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   725篇
  免费   31篇
  国内免费   1篇
电工技术   6篇
综合类   4篇
化学工业   214篇
金属工艺   10篇
机械仪表   7篇
建筑科学   28篇
能源动力   4篇
轻工业   137篇
水利工程   7篇
石油天然气   1篇
无线电   44篇
一般工业技术   140篇
冶金工业   70篇
原子能技术   2篇
自动化技术   83篇
  2023年   8篇
  2022年   17篇
  2021年   13篇
  2020年   14篇
  2019年   19篇
  2018年   15篇
  2017年   20篇
  2016年   24篇
  2015年   22篇
  2014年   19篇
  2013年   27篇
  2012年   31篇
  2011年   59篇
  2010年   35篇
  2009年   29篇
  2008年   40篇
  2007年   22篇
  2006年   27篇
  2005年   29篇
  2004年   29篇
  2003年   15篇
  2002年   17篇
  2001年   13篇
  2000年   11篇
  1999年   5篇
  1998年   16篇
  1997年   14篇
  1996年   11篇
  1995年   16篇
  1994年   14篇
  1993年   15篇
  1992年   10篇
  1991年   14篇
  1990年   5篇
  1989年   3篇
  1988年   12篇
  1987年   4篇
  1984年   5篇
  1983年   7篇
  1982年   6篇
  1981年   7篇
  1980年   2篇
  1978年   2篇
  1977年   4篇
  1976年   3篇
  1975年   3篇
  1974年   7篇
  1973年   4篇
  1970年   4篇
  1968年   2篇
排序方式: 共有757条查询结果,搜索用时 15 毫秒
41.
CY Genton  M Dutoit  L Portmann  M Gillet  L Guillou 《Canadian Metallurgical Quarterly》1998,194(12):861-3; discussion 865-6
This case report concerns a 64 year-old woman who presented a pathologic fracture of the femur neck. Histologic examination of the performed bone biopsy disclosed the presence of a carcinomatous metastasis with unusual microscopic features. The site of the primary tumor could be unequivocally determined as being the thyroid gland, as immunostaining of the tumor cells showed positivity with anti-thyroglobulin. The thyroidectomy specimen weighed 149 g, was nodular and partially calcified. Exhaustive microscopic examination finally revealed the presence of a minute columnar cell carcinoma, 0.6 cm in diameter, with obvious vascular invasion. This case illustrates well 1) the usefulness of immunostaining with anti-thyroglobulin in cases of bone metastasis with unusual microscopic features and unknown primary, as well as 2) the aggressiveness of this rare type of carcinoma of the thyroid.  相似文献   
42.
Hydrogen induced stress corrosion cracking of non galvanized and galvanized construction steels The processes of atmospheric corrosion and corrosion in collected water which may lead to hydrogen induced stress corrosion cracking of high-strength reinforcing steels in casing tubes before injection with concrete are discussed. Hydrogen uptake during corrosion occurs in weakly acid solutions as well as in neutral or alkaline aqueous solutions. The hydrogen uptake by proton discharge in acid solutions decreases with increasing pH of the electrolyte. Hydrogen can also be absorbed in neutral to weakly alkaline solutions if steels are plastically deformed and water reacts with the fresh iron surface. In alkaline solutions, hydrogen uptake is possible if, at the generally passivated steel surface, localized corrosion (pitting or crevice corrosion), local galvanic cells and a sufficient decrease in the pH of the pit electrolyte occurs. In the case of galvanized steels with damaged zinc layers, hydrogen uptake may result from the cathodic polarization of the free steel surface by zinc dissolution. The absorbed hydrogen interacts with the microstructure of the steels and weakens the bonds between the iron atoms. The influence of the microstructure of high-strength steels on the fracture behaviour is discussed on the basic of the so-called decohesion theory.  相似文献   
43.
A three-factor factorial experiment was performed to assess the efficiency of lipid extraction from the back of human volunteers. Chloroform-methanol (2:1 v/v) proved substantially superior to acetone or diethyl ether. The latter two solvents were also significantly more efficient than n-hexane. The implication of the findings is discussed with regard to the isolation and characterization of fungistatic and bacteriostatic agents on the surface of the skin.  相似文献   
44.
The authors report of three cases of medullary carcinoma of the thyroid and, from a review of the literature, study the definition, frequency, embryological and etiological characteristics of this disease. The physiology of thyrocalcitonin, the concept of the APUD system the secretion of active substances by the tumour cells are considered. The macroscopic and microscopic characteristics and its mode of spread are described. The two main clinical forms, the sporadic form and the familial form are described together with the other endocrine involvements. Among the factors in positive diagnosis, accent is placed on per-operative histological examination and on biological tests of familial detection. Among the forms of treatment the essential place of surgery explains partly the relatively favourable course and prognosis of the malignant disease.  相似文献   
45.
