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   834篇
  免费   5篇
电工技术   3篇
化学工业   42篇
金属工艺   2篇
机械仪表   6篇
建筑科学   3篇
能源动力   16篇
轻工业   18篇
水利工程   2篇
无线电   29篇
一般工业技术   35篇
冶金工业   618篇
原子能技术   2篇
自动化技术   63篇
  2023年   4篇
  2022年   11篇
  2021年   11篇
  2020年   8篇
  2019年   5篇
  2018年   5篇
  2017年   10篇
  2016年   10篇
  2015年   2篇
  2014年   4篇
  2013年   8篇
  2012年   7篇
  2011年   6篇
  2010年   6篇
  2009年   11篇
  2008年   9篇
  2007年   9篇
  2006年   7篇
  2005年   7篇
  2004年   2篇
  2002年   3篇
  2001年   2篇
  2000年   2篇
  1999年   11篇
  1998年   155篇
  1997年   100篇
  1996年   61篇
  1995年   53篇
  1994年   39篇
  1993年   48篇
  1992年   14篇
  1991年   15篇
  1990年   13篇
  1989年   8篇
  1988年   7篇
  1987年   10篇
  1986年   8篇
  1985年   13篇
  1984年   3篇
  1983年   2篇
  1982年   6篇
  1981年   6篇
  1980年   8篇
  1979年   5篇
  1978年   7篇
  1977年   22篇
  1976年   64篇
  1975年   4篇
  1973年   3篇
  1940年   1篇
排序方式: 共有839条查询结果,搜索用时 15 毫秒
21.
The frequent difficulties encountered in the diagnosis of pediatric sarcomas, caused by the lack of observable differentiation at the light microscopic level, has led to the routine use of immunohistochemistry in pediatric surgical pathology. To a large degree the advent of this staining technique has led to the correct assessment of many perplexing lesions that previously would have been given inconclusive diagnoses. However, with increased usage and testing, it has become apparent that there are few, if any, "magic bullets" in immunohistochemistry for pediatric pathologists. Thus, it behooves diagnosticians to be careful in the usage of this technique, to be aware of possible discrepancies in its results, and to remember the ancillary nature of its application. The following article will review selected markers commonly used in pediatric surgical pathology, from both previous reports and the author's perspective, and will briefly consider several new phenotypic markers which have potential utility with childhood sarcomas.  相似文献   
22.
The authors' experience with 45 papillosphincterotomies, performed for diseases of bile passages and chronic pancreatitis, is reported. The details of the operative technic, employed by the authors, are described. The technic of papillosphincterotomy on a conus-shape sound by means of a "laser scalpel" proved to be the most perfect one. Careful observation of the surgical technic made it possible to gain favourable results--only 1 of 45 operated patients died. Papillosphincterotomy is largely advocated in stenoses and concretions in the large duodenal papilla, strictures of choledocho-duodenoanastomoses, care should be taken not to overwiden indications to the operation concerned.  相似文献   
23.
Flexible robotic cells combine the capabilities of robotic flow shops with those of flexible manufacturing systems. In an m-machine flexible cell, each part visits each machine in the same order. However, the m operations can be performed in any order, and each machine can be configured to perform any operation. We derive the maximum percentage increase in throughput that can be achieved by changing the assignment of operations to machines and then keeping that assignment constant throughout a lot's processing. We find that no increase can be gained in two-machine cells, and that the gain in three- and four-machine cells each is at most 14 %.  相似文献   
24.
The presence of dissimilar network models and standards necessitates interoperability as a means of achieving ubiquitous connectivity and management. The primary focus of this paper is to identify interoperability issues, independent of the network management model, which form the basis for developing interworking paradigms. Network Management and Interoperability related concepts and terminology are introduced and a generic network management framework is presented. Based on the generic framework, interoperability issues for developing paradigms are identified systematically. Different paradigms for interoperability are described and compared. The techniques used by these paradigms in addressing the issues identified are discussed.  相似文献   
25.
This paper proposes a new methodology to solve partially observed inventory problems. Generally, these problems have infinite-dimensional states that are conditional distributions of the inventory level. Our methodology involves linearizing the state transitions via unnormalized probabilities. It then uses an appropriate functional basis to represent the state. Considering the speed and stability of computations, we choose truncated Chebyshev polynomials as the basis. We use Fast Fourier Transforms along with an appropriate discretization of inventory levels to speed up the computations. These main ideas are blended to obtain an iterative algorithm to solve a partially observed inventory model with rain checks. In this model, the inventory manager (IM) does not know the inventory level when it is positive. Otherwise, the IM fully observes it. This model provides a context to illustrate our methodology, which applies to other such models. Although this model has been studied mathematically in the literature, the use of our algorithm provides a numerical approximation of the optimal order quantities. These are compared to the orders released under a base mean-stock policy, where the IM replaces the unobserved inventory level with its mean and applies the well-known base stock policy. We show numerically that the optimal order quantity is very close to the base mean-stock order quantity, when the variance of the inventory distribution is small. When the mean of the inventory distribution is large, the optimal order quantity is more than the base mean-stock quantity, and it is the other way around when the mean is small or negative. These insights are explained via uncertainty and information effects and their interplay. We expect this interplay to show up in other partially observed inventory models.  相似文献   
26.
