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   718篇
  免费   51篇
  国内免费   12篇
耳鼻咽喉   7篇
儿科学   32篇
妇产科学   55篇
基础医学   122篇
口腔科学   8篇
临床医学   60篇
内科学   167篇
皮肤病学   14篇
神经病学   17篇
特种医学   100篇
外科学   55篇
综合类   9篇
预防医学   21篇
眼科学   11篇
药学   44篇
中国医学   15篇
肿瘤学   44篇
  2020年   4篇
  2019年   8篇
  2018年   11篇
  2017年   14篇
  2016年   14篇
  2015年   18篇
  2014年   19篇
  2013年   31篇
  2012年   34篇
  2011年   21篇
  2010年   24篇
  2009年   15篇
  2008年   21篇
  2007年   25篇
  2006年   13篇
  2005年   25篇
  2004年   26篇
  2003年   31篇
  2002年   31篇
  2001年   31篇
  2000年   22篇
  1999年   17篇
  1998年   13篇
  1997年   14篇
  1996年   9篇
  1995年   8篇
  1994年   18篇
  1993年   22篇
  1992年   8篇
  1991年   11篇
  1990年   8篇
  1989年   27篇
  1988年   16篇
  1987年   25篇
  1986年   8篇
  1985年   15篇
  1984年   5篇
  1983年   6篇
  1981年   10篇
  1980年   7篇
  1979年   14篇
  1978年   7篇
  1977年   12篇
  1975年   5篇
  1973年   6篇
  1972年   3篇
  1971年   8篇
  1970年   4篇
  1965年   3篇
  1925年   4篇
排序方式: 共有781条查询结果,搜索用时 15 毫秒
1.
MR compatibility of Guglielmi detachable coils   总被引:6,自引:0,他引:6  
  相似文献   
2.
Several human organs are not capable of functional regeneration following a tissue defect and react with scar formation. In stem cell transplantation, undifferentiated or partly differentiated precursor cells are applied to defective tissue for therapeutic regeneration. After promising preclinical investigations, the transplantation of autologous stem cells for myocardial infarction treatment is being transferred to clinical use. Mesenchymal stem cells and endothelial precursor cells derived from the bone marrow or circulating blood as well as skeletal myoblasts are employed in clinical trials. Furthermore, indications for cell transplantation and delivery routes vary considerably throughout current investigations. Initial results suggest a potential for restoration of cardiac function in stem cell-treated patients; however, the mechanisms are not fully understood. This overview will focus on objectives, recent achievements, and future perspectives of diverse stem cell transplantation approaches.  相似文献   
3.
Patellofemoral joint: kinematic MR imaging to assess tracking abnormalities   总被引:4,自引:0,他引:4  
Shellock  FG; Mink  JH; Fox  JM 《Radiology》1988,168(2):551-553
The patellofemoral joint was imaged with magnetic resonance (MR) in the axial plane while the knee was positioned from 0 degrees to 32 degrees of flexion (nine positions). These multiple sequential images obtained within the early phases of flexion of the knee were viewed in a "cine-loop" format, producing a kinematic study that clearly demonstrated the relationship of the patella to the trochlear groove. Four healthy subjects and one patient with known bilateral subluxing patellae were studied. The preliminary results suggest that kinematic MR imaging of the patellofemoral joint is potentially useful for the evaluation of patellar tracking abnormalities.  相似文献   
4.
Recent advances in the development of conjugate polysaccharide vaccines for human use have stimulated interest in the use of assays detecting antibody-secreting cells (AbSC) with specificity for bacterial antigens. Here we present improved haemolytic plaque-forming cell (PFC) assays detecting AbSC with specificity for tetanus and diphtheria toxoid as well as for Haemophilus influenzae type b and pneumococcal capsular polysaccharides. These assays were found to be less time consuming, more economical and yielded 1.9-3.4-fold higher plaque numbers than traditional Jerne-type PFC assays. In the case of anti-polysaccharide AbSC of the IgG isotype, the increase was as high as 7.4-11.8 times. Evidence is presented that the pronounced improvement in the detection of the latter is due to the presence of aggregating anti-IgG antibody from the beginning of the assay. It is proposed that in the case of low affinity of anti-polysaccharide antibodies aggregation of secreted monomeric antibody (IgG) is critical for plaque formation and increases the avidity of binding to target cells.  相似文献   
5.
Staphylococcus aureus invasion of mammalian cells, including epithelial, endothelial, and fibroblastic cells, critically depends on fibronectin bridging between S. aureus fibronectin-binding proteins (FnBPs) and the host fibronectin receptor integrin alpha(5)beta(1) (B. Sinha et al., Cell. Microbiol. 1:101-117, 1999). However, it is unknown whether this mechanism is sufficient for S. aureus invasion. To address this question, various S. aureus adhesins (FnBPA, FnBPB, and clumping factor [ClfA]) were expressed in Staphylococcus carnosus and Lactococcus lactis subsp. cremoris. Both noninvasive gram-positive microorganisms are genetically distinct from S. aureus, lack any known S. aureus surface protein, and do not bind fibronectin. Transformants of S. carnosus and L. lactis harboring plasmids coding for various S. aureus surface proteins (FnBPA, FnBPB, and ClfA) functionally expressed adhesins (as determined by bacterial clumping in plasma, specific latex agglutination, Western ligand blotting, and binding to immobilized and soluble fibronectin). FnBPA or FnBPB but not of ClfA conferred invasiveness to S. carnosus and L. lactis. Invasion of 293 cells by transformants was comparable to that of strongly invasive S. aureus strain Cowan 1. Binding of soluble and immobilized fibronectin paralleled invasiveness, demonstrating that the amount of accessible surface FnBPs is rate limiting. Thus, S. aureus FnBPs confer invasiveness to noninvasive, apathogenic gram-positive cocci. Furthermore, FnBP-coated polystyrene beads were internalized by 293 cells, demonstrating that FnBPs are sufficient for invasion of host cells without the need for (S. aureus-specific) coreceptors.  相似文献   
6.