We describe and discuss the properties of a binary neural network that can serve as a dynamic neural filter (DNF), which maps regions of input space into spatiotemporal sequences of neuronal activity. Both deterministic and stochastic dynamics are studied, allowing the investigation of the stability of spatiotemporal sequences under noisy conditions. We define a measure of the coding capacity of a DNF and develop an algorithm for constructing a DNF that can serve as a source of given codes. On the basis of this algorithm, we suggest using a minimal DNF capable of generating observed sequences as a measure of complexity of spatiotemporal data. This measure is applied to experimental observations in the locust olfactory system, whose reverberating local field potential provides a natural temporal scale allowing the use of a binary DNF. For random synaptic matrices, a DNF can generate very large cycles, thus becoming an efficient tool for producing spatiotemporal codes. The latter can be stabilized by applying to the parameters of the DNF a learning algorithm with suitable margins.  相似文献   
46.
This article presents a collection of regional science books that longstanding members of the Regional Science Association International (RSAI) identified as path-breaking books. The most frequently nominated books include the classics by Isard, the seminal books in urban economics by Alonso, Muth and Mills, methods books by Miernyk, Wilson, Anselin, and Cliff and Ord, textbooks by Beckmann and Richardson, as well as the recent contribution by Fujita, Krugman and Venables. Reviews of these books, written by leading scholars from different continents, make up the major contribution of this article and are a testimony to the far-reaching influence of regional science in the academic literature.JEL Classification: A2, B2, B3, C00, R00With contributions by Michael Batty, Manas Chatterji, Kieran Donaghy, Bernard Fingleton, Arthur Getis, Michael J. Greenwood, Daniel P. McMillen, Gordon F. Mulligan, Jan Oosterhaven,Peter V. Schaeffer, Daniel Shefer. See the Appendix for contributors affiliations and contact information.  相似文献   
47.
For provenance assignments of wines strontium isotope ratios can be used because soils from different wine-growing regions, and hence the wines grown there, each show specific ratios. Some successful applications are demonstrated.
87Sr/86Sr aus Gestein und Boden in Rebe und Wein
Zusammenfassung Zur Herkunftsbestimmung von Weinen können Strontium-Isotopenverhältnisse herangezogen werden, da die Böden verschiedener Weinbaugebiete, und damit die dort gezogenen Weine, jeweils spezifische Verhältnisse aufweisen. Einige erfolgreiche Anwendungen werden demonstriert.
  相似文献   
48.
We present numerical results obtained by 3D-BPM concerning evanescent field coupling in monomode fibres. At first we study the coupling between a monomode fibre and a mode sink. We show the existence or the absence of guided modes. BPM, is also applied to the study of directional couplers consisting of two fibres separated by an index liquid. The transmission coefficient is computed for various geometries and the electric field intensity is visualised by plotting isovalues.  相似文献   
49.
50.
To evaluate the ability of MR T2 mapping (8.5 T) to characterize ex vivo longitudinally, morphologically and quantitatively, alginate-based tissue engineering in a rat model of patellar cartilage chondral focal defect. Calibrated rat patellar cartilage defects (1.3 mm) were created at day 0 (D0) and alginate sponge with (Sp/C+) or without (Sp/C–) autologous chondrocytes were implanted. Animals were sacrificed sequentially at D20, D40 and D60 after surgery and dissected patellae underwent MRI exploration (8.5 T). T2 values were calculated from eight SE images by using nonlinear least-squares curve fitting on a pixel-by-pixel basis (constant repetition time of 1.5 s, eight different echo times: 5.5, 7.5, 10.5, 12.5, 15.0, 20.0, 25.0 and 30.0 ms). On the T2 map, acquired in a transversal plane through the repair zone, global T2 values and zonal variation of T2 values of repair tissue were evaluated versus control group and compared with macroscopic score and histological studies (toluidine blue, sirius red and hematoxylin-eosin). Partial, total and hypertrophic repair patterns were identified. At D40 and D60, Sp/C+ group was characterized by a higher proportion of total repair in comparison to Sp/C– group. At D60, the proportion of hypertrophic repair was two fold in Sp/C– group versus Sp/C+ group. As confirmed morphologically and histologically, the T2 map also permitted the distinction of three types of repair tissue: total, partial and hypertrophic. Total repair tissue was characterized by high T2 values versus normal cartilage (p<0.05). Zonal variation, reflecting the collagen network organization, appeared only at D60 for Sp/C+ group (p<0.05). Hypertrophic tissue, mainly observed at D60, presented high T2 global values without zonal variation with cartilage depth. These results confirm the potency of the MR T2 map (8.5 T) to characterize macroscopically and microscopically the patterns of the scaffold guided-tissue repair of a focal chondral lesion in the rat patella (total, partial and hypertrophic). On T2 map, three parameters (i.e. MRI macroscopic pattern, T2 global values and zonal variation of T2 values) permit to characterize chondral repair tissue, as a virtual biopsy.  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