全文获取类型
收费全文 | 29104篇 |
免费 | 2280篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 217篇 |
综合类 | 10篇 |
化学工业 | 6296篇 |
金属工艺 | 474篇 |
机械仪表 | 657篇 |
建筑科学 | 902篇 |
矿业工程 | 57篇 |
能源动力 | 620篇 |
轻工业 | 6097篇 |
水利工程 | 356篇 |
石油天然气 | 151篇 |
武器工业 | 1篇 |
无线电 | 1206篇 |
一般工业技术 | 4747篇 |
冶金工业 | 5664篇 |
原子能技术 | 94篇 |
自动化技术 | 3866篇 |
出版年
2024年 | 74篇 |
2023年 | 309篇 |
2022年 | 383篇 |
2021年 | 849篇 |
2020年 | 746篇 |
2019年 | 798篇 |
2018年 | 1339篇 |
2017年 | 1325篇 |
2016年 | 1365篇 |
2015年 | 1054篇 |
2014年 | 1253篇 |
2013年 | 2507篇 |
2012年 | 1940篇 |
2011年 | 1759篇 |
2010年 | 1429篇 |
2009年 | 1250篇 |
2008年 | 1288篇 |
2007年 | 1181篇 |
2006年 | 758篇 |
2005年 | 612篇 |
2004年 | 600篇 |
2003年 | 542篇 |
2002年 | 479篇 |
2001年 | 372篇 |
2000年 | 296篇 |
1999年 | 341篇 |
1998年 | 1994篇 |
1997年 | 1259篇 |
1996年 | 767篇 |
1995年 | 430篇 |
1994年 | 325篇 |
1993年 | 341篇 |
1992年 | 97篇 |
1991年 | 82篇 |
1990年 | 71篇 |
1989年 | 69篇 |
1988年 | 89篇 |
1987年 | 74篇 |
1986年 | 67篇 |
1985年 | 78篇 |
1984年 | 68篇 |
1983年 | 37篇 |
1982年 | 39篇 |
1981年 | 64篇 |
1980年 | 62篇 |
1978年 | 32篇 |
1977年 | 106篇 |
1976年 | 216篇 |
1975年 | 34篇 |
1973年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
162.
V. Ocelík V. Z. Bengus E. B. Korolkova K. Csach J. Miškuf P. Duhaj 《Journal of Materials Science》1991,26(24):6699-6705
The fracture stress and the critical stress intensity factor of the Fe40Ni40B20 amorphous metallic ribbons 20 μm thick were measured in the temperature range 4.2–300 K and at deformation rates from 3.3×10−6 to 1.25×10−3 m−1 with the aim to obtain more information on the condition for the onset and development of the inhomogeneous plastic deformation
and fracture. 相似文献
163.
In this paper, a new approach for powder cold compaction simulations is presented. A density-dependent plastic model within
the framework of finite strain multiplicative hyperelastoplasticity is used to describe the highly nonlinear material behaviour;
the Coulomb dry friction model is used to capture friction effects at die-powder contact; and an Arbitrary Lagrangian–Eulerian
(ALE) formulation is used to avoid the (usual) excessive distortion of Lagrangian meshes caused by large mass fluxes. Several
representative examples, involving structured and unstructured meshes are simulated. The results obtained agree with the experimental
data and other numerical results reported in the literature. It is shown that, contrary to other Lagrangian and adaptive h-remeshing approaches recently reported for this type of problems, the present approach verifies the mass conservation principle
with very low relative errors (less than 1% in all ALE examples and exactly in the pure Lagrangian examples). Moreover, thanks
to the use of an ALE formulation and in contrast with other simulations, the presented density distributions do not present
spurious oscillations.
Received: 20 March 2002 / Accepted: 15 October 2002
The partial financial support of the Ministerio de Ciencia y Tecnología (grant number DPI 2001-2204) is gratefully acknowledged. 相似文献
164.
P. Cañizares J. García-Gómez C. Sáez M.A. Rodrigo 《Journal of Applied Electrochemistry》2003,33(10):917-927
The electrochemical oxidation of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol aqueous wastes using boron-doped diamond electrodes was studied. This treatment led to complete mineralization of the wastes regardless of the operating conditions. A simple mechanistic model is consistent with the voltammetric and electrolysis results. According to this model, the electrochemical treatment of chlorophenol aqueous wastes involves the anodic and cathodic release of chlorine followed by the formation of non-chlorinated aromatic intermediates. Subsequent cleavage of the aromatic ring gives rise to non-chlorinated carboxylic acids. Chlorine atoms arising from the hydrodehalogenation of the chlorophenols are converted into more oxidized molecules at the anode. These molecules react with unsaturated C4 carboxylic acid to finally yield trichloroacetic acid through a haloform reaction. The non-chlorinated organic acids are ultimately oxidized to carbon dioxide and the trichloroacetic acid into carbon dioxide and volatile organo-chlorinated molecules. Both direct and mediated electrochemical oxidation processes are involved in the electrochemical treatment of chlorophenols. 相似文献
165.
