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   4980篇
  免费   433篇
  国内免费   23篇
耳鼻咽喉   63篇
儿科学   182篇
妇产科学   192篇
基础医学   801篇
口腔科学   107篇
临床医学   382篇
内科学   833篇
皮肤病学   80篇
神经病学   396篇
特种医学   268篇
外科学   669篇
综合类   54篇
一般理论   6篇
预防医学   457篇
眼科学   259篇
药学   361篇
中国医学   5篇
肿瘤学   321篇
  2022年   45篇
  2021年   81篇
  2020年   51篇
  2019年   79篇
  2018年   93篇
  2017年   65篇
  2016年   79篇
  2015年   100篇
  2014年   129篇
  2013年   184篇
  2012年   238篇
  2011年   270篇
  2010年   141篇
  2009年   131篇
  2008年   224篇
  2007年   242篇
  2006年   226篇
  2005年   233篇
  2004年   178篇
  2003年   199篇
  2002年   154篇
  2001年   143篇
  2000年   156篇
  1999年   100篇
  1998年   49篇
  1997年   44篇
  1996年   41篇
  1995年   43篇
  1994年   44篇
  1992年   85篇
  1991年   89篇
  1990年   106篇
  1989年   95篇
  1988年   91篇
  1987年   104篇
  1986年   72篇
  1985年   107篇
  1984年   75篇
  1983年   67篇
  1982年   42篇
  1981年   44篇
  1979年   53篇
  1978年   50篇
  1977年   50篇
  1975年   37篇
  1974年   32篇
  1973年   45篇
  1972年   41篇
  1967年   31篇
  1966年   38篇
排序方式: 共有5436条查询结果,搜索用时 15 毫秒
91.
A curriculum guide entitled "Heart Health Curriculum Guide" was developed with and by teachers in Peabody Public Schools under a Massachusetts Public Health grant to the American Heart Association. The 67-page manual describes the format of the 12-hour teacher workshop, background physiology of heart/circulatory system, hypertension risk factors, a set of 20 lessons, and evaluating procedures. (Copies may be obtained for $3.00 by writing the corresponding author.) As a result of teaching this unit, sixth grade students in each school ran a Blood Pressure Screening Clinic for their parents and school staff.  相似文献   
92.
Near infrared (NIR) spectroscopy spectra can be converted mathematically to precise quantitative information of chemical and physical nature by multivariate calibration. This makes NIR analysis useful for a variety of "difficult" sample types (powders, slurries), more or less without any sample preparation. The paper emphasizes the importance of using prior knowledge for spectral preprocessing of spectral data prior to the linear multivariate calibration modelling. Two new preprocessing methods are presented: extended multiplicative signal correction (EMSC) for elimination of uncontrollable path length or scattering effects, and spectral interference subtraction (SIS) for elimination of known spectral interferences. Determination of toluene in mixtures with benzene and xylene from NIR spectra with gross simulated light scattering effects is used for illustration.  相似文献   
93.
This paper addresses the question of the degree of agreement between experienced assessors making level-of-care placement decisions for the same client, given a comparable opportunity to obtain and record client information in a community-based Long-Term Care program.A systematic sample of 246 cases was selected, consisting of 47 preadmission assessments and 199 reviews. The resulting data were subjected to analysis using the statistic Kappa and the degree of agreement categories suggested by Fleiss.1 It was found that at the level-of-care extremes— Extended Care and Personal Care—the agreement between two nurse assessors for reviews could be considered excellent. In the Intermediate Care range, however, the reliability of the level-of-care decision can only be considered fair. Agreement for initial assessments was less, withK=0.469 indicating, overall, only fair agreement. While there was most often only a one-care-level difference between assessors, the program assessor tended to recommend a higher level than the study or check assessor. This has implications for funding agencies and/or facility planners who must assess the likely care requirements of an increasing number of disabled elderly. From a program management perspective, the preceding analyses allow an objective judgement of the extent of the placement decision problem, if any, and further provide a definition of areas most in need of revision. The value of collaboration between practitioner and researcher is evident in these analyses.Dr. Stark is Director, Division of Health Services Research and Development and Assistant Professor, Department of Health Care and Epidemiology, The University of British Columbia. Dr. Gutman is Director, Gerontology Centre and Associate Professor, Faculty of Interdisciplinary Studies, Simon Fraser University. Dr. Brothers is Research Associate, Division of Health Systems, The University of British Columbia. Address enquiries to Dr. A. Stark, Director, Division of Health Services Research and Development, Office of the Coordinator of Health Sciences, The John F. McCreary Health Sciences Centre, 2194 Health Sciences Mall, The University of British Columbia, Vancouver, B.C., V6T 1Z6.The research described in this paper, as well as the larger study of which it is a part, is supported by a grant from the B.C. Health Care Research Foundation. In addition, the cooperation and support of the Ministry of Health, Province of British Columbia is gratefully acknowledged.  相似文献   
94.
