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   329篇
  免费   28篇
  国内免费   23篇
儿科学   18篇
妇产科学   6篇
基础医学   35篇
口腔科学   9篇
临床医学   38篇
内科学   91篇
皮肤病学   30篇
神经病学   9篇
特种医学   68篇
外科学   9篇
综合类   17篇
预防医学   4篇
药学   30篇
肿瘤学   16篇
  2023年   2篇
  2021年   2篇
  2019年   5篇
  2018年   5篇
  2017年   3篇
  2016年   2篇
  2015年   11篇
  2014年   5篇
  2013年   11篇
  2012年   4篇
  2011年   4篇
  2010年   11篇
  2009年   17篇
  2008年   11篇
  2007年   20篇
  2006年   11篇
  2005年   9篇
  2004年   6篇
  2003年   9篇
  2002年   6篇
  2001年   6篇
  2000年   1篇
  1999年   7篇
  1998年   21篇
  1997年   15篇
  1996年   28篇
  1995年   8篇
  1994年   18篇
  1993年   8篇
  1992年   4篇
  1991年   6篇
  1990年   10篇
  1989年   7篇
  1988年   14篇
  1987年   10篇
  1986年   8篇
  1985年   11篇
  1984年   5篇
  1983年   5篇
  1982年   6篇
  1981年   6篇
  1980年   5篇
  1979年   1篇
  1978年   3篇
  1977年   4篇
  1976年   6篇
  1975年   3篇
排序方式: 共有380条查询结果,搜索用时 15 毫秒
41.
42.
43.
Tagged MR imaging in a deforming phantom: photographic validation   总被引:1,自引:0,他引:1  
Moore  CC; Reeder  SB; McVeigh  ER 《Radiology》1994,190(3):765
  相似文献   
44.
The present report describes a successful intracytoplasmic sperm injection (ICSI) procedure performed with immotile spermatozoa from a young man with a combination of dysplasia of the fibrous sheath and dynein deficiency, a recently described variant of the immotile cilia syndrome. This methodology provides the only suitable solution for these patients in whom all other assisted fertilization technologies have previously failed, and opens the possibilities for treatment of male infertility due to severe, irreversible sperm defects such as the one reported here.   相似文献   
45.
46.
Linkage analysis was performed on a large pedigree with an autosomal dominant platelet disorder and a striking propensity in affected family members to develop hematologic malignancy, predominantly acute myelogenous leukemia. We report the linkage of the autosomal dominant platelet disorder to markers on chromosome 21q22. Four genetic markers completely cosegregate with the trait and yield maximum logarithm of difference scores ranging from 4.9 to 10.5 (theta = .001). Two flanking markers, D21S1265 and D21S167, define a critical region for the disease locus of 15.2 centimorgan. Further analysis of this locus may identify a gene product that affects platelet production and function and contributes to the molecular evolution of hematologic malignancy.  相似文献   
47.
Grinnell  BW; Walls  JD; Marks  C; Glasebrook  AL; Berg  DT; Yan  SB; Bang  NU 《Blood》1990,76(12):2546-2554
Human protein S (HPS), a regulator of hemostasis, is a vitamin K- dependent plasma protein with potential clinical utility. We have obtained high-level expression of the cDNA for HPS in two mammalian cell lines. Both cell lines secreted single chain recombinant HPS (rHPS) in serum-free medium as determined by Western blot analysis. The ability of the rHPS from both cell lines to act as a cofactor for human protein C (HPC) was determined; the rHPS secreted from the human 293 cell line had an activity six times that of the rHPS from the AV12-664 Syrian hamster cell line. Furthermore, the relative specific cofactor activity of rHPS from the 293 cell line was actually 2.5-fold higher than that of single-chain human plasma-derived HPS. Essentially all of the rHPS secreted from the 293 cell line exhibited a calcium-dependent elution profile on anion exchange chromatography, whereas only 25% to 35% of the hamster cell-derived rHPS exhibited this profile. However, the calcium-eluted rHPS from the AV12 cell line had a high specific cofactor activity, equivalent to that of the 293-derived rHPS. A NaCl- elutable rHPS fraction (calcium nondependent) was isolated from the recombinant AV12-664 cell line, further purified, and found to have reduced activity, only 40% that of the calcium-dependent rHPS. The only observable difference in the calcium-dependent and nondependent rHPS molecules was in the content of gamma-carboxyglutamic acid (Gla); the calcium-dependent material contained approximately 10 mol Gla/mol protein whereas the calcium-nondependent material contained only approximately 8 mol Gla/mol of protein. In addition, the calcium- nondependent rHPS had reduced ability to interact with phospholipid vesicles as evidenced by an eightfold increase in the apparent kd. Our data demonstrate the isolation of rHPS with high specific activity, and show that a reduction in as few as two Gla residues dramatically decreases its functional cofactor activity for HPC, due to a reduction in ability to interact with the phospholipid bilayer.  相似文献   
48.
Chapman  RM; Sutcliffe  SB 《Blood》1981,58(4):849-851
It has been reported by us and by others that after chemotherapy for Hodgkin's disease the ovary contains fewer than 5 primordial and primary follicles per 5 x 5 mm biopsy section. In young women this is associated with premature menopause. We report here that before treatment the tissue contains 18--55 such follicles per biopsy section. When women took combination oral contraceptives throughout the course of MVPP therapy, the posttreatment ovarian biopsy tissue had more than 20 follicles per histologic section. Normal menses were established in the five women who discontinued oral contraceptives at the end of MVPP therapy, and one of them is now pregnant.  相似文献   
49.

