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   539篇
  免费   82篇
  国内免费   3篇
耳鼻咽喉   1篇
儿科学   41篇
妇产科学   11篇
基础医学   57篇
口腔科学   31篇
临床医学   107篇
内科学   154篇
皮肤病学   15篇
神经病学   21篇
特种医学   42篇
外科学   19篇
综合类   15篇
预防医学   47篇
眼科学   10篇
药学   26篇
肿瘤学   27篇
  2024年   2篇
  2023年   11篇
  2022年   1篇
  2021年   7篇
  2020年   6篇
  2019年   4篇
  2018年   18篇
  2017年   12篇
  2016年   11篇
  2015年   13篇
  2014年   19篇
  2013年   36篇
  2012年   6篇
  2011年   13篇
  2010年   25篇
  2009年   38篇
  2008年   17篇
  2007年   10篇
  2006年   10篇
  2005年   15篇
  2004年   14篇
  2003年   6篇
  2002年   12篇
  2001年   7篇
  2000年   8篇
  1999年   20篇
  1998年   22篇
  1997年   33篇
  1996年   37篇
  1995年   27篇
  1994年   21篇
  1993年   18篇
  1992年   5篇
  1991年   6篇
  1990年   7篇
  1989年   17篇
  1988年   10篇
  1987年   4篇
  1986年   13篇
  1985年   11篇
  1984年   7篇
  1983年   6篇
  1982年   10篇
  1981年   6篇
  1980年   10篇
  1978年   4篇
  1977年   3篇
  1976年   4篇
  1901年   1篇
  1900年   1篇
排序方式: 共有624条查询结果,搜索用时 15 毫秒
91.
Bradley  WG  Jr; Schmidt  PG 《Radiology》1985,156(1):99-103
Subarachnoid hemorrhage has a much higher intensity in magnetic resonance (MR) images with the passage of time. Acute subarachnoid hemorrhage is difficult to see; within 1 week its appearance has become intensified on T1-weighted images. Different concentrations of blood and lysed red blood cells in cerebrospinal fluid (CSF) were examined spectroscopically but did not significantly alter T1 and T2 relaxation of CSF acutely. Ultraviolet visible spectroscopy of bloody CSF stored hypoxically for 3 days showed the presence of methemoglobin. The iron in methemoglobin is paramagnetic; in combination with water this facilitates T1 relaxation. It is concluded that methemoglobin formation with T1 shortening at least partially accounts for the increasing intensity of the MR appearance of subarachnoid hemorrhage over time in the central nervous system and may also explain the intense appearance of subacute hemorrhage in MR images elsewhere in the body.  相似文献   
92.
朝藿素D的分离和结构   总被引:6,自引:0,他引:6  
从朝鲜淫羊藿(Epimedium koreanum)地上部分分离得到一新黄酮成分(I)和一已知化合物(II)。经光谱解析,证明I的结构为5,7,3',4'-tetrahydroxy-5'-prenylflavone,命名为朝藿素D(epimedokoreanin D);II为2-hydroxy-3,4,6,7-tetramethoxy-9,10-dihydrophenanthren。  相似文献   
93.
The head nurse occupies an important position in the nursing unit Concerning leadership style, a distinction is traditionally made between consideration and initiating structure Sometimes a third style is distinguished as well, namely 'production-orientated' leadership In a study of 561 nurses from 16 general hospitals in The Netherlands, the influence of two leadership styles upon the reactions of nurses (job satisfaction, experienced meaningfulness, health complaints and absenteeism) to their work situations was examined, namely the styles of social (i e consideration) and instrumental leadership (a combination of the styles initiating structure and production-onentated) The separate effects of the two styles were studied, as well as the connection between combinations of leadership styles and reactions The results indicate that social leadership contributes positively to nurses' reactions to their job Instrumental leadership, on the other hand, leads to health complaints From the analyses of combinations of leadership styles it appears that nurses are most satisfied if the head nurse pays much attention to both dimensions of leadership For health complaints, a tendency in this directions is also found Finally, it becomes clear that nurses with a great need for autonomy prefer a different type of leadership from nurses with little need for autonomy  相似文献   
94.
95.
Platelet adhesion to fibrillar collagens (types I, II, III, and V) and nonfibrillar collagens (types IV, VI, VII, and VIII) was investigated in the presence of physiologic concentrations of divalent cations under conditions of stasis and flow. Under static conditions, platelet adhesion was observed to collagen types I through VII but not to type VIII. Under flow conditions, platelet adhesion to collagen types I, II, III, and IV was almost independent of shear rates above 300/s. Collagen type V was nonadhesive. Platelet adhesion to collagen type VI was shear rate-dependent and optimal at a rate of 300/s. Collagen types VII and VIII showed minor reactivity and supported platelet adhesion only between shear rates 100 to 1,000/s. Monoclonal antibody (MoAb) 176D7, directed against platelet membrane glycoprotein Ia (GPIa; very late antigen [VLA]-alpha 2 subunit), completely inhibited platelet adhesion to all collagens tested, under conditions of both stasis and flow. Platelet adhesion to collagen type III at shear rate 1,600/s was only inhibited for 85%. The concentration of antibody required for complete inhibition of platelet adhesion was dependent on the shear rate and the reactivity of the collagen. An MoAb directed against GPIIa (VLA-beta subunit) partially inhibited platelet adhesion to collagen. These results show that GPIa-IIa is a major and universal platelet receptor for eight unique types of collagen.  相似文献   
96.
