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   9596篇
  免费   33篇
  国内免费   2篇
电工技术   27篇
综合类   5篇
化学工业   144篇
金属工艺   14篇
机械仪表   19篇
建筑科学   66篇
能源动力   32篇
轻工业   129篇
水利工程   6篇
石油天然气   16篇
武器工业   1篇
无线电   122篇
一般工业技术   138篇
冶金工业   8753篇
原子能技术   10篇
自动化技术   149篇
  2022年   10篇
  2021年   9篇
  2020年   7篇
  2019年   13篇
  2018年   17篇
  2017年   16篇
  2016年   22篇
  2015年   12篇
  2014年   25篇
  2013年   21篇
  2012年   33篇
  2011年   40篇
  2010年   45篇
  2009年   42篇
  2008年   54篇
  2007年   45篇
  2006年   47篇
  2005年   39篇
  2004年   47篇
  2003年   43篇
  2002年   23篇
  2001年   29篇
  2000年   40篇
  1999年   308篇
  1998年   2807篇
  1997年   1559篇
  1996年   995篇
  1995年   580篇
  1994年   453篇
  1993年   559篇
  1992年   77篇
  1991年   115篇
  1990年   116篇
  1989年   96篇
  1988年   110篇
  1987年   97篇
  1986年   100篇
  1985年   74篇
  1984年   13篇
  1983年   11篇
  1982年   39篇
  1981年   43篇
  1980年   82篇
  1978年   15篇
  1977年   192篇
  1976年   446篇
  1975年   11篇
  1968年   6篇
  1967年   5篇
  1955年   7篇
排序方式: 共有9631条查询结果,搜索用时 15 毫秒
91.
92.
93.
JM Cummings  RO Parra  JA Boullier 《Canadian Metallurgical Quarterly》1995,45(3):414-8; discussion 418-20
OBJECTIVES: An evolving technology for the treatment of bladder outlet obstruction due to benign prostatic hyperplasia (BPH) is the use of the side-firing neodymium: yttrium-aluminum-garnet (Nd:YAG) laser to achieve prostatic tissue ablation. The purpose of this study was to determine the short-term efficacy of this procedure in both an objective and subjective manner. METHODS: We examined this technique by carefully evaluating our first 25 men undergoing the procedure. Each patient was subjected to careful symptom score analysis using the American Urological Association symptom index and multichannel urodynamics, including pressure-flow studies both preoperatively and at 3 months postoperatively. RESULTS: At the 3-month follow-up, symptom scores improved from a preoperative mean of 11.4 to 7.2 and the mean maximum flow rate improved from 6.1 to 14.5 cc/s. These are both significant at P < 0.001. Statistically similar improvement was seen in detrusor pressure at opening and at maximum flow. Eighty percent of the men studied had at least a 50% reduction in symptom score and a 50% improvement in flow rate. CONCLUSIONS: We conclude that laser prostatectomy is a promising minimally invasive treatment for bladder outlet obstruction secondary to BPH and deserves further evaluation at longer terms of follow-up.  相似文献   
94.
95.
96.