BACKGROUND:

In Saskatchewan, pneumococcal conjugate vaccination (PCV) was offered to high-risk children in 2002 and to all infants in 2005.

OBJECTIVE:

To describe trends in the frequency of medical visits for lower respiratory tract infection (LRI) and otitis media (OM) in relation to PCV use during the period 1990 to 2008.

METHODS:

Statistics regarding the number of children covered by the health insurance plan, PCV administration, and medical visits with a diagnostic code associated with LRI and OM were provided by Saskatchewan Health. Monthly rates were analyzed using dynamic state space models.

RESULTS:

In all series, there was a marked seasonal cycle and some higher-than-expected winter peak values, possibly associated with epidemics of specific respiratory viruses. Three abrupt decreases in baseline rate were observed for LRI and the final one, in February 2007, could be related to the increased proportion of children vaccinated with PCV. There was no statistical correlation between PCV use and OM visit frequency.

CONCLUSION:

Many environmental, biological and administrative factors may influence health services use, and an effect of low magnitude of a particular vaccine pertaining to nonspecific outcomes could be obscured in time-series analyses.  相似文献   
50.
Mohandas  N; Clark  MR; Kissinger  S; Bayer  C; Shohet  SB 《Blood》1980,56(1):125-128
Because of discrepancies between electronically and manually measured values of mean cell hemoglobin concentration (MCHC) encountered in studies of pathologic red cells, we studied the effect of cell water content on MCHC measurements by both methods. A series of red cell samples with varying water contents (54%-164% normal) were prepared from normal cells using the antibiotic nystatin. MCHC was then measured, using the microhematocrit centrifuge and three different electronic cell counters in common laboratory use. For MCHC values above 36 g/dl as measured by the spun hematocrit method, all three electronic counters under estimmated the MCHC, with increasing error as the true MCHC increased. For MCHC values below 30 g/dl, the values from two conductivity based instruments agreed with those from the spun hematocrit method, whereas one instrument based on light scattering overestimated the MCHC. These results indicate that inaccuracies in the measured mean cell volume (MCV) of dehydrated or otherwise undeformable cells may lead to spurious values for MCHC when electronic cell counters are used.  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