Ultrasonically guided punctures. A modified technique   总被引:2,自引:0,他引:2  
Lindgren  PG 《Radiology》1980,137(1):235
  相似文献   
97.
This paper describes a qualitative research study which explored the practices and views of nurses working on a new Mental Health Intensive Care Unit A review of the literature identified the main aspects of intensive care provision (1) physical security, (2) characteristics of the patient group, (3) staff-patient ratios, (4) therapeutic environment and (5) multi-agency involvement Twenty-one periods of participant observation helped form the questions for a semi structured in-depth tape recorded interview in which 11 out of a total of 16 trained nurses took part The information is categorized and the discussion is informed by observation of practice The nurses perceived the following as the main issues that the physical environment is inadequate for security, that the patient group appears to have the common characteristic of being unwanted in other clinical settings, that the staff-patient ratio is inadequate and that their vision of the nature of a therapeutic environment is vague  相似文献   
98.
OBJECTIVES: This study estimates the prevalence of perceived food intolerance and its consequences in subjects with irritable bowel syndrome (IBS), evaluates the utility of common tests for food intolerance, studies the relation between perceived food intolerance and other disorders, and discusses the etiology. DESIGN: Cross-sectional study. SETTING: National health survey. SUBJECTS: A selection of the population (n=11,078) in Oppland county, Norway, was invited to a health screening, and a sample of subjects with IBS were included in the study. INTERVENTIONS: A medical history of food intolerance, musculoskeletal pain, mood disorders and abdominal complaints was taken, and tests were performed for food allergy and malabsorption. A dietician evaluated the dietary habits of the subjects. RESULTS: Out of 4,622 subjects with adequately filled-in questionnaires, 84 were included in the study, 59 (70%) had symptoms related to intake of food, 62% limited or excluded food items from the diet and 12% had an inadequate diet. The mean numbers of food items related to symptoms and the number of foods limited or excluded from the diet were 4.8 and 2.5, respectively. There were no associations between the tests for food allergy and malabsorption and perceived food intolerance. Perceived food intolerance was unrelated to musculoskeletal pain and mood disorders. CONCLUSIONS: Perceived food intolerance is a common problem with significant nutritional consequences in a population with IBS. The uselessness of current antibody tests and tests for malabsorption and the lack of correlation to psychiatric co-morbidity make the etiology obscure.  相似文献   
99.
中药升麻的化学成分   总被引:14,自引:0,他引:14  
李从军  陈迪华  肖培根 《药学学报》1993,28(10):777-781
从中药兴安升麻[Cimicifuga dahurica(Turcz.)Maxim.]的干燥根茎中分得五个化合物,其中四个为三萜木糖甙:升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅰ),25-O-乙酰升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅱ),12-羟基升麻醇-3-O-β-D-吡喃木糖甙(23R,24S)(Ⅲ),升麻醇-3-O-β-D-吡喃木糖基(3→1)-β-D-吡喃木糖甙(23R,24S)(Ⅳ),另一个为异阿魏酸(Ⅴ)。Ⅲ和Ⅳ为新化合物,通过光谱(IR,MS,1H及13C NMR)解析确定了它们的结构,分别命名为升麻甙A(cimiside A)和升麻甙B(cimiside B)。  相似文献   
100.
Biologists and physical anthropologists attempted to classify human being into races according to phenotypic variations. The latter are based either on one or two phenotypic characters therefore the outcome is unable to givq clear distinction among different races. Cranial index seems to be an important,tool, which may be used to identify the races in different geographical regions. 75 dried skulls collected from different part of Maharashtra were measured to determine the cranial index. Skulls were classified by the method of Montagu (1960)2 Average maximum cranial length and breadth were found to be 17.11 cm and 12.98 cm respectively and maximum & minimum cranial lengths were observed to be 18.50 and 16.60 cm and cranial breadths were noted to be 14.50 and 12.10 cm respectively. Average cranial index (mean ± SD) was 75.49 ± 3.95. In our study most of the skulls were grouped under the Mesocranial (46.66%) and Dolichocranial (42.66%) categorises when based on Montagu and Dolichocranial categorises when 56% based Comas'. As per the conclusion Maharashtrian population belongs to Indo-Dravidian race.  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