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   5151篇
  免费   320篇
  国内免费   55篇
耳鼻咽喉   47篇
儿科学   217篇
妇产科学   128篇
基础医学   610篇
口腔科学   107篇
临床医学   393篇
内科学   1019篇
皮肤病学   145篇
神经病学   416篇
特种医学   260篇
外科学   834篇
综合类   131篇
一般理论   4篇
预防医学   322篇
眼科学   123篇
药学   359篇
中国医学   23篇
肿瘤学   388篇
  2023年   40篇
  2022年   57篇
  2021年   197篇
  2020年   95篇
  2019年   153篇
  2018年   178篇
  2017年   127篇
  2016年   181篇
  2015年   203篇
  2014年   269篇
  2013年   305篇
  2012年   424篇
  2011年   433篇
  2010年   254篇
  2009年   229篇
  2008年   328篇
  2007年   300篇
  2006年   234篇
  2005年   283篇
  2004年   227篇
  2003年   207篇
  2002年   173篇
  2001年   66篇
  2000年   70篇
  1999年   61篇
  1998年   31篇
  1997年   27篇
  1996年   24篇
  1995年   16篇
  1994年   12篇
  1993年   16篇
  1992年   20篇
  1991年   32篇
  1990年   30篇
  1989年   27篇
  1988年   23篇
  1987年   23篇
  1986年   20篇
  1985年   15篇
  1984年   16篇
  1983年   15篇
  1982年   12篇
  1981年   10篇
  1980年   10篇
  1979年   4篇
  1978年   7篇
  1977年   6篇
  1975年   4篇
  1967年   4篇
  1966年   3篇
排序方式: 共有5526条查询结果,搜索用时 109 毫秒
21.
One hundred and forty eight subjects with euthyroid solitary thyroid nodules (STN) were taken up for radionuclide perfusion study. They were found to have a cold STN on 99mTc thyroid static scan. All had fine needle aspiration cytology (FNAC), and except for subjects with chronic lymphocytic thyroiditis, were subjected to surgery for tissue diagnosis by histopathology. The diagnostic findings in these patients of solitary thyroid nodules were correlated with the histopathology. Radionuclide perfusion study is considered useful to differentiate benign from malignant cold thyroid solitary nodules with high degree of sensitivity (95%) and specificity (87.9%).  相似文献   
22.
Peripheral primitive neuroectodermal tumour (PNET)/Ewing's sarcoma (ES) and neuroblastoma (NB) are related tumours of neural crest origin with primitive neural characteristics. Fibroblast growth factor 2 (FGF2) is a critical signalling molecule for primitive neural crest cells. The treatment of NB cells with FGF2 variably affects biological characteristics such as growth and differentiation, while in PNET/ES, FGF2 predominantly induces apoptosis. The JK-GMS Askin tumour cell line can be induced to differentiate upon treatment with nerve growth factor (NGF), indicating the integrity of the cellular machinery necessary for differentiation. The present study assesses whether FGF2 can induce differentiation in JK-GMS cells. JK-GMS cells expressed high-affinity FGF receptors (FGFRs), and treatment with FGF2 induced phosphorylation of FGFR1 together with activation of extracellular signal-regulated kinases (ERK1/ERK2) and c-Jun N-terminal kinase (JNK). Subsequent biological effects were growth inhibition, neuronal differentiation, and apoptosis, and these changes were associated with increased expression of neurofilaments, reduction of c-myc and bcl-2 expression, and activation of caspase 3. Treatment of the cells with a specific inhibitor of the MAPK/extracellular signal-regulated kinase (MEK)-1, PD98059, predominantly inhibited the effects of FGF2 on growth, differentiation, and apoptosis, while an inhibitor of JNK reduced apoptosis, indicating that the ERK1/2 and JNK pathways are critical components of FGF2-mediated effects in JK-GMS cells. Additional comparative analyses of FGF2-mediated effects in two ES cell lines (CADO-ES, RD-ES) and a PNET cell line (SK-N-MC) showed pronounced differentiation in SK-N-MC, but not in CADO-ES or RD-ES cells. This study demonstrates that FGF2 can induce neuronal differentiation of PNET including Askin tumour. These findings clearly indicate that the FGF2-mediated signalling pathway plays a critical role in controlling the major properties of PNET cells and may provide a potential therapeutic target for PNET.  相似文献   
23.
Monoclonal antibody CIBCNSH3 of IgG1 isotype has been generated against human epidermal growth factor receptor (EGFR) using MDA MB 468 breast carcinoma cell line as immunogen. Earlier studies have revealed that this MAb blocked growth factor-receptor interaction and thus inhibited cell proliferation and tumor growth. In the present paper, this MAb has been extensively characterized to evaluate its application in the study of human cancers. The results were compared with those obtained using a control MAb ICR 62 specific to EGFR. Competitive assay showed that this MAb bound to an epitope in the extracellular domain of the EGFR to which MAb ICR 62 also bound. This MAb immunoprecipitated the 170 kD glycoprotein. The specificity was further confirmed by the formation of a single discrete band in western blot analysis. By flow cytometric analysis this monoclonal antibody revealed high binding affinity with MDA MB 468 cells. By immunocytochemical assay, out of 35 breast tumors studied, 40% were found to exhibit strong cell membrane staining and in the case of 25 oral cancers studied, 56% were strong positive. High expression of EGFR was observed in MDA MB 468 cells and HN 5 cells. These studies clearly indicate that MAb CIBCNSH3 might prove useful to identify tumors with high level of expression of EGFR associated with poor prognosis.  相似文献   
24.
