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   61525篇
  免费   5699篇
  国内免费   3447篇
耳鼻咽喉   513篇
儿科学   880篇
妇产科学   1008篇
基础医学   7068篇
口腔科学   1091篇
临床医学   7171篇
内科学   9926篇
皮肤病学   741篇
神经病学   2924篇
特种医学   2537篇
外国民族医学   34篇
外科学   7414篇
综合类   9131篇
现状与发展   16篇
一般理论   16篇
预防医学   3989篇
眼科学   1486篇
药学   6543篇
  54篇
中国医学   3094篇
肿瘤学   5035篇
  2024年   177篇
  2023年   847篇
  2022年   2089篇
  2021年   2889篇
  2020年   2082篇
  2019年   1905篇
  2018年   2037篇
  2017年   1814篇
  2016年   1805篇
  2015年   2510篇
  2014年   3177篇
  2013年   3195篇
  2012年   4466篇
  2011年   4744篇
  2010年   3088篇
  2009年   2533篇
  2008年   3377篇
  2007年   3447篇
  2006年   3207篇
  2005年   2971篇
  2004年   2408篇
  2003年   2226篇
  2002年   2015篇
  2001年   1673篇
  2000年   1615篇
  1999年   1446篇
  1998年   782篇
  1997年   787篇
  1996年   636篇
  1995年   533篇
  1994年   465篇
  1993年   317篇
  1992年   510篇
  1991年   416篇
  1990年   389篇
  1989年   347篇
  1988年   276篇
  1987年   265篇
  1986年   209篇
  1985年   162篇
  1984年   117篇
  1983年   84篇
  1982年   60篇
  1981年   74篇
  1980年   40篇
  1979年   72篇
  1978年   37篇
  1974年   36篇
  1973年   33篇
  1972年   41篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
We have previously demonstrated low levels of immunoreactive (ir)-beta-endorphin (beta-EP) and ir-ACTH in a subpopulation of mouse spleen macrophages, which is consistent with an involvement of opioid peptides in modulation of immune responses. Gel chromatography studies suggested the presence of an approximately 3.5,000-molecular weight (mol wt) species, putatively beta-EP, an approximately 11.5,000-mol-wt species, putatively beta-lipotropin, and a higher molecular weight species (putative beta-EP precursor, pro-opiomelanocortin (POMC). In this study we have extended our original findings by demonstrating the presence of messenger RNA for POMC by the use of a complementary DNA probe and Northern blot analysis of extracts of mouse and rat spleen. In addition, using high performance liquid chromatography (HPLC), we have shown that the major endorphin species in mouse spleen macrophages is beta-EP1-31, and that there are smaller amounts of each of the acetylated forms, N-acetyl-beta-EP1-16 (alpha-endorphin), N-acetyl-beta-EP1-17 (gamma-endorphin), N-acetyl-beta-EP1-27, and N-acetyl-beta-EP1-31. We interpret these studies as showing that (a) the spleen is an organ of POMC synthesis and that (b) the predominant COOH-terminal product of macrophage POMC is the opiate-receptor active species beta-EP1-31.  相似文献   
34.
Spinal cord injury: prognosis for ambulation based on quadriceps recovery.   总被引:1,自引:0,他引:1  
The purpose of this study was to determine if early recovery of quadricep muscle strength post spinal cord injury (SCI) is a useful predictor of future ambulation. Seventeen C4-T10 motor incomplete (Frankel C) spinal cord injured patients admitted to our center between March 1988 and April 1990 were examined within 72 hours to one week post injury. All patients had initial quadricep strengths < or = 2/5 in both legs. Strength in the strongest quadricep was followed prospectively at intervals from admission to one year post injury. Recovery time to a > 3/5 quadricep was established for each patient. Patients were categorized into 2 groups: FA (n = 11) were those patients who achieved functional ambulation and NA (n = 6) were those subjects who were nonambulators. Functional ambulators were defined as those patients who were able to walk in the household and/or the community while non ambulators were those who either did not ambulate or did so only for exercise. All patients (n = 9) who achieved a > 3/5 quadricep by 2 months post SCI became functional ambulators whereas in the group of 8 patients who did not achieve a > 3/5 by 2 months, only 2 became functional ambulators. This result was found to be significant using a point-by-serial correlation with p < 0.05. In conclusion, motor incomplete spinal cord injured patients who recovered to a > 3/5 quadricep strength by 2 months post injury had an excellent prognosis for subsequent ambulation by 6 months post injury.  相似文献   
35.
