sham-sensitized rats and injected intraperitoneally into naive Brown Norway recipients. The recipients were treated with a CD8alpha mAb (OX-8) to deplete the resident CD8+ T cells (n = 12) or mouse ascites (n = 12). Two days after adoptive transfer, the recipient animals were OVA challenged, lung resistance was measured for 8 hours, and bronchoalveolar lavage (BAL) was performed. RESULTS: After OVA challenge, primed CD4-transferred CD8-depleted rats had larger early airway responses and late airway responses compared with primed CD4-transferred CD8-nondepleted rats (early airway responses: 158.6% +/- 19.2% vs 115.7% +/- 5.9%, P < .05; late airway responses: 8.5% +/- 1.7% vs 4.4% +/- 0.9%, P < .05). BAL eosinophilia was also greater (4.67% +/- 0.45% vs 2.34 +/- 0.26%, P < .01). The cells in BAL fluid expressing IL-4 mRNA were not significantly changed by CD8 depletion, but IL-5 mRNA+ cells were higher in number, and IFN-gamma mRNA+ cells were fewer in the CD8-depleted group. CONCLUSIONS: Resident CD8+ T cells downregulate the late allergic response and airway inflammation evoked by CD4+ T-cell transfers in Brown Norway rats. This downregulation does not require antigen priming.  相似文献   
47.
Huang Q  Chu PG  Lau SK  Weiss LM 《Human pathology》2004,35(6):769-773
We report a case of an 83-year-old man with a high-grade carcinoma of the urinary bladder who underwent cystoprostatectomy. The invasive carcinoma showed mixed, morphologically distinct patterns consisting of conventional high-grade urothelial carcinoma, glandular differentiation resembling enteric type adenocarcinoma, and acinar/tubular type differentiation, morphologically similar to Gleason grade 3 prostatic adenocarcinoma. Immunohistochemical studies revealed the acinar/tubular component of the tumor to be negative for prostate-specific antigen and prostatic acid phosphatase, but positive for cytokeratin 7, cytokeratin 20, high molecular weight cytokeratin (34 beta E12), and thrombomodulin, consistent with origin from the bladder rather than the prostate. Although bladder carcinomas composed of mixed morphologic patterns are not uncommon, to our knowledge, the presence of acinar/tubular type features simulating prostatic adenocarcinoma in such tumors has not been described elsewhere.  相似文献   
48.
An intracellular organism was isolated from the tissues of an Oriental white-backed vulture (Gyps bengalensis) in chicken embryo fibroblast cell cultures. Biochemical and physical properties, ultrastructural features, and 16S ribosomal DNA sequencing classified this organism as a new taxon of mycoplasma, for which the name "Mycoplasma vulturii" is proposed.  相似文献   
49.
Paraffin-section immunohistochemical analysis was performed using a monoclonal antibody against CD163 to evaluate the antibody's usefulness in identifying cells of monocyte/macrophage lineage in normal and neoplastic conditions. Normal human tissue samples and samples from 211 hematopoietic disorders and 115 nonhematopoietic neoplasms were examined. The distribution of KP1 and PG-M1, monoclonal antibodies to the macrophage-associated CD68 antigen, also were evaluated for comparison. CD163 immunoreactivity was observed in resident macrophages of all normal tissue samples except splenic white pulp macrophages and germinal center tingible body macrophages. Among hematopoietic disorders and nonhematopoietic neoplasms, CD163 expression was restricted largely to cases of chronic myelomonocytic leukemia, histiocytic sarcoma, sinus histiocytosis with massive lymphadenopathy, and littoral cell angioma. Acute myeloid leukemias (AMLs) with monocytic differentiation were CD163- with the exception of 1 case of acute monoblastic leukemia. Most myeloid sarcomas also were CD163-. Compared with the CD68 antibodies, CD163 demonstrated greater specificity as a marker of disorders of monocyte/macrophage origin. However, immunohistochemical evaluation of CD163 expression does not seem to be a sensitive means of determining monocytic differentiation in AMLs in paraffin sections or establishing a diagnosis of myeloid sarcoma.  相似文献   
50.
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