全文获取类型
收费全文 | 418篇 |
免费 | 43篇 |
专业分类
电工技术 | 1篇 |
综合类 | 2篇 |
化学工业 | 136篇 |
金属工艺 | 2篇 |
机械仪表 | 14篇 |
建筑科学 | 28篇 |
矿业工程 | 1篇 |
能源动力 | 9篇 |
轻工业 | 90篇 |
水利工程 | 4篇 |
无线电 | 15篇 |
一般工业技术 | 65篇 |
冶金工业 | 54篇 |
原子能技术 | 2篇 |
自动化技术 | 38篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 18篇 |
2021年 | 28篇 |
2020年 | 16篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 20篇 |
2016年 | 24篇 |
2015年 | 17篇 |
2014年 | 24篇 |
2013年 | 36篇 |
2012年 | 27篇 |
2011年 | 38篇 |
2010年 | 26篇 |
2009年 | 20篇 |
2008年 | 19篇 |
2007年 | 13篇 |
2006年 | 10篇 |
2005年 | 11篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1969年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有461条查询结果,搜索用时 15 毫秒
41.
The Maglev vehicle Transrapid is levitated by magnetic forces which pull the vehicles levitation frames toward the guideway
from below. The magnets possess poles with alternating fluxes which are part of the synchronous long stator linear motor.
Although the Transrapid glides along its guideway without mechanical contact, this alternation as well as the loading and
unloading of the guideway girders excite vibrations of the ground. In order to calculate the time behavior of the vibrational
emissions, a simulation of the transfer of a Transrapid vehicle over several guideway girders is proposed. The equations of
motion for the vehicle and the girders are calculated separately by the MBS software NEWEUL and assembled and numerically
integrated in MATLAB/SIMULINK. The control law for the magnet forces is simplified by the characteristics of linear spring-damper
elements. The controlled magnet forces travel along the guideway continuously and include the dynamic component due to the
alternating fluxes and the geometry of the poles and stator. Results of a complete vehicle moving along a guideway consisting
of several girders can be obtained within a few minutes of computation time. Therefore, the mechanism of excitations can be
analyzed by numerical time integration in the full state space. The results are validated by measurements of the forces in
the joints of the guideway girders. The vibrational emission along the Transrapid guideway differs from the vibrations of
contact-afflicted vehicles as no impacts and fewer stochastic effects occur. 相似文献
42.
Silvia Patricia Galíndez‐Nájera Oswaldo Ramos‐Monroy Nora Ruiz‐Ordaz Angélica Salmerón‐Alcocer Cleotilde Juárez‐Ramírez Deifilia Ahuatzi‐Chacón Everardo Curiel‐Quesada Juvencio Galíndez‐Mayer 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(4):554-561
BACKGROUND: The impact of mixtures of chloro‐triazinic herbicides, such as atrazine and simazine, on aquatic ecosystems is of environmental concern. To study their biodegradation under various operational conditions, a binary community comprising Stenotrophomonas maltophilia and Arthrobacter sp. attached to the porous support of a packed bed reactor, was evaluated. RESULTS: The genetic analysis of the two atrazine‐degrading strains revealed that genes atzA, atzB, atzC are present in both bacteria, but only S. maltophilia possess atzD. Thus, by cultivating Arthrobacter sp. on these herbicides, cyanuric acid accumulation was observed. When the binary community was cultivated in the biofilm reactor, at all the loading rates probed, both herbicides were entirely removed. However, complete biodegradation of cyanuric acid was not achieved. CONCLUSIONS: Even with a two‐stage reactor, cyanuric acid was only partially removed. This fact could be attributed to the absence, in the second stage, of an easily degradable energy source, required by S. maltophilia for the uptake and cometabolic degradation of the recalcitrant heterocyclic ring. Responding to differences in nutritional conditions prevailing at each reactor stage, local differences in species' predominance were clearly detected by microbiological and molecular biology methods. Copyright © 2010 Society of Chemical Industry 相似文献
43.
