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   29025篇
  免费   1608篇
  国内免费   59篇
耳鼻咽喉   443篇
儿科学   1157篇
妇产科学   939篇
基础医学   4698篇
口腔科学   642篇
临床医学   2425篇
内科学   5788篇
皮肤病学   576篇
神经病学   2755篇
特种医学   1201篇
外国民族医学   16篇
外科学   4146篇
综合类   151篇
一般理论   4篇
预防医学   1591篇
眼科学   546篇
药学   1635篇
中国医学   21篇
肿瘤学   1958篇
  2022年   223篇
  2021年   386篇
  2020年   260篇
  2019年   351篇
  2018年   467篇
  2017年   384篇
  2016年   529篇
  2015年   514篇
  2014年   692篇
  2013年   908篇
  2012年   1295篇
  2011年   1378篇
  2010年   696篇
  2009年   730篇
  2008年   1255篇
  2007年   1345篇
  2006年   1268篇
  2005年   1296篇
  2004年   1106篇
  2003年   1090篇
  2002年   1012篇
  2001年   994篇
  2000年   1028篇
  1999年   878篇
  1998年   376篇
  1997年   296篇
  1996年   242篇
  1995年   222篇
  1994年   194篇
  1993年   192篇
  1992年   547篇
  1991年   587篇
  1990年   566篇
  1989年   468篇
  1988年   442篇
  1987年   460篇
  1986年   436篇
  1985年   439篇
  1984年   309篇
  1983年   252篇
  1982年   160篇
  1981年   181篇
  1979年   302篇
  1978年   224篇
  1977年   187篇
  1976年   173篇
  1975年   191篇
  1974年   239篇
  1973年   196篇
  1972年   175篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
121.
There are relatively few effective clinical options for preserving female fertility, particularly following aggressive chemotherapy and/or radiotherapy treatment protocols. This document reviews scientific background, current technology, clinical results, and potential future applications of ovarian tissue cryopreservation and transplantation. The technology is investigational although rapidly evolving, and the list of appropriate indications may be expanded in the future. Germany stays abreast of these rapid worldwide developments by having founded the first German network of experts for fertility preservation in patients undergoing chemotherapy and/or radiotherapy.  相似文献   
122.
The aim of this orthopaedic-biomechanical study was to evaluate lower leg muscle function in ankle osteoarthritis (OA) patients and muscle rehabilitation after the implantation of a total ankle replacement (TAR). Patients with a severe unilateral ankle OA were assessed with an orthopaedic and biomechanical examination before and one year after TAR surgery. Visual analogue pain score, American Orthopaedic Foot and Ankle Society (AOFAS) ankle score, ankle range of motion for dorsi- and plantar flexion (ROM DF/PF), and calf circumference difference between affected and contralateral healthy leg were measured. Isometric maximal voluntary torque for ankle dorsiflexion and plantar flexion were measured simultaneously with surface electromyography (EMG; mean frequency and intensity) of the anterior tibial, medial gastrocnemius, soleus, and peroneus longus muscle. Data were compared to a group of age- and gender-matched normal subjects. The mean calf circumference difference between legs did not significantly decrease from preoperative to one year follow-up. The mean dorsiflexion torque and plantar flexion torque of the affected ankle increased significantly. The atrophic muscles were characterized by a reduction of the mean EMG intensity and mean EMG frequency. In the rehabilitation process, the mean EMG intensity recovered and was not significantly different for all muscles, however, not for EMG frequency, which remained low and unchanged. This study reports for the first time in the literature the clinical and biomechanical facts of lower leg muscle atrophy in ankle OA as well as the amount of the muscle rehabilitation after a total ankle replacement. Patients with a symptomatic ankle OA achieve better function with a total ankle replacement; however, one year after the operation neuromuscular and biomechanical deficits may still be present.  相似文献   
123.
