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   129773篇
  免费   6655篇
  国内免费   156篇
耳鼻咽喉   2288篇
儿科学   6382篇
妇产科学   4460篇
基础医学   16984篇
口腔科学   3777篇
临床医学   9307篇
内科学   24158篇
皮肤病学   3753篇
神经病学   9854篇
特种医学   5673篇
外国民族医学   32篇
外科学   22166篇
综合类   1741篇
一般理论   36篇
预防医学   6233篇
眼科学   3804篇
药学   8816篇
  1篇
中国医学   411篇
肿瘤学   6708篇
  2019年   850篇
  2018年   1328篇
  2017年   1151篇
  2016年   1531篇
  2015年   1540篇
  2014年   2112篇
  2013年   3102篇
  2012年   3875篇
  2011年   4064篇
  2010年   2475篇
  2009年   2270篇
  2008年   4030篇
  2007年   4343篇
  2006年   4502篇
  2005年   4587篇
  2004年   4575篇
  2003年   4388篇
  2002年   4337篇
  2001年   7505篇
  2000年   7471篇
  1999年   6238篇
  1998年   1728篇
  1997年   1650篇
  1996年   1440篇
  1995年   1257篇
  1994年   1135篇
  1993年   1156篇
  1992年   3804篇
  1991年   3615篇
  1990年   3589篇
  1989年   3392篇
  1988年   3007篇
  1987年   2912篇
  1986年   2825篇
  1985年   2636篇
  1984年   1959篇
  1983年   1607篇
  1982年   935篇
  1981年   927篇
  1979年   1833篇
  1978年   1359篇
  1977年   1120篇
  1976年   944篇
  1975年   1186篇
  1974年   1227篇
  1973年   1211篇
  1972年   1054篇
  1971年   980篇
  1970年   881篇
  1969年   793篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
 Because the immunomodulatory effects of antibiotics could possibly influence the degree of the systemic and local response to infection, knowledge of their intrinsic influence on the host's inflammatory response appears to be essential. Therefore, this study investigated the effects of frequently used antimicrobial agents (β-lactams, quinolones gentamicin, vancomycin and metronidazole) on the in-vitro tumor necrosis factor (TNF)-α and interleukin (IL)-6 production of isolated human peripheral blood mononuclear cells (PBMNC), cultured with or without endotoxin, in comparison with those effects obtained in a whole-blood assay system. In the presence of ciprofloxacin, ofloxacin, gentamicin, vancomycin, and metronidazole, a significant inhibition of the endotoxin-stimulated TNF-α production of human peripheral blood mononuclear cells (PBMNC) was found at therapeutic levels. Only ofloxacin showed a significant inhibitory influence on the endotoxin-induced IL-6 production of PBMNC. In the whole-blood assay, significant effects were not detectable. None of the antibiotics showed cytotoxicity. It is concluded that, at present, the direct immunological effects of antibiotics should be interpreted carefully with regard to the experimental conditions, and regardless of the therapeutic implications. To assess the potential direct immunomodulatory effect of antimicrobial agents, different cell culture procedures should be used. Received: October 19, 2001 / Accepted: February 15, 2002  相似文献   
103.
Static analysis with finite element of a realistic femur nail bone-implant system in a typical proximal femoral fracture under physiological load bearing situations provides results for stress, displacement and strain. The question to be answered is, if simulation with the finite element analysis is able to explain biomechanically clinical observed patterns of failure. Surface-Reconstruction with CT database of a proximal femur and reconstruction with CT based density data was done. Next steps were to unite the bone structure with the Proximal Femoral Nail and to model two relevant fractures (31-A2.2 and A2.3 according AO). After modelling of geometry, isotropic material behaviour and load application numeric calculation of the femur-nail system with FE-software was performed. FE simulation mainly shows an axial dislocation of the femoral head screw with nearly no dislocation of the antirotation screw. This so-called z-effect therefore means: (1) Tilting of the proximal main fragment around the sagittal axis between the screws and (2) relative movement of both screws in the frontal plane. Relative movement of the two screws against each other could be the reason for implant failure, the so called cut out. Furthermore simulation shows different gliding of the screws explaining the so called z-telescoping. The analyzed stress patterns have to be relativized, because isotropic material behaviour of cancellous bone was assumed. Further examinations for this issue are necessary.  相似文献   
104.
