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   842篇
  免费   3篇
  国内免费   1篇
电工技术   1篇
化学工业   49篇
金属工艺   7篇
机械仪表   17篇
建筑科学   11篇
矿业工程   3篇
能源动力   5篇
轻工业   12篇
水利工程   5篇
石油天然气   1篇
无线电   26篇
一般工业技术   51篇
冶金工业   579篇
原子能技术   4篇
自动化技术   75篇
  2021年   2篇
  2017年   3篇
  2016年   6篇
  2015年   2篇
  2014年   4篇
  2013年   14篇
  2012年   16篇
  2011年   12篇
  2010年   9篇
  2009年   12篇
  2008年   11篇
  2007年   6篇
  2006年   11篇
  2005年   9篇
  2004年   5篇
  2003年   4篇
  2002年   10篇
  2001年   4篇
  2000年   11篇
  1999年   22篇
  1998年   167篇
  1997年   100篇
  1996年   72篇
  1995年   37篇
  1994年   32篇
  1993年   41篇
  1992年   12篇
  1991年   7篇
  1990年   8篇
  1989年   11篇
  1988年   12篇
  1987年   11篇
  1986年   7篇
  1985年   6篇
  1984年   9篇
  1983年   9篇
  1982年   9篇
  1981年   9篇
  1980年   18篇
  1979年   6篇
  1978年   4篇
  1977年   23篇
  1976年   42篇
  1975年   4篇
  1974年   2篇
  1973年   3篇
  1969年   3篇
  1958年   1篇
  1930年   1篇
  1928年   1篇
排序方式: 共有846条查询结果,搜索用时 500 毫秒
31.
1. Out of 494 infants none was breastfed within 2 hours of delivery. 36% infants received first breastfeed after 24 hours of delivery 91.2% of the mothers used prelacteal feeds. 2. Only 31.06% of the infants were weaned, out of these only 7 received complementary foods between 4-6 months. 3. Thus, it can be concluded that though breastfeeding is practiced by all mothers, there is need for early initiation of breastfeeding and proper weaning habits.  相似文献   
32.
It is known that the growth factor activates appropriate membrane receptors which become starting points of cascades of protein-protein interactions leading to cellular response. Recent data suggest that different signalling pathways may cross-talk during the cellular response. Here we show that phosphoinositide-specific phospholipase C gamma 1, one of the key elements in phosphoinositide pathway of signal transduction, is physically associated with members of the STAT pathway. The precipitation of phospholipase C gamma 1, using polyclonal antibody in A-431 cells, leads to co-immunoprecipitation of STAT1 alpha and STAT1 beta, as well as STAT3. The formation of such complexes was observed in both unstimulated and EGF stimulated cells. The participation of SH3-domains in the formation of such complexes is discussed.  相似文献   
33.
PURPOSE: To analyze the likelihood of perioperative transfusion using the data of the abstracted patient discharge records. MATERIAL AND METHODS: It was studied the data of the records of the pediatric patients in whom were done surgical procedures for 1996. The abstracted patient discharge records are codified according the ICD-9-CM codes. RESULTS: 1,166 pediatric patients were operated, of whom were transfused 25 (2.1%). The transfusion rate was higher in patients less than 3 years old, who were operated with three o more surgical procedures simultaneously, who were admitted newly after the admittance here studied, and patients operated of spine, dorsolumbar spine, pharynx, thorax and mediastinum, central nervous system, colon, vessels and hip. CONCLUSIONS: Given the variability of the transfusion rate, to know it will allow a better planning of the surgical transfusions, the policy of the hospital blood bank and to increase the information to patient about the risk of the elective surgery.  相似文献   
34.
