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   379014篇
  免费   24169篇
  国内免费   2810篇
耳鼻咽喉   5183篇
儿科学   8199篇
妇产科学   10076篇
基础医学   53118篇
口腔科学   11775篇
临床医学   30081篇
内科学   78269篇
皮肤病学   8543篇
神经病学   27232篇
特种医学   13911篇
外国民族医学   82篇
外科学   60559篇
综合类   9953篇
现状与发展   1篇
一般理论   64篇
预防医学   17424篇
眼科学   9445篇
药学   30981篇
  1篇
中国医学   2193篇
肿瘤学   28903篇
  2021年   2607篇
  2019年   2719篇
  2018年   4512篇
  2017年   3432篇
  2016年   3518篇
  2015年   4016篇
  2014年   5695篇
  2013年   7373篇
  2012年   10014篇
  2011年   10200篇
  2010年   6180篇
  2009年   5841篇
  2008年   9454篇
  2007年   10286篇
  2006年   10207篇
  2005年   9264篇
  2004年   8773篇
  2003年   8513篇
  2002年   8194篇
  2001年   28244篇
  2000年   28777篇
  1999年   23650篇
  1998年   5161篇
  1997年   4247篇
  1996年   3830篇
  1995年   3482篇
  1994年   3104篇
  1993年   2844篇
  1992年   16052篇
  1991年   14812篇
  1990年   14155篇
  1989年   13958篇
  1988年   12579篇
  1987年   12060篇
  1986年   11103篇
  1985年   10322篇
  1984年   6911篇
  1983年   5600篇
  1982年   2719篇
  1979年   5477篇
  1978年   3347篇
  1977年   2972篇
  1975年   2641篇
  1974年   3064篇
  1973年   2865篇
  1972年   2828篇
  1971年   2774篇
  1970年   2510篇
  1969年   2543篇
  1968年   2251篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
PURPOSE: Type I IFNs (IFN-alpha/beta) have shown significant antitumor activity in preclinical models but limited efficacy and significant toxicity in clinical trials. We hypothesized that the antitumor activity of type I IFNs could be enhanced by chronic, low-dose systemic delivery and sought to test this in murine neuroblastoma models. EXPERIMENTAL DESIGN: Continuous liver-generated expression of human IFN-beta (hINF-beta) was achieved through a gene therapy-mediated approach using adeno-associated virus vectors encoding hIFN-beta (AAV hINF-beta). Orthotopic localized retroperitoneal and disseminated models of neuroblastoma were established using three different xenografts. Immunohistochemical analysis and ELISA were used to evaluate the antiangiogenic effect of therapy. RESULTS: The development of both localized orthotopic (retroperitoneal) and disseminated neuroblastoma was prevented in all mice expressing hINF-beta. Continued growth of established retroperitoneal tumors, treated with AAV hINF-beta as monotherapy, was significantly restricted, and survival for mice with established, disseminated disease was significantly prolonged following administration of AAV hINF-beta. Analysis of treated tumors revealed a significant antiangiogenic effect. Mean intratumoral vessel density was diminished and expression of the angiogenic factors vascular endothelial growth factor and basic fibroblast growth factor were both decreased. Finally, combination therapy in which AAV hIFN-beta was used together with low-dose cyclophosphamide resulted in regression of both established retroperitoneal and disseminated disease. CONCLUSIONS: AAV-mediated delivery of hIFN-beta when used as monotherapy was able to restrict neuroblastoma growth due in part to inhibition of angiogenesis. When used in combination with conventional chemotherapy, AAV hIFN-beta was able to effect complete tumor regression.  相似文献   
992.
993.
Urinary continence with a Kock or Mainz pouch is achieved by a nipple valve of the invaginated ileum which is usually fixed with metal staples. However, metal staples can cause various complications as a foreign body. The seromuscular stripping method, a new technique to create a nipple valve, was applied to 17 patients with bladder cancer in the construction of a continent urinary reservoir by the ileocolonic pouch (Mainz pouch). Metal staples were not used. The results were satisfactory except for 2 patients who became incontinent because of prolapse of the nipple in one and insufficient valve function due to ischemic change of the nipple valve in the other. Histology of the nipple valve from an autopsy case showed a good double layer nipple valve that functioned well to preserve continence.  相似文献   
994.
A low concentration of transition metal ions Co2+ and Ni2+ increases the inward current density in neurons from the land snail Helix aspersa. The currents were measured using a single electrode voltage-clamp/internal perfusion method under conditions in which the external Na+ was replaced by Tris+, the predominant external current carrying cation was Ca2+, and the internal perfusate contained 120 mM Cs+/0 K+; 30 mM tetraethylammonium (TEA) was added externally to block K+ current. In the presence of Co2+ (3 mM) or Ni2+ (0.5 mM) inward Ca2+ currents were stimulated normally by voltage-dependent activation of Ca2+ channels. There was a 5-10% decrease in the rate of rise of the inward current. The principal effect of Co2+ and Ni2+ in increasing the current density seems to be a decrease in the rate at which the inward currents decline during a depolarizing voltage pulse. The results may be due to a decrease in a voltage-dependent or Ca(2+)-dependent outward current and/or an inhibition of Ca2+ channel inactivation. Outward current under these conditions (zero internal K+) was significant and most likely due to Cs+ efflux through the voltage-activated or Ca(2+)-activated nonspecific cation channels. Co2+ is an extremely effective blocker of this outward current. These results are not an artifact of internal perfusion or the special ionic conditions. Intracellular recording of unperfused neurons in normal Helix Ringer's solution showed that the Ca(2+)-dependent action potential duration was increased significantly by low concentrations of Co2+. This result is consistant with the Co(2+)-dependent increase in inward (depolarizing) current seen in voltage-clamp experiments.  相似文献   
995.
Conventional radiography was performed at diagnosis and at follow-up 5 to 9 months later in 70 children with transient synovitis of the hip. Twenty-four of the patients also had CT examination at diagnosis. The cartilaginous and osseous reaction in the conventional antero-posterior radiographs was studied as was the relation between the radiographic and CT findings concerning fat planes, joint effusion, and position of the hip joint. At diagnosis there was significant increase in the medial joint space and at follow-up examination there was significant increase in medial and cranial joint space, metaphyseal width and acetabular roof width. There was a correlation of a bulging lateral 'capsular fat plane' to the position of abduction in the affected hip which explains the asymmetry in the lateral fat plane observed in these patients.  相似文献   
996.
997.
998.
999.
Correction of cryptotia using a subcutaneous pedicled flap   总被引:1,自引:0,他引:1  
Cryptotia is a relatively common deformity of the ear among orientals. Although many methods for correcting this deformity have been reported, there is no one perfect method. We have developed a method using a subcutaneous pedicle flap raised from the retroauricular region, where relative abundance of skin exists. We have treated 9 ears of 7 patients by the method reported herein. Results are satisfactory in all cases.  相似文献   
1000.
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