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   12898篇
  免费   661篇
  国内免费   41篇
耳鼻咽喉   269篇
儿科学   859篇
妇产科学   477篇
基础医学   1374篇
口腔科学   352篇
临床医学   1186篇
内科学   2460篇
皮肤病学   458篇
神经病学   809篇
特种医学   293篇
外科学   2120篇
综合类   407篇
一般理论   3篇
预防医学   1216篇
眼科学   298篇
药学   679篇
  1篇
中国医学   15篇
肿瘤学   324篇
  2018年   82篇
  2017年   101篇
  2016年   87篇
  2015年   153篇
  2014年   143篇
  2013年   248篇
  2012年   326篇
  2011年   366篇
  2010年   209篇
  2009年   230篇
  2008年   260篇
  2007年   242篇
  2006年   271篇
  2005年   263篇
  2004年   166篇
  2003年   158篇
  2002年   190篇
  2001年   195篇
  2000年   164篇
  1999年   204篇
  1998年   204篇
  1997年   238篇
  1996年   248篇
  1995年   200篇
  1994年   189篇
  1993年   202篇
  1992年   206篇
  1991年   195篇
  1990年   197篇
  1989年   193篇
  1988年   205篇
  1987年   203篇
  1986年   159篇
  1985年   173篇
  1984年   156篇
  1983年   123篇
  1982年   88篇
  1981年   95篇
  1979年   115篇
  1978年   105篇
  1977年   115篇
  1976年   90篇
  1959年   347篇
  1958年   760篇
  1957年   869篇
  1956年   775篇
  1955年   804篇
  1954年   780篇
  1949年   182篇
  1948年   126篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Scintigraphic visualization of intrathecal liposome biodistribution   总被引:1,自引:0,他引:1  
Background: Liposomes containing local anaesthetics have been administered intrathecally and in the epidural space. Poor attention has been given to the pharmacokinetics of liposomes as drug carriers. Therefore, we observed the biodistribution of liposomes after intrathecal injection in rats by scintigraphic imaging during 24 h.
Methods: We administered 99Tc-labeled multilamellar (MLV) and small unilamellar vesicles (SUV) of defined size and volume dispersities into the cerebrospinal fluid at the lumbar level. Those vesicles were free of contamination by radiolabeled colloids as visualized by light and electron microscopy and of neurotoxic products from phosphatidylcholine hydrolysis and peroxidation, both during the preparation process and after 24 h incubation in cerebrospinal fluid at 37°C in vitro.
Results: SUV immediately diffused from the lumbar site of injection to the head and were cleared between 1 and 24 h after injection. MLV were cleared more slowly from the spinal space and appeared in the head region 1 h after injection where they accumulated up to 24 h. These differences were explained in terms of vesicle sizes and volumes. SUV with 0.05 μm diameters were rapidly absorbed into the blood through the arachnoid granulations. In contrast, particles larger than the upper size limit of the arachnoid granulations permeability (±8 μm) could accumulate in the head with a slow elimination rate.
Conclusion: This difference in clearance from the intrathecal space outlines the importance of defining the size of the liposomes, the distribution of a tracer or a drug inside the liposomal preparation, the chemical stability and the absence of toxic degradation products of liposome formulations before clinical use.  相似文献   
62.
The records of 28 patients who underwent free jejunal graft reconstruction after resection for cancer involving the pharynx were analysed. Seven patients had a T3 carcinoma, 15 patients T4 and six patients recurrence after laryngectomy. Ten patients had received radiotherapy in the past. Post-operatively, 15 patients (54%) had complications and two patients (7%) died. No significant difference was observed in the complication rate between the group that received radiotherapy in the past and those who did not. Nineteen patients received post-operative radiotherapy. Nine patients had no radiotherapy on the basis of complete resection or because of serious complications. For the whole group the 2-year recurrence free period and survival were 42% and 51% respectively. The postoperative radiotherapy group had a significantly better survival (73%) and recurrence free period (63%) than the group without post-operative radiotherapy (0%). Thus, post-operative radiotherapy seems indicated irrespective of resection margins.  相似文献   
63.
64.