Orale Zytologie     
Zusammenfassung Die orale Zytologie erf?hrt eine Renaissance, die durch die Einführung der Bürste als Entnahmetr?ger und durch die Anwendung zus?tzlicher moderner Verfahren bedingt ist. Die Bürste kann tiefe Schichten der oralen Mukosa erfassen, in denen die squam?se intraepitheliale Neoplasie (SIN) beginnt. Zus?tzliche Verfahren zur Bewertung der biologischen Potenz der gewonnenen oralen Epithelzellen sind: die computerunterstützte Bildanalyse (OralCDx?), die DNA-Zytometrie, die Immunzytochemie, die Dünnschichtzytologie und molekularbiologische Analysen. Alle genannten Verfahren sind geeignet, die Sensitivit?t (bis zu 100%) und Spezifit?t (bis zu 100%) der oralen Zytologie zu erh?hen. Dennoch gibt es Berichte über orale Plattenepithelkarzinome, die mithilfe der Bürstenbiopsie nicht erkannt wurden. Die Wertigkeit der einzelnen Verfahren kann aktuell aufgrund fehlender vergleichender Studien nicht abschlie?end beurteilt werden. Die Immunzytochemie mit kommerziellen Antik?rpern gegen Laminin 5 ist allseits verfügbar und methodisch einfach. Das nichtinvasive diagnostische Verfahren der methodisch unterstützten oralen Bürstenbiopsie kann einen Beitrag zur frühen Erkennung ausgew?hlter Mundschleimhautl?sionen leisten. Ein positiver Befund oder eine Progression der L?sion bei negativem Befund sind Indikationen zur überweisung des Patienten an Fachkliniken und zur dort durchgeführten Skalpellbiopsie mit histopathologischer Untersuchung. Die histopathologische Begutachtung bleibt der Goldstandard in der definitiven Diagnostik maligner oraler L?sionen.   相似文献   
124.
125.
OBJECTIVE: To examine fetal (FHR) and neonatal heart rate patterns following use of common oral antihypertensives in pregnancy. METHODS: A systematic review of randomized controlled trials (RCTs), observational studies (N >/= 6 women), and animal studies. Data were abstracted (two reviewers) to determine relative risk (RR) (or risk difference (RD) for low event rates) and 95% CI. RESULTS: Eighteen RCTs (1858 women), one controlled observational study (N = 22), and seven case series (N = 117) were reviewed. Most hypertension was pregnancy-induced (N = 14 studies). The FHR was assessed by cardiotocogram (CTG) (N = 17 studies (visual interpretation); 1 study (computerized CTG), or umbilical artery velocimetry (N = 4). Four studies examined neonatal heart rate. In placebo-controlled RCTs (N = 192 women), adverse FHR effects did not differ between groups [9/101 (drugs) vs. 7/91 (placebo); RD 0.02, 95% CI (- 0.06, 0.11); chi2 = 1.02]. In six drug vs. drug RCTs (295 women), adverse FHR effects did not differ between groups [29/144 (methyldopa) vs. 42/151 (other drugs); RR 0.72, 95% CI (0.49, 1.07); chi2 = 0.69]. In one labetalol vs. placebo trial, neonatal bradycardia did not differ between groups [4/70 (labetalol) vs. 4/74 (placebo); OR 1.06, 95% CI (0.26, 4.39)], while in three drug vs. drug RCTs, neonatal bradycardia was not observed (0/24 vs. 0/26). CONCLUSIONS: Available data are inadequate to conclude whether oral methyldopa, labetalol, nifedipine, or hydralazine adversely affect fetal or neonatal heart rate and pattern. Until definitive data are available, FHR changes cannot be reliably attributed to drug effect, but may be due to progression of the underlying maternal or placental disease.  相似文献   
126.
Several human organs are not capable of functional regeneration following a tissue defect and react with scar formation. In stem cell transplantation, undifferentiated or partly differentiated precursor cells are applied to defective tissue for therapeutic regeneration. After promising preclinical investigations, the transplantation of autologous stem cells for myocardial infarction treatment is being transferred to clinical use. Mesenchymal stem cells and endothelial precursor cells derived from the bone marrow or circulating blood as well as skeletal myoblasts are employed in clinical trials. Furthermore, indications for cell transplantation and delivery routes vary considerably throughout current investigations. Initial results suggest a potential for restoration of cardiac function in stem cell-treated patients; however, the mechanisms are not fully understood. This overview will focus on objectives, recent achievements, and future perspectives of diverse stem cell transplantation approaches.  相似文献   
127.
