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   4319篇
  免费   310篇
  国内免费   14篇
耳鼻咽喉   41篇
儿科学   106篇
妇产科学   114篇
基础医学   493篇
口腔科学   66篇
临床医学   460篇
内科学   1277篇
皮肤病学   92篇
神经病学   342篇
特种医学   150篇
外科学   670篇
综合类   37篇
预防医学   199篇
眼科学   65篇
药学   344篇
中国医学   2篇
肿瘤学   185篇
  2023年   25篇
  2022年   41篇
  2021年   67篇
  2020年   46篇
  2019年   62篇
  2018年   79篇
  2017年   60篇
  2016年   78篇
  2015年   88篇
  2014年   127篇
  2013年   142篇
  2012年   201篇
  2011年   234篇
  2010年   124篇
  2009年   107篇
  2008年   190篇
  2007年   238篇
  2006年   187篇
  2005年   209篇
  2004年   191篇
  2003年   187篇
  2002年   188篇
  2001年   163篇
  2000年   153篇
  1999年   127篇
  1998年   58篇
  1997年   50篇
  1996年   40篇
  1995年   31篇
  1994年   28篇
  1993年   27篇
  1992年   90篇
  1991年   61篇
  1990年   59篇
  1989年   83篇
  1988年   58篇
  1987年   76篇
  1986年   62篇
  1985年   53篇
  1984年   48篇
  1983年   38篇
  1982年   35篇
  1981年   27篇
  1979年   27篇
  1978年   22篇
  1977年   26篇
  1976年   27篇
  1975年   29篇
  1974年   37篇
  1971年   27篇
排序方式: 共有4643条查询结果,搜索用时 31 毫秒
51.
Screening methods for thyroid hormone disruptors   总被引:15,自引:0,他引:15  
The U.S. Congress has passed legislation requiring the EPA to implement screening tests for identifying endocrine-disrupting chemicals. A series of workshops was sponsored by the EPA, the Chemical Manufacturers Association, and the World Wildlife Fund; one workshop focused on screens for chemicals that alter thyroid hormone function and homeostasis. Participants at this meeting identified and examined methods to detect alterations in thyroid hormone synthesis, transport, and catabolism. In addition, some methods to detect chemicals that bind to the thyroid hormone receptors acting as either agonists or antagonists were also identified. Screening methods used in mammals as well as other vertebrate classes were examined. There was a general consensus that all known chemicals which interfere with thyroid hormone function and homeostasis act by either inhibiting synthesis, altering serum transport proteins, or by increasing catabolism of thyroid hormones. There are no direct data to support the assertion that certain environmental chemicals bind and activate the thyroid hormone receptors; further research is indicated. In light of this, screening methods should reflect known mechanisms of action. Most methods examined, albeit useful for mechanistic studies, were thought to be too specific and therefore would not be applicable for broad-based screening. Determination of serum thyroid hormone concentrations following chemical exposure in rodents was thought to be a reasonable initial screen. Concurrent histologic evaluation of the thyroid would strengthen this screen. Similar methods in teleosts may be useful as screens, but would require indicators of tissue production of thyroid hormones. The use of tadpole metamorphosis as a screen may also be useful; however, this method requires validation and standardization prior to use as a broad-based screen.  相似文献   
52.
Innovative interdisciplinary education in allied health has been developed in order to give students insight into role competencies of other professionals, improve the quality of health care while reducing costs, and facilitate the interdependent functioning of allied health care providers in meeting patient or client needs. The process of interdisciplinary course development requires the same communication and needs identification by faculty as is necessary for the provision of team care by practitioners. A retrospective account of interdisciplinary course development in a major health sciences center, together with materials developed for class presentation, may serve to encourage this type of activity elsewhere.  相似文献   
53.
Authors of the article "Financing Family Planning Services: Is Categorical Legislation Still Needed?" in the September-December 1991 issue of the American Journal of Gynecological Health, respond to a charge by the Executive Director of the Los Angeles Regional Family Planning Council that data presented on California's 1987 expenditures for family planning services were erroneous. Data presented in the article were obtained and reprinted from a 1988 article in Family Planning Perspectives by Rachel Benson Gold and Sandra Guardado. The figure of $27,000 was for contraceptive services exclusive of expenditures for sterilization, infertility, or extraclinical education. This figure was later adjusted in Volume 21 of Family Planning Perspectives to $27 million. Accordingly, total state funds spent nationwide was $76 million and national expenditures were $412 million. The authors were unaware of these corrections when their article went to press and thank their critic for bringing attention to the error. Even so, the author's original conclusion holds that categorical legislation is needed for family planning.  相似文献   
54.
