全文获取类型
收费全文 | 377篇 |
免费 | 7篇 |
专业分类
电工技术 | 1篇 |
综合类 | 1篇 |
化学工业 | 125篇 |
金属工艺 | 5篇 |
机械仪表 | 10篇 |
建筑科学 | 17篇 |
能源动力 | 15篇 |
轻工业 | 25篇 |
水利工程 | 4篇 |
无线电 | 29篇 |
一般工业技术 | 44篇 |
冶金工业 | 46篇 |
原子能技术 | 1篇 |
自动化技术 | 61篇 |
出版年
2023年 | 3篇 |
2022年 | 16篇 |
2021年 | 17篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 14篇 |
2017年 | 15篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 23篇 |
2012年 | 14篇 |
2011年 | 25篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 20篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 11篇 |
1998年 | 17篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有384条查询结果,搜索用时 15 毫秒
41.
KI el-Noueam V Giuliano ME Schweitzer BJ O''Hara 《Canadian Metallurgical Quarterly》1997,21(5):796-799
A 62-year-old female who had a complaint of palpitation was diagnosed as bicuspid aortic stenosis and left single coronary artery by the echocardiographic examination, cardiac catheterization study and coronary artery angiography. Aortic valve replacement was performed and the patient was discharged 22 days after surgery with good post-operative course. Preoperative coronary artery angiography was important in the case of aortic valvular disease. 相似文献
42.
An ultrastructural study of spermiogenesis in two species of Sitophilus (Coleoptera: Curculionidae).
Khesller Patrícia Olázia Name Giuliano Pagy Felipe dos Reis S?nia Nair Báo 《Biocell》2007,31(2):229-236
The spermiogenesis of Sitophilus zeamais and Sitophilus oryzae, the maize and the rice weevil, respectively, was studied by light microscopy and scanning and transmission electron microscopy. Sitophilus spp. is the most widespread and destructive primary pest of stored cereals in the world. The spermiogenesis occurs within cysts. There are approximately 256 germ line cells per cyst. Inside each cysts, all the spermatids are in the same stage of maturation. The ultrastructure of the spermatozoa of S. zeamais and S. oryzae is similar to that described for other beetles. The head is formed by a three-layered acrosome with the perforatorium, the acrosomal vesicle, the extra-acrosomal layer and the nucleus. The flagellum has the typical axoneme formed by a 9+9+2 microtubules arrangement, two mitochondrial derivatives and two accessory bodies. The typical pattern for Curculionidae spermatozoa described here may provide useful information for future phylogenetic analysis of the superfamily Curculionoidea. 相似文献
43.
Magnetic resonance imaging findings of median nerve hamartoma are presented in three patients with palpable wrist masses and median neuropathy. Fat-suppressed T1-weighted images demonstrated adipose tissue separating the neural and fibrous tissue bundles in two of three patients, which results in the distinctive appearance of these tumors on magnetic resonance imaging. Fibrous tissue appeared as enhancing longitudinal bundles within the tumor on gadolinium enhanced fat-suppressed T1-weighted images. 相似文献
44.
A neural networks approach is applied to the derivation of the operating rules of an irrigation supply reservoir. Operating rules are determined as a two step process: first, a dynamic programming technique, which determines the optimal releases byminimizing the sum of squared deficits, assumed as objective function, subject to various constraints is applied. Then, theresulting releases from the reservoir are expressed as a functionof significant variables by neural networks. Neural networks aretrained on a long period, including severe drought events, andthe operation rules so determined are validated on a differentshorter period. The behaviour of different operating rules is assessed by simulating reservoir operation and by computing several performance indices of the reservoir and crop yield through a soil water balance model. Results show that operating rules based on an optimization with constraints resembling real system operation criteria lead to a good performance both in normal and in drought periods, reducing maximum deficits and water spills. 相似文献
45.
Nonlinear absorption of light: Optical saturation of electronic transitions in organic molecules with high intensity laser radiation 总被引:1,自引:0,他引:1
A review of spectroscopic properties of complex molecules is presented and used to show that a simple two-level scheme is inadequate to describe the optical bleaching of dye molecules. Experimental data are reported for the transmission of intense ruby laser radiation by several types of dyes. Rate equation analyses are carried out using steady-state solutions and iterative computer solutions; calculated bleaching curves are compared with our data for cryptocyanine. On these bases, we show that, in general, the optical bleaching process involves the removal of ground-state molecules to other states having smaller absorption cross sections at the exciting frequency, and that recovery of absorption at this frequency is characterized by a complex relaxation mechanism. 相似文献
46.
Sulfur-bridged polyaniline coatings are obtained onto Fe anodes by electrolyzing a basic solution of one aniline and ammonium sulfide. Their sulfur content ranges from 7% to 17%, depending on the substituents on aniline. Variously substituted anilines may be polymerized in this way and coating pollution by azobenzene formed in a side reaction is almost completely avoided. Sulfur probably enters the polymer chains through a free radical mechanism. HS? intermediates being formed by both homogeneous and anodic oxidation of HS? anions. Coatings from N-allylaniline, being thermally curable, show satisfactory physical properties. 相似文献
47.
48.
In this work a Sulzer structured packing, Mellapak 250Y, was studied for applications in the field of absorption. A new model was proposed which makes it possible to estimate the packing surface that actually takes part in the process. In the course of these studies, new experimental data were obtained relating to the absorption of 1,1,1-trichloroethane using Genosorb 300, a mixture of polyethylene glycol dimethyl ethers produced by Hoechst S.p.A., as absorption liquid. The results obtained with the proposed model are in agreement both with the experimental measurements made in the course of the work and with experimental absorption measurements reported by other authors on water systems. 相似文献
49.
50.
Compared with control birds receiving ad libitum free-water, the total water intake of male and female northern bobwhite declined when only mealworms were available as a source of water. Male northern bobwhite sustained tissue mass and reproductive function with mealworms as their only source of water. Female northern bobwhite could not sustain body, ovary, and oviduct mass, and rate of egg production with mealworms as their only source of water. We suggest that, without free-water, breeding females require a diet with a water:dry matter ratio of greater than 1:1.29 (> 44% water). 相似文献