229 stomachs resected for duodenal and gastric ulcer and carcinoma were examined with special regard to the morphological and histochemical pattern of intestinal metaplasia (IM). The results of qualitative and semiquantitative studies were analysed statistically. Whereas duodenal and gastric ulcer cases are best discriminated by the presence or absence of IM, the strongest discriminating factor between carcinoma and gastric ulcer is the content of goblet cells in metaplastic crypts. Metaplastic crypts lined exclusively with goblet cells producing sulfated acid glycoproteins could be identified in more than one third of the cancer cases. The increase in goblet cells coincides with a loss of the more differentiated cells in the metaplastic glands, such as enterocytes, APUD cells, or Paneth cells. This "enterocoli metaplasia" seems to be specific for cancer bearing mucosa and occurs more often in cancer of intestinal type; it may represent a form of a derepressive dedifferentiation. The significance of enterocoli metaplasia as a premalignant lesion remains to be elucidated.  相似文献   
7.
Chimerism analysis of hematopoietic cells has emerged as an essential tool in nonmyeloablative hematopoietic stem cell transplantation. We have investigated the development of donor chimerism in granulocytes and CD4(+) and CD8(+) T cells in blood and bone marrow of 24 patients with hematologic malignancies who received HLA-identical sibling peripheral blood stem cell grafts after conditioning with fludarabine and 2 Gy of total body irradiation. The T-cell chimerism of blood and bone marrow was tightly correlated. Complete donor chimerism was reached earlier in the granulocytes than in the T cells. Mixed T-cell chimerism was common at the time of onset of acute graft-versus-host disease (aGVHD), and both CD4(+) and CD8(+) donor T-cell chimerism increased with the occurrence of aGVHD grades II to IV (P =.0002 and P =.019, respectively). The rate of disappearance of recipient CD8(+) T cells was faster in patients with aGVHD grades II to IV than in patients without clinically significant aGVHD (P =.016). This observation indicates a role of graft-versus-lymphohematopoietic tissue reactions in creating complete donor T-cell chimerism. A donor CD8(+) T-cell count above the median on day +14 increased the risk of subsequent development of aGVHD grades II to IV (P =.003).  相似文献   
8.
Children with recurrent lower respiratory tract infection (RLRI) may respond poorly to polysaccharide antigens. To examine how such children respond to a polysaccharide coupled to a protein carrier, we immunized 15 children with RLRI aged 8–69 months and 15 carefully age-matched healthy controls once with a Haemophilus influenzae type b (Hib) conjugate vaccine. Total IgG subclasses, total antipolysaccharide Hib antibodies, and antipolysaccharide Hib antibodies of IgM, IgG, IgA, and IgG 1–4 specificity were determined by ELISA. There were no significant differences between the two groups in any single total IgG subclass, but total IgG measured as the sum of all four subclasses was significantly lower in the children with RLRI than in the controls ( P = 0.036). Before vaccination, the children with RLRI had significantly less IgG antipolysaccharide Hib antibody than the controls ( P = 0.005), whereas 1 month later they had significantly more IgM antibody (P = 0.038). No other significant differences were found between the groups before or after immunization with respect to antipolysaccharide Hib antibodies. Since naturally occurring IgG antibodies are thought to be aquired partly as a consequence of antigenic stimulation on mucosal surfaces, we hypothesize that the low level of specific IgG found before immunization, as well as the low total IgG in the children with RLRI, may reflect an impaired ability to prime through mucosal surfaces. This is supported by our finding of an increased IgM response to Hib conjugate vaccine in these children, since this isotype predominates in the primary immune response, i.e., in the absence of immunologic memory. In conclusion, children with RLRI can be protected against invasive Hib infection as well as healthy children, but may have an immunodeficiency characterized by defective ability to respond to antigenic stimulation on mucosal surfaces.  相似文献   
9.
Thirty-six unrelated Danish patients with pauciarticular Juvenile Chronic Arthritis (PJCA) and 120 controls were typed for HLA-DPw1-w6 and the local specificity CDPHEI with bulk-expanded Primed Lymphocyte Typing (PLT) cells. The frequency of HLA-DPw2 was 52.8% in PJCA patients and 16.7% in controls (relative risk, RR = 4.5; P less than 0.001). The antigens HLA-Dw5 and/or Dw8 were present in 50% of the patients and in 21.3% of the controls (RR = 4.2; p less than 10(-3)). DPw2 was not associated (in linkage disequilibrium) with Dw5/w8 in patients or in controls, and the DP and D associations with PJCA were independent of each other. However, the combined presence of DPw2 and Dw5 and/or Dw8 gave a significantly higher risk of PJCA than each antigen alone indicating interaction of DP and DR gene products. PJCA is the first disease definitely found to be associated with a DP antigen.  相似文献   
10.
The authors studied the effect of a chemo-/radiotherapy or radio-/chemotherapy on 52 cases of microcellular bronchial carcinoma, classification "limited disease". The survival curves were slightly better for the patients submitted to primary chemotherapy, but the difference was not statistically significant, and the curves coincided again after 18 months. 60 to 80% of the patients had no complaints or only unimportant complaints during more than half of their survival time. In 23 patients with "extensive disease" who received only a symptomatic therapy or a combined palliative chemotherapy, chemotherapy had a slightly better effect, but this was not statistically significant.  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