Federal and state funds have provided for family planning services in American since the 1960s. Since 1976, services have been funded principally through federal statutes Title X of the Public Health Service Act and Titles V, XIX, and XX of the Social Security Act as well as various state appropriations. While these statutes aim to ensure that women of lower socioeconomic status enjoy access to reproductive health care services, levels of public expenditure in this area vary widely among states. In 1987, public family planning expenditures/woman at risk ranged from $60.16 in Wisconsin to $9.41 in Florida. Within this range of expenditures, the relative importance of each funding source per state varies widely. States with the most robust Title XIX programs, Medicaid, however, have highest per woman family planning expenditures. Upon reviewing the complement of public funding sources and how they are spent at the state level, the authors argue that categorical legislation is still needed to protect access to contraceptive services in America. In particular, of funds from supporting statues, Medicaid is distributed most equitable across the country. These funds paid for 36% of all public outlays for family planning in 1987. Without categorical legislation, however, Medicaid is insufficient to maintain the national family planning effort; the 1987 contribution of $10.49/woman at risk of unwanted pregnancy was insufficient to provide minimum services. Title X requires grantees to follow regulations which ensure state uniformity of quality and service distribution; submission of annual 5-year plans to Congress on how family planning goals will be achieved; and also authorizes monies for training and research. Despite political attacks, family planning funding must remain separate from maternal and child health programs. Such independence will keep these services politically visible; allow use of the more extensive family planning delivery system; catalyze states to spend other monies on family planning; and fuel innovations in service delivery, client education, and new contraceptive technologies. Title X should even be reauthorized under more precise mandates and include a national data collection system, consideration of the shortage of clinicians, and codification of 1981 guidelines reversed by the gag rule.  相似文献   
55.
The feasibility of fragmentation of salivary stones by a new extracorporeal piezoelectric lithotripter was investigated. A total of 40 salivary stones were submitted to piezoelectric shock wave treatment. The diameter, weight, and volume of all the stones were determined prior to shock wave administration. After shock wave administration the chemical composition of the stones was investigated by X-ray diffractometry. Fragmentation was achieved in 35 out of the 40 (87.5%) stones. Twenty-five of the 40 (62.5%) stones were disintegrated "therapeutically adequate" (residual fragments less than 1.5 mm). A statistically significant correlation was not observed between the number of discharges required for disintegration and the diameter, weight, volume, or the chemical composition of the stones.  相似文献   
56.
On the basis of earlier experiments showing a differential deficit of aphasics in picture sorting and matching tasks, two experiments were conducted to test the conjecture of a specific deficit of aphasics in the analytical appraisal of individual features. Broca's and Wernicke's aphasics-according to clinical diagnoses and the Aachener Aphasie Test-were compared with patients having right-hemisphere lesions or left-hemisphere lesions without aphasia. Both groups of aphasics differed from the control groups in the sorting task, irrespective of the sorting criterion, but the differences were small. The picture matching task did not discriminate between groups. Obviously, the basic assumption has to be modified with respect to specific conditions of task requirements. The experimental literature is reviewed.This research was supported by a Research Grant from the Deutsche Forschungsgemeinschaft.The research was conducted at the following clinics and rehabilitation centers. We are grateful for their support: Abteilung Neurologie der Med. Fak., RWTH, Aachen. Poliklinik für Stimm-und Sprachkranke, Universitätsklinikum Steglitz, Freie Universität Berlin. Neurologisches Rehabilitationszentrum Godeshöhe e. V., Bonn. Rheinische Landesklinik für Sprachgestörte, Bonn. Neurologische Klinik der Universität Ulm, Dietenbronn. Kliniken Schmieder, Gailingen und Allensbach. Max-Planck-Institut für Psychiatrie, München. Neurologiches Krankenhaus, München. Neurologisches und Hirneverletzten-Versorgungskrankenhaus, Tübingen.We are also most grateful for the kind help of K. Willmes, Aachen, in carrying out the discriminant analyses to classify the aphasics on the basis of the Aachener Aphasie Test.  相似文献   
57.
