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   1687篇
  免费   2篇
化学工业   27篇
建筑科学   10篇
能源动力   1篇
轻工业   32篇
水利工程   1篇
冶金工业   1611篇
自动化技术   7篇
  2021年   1篇
  2020年   1篇
  2019年   1篇
  2017年   1篇
  2016年   1篇
  2015年   2篇
  2014年   3篇
  2013年   2篇
  2012年   2篇
  2011年   4篇
  2010年   6篇
  2009年   2篇
  2008年   2篇
  2007年   3篇
  2006年   1篇
  2005年   3篇
  2004年   3篇
  2003年   3篇
  2002年   1篇
  2001年   2篇
  1999年   35篇
  1998年   446篇
  1997年   254篇
  1996年   180篇
  1995年   117篇
  1994年   96篇
  1993年   93篇
  1992年   12篇
  1991年   18篇
  1990年   19篇
  1989年   28篇
  1988年   25篇
  1987年   28篇
  1986年   21篇
  1985年   20篇
  1984年   1篇
  1983年   7篇
  1982年   9篇
  1981年   7篇
  1980年   23篇
  1978年   7篇
  1977年   58篇
  1976年   127篇
  1975年   5篇
  1973年   2篇
  1966年   1篇
  1964年   2篇
  1962年   1篇
  1955年   1篇
  1935年   2篇
排序方式: 共有1689条查询结果,搜索用时 11 毫秒
71.
It is argued that M. A. Hagen's (see record 1975-00215-001) review of picture perception contains a number of inaccuracies involving the nature of higher order variables in perception, the demonstration of visual compensation, the manipulation of relative size information, the postulation of an ability to discriminate the correctness of viewing point, and the existence of ambiguity in monocular perception. It is suggested that such errors are the result of a misunderstanding of the formal basis of J. J. Gibson's (1950, 1966) perceptual theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
72.
Helcococcus kunzii, a nonvirulent member of the human skin flora, has recently been implicated in causing infections in immunosuppressed patients. We report a case of breast abscess associated with H. kunzii in an immunocompetant patient and discuss the criteria used in its identification and our observations of susceptibility testing for this species.  相似文献   
73.
The Tuberculosis in Animals Subsection of the International Union Against Tuberculosis and Lung Disease (IUATLD) recently identified a need to standardize the deoxyribonucleic acid (DNA) strain typing of Mycobacterium bovis. The standard method for strain typing of M. tuberculosis isolates cannot be directly extrapolated to M. bovis due to the low copy number of IS6110 identified in the majority of M. bovis strains, particularly from cattle. To improve the resolution of M. bovis strains, alternative methods and additional DNA probes have been investigated. In combination with studies of published literature, laboratories performing M. bovis DNA fingerprinting were surveyed. Results of these surveys allowed us to reach consensus and to make recommendations for DNA typing of M. bovis isolates, which hopefully will lead towards a standardized approach to the DNA fingerprinting of this organism. This approach, in conjunction with conventional epidemiological traceback approaches, should facilitate more accurate and effective investigations into the epidemiology, maintenance and transmission of M. bovis within and between man and domesticated, feral and wild animals, both at a local and a global level.  相似文献   
74.
Eighty freshly extracted teeth were endodontically prepared and filled with gutta-percha and either a zinc oxide-eugenol-based sealer or AH26 to determine what effect these sealers, with widely differing properties, would have on apical microleakage after either immediate or delayed dowel space preparation. The teeth were randomly assigned to 1 of 4 groups, and the post space was made either immediately after filling or after being stored in 100% humidity for 1 wk. They were then immersed in a 2% methylene blue solution under vacuum, washed, and split longitudinally. The extent of dye penetration was read by five independent observers and the results analyzed. The only significant difference was in the delayed preparation group with zinc oxide-eugenol sealer, which showed greater leakage than the other groups.  相似文献   
75.
The frequency of infertility in developed countries is approximately 8-10%. New drugs are available for assisted reproduction techniques. Two recombinant follicle-stimulating hormone (FSH) products, follitropin-beta (Follistim in the United States, Puregon in Europe) and follitropin-alpha (Gonal-F), join compounds derived through transfecting nonhuman cell lines with genetic material capable of replicating identical amino acid sequences to human compounds. The cell line used for recombinant (r)-FSH production is the Chinese hamster ovary (CHO). Previously, the only agents that showed benefit in controlled ovulatory stimulation were derived from the urine of menopausal women. Those compounds contain additional substances, such as urinary proteins and various amounts of luteininzing hormone. The amino acid sequence of r-FSH is identical to that of human FSH, but the two recombinant products exist in many different isoforms and differ from each other and from human FSH due to varied carbohydrate side chains. Due to variation in the carbohydrate side chains, follitropin-beta in solution has a higher pH than urine-derived FSH, which enhances receptor affinity and therefore is a greater inducer of folliculogenesis. Follitropin-beta does not cause endogenous production of anti-CHO or anti-FSH antibodies, and is well tolerated.  相似文献   
76.
Rheumatoid-like synovial lesions have been produced experimentally in 21% of rabbits receiving intravenous injections of bovine serum by various regimens. They were characterized by lining cell hyperplasia, accumulations, often follicular, of lymphocytes and plasma cells just under the lining layer, sometimes with extensive fibroplasia and pannus formation with cartilage erosion.  相似文献   
77.
The development and implementation of systems for the more complex realtime image processing and scene understanding tasks, such as robot vision and remote surveillance, calls for faster computation than that possible using the traditional serial computer. The advent of VLSI has made feasible the consideration of more specialized processing architectures, designed to support these datarates, while keeping systems compact and relatively cheap. Two approaches are discussed: the use of a programmable processor array, and the customizing of image processing algorithms in silicon. This paper examines designs based upon each approach in the light of the techniques and constraints of VLSI. In particular we describe in some detail an example of a VLSI parallel array processor, the Grid (GEC rectangular image and data processor), and a number of special-purpose CMOS/SOS chips based on systolic design techniques.  相似文献   
78.
79.
80.
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