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   39291篇
  免费   3800篇
  国内免费   47篇
耳鼻咽喉   358篇
儿科学   1193篇
妇产科学   1076篇
基础医学   5296篇
口腔科学   729篇
临床医学   5222篇
内科学   7526篇
皮肤病学   558篇
神经病学   3918篇
特种医学   987篇
外科学   4661篇
综合类   833篇
一般理论   42篇
预防医学   4676篇
眼科学   618篇
药学   3021篇
  1篇
中国医学   40篇
肿瘤学   2383篇
  2023年   248篇
  2022年   390篇
  2021年   844篇
  2020年   497篇
  2019年   855篇
  2018年   961篇
  2017年   735篇
  2016年   754篇
  2015年   829篇
  2014年   1154篇
  2013年   1625篇
  2012年   2373篇
  2011年   2490篇
  2010年   1339篇
  2009年   1151篇
  2008年   2015篇
  2007年   2191篇
  2006年   2125篇
  2005年   2161篇
  2004年   1771篇
  2003年   1743篇
  2002年   1564篇
  2001年   781篇
  2000年   784篇
  1999年   679篇
  1998年   384篇
  1997年   297篇
  1996年   261篇
  1995年   300篇
  1994年   277篇
  1993年   237篇
  1992年   548篇
  1991年   501篇
  1990年   489篇
  1989年   486篇
  1988年   433篇
  1987年   438篇
  1986年   384篇
  1985年   451篇
  1984年   392篇
  1983年   305篇
  1982年   296篇
  1981年   244篇
  1980年   256篇
  1979年   356篇
  1978年   305篇
  1976年   248篇
  1974年   280篇
  1973年   290篇
  1972年   242篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
In the absence of clinically positive regional nodes, any value of prophylactic dissection in malignant melanomas depends on accurate preoperative determination of the pathway of lymphatic drainage. We report on the use of noninvasive radionuclide lymphoscintigraphy in the determination of regional patterns of lymph node drainage in patients with melanomas. Ten patients were studied; treatment was altered by test results in 2. Eleven node groups were excised in 7 patients. There have been no metastatic melanomas found in any nodal basins not detected by lymphoscintigraphy 23 to 42 months after operation.  相似文献   
93.
OBJECTIVE: The aim was to measure erythropoietin levels in amniotic fluid and extraembryonic coelomic fluid from 7-12 weeks' gestation. SUBJECTS: Twenty healthy women with ultrasonographically normal first trimester pregnancies prior to surgical termination. METHODS: Paired samples of amniotic fluid and extraembryonic coelomic fluid were collected by transvaginal ultrasound guided needling. Erythropoietin was measured in both pregnancy fluids using a radioimmunoassay. RESULTS: There was a highly significant difference between erythropoietin levels in extraembryonic coelomic fluid (median level 15.45 mU/ml; range 6.8-32.1 mU/ml) and those in amniotic fluid (median 5.0 mU/ml; range < 5.0-5.8 mU/ml) (P < 0.0001; Mann-Whitney U-test). The levels of erythropoietin in maternal serum (median 15.4 mU/ml; range 5.6-29.4 mU/ml) were similar to those in the extra-embryonic coelom (P = 0.81; Mann-Whitney U-test). No relation was demonstrated between erythropoietin levels in amniotic fluid or coelomic fluid and stage of gestation. CONCLUSION: High levels of erythropoietin in coelomic fluid suggests that the hormone is involved in the process of human extraembryonic erythropoiesis. The exact regulatory role remains unknown.  相似文献   
94.
J V Lewis  R A Myers 《Injury》1992,23(1):10-12
Non-obstructive colonic dilatation was diagnosed in six of 13,641 patients admitted to a Level I trauma centre over a 70-month period (incidence, less than 0.05 per cent). Four were older than 60 years, and five required long-term support on a ventilator. Successful treatment depends on expeditious decompression of the dilated colon. Fibreoptic colonoscopy is the recommended method.  相似文献   
95.
Introduction   Fibrosis is a component of many tissue pathologies leading to loss of normal tissue function, primarily due to excessive collagen deposition. Collagen is deposited following cleavage of the C- and N- terminal peptides from the pro-collagen molecule. The cleavage of the globular C-peptide by PCP reduces solubility of the fibrillar collagen molecule, resulting in deposition of insoluble collagen. Increased insoluble collagen deposition is a feature of all organ fibroses, with inhibition of this process, a key potential anti-fibrotic mechanism. The aim of this work was to discover potent and selective PCP inhibitors as experimental, topically applied, anti-fibrotic drugs for clinical evaluation.
Materials and methods   PCP was cloned from human osteosarcoma cells and enzymatic activity demonstrated using a PCP-specific peptide cleavage assay. Activities were confirmed by measuring cleavage of [3H]C-peptide from type-I pro-collagen. A cell-based fibroplasias model was employed to demonstrate compound efficacy using collagen deposition, liberated C-peptide and histological endpoints. The activities of PCP inhibitors in fibroblast and epithelial in vitro cell proliferation and migration assays, and selectivity vs. a panel of MMPs were also determined.
Discussion   In summary, we have identified and characterized potent and selective inhibitors of PCP for progression to clinical studies for investigation as a treatment paradigm for fibrotic disease.  

  Results  相似文献   

96.
Central dual-energy X-ray absorptiometry (DXA) is the gold standard for non-invasive measurement of bone mineral density (BMD). Using this value and subject demographics, DXA software calculates T-scores and Z-scores. Professional society guidelines for the management of osteoporosis are based on T-scores and Z-scores, rather than on the actual BMD value. Although one expects T-scores and Z-scores to be very similar in young men and women for any given BMD measurement, little literature exists on this issue. Our clinical experience shows that some younger adult individuals (premenopausal women and men younger than 50 yr) have larger than expected difference between their DXA T-score and Z-score. This cross-sectional study evaluates the extent of this discordance between Z-scores and T-scores in a sample of 4275 men and women aged 20–49 yr. All subjects were scanned by central DXA using equipment manufactured by GE Lunar, GE, Madison, WI, or Hologic, Inc., Bedford, MA. Significant differences between Z-scores and T-scores were seen within individuals at the lumbar spine, total hip, femoral neck, and trochanter (p value < 0.001) for both DXA systems. Although these differences were less than half a standard deviation (SD) in most instances, the magnitude of difference was substantial at times, being 1 or more SD in up to 11% of cases (range: −1.95 to +1.54 SD). The smallest differences were seen at the total hip and the largest differences were seen at the femoral neck for both technologies. This is in part because there is no single standard Z-score definition, resulting in different methods of calculation across, and even within, DXA manufacturers. Standardization of Z-score definition and method of calculation is indicated. DXA Z-scores should be interpreted with caution in men and women aged 20–50 yr.  相似文献   
97.
98.
99.
100.
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