Hereditary neuropathy with liability to pressure palsies   总被引:1,自引:0,他引:1  
Summary Clinical, neurophysiological and pathological investigations were carried out in 11 affected members of 2 families with hereditary neuropathy with liability to pressure palsies (HNPP). The observations were related to findings in 261 cases of 47 families published in the literature. It was concluded that HNPP is a nosological entity characterized by the following diagnostic criteria: (1) an autosomal dominant inheritance; (2) the clinical presentation of a recurrent mononeuropathy simplex or multiplex, frequently related to an inadequate trauma to peripheral nerves; (3) a significant slowing of motor and sensory conduction velocity in clinically affected, but also in clinically unaffected nerves; (4) characteristic morphological findings in sural nerve biopsy featuring tomaculous swellings of myelin sheaths, transnodal myelination and segmental demyelination. The pathogenesis of HNPP is not clear. Hypothetical explanations of the pathogenesis of HNPP are discussed.In memory of Albert Bischoff (1921–1981), Professor of Neurology, University of Berne  相似文献   
58.
    
Zusammenfassung In 10 Jahren werden 130 Kinder wegen eines Dunndarmileus operiert. In 45 Fallen war die Ursache des Dunndarmileus eine vorausgegangene Laparotomie. Bei 13 dieser 45 Relaparotomien mußte erneut eine Laparotomie durchgeführt werden. In 40 % der Relaparotomiefälle war ein durchblutungsgestörter Darm die Ursache dafür. Funktions- and durchblutungsgestörte, dilatierte, hypertrophierte and atonische Darmanteile, die für die normale Peristaltik ungeeignet sind, sollen durch eine erweiterte Resektion des Dünndarms reseziert werden (Anastomose vitaler Diinndarmabschnitte).  相似文献   
59.
Summary Serial nerve biopsies were performed at an early, and at an advanced stage of the disease in 2 patients with progressive neural muscular atrophy. The early biopsy showed a complete loss of the large diameter and thickly myelinated fibres, as well as an expansion of the endoneurial interstitium in both cases. Myelinated and unmyelinated fibres exhibited axonal degeneration in all biopsies occasionally. Onion bulb formation, a typical feature of peripheral neuropathy in neural muscular atrophy, was found to be prominent only in the latter biopsies. As regards the formal pathogenesis of hypertrophic neuropathy in neural muscular atrophy, axonal dystrophy and interstitial changes of the endoneurium were regarded as primary phenomena, demyelination and onion bulb formation as secondary. A possible causal relation between axonal dystrophy and interstitial changes, observed in these cases, is discussed in the light of the present literature.
Zusammenfassung Bei 2 Patienten mit progressiver neuraler Muskelatrophie wurden Nervenbiopsien jeweils in einem frühen und in einem fortgeschrittenerem Stadium der Erkrankung entnommen und verglichen. In beiden Fällen zeigten bereits die frühen Biopsien ein völliges Fehlen der großkalibrigen, dickbemarkten Axone. Ebenfalls als frühe Veränderung wurde eine Erweiterung des endoneuralen Interstitiums festgestellt. Eine geringe Anzahl der vorhandenen bemarkten und unbemarkten Axone in allen Biopsien wies degenerative Veränderungen auf. Die für die progressive neurale Muskelatrophie typische Zwiebelschalenbildung der Schwannschen Zellen — möglicherweise eine Reaktion auf wiederholte De-und Remyelinisierungsvorgänge um dystrophische Axone — trat erst in den späteren Biopsien deutlicher hervor. Hinsichtlich der formalen Genese der hypertrophischen Neuropathie bei neuraler Muskelatrophie sind nach diesen Beobachtungen axonale Dystrophie und interstitielle Veränderungen des Endoneuriums als primäre Entmarkung und Zwiebelschalenbildung als sekundäre Phänomene zu betrachten. Die Möglichkeit einer kausalen Beziehung zwischen axonaler Dystrophie und interstitiellen Veränderungen wird an Hand der vorliegenden Befunde und Literatur diskutiert.
  相似文献   
60.
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