25.
Immediate breast reconstruction-impact on radiation management   总被引:1,自引:0,他引:1  
Breast reconstruction is an option for women undergoing modified radical mastectomy due to a diagnosis of breast cancer. In certain patients, breast reconstruction is performed by insertion of a temporary tissue expander prior to the placement of permanent breast implants. Some of these patients, following mastectomy, may require chest wall irradiation to prevent loco regional relapse. The compatibility of radiation and tissue expanders placed in the chest wall is of major concern to the radiation oncologist. Clinically undetectable changes can occur in the tissue expander during the course of radiation therapy. This can lead to radiation treatment set-up changes, variation in tissue expansion resulting in unwanted cosmesis, and deviation from the prescribed radiation dose leading to over and/or under dosing of tumor burden. At Howard University hospital, a CT scan was utilized to evaluate the status of the temporary tissue expander during radiation treatment to enable us to prevent radiation treatment related complications resulting from dosimetric discrepancies. CT images of the tissue expander were obtained through the course of treatment. To avoid a 'geographic miss' the amount of fluid injected into the tissue expander was kept constant following patient's satisfaction with the size of the breast mound. The CT scans allowed better visualization of the prosthesis and its relation to the surrounding tumor bed. This technique ensured that anatomical changes occurring during radiation treatment, if any, were minimized. Repeated dosimetry evaluations showed no changes to the prescribed dose distribution. A CT of the reconstructed breast provides an important quality control. Further studies with greater number of patients are required for confirming this impact on radiation treatment.  相似文献   
26.
Antigenic polymorphism and HLA restriction may limit the immunogenicity of a subunit vaccine against liver-stage Plasmodium falciparum. We examined 59 clinical isolates and five laboratory clones of P. falciparum for polymorphism in the N- and C-terminal regions of LSA-1, evaluated binding of the corresponding peptides to selected HLA class I alleles, and measured IFN-gamma responses in residents of a malaria-endemic area of Papua New Guinea where HLA-A*1101, -24, -B13, and -B40 are the most common class I alleles. LSA-1 polymorphism was limited to a single non-synonymous mutation encoding serine (S), proline (P), or threonine (T) at amino acid 85. Nine-mer 84-92 peptides with S, T, or P at the primary anchor position bound differentially to HLA-A11, -A2, and -B7. IFN-gamma ELISPOT responses increased with age in malaria-exposed subjects: 14-16% and 30-36% of 2-5- and 6-54-year-olds, respectively, had > or =10 IFN-gamma-secreting cells/106 peripheral blood mononuclear cells when stimulated with at least one peptide variant (P<0.05). IFN-gamma responses to all three peptides were also greater for older than younger individuals. No children < 3 years old had lymphocytes that responded to all three 84-92 peptides, whereas 45% of adults (mean age 48 years) had aggregated IFN-gamma responses. These data support the notion that age-related cumulative exposure to P. falciparum increases the frequency of IFN-gamma responses to polymorphic epitopes of liver-stage antigens such as LSA-1.  相似文献   
27.

Background  

CD4+ T lymphocyte (CD4) cell count testing is the standard method for determining eligibility for antiretroviral therapy (ART), but is not widely available in sub-Saharan Africa. Total lymphocyte counts (TLCs) have not proven sufficiently accurate in identifying subjects with low CD4 counts. We developed clinical algorithms using TLCs, hemoglobin (Hb), and body mass index (BMI) to identify patients who require ART.  相似文献   
28.
29.
This study examined the prevalence and correlated factors of cigarette smoking in a cross-sectional, epidemiological survey of Korean American men living in Maryland (n=333). In this sample, 26.1% were current smokers and 42.3% were former smokers. The older age group (> or = 40 years) was more likely to have quit smoking than the younger age group (< 40 years). In multiple logistic regression analysis, acculturation was associated with smoking status; those who stayed more than 20 years in the U.S. were less likely to be current smokers (OR=0.32, 95% CI 0.13-0.77) than those who stayed less than 10 years. Alcohol use was associated with smoking status; those who consumed alcohol were more likely to be current smokers (OR=5.24, 95% CI 2.33-11.79) or former smokers (OR=5.45, 95% CI=2.69-11.04) than those did not. Those with hypertension were more likely to have quit smoking (OR=3.11, 95% CI=1.33-7.24). The results suggest that the role of acculturation in smoking status among Korean American men deserves further attention by researchers as well as by health professionals who develop smoking prevention and cessation programs.  相似文献   
30.
The PCBs, DDE, and mirex levels were measured in the subcutaneous fat and breast muscle of fifty-five waterfowl collected in New York State during 1981 and 1982. Levels were obtained by electron capture gas chromatography (EC-GC) on wet weight, dry weight, and lipid weight bases; results were confirmed by gas chromatography-mass spectrometry (GC-MS). The mean PCB levels were 6.1 (g/g in fat and 0.25 g/g in breast muscle on a wet weight basis. The mean DDE and mirex levels were 0.10 g/g and 0.28 g/g in fat and 0.01 g/g and 0.002 g/g in breast muscle on a wet weight basis, respectively.The results of the present study confirm those of the previous study (Kimet al. 1984). The detailed comparison, however, shows that the levels of PCBs and DDE in fat continued to decline while the level of mirex increased slightly.  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