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   2266篇
  免费   9篇
电工技术   8篇
化学工业   48篇
金属工艺   6篇
机械仪表   8篇
建筑科学   10篇
矿业工程   1篇
能源动力   10篇
轻工业   26篇
水利工程   5篇
无线电   66篇
一般工业技术   49篇
冶金工业   1997篇
原子能技术   2篇
自动化技术   39篇
  2022年   3篇
  2020年   3篇
  2019年   3篇
  2018年   5篇
  2017年   6篇
  2016年   4篇
  2015年   4篇
  2013年   18篇
  2012年   9篇
  2011年   13篇
  2010年   11篇
  2009年   5篇
  2008年   11篇
  2007年   14篇
  2006年   8篇
  2005年   14篇
  2004年   4篇
  2003年   16篇
  2002年   9篇
  2001年   6篇
  2000年   7篇
  1999年   63篇
  1998年   612篇
  1997年   340篇
  1996年   237篇
  1995年   110篇
  1994年   120篇
  1993年   139篇
  1992年   16篇
  1991年   26篇
  1990年   32篇
  1989年   26篇
  1988年   20篇
  1987年   22篇
  1986年   28篇
  1985年   19篇
  1984年   7篇
  1983年   6篇
  1982年   11篇
  1981年   20篇
  1980年   15篇
  1979年   4篇
  1978年   7篇
  1977年   64篇
  1976年   132篇
  1975年   6篇
  1974年   5篇
  1973年   3篇
  1971年   2篇
  1955年   3篇
排序方式: 共有2275条查询结果,搜索用时 0 毫秒
41.
Meeting a person with AIDS in the classroom was evaluated to determine if it had an impact on students' perceived susceptibility to HIV infection and attitudes toward persons with AIDS. The meeting was incorporated into the Grade 9 AIDS education program of a school district in Nova Scotia. Four schools participated in this study. Two schools were randomly assigned to the treatment group, which met the person with AIDS, and the remaining two schools formed the comparison group. Measures of the two attitudinal variables were collected using a self-report questionnaire that was administered both prior to and two weeks after the educational intervention. Meeting a person with AIDS in the classroom had no measurable impact on students perceived susceptibility to HIV infection nor on their attitudes toward persons with AIDS. Suggestions for using the educational intervention more effectively and for further research are made.  相似文献   
42.
This study aimed to examine the functional coupling between midbrain raphe and the septohippocampal system at the level of neuronal firing. Raphe unit activity and hippocampal EEG were simultaneously recorded in urethane-anaesthetized rats and their relationship was examined in the frequency domain. Subsets of presumably non-serotonergic neurones in both the dorsal and median raphe nuclei fired rhythmically in synchrony with hippocampal theta activity. Theta cells in the median raphe showed higher coherence than those in dorsal raphe and formed a more homogeneous group of cells, according to their firing rates. Since the raphe-septal serotonergic system is known to desynchronize the hippocampal EEG, activation of a subset of nonserotonergic cells during theta in this nucleus indicates a feedback from the limbic circuitry on the ascending raphe control of forebrain activity.  相似文献   
43.
44.
We reviewed 32 children with 41 radiation-therapy associated slipped capital femoral epiphyses (RTASCFE). Ten were from the authors' institutions and 22 from the literature. Gender distribution was equal. The age at diagnosis of the malignancy was 4.3 +/- 3.1 years; the amount of radiation was 4,240 +/- 1,445 rads. Children with RTASCFE presented younger (10.4 +/- 3.2 years) than a routine SCFE. The average symptom duration was 5 +/- 6 months. Children with RTASCFE are usually thin (median weight, 10th percentile) in contrast to children with typical SCFE, who are usually obese (<95th percentile). The majority (82%) of the slips were mild, compared to routine SCFEs (approximately 50%); 28% were bilateral. There was a positive linear relationship between the age at presentation of the SCFE and the age at diagnosis of the malignancy; there was a negative linear relationship between the age at presentation of the SCFE and the amount of radiation therapy.  相似文献   
45.
46.
Diosgenyl alpha-L-rhamnopyranosyl-(1--2)-[beta-glucopyranosyl-(1--3)]- beta-D-glucopyranoside (gracillin), a monodesmosidic saponin isolated from paris, dioscorea, and costacea species with promising cardiovascular and antitumor activities, was synthesized by stepwise glycosylation.  相似文献   
47.
48.
Bowen's disease has a particular predilection for the lower leg, especially in women. A review of the literature for treating Bowen's disease is presented and the problems associated with treating the lower leg emphasized. Evidence for the various treatment modalities used to treat Bowen's disease largely comes from studies that lack good methodology in terms of standardized techniques, patient controls and adequate follow-up. In particular the widely accepted recommendation for excision is not supported by evidence that this treatment is superior to other modalities. The choice of treatment for Bowen's disease should take into account the patient's general condition, the site and size of the lesion.  相似文献   
49.
50.
Before use of cardiovascular surgical techniques and procedures in humans, many experiments, e.g., hypothermic circulatory arrest and cardiopulmonary bypass using the heart-lung machine, have been performed in the dog. As a consequence experimental canine cardiovascular surgery is highly developed. This has not resulted in the routine performance of open heart surgery in veterinary medicine, probably because of the high costs. Cardiovascular surgery in the dog is generally limited to interventions not depending on hypothermic circulatory arrest or cardiopulmonary bypass. The clinical cardiovascular surgery in dogs can be divided into routine and more specialized interventions. The first category includes correction of peritoneopericardial diaphragmatic hernia, pericardial fenestration in dogs with pericardial effusion, treatment of persistent right aortic arch, and patent ductus closure. The specialized interventions include dilation of pulmonic and aortic stenoses and pacemaker implantation. The diagnosis and surgical treatment of such diseases is described. New developments in cardiovascular surgical treatment that can be expected include catheter techniques for occlusion of shunts and dilations using balloons, because the financial costs of these procedures are not prohibitive.  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