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   8951篇
  免费   579篇
  国内免费   48篇
耳鼻咽喉   97篇
儿科学   217篇
妇产科学   165篇
基础医学   1215篇
口腔科学   1163篇
临床医学   662篇
内科学   1869篇
皮肤病学   225篇
神经病学   561篇
特种医学   379篇
外科学   923篇
综合类   105篇
预防医学   924篇
眼科学   170篇
药学   569篇
中国医学   87篇
肿瘤学   247篇
  2023年   90篇
  2022年   227篇
  2021年   331篇
  2020年   251篇
  2019年   296篇
  2018年   383篇
  2017年   227篇
  2016年   276篇
  2015年   340篇
  2014年   426篇
  2013年   543篇
  2012年   686篇
  2011年   778篇
  2010年   381篇
  2009年   348篇
  2008年   443篇
  2007年   507篇
  2006年   397篇
  2005年   304篇
  2004年   232篇
  2003年   180篇
  2002年   183篇
  2001年   144篇
  2000年   132篇
  1999年   138篇
  1998年   96篇
  1997年   80篇
  1996年   66篇
  1995年   41篇
  1994年   55篇
  1993年   48篇
  1992年   50篇
  1991年   64篇
  1990年   49篇
  1989年   84篇
  1988年   56篇
  1987年   64篇
  1986年   53篇
  1985年   35篇
  1984年   43篇
  1983年   32篇
  1982年   32篇
  1981年   24篇
  1980年   20篇
  1979年   19篇
  1977年   23篇
  1976年   20篇
  1975年   28篇
  1970年   24篇
  1968年   23篇
排序方式: 共有9578条查询结果,搜索用时 15 毫秒
991.
The National Laboratory for Metrology of Ionizing Radiation (LNMRI)/Brazil participated in the last (57)Co activity measurement comparison organized by IAEA, in 2008. This was made in order to realize primary standardization of this radionuclide and to reduce the measuring uncertainties in the laboratory. Additionally, one sample with 2.6g was taken from the IAEA master solution of (57)Co and was prepared to be used in the measurement of the radionuclide's half-life in an ionization chamber system. The (57)Co half-life was measured to be 271.82 (17) days.  相似文献   
992.
Watson & Ballet and Vender staging systems are widely known for classifying SNAC wrist osteoarthritis. Despite of its day-to-day use, no assessment for its agreement was performed. To Evaluate the intra and interobserver agreement for these classification systems. Forty-eight posteroanterior wrist radiographs from patients with osteoarthritis due to scaphoid nonunion were evaluated at two occasions??in a 1?week interval??by five observers with different expertise??hand surgeons, hand surgery residents, orthopedic surgeons and orthopedic surgery residents. They rated osteoarthritis stages according to the above-cited systems. Kappa statistics were performed for measuring agreement. Unsatisfactory (Cohen??s Kappa <0.5) agreement was found for all intra and inter observer measures for both systems. There was no clear correlation between expertise and kappa values. Unsatisfactory agreement was found for both classifications, despite the evaluator expertise. A rationale of a more reliable classification is needed.  相似文献   
993.
ABSTRACT: BACKGROUND: Few studies demonstrate effectiveness of therapies for oral rehabilitation of patients with cerebral palsy (CP), given the difficulties in chewing, swallowing and speech, besides the intellectual, sensory and social limitations. Due to upper airway obstruction, they are also vulnerable to sleep disorders. This study aims to assess the sleep variables, through polysomnography, and masticatory dynamics, using electromiography, before and after neuromuscular electrical stimulation, associated or not with low power laser (Gallium Arsenide- Aluminun, = 780nm) and LED ( = 660 nm) irradiation in CP patients. Methods/Design: 50 patients with CP, both gender, aged between 19 and 60 years will be enrolled in this study. The inclusion criteria are: voluntary participation, patient with hemiparesis, quadriparesis or diparetic CP, with ability to understand and respond to verbal commands. The exclusion criteria are: patients undergoing / underwent orthodontic, functional maxillary orthopedic or botulinum toxin treatment. Polysomnographic and surface electromyographic exams on masseter, temporalis and suprahyoid will be carry out in all sample. Questionnaire assessing oral characteristics will be applied. The sample will be divided into 5 treatment groups: Group 1: neuromuscular electrical stimulation; Group 2: laser therapy; Group 3: LED therapy; Group 4: neuromuscular electrical stimulation and laser therapy and Group 5: neuromuscular electrical stimulation and LED therapy. All patients will be treated during 8 consecutive weeks. After treatment, polysomnographic and electromiographic exams will be collected again. Discussion: This paper describes a five arm clinical trial assessing the examination of sleep quality and masticatory function in patients with CP under non-invasive therapies.  相似文献   
994.
995.
Objectives: Suture materials are widely used in urology. The interaction of these materials with the extracellular matrix in the inflammatory process can be estimated by stereology of collagen fibers and the present study was designed to determine the behavior of the bladder tissue of rats to grafts of the biopolymer of sugar cane (BPCA), and the inflammation and intravesical stone formation compared to the polyglactin 910. Materials and Methods: 42 Wistar rats were divided in four groups: Group I (n = 10) rats submitted to bladder implantation of ~4-0 BPCA suture graft and euthanized at 4 weeks; Group II (n = 10) rats submitted to bladder implantation of 4-0 polyglactin 910 suture graft and euthanized at 4 weeks; Group III (n = 12) rats submitted to bladder implantation of ~4-0 BPCA suture graft and euthanized at 8 weeks; Group IV (n = 10) rats submitted to bladder implantation of 4-0 polyglactin 910 suture graft and euthanized at 8 weeks. Bladders collected at necropsy were analyzed for their weight and the presence of grafts and calculi. Sections were prepared for stereological analysis of collagen fibers. Results: The bladder weight was higher in group I, particularly in the presence of bladder stones. The presence of the graft was observed in 100 % (group I), 80 % (group II), 91.6 % (group III) and 30 % (group IV); polyglactin 910 showed an absorption of 70 % in this period. The stereological analysis showed a higher volume density of collagen fibers in group I versus other groups (p < 0.001). Conclusion: The BPCA was a material with good integration into the bladder of rats; its absorption was slower than that of the polyglactin 910. The presence of urinary stones was lower in bladders with implantation of BPCA, particularly after 8 weeks. There was a greater initial inflammatory response to BPCA graft that was directly related to the increase in bladder weight and the presence of urinary stones, but that equalized the results of polyglactin 910 after 8 weeks.  相似文献   
996.
997.
ABSTRACT: Pregnancy affects both the maternal and fetal metabolism and even in nondiabetic women exerts a diabetogenic effect. Among pregnant women, 2 to 17.8% develop gestational diabetes. Pregnancy can also occur in women with preexisting diabetes, that can predispose the fetus to many alterations in organogenesis, growth restriction and the mother to some diabetes-related complications like retinopathy and nephropathy or accelerate the course of these complications if they are already present. Women with gestational diabetes generally start their treatment with diet and lifestyle modification; when these changes fail in keeping an optimal glycemic control, then insulin therapy must be considered. Women with type 2 diabetes in use of oral hypoglycemic agents are advised to change to insulin therapy. Those with preexisting type 1 diabetes must start an intensive glycemic control, preferably before conception. All these procedures are performed aiming to keep glycemic levels normal or near-normal as possible to avoid the occurrence of adverse perinatal outcomes to the mother and to the fetus. The aim of this review is to reinforce the need to improve the knowledge on reproductive health of women with diabetes during gestation and to understand what are the reasons for them failing to attend for prepregnancy care programs, and to understand the underlying mechanisms of adverse fetal and maternal outcomes, which in turn may lead to strategies for its prevention.  相似文献   
998.
To investigate the effects of age and disease on endogenous cardiac progenitor cells, we obtained right atrial and left ventricular epicardial biopsies from patients (n?=?22) with chronic ischaemic heart disease and measured doubling time and surface marker expression in explant- and cardiosphere-derived cells (EDCs, CDCs). EDCs could be expanded from all atrial biopsy samples, but sufficient cells for cardiosphere culture were obtained from only 8 of 22 ventricular biopsies. EDCs from both atrium and ventricle contained a higher proportion of c-kit+ cells than CDCs, which contained few such cells. There was wide variation in expression of CD90 (atrial CDCs 5-92?% CD90+; ventricular CDCs 11-89?% CD90+), with atrial CDCs cultured from diabetic patients (n?=?4) containing 1.6-fold more CD90+ cells than those from non-diabetic patients (n?=?18). No effect of age or other co-morbidities was detected. Thus, CDCs from atrial biopsies may vary in their therapeutic potential.  相似文献   
999.
1000.

