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   11850篇
  免费   1179篇
  国内免费   579篇
耳鼻咽喉   50篇
儿科学   78篇
妇产科学   42篇
基础医学   788篇
口腔科学   153篇
临床医学   1169篇
内科学   1045篇
皮肤病学   71篇
神经病学   619篇
特种医学   301篇
外科学   471篇
综合类   1441篇
一般理论   1篇
预防医学   1216篇
眼科学   104篇
药学   2854篇
  7篇
中国医学   3004篇
肿瘤学   194篇
  2024年   40篇
  2023年   225篇
  2022年   340篇
  2021年   474篇
  2020年   422篇
  2019年   458篇
  2018年   398篇
  2017年   437篇
  2016年   463篇
  2015年   408篇
  2014年   806篇
  2013年   1076篇
  2012年   902篇
  2011年   903篇
  2010年   626篇
  2009年   546篇
  2008年   619篇
  2007年   580篇
  2006年   512篇
  2005年   424篇
  2004年   328篇
  2003年   337篇
  2002年   247篇
  2001年   251篇
  2000年   176篇
  1999年   139篇
  1998年   153篇
  1997年   136篇
  1996年   105篇
  1995年   88篇
  1994年   100篇
  1993年   85篇
  1992年   92篇
  1991年   61篇
  1990年   43篇
  1989年   48篇
  1988年   42篇
  1987年   34篇
  1986年   26篇
  1985年   53篇
  1984年   56篇
  1983年   50篇
  1982年   40篇
  1981年   32篇
  1980年   41篇
  1979年   34篇
  1978年   27篇
  1977年   27篇
  1976年   23篇
  1974年   21篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
31.
化学染发剂和冷烫精的毒性及对人体健康影响的调查研究   总被引:7,自引:1,他引:6  
本文通过化学染发剂和冷烫精对大白鼠骨髓多染红细胞,毛囊细胞的微核实验及人群健康影响调查,结果表明化学染发剂,冷烫清具有较强致突变作用,两者同时使用致突变明显增强,并提出研制高效无毒染发剂和加强防护的重要性。  相似文献   
32.
Both systemic and local therapy, for conditions of the breast and unrelated to it, may produce manuno-graphic changes. Some of these are characteristic, such as the pattern of scarring seen in reduction mammo-plasty. In many other instances, however, the changes produced overlap features commonly seen in malignancy. A knowledge of the timing, natural history and spectrum of these changes will aid mammographic interpretation.  相似文献   
33.
34.
Systolic and diastolic blood pressures were measured on 254 monozygotic (MZ) and 260 dizygotic (DZ) male twin pairs, during middle age (average age 48 years) and at two later age points. Genetic and environmental components of covariation were modeled by time series. For both measures, shared environmental influences were absent and specific environmental influences were largely time-specific. Although heritability was about 0.5 at each time point, genetic variation present at middle age contributed only about 60% to that present 9 years later, the remaining 40% being new. Fifteen years later, at the third time point, no new genetic variation was evident, variation in individual differences being entirely attributable to genetic differences laid down at the two earlier ages. © 1993 Wiley-Liss, Inc.  相似文献   
35.
 Dermal exposures of methanol were administered in a clinical study designed to compare several biological indicators. Four subjects were exposed in five exposure sessions of varying length. In each session, a sequence of measurements of methanol concentrations in blood, breath, and headspace samples of air at exposed and unexposed skin were collected before and after dermal exposures. Skin headspace samples, collected in gas sampling bags, were designed to reflect equilibrium skin: air partitioning. At exposed skin, headspace samples were highly elevated for at least 8 h following exposure, indicating the presence of a methanol reservoir in skin. After exposure, methanol concentrations at exposed skin showed a rapid initial decline, then a slower first-order decrease. Methanol concentrations were clearly detectable in headspace samples at unexposed skin. Substantial transfer from exposed skin occurred due to mechanical contact and washing. When transfer was restricted, surface concentrations at unexposed skin were similar to levels in breath and were strongly correlated to methanol concentrations in blood. While results are preliminary due to the small sample sizes and several unresolved experimental issues, the simple, rapid, and noninvasive skin headspace measurements appear useful as a biological exposure indicator that clearly shows the presence and site of a dermal exposure, and measurements at unexposed skin reflect concentrations in blood. Received: 14 March 1995/Accepted: 3 November 1995  相似文献   
36.
