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   363篇
  免费   4篇
电工技术   13篇
化学工业   92篇
金属工艺   10篇
机械仪表   3篇
建筑科学   1篇
能源动力   9篇
轻工业   21篇
水利工程   2篇
无线电   58篇
一般工业技术   50篇
冶金工业   86篇
原子能技术   8篇
自动化技术   14篇
  2023年   1篇
  2022年   1篇
  2021年   4篇
  2019年   1篇
  2018年   2篇
  2017年   3篇
  2016年   1篇
  2015年   2篇
  2014年   6篇
  2013年   10篇
  2012年   9篇
  2011年   8篇
  2010年   17篇
  2009年   9篇
  2008年   8篇
  2007年   13篇
  2006年   10篇
  2005年   9篇
  2004年   9篇
  2003年   7篇
  2002年   12篇
  2001年   13篇
  2000年   4篇
  1999年   6篇
  1998年   30篇
  1997年   22篇
  1996年   16篇
  1995年   12篇
  1994年   17篇
  1993年   10篇
  1992年   8篇
  1991年   6篇
  1990年   3篇
  1989年   3篇
  1988年   7篇
  1987年   4篇
  1986年   4篇
  1985年   13篇
  1984年   4篇
  1983年   10篇
  1982年   6篇
  1981年   4篇
  1980年   5篇
  1979年   3篇
  1978年   3篇
  1977年   2篇
  1976年   6篇
  1974年   1篇
  1973年   1篇
  1971年   2篇
排序方式: 共有367条查询结果,搜索用时 15 毫秒
1.
The problem of model selection, or determination of the number of hidden units, can be approached statistically, by generalizing Akaike's information criterion (AIC) to be applicable to unfaithful (i.e., unrealizable) models with general loss criteria including regularization terms. The relation between the training error and the generalization error is studied in terms of the number of the training examples and the complexity of a network which reduces to the number of parameters in the ordinary statistical theory of AIC. This relation leads to a new network information criterion which is useful for selecting the optimal network model based on a given training set.  相似文献   
2.
As a model for organic ferromagnetism in a one-dimensional system, substituted polyacetylenes are re-considered on the basis of the molecular orbital (MO) and the crystal orbital (CO) methods. The semiempirical MO calculations with configuration interaction for the dimer model show that the exchange interaction on poly[(4-oxyphenyl)acetylene] (1) is negative in spite of Ovchinnikov's prediction, due to the direct interaction between the adjacent pendant spins. On the other hand, it is shown that a polyacetylene chain with phenoxy radicals as pendants on every other active site can become a one-dimensional feromagnet. Moreover, the CO calculations by means of the unrestricted Hartree-Fock method give a theoretical background for the realization of a ground state with macroscopic spin alignment on the improved model chain.  相似文献   
3.
4.
5.
The feasibility of a solid polymer electrolyte (SPE) method for Kolbe type reactions was investigated by using Pt-SPE composed with Nafion 415 and platinum. The Kolbe reaction of acetic acid proceeded effectively on one side and both sides Pt-SPE composites. The lower current efficiency was observed on the latter than on the former. Neat acetic acid could also be electrolysed on both sides SPE though the cell voltage was fairly high.A methanolic solution of monomethyl adipate was electrolysed to give dimethyl sebacate on both sides Pt-SPE according to the Brown-Walker reaction. The current efficiency and the terminal voltage increased with the concentration of monomethyl adipate. Pt-SPE behaved as an active electrode of a high roughness factor, eg about 6, for the Kolbe reaction of acetate.  相似文献   
6.
In the copolymerization of phenylacetylene with various acetylenes catalysed by WCl6·Ph4Sn, the relative reactivity of monomer decreased with increasing steric effect of monomer, e.g. HC  Cn-Bu, HC  Cn-Hex > HC  CPh, HC  Cs-Bu > HC  Ct-Bu, MeCCPh, CICCPh. While 1-chloro-2-phenylacetylene (a disubstituted acetylene) showed high reactivity in the homopolymerization by Mobased catalysts, the reactivity was remarkably depressed in the presence of phenylacetylene as comonomer. Based on these results, the relative reactivity of the acetylenic monomers in copolymerization was explained in terms of competitive coordination of monomers to the propagating end.  相似文献   
7.
The mechanical properties of a textured alumina made by high-temperature deformation of normal-purity sintered alumina have been investigated. The textured alumina shows very high bending strength and extremely high fracture toughness. Fracture toughness of more than 10 MPa·m1/2 was measured by the single-edge precracked beam method, and even using the single-edge V-notched beam method, toughness of over 8 MPa·m1/2 was obtained. This high fracture toughness was attributed to a large number of aligned small platelike grains of the textured structure enhancing the grain bridging effect.  相似文献   
8.
International Journal of Information Security - Card-based cryptography is an attractive and unconventional computation model; it provides secure computing methods using a deck of physical cards....  相似文献   
9.
An integrated optical-disk pickup that uses a focusing grating coupler with a numerical aperture of 0.45 (a focal length of 1.0 mm and an aperture of 1.0 mm × 0.8 mm) was developed, and the readout signal on an International Standards Organization (ISO) -formatted 90-mm optical disk was detected by the pickup. The signal-amplitude ratio of the minimum-limit data pattern to the maximum was 0.53 on the innermost track. It meets the requirement on the signal resolution for optical-disk storage devices.  相似文献   
10.
Very large macrophages, which we have termed "giant macrophages" (G-M phi), have been found in renal tubules, some containing cytoplasmic vacuoles. To elucidate their pathophysiological roles, we examined renal biopsy tissues from various primary glomerulonephritis (GN) and tubulointerstitial nephritis (TIN) using immunohistochemistry with monoclonal antibodies against M phi and other cell surface markers. Giant macrophages were absent or rare in TIN, minimal change nephrotic syndrome, and minor glomerular abnormalities, but G-M phi was plentiful in progressive glomerulonephrides such as IgA nephropathy with crescents, membranoproliferative GN, focal segmental glomerulosclerosis, and especially in crescentic GN. These G-M phi were usually seen in the lumen of renal tubules, but occasionally were found in the Bowman's spaces and glomerular tufts, and similar cells were also found in urine. Moreover, they frequently made contact with tubular epithelial cells expressing intercellular adhesion molecule-1, and the tubular epithelial cells in such lesions often had degenerative changes. Giant M phi may damage tubular epithelial cells from the luminal side. Phenotypically, G-M phi showed activated (CD71+) and mature (25F9+) characteristics along with features of M phi (CD68+), and the cytoplasm contained a great deal of lipids. The numbers of G-M phi in renal tissues closely correlated with the degree of hematuria (rho = 0.5, P < 0.001), serum creatinine value (r = 0.63, P < 0.001) in GN patients (N = 96) and with proteinuria in IgA nephropathy patients (r = 0.89, P < 0.001, N = 27). These data suggest that G-M phi are M phi that were activated and matured in certain active inflammatory sites, which flowed into tubules and then into urine. Thus, the existence of G-M phi in biopsy tissue or urine reflect the activity of GN and may have a predictive value for the progression of GN.  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