全文获取类型
收费全文 | 2140篇 |
免费 | 1篇 |
专业分类
化学工业 | 11篇 |
机械仪表 | 3篇 |
建筑科学 | 1篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
轻工业 | 11篇 |
无线电 | 1篇 |
一般工业技术 | 5篇 |
冶金工业 | 2102篇 |
自动化技术 | 5篇 |
出版年
2022年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 1篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 57篇 |
1998年 | 581篇 |
1997年 | 366篇 |
1996年 | 242篇 |
1995年 | 137篇 |
1994年 | 101篇 |
1993年 | 137篇 |
1992年 | 20篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 31篇 |
1988年 | 24篇 |
1987年 | 22篇 |
1986年 | 22篇 |
1985年 | 24篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 74篇 |
1976年 | 151篇 |
1975年 | 4篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1955年 | 2篇 |
排序方式: 共有2141条查询结果,搜索用时 41 毫秒
101.
GENOMIC HARDWIRING AND PHENOTYPIC PLASTICITY OF TERPENOID-BASED DEFENSES IN CONIFERS 总被引:8,自引:0,他引:8
Over evolutionary history, conifers have faced a myriad of threats from phloem- and xylem-feeding insects, defoliating insects, and fungal pathogens. Among the trees defenses, terpenoids appear to play a major role by harming, disabling, deterring, repelling, or otherwise reducing the fitness of potential invaders. Each of the three classes of terpenoids in conifers, monoterpenes, sesquiterpenes, and diterpenes, are composed of a large number of representative compounds. In most cases, the presence of a particular terpenoid compound in the oleoresin or volatile emissions from a specific conifer can be accounted for by the expression of one of many committed terpene synthase (TPS) genes. However, while each TPS may produce one or a few major products, many produce a variety of minor products with relatively constant component ratios in the product blends. TPS genes exist in conifers in large and functionally diverse, yet monophyletic, gene families. Within these gene families, new biochemical functions of TPS appear to have evolved by gene duplication and changes in the amino acid sequence of the enzymes active site. In addition, TPS genes may be differentially expressed prior to, during, and following attack by insects or pathogens. Thus, while the production of any particular terpenoid is hardwired into a conifers genome, these trees have the capacity to change the mixture of terpenoids in oleoresin secretions and volatile emissions. Anatomical changes may also accompany induced terpenoid production, supplementing the plasticity of the molecular and biochemical events. 相似文献
102.
103.
TJ Hall M Cooper RG Hughes B Levin DB Skinner AR Moossa 《Canadian Metallurgical Quarterly》1977,134(5):544-548
The clinical, surgical, and pathologic findings in a five year prospective study of 192 patients referred with a high probability of pancreatic cancer are reported. We have defined the requirements of any pancreatic imaging procedure as its ability to distinguish a normal pancreas from pancreatic cancer or chronic pancreatitis and the capability of detecting tumors less than 5 cm in diameter. There was a 47 percent incidence of pancreatic disease (27 percent pancreatic cancer and 20 percent chronic pancreatitis). Prospective radionuclide imaging as routinely performed was found to be of little clinical value in this patient population; it was neither specific nor sensitive to pancreatic cancer or chronic pancreatitis. Preliminary data with longitudinal multiplane emission tomography show an improved diagnostic accuracy and the ability to detect resectable tumors, but its efficacy needs to be prospectively compared with other screening tests on a carefully defined patient population. 相似文献
104.
105.
106.
D Lau BJ Hering A El-Ouaghlidi H Jahr H Brandhorst D Brandhorst R Vietzke K Federlin RG Bretzel 《Canadian Metallurgical Quarterly》1999,77(1):175-177
The shikimate pathway presents an attractive target for malaria chemotherapy. Three shikimic acid analogs exhibited different effects on Plasmodium falciparum growth. (6R)-6-Fluoro-shikimate and (6S)-6-fluoro-shikimate inhibited growth (50% inhibitory concentrations, 1.5 x 10(-5) and 2.7 x 10(-4) M, respectively), whereas 2-fluoro-shikimate had no effect. para-Aminobenzoic acid abrogated the inhibition, demonstrating that the shikimate pathway was specifically targeted. 相似文献
107.
108.
109.
110.
RG Stock K Chan M Terk JK Dewyngaert NN Stone P Dottino 《Canadian Metallurgical Quarterly》1997,37(4):819-825
The authors review the literature on intra-adenomatous pituitary apoplexy with special emphasis on pathophysiology, diagnosis and therapeutic approach. They present five cases, from a series of 86 patients with pituitary tumors, that developed this syndrome. The patients were diagnosed and followed by the Neurosurgery and Endocrinology Services of Hospital Universitario Clementino Fraga Filho, Universidade Federal do Rio de Janeiro. Diagnosis was confirmed by CT-Scan and MRI in all cases, and the treatment of choice was surgical. Conclusions point to the diagnostic difficulties and the urgency of treatment in this clinical setting. 相似文献