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   9384篇
  免费   959篇
  国内免费   73篇
耳鼻咽喉   70篇
儿科学   199篇
妇产科学   300篇
基础医学   1382篇
口腔科学   240篇
临床医学   903篇
内科学   1564篇
皮肤病学   204篇
神经病学   667篇
特种医学   660篇
外科学   1509篇
综合类   272篇
一般理论   7篇
预防医学   987篇
眼科学   208篇
药学   606篇
中国医学   2篇
肿瘤学   636篇
  2021年   128篇
  2020年   77篇
  2019年   163篇
  2018年   159篇
  2017年   117篇
  2016年   124篇
  2015年   141篇
  2014年   186篇
  2013年   281篇
  2012年   385篇
  2011年   406篇
  2010年   247篇
  2009年   282篇
  2008年   424篇
  2007年   446篇
  2006年   438篇
  2005年   407篇
  2004年   357篇
  2003年   334篇
  2002年   318篇
  2001年   297篇
  2000年   302篇
  1999年   256篇
  1998年   135篇
  1997年   143篇
  1996年   143篇
  1995年   146篇
  1994年   119篇
  1993年   110篇
  1992年   230篇
  1991年   206篇
  1990年   196篇
  1989年   223篇
  1988年   171篇
  1987年   199篇
  1986年   174篇
  1985年   190篇
  1984年   144篇
  1983年   120篇
  1982年   105篇
  1981年   63篇
  1980年   76篇
  1979年   116篇
  1978年   74篇
  1977年   80篇
  1976年   67篇
  1975年   64篇
  1974年   74篇
  1973年   71篇
  1968年   63篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Aboriginal suicide has become an issue receiving national attention because of the association with "deaths in custody". To date little systematic work has been directed to the investigation of suicide among a non-incarcerated Aboriginal population. This paper focuses on deaths by suicide within one geographical area. It identifies two factors, alcoholism and disruption of interpersonal attachments, which may play a causal role in male Aboriginal suicide. The sudden emergence of suicide in this partial descent population, in concert with suicides among incarcerated and non-incarcerated Aborigines elsewhere, suggests that socio-historical forces must be examined to further clarify the phenomenon.  相似文献   
72.
Impact of clinical history on fracture detection with radiography   总被引:3,自引:0,他引:3  
The effect of knowledge of localizing symptoms and signs in the detection of fractures was studied. Forty radiographs of the extremities were examined twice by seven radiologists; the sessions were separated by 4 months. In 26 cases, a subtle fracture was present; 14 cases were normal. In half of the cases at each session, the precise location of pain, tenderness, or swelling was provided. The observer was asked to determine if the case was normal or abnormal (provide the exact location of the fracture) and to indicate the degree of confidence in the diagnosis. Responses were converted to a numeric scale for analysis. Analysis of receiver operator characteristic parameters indicates that clues regarding location of trauma facilitate detection of fractures. The improvement is based largely on an increased true-positive rate without an increased false-positive rate, regardless of the decision criteria of the radiologist (overall willingness to "overread" or "underread"). This has direct clinical applicability and reinforces the plea of radiologists for precise clinical information.  相似文献   
73.
The use of food frequency questionnaires for measuring dietary intake has become widespread in epidemiologic studies. It has been suggested that inquiring about a person's usual serving size of each food, in addition to the frequency of consumption, will improve the accuracy of this method. This approach implies that individuals characteristically eat a specific amount of any particular food, and that this amount can be reported with reasonable accuracy. To investigate the variability of portion sizes, the authors analyzed data for 68 commonly consumed foods, based on four one-week weighed diet histories recorded by 194 Boston-area women aged 34-59 years during 1980 and 1981. For each food, total population variance in portion size was partitioned into within-person (intraindividual) and between-person (interindividual) components. For all but seven food items (yogurt, liver, mixed vegetables, watermelon, pancakes/waffles, cold cereal, and cooked cereal) the within-person variance in portion size exceeded the between-person variance. The mean of the within-person to between-person variance ratios, after exclusion of two outlying foods, was 3.4 for untransformed portion sizes, and 3.2 after portion sizes were loge-transformed. Foods with a high within-person variance also tended to have a high between-person variance. The dominance of within-person variance in portion sizes suggests that the concept of usual portion size is complex, and that subjects may experience substantial difficulty in specifying their "usual" portion size. The smaller contribution of between-person variance to the total variance in portion size suggests that specification of a standard portion size by the investigator may not introduce a large error in the estimation of food and nutrient intake.  相似文献   
74.
Clinical applications of electrical stimulation for effecting change in the damaged or disabled nervous system are in their infancy. This technique is extremely powerful, because any neural structure that is electrically excitable can potentially be affected. Although early attempts to apply electrical stimulation were limited by insufficient physiological knowledge and undeveloped technology, developments over the past two decades now provide a strong base for clinical applications. Clinical systems for bladder control and respiration have been in use for many years. Some applications of FES to restore hand function and walking are in multicenter testing, whereas many others are being studied for clinical feasibility at single sites. Applications are focusing on safety and efficacy, as well as on clinical outcome measures to address the issues posed by the regulatory and reimbursement processes. As clinical systems become more routine, issues of multiple system applications will need to be addressed. Present and future applications of functional electrical stimulation may be expected to significantly enhance independence and improve the quality of life for individuals with central nervous system dysfunction.  相似文献   
75.
