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   4703篇
  免费   271篇
  国内免费   17篇
耳鼻咽喉   61篇
儿科学   115篇
妇产科学   119篇
基础医学   646篇
口腔科学   563篇
临床医学   377篇
内科学   995篇
皮肤病学   137篇
神经病学   311篇
特种医学   124篇
外科学   484篇
综合类   23篇
一般理论   1篇
预防医学   534篇
眼科学   93篇
药学   246篇
中国医学   38篇
肿瘤学   124篇
  2023年   51篇
  2022年   119篇
  2021年   179篇
  2020年   136篇
  2019年   133篇
  2018年   190篇
  2017年   120篇
  2016年   140篇
  2015年   168篇
  2014年   229篇
  2013年   272篇
  2012年   413篇
  2011年   421篇
  2010年   182篇
  2009年   185篇
  2008年   295篇
  2007年   287篇
  2006年   254篇
  2005年   228篇
  2004年   162篇
  2003年   135篇
  2002年   135篇
  2001年   100篇
  2000年   79篇
  1999年   58篇
  1998年   27篇
  1997年   18篇
  1996年   7篇
  1995年   18篇
  1994年   8篇
  1993年   6篇
  1992年   11篇
  1991年   22篇
  1990年   21篇
  1989年   15篇
  1988年   6篇
  1987年   10篇
  1986年   14篇
  1985年   7篇
  1984年   6篇
  1983年   6篇
  1977年   6篇
  1975年   5篇
  1974年   6篇
  1973年   10篇
  1971年   9篇
  1970年   16篇
  1969年   12篇
  1968年   6篇
  1967年   6篇
排序方式: 共有4991条查询结果,搜索用时 15 毫秒
11.
12.
New techniques of sling placement may be associated with infectious complications. Slings through the obturator foramen and thigh can lead to a significant abscess formation within the thigh adductor muscles. A large thigh abscess associated with a transobturator sling was diagnosed and treated. The authors report the evaluation and treatment of a unique infectious complication of transobturator slings.  相似文献   
13.
PURPOSE: A prospective radiographic study analyzed condylar position in patients who had undergone orthodontic treatment and isolated maxillary advancement after Le Fort I osteotomy. PATIENTS AND METHODS: Eleven patients were selected and radiographic images were taken in the immediate preoperative, immediate postoperative (1-2 weeks), and late postoperative periods (minimum of 6 months). Tracings were done on acetate paper for the submento-vertex radiograph, to measure the axial angulation of the condyles, and for the tomographic images of both sides, in the maximal intercuspation, rest position, and maximal opening, for the 3 periods. Linear measurements were taken for the tomograms over the posterior, superior, and anterior articular spaces. These images with the tracings were digitized and measured by means of computer software (UTHSCSA Image Tool 3.0; University of Texas Health Science Center at San Antonio, San Antonio, TX), after it had been adequately calibrated. RESULTS: The analysis of variance (ANOVA; 5% of significance) demonstrated 1) that there was no statistically significant difference for the linear measurements of the articular spaces in any of the periods, and 2) also not for the angular measure of the condyles (P > .05). In the maximal opening, there was a significant difference for the immediate postoperative period for both sides (P = .003). CONCLUSION: Le Fort I osteotomy for maxillary advancement did not cause any significant changes in this specific group of patients evaluated.  相似文献   
14.
15.
This study evaluated the effects of [D-Leu1]Microcystin-LR variants, by the exposure of Hypophthalmichthys molitrix to Microcystis aeruginosa NPLJ4. Fish was placed in aquariums and exposed to 105 cells mL−1. For 15 days, 05 individuals were removed every 05 days, and tissue samples of liver, skeletal muscle and intestinal tract were collected for histopathologic analyses. Following exposure, those surviving were placed in clean water for 15 days to evaluate their recovery. A control without toxins was maintained in the same conditions and exhibited normal histology and no tissue damage. In exposed fish, samples were characterized by serious damages that similarly affected the different organs, such as dissociation of cells, necrosis and haemorrhage. Samples showed signs of recovery but severe damages were still observed. The results should be valuable to analyze the potency of microcystin toxicity and to help in the diagnosis of fish deaths.  相似文献   
16.
