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   1977篇
  免费   2篇
电工技术   1篇
化学工业   6篇
金属工艺   1篇
建筑科学   2篇
能源动力   6篇
轻工业   12篇
水利工程   1篇
无线电   4篇
一般工业技术   4篇
冶金工业   1928篇
原子能技术   11篇
自动化技术   3篇
  2023年   1篇
  2021年   1篇
  2019年   1篇
  2018年   1篇
  2017年   3篇
  2016年   2篇
  2015年   3篇
  2014年   4篇
  2013年   2篇
  2012年   3篇
  2011年   7篇
  2010年   3篇
  2009年   1篇
  2008年   4篇
  2007年   5篇
  2006年   1篇
  2005年   2篇
  2004年   2篇
  2003年   3篇
  2002年   1篇
  1999年   64篇
  1998年   568篇
  1997年   356篇
  1996年   239篇
  1995年   120篇
  1994年   94篇
  1993年   122篇
  1992年   12篇
  1991年   24篇
  1990年   12篇
  1989年   18篇
  1988年   20篇
  1987年   13篇
  1986年   17篇
  1985年   14篇
  1983年   3篇
  1982年   8篇
  1981年   10篇
  1980年   10篇
  1979年   2篇
  1978年   5篇
  1977年   62篇
  1976年   124篇
  1975年   6篇
  1972年   1篇
  1965年   1篇
  1963年   1篇
  1955年   2篇
  1954年   1篇
排序方式: 共有1979条查询结果,搜索用时 0 毫秒
21.
Resection of a large postinfarctional ventricular aneurysm led to termination of intractable angina pectoris in one patient. The patient has been followed for 5 years and remains angina-free, even though aorto-coronary bypass surgery was not performed in this patient. The patient presented no evidence of congestive heart failure, arterial emboli, or cardiac arrhythmia before or after the surgery. Intractable angina alone in the absence of congestive heart failure, systemic embolism, and refractory ventricular tachyarrhythmia may constitute another indication for ventricular aneurysmectomy with or without concomitant aorto-coronary bypass surgery.  相似文献   
22.
A 4-month-old infant with congenital glaucoma had been treated with a topical antibiotic-corticosteroid for three months. This fact complicated initial management, delaying definitive diagnosis and therapy. Topical steroid therapy in infants can produce a condition simulating congenital glaucoma. Since there is little rationale for using topical steroids to treat most infantile external disease processes, they are best avoided. When steroids are used for a prolonged period, some strategy for detecting glaucoma should be adopted.  相似文献   
23.
The third documented case of primary squamous cell carcinoma of the urachus in the English literature is reported. The interesting coincidental occurrence of the dermoid cyst of the right ovary and a complete longitudinal septum of the vagina and uterine cervix is described.  相似文献   
24.
25.
In a cross-sectional survey carried out in Troms? in 1986-7, 19,137 men and women aged 12-56 years from the general population were asked about their use of drugs during the preceding 14 days. Use of analgesics was very common. On average 28% of the women and 13% of the men had used analgesics. Drug use due to menstruation discomfort contributed only partly to the gender difference. Drug use was independent of age from 20 years of age. Factors having an impact on analgesic drug use were analyzed by logistic regression. The most significant predictors of analgesic use were suffering from headache (OR = 14.2(women) OR = 24.4(men)) and infections (OR = 2.0(women) OR = 2.4(men)). Drug users also tended to suffer from symptoms of depression (women) and sleeplessness (men). Lifestyle and sociodemographic factors were also significant predictors, but were of marginal importance (OR < 1.5) compared with occurrence of pain and infections.  相似文献   
26.
27.
28.
In insects gas exchange may be: 1) entirely passive, when metabolic rate is low; 2) enhanced automatically by muscle contractions that produce movements, e.g., wing movements in flight; or 3) produced by ventilatory movements, particularly of the abdomen. In terrestrial insects such as locusts and cockroaches ventilatory movements are governed by a dominant oscillator in the metathoracic or anterior abdominal ganglion. The dominant oscillator overrides local oscillators in the abdominal ganglia and thus sets the rhythm for the entire abdomen, and it also controls spiracle opening and closing in several thoracic and abdominal segments. This ventilatory control mechanism appears to be different from that generating metachronal rhythms such as occur in the ventilatory and locomotory movements of aquatic arthropods. There are now several examples of rhythms, both ventilatory and locomotory, that can be generated by the central nervous system in the absence of phasic sensory feedback, but the mechanism of rhythm production is not known. Studies of ganglionic output suggest that neuronal oscillators can produce a range of frequencies and that some oscillators may be employed in more than one function or behavior. The mechanisms by which central oscillators are coupled to the output motorneurons are also not known; large phase changes suggest that in some cases different coupling interneurons are active. Intracellular recordings from identified neurons have begun to clarify the important roles of interneurons in the production of motor patterns.  相似文献   
29.
30.
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