Health care consumers use a plethora of services which are accessible on an ambulatory basis. These include the services of pharmacists, optometrists, nurses, dentists, audiologists, orthotics, and so forth. Since many of these services are provided in physically and financially separate facilities and often are not located in close proximity to one another, consumers may spend a large amount of time traveling between locations. Economic inefficiencies due to the size and dispersion of separate and independent facilities may produce an increase in the cost of ambulatory health care services. Thus, the concept of a health care center, an ambulatory health care analog to the multispecialty shopping center, is proposed as a potential alternative and improvement in the delivery of these services. Space, location, personnel, and initial capital requirements for a model health care center are projected based on existing data for the establishment of each separate auxiliary health care facility. Projections are made to determine the appropriate and necessary site for the health care center's trade area. Potential revenues are calculated by examining some pharmacy operations which are beginning to pioneer these areas and utilizing revenue figures for the various individual services. The results indicate that the pharmacy, as a frequently visited health care facility, may be an excellent choice around which to develop the health care center concept in metropolitan areas.  相似文献   
95.
Previous studies employed a second-order schedule paradigm maintained by cocaine reinforcement to show that BP897, a dopamine D(3) partial agonist, selectively modulated drug-seeking behavior. We investigated its effect on drug-seeking behavior induced by presentation of stimuli associated with and predictive of cocaine availability after a period of extinction and in the absence of any further cocaine. Male rats were trained to associate discriminative stimuli (S(D)) with the availability of intravenous (i.v.) 0.25 mg/0.1 ml/infusion cocaine (S(D+)) or no-reward (S(D-)) saline solution. Each infusion of cocaine or saline was followed by a response-cue signaling 20-s time-out (TO). After meeting the self-administration training criterion rats were placed on extinction conditions during which i.v. solutions and S(D)s were withheld. Every other 3 days on which rats met the extinction criterion, reinstatement tests were conducted, presenting the S(D+) or S(D-) noncontingently together with a contingent presentation of cocaine- or saline-cues signaling 20-s TO. Regardless of the order of presentation or the nature of the stimuli (auditory or visual), cocaine-associated but not saline-associated stimuli reinstated responding on the previously active lever. Presentation of cocaine-associated stimuli induced lasting drug-seeking behavior for at least eight test sessions. BP897 (1.0 mg/kg i.p.) significantly attenuated this behavior. Since it has been reported that BP897 can interact with a panel of different receptors with high affinity, we evaluated the effects of 7-OH-DPAT, an agonist to D(3) receptors, raclopride, a preferential antagonist to D(2) receptors, and WAY 100,635, an antagonist at 5-HT(1A) receptors, on drug-seeking behavior. 7-OH-DPAT (0.1-3.0 mg/kg i.p.) had biphasic effects on reinstatement induced by the cocaine-associated cues, low dosages reducing and high dosages increasing the impact of cocaine-associated stimuli on rats' behavior. Raclopride (0.1, 0.3 mg/kg s.c.) completely prevented drug-seeking behavior induced by the reintroduction of cocaine-associated stimuli. WAY 100,635 (0.1-1.0 mg/kg s.c.) had no effect on this behavior. These results, while confirming that the partial agonist at the D(3) receptors, BP897, might be a useful medication, also suggest a role of D(2) receptors in cue-induced cocaine-seeking behavior.  相似文献   
96.
A variety of reasons can afflict wound healing. Current research is focussed on the acceleration of wound healing by stimulating molecular processes. Gene therapy may offer completely new ways to treat chronic wounds. Possible advantages of gene therapeutic modulation of wound healing might be a long term efficiency, systemic or local regulation of gene expression and low side-effects. Current goals comprise the improvement of transfection efficiency and specificity. In vivo applications are therefore focussed on optimized inducible or even cell-type specific promotors, as well as on improved local application techniques. Studies from our laboratory demonstrate the possibility to combine modern cell culture techniques with different types of gene transfer. This enables the simultaneous grafting of manipulated cells to the wound with the continuous delivery of specific proteins of interest. Experimentally, this lead to accelerated closure of partial and full thickness animal wounds. Clinically, gene therapy for the treatment of chronic wounds seems to be a realistic goal within the next years and might be applicable for a variety of novel indications.  相似文献   
97.