Objective

The purpose of this study was to analyse the use of digital tools for image enhancement of mandibular radiolucent lesions and the effects of this manipulation on the percentage of correct radiographic diagnoses.

Methods

24 panoramic radiographs exhibiting radiolucent lesions were selected, digitized and evaluated by non-experts (undergraduate and newly graduated practitioners) and by professional experts in oral diagnosis. The percentages of correct and incorrect diagnoses, according to the use of brightness/contrast, sharpness, inversion, highlight and zoom tools, were compared. All dental professionals made their evaluations without (T1) and with (T2) a list of radiographic diagnostic parameters.

Results

Digital tools were used with low frequency mainly in T2. The most preferred tool was sharpness (45.2%). In the expert group, the percentage of correct diagnoses did not change when any of the digital tools were used. For the non-expert group, there was an increase in the frequency of correct diagnoses when brightness/contrast was used in T2 (p=0.008) and when brightness/contrast and sharpness were not used in T1 (p=0.027). The use or non-use of brightness/contrast, zoom and sharpness showed moderate agreement in the group of experts [kappa agreement coefficient (κ)=0.514, 0.425 and 0.335, respectively]. For the non-expert group there was slight agreement for all the tools used (κ≤0.237).

Conclusions

Consulting the list of radiographic parameters before image manipulation reduced the frequency of tool use in both groups of examiners. Consulting the radiographic parameters with the use of some digital tools was important for improving correct diagnosis only in the group of non-expert examiners.  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