Nasdala L Ruschel K Rhede D Wirth R Kerschhofer-Wallner L Kennedy AK Kinny PD Finger F Groschopf N 《Chimia》2010,64(10):705-711
The internal textures of crystals of moderately radiation-damaged monazite-(Ce) from Moss, Norway, indicate heavy, secondary chemical alteration. In fact, the cm-sized specimens are no longer mono-mineral monazite but rather a composite consisting of monazite-(Ce) and apatite pervaded by several generations of fractures filled with sulphides and a phase rich in Th, Y, and Si. This composite is virtually a 'pseudomorph' after primary euhedral monazite crystals whose faces are still well preserved. The chemical alteration has resulted in major reworking and decomposition of the primary crystals, with potentially uncontrolled elemental changes, including extensive release of Th from the primary monazite and local redeposition of radionuclides in fracture fillings. This seems to question the general alteration-resistance of orthophosphate phases in a low-temperature, 'wet' environment, and hence their suitability as potential host ceramics for the long-term immobilisation of radioactive waste. 相似文献
44.
Ainhoa Fernández-Tena Itziar Otaegi Lourdes Irusta Victor Sebastián Gonzalo Guerrica-Echevarria Alejandro Jesus Müller Nora Aranburu 《大分子材料与工程》2023,308(12):2300213
In this work, the effectiveness of seven commercial compatibilizers is tested in polylactide (PLA)/poly(ε-caprolactone) (PCL) blends with different compositions to obtain a high-impact PLA. None of the compatibilizers is effective for 90/10 and 80/20 PLA/PCL compositions, as no improvement of the impact strength is observed. For the 70/30 composition, compatibilizers having glycidyl methacrylate (GMA) and acrylate groups in their structure are proved the most effective, as the morphological change towards co-continuity induced by them leads to significant impact strength improvements (of ≈345% and 90% with respect to the neat PLA and the noncompatibilized PLA/PCL 70/30 blend, respectively). The 70/30 PLA/PCL composition, as it shows the best balance of properties, and the best compatibilizer (ElvaloyPTW) are chosen to carry out the optimization of the compatibilizer content. It is found that adding 6 phr to the blend results in highly toughened and ductile blends while maintaining a high modulus and yield strength values. Larger compatibilizer contents lead to even higher impact strength values, but the low-strain mechanical properties are notably reduced. Thus, in this work, a simple and easily scalable method to produce high-impact PLA is shown, as it implies the compounding of three commercially available components without involving any toxic solvents. 相似文献
45.
Carlo Alberto Biffi Paola Bassani Marco Carnevale Nora Lecis Antonietta Loconte Barbara Previtali Ausonio Tuissi 《Metals and Materials International》2014,20(1):83-92
The machining of shape memory alloys (SMAs), such as NiTi based alloys, is a very interesting and relevant topic for several industrial applications in the biomedical, sensor and actuator fields. Laser technology is one of the most suitable methods for the manufacturing of products in the aforementioned fields, mainly when small and precise features have to be included. Due to the thermal nature of this process, study of its effect on the functional properties of these materials is needed. Except for binary NiTi, few results on the laser machining of NiTi based alloys are available in the literature. In this work, thin sheets of Ni40Ti50Cu10 (at.%) were processed by a fibre laser and the effect of process speed on the material properties was analysed. Scanning electronic microscopy was adopted for observation of the laser cut edges’ morphology. Chemical composition of the processed material was evaluated by energy dispersion spectroscopy and nanohardness measurements were used to estimate the heat affected zone. SMA functional properties were studied on both base and laser machined material. These characteristics are affected by laser machining for the presence of melted material; this effect can be minimised by increasing the laser process speed. 相似文献
46.
Pablo C. L'Argentiere Nora S. Fígoli 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1990,48(3):361-368
The poisoning of a commercial Pd/Al2O3 catalyst by pyridine and thiophene during the selective hydrogenation of styrene to ethylbenzene was studied. It was found that the Pd electronic state is the main factor controlling the interaction between the metal and the poisons. Pyridine added to the non-poisoned feed in a pulse produces a modification in the Pd electronic state and a decrease in conversion, but, within certain limits, inhibits the adsorption of more pyridine or thiophene molecules. 相似文献
47.
A Piattelli A Scarano A Dalla Nora G De Bona GA Favero 《Canadian Metallurgical Quarterly》1998,19(7-9):643-649
The authors present a histologic analysis of 19 Branemark titanium implants retrieved for different causes: four implants were removed for abutment fracture, one for dental nerve dysesthesia, two for bone overheating, two for peri-implantitis, nine for mobility, one for unknown causes. In the implants removed for fracture a high bone-implant contact percentage was present (71.83 +/- 4.96%) with compact, mature bone at the interface. The picture of the failure due to bone overheating was characteristic with the presence of bone sequestra and of a gap between implant and bone filled by lymphocytes and plasma cells: many bacteria surrounded the necrotic bone and no newly regenerated bone was present. In peri-implantitis an inflammatory infiltrate was observed in the peri-implant tissues: a dense fibrous connective tissue was present around implants failed for mobility. The microscopical picture is certainly extremely important in identifying the causal determinants of an implant failure. 相似文献
48.