Salmonellosis on the dairy continues to have a significant effect on animal health and productivity and in the United States. Additionally, Salmonella enterica ssp. enterica causes an estimated 1.2 million cases of human illness annually. Contributing to the morbidity and mortality in both human and domestic animal species is emergence of antimicrobial resistance by Salmonella species and increased incidence of multidrug-resistant isolates. This study describes serotype distribution and the antimicrobial resistance patterns for various Salmonella serotypes isolated from bovine samples submitted to the Wisconsin Veterinary Diagnostic Laboratory (WVDL) over the past 10 yr. Salmonella serotyping and antimicrobial susceptibility testing data were obtained from the laboratory information management system at WVDL. Data from accessions were limited to bovine samples submitted to the WVDL between January 2006 and June 2015 and those that had both a definitive serotype and complete results for antimicrobial susceptibility testing. A total of 4,976 isolates were identified. Salmonella enterica ser. Dublin was the most prevalent serotype identified among bovine samples submitted to the WVDL, accounting for a total of 1,153 isolates (23% of total isolates) over the study period. Along with Dublin, Salmonella enterica ser. Cerro (795, 16%), Newport (720, 14%), Montevideo (421, 8%), Kentucky (419, 8%), and Typhimurium (202, 4%) comprised the top 6 most commonly isolated serotypes during that time. Overall, resistance of bovine Salmonella isolates in the study population remained stable, although decreases in resistance were noted for gentamicin, neomycin, and trimethoprim sulfamethoxazole during the study period. All isolates remained susceptible to enrofloxacin. These data show that antimicrobial susceptibility for bovine Salmonella has changed in the population served by WVDL in the past 10 yr. This information is important for understanding Salmonella disease ecology in Wisconsin. Our findings are also relevant for animal and public health by improving informed antimicrobial use, new drug development, and regulation of their use in food animals.  相似文献   
27.
28.
The degree to which a reformed U.S. health care system relies on an adequate supply of primary care physicians will determine the urgency of change in the composition of the medical workforce. In many areas of the United States, the demand for primary care physicians, particularly in managed care settings, far exceeds the supply. In contrast, reports of reduced practice opportunities for medical and surgical subspecialists in the same settings are increasing. As opportunities for and incomes of primary care physicians are enhanced, some medical subspecialists may seek retraining in primary care. This article provides a context for understanding the development of physician retraining programs, examines precedents for retraining physicians, describes four possible pathways through which medical subspecialists might acquire primary care training, and emphasizes the importance of defining the scope of practice and necessary skills for providing primary care. Obstacles to retraining appear to be economic (Who will pay? Is the cost worth the benefit?) and jurisdictional (Who will define core competencies? Who will credential programs and trainees?). The current absence of demand for such retraining programs suggests either that marketplace-induced changes will not take place or that the notion of a primary care provider shortage and an oversupply of medical subspecialists is overstated. The inclusion of physician retraining programs in proposed health reform legislation suggests that policymakers are convinced that such programs offer one viable solution to the nation's medical workforce needs.  相似文献   
29.
30.
We investigated the effect of the somatosensory functions to the outcomes of motor functions in 28 patients with thalamic hemorrhage. The disturbance of the pyramidal tracts was assessed by the destruction of the internal capsule found in computed tomography (CT). The disturbance of the somatosensory function was analyzed by the N20 component of short-latency somatosensory evoked potentials (SSEP). The outcomes of motor function was evaluated after 3 months of ictus. Correlations between the outcomes of motor function, disturbance of the pyramidal tract, and disturbance of the somatosensory function were discussed. The result indicated that functional outcomes statistically correlated with neither disturbance of the internal capsule alone nor disturbance of N20 alone. But, there was statistically significant between functional outcomes and the combination of disturbance of the internal capsule with disturbance of N20 (p < 0.05, Wilcoxon signed-rank). There was not statistical difference in hematoma volume or consciousness. The implications of these results suggest that somatosensory function may affect the recovery of motor functions.  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