The synthesis of acute-phase proteins by the liver during sepsis has been thought to be induced primarily by monokines released from activated macrophages, although glucocorticoid hormones may also stimulate this process to a lesser degree. According to this concept, synthesis of these proteins following administration of bacterial endotoxins would be an indirect effect and would not reflect a direct interaction of the endotoxin molecule with the hepatic parenchymal cell. We observed, however, that the synthesis of a 23-kilodalton protein was stimulated directly by the addition of lipopolysaccharide to cultures of primary mouse hepatocytes. The synthesis of this protein was also stimulated by glucocorticoids and interleukin 1. These findings demonstrate that certain hepatic proteins are subject to complex regulation by several factors thought to be important mediators of sepsis; in addition, they suggest that hepatic parenchymal cells may have the intrinsic capacity to respond directly to bacterial endotoxins.  相似文献   
65.
Interleukin 2 (IL-2) is an essential mediator of the immune response and has also been shown to be protective in experimental models of sepsis. Macrophages have IL-2 receptors but their function is unknown. We investigated the effect of IL-2 on Kupffer cells, the fixed macrophages of the liver, using an in vitro rat hepatocyte-Kupffer cell coculture system. In this model, endotoxin (lipopolysaccharide) triggers Kupffer cells to induce suppression of hepatocyte protein synthesis. We found that pretreatment with 10 U/mL or more of IL-2 primed Kupffer cells, significantly reducing the concentration of lipopolysaccharide necessary to trigger Kupffer cell-mediated suppression of hepatocyte protein synthesis. Higher concentrations of IL-2 (greater than or equal to 1 x 10(4) U/mL) alone were capable of priming and triggering Kupffer cells to suppress hepatocyte protein synthesis. These data show that IL-2 increases Kupffer cell sensitivity to endotoxin, suggesting that IL-2 may play an important role in regulating macrophage responses to septic stimuli.  相似文献   
66.
We report on the mechanisms, the environmental changes and patient compliance with regard to conventional and new dust and mite avoidance measures to prevent allergic symptoms caused by mite allergens, taking into account both allergen contamination and the developmental success of pyroglyphid Acari. Twenty patients with persisting rhinitic complaints were selected and matched. Although the patients had performed some conventional dust and mite avoidance measures (patient compliance was 90%), the dwellings proved to be a stimulus for mite development. Moisture problems due to faulty construction and excessive moisture production were common. Since humidity conditions could not be changed at short notice, the 20 homes were subjected to the new variants of mite allergen avoidance based on intensive cleaning without (control) and with an acaricide incorporated (acaricidal cleaner [Acarosan]). After the carrying out of conventional avoidance measures, these patients still had allergic symptoms, and dust from only 23 to 52% of their textile objects was under the proposed guanine (mite faeces indicator) risk level. Only the acaricidal cleaner was able to decrease the allergenic mite load (and the burden of the patients) significantly in this 12 month period. With respect to mite-extermination, acaricidal cleaning was 88% better than intensive cleaning. Reduction of guanine was 38% better in the Acarosan treatment group. Clinical results have been reported elsewhere. A significant difference in favour of the acaricidal cleaning was seen in both subjective (as regards symptoms) and in objective data (total IgE). Another 50 patients were questioned. About 90% were willing to spend two weekends (70%), or at the most one weekend (20%) per year sanitizing the dwelling by cleaning it with the whole family. The authors of this report consider acaricidal cleaning to be a significant improvement in the management of mite-allergic diseases, such as rhinitis. Compared with the replacement of home textiles, this treatment is less expensive and more effective. Patient compliance is acceptable, but depends on acceptance by physicians and the initial motivation and consequent burden on the patient.  相似文献   
67.
From the above discussion, it can be seen that the establishment of epithelial polarity plays a critical role in mammalian development. Functional and structural transitions in the vectorial processes of epithelial tissues in the developing embryo accompany critical events during development. Pathophysiologic states may arise due to either genetic or acquired abnormalities of polarity. Immaturity of vectorial transport functions frequently accompany the onset of premature birth and result in abnormal function of transport epithelia. Further definition of the molecular mechanisms that lead to the establishment and maintenance of epithelial polarity, as well as the developmental sequence of vectorial transport functions in developing epithelia, will lead to better understanding and treatment of fundamental disease states in the fetus and newborn.  相似文献   
68.
69.
70.
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