C. A. Macias-Chapula Irma P. Rodea-Castro Nora Narvaez-Berthelemot 《Scientometrics》1998,41(1-2):41-49
This work reports on the preliminary results of a bibliometric analysis of AIDS literature, as produced in or about Latin
America and the Caribbean for the period 1980–1996. Two international and two regional secondary sources were used in order
to obtain comparative analyses regarding for example, comprehensiveness of AIDS literature coverage and local/main frame visibility.
Less than 1000 records were retrieved from each of the databases searched. Leading countries in AIDSLINE were Haiti, Brasil,
Mexico and Puerto Rico. The distribution by year of publication showed a decrease in Haiti records, from 54 in 1983, to 4
in 1995. The rest of the countries either increased or maintained an average production throughout the years. Regional secondary
information sources were less current and comprehensive in the field. Further lines of research are described by the authors. 相似文献
49.
Michael J Collins Stephanie C Voetz Nora Bretschneider 《Contact lens & anterior eye》2005,28(3):121-125
The removal of rigid contact lenses from the eye, using the eyelids, is a relatively simple procedure. However, there is a sequence of biomechanical events underlying this procedure which are not well understood. By using high-speed videokeratoscopy (50 Hz), we have shown that during the lid-pull procedure the cornea typically shows a significant increase in with-the-rule astigmatism by an average of 2.19 D (axial power). The average increase in steep K power was 1.22 D (S.D. +/-1.05 D) and the average decrease in flat K power was 0.97 D (S.D. +/-1.05 D). This change in corneal topography increases the edge lift of the lens at 12 and 6 O'clock locations of the lens, enhancing the removal process. When the subject blinks, as the lid margins reach the lens edge, the lens flexes and the eye retracts by an average of 0.66 mm (S.D. +/-0.27 mm). This retraction again enhances the act of lens removal. 相似文献
50.
F Rivera-Chavez LH Toledo-Pereyra DT Nora B Bachulis F Ilgenfritz RE Dean 《Canadian Metallurgical Quarterly》1998,45(3):440-445
OBJECTIVE: Increased intra-abdominal pressure (IAP) compromises cardiopulmonary function and visceral perfusion. Our goal was to characterize acute changes in these subsystems associated with operative abdominal decompression. PATIENT POPULATION: A series of 11 consecutive injured patients monitored with a pulmonary artery catheter and nasogastric tonometer in whom operative decompression was performed. Indications for decompression included oliguria or progressive acidosis despite aggressive resuscitation in the presence of elevated IAP (>25 mm Hg). MAIN OUTCOME MEASURES: Studied hemodynamic variables included pulmonary artery occlusion pressure (PAOP), right ventricular end-diastolic volume index (RVEDVI), and cardiac index (CI). Pulmonary variables included shunt fraction (Qs/Qt) and dynamic compliance (Cdyn). Visceral perfusion was assessed using hourly urine output 4 hours before and after decompression (UOP) and gastric intramucosal pH (pHi). Mean values before and after decompression were compared using the paired t test. Linear regression and Fisher's z transformation were used to evaluate the relationships between RVEDVI, PAOP, CI, and IAP. IAP was transduced via bladder pressures. Significance was defined as p < 0.05. Data are expressed as means+/-SD. RESULTS: IAP decreased with decompression (49+/-11 to 19+/-6.8 mm Hg; p < 0.0001). RVEDVI improved independent of CI and correlated better (p < 0.01) with CI (r =0.49, p=0.04) than PAOP did (r=-0.36, p=0.09). PAOP correlated significantly with IAP (r=0.45, p=0.04). Decompression resulted in significant improvements in Qs/Qt, Cdyn, UOP, and pHi. CONCLUSION: Abdominal decompression in patients with increased IAP improves preload, pulmonary function, and visceral perfusion. Elevated IAP has important effects on PAOP, which makes the PAOP an unreliable index of preload in these patients. 相似文献