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   217253篇
  免费   3146篇
  国内免费   366篇
耳鼻咽喉   1576篇
儿科学   7392篇
妇产科学   4240篇
基础医学   21514篇
口腔科学   3217篇
临床医学   15564篇
内科学   42728篇
皮肤病学   1572篇
神经病学   20092篇
特种医学   9952篇
外科学   35130篇
综合类   2467篇
一般理论   9篇
预防医学   20326篇
眼科学   3407篇
药学   11735篇
中国医学   737篇
肿瘤学   19107篇
  2023年   299篇
  2022年   634篇
  2021年   1464篇
  2020年   791篇
  2019年   1130篇
  2018年   23227篇
  2017年   18184篇
  2016年   20412篇
  2015年   2166篇
  2014年   2540篇
  2013年   3046篇
  2012年   10414篇
  2011年   24281篇
  2010年   20620篇
  2009年   13096篇
  2008年   22277篇
  2007年   24543篇
  2006年   3385篇
  2005年   4980篇
  2004年   5895篇
  2003年   6590篇
  2002年   4472篇
  2001年   523篇
  2000年   578篇
  1999年   436篇
  1998年   556篇
  1997年   517篇
  1996年   364篇
  1995年   374篇
  1994年   310篇
  1993年   219篇
  1992年   174篇
  1991年   181篇
  1990年   217篇
  1989年   157篇
  1988年   115篇
  1987年   94篇
  1986年   94篇
  1985年   98篇
  1984年   91篇
  1983年   85篇
  1982年   117篇
  1981年   66篇
  1980年   110篇
  1978年   55篇
  1976年   43篇
  1974年   49篇
  1938年   63篇
  1932年   59篇
  1930年   48篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
The treatment of deep cartilage defects in load-bearing joints is a problem that still has no satisfactory solution. Full-thickness defects of the articular cartilage rarely heal spontaneously, usually leaving damage that can lead to early arthrosis. Techniques currently available for the treatment of chondral defects include abrasion, drilling, micro-fracturing, transplantation of tissue autografts and allografts, and cell transplantation. Osteochondral autograft transplantation is currently the only surgical cartilage repair technique known to lead to the formation of genuine hyaline articular cartilage and its retention at least in the medium term. The Draenert method, in which a water-cooled diamond bone-cutting system is used, is an effective procedure for resurfacing the joints affected by localised cartilaginous defects, even when there is also severe bone loss. Donor-side morbidity can be kept to a minimum by filling the defect caused by harvesting with a press-fit cylinder of cancellous bone covered with periosteum for protection.  相似文献   
72.
Ischemic injury plays an important role in chronic renal transplant failure (CRTF). Down-regulation of ecto-adenosine triphosphatase (ATPase) in combination with up-regulation of ecto-5'-nucleotidase is a hallmark of ischemic injury. We studied the expression of renal ecto-5'-nucleotidase and ecto-ATPase in experimental renal transplantation. Fisher 344-to-Lewis allografted rats were either treated with an angiotensin-converting enzyme inhibitor (ACEi) or left untreated. Lewis-to-Lewis syngrafted rats served as controls. Untreated allografted rats developed proteinuria, glomerulosclerosis, and mild intimal hyperplasia. ACEi completely prevented focal and segmental glomerulosclerosis (FGS) and proteinuria, but significantly enhanced intimal hyperplasia. Untreated allografted rats revealed marked vascular ecto-5'-nucleotidase activity, which increased with ACEi. Vascular ecto-5'-nucleotidase activity was absent in syngrafted animals. Ecto-5'-nucleotidase activity correlated well with intimal hyperplasia. Glomerular ecto-ATPase expression was significantly reduced in untreated allografted rats compared to syngrafted rats and correlated well with the extent of FGS. ACEi prevented reduction in glomerular ecto-ATPase. We found de-novo expression of ecto-5'-nucleotidase at sites of renal intimal hyperplasia. Glomerular ecto-ATPase expression was markedly reduced in allografted rats and was prevented by ACEi. These enzyme expression patterns suggest local ischemic damage in experimental CRTF.  相似文献   
73.