Quinidine gluconate 324 mg sustained release tablets (Quinaglute) was administered as a single dose to 15 healthy male subjects following an overnight fast, immediately following a high fat (HF) breakfast or immediately following a low fat (LF) breakfast. Serum samples were obtained over a 48 h period and analyzed for quinidine content using a high performance liquid chromatographic assay. Under the conditions of the study, both the rate and extent of quinidine bioavailability was significantly affected by food. The extent of bioavailability was statistically significantly greater (p less than 0.05) following both the HF and LF meals as compared to that in the fasted state. Rate of bioavailability was significantly enhanced following the LF meal as compared to that of the other two treatment groups. Although peak concentrations were greater and time to peak concentrations somewhat later following the HF meal versus those under fasting conditions, these differences were not statistically significant. In addition, the characteristics of the serum concentration-time profile (as defined by the number, magnitude, and time of occurrence of the multiple absorption maxima) was unique for each of the three treatment groups. Possible mechanisms underlying these results are explored.  相似文献   
37.
We developed an objective and automatic procedure to assess the severity of levodopa-induced dyskinesia (LID) in patients with Parkinson's disease during daily life activities. Thirteen patients were continuously monitored in a home-like situation for a period of approximately 2.5 hours. During this time period, the patients performed approximately 35 functional daily life activities. Behavior of the patients was measured using triaxial accelerometers, which were placed at six different positions on the body. A neural network was trained to assess the severity of LID using various variables of the accelerometer signals. Neural network scores were compared with the assessment by physicians, who evaluated the continuously videotaped behavior of the patients off-line. The neural network correctly classified dyskinesia or the absence of dyskinesia in 15-minute intervals in 93.7, 99.7, and 97.0% for the arm, trunk, and leg, respectively. In the few cases of misclassification, the rating by the neural network was in the class next to that indicated by the physicians using the AIMS score (scale 0-4). Analysis of the neural networks revealed several new variables, which are relevant for assessing the severity of LID. The results indicate that the neural network can accurately assess the severity of LID and could distinguish LID from voluntary movements in daily life situations.  相似文献   
38.
本研究探讨了中草药“三匹风”主要成份之一的黄酮类化合物的提取方法和化学鉴定法。经实验优选,确定采用70%乙醇提取法分离提取三匹风中的总黄酮成份。  相似文献   
39.
Yucatan Pig: An Optimal Hairless Model for a True Random Cutaneous Flap   总被引:1,自引:0,他引:1  
Porcine models have been used extensively for skin flap research because of the established similarity between the cutaneous blood supply of the swine and humans. The Yucatan minipig provides an excellent model for researching the properties of random cutaneous flaps, offering several advantages over other breeds of swine. In this study, a total of 67 random cutaneous dorsal flank flaps measuring 4 × 14 cm were raised on nine Yucatan minipigs. The mean survival length (10.03 ± 1.60 cm) of the nondelayed flaps was greater than others reported in the literature. The well-defined plane between the subcutaneous tissue and the panniculus carnosus facilitated flap elevation consistently above the level of the panniculus carnosus thereby ensuring the creation of a true random cutaneous flap. Furthermore, the hairless nature of the skin, particularly beneficial in studying chemical peels, permits easy visualization and monitoring of any external skin changes. These advantages make the Yucatan minipig a more desirable alternative to other breeds of swine for use in skin flap research.  相似文献   
40.
Abstract The major reason for late graft losses is chronic rejection. Recently, a large number of studies have indicated that proteolytic enzymes play an important role as mediators of glomerular injury. The cysteine proteinases cathepsins B and L degrade structural matrix proteins such as type I collagen and laminin. We investigated intraglomerular protease activities in 12 patients after kidney graftectomy because of end-tage renal disease following chronic rejection. A group of 12 patients undergoing nephrectomy because of cancer served as controls using only non-involved parts of the kidney. The activities of cathepsins B and L in homogenates of isolated glomeruli were measured fluorometrically methylcoumarylamidc substrates and related to DNA content. In rejected kidney allografts we observed significantly enhanced intraglomerular cathepsin B activity and cathepsin B + L activity.  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