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   21398篇
  免费   1752篇
  国内免费   75篇
耳鼻咽喉   313篇
儿科学   600篇
妇产科学   465篇
基础医学   3014篇
口腔科学   444篇
临床医学   1998篇
内科学   5028篇
皮肤病学   239篇
神经病学   2017篇
特种医学   650篇
外科学   3391篇
综合类   300篇
一般理论   16篇
预防医学   1617篇
眼科学   580篇
药学   1195篇
中国医学   38篇
肿瘤学   1320篇
  2023年   157篇
  2022年   304篇
  2021年   782篇
  2020年   407篇
  2019年   613篇
  2018年   744篇
  2017年   486篇
  2016年   496篇
  2015年   608篇
  2014年   789篇
  2013年   1040篇
  2012年   1510篇
  2011年   1528篇
  2010年   832篇
  2009年   710篇
  2008年   1252篇
  2007年   1240篇
  2006年   1233篇
  2005年   1158篇
  2004年   1064篇
  2003年   937篇
  2002年   923篇
  2001年   152篇
  2000年   138篇
  1999年   166篇
  1998年   183篇
  1997年   166篇
  1996年   138篇
  1995年   128篇
  1994年   118篇
  1993年   118篇
  1992年   110篇
  1991年   105篇
  1990年   115篇
  1989年   92篇
  1988年   111篇
  1987年   118篇
  1986年   82篇
  1985年   108篇
  1984年   109篇
  1983年   103篇
  1982年   138篇
  1981年   126篇
  1980年   167篇
  1979年   81篇
  1978年   87篇
  1977年   86篇
  1976年   88篇
  1975年   68篇
  1974年   72篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
2.
3.
4.

Background Context

Low back pain (LBP) is a common complaint in clinical practice of multifactorial origin. Although obesity has been thought to contribute to LBP primarily by altering the distribution of mechanical loads on the spine, the additional contribution of obesity-related conditions such as diabetes mellitus (DM) to LBP has not been thoroughly examined.

Purpose

To determine if there is a relationship between DM and LBP that is independent of body mass index (BMI) in a large cohort of adult survey participants.

Study Design

Retrospective analysis of prospectively collected National Health and Nutrition Examination Survey (NHANES) data to characterize associations between LBP, DM, and BMI in adults subdivided into 6 subpopulations: normal weight (BMI 18.5–25), overweight (BMI 25–30), and obese (BMI >30) diabetics and nondiabetics. Diabetes was defined with glycohemoglobin A1c (HbA1c) 6.5%.

Patient Sample

11,756 participants from NHANES cohort.

Outcome Measures

Percentage of LBP reported.

Methods

LBP reported in the 1999-2004 miscellaneous pain NHANES questionnaire was the dependent variable examined. Covariates included HbA1c, BMI, age, and family income ratio to poverty as continuous variables as well as race, gender, and smoking as binary variables. Individuals were further subdivided by weight class and diabetes status. Regression and graphical analyses were performed on the study population as a whole and also on subpopulations.

Results

Increasing HbA1c did not increase the odds of reporting LBP in the full cohort. However, multivariate logistic regression of the 6 subpopulations revealed that the odds of LBP significantly increased with increasing HbA1c levels in normal weight diabetics. No other subpopulations reported significant relationships between LBP and HbA1c. LBP was also significantly associated with BMI for normal weight diabetics and also for obese subjects regardless of their DM status.

Conclusions

LBP is significantly related to DM status, but this relationship is complex and may interact with BMI. These results support the concept that LBP may be improved in normal weight diabetic subjects with improved glycemic control and weight loss, and that all obese LBP subjects may benefit from improved weight loss alone.  相似文献   
5.
6.
7.
8.
This work describes the synthesis and tumor affinity testing of 8-[123I]iodo-l-1,2,3,4-tetrahydro-7-hydroxyisoquinoline-3-carboxylic acid [ITIC(OH)], a cyclic non-naturally occurring amino acid as an imaging probe for prostate cancer. Parameters for labelling were optimized with regard to the amount of precursor, the temperature and time. Thereafter, ITIC(OH) was evaluated in terms of its uptake in primary human PC-3 and DU-145 prostate cancer cells, followed by analysis of the underlying mechanisms of the radioactivity accumulation in tumor cells. No-carrier-added ITIC(OH) was obtained in 80+/-15% radiochemical yield and >98% radiochemical purity by a one-step radioiodination, using IODO-GEN as oxidant. The total synthesis time was less than 30 min, and compatible with a clinical routine production. ITIC(OH) accumulated intensively in primary human prostate cancer cells. The radioactivity incorporation in tumor following a 10-min incubation at 37 degrees C/pH 7.4 varied from 35% to 58% of the total loaded activity per 10(6) tumor cells (355-540 cpm/1000 cells). Inhibition experiments revealed that ITIC(OH) was taken up into tumor by an active transport different from the common amino acid carrier systems, including the sodium-dependent system A and B+,0, and the sodium-independent L- and ASC-type transporter. In contrast, the cellular incorporation was dependent on the membrane potential and correlated with the activity of the mitochondria. In conclusion, the specific and high-level accumulation of ITIC(OH) in human prostate carcinoma cells, indicates that the new radiopharmaceutical is a good candidate for further in vivo investigations to ascertain its potential as an imaging probe for prostate cancer by SPET.  相似文献   
9.
The New Zealand obese mouse (NZO/Hl) is characterised by hereditary obesity and type-2 diabetes, including insulin resistance, hyperinsulinaemia, and glucose intolerance. In other diabetic models, it has been revealed that the proper functioning of the glucose transporter isoform 2 (GLUT2) is essential for adequate secretion of insulin. The aim of this study was to compare the distribution of islet cells and GLUT2, as well as the expression of GLUT2-mRNA, in the pancreas of NZO mice and metabolically unimpaired NMRI (Naval Medical Research Institute) mice. Pancreas tissue was obtained from different stages of development. For molecular determination of the expression level of GLUT2-mRNA, total-RNA was extracted from the pancreas and analysed by quantitative real-time RT-PCR. All investigated NZO mice displayed increased weight, elevated hyperinsulinaemia, and slightly enhanced blood glucose levels compared with the NMRI control mice. By means of immunofluorescence microscopy drastically reduced insulin levels were detected, which might be compensated by the observed islet cell hyperplasia and hypertrophy. Furthermore, the normally peripheral localisation of the alpha-cells within islets was disturbed. By contrast, there were no changes in somatostatin cell distribution. However, considerable differences appeared with regard to GLUT2: whereas the beta-cells of NMRI mice showed dense immunostaining of the GLUT2 transporter on the cell surface, in all age groups of NZO mice, GLUT2 on the plasma membranes was reduced and dispersed in the cytoplasm. These findings agree with the molecular biological results, which displayed decreased mRNA-expression of GLUT2. In summary, the observed alteration of islet morphology and of GLUT2 expression in diabetic mice complements our previous results from a superfusion protocol and further clarifies the mechanisms of diabetogenesis in NZO mice.  相似文献   
10.
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