36.
37.
It has been suggested that gains of chromosomes 7 and 17 and loss of Y occur in renal papillary adenoma and that progression to papillary renal cell carcinoma is marked by gains of additional chromosomes, most frequently 12, 16, and 20. Previous studies have included very few lesions of <5 mm in diameter, a requirement of the present definition of papillary adenoma. Ten papillary adenomas (ranging from 1 to 5 mm in diameter) from autopsy material and 10 surgically resected papillary renal cell carcinomas were studied with fluorescence in situ hybridization in paraffin sections using centromeric probes for chromosomes 7, 12, 16, 17, 20, and Y diluted 1:100 with tDenHyb1 buffer. The signals in 50 to 150 nuclei were counted in each tumor. Controls for all the probes were normal renal tissues from the same patients. Three or more signals per nucleus were frequently observed in papillary adenomas: chromosome 7 (range, 10 to 50%; > or = 30% in 9 of 10), 17 (range, 10 to 47%; > or = 30% in 7), 16 (range, 1 to 63%; > or = 10% in 5), 12 (range, 0 to 32%; > or =10% in 4), and 20 (range, 5 to 49%; > or = 10% in 5). Loss of the Y chromosome was observed in 80 to 90% of nuclei in 9 adenomas from males. Three or more signals were frequent in papillary renal cell carcinomas: chromosome 7 (range, 32 to 63%; > or =30% in 10 of 10), 17 (range, 28 to 61%; > or = 30% in 7), 16 (range, 0 to 45%; > or = 10% in 6), 12 (range, 1 to 37, > or = 10% in 5), 20 (range, 2 to 44%; > or = 10% in 4). No signal for Y was observed in 12 to 88% (> or = 81% in 6) of nuclei in 7 carcinomas from males. Statistical analysis showed no difference between adenomas and carcinomas. Gains of chromosomes 7, 17, 16, 12, and 20 and loss of the Y chromosome occur early in the evolution of papillary renal cell neoplasia in tumors that are only a few millimeters in diameter. Progressive gains of these chromosomes do not appear to correlate with the transition from adenoma to carcinoma.  相似文献   
38.
39.
BACKGROUND: Dietary salt and fluid restriction is important in controlling fluid balance in patients on continuous ambulatory peritoneal dialysis (CAPD). However, it is often difficult to monitor patients' dietary total sodium intake (TSI). Usually, total sodium removal (TSR), the sum of urinary sodium removal (USR) and dialysate sodium removal (DSR), is suggested to represent TSI. In the present study, we investigated the reliability of using TSR as a surrogate to TSI in CAPD patients. METHODS: 40 clinically stable CAPD patients were closely followed for 3 months. Their TSI, USR, DSR, and fluid status were measured twice: at baseline and at the end of this study respectively. Fluid status was evaluated by bioimpedance analysis. Patients with increased sodium intake (group ISI) or decreased sodium intake (group DSI) (both >0.5 g/day or >21.74 mmol/day elemental sodium) were included in this study. RESULTS: There were 15 patients in group ISI and 9 patients in group DSI. During the follow-up, although TSI increased in group ISI and decreased in group DSI (p < 0.05), there were no significant changes in USR, DSR, or TSR in either group. No relationship was found between TSI and TSR. Changes in weight, blood pressure, urine volume, ultra-filtration, and small solute removal (Kt/V and creatinine clearance) were not statistically significant between the two groups. Fluid status deteriorated in group ISI and improved in group DSI (p < 0.05). CONCLUSIONS: Our study suggests that changes in total sodium intake do not lead to proportionate changes in total sodium removal in CAPD patients. Therefore, TSR (the sum of USR and DSR) should be used cautiously to monitor TSI in this patient population.  相似文献   
40.
We examined whether the inhibition of neoplastically transformedcell growth by co-cultured non-transformed cells involved gapjunctional intercellular communication (GJIC). The growth ofpoorly communicating (  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