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   13025篇
  免费   921篇
  国内免费   35篇
耳鼻咽喉   136篇
儿科学   528篇
妇产科学   203篇
基础医学   1670篇
口腔科学   169篇
临床医学   1417篇
内科学   2559篇
皮肤病学   197篇
神经病学   1234篇
特种医学   367篇
外国民族医学   2篇
外科学   1771篇
综合类   186篇
一般理论   13篇
预防医学   1124篇
眼科学   527篇
药学   1068篇
中国医学   24篇
肿瘤学   786篇
  2023年   61篇
  2022年   112篇
  2021年   302篇
  2020年   170篇
  2019年   254篇
  2018年   315篇
  2017年   265篇
  2016年   264篇
  2015年   342篇
  2014年   422篇
  2013年   629篇
  2012年   998篇
  2011年   996篇
  2010年   543篇
  2009年   458篇
  2008年   778篇
  2007年   872篇
  2006年   803篇
  2005年   809篇
  2004年   721篇
  2003年   688篇
  2002年   624篇
  2001年   164篇
  2000年   139篇
  1999年   146篇
  1998年   165篇
  1997年   130篇
  1996年   88篇
  1995年   96篇
  1994年   113篇
  1993年   77篇
  1992年   115篇
  1991年   96篇
  1990年   76篇
  1989年   95篇
  1988年   83篇
  1987年   54篇
  1986年   70篇
  1985年   67篇
  1984年   64篇
  1983年   58篇
  1982年   72篇
  1981年   66篇
  1980年   48篇
  1979年   61篇
  1978年   53篇
  1977年   35篇
  1976年   32篇
  1974年   33篇
  1972年   33篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
13.
14.
Dietary supplementation with vitamin K(1), with vitamin D(3) and calcium or their combination, was examined in healthy older women during a 2-year, double-blind, placebo-controlled trial. Combined vitamin K with vitamin D plus calcium was associated with a modest but significant increase in BMC at the ultradistal radius but not at other sites in the hip or radius. INTRODUCTION: The putative beneficial role of high dietary vitamin K(1) (phylloquinone) on BMD and the possibility of interactive benefits with vitamin D were studied in a 2-year double-blind, placebo-controlled trial in healthy Scottish women > or =60 years of age. MATERIALS AND METHODS: Healthy, nonosteoporotic women (n = 244) were randomized to receive either (1) placebo, (2) 200 microg/day vitamin K(1), (3) 10 microg (400 IU) vitamin D(3) plus 1000 mg calcium/day, or (4) combined vitamins K(1) and D(3) plus calcium. Baseline and 6-month measurements included DXA bone mineral scans of the hip and wrist, markers of bone turnover, and vitamin status. Supplementation effects were tested using multivariate general linear modeling, with full adjustment for baseline and potential confounding variables. RESULTS: Significant bone mineral loss was seen only at the mid-distal radius but with no significant difference between groups. However, women who took combined vitamin K and vitamin D plus calcium showed a significant and sustained increase in both BMD and BMC at the site of the ultradistal radius. Serum status indicators responded significantly to respective supplementation with vitamins K and D. Over 2 years, serum vitamin K(1) increased by 157% (p < 0.001), the percentage of undercarboxylated osteocalcin (%GluOC) decreased by 51% (p < 0.001), serum 25-hydroxyvitamin D [25(OH)D] increased by 17% (p < 0.001), and PTH decreased by 11% (p = 0.049). CONCLUSIONS: These results provide evidence of a modest synergy in healthy older women from nutritionally relevant intakes of vitamin K(1) together with supplements of calcium plus moderate vitamin D(3) to enhance BMC at the ultradistal radius, a site consisting of principally trabecular bone. The substantial increase in gamma-carboxylation of osteocalcin by vitamin K may have long-term benefits and is potentially achievable by increased dietary intakes of vitamin K rather than by supplementation.  相似文献   
15.
16.
OBJECTIVE: To examine the relationship between growth rate of vestibular schwannomas and the expression of various growth factor receptors. STUDY DESIGN: Retrospective case review of clinical growth rate in conjunction with a histopathologic and immunohistochemical reexamination of archival specimens. SETTING: A tertiary referral neurotologic center. PATIENTS: Three groups: a historical group to act as controls, consisting of 30 patients with sporadic vestibular schwannomas removed before the unit adopted an initial interval scan policy; a group of 14 patients with sporadic vestibular schwannomas who had undergone an initial interval scan policy, showed radiologic evidence of growth, and therefore had their schwannoma removed; and a group of 16 schwannomas removed from 11 neurofibromatosis Type 2 patients. MAIN OUTCOME MEASURES: A comparison between the three clinical groups using immunohistochemical studies to determine the level of expression of the proliferation factor Ki-67, c-erbB-2, and c-erbB-3 receptors and fibroblastic growth factor receptors 1 and 4. RESULTS: The level of expression of the proliferation factor Ki-67 was very low and similar in all three groups. C-erbB-2 and c-erbB-3 receptors were not expressed in any of the groups. fibroblastic growth factor receptor 4 expression was not significantly different, but there was a variation in the expression of fibroblastic growth factor receptor 1 between the three groups that correlated well with the differing incidence of growth in the groups. The increase in expression of fibroblastic growth factor receptor 1 in the neurofibromatosis Type 2 group was not statistically significant, but the increase in expression of fibroblastic growth factor receptor 1 in the growing sporadic group was statistically significant when compared with the historical controls. The level of fibroblastic growth factor receptor 1 expression correlates significantly with the rate of growth as measured on interval magnetic resonance imaging. CONCLUSIONS: Overexpression of fibroblastic growth factor receptor 1 has a positive correlation with the incidence and the rate of growth of sporadic vestibular schwannomas.  相似文献   
17.
18.
Recombinant forms of normal glycophorin C (GPC), carrying the high frequency Gerbich blood group antigens, and its natural deletion mutants of Yus and Ge type (all combined with oligohistidyl tag) were expressed in CHO and COS 7 cells. The stable expression of all recombinant forms of GPC in CHO cells was obtained, but the level of expression was low and detectable only by flow cytometry. The high level of transient expression of GPC recombinant forms in COS 7 cells allowed their purification on Ni-NTA-agarose. The purified recombinant GPC and mutants of Yus and Ge type behaved in SDS-PAGE similarly to normal GPC forms from RBC membranes. The recombinant GPC.Yus and GPC.Ge mutants appeared as diffuse bands, suggesting the similar heterogeneity of glycosylation that was observed in natural GPC.Yus and GPC.Ge glycoproteins. The flow cytometry analysis of the transfected CHO and COS 7 cells showed that binding of anti-GPC monoclonal antibodies to GPC variants was accordant with the known fine specificity of these antibodies. The obtained recombinant forms of GPC carrying common Gerbich antigens may be useful in serology, and also as model molecules for structure-function studies.  相似文献   
19.
20.
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