Occupational diseases Nos. 2108 and 2110 correspond to intervertebral disc-related diseases of the lumbar spine from many years of carrying or lifting heavy loads, occupations in extreme postures of full flexion or oscillation of the whole body when seated, and which compel the cessation of all activities which are or could be the cause for the origin, exacerbation or recurrence of the disease. These occupational diseases came into force at the start of 1993, but there have been considerable problems in their implementation. The present Part I of the contribution is the result of the work of an interdisciplinary study group and contains medical criteria for the assessment of possibly strain-related clinical characteristics and the evaluation of other possible causes. Part II is to be published in Volume 4/2005 and will deal with questions related to forced cessation and to the assessment of the loss of earning ability. Agreement was reached in many areas related to the assessment of occupational claims. This should allow for evidence-based decision making in the future for the occupational diseases Nos. 2108 and 2110.  相似文献   
105.
106.
107.
108.
The information contained in package inserts varies from country to country in Europe, although other regulatory aspects of data presentation are quite similar. West Germany's Drug Law of 1976 requires 11 items to be included in the package insert for both patient and health professional: name/address of manufacturer; drug name; active constituents; indications; contraindications; side effects; drug interactions; dosage instructions; method and duration of application; statement that drug should not be used after expiration date; and statement that drug should be kept out of reach of children. All information must be submitted to the Health Office at the time of application or the applicant is liable for criminal prosecution. Documentation of side effects must be complete, although no special form is required. Similarly, causality assessment needs to be made even though specific algorithms are not required. Proposed amendments to the Drug Law will include additional information to physicians concerning the overdose instructions, pharmacological properties, and bioavailability of the drug. Registration procedures are the same throughout Europe and are called Summary of Products Characteristics. Assessment reports are also required for each new chemical entity in the European Community.  相似文献   
109.
BACKGROUND: Studies of the association between indoor allergen exposure and the development of allergic diseases have often measured allergen exposure at one point in time. OBJECTIVE: We investigated the variability of house dust mite (Der p 1, Der f 1) and cat (Fel d 1) allergen in Dutch homes over a period of 8 years. METHODS: Data were obtained in the Dutch PIAMA birth cohort study. Dust from the child's mattress, the parents' mattress and the living room floor was collected at four points in time, when the child was 3 months, 4, 6 and 8 years old. Dust samples were analysed for Der p 1, Der f 1 and Fel d 1 by sandwich enzyme immuno assay. RESULTS: Mite allergen concentrations for the child's mattress, the parents' mattress and the living room floor were moderately correlated between time-points. Agreement was better for cat allergen. For Der p 1 and Der f 1 on the child's mattress, the within-home variance was close to or smaller than the between-home variance in most cases. For Fel d 1, the within-home variance was almost always smaller than the between-home variance. Results were similar for allergen levels expressed per gram of dust and allergen levels expressed per square metre of the sampled surface. Variance ratios were smaller when samples were taken at shorter time intervals than at longer time intervals. CONCLUSION: Over a period of 4 years, mite and cat allergens measured in house dust are sufficiently stable to use single measurements with confidence in epidemiological studies. The within-home variance was larger when samples were taken 8 years apart so that over such long periods, repetition of sampling is recommended.  相似文献   
110.
Zusammenfassung Die Arbeit stellt den Begriff der Mechanonarkose auf und setzt Chemonarkose und Mechanonarkose in Parallele zueinander. Sowohl chemische Narkotica wie physikalische Kompression machen reversible Lähmungen und irreversible Schädigungen der verschiedensten tierischen und pflanzlichen Lebenserscheinungen, wobei die Lebewesen oder die Organe eines Lebewesens sich nach ihrer Empfindlichkeit und Resistenz in die gleiche Reihenfolge für beide Agentien anordnen. Beide machen in unternarkotischer Dosis allerlei Reizerscheinungen, in übernarkotischer Dosis an Muskeln Kontraktur und Verkürzung, und sind in ihrer Wirkung bis ins Einzelne vergleichbar. Als gemeinsame Erklärungsmöglichkeit für beide Agentien wird die Viscositätserhöhung an Zellgrenzen und Zelloberflächen mit ihrer Erschwerung von Diffusion und Stoffaustausch (Oberflächenverdichtung, Permeabilitätsabnahme) und ihren weiteren Folgen für den Zellstoffwechsel betrachtet.  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