Jefferson Fabrício Cardoso Lins Hugo Ricardo Z. Sandim Hans-Jürgen Kestenbach 《Journal of Materials Science》2007,42(16):6572-6577
The present paper reports the experimental results on the microstructural and textural characterization of a hot-rolled IF
steel. The IF steel was hot-rolled in multiple passes in the austenitic field (1,070 °C) followed by air-cooling. SEM, TEM,
and LOM were used to image the microstructure of the material. The global texture was determined by X-ray diffraction (XRD)
technique. The mesotexture of selected regions was investigated by electron backscatter diffraction (EBSD). Results show the
presence of a diffuse (nearly random) and weak texture in the hot-band that consists of recrystallized polygonal grains and
subgrains. The fraction of boundaries with misorientations comprised in the interval 2° ≤ ψ < 15° was found to be lower than
5%. It can be concluded that these low angle boundaries and the presence of subgrains can be associated to the existence of
a few areas softened by recovery during or after hot rolling in austenitic field. 相似文献
166.
Summary The cationic polymerization of 2-ethyl-2-oxazoline using CH3I as initiator at different monomer/initiator ratios, temperatures, solvents and times of polymerization was carried out. The effect of these variables on the polymerization yield and viscosity of the polymers was studied. The poly(N-propionyl)iminoethylene was hydrolyzed in acid medium obtaining a linear poly(ethyleneimine) (PEI). All the polymers were characterized by elemental analysis, IR,1H NMR, and13C NMR spectroscopy. 相似文献
167.
Venezuela's vast natural resource base has largely shaped the nation's economic and energy-use patterns. Major opportunities exist for improving the efficiency of energy use in Venezuela and, consequently, restraining the growth of energy-related carbon emissions. This paper presents a detailed report of one potential development path for Venezuela and estimates the ensuing levels of energy demand and CO2 emissions associated with pursuing this path through the year 2025. The results indicate that by adopting a development strategy that incorporates structural changes in the economy, fuel-switching measures and improved end-use efficiencies, Venezuela can introduce energy efficiency and carbon restraints as part of its economic development process. 相似文献
168.
C Dotres Martínez 《Canadian Metallurgical Quarterly》1995,47(3):150-153
The authors report one case of multiple bilateral hydatid cyst of kidney associated to brain and spleen localizations, after intra cardiac rupture. They point out the rarity of the bilateral kidney localization of hydatidosis, explain the dissemination mode, and stress the role of computed tomography for the pre-operative diagnosis. The treatment is above all surgical and adapted to each case. The post-operative results are satisfying. Complementary medical treatment could be useful. 相似文献
169.
Recent reports have described a pathogenic role of nitric oxide in several respiratory disease. It is specially useful in the adult respiratory distress syndrome, where it acts as a selective vasodilator and improves gas exchange, decreasing pulmonary shunting. Although it has a proven bronchodilator effect, its therapeutic role in diseases such as asthma and chronic limitation of airway flow is not well defined. This article review the metabolism, mechanisms of action, potential uses and adverse effects of nitric oxide in respiratory disease. 相似文献
170.
J Sánchez A Torres J Serrano J Román C Martín L Pérula F Martínez P Gómez 《Canadian Metallurgical Quarterly》1997,20(5):403-408
BACKGROUND: Locally advanced thyroid cancer invading the tracheal cartilage represents a difficult treatment dilemma during thyroidectomy. METHODS: A retrospective chart review was performed to determine the results of laryngotracheal resection or tracheal cartilage shave with adjuvant radiotherapy in patients with locally advanced thyroid cancer invading the upper airway. RESULTS: Of 597 patients undergoing thyroidectomy for thyroid cancer, 40 were found to have laryngotracheal invasion. Thirty-five patients with superficial invasion underwent cartilage shave procedures with adjuvant radiotherapy; five with full-thickness invasion underwent radical resection, including tracheal sleeve resection (n = 3) or total laryngectomy (n = 2). Histologic subtypes included papillary (n = 32), follicular (n = 2), Hurthle cell (n = 1), medullary (n = 3), and anaplastic (n = 2). Of the cartilage shave group, 25 are currently alive with no evidence of disease at a mean follow-up of 81 months (range 1-290). Six developed isolated local/regional recurrence and were managed with total laryngectomy (n = 1), tracheal resection (n = 1), cervical lymphadenectomy (n = 1), or repeat radiotherapy (n = 3). All six patients remain free of disease at a mean follow-up of 5 years. Of those who underwent initial laryngotracheal resection, four remain free of disease at a mean follow-up of 5 years. The rates of 10-year disease-free survival and overall survival for all patients were 47.9% (95% confidence interval [CI] 24.8, 71.0) and 83.9% (95% CI 70.3, 97.5), respectively. CONCLUSIONS: These data suggest that adequate management of thyroid cancer with laryngotracheal invasion can be achieved with a more conservative surgical approach and adjuvant radiotherapy, reserving more radical resections for extensive primary lesions or locally recurrent disease. 相似文献