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   2468篇
  免费   3篇
化学工业   31篇
金属工艺   2篇
建筑科学   1篇
能源动力   4篇
轻工业   5篇
水利工程   1篇
无线电   7篇
一般工业技术   22篇
冶金工业   2381篇
原子能技术   1篇
自动化技术   16篇
  2022年   1篇
  2017年   1篇
  2016年   4篇
  2013年   1篇
  2012年   6篇
  2011年   1篇
  2010年   5篇
  2009年   1篇
  2008年   13篇
  2007年   11篇
  2006年   8篇
  2005年   4篇
  2004年   3篇
  2003年   7篇
  2002年   2篇
  1999年   81篇
  1998年   813篇
  1997年   480篇
  1996年   252篇
  1995年   157篇
  1994年   126篇
  1993年   139篇
  1992年   14篇
  1991年   17篇
  1990年   22篇
  1989年   26篇
  1988年   24篇
  1987年   23篇
  1986年   14篇
  1985年   10篇
  1984年   1篇
  1983年   4篇
  1982年   4篇
  1981年   16篇
  1980年   10篇
  1978年   3篇
  1977年   47篇
  1976年   108篇
  1975年   5篇
  1974年   2篇
  1973年   1篇
  1970年   1篇
  1955年   3篇
排序方式: 共有2471条查询结果,搜索用时 15 毫秒
51.
OBJECTIVE: Concurrent use of benzodiazepines and psychotherapy for panic disorder is a prevalent but highly controversial practice. Although there are many rationales for that approach, critics contend that benzodiazepines foster drug abuse and dependence and undermine psychosocial treatments in various ways. The authors examine that controversy in the light of recent empirical findings and offer some tentative conclusions and recommendations. METHOD: Data from studies combining benzodiazepines and the leading psychosocial treatment for panic disorder, exposure-based cognitive behavior therapy, are reviewed, and their application to clinical practice is discussed. RESULTS: The strongest support for combined treatment is for the addition of cognitive behavior therapy to pharmacotherapy for patients with agoraphobia and for those whose benzodiazepine treatment is being discontinued. The greatest problem with combined treatment is relapse after drug discontinuance. CONCLUSIONS: Combined treatment may be advantageous for some patients, but it must be carefully designed to avoid potential problems. Suggestions for that are given.  相似文献   
52.
53.
54.
55.
We have noted a striking similarity between the sequences of proteins in a novel family of lipases we recently reported [Upton, C. and Buckley, J. T. (1995) Trends Biol. Sci. 20, 178-9] and more than 120 sequences from the database of Expressed Sequence Tags (dbEST) which correspond to at least 30 unique genes from arabidopsis, rice and maize. A cDNA (Arab-1) corresponding to one of these sequences was isolated, sequenced and translated. There was significant similarity to sequences in the new lipase family over the entire open reading frame of Arab-1 and when expressed in E. coli, the gene product was lipolytic. Arab-1 and genes for some of the other plant proteins appear to be differentially expressed. They may play a role in the regulation of lipid metabolism during plant development.  相似文献   
56.
We present a computational model of the processes involved in retrieving stored semantic and name information from objects, using a simple interactive activation and competition architecture. We simulate evidence showing a cross-over in normal reaction times to make semantic classification and identification responses to objects from categories with either structurally similar or structurally dissimilar exemplars, and that identification times to objects from these two different classes correlate differentially with measures of the structural similarity of objects within the category and the frequency of the object's name. Structural similarity exerts a negative effect on object decision as well as naming, though this effect is larger on naming. Also, on naming, structural similarity interacts with the effects of name frequency, captured in the model by varying the weight on connections from semantic to name units; frequency effects are larger with structurally dissimilar items. In addition, (1) the range of potential errors for objects from these two classes, when responses are elicited before activation reached a stable state, differ--a wider range of errors occur to objects from categories with structurally similar exemplars; and (2) simulated lesions to different locations within the model produce selective impairments to identification but not to semantic classification responses to objects from categories with structurally similar exemplars. We discuss the results in relation to data on visual object processing in both normality and pathology.  相似文献   
57.
OBJECTIVE: 1) To examine the ordering of head CT scans in elder patients with delirium and cognitive impairment; and 2) to report CT scan findings associated with these conditions. METHODS: This was a 2-part study. Part 1 was a prospective, observational study of 560 adults > 70 years of age evaluated at 3 separate EDs using a 200-hour stratified sampling process at each ED. During Part 1, the frequencies of specific findings (i.e., delirium, impaired consciousness, and impaired cognition) and CT scan rates for these groups were determined. Part 2 was a retrospective analysis of CT scan reports and medical records (n = 279) for patients > 70 years of age in the prospective sample (n = 79) and from a sample (n = 200) of CT scans obtained at a fourth ED. Part 2 examined clinical findings detected in the ED to determine those factors that were associated with acute findings on CT scan. RESULTS: Part 1: There were 333 (59.4%) patients prospectively classified as having impaired cognition, impaired consciousness, or delirium; 79 (23.7%) of these patients had a head CT scan. Of these 3 groups, delirious patients were more frequently scanned (p < 0.001). Part 2: Of 279 CT scans, 42 (15.0%) were positive for an acute condition (hemorrhage, hematoma, space-occupying lesion, infarct). Of 42 positive scans, 40 (95.1%) were found in the 102 (36.6%) patients with either impaired consciousness or a new focal neurologic finding detected in the ED. CONCLUSIONS: Considerable variability in ED CT scan ordering exists for elder patients with neurologic findings. Impaired consciousness and/or new focal neurologic signs are associated with acute findings on CT scan in elder patients. Acute CT abnormalities are uncommon in elder ED patients with other neurologic findings. Additional prospective evaluation is warranted prior to guideline development for CT scans in this patient population.  相似文献   
58.
59.
Orocaecal transit time (OCTT) was assessed in six healthy beagles by means of the breath hydrogen test (BH2T) and the sulphasalazine/sulphapyridine method (SLZ) after the administration of a test meal of canned food mixed with sulphasalazine. Orocaecal transit time was defined as the time taken from the oral administration of the test meal to the time when the first portion of the meal reached the colon. In five of the dogs the OCTTs assessed by the BH2T were shorter than those measured by the SLZ method by 30, 15, 45, 30 and 45 minutes. However, the median OCTT assessed by the BH2T (135 minutes, range 120 to 195 minutes) was not significantly different from that measured by the SLZ (180 minutes, range 150 to 210 minutes) and was highly correlated with it (r = 0.94, P = 0.016). The sixth dog maintained baseline hydrogen and plasma sulphapyridine readings throughout the monitoring period and the OCTT could not be measured.  相似文献   
60.
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