Allelic frequencies of eight autosomal short‐tandem repeat (STR) loci (TH01, TPOx, CSF1PO, vWA, FES/FPS, F13A1, F13B, and CD4) were determined in 400 individuals born in the State of São Paulo. No significant deviations from Hardy‐Weinberg equilibrium were found in any loci analyzed. The Unweighted Pair‐Group Method with Arithmetic Mean (UPGMA) tree constructed based on genetic distances revealed that the present population was grouped with Europeans, and separated from African and Amerindian populations. Estimates of admixture components based on the gene identity method revealed 79% European, 14% African, and 7% Amerindian contributions to this Brazilian population sample. Am. J. Hum. Biol. 18:702–705, 2006. © 2006 Wiley‐Liss, Inc.  相似文献   
17.
The point of penetration of the recurrent laryngeal nerve into the larynx is recognized as the most frequent site of injury to the nerve during surgical procedures of the thyroid gland. The anatomical relationships of 25 right and left recurrent laryngeal nerves in 25 anatomical blocks from formalin-fixed human corpses have been studied. In 34 cases (68%), the recurrent laryngeal nerve penetrated into the larynx below the lower fibers of the inferior constrictor muscle of the pharynx (type 1 of penetration). In the remaining 16 cases (32%), the nerve crossed through those muscle fibers to penetrate into the larynx (type 2 of penetration). The thyroid gland was found to involve the recurrent laryngeal nerve at the penetration point into the larynx in 19 of 50 cases (38%).  相似文献   
18.
Protoplasts of the pathogenic plant fungus, Crinipellis perniciosa, were transformed to hygromycin B resistance using the pAN7-1 plasmid, which contains the Escherichia coli hph gene under the control of Aspergillus nidulans regulatory sequences. The pAN7-1 plasmid was introduced by PEG/CaCl(2) treatment. Transformation frequencies of 1.6-2.5 transformants/microg of DNA were achieved. About 54% of the transformants were abortive and 40 analyzed transformants were mitotically stable and showed different hygromycin B resistance levels. The presence of the hph gene was checked by PCR in five transformants and the integration of multiple plasmid copies into different genome sites was observed by Southern analysis. This is the first report of a C. perniciosa transformation system and represents an important step for further research into genetic manipulation of this fungal plant pathogen.  相似文献   
19.
The study objectives were to compare in vitro transportability and physical properties of respiratory mucus, obtained invasively by direct collection (DC) right after endotracheal intubation and non-invasively by sputum induction with 3% hypertonic saline solution inhalation (SI) 24 h before the anesthesia. Twenty-two patients with no pulmonary disease scheduled for elective abdominal surgical procedures were studied. The parameters analyzed and the main results are as follows. (1) Transportability by cilia (MCT), SI was higher than DC (0.94+/-0.25 and 0.62+/-0.25; P<0.001). There was a significant correlation between the two methods and DC could be estimated by: DC=0.21+(0.44 SI) (r=0.44; P<0.001). (2) Transportability by cough (CC), SI was higher than DC (68.23+/-32.1 and 33.58+/-19.04 mm; P=0.002). (3) Contact angle (CA), SI was lower than DC (10+/-3 degrees and 22+/-14 degrees ; P=0.025). (4) Rheological properties (no significant difference obtained between SI and DC). These results indicated that SI changes mucus physical properties and transportability in non-expectorators.  相似文献   
20.
It has been suggested for many years that the regulation of the immune system for the maintenance of peripheral tolerance may involve regulatory/suppressor T cells. In the past few years, several investigators have demonstrated that these cells can be generated in vitro. It has also been shown that they can inhibit the progression of various autoimmune disease models when infused into susceptible mice. We have generated two murine T cell lines in the presence of KLH-specific T cell clones from BALB/c or DBA2 mice. The lines are characterized by a low proliferative response to mitogens, the capacity to secrete high amounts of IL-10 and TGF-beta, and small amounts of IFN-gamma. Interestingly, these cells are unable to produce IL-2, IL-4 or IL-5. The study of the surface phenotype of both lines revealed CD4+, CD25high, CD44low and CTLA-4- cells. When injected intravenously in (CBy.D2) F1 mice, these cells were able to inhibit 50-100% of the TNP-specific antibody production, when the hapten was coupled to KLH. In the present study we offer another evidence for the existence of regulatory T cells in the T lymphocyte repertoire, suggesting that they can also regulate immune responses to foreign antigens. Furthermore, we demonstrate an alternative pathway to generate these cells different from approaches used thus far.  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