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   432篇
  免费   11篇
  国内免费   15篇
儿科学   37篇
妇产科学   3篇
基础医学   28篇
口腔科学   6篇
临床医学   40篇
内科学   102篇
皮肤病学   4篇
神经病学   9篇
特种医学   128篇
外科学   23篇
综合类   44篇
预防医学   8篇
药学   11篇
肿瘤学   15篇
  2021年   2篇
  2020年   1篇
  2019年   2篇
  2018年   5篇
  2017年   2篇
  2016年   1篇
  2015年   3篇
  2014年   5篇
  2013年   10篇
  2012年   4篇
  2011年   4篇
  2010年   7篇
  2009年   14篇
  2008年   3篇
  2007年   9篇
  2006年   10篇
  2005年   9篇
  2004年   3篇
  2003年   5篇
  2002年   3篇
  2001年   1篇
  2000年   6篇
  1999年   9篇
  1998年   23篇
  1997年   39篇
  1996年   45篇
  1995年   23篇
  1994年   25篇
  1993年   25篇
  1992年   6篇
  1991年   4篇
  1990年   5篇
  1989年   17篇
  1988年   18篇
  1987年   14篇
  1986年   21篇
  1985年   7篇
  1984年   5篇
  1983年   6篇
  1982年   11篇
  1981年   5篇
  1980年   8篇
  1979年   2篇
  1978年   8篇
  1977年   6篇
  1976年   11篇
  1975年   6篇
排序方式: 共有458条查询结果,搜索用时 15 毫秒
71.
72.
During the course of differentiation of early human myeloid cells toward monocytes and granulocytes, cell surface expression of the cell adhesion molecule, CD11b/CD18 (Mo1) increases dramatically and expression of myeloperoxidase (MPO), a bacteriocidal enzyme, decreases markedly. Using the inducible promyelocytic cell line HL-60 as a model, we studied the mRNA expression of these genes. Differentiation of these cells along both a monocytic and a granulocytic pathway demonstrated that the mRNA levels of the two subunits of CD11b/CD18 increased in a pattern temporally and quantitatively similar to the increase in cell surface expression of this heterodimer. In contrast, the expression of MPO mRNA decreased in a temporal and quantitative pattern similar to the known decrease in MPO protein during differentiation, suggesting that regulation of these myeloid-specific proteins may occur at the level of mRNA expression. These findings have important implications with regard to the nature of the block in differentiation in acute nonlymphocytic leukemia and the regulation of myeloid gene expression.  相似文献   
73.
Zhu  D; Oscier  DG; Stevenson  FK 《Blood》1995,85(6):1603-1607
Splenic lymphoma with villous lymphocytes (SLVL) is a recently defined subgroup of chronic B-cell lymphoproliferative diseases. The characteristic morphology of the tumor cells, together with phenotypic and cytogenetic findings, indicate that it is a distinct entity, but the nature of the cell or origin and its relationship to other low- grade lymphomas is unclear. For B-cell tumors, analysis of the variable region heavy chain (VH) genes used to encode the clonal Ig has shown marked differences between histologic categories, both in gene usage and extent of somatic mutation. An investigation of VH genes used in five typical cases of SLVL has shown somatic hypermutation from germline sequences in all cases, indicating that the cell of origin has been exposed to the hypermutation mechanism. However, no clonal heterogeneity was detectable, demonstrating that the tumor cell does not accumulate further mutations. These characteristics are similar to those found in mature postfollicular B cells, such as plasma cells. The distribution of mutations leading to replacement amino acids differed among the cases, with three of five cases showing clear evidence for antigen selection.  相似文献   
74.
75.
A woman with a 5-year history of unilateral orofacial granulomatosis required repeated evaluations (including sequential colonoscopies) to establish the diagnosis of cutaneous Crohn's disease, a condition that proved responsive to low doses of oral methotrexate administered weekly. To our knowledge this is the first report describing the use of methotrexate for treatment of orofacial granulomatosis caused by underlying Crohn's disease.  相似文献   
76.
ObjectiveTo investigate the neurotransmitter enzyme Acetylcholinesterase (AChE) activity in the brain and blood of rats infected with Trypanosoma congolense (T. congo).MethodsPresence and degree of parasitemia was determined daily for each rat by the rapid matching method. AChE activity was determined by preparing a reaction mixture of brain homogenate and whole blood with 5, 5-dithiobisnitrobenzioc acid (DTNB or Ellman's reagent) and Acetylthiocholine (ATC). The increase in absorbance was recorded at 436 nm over 10 min at 2 min intervals. Trypanosome species identification (before inoculation and on day 10 post infection) was done by Polymerase chain reaction using specific primers.ResultsThe AChE activity in the brain and blood decreased significantly as compared with the uninfected control. The AChE activity dropped to 0.32 from 2.20 μmol ACTC min?1mg protein?1 in the brain and 4.57 to 0.76 μmol ACTC min-1mg protein?1 in the blood. The animals treated with Diminaveto at 3.5 mg/kg/d were observed to have recovered significantly from parasitemia and were able to regain AChE activity in the blood but not in the brain as compared to the control groups. We also observed, that progressive parasitemia resulted to alterations in PCV, Hb, RBC, WBC, neurophils, total protein, lymphocytes, monocytes and eosinophil in acute infections of T. congo. Polymerase chain reaction (PCR) of infected blood before inoculation and on day 10 post infection revealed 600 bp on agarose gel electrophoresis.ConclusionsThis finding suggest that decrease in AChE activity increases acetylcholine concentration in the synaptic cleft resulting to neurological failures in impulse transfer in T. congo infection rats.  相似文献   
77.
In a multicentre randomised, unblinded patient preference pilot trial to assess the feasibility of a definitive randomised trial comparing colposuspension with tension-free vaginal tape (TVT) plus anterior repair in women with incontinence and prolapse, we found that 31 of 56 eligible women agreed to participate (55%). Recruitment was more successful face to face (87%) than by letter (16%). Only four of our women agreed to be randomised, 21 (68%) chose anterior repair + TVT and six (19%) chose colposuspension. This study demonstrates the importance of pilot work for complex trials to identify issues likely to adversely affect recruitment.  相似文献   
78.

