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   2559篇
  免费   126篇
  国内免费   77篇
耳鼻咽喉   12篇
儿科学   213篇
妇产科学   31篇
基础医学   262篇
口腔科学   59篇
临床医学   283篇
内科学   599篇
皮肤病学   79篇
神经病学   78篇
特种医学   397篇
外科学   289篇
综合类   47篇
预防医学   141篇
眼科学   52篇
药学   94篇
  2篇
中国医学   1篇
肿瘤学   123篇
  2023年   8篇
  2022年   10篇
  2021年   26篇
  2020年   18篇
  2019年   29篇
  2018年   47篇
  2017年   30篇
  2016年   27篇
  2015年   45篇
  2014年   58篇
  2013年   68篇
  2012年   61篇
  2011年   73篇
  2010年   103篇
  2009年   100篇
  2008年   82篇
  2007年   119篇
  2006年   79篇
  2005年   87篇
  2004年   62篇
  2003年   58篇
  2002年   80篇
  2001年   69篇
  2000年   65篇
  1999年   54篇
  1998年   130篇
  1997年   162篇
  1996年   134篇
  1995年   111篇
  1994年   115篇
  1993年   100篇
  1992年   32篇
  1991年   36篇
  1990年   39篇
  1989年   56篇
  1988年   49篇
  1987年   45篇
  1986年   50篇
  1985年   45篇
  1984年   26篇
  1983年   16篇
  1982年   25篇
  1981年   29篇
  1980年   25篇
  1979年   4篇
  1978年   8篇
  1977年   19篇
  1976年   25篇
  1975年   14篇
  1966年   2篇
排序方式: 共有2762条查询结果,搜索用时 15 毫秒
101.
Diverse materials with varying physical and magnetic properties have been evaluated as gastrointestinal contrast agents for magnetic resonance (MR) imaging. Uniform marking of the small bowel remains the greatest challenge. Ferrites are magnetically active iron oxide particles that are miscible with water and cause loss of signal on MR images. The decrease in MR signal intensity produced by ferrites occurs with a wide range of iron concentrations (0.1-10 mM) and with both T1- and T2-weighted pulse sequences. These effects of ferrites are explained by predominant T2 shortening with negligible T1 effects. The ferrite preparation used in this study was stable in vitro, with little iron solubilized by acid. Intragastric administration of ferrite (5 mg of iron per kg in 6 ml) routinely marked the small bowel of rats. The authors conclude that ferrites represent a promising new class of contrast agents for gastrointestinal MR imaging.  相似文献   
102.
Thirty-five patients hospitalized for recent angiographically documented arterial occlusion in the legs (27 femoropopliteal arteries and eight grafts) benefited from local fibrinolytic therapy delivered at the site of the occlusion with a 4- or 5-F catheter. This therapy combined a continuous urokinase (UK) infusion of 1,000 U/kg/hour and a lysyl plasminogen (LYS-PLG) infusion of 15 microkatals every 30 minutes. Angiographically confirmed lysis was obtained in 85% of the cases. Only 3% of the patients had major and 6% had minor groin hematomas. Only two patients had concentrations of fibrinogen as low as 100 mg/dl. Intravascular infusion of UK-LYS-PLG is as effective as streptokinase. Its excellent tolerance makes it a good alternative in the treatment of acute ischemia in the lower limbs.  相似文献   
103.
FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease.  相似文献   
104.
BACKGROUND AND AIMS: There is growing evidence of the effects of immunosuppressive agents on "immune targets" in renal transplantation. Immunological monitoring could indirectly measure the suppressive effect of these drugs and guide early preventive interventions in transplant recipients. Due to the selective antiproliferative effect of mycophenolate mofetil (MMF) on lymphocytes, our goal was to determine whether MMF modulates peripheral blood lymphocyte subsets (PBLS) in kidney allograft patients. METHODS: We assessed absolute CD3(+), CD3(+)CD4(+), CD3(+)CD8(+), CD19(+), CD16(+)CD3(-) PBLS counts and CD4/CD8 ratios for 12 months in three groups of kidney allograft patients stratified according to maintenance immunosuppressive regimen: group A (n = 31), which started MMF with prednisone (P) + cyclosporine A (CyA), and two control groups, B (n = 19) and C (n = 15) on P + CyA + azathioprine (Aza) and P + CyA regimens, respectively. We compared intra- and intergroup lymphocyte counts and ratios. RESULTS: Intergroup comparisons showed a significant reduction in all PBLS in group A (CD19(+) from 3 months and other subsets from 6 months), whereas there were no significant changes in PBLS in the other group analyses or comparisons. CONCLUSIONS: Our findings suggest that (1) MMF modulates all PBLS in kidney allograft patients, causing a progressive reduction occurring earlier in CD19(+), and (2) we can rule out that these changes were caused by the "natural immunological evolution" of the transplantation. These results could offer a new method for immunological monitoring of transplant patients.  相似文献   
105.