Contemporary discourse contains numerous examples of use of the concept of culture by social and behavioral scientists. Simple reification, where the speaker makes culture into a thing capable of action exemplifies one usage in public discourse. Some quantitative social scientists attempt to characterize people’s cultural identities by means of a single categorical variable, which often “lumps” people into categories such as “Hispanic” or “Black” that in fact have numerous culturally bounded subcategories. Approaches that emphasize cultural process are preferable to those who attempt to categorize; more complex measures of acculturation help investigators to make convincing analyses of circumstances in which health disparities occur. Examples in which investigators make appropriate use of cultural characterizations demonstrate their utility in investigating health disparities in Haitian American women, injecting and noninjecting drug users, Hispanic youth, and adult Hispanics at risk of HIV infection. Focus on culture in the study of health disparities can identify entanglements between structural factors such as poverty and lack of education and cultural factors such as beliefs about health. Qualitative methods coupled with quantitative methods have great potential to improve investigators’ grasp of cultural nuance while capturing the distribution of qualitatively derived behaviors.  相似文献   
74.
75.
76.
Ureteral herniation is a rare entity. We report the first case of extraperitoneal ureteral herniation in a pediatric en bloc renal graft causing obstructive uropathy. A 70-year-old, obese patient with an en bloc renal transplant was found to have ureterohydronephrosis in the right renal graft on magnetic resonance imaging. Nephrostomy with insertion of a double-J catheter confirmed the presence of a ureteral loop within the inguinal tract. Surgery confirmed herniation of the ureter through the internal inguinal ring, crossing over the spermatic cord. We performed release, resection, ureteral reimplantation and hernioplasty. Four months later, renal function was normal and urinary tract dilation had diminished. This case illustrates an unusual cause of obstructive uropathy in a transplanted kidney. Apart from obesity, two other factors may have contributed to its development: presence of a redundant ureter, and the fact that the ureter had been placed over, rather than under, the spermatic cord.  相似文献   
77.
The specific characteristics of genetic data lead to ethical-legal conflicts in the framework of genetic diagnosis. Several international organisations, including UNESCO and the Council of Europe, have enacted rules referring to the use of genetic information. This paper discusses possible legal and ethical criteria that could be used in genetic testing.  相似文献   
78.
3D FEA of cemented steel, glass and carbon posts in a maxillary incisor.   总被引:12,自引:0,他引:12  
OBJECTIVES: A comparative study on the stress distribution in the dentine and cement layer of an endodontically treated maxillary incisor has been carried out by using Finite Element Analysis (FEA). The role of post and cement rigidity on reliability of endodontic restorations is discussed. METHODS: A 3D FEM model (13,272 elements and 15,152 nodes) of a central maxillary incisor is presented. A chewing static force of 10 N was applied at 125 degree angle with the tooth longitudinal axis at the palatal surface of the crown. Steel, carbon and glass fiber posts have been considered. The differences in occlusal load transfer ability when steel, carbon and glass posts, fixed to root canal using luting cements of different elastic moduli (7.0 and 18.7 GPa) are discussed. RESULTS AND SIGNIFICANCE: The more stiff systems (steel and carbon posts) have been evaluated to work against the natural function of the tooth. Maximum Von Mises equivalent stress values ranging from 7.5 (steel) to 5.4 and 3.6 MPa (respectively, for carbon posts fixed with high and low cement moduli) and to 2.2 MPa (either for glass posts fixed with high and low cement moduli) have been observed under a static masticatory load of 10 N. A very stiff post works against the natural function of the tooth creating zones of tension and shear both in the dentine and at the interfaces of the luting cement and the post. Stresses in static loading do not reach material (dentine and cement) failure limits, however, they significantly differ leading to different abilities of the restored systems to sustain fatigue loading. The influence of the cement layer elasticity in redistributing the stresses has been observed to be less relevant as the post flexibility is increased.  相似文献   
79.
80.

Introduction  

This paper presents the results of a study on the psychometric properties of an authorized Spanish version of the McMaster Family Assessment Device, a self-report measure of family functioning.  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