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   1862篇
  免费   0篇
电工技术   1篇
综合类   1篇
化学工业   5篇
机械仪表   2篇
建筑科学   1篇
能源动力   1篇
轻工业   10篇
石油天然气   1篇
无线电   2篇
一般工业技术   4篇
冶金工业   1831篇
自动化技术   3篇
  2019年   1篇
  2017年   1篇
  2015年   1篇
  2014年   1篇
  2013年   2篇
  2011年   3篇
  2010年   2篇
  2009年   2篇
  2006年   5篇
  2005年   3篇
  2004年   3篇
  2003年   2篇
  2002年   2篇
  2001年   2篇
  2000年   3篇
  1999年   65篇
  1998年   611篇
  1997年   310篇
  1996年   196篇
  1995年   114篇
  1994年   90篇
  1993年   114篇
  1992年   23篇
  1991年   21篇
  1990年   24篇
  1989年   20篇
  1988年   20篇
  1987年   31篇
  1986年   20篇
  1985年   11篇
  1984年   2篇
  1983年   9篇
  1982年   4篇
  1981年   6篇
  1980年   25篇
  1978年   2篇
  1977年   21篇
  1976年   80篇
  1975年   3篇
  1973年   1篇
  1971年   2篇
  1970年   1篇
  1969年   1篇
  1955年   1篇
  1933年   1篇
排序方式: 共有1862条查询结果,搜索用时 0 毫秒
11.
Melanocytic naevi on the face and neck of 110 Brisbane secondary school students aged 16-17 years were mapped according to specified regions to investigate the dose-response relationship between ultraviolet (UV) radiation and melanocytic naevi. Highest naevus density occurred in regions receiving a mean UV dose of 0.2-0.4 relative to the vertex while densities were low in minimally and maximally exposed regions. This pattern of naevus distribution was unaffected by sex or phenotypic features such as skin colour or degree of freckling. These findings suggest that there is a narrow dose range over which UV radiation can effectively promote the proliferation of melanocytes. A comparison of the regional distribution of naevi on the face and neck with that of solar keratoses appearing over 1 year on the heads of residents of a neighbouring town has shown them to differ significantly. This study may shed some light on the unknown, yet expectedly complex, relation of UV radiation to melanocytic naevi.  相似文献   
12.
These studies were designed to determine the effect of acute alcohol treatment on gestational length and to probe for a mechanism underlying alcohol-induced early onset of parturition (EOP) in mice. Experiment 1: alcohol increases the incidence of EOP. Pregnant C57BL/6J mice were given alcohol (0, 4, 5 or 6 g kg(-1), i.g.) on Gestational Day (GD) 10, 15, 16, 17 or 18. Deliveries were monitored every 6 h from GD 18. Results indicated that 6 g kg(-1) alcohol treatment on GD 17 or 18 increased the incidence of EOP. Experiment 2: prostaglandins (PGs) play roles in parturition. The purpose of Experiment 2 was to determine whether PGs mediate alcohol-induced EOP in mice. The results indicated that pretreatment on GD 17 with aspirin, a prostaglandin synthesis inhibitor, prevented alcohol-induced EOP. These data suggest that alcohol-induced EOP in mice may be mediated by PGs. Experiment 3: PGs are influenced by alcohol and are triggers of labour. Experiment 3 measured uterine PGs associated with the onset of alcohol-induced EOP in mice. Alcohol increased uterine PGE and PGF2alpha, with PGE levels higher than control before labour, and elevated PGF2alpha levels correlating with labour. Changes in gestational length have important implications for pregnancy outcome, as well as for normal fetal growth and development.  相似文献   
13.
The present study examined the effect of received support on adjustment by foreign students, with data from 33 Chinese students who completed questionnaires at three occasions: three months (the first period), nine months (the second period), and one year and nine months (the third period) after they arrived in Japan. The Social Support Scale for Chinese Students in Japan (Jou, 1993a) and items for measurement of adjustment were used in the questionnaires. Analysis of Variance results revealed no differences among the amounts of support received during the three periods, but compared with the first or second, adjustment was better during the third period. Results from path analysis indicated that support in the first period was positively related to adjustment in the first period, the first period adjustment and second period support positively to the second period adjustment, and only the second period adjustment positively to the third period adjustment. Thus, the present study suggests that it is especially necessary to provide more support to foreign students during the critical early period in order to facilitate their adjustment.  相似文献   
14.