Fluoroscopy is the most common tool for the intraoperative control of long-bone fracture reduction. Limitations of this technology include high radiation exposure for the patient and the surgical team, limited visual field, distorted images, and cumbersome verification of image updating. Fluoroscopy-based navigation systems partially address these limitations by allowing fluoroscopic images to be used for real-time surgical localization and instrument tracking. Existing fluoroscopy-based navigation systems are still limited as far as the virtual representation of true surgical reality is concerned. This article, for the first time, presents a reality-enhanced virtual fluoroscopy with radiation-free updates of in situ surgical fluoroscopic images to control metaphyseal fracture reduction. A virtual fluoroscopy is created using the projection properties of the fluoroscope; it allows the display of detailed three-dimensional (3D) geometric models of surgical tools and implants superimposed on the X-ray images. Starting from multiple registered fluoroscopy images, a virtual 3D cylinder model for each principal bone fragment is constructed. This spatial cylinder model not only supplies a 3D image of the fracture, but also allows effective fragment projection recovery from the fluoroscopic images and enables radiation-free updates of in situ surgical fluoroscopic images by non-linear interpolation and warping algorithms. Initial clinical experience was gained during four tibia fracture fixations that were treated by LISS (Less Invasive Stabilization System) osteosynthesis. In the cases operated on, after primary image acquisition, the image intensifier was replaced by the virtual reality system. In all cases, the procedure including fracture reduction and LISS osteosynthesis was performed entirely in virtual reality. A significant disadvantage was the unfamiliar operation of this prototype software and the need for an additional operator for the navigation system.  相似文献   
128.
129.
This paper gives an overview of the diagnostics and therapy of specific developmental language disorders. In addition, the present understanding of etiology and in particular genetics is discussed. For the classification of a specific language impairment both the linguistic and the general cognitive abilities have to be evaluated.For this purpose, standardised tests should be used instead of informal methods. Hearing impairment has to be ruled out for each language retarded child. If a decrease or stagnation of the language ability is observed, it is necessary to initiate detailed cerebral diagnostics. In the therapy the language symptoms must be directly treated,whereas a training of basic, non-linguistic abilities does not appear to be effective.Additional symptoms, in particular hyperactivity, conduct and emotional disorders, should be considered sufficiently in the treatment.Parents should be included in the therapeutic process more strongly than has been the case in the past.  相似文献   
130.
OBJECTIVE: An animal model has been designed to assess the feasibility of off-pump mitral valve replacement using valved stents. METHODS: Glutaraldehyde-preserved homograft was sutured inside a prosthetic tube (Dacron). Then, two self-expandable nitinol Z-stents were sutured on the external surface of the prosthesis in such a way to create two self-expanding crowns for fixation. In adult pigs and under general anesthesia, the left atrium was exposed through a left thoracotomy and atrio-ventricular roadmapping was performed with intravascular ultrasound (IVUS) and fluoroscopy. The double-crowned valved stents were loaded into a delivery sheath. The sheath was then introduced into the left atrium and the valved stents was deployed in mitral position in such a way that the part in between the two stents was at the level of the mitral annulus. Intracardiac Unltrasound (ICUS) was used to assess the valve function. Hemodynamic parameters were gathered as well. Animal survived for no more than 3h after the valve deployment and gross anatomy examination of the left heart was carried out. RESULTS: The mean height of the valved stents was 29.4+/-0.2 mm, with an internal diameter of 20.4+/-1.0mm, and an external diameter of 25.5+/-0.8 mm. The procedure was successfully carried out in eight animals. In vivo evaluation showed a native mitral annulus diameter of 24.9+/-0.6 mm, and a mean mitral valve area of 421.4+/-17.5 mm2. ICUS showed a mild mitral regurgitation in three out of eight animals. Mean pressure gradient across the valved stents was 2.6+/-3.1 mmHg. Mean pressure gradient across the left ventricular outflow tract (LVOT) was 6.6+/-5.2 mmHg. The mean survival time was 97.5+/-56.3 min (survival time range was 40-180 min). One animal died due to the occlusion of the LVOT because of valved stents displacement. Postmortem evaluation confirmed correct positioning of the valved stent in the mitral position in seven out of eight animals. No atrial or ventricular lesions due to the valved stents were found. CONCLUSIONS: Off-pump implantation of a self-expandable valved stent in the mitral position is technically feasible. Further studies will assess if this procedure is also feasible in humans.  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