Pesando  JM; Conrad  TA 《Blood》1984,64(5):1074-1078
Serologic studies using four murine monoclonal antibodies specific for the common acute lymphoblastic leukemia antigen (CALLA) and five monoclonal antibodies specific for the gp24 surface antigen indicate that these leukemia-associated antigens are present on cells of comparable tissues in man and in four nonhuman primates. As in man, adherent cell populations obtained from skin, lung, and bone marrow of Macaca fascicularis, M mulatta, M nemestrina, and Papio cynocephalus react with these antibodies. Similarly, granulocytes from both man and these nonhuman primates bind CALLA- and gp24-specific antibodies. Radioimmune precipitation experiments confirm the identity of these antigens. Our studies suggest that nonhuman primates can be used to screen serologic reagents to leukemia-associated antigens for potential toxic effects on normal tissues prior to their use in man. Similarly, nonhuman primates could be employed to assess the possible role of antigen-positive stromal cells in the reconstitution of bone marrow following transplantation.  相似文献   
106.
107.
Fifty-two patients with stage III or IV nodular mixed lymphocytic- histiocytic lymphoma (NM) were entered on a prospective randomized trial comparing cyclophosphamide-prednisone (CP) to either COPP (cyclophosphamide, vincristine, procarbazine, prednisone) or BCVP (BCNU, cyclophosphamide, vincristine, prednisone). The COPP regimen utilized in this Eastern Cooperative Oncology Group (ECOG) trial was similar to the four-drug regimen C-MOPP reported by the National Cancer Institute to achieve prolonged relapse-free survival in this histology. No significant differences in complete response rates, response duration, or overall survival were noted among the three regimens. A pattern of continuous late relapse was observed for all three chemotherapy programs. Although 11 of the 18 (61%) COPP patients achieved a complete response, only 3/11 (27%) remain disease-free with a median follow-up of over 3 yr. However, two of these three long-term complete responders have died with no clinical evidence of recurrent disease. The COPP patients received 84% of the calculated ideal doses of cyclophosphamide and 78% of the ideal dosage of procarbazine. Grade 3-4 hematologic toxicity was noted in 22% of the COPP group, 36% with BCVP, and 0% for the CP patients. We were unable to confirm the ability of COPP to achieve durable complete remissions in NM lymphoma. The cyclophosphamide-prednisone combination was equally effective when compared with COPP and BCVP, but produced minimal toxicity.  相似文献   
108.
We describe three patients who had typical features of hairy cell leukemia (HCL) and multiple myeloma (MM) at the same time. In two, both diagnoses were made within a short period of time, and in the third, HCL had been present for 2 yr before the appearance of a paraprotein, bone lesions, and plasma-cell infiltrates established the diagnosis of MM. Although this association has not been previously reported, cases of HCL with osteolytic lesions or a paraprotein band have been described. The cases described may represent clinical manifestations of closely related disorders arising from divergent differentiation from a common B-cell precursor rather than a chance association.  相似文献   
109.
Oral Diseases (2010) 17 , 115–122 Objective: To determine whether oral rinse matrix metalloproteinase (MMP)‐8 levels, measured by three different methods, tissue inhibitor of matrix metalloprotease‐1 (TIMP‐1) levels and elastase activity differentiate subjects with different periodontal condition; and second, to find out if MMP‐8 levels were comparable among the methods used. Methods: MMP‐8 levels were analysed with an immunofluorometric method (IFMA), dentoELISA and commercial ELISA. Also TIMP‐1 levels and elastase activity were measured. For statistical analysis 214 study subjects were categorized into four groups, specified by the presence and number of moderate (4–5 mm) and deep (≥6 mm) periodontal pockets, and bleeding on probing percentage. Results: MMP‐8 levels especially measured by dentoELISA and adjusted to the number of teeth per subject differentiated the study group with strong periodontal inflammatory burden from groups with lower levels. This was also verified with receiver operating characteristic ( ROC) analysis. Elastase activity associated with higher IFMA and dentoELISA MMP‐8 levels. IFMA MMP‐8/TIMP and dentoELISA MMP‐8/TIMP‐1 tended to be higher with the increasing level of periodontal inflammatory burden. TIMP‐1 levels decreased with increasing age. Conclusions: Oral rinse MMP‐8 together with TIMP‐1 analysis may have potential in complementary periodontal diagnostics. dentoELISA can be applied in quantitative oral rinse chair side biomarker diagnostics.  相似文献   
110.
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