Human anti-murine antibody titres following patient exposure to the monoclonal antibody Orthoclone OKT3 (muromonab-CD3) are determined by laboratories using diverse analytical methods which are not standardized and whose concordance is not established. A multicentre study group therefore compared testing for IgG anti-OKT3 antibody among seven laboratories. A set of 270 sera was obtained from 30 heart, 30 kidney and 30 liver transplant recipients with no previous exposure to OKT3 who were receiving OKT3 for induction immunosuppression. Sera were collected from each patient prior to and at 24 +/- 2 days and 31 +/- 2 days following initial OKT3 exposure. Identical aliquots of all 270 sera were tested for IgG anti-OKT3 antibody by each laboratory. In addition, the limit of detection of each laboratory's method was estimated by titration of an affinity-purified IgG anti-OKT3 reference material of known concentration. Anti-OKT3 antibody formation differed greatly among the three organ groups. Cardiac patients demonstrated the least sensitization and almost exclusively lower titres, while kidney recipients had more frequent and higher titre antibody formation. Liver recipients yielded the highest sensitization rate and the most frequent high titre sera. Importantly, the seven laboratories differed widely in the number of pretreatment sera reported as positive (ranging from 0% to 41% among laboratories), the number of post-OKT3 sera reported as positive (17-63%), the number of post-OKT3 samples with titre > or = 1000 (2-31%), and the number of patients sensitized 19-69%). Concordance among laboratories was highly variable, with interlaboratory agreement ranging from 38% to 83% on the sample titres assigned to 180 post-OKT3 sera. Many of the discordant results were consistent with differences in the limit of detection of the analytical methods, which ranged from 0.19 microgram/ml to > or = 15 micrograms/ml, a nearly 100-fold difference among laboratories. This study demonstrated the presence of both good concordance and significant discordance among laboratories in determining human anti-mouse antibody titres, and demonstrated that common titre categories (100, 1000, 10,000) were not equivalent among laboratories. The level of concordance among methods should be considered when comparing anti-OKT3 antibody results from different centres and their correlation with clinical events. Universal comparative testing, patterned after proficiency testing programmes, is needed to assess differences among laboratories and to bring uniformity and a sound interpretative basis to this field of testing.  相似文献   
97.
In the Netherlands both nursing homes and homes for the aged serve as a residence for demented elderly. Although these institutions differ considerably regarding financing and care facilities, specific functions of each institute concerning demented elderly have not been clearly defined. In order to know to what extent residential facilities serve demented elderly, the prevalence and severity of dementia among residents aged 65 and over was studied as part of a prevalence study among elderly people in a rural area of the Netherlands. The target population existed of all persons aged 65 and over who were registered in eight general practices. Patients who had to leave the practice on account of ill-health and were admitted to nursing homes were included in the study. In a two stage study the MMSE was applied as a screening instrument. Based on MMSE-score a non-proportional stratified random sample was drawn for the second, diagnostic stage, which existed of the CAMDEX. Prevalence estimates for DSM-III-R-dementia were 21% among residents of homes for the aged, 48% among residents of somatic wards of nursing homes and 100% among those admitted to psychogeriatric wards of nursing homes. Severity of dementia was highest among residents of psychogeriatric wards of nursing homes and lowest among those living in homes for the aged. Prevalence of dementia among residents of homes for the aged can be fully attributed to the age-distribution. The high frequency of dementia among residents of somatic nursing home wards can be explained in several ways: First, admission can be necessary due to a combination of dementia and somatic illness.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
98.
99.
Whether a sulfonylurea may be used together with insulin for treating NIDDM has been controversial. One view, based on older studies, has been that the additional benefit is too small or the level of glucose control achieved usually too poor to recommend this method. More recent studies of a more specific way of combining a sulfonylurea with insulin are more supportive. When a single injection of insulin taken in the evening is added to a sulfonylurea at the time of secondary failure of the sulfonylurea alone, glycemic control is quite simply and consistently restored to acceptable levels. At this time in the natural history of NIDDM, evening insulin combined therapy is more effective than a single injection of insulin alone, and just as effective as a more complex multiple-injection regimen without an oral agent. A recent multicenter trial of a new sulfonylurea, glimepiride, in combination with a single injection of 70/30 insulin before dinner has confirmed that this approach is safe and more consistently effective than insulin alone for obese patients beginning insulin in a setting resembling clinical practice. The available evidence suggests this form of combined therapy is suitable for routine use.  相似文献   
100.
This article analyzes data from a national sample of 356 agencies on barriers to providing case management to rural older persons. Although considerable variation is found regarding the degree of difficulty attributed to various barriers, several areas are reported by respondents as problematic, such as a lack of resources to pay for case management and services, a lack of services, and a lack of transportation. On the other hand, a lack of rural case management standards, qualified persons to conduct case management, and opportunities for staff training, as well as staff turnover and professional isolation, are generally not seen as particularly troublesome. More support from families and personal knowledge of clients and service providers are most likely to be seen as advantages in providing case management to rural elders. These findings both support and contradict the current gerontological literature on the types of barriers that impede the development and provision of services to rural older persons. Additional research is needed on the barriers to providing case management to rural older persons before policies directing scarce resources are put into place.  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