98.
99.
Background and purpose — Classification of ankle fractures is crucial for guiding treatment but advanced classifications such as the AO Foundation/Orthopedic Trauma Association (AO/OTA) are often too complex for human observers to learn and use. We have therefore investigated whether an automated algorithm that uses deep learning can learn to classify radiographs according to the new AO/OTA 2018 standards.Method — We trained a neural network based on the ResNet architecture on 4,941 radiographic ankle examinations. All images were classified according to the AO/OTA 2018 classification. A senior orthopedic surgeon (MG) then re-evaluated all images with fractures. We evaluated the network against a test set of 400 patients reviewed by 2 expert observers (MG, AS) independently.Results — In the training dataset, about half of the examinations contained fractures. The majority of the fractures were malleolar, of which the type B injuries represented almost 60% of the cases. Average area under the area under the receiver operating characteristic curve (AUC) was 0.90 (95% CI 0.82–0.94) for correctly classifying AO/OTA class where the most common major fractures, the malleolar type B fractures, reached an AUC of 0.93 (CI 0.90–0.95). The poorest performing type was malleolar A fractures, which included avulsions of the fibular tip.Interpretation — We found that a neural network could attain the required performance to aid with a detailed ankle fracture classification. This approach could be scaled up to other body parts. As the type of fracture is an important part of orthopedic decision-making, this is an important step toward computer-assisted decision-making.

Ankle fractures are recognized among the most common fractures, with peak incidence between 15 and 29 years (67 per 100,000 person-years) and elderly women ≥ 60 years (174 per 100,000 person-years) (Westerman and Porter 2007, Thur et al. 2012). Efforts to classify ankle fractures in clinically relevant entities have a long history, ending in 3 classic systems, i.e., the Lauge-Hansen (Hansen 1942), Danis–Weber, and the AO/OTA classifications (Association Committee for Coding and Classification 1996; Budny and Young 2008), where the Danis–Weber with its A, B, and C classes is probably the most used in everyday practice.The most recent update for the AO/OTA classification system was published in 2018 (Meinberg et al. 2018). The AO/OTA system contains classifications for the entire body. The ankle is divided into (1) malleolar, (2) distal tibia, and (3) fibular fractures. For malleolar fractures, the subcategories correspond to the Danis–Weber ABC classification (Hughes et al. 1979) with the addition of a suffix of 2 digits (range 1–3), e.g., the common intra-syndesmotic B-injury without widening of the mortise corresponds to the B1.1 class. The numbers correspond roughly to the severity of each fracture.The complexity of this classification makes it difficult to learn and apply, limiting inter-observer reliability and reproducibility (Fonseca et al. 2017). This has hindered its use in an everyday clinical setting, suggesting the need for better aid during the classification.During recent years, the resurgence of neural networks, a form of artificial intelligence (AI), has proven highly successful for image classification. In some medical image classification applications neural networks attain (Olczak et al. 2017, Kim and MacKinnon 2018, Gan et al. 2019), and surpass, human expert performance (Esteva et al. 2017, Lee et al. 2017, Chung et al. 2018, Urakawa et al. 2019). Machine learning and neural networks are also becoming more commonplace research tools in orthopedics. They hold great potential, as the diagnostic underpinning and intervention decision relies heavily on medical imaging (Cabitza et al. 2018). The strength of these learning algorithms is their ability to review a vast number of examinations and examples, and the speed and consistency with which they can review each examination and at the same time remember thousands of categories without issue.We therefore hypothesized that a neural network can learn to classify ankle fractures according to the AO/OTA 2018 classification from radiographs.  相似文献   
100.
##正##On July 31, 2012, The Miami Project to Cure Paralysis at the University of Miami Miller School of Medicine received permission from the Food and Drug Administration(FDA) to begin a Phase I clinical trial to evaluate the safety of transplanting human autologous Schwann cells to treat patients with spinal cord injuries. This is the only FDA-approved cell therapy-based clinical trial for sub-acute spinal cord injury in the United States.  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