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   2148篇
  免费   3篇
  国内免费   1篇
电工技术   2篇
化学工业   49篇
金属工艺   9篇
机械仪表   6篇
建筑科学   4篇
能源动力   5篇
轻工业   10篇
水利工程   1篇
石油天然气   3篇
无线电   9篇
一般工业技术   36篇
冶金工业   1987篇
原子能技术   1篇
自动化技术   30篇
  2023年   2篇
  2021年   3篇
  2020年   2篇
  2019年   3篇
  2018年   4篇
  2017年   5篇
  2016年   8篇
  2014年   3篇
  2013年   8篇
  2012年   9篇
  2011年   9篇
  2010年   10篇
  2009年   3篇
  2008年   10篇
  2007年   7篇
  2006年   8篇
  2005年   2篇
  2004年   3篇
  2003年   5篇
  2002年   6篇
  2001年   2篇
  1999年   64篇
  1998年   586篇
  1997年   331篇
  1996年   196篇
  1995年   123篇
  1994年   116篇
  1993年   120篇
  1992年   26篇
  1991年   39篇
  1990年   28篇
  1989年   45篇
  1988年   38篇
  1987年   27篇
  1986年   27篇
  1985年   20篇
  1984年   2篇
  1983年   10篇
  1982年   13篇
  1981年   9篇
  1980年   18篇
  1979年   4篇
  1978年   3篇
  1977年   56篇
  1976年   124篇
  1975年   2篇
  1965年   1篇
  1956年   1篇
  1954年   2篇
  1940年   1篇
排序方式: 共有2152条查询结果,搜索用时 15 毫秒
61.
62.
63.
BACKGROUND: The procoagulant effect of anionic phospholipid may play a major role in the development of arterial thrombosis. METHODS AND RESULTS: Annexin V, a calcium-dependent anionic-phospholipid-binding protein, was expressed and isolated from Escherichia coli and its antithrombotic effect examined in a rabbit carotid artery thrombosis model. A partially occlusive thrombus was formed in the left carotid artery by application of electric current to produce an approximately 50% occlusion of the lumen. After the current was discontinued, flow ceased completely within 42+/-12 minutes (n=6) because of continuing platelet/fibrin thrombus formation. When annexin V was given at doses of 2.8 to 16.6 microg x kg(-1) x min(-1) for a period of 180 minutes, starting at the time the current was stopped, there was a dose-dependent inhibition of thrombus formation. At a dose of 5.6 microg x kg(-1) x min(-1), blood flow remained patent throughout the infusion and for an additional 60 minutes after the infusion was stopped. In addition, there was a decrease in thrombus weight (16+/-7.4 versus 2.0+/-1.0 g), (125)I-fibrin deposition (approximately 45% reduction, P<.001), and (111)In-labeled platelet accumulation (approximately 43% reduction, P<.001). Prior mixing of annexin V with phosphatidylserine micelles abolished the antithrombotic effect of annexin V, whereas mixing with phosphatidylcholine micelles had no effect. The antithrombotic effect of annexin V was not associated with bleeding tendency, as judged by the amount of blood absorbed in a gauze pad placed in a surgical incision extending to the muscle tissue and by the standard template bleeding time. CONCLUSIONS: These observations support a potentially important role for anionic phospholipid exposure in platelets in arterial thrombosis, and inhibition of this activity could be a novel target for therapy in coronary thrombosis and stroke and after angioplasty.  相似文献   
64.
Complicated colorectal carcinoma has several symptoms, the most common being bleeding and obstruction. Occasionally it will cause perforation, which carries a worse prognosis. We report a case of perforated adenocarcinoma of the cecum that presented as an abscess of the thigh. We also present a review of the literature on this subject.  相似文献   
65.
66.
Many patients diagnosed with breast cancer will develop metastases and these have diverse presentations. We have reviewed 100 consecutive patients who have died with metastatic breast cancer, to determine the frequency, sites and mode of presentation of recurrent disease. The commonest site of failure was loco-regional (n = 61), this usually presented with a mass, but a minority of patients also complained of pain. Bone metastases developed in 60 patients and produced bone pain, pathological fracture (n = 6) or cord compression (n = 5). Pulmonary metastases producing shortness of breath were diagnosed in 34 patients and were asymptomatic in a further 10. Intra-abdominal metastases were found at some time in 23 patients, most commonly in the liver (n = 20) and the majority complained of epigastric pain (n = 17). Brain metastases occurred in 23 patients and produced a wide range of symptoms including those of a space-occupying lesion (n = 10), cranial nerve palsy (n = 7), diabetes insipidus (n = 3), focal limb weakness (n = 2) and meningitis (n = 1). Three patients had choroid metastases producing reduced visual acuity. Recurrent breast carcinoma can present in a variety of ways, therefore any new symptom or sign should be considered to represent recurrence until proved otherwise.  相似文献   
67.
68.
Conclusion The use of fats, fatty oils, and derivatives is extensive in the petroleum industry to improve its lubricants in their wetting ability or oiliness. Fats and their derivatives serve to carry active elements such as chlorine, sulfur, and phosphorus for the improvement of load-carrying capacity, resistance to oxidation, inhibiting corrosiveness, and preventing wear during use. Greases are compounded from whole fats and fatty acids which serve under suitable conditions to gel lubricating oil and thus fulfill lubricating requirements which the liquid oils cannot themselves satisfy. Greases and their components may be tested for skin hardening in storage by means of an oxygen absorption test which distinguishes between satisfactory and unsatisfactory ingredients and products. Presented in a symposium on the Industrial Applications of Fats & Fatty Acids at the Fall Convention of the American Oil Chemists Society, Chicago, Oct. 1939.  相似文献   
69.
70.
BACKGROUND: This study aims to gain an understanding of treatment delays and their nature in initial psychotic episodes. We investigated to whom people turn for help, how long that approach takes and subsequent delays in commencing treatment. METHOD: Qualitative and quantitative methods were combined with interviews of 62 people suffering from first-episode psychoses, aged 16-30 years, who had recently accessed a specialist mental health service in Melbourne, Australia. A modified version of the World Health Organization Encounter Form was analysed in conjunction with other data. RESULTS: Pathways to care and the ways in which they were experienced were highly variable, with 50% of people experiencing psychotic symptoms before approaching any service. The general practitioner played a key role with 50% of people having had GP contact at some point prior to commencing effective treatment. Where an individual's own efforts to seek early help failed, the role of relatives and others was subsequently vital. CONCLUSIONS: Opportunities exist for shortening delays through targeted health promotion activities and professional training. The need is indicated for a multi-layered or topographical strategy to identify and minimise critical barriers on the route to early intervention. Refinement of interview techniques and instruments of measurement are needed to enhance the explanatory power of data collected.  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