The clinical course and outcome of 111 patients with tricuspid atresia, seen during 1972-1982, were reviewed. All clinical and investigation data, progress and management were analysed. The mean age at presentation was 21.9 +/- 8.8 days. Patients with reduced pulmonary blood flow presented earlier. Patients with normal or increased pulmonary blood flow usually presented in heart failure. "True" natural history was observed in 13 unoperated patients. Six of these died at the age of 7 days to 8 months (mean 32.2 days). Seven patients survived without surgery for 11 months to 24 years, the older ones developing pulmonary vascular obstructive disease. The overall mortality in the whole series was 32.4% (36/111), the mean age at death was 3.1 years (range 3 days-48 years). The mortality rate within the first year of life was 22.5%. The mean age of survivors at follow-up was 10.7 +/- 0.9 years (range 11 months-27 years).  相似文献   
76.
This study investigated the effect of dehydration on measurements of body composition by hydrostatic weighing (HW) and bioelectric impedance analysis (BIA). Ten endurance-trained male athletes between the ages of 18 and 42 years performed an endurance training session consisting of running until body weight was reduced by approximately 3%. Body composition was determined prior to exercise and immediately after exercise by HW and BIA techniques. A high correlation existed between pre- and postdehydration for both HW and BIA. Validity coefficients between HW and BIA were moderate (predehydration 0.85 and postdehydration 0.82). In addition, BIA percent fat was 3.5% higher than HW percent fat. The BIA revealed a mean loss of 2.1% fat BIA and only 0.9% fat HW after approximately 45 minutes of exercise. BIA also showed an increase in percent body water (mean = 2.6%) in all 10 subjects after dehydration. There are indications that BIA, with its present equational configuration, is measuring something other than lean body weight. J Orthop Sports Phys Ther 1989;10(11):451-455.  相似文献   
77.
Optic nerve pseudomeningioma secondary to localized amyloidosis   总被引:1,自引:0,他引:1  
A 55-year-old woman presented with a mass of the optic nerve sheath suggestive of a meningioma. On excision, this proved to be amyloid. No systemic involvement could be found. Although amyloid may arise as a solitary lesion of the orbit or extraocular muscle, this "pseudomeningiomatous" pattern has not been previously noted. A magnetic resonance scan was helpful because the amyloid imaged at a density similar to vitreous and cerebral white matter, unlike meningiomas, which appear more like bone. The diagnosis of localized amyloidosis, however, still remains dependent on histopathology and cannot be made on a clinical basis.  相似文献   
78.
王文杰  朱秀媛 《药学学报》1989,24(2):151-154
Lei Wan, Poliporus mylittae Cook et Mass(Omphalia lapidescena Scbraet) is a kind of fungus used in traditional Chinese medicine, as an antheiminthie From Lei Wan, an "active component designated as. S-4001 had been isolated.Preliminary results indicate that S-4001 belongs to D, β, 1-3 glucan with some 1-6 linkages.After administration of S-4001, significant antiinflammatory activity was found in various experimental animal models, including croton oil induced ear edema in mice and agar or yeast induced ankle swelling in rats. An inhibitory action on leucocyte migration inducced by intraperitoneal injection of CMC in rats was also observed. The plasma content of corticosterone was significantly increased, but the content of ascorbic acid in the adrenals did not change in rats given S-4001. Apart from these actions, S-4001 showed a number of immunostimulating actions such as increasing the clearance of Congo red from mice blood and potentiating the immunohemolysis reaction in 615 mice.  相似文献   
79.
Sperm-agglutinating antibodies were present in three (2-6%) of 117 fertile men and in 19 (33-9%) of 56 men who had been vasectomized. Twenty-four of the 56 vasectomized men had been studied before vasectomy; sperm-agglutinating antibodies were present in one (4-3%) compared with eight (33-3%) after vasectomy. No sperm-immobilizing antibodies were detected before vasectomy but were present in 10 (17-9%) of the 56 men after vasectomy.  相似文献   
80.
H. Zola    H. A. Moore    I. K. Hunter    A. Hohmann    P. J. Mcnamara    J. Bradley    P. Mum    A. Morley    J. V. Melo  D. Catovsky 《Tissue antigens》1985,26(1):60-70
FMC3 and FMC29 are monoclonal antibodies which react with a 30,000 Dalton molecule expressed on the lymphocyte surface membrane. The molecule is a protein which does not appear to be N-glycosylated. The antigen, which is also expressed intracellularly, does not appear to be a marker of differentiation or maturation. Polyclonal cell populations, such as peripheral blood lymphocytes, show a bimodal distribution of surface antigen density, whilst monoclonal cell populations analysed quantitatively showed unimodal antigen density distributions. This suggests the antigen may be a clonal marker.  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