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   2996篇
  免费   159篇
  国内免费   8篇
耳鼻咽喉   45篇
儿科学   373篇
妇产科学   106篇
基础医学   431篇
口腔科学   74篇
临床医学   141篇
内科学   594篇
皮肤病学   89篇
神经病学   67篇
特种医学   71篇
外科学   390篇
综合类   111篇
一般理论   1篇
预防医学   155篇
眼科学   118篇
药学   230篇
中国医学   14篇
肿瘤学   153篇
  2022年   19篇
  2021年   70篇
  2020年   48篇
  2019年   39篇
  2018年   56篇
  2017年   41篇
  2016年   45篇
  2015年   47篇
  2014年   79篇
  2013年   76篇
  2012年   119篇
  2011年   146篇
  2010年   77篇
  2009年   86篇
  2008年   129篇
  2007年   115篇
  2006年   90篇
  2005年   109篇
  2004年   97篇
  2003年   99篇
  2002年   97篇
  2001年   102篇
  2000年   89篇
  1999年   75篇
  1998年   43篇
  1997年   25篇
  1996年   39篇
  1995年   21篇
  1992年   53篇
  1991年   59篇
  1990年   71篇
  1989年   57篇
  1988年   63篇
  1987年   54篇
  1986年   70篇
  1985年   47篇
  1984年   42篇
  1983年   30篇
  1979年   40篇
  1978年   22篇
  1977年   26篇
  1976年   28篇
  1975年   29篇
  1973年   33篇
  1972年   38篇
  1971年   29篇
  1970年   31篇
  1969年   32篇
  1968年   27篇
  1967年   34篇
排序方式: 共有3163条查询结果,搜索用时 15 毫秒
31.
32.
33.
Cyclic ADP-ribose (cADPR) mobilizes calcium from intracellular stores and contributes to agonist-induced intracellular calcium elevation in airway smooth muscle (ASM). In this study we determined the functional role of CD38/cADPR signaling in the regulation of airway tone using CD38 deficient (cd38(-/-)) mice. The responsiveness to different doses of methacholine, as determined by changes in lung resistance and dynamic compliance, was significantly (P < or = 0.05) lower in cd38(-/-) mice compared with wild-type controls. To determine the mechanism responsible for the reduced responsiveness, we measured the intracellular calcium responses to contractile agonists in ASM cells. In ASM cells isolated from cd38(-/-) mice, the intracellular calcium responses to acetylcholine and endothelin-1 were significantly lower than in controls. Pretreatment of ASM cells with a cADPR antagonist resulted in attenuated intracellular calcium responses to endothelin-1 in cells isolated from wild-type mice, but not in those isolated from the cd38(-/-) mice. Very low cADPR levels and no detectable ADP-ribosyl cyclase activity were observed in lung tissue from cd38(-/-) mice, suggesting that CD38 is a critical source for cADPR synthesis. The results of the present study demonstrate that CD38/cADPR contributes to airway smooth muscle tone and responsiveness through its effects on agonist-induced elevation of intracellular calcium in ASM cells.  相似文献   
34.
Primary malignant lymphomas of the breast (PBL) are uncommon constituting only 0.04 to 0.53% of malignant breast neoplasms. We wish to report the clinical, cytological and histologic findings of PBL diagnosed in a 52 years old female.  相似文献   
35.
The need for fast, accurate and high resolution dosimetric quality assurance in radiation therapy has been outpacing the development of new and improved 2D and 3D dosimetry techniques. This paper summarizes the efforts to create a novel and potentially very fast, 3D dosimetry method based on the observation of scintillation light from an irradiated liquid scintillator volume serving simultaneously as a phantom material and as a dose detector medium. The method, named three-dimensional scintillation dosimetry (3DSD), uses visible light images of the liquid scintillator volume at multiple angles and applies a tomographic algorithm to a series of these images to reconstruct the scintillation light emission density in each voxel of the volume. It is based on the hypothesis that with careful design and data processing, one can achieve acceptable proportionality between the local light emission density and the locally absorbed dose. The method is applied to a Ru-106 eye plaque immersed in a 16.4 cm3 liquid scintillator volume and the reconstructed 3D dose map is compared along selected profiles and planes with radiochromic film and diode measurements. The comparison indicates that the 3DSD method agrees, within 25% for most points or within approximately 2 mm distance to agreement, with the relative radiochromic film and diode dose distributions in a small (approximately 4.5 mm high and approximately 12 mm diameter) volume in the unobstructed, high gradient dose region outside the edge of the plaque. For a comparison, the reproducibility of the radiochromic film results for our measurements ranges from 10 to 15% within this volume. At present, the 3DSD method is not accurate close to the edge of the plaque, and further than approximately 10 mm (<10% central axis depth dose) from the plaque surface. Improvement strategies, considered important to provide a more accurate quick check of the dose profiles in 3D for brachytherapy applicators, are discussed.  相似文献   
36.
37.
Extraskeletal chondroma is a rare entity. A fairly benign condition, it is usually seen in adults. It presents as an enlarging mass, most commonly in the hand. Local excision is the treatment of choice. We present a case of extraskeletal chondroma of hand in a 12 year male child. Its variable histological appearance not infrequently leads to a mistaken diagnosis of chondrosarcoma.  相似文献   
38.
Aspergillus infection of the central nervous system (CNS) is an uncommon disease. Most of the reported cases are of sinocranial spread and cases with contiguous spread to spinal cord from lung and other organs are uncommon. A case of pulmonary aspergillosis with extension to thoracic vertebrae forming a paraspinal mass resulting in neurological deficit due to Aspergillus flavus, is reported. The 43 year old patient did not have any obvious predisposing condition. He presented with loss of motor function and succumbed to the infection despite operative intervention and antifungal therapy. A brief update on CNS aspergillosis is presented along with detailed clinical, radiological and laboratory work up of the patient.  相似文献   
39.
40.
Peresters dissociate thermally to alkoxy and acyloxy radicals. The acyloxy radical may dissociate further into an aryl radical and carbon dioxide. Alternatively they may break into these products in a single stage reaction. The decomposition of tert-butyl perbenzoate has been studied and it has been shown that the primary products of the dissociation of this ester are alkoxy and acyloxy radicals. The polymerization of styrene, using tert-butyl perbenzoate, tert-butyl percinnamate and tert-butyl percrotonate has been studied at 120 ± 1°C. It has been shown that the rate of polymerization is proportional to the square root of the initiator concentration and the 3/2 power of the monomer concentration.  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