The pathology of aerosolized staphylococcal enterotoxin B (SEB) was studied in the nonhuman primate. Six juvenile rhesus monkeys that received multiple lethal inhaled doses of SEB developed diarrhea and vomiting within 24 hr followed by depression, dyspnea, and shock. Three of 6 animals died by 52 hr. The most striking gross lesion in all 6 monkeys was diffuse severe pulmonary edema. Histologically, edema fluid was present within the peribronchiolar, peribronchial, and perivascular interstitium, alveolar septa, and alveoli. The adventitia of pulmonary vessels was infiltrated by lymphocytes, macrophages, and fewer neutrophils. Numerous large lymphocytes with occasional mitotic figures were within pulmonary vessels, often occluding alveolar capillaries. These cells were strongly immunoreactive with monoclonal antibodies against CD3, establishing them as T cells. Ultrastructurally, endothelial cell junctions were intact, and endothelial cells and type I pneumocytes contained numerous pinocytotic vesicles. Alveolar septal interstitial spaces were expanded by edema. The mechanism of these SEB-induced pulmonary lesions was not determined. We hypothesize that cytokine production by activated T cells may have caused vascular permeability changes leading to widespread pulmonary edema and shock.  相似文献   
15.
CL Brumley  JA Kuhn 《Canadian Metallurgical Quarterly》1995,62(3):343-50, 353-5; quiz 356-8, 361-2
Monoclonal antibodies (MoAbs) are biologically engineered proteins designed to bind to antigens emanating from tumor cells. Selected radioactive isotopes are fused with MoAbs to allow radioimmunodetection of external imaging of metastatic deposits in patients with colon cancer. For the past 10 years, radiolabeled MoAbs have improved tumor localization techniques and influenced the clinical management of surgical patients. Intraoperatively, surgeons use appropriately shielded, handheld, gamma detection probes to locate radiolabeled MoAbs and corresponding colon cancers (ie, residual, recurrent tumors). Using gamma detection probes intraoperatively, surgeons can localize nonpalpable occult tumors and disease not suspected from external antibody scans or other traditional diagnostic methods. This success confirms the need for complete tumor resections, thorough scanning of entire tumor beds, and ex vivo scanning of surgical specimens to assess for potential nodal metastases.  相似文献   
16.
In the context of intense interest in evidence-based practice (EBP), the authors sought to establish consensus on discredited psychological treatments and assessments using Delphi methodology. A panel of 101 experts participated in a 2-stage survey, reporting familiarity with 59 treatments and 30 assessment techniques and rating these on a continuum from not at all discredited to certainly discredited. The authors report their composite findings as well as significant differences that occurred as a function of the experts' gender and theoretical orientation. The results should be interpreted carefully and humbly, but they do offer a cogent first step in consensually identifying a continuum of discredited procedures in modern mental health practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
17.
Investigated the relationship of behavior therapists' characteristics, activities, and treatment conditions to their reported practices in therapy using 69 practicing therapists from the Association for Advancement of Behavior Therapy, who completed a questionnaire assessing their personal and professional characteristics and their use of 99 varied therapeutic techniques and skills. 13 scales were constructed via principal component analysis and analyzed for effects due to each of the independent variables. Results suggest that, even for a homogeneous sample of behavior therapists, reported frequency of use of particular therapeutic techniques varies as a function of the setting of therapy and type of clients. Behavior therapists appeared to selectively employ interventions based on, and generally appropriate to, the particular clinical setting and problem encountered. Behavior therapists' personal characteristics as well as their professional activities also appeared to influence professed clinical practices. The importance of an adaptable therapeutic armamentarium and the need for flexible clinical training are discussed. (60 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
18.
CL Nagendra  GKM Thutupalli 《Vacuum》1981,31(3):137-140
New explicit expressions for computation of the single and double layer thicknesses to be used in the design of anti-reflection coatings (ARC) are presented. A theoretical study on the performance of a double layer ARC systems on Ge using ZnSe, BaF2 and BiF3 is presented.  相似文献   
19.
The model presented in this paper accounts for the relationship between Type A behavior and the work environment and identifies: (1) susceptible Type A individuals; (2) potential occupational stressors in the work environment; (3) subsequent resulting control conflict and maladaptive coping behavior; (4) feedback error and time lag resulting in detrimental symptoms; and (5) methods of changing Type A behavior (Fig 1). From this literature review, it becomes clear that there is a need for further prospective research especially in the area aimed at isolating and determining the specific work environment variables which enhance Type A behavior. As yet, no prospective research project is known which has followed a sample of employees from their job application and interview situation through their careers, in order to investigate changes in, and influences on, Type A behavior patterns. Finally, there is an obvious need for the introduction of more Type A behavior modification programs for workers, and perhaps more emphasis should also be directed toward changing the Type A behavior pattern socialization process, which appears to be so prevalent in urban, middle-class home environments.  相似文献   
20.
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