全文获取类型
收费全文 | 1156篇 |
免费 | 37篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 184篇 |
金属工艺 | 38篇 |
机械仪表 | 50篇 |
建筑科学 | 34篇 |
矿业工程 | 1篇 |
能源动力 | 59篇 |
轻工业 | 102篇 |
水利工程 | 10篇 |
石油天然气 | 18篇 |
无线电 | 136篇 |
一般工业技术 | 170篇 |
冶金工业 | 198篇 |
原子能技术 | 13篇 |
自动化技术 | 167篇 |
出版年
2023年 | 20篇 |
2022年 | 23篇 |
2021年 | 41篇 |
2020年 | 32篇 |
2019年 | 32篇 |
2018年 | 49篇 |
2017年 | 30篇 |
2016年 | 49篇 |
2015年 | 33篇 |
2014年 | 42篇 |
2013年 | 96篇 |
2012年 | 47篇 |
2011年 | 42篇 |
2010年 | 45篇 |
2009年 | 43篇 |
2008年 | 49篇 |
2007年 | 33篇 |
2006年 | 25篇 |
2005年 | 32篇 |
2004年 | 27篇 |
2003年 | 18篇 |
2002年 | 26篇 |
2001年 | 12篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 43篇 |
1997年 | 23篇 |
1996年 | 18篇 |
1995年 | 24篇 |
1994年 | 19篇 |
1993年 | 22篇 |
1992年 | 10篇 |
1991年 | 13篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 4篇 |
1972年 | 6篇 |
排序方式: 共有1195条查询结果,搜索用时 46 毫秒
1.
Chemical engineering systems often involve a functional porous medium, such as in catalyzed reactive flows, fluid purifiers, and chromatographic separations. Ideally, the flow rates throughout the porous medium are uniform, and all portions of the medium contribute efficiently to its function. The permeability is a property of a porous medium that depends on pore geometry and relates flow rate to pressure drop. Additive manufacturing techniques raise the possibilities that permeability can be arbitrarily specified in three dimensions, and that a broader range of permeabilities can be achieved than by traditional manufacturing methods. Using numerical optimization methods, we show that designs with spatially varying permeability can achieve greater flow uniformity than designs with uniform permeability. We consider geometries involving hemispherical regions that distribute flow, as in many glass chromatography columns. By several measures, significant improvements in flow uniformity can be obtained by modifying permeability only near the inlet and outlet. 相似文献
2.
Anis Zeglaoui Anouar Houmia Maher Mejai Radhouane Aloui 《International Journal of Adaptive Control and Signal Processing》2021,35(9):1842-1859
In compressive sampling theory, the least absolute shrinkage and selection operator (LASSO) is a representative problem. Nevertheless, the non-differentiable constraint impedes the use of Lagrange programming neural networks (LPNNs). We present in this article the -LPNN model, a novel algorithm that tackles the LASSO minimization together with the underlying theory support. First, we design a sequence of smooth constrained optimization problems, by introducing a convenient differentiable approximation to the non-differentiable -norm constraint. Next, we prove that the optimal solutions of the regularized intermediate problems converge to the optimal sparse signal for the LASSO. Then, for every regularized problem from the sequence, the -LPNN dynamic model is derived, and the asymptotic stability of its equilibrium state is established as well. Finally, numerical simulations are carried out to compare the performance of the proposed -LPNN algorithm with both the LASSO-LPNN model and a standard digital method. 相似文献
3.
The Journal of Supercomputing - Data center network virtualization is being considered as a promising technology to provide a performance guarantee for cloud computing applications. One important... 相似文献
4.
Abdeljaoued Emna Brulé Mathieu Tayibi Saida Manolakos Dimitris Oukarroum Abdallah Monlau Florian Barakat Abdellatif 《Clean Technologies and Environmental Policy》2020,22(10):1967-1997
Clean Technologies and Environmental Policy - Biochar has caught great attention over the last decade, yielding a large number of publications in a broad range of disciplines. This scientometric... 相似文献
5.
Maher M. Osman Mounir M. Abd El-Malek Aida B. Tadros Atef M. Michael 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):46-52
4-Amino-3-thio-1,24-triazolidine (L1) and 4-amino-5-thio-1,3,4-thiadiazole (LII) as well as their metal complexes of the general formulae MLI·2H2O and MLIICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(LI)2·2H2O and SnLIICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae. 相似文献
6.
7.
8.
9.
PH Benhamou N Kalach J Raymond C Abdallah C Dupont 《Canadian Metallurgical Quarterly》1994,23(37):1703-1707
OBJECTIVES: Numerous reports have established the association of Helicobacter pylori and recurrent abdominal pain in children. We investigated the clinical, bacteriological and therapeutic features of our patients seen over a 1 year period. METHODS: We investigated 121 children during 1992 in Hospital Saint Vincent-de-Paul, Paris. At endoscopy, biopsies were taken and sent for histology and bacteriology and urease testing. A decision regarding treatment by amoxicillin and metronidazol was made after positive results of bacteriology and/or histology. RESULTS: Heliobacter pylori was found in 47 antral biopsies after pathology examination with Giemsa staining alone 16 times, bacterial culture 9 times and both methods 22 times. Abdominal pain was the prominent symptom, occurring in 35.5% of Helicobacter pylori+patients. In 25 of the positive negative patients, a nodular gastritis was observed (53.1%) and in 27.6% of them a weight loss or a delay in weight gain. Few patients became after combined treatment with amoxicillin and metronidazol whereas eradication rates after triple therapy with amoxicillin-metronidazol and H2 antagonist or proton pump blocker were higher. CONCLUSION: Helicobacter pylori related gastritis is a common cause of abdominal complaints in children. The most common symptom is recurrent abdominal pain. Antral nodularity is a peculiar endoscopic finding in children. Two-drug therapy associating amoxicillin-metronidazol is often ineffective to eradicate the bacteria whereas eradication rates after triple therapy amoxicillin-metronidazol and H2 antagonist or proton pump blocker are higher. 相似文献
10.
S. P. Ashburn M. C. Öztürk J. J. Wortman G. Harris J. Honeycutt D. M. Maher 《Journal of Electronic Materials》1992,21(1):81-86
Titanium and cobalt germanides have been formed on Si (100) substrates using rapid thermal processing. Germanium was deposited
by rapid thermal chemical vapor deposition prior to metal evaporation. Solid phase reactions were then performed using rapid
thermal annealing in either Ar or N2 ambients. Germanide formation has been found to occur in a manner similar to the formation of corresponding silicides. The
sheet resistance was found to be dependent on annealing ambient (Ar or N2) for titanium germanide formation, but not for cobalt germanide formation. The resistivities of titanium and cobalt germanides
were found to be 20 μΩ-cm and 35.3μΩ-cm, corresponding to TiGe2 and Co2Ge, respectively. During solid phase reactions of Ti with Ge, we have found that the Ti6Ge5 phase forms prior to TiGe2. The TiGe2 phase was found to form approximately at 800° C. Cobalt germanide formation was found to occur at relatively low temperatures
(425° C); however, the stability of the material is poor at elevated temperatures. 相似文献