Vinylidenebisphosphonic acid tetraethyl ester (1) and diazo ketones 7a-1 in ether at 22 degrees C yield pyrazoline bisphosphonate tetraethyl esters 8a-1 in moderate to good yield. These compounds were evaluated in animal models of arthritis: rat adjuvant-induced polyarthritis (AIP) and murine antigen-induced arthritis (AIA) and a murine model of chronic inflammation, the delayed type hypersensitivity granuloma reaction (DTH-GRA). (5-Benzoyl-2,4-dihydro-3H-pyrazol-3-ylidene)-bisphosphonic acid tetraethyl ester (8a), and [5-(3-fluorobenzoyl)-2,4-dihydro-3H-pyraxol-3-ylidene]- bisphosphonic acid tetraethyl ester (8d) significantly inhibited the arthritis models, AIP (15 mg/kg) and AIA (25 mg/kg), as well as the DTH-GRA (25 mg/kg). Conversion of 8a to the corresponding bisphosphonic acid, 10a, resulted in loss of activity. Compounds with alkyl substituents on the pyrazoline nitrogen, 9a-d, were inactive in the DTH-GRA. These results show that 8a and 8d have novel antiinflammatory activity and are capable of inhibiting chronic arthritis and inflammation in animals. Such compounds might be useful in man for treating chronic tissue injury associated with arthropathies such as inflammatory joint disease as well as other chronic inflammatory diseases.  相似文献   
35.
36.
Community hospital graduate medical education programs have been judged deficient in several areas when compared with university programs. Generally community programs are smaller, they have a greater percentage of foreign house officers and unfilled house staff positions, and their graduates do less well on specialty board examinations. Difficulties may exist in offering a balanced and broad-based educational exposure. Four separate pediatric residencies in Phoenix became affiliated in 1972. The traditional deficiencies have been overcome, and a very popular and well-balanced program has ensued. Additionally, wasteful duplication has been avoided. Disadvantages have included complex scheduling and loss of continual close contact with house officers. Assigning patients to residents for continuity of care has been difficult. Experiences gained in this amalgamation may well apply to other hospitals facing similar problems. Local consortiums, such as this, fit well into university affiliated programs or statewide organizations.  相似文献   
37.
Isolated lamb hearts perfused at 13degrees C. with acellular perfusates developed progressive intersitital edema and a rise in vascular resistance. They did not exhbit any electrical or mechanical activity. In contrast, hearts perfused with whole fresh blood remained well preserved, had no edema or change in vascular resistance, and contracted vigorously while being perfused at 10degrees and 13degrees C. This study was designed to determine which particular component(s) of whole blood contributed to improved cardiac preservation. Isolated lamb hearts were perfused for 18 hours at 13degrees C. with plasma containing platelets and some or no red blood cells. Continuously fresh plasma was obtained from a donor animal by means of a flow-through centrifuge. Hearts perfused at 13degrees C. with fresh plasma of either low or high platelet count contracted during the initial 2 to 4 hours of the perfusion only and were as poorly preserved as hearts perfused with acellular microfiltered plasma. A hematocrit value of 2 to 5 per cent in the plasma perfusate resulted in the hearts being preserved almost as well as with fresh whole blood; they showed a forceful cardiac activity at 13degrees C., there was no edema, the vascular resistance was stable, and after rewarming they had good ventricular function. The improvement in cardiac preservation brought about by addition of a minimal amount of red blood cells suggests a specific effect of erythrocytes on the cardiac microcirculation.  相似文献   
38.
39.
This paper examines the factors and theoretical frameworks for the adoption of technology for older adults, and proposes two models of technology acceptance and rejection, one from an ease of learning perspective, and one from a system and user perspective. Both models are supported from reports on two case studies of older adults using handheld touchscreen tablet devices; one in which the participants are supported during tasks primarily related to walking and navigation, and one in which participants are unsupported in communication related tasks. The first study shows the powerful role that facilitating conditions have for learning how to use digital technologies for this user group, whether supporting through step by step guidance, providing a friendly space to use trial and error methods, and/or provision of a manual. The second study shows the pitfalls of a lack of facilitating conditions during initial use, and highlights potential for appropriate design in helping to avoid some user errors during this phase.  相似文献   
40.
A 100 ?m-diameter GaAs triangular barrier switch (TBS) has been optically switched using a GaAlAs laser diode. The resulting transient response has been measured to have a leading edge of ~ 295 ps.  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