Purpose

To develop a chemical‐shift–based imaging method for fat quantification that accounts for the complex spectrum of fat, and to compare this method with MR spectroscopy (MRS). Quantitative noninvasive biomarkers of hepatic steatosis are urgently needed for the diagnosis and management of nonalcoholic fatty liver disease (NAFLD).

Materials and Methods

Hepatic steatosis was measured with “fat‐fraction” images in 31 patients using a multiecho chemical‐shift–based water‐fat separation method at 1.5T. Fat‐fraction images were reconstructed using a conventional signal model that considers fat as a single peak at –210 Hz relative to water (“single peak” reconstruction). Fat‐fraction images were also reconstructed from the same source images using two methods that account for the complex spectrum of fat; precalibrated and self‐calibrated “multipeak” reconstruction. Single‐voxel MRS that was coregistered with imaging was performed for comparison.

Results

Imaging and MRS demonstrated excellent correlation with single peak reconstruction (r2 = 0.91), precalibrated multipeak reconstruction (r2 = 0.94), and self‐calibrated multipeak reconstruction (r2 = 0.91). However, precalibrated multipeak reconstruction demonstrated the best agreement with MRS, with a slope statistically equivalent to 1 (0.96 ± 0.04; P = 0.4), compared to self‐calibrated multipeak reconstruction (0.83 ± 0.05, P = 0.001) and single‐peak reconstruction (0.67 ± 0.04, P < 0.001).

Conclusion

Accurate spectral modeling is necessary for accurate quantification of hepatic steatosis with MRI. J. Magn. Reson. Imaging 2009;29:1332–1339. © 2009 Wiley‐Liss, Inc.  相似文献   
79.
80.
Neutrophils and monocytes express high levels of PU.1 (Spi-1) but not Spi-B   总被引:9,自引:13,他引:9  
Chen  HM; Zhang  P; Voso  MT; Hohaus  S; Gonzalez  DA; Glass  CK; Zhang  DE; Tenen  DG 《Blood》1995,85(10):2918-2928
  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