全文获取类型
收费全文 | 951篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 92篇 |
金属工艺 | 1篇 |
机械仪表 | 4篇 |
建筑科学 | 18篇 |
能源动力 | 21篇 |
轻工业 | 36篇 |
水利工程 | 6篇 |
无线电 | 27篇 |
一般工业技术 | 49篇 |
冶金工业 | 673篇 |
原子能技术 | 4篇 |
自动化技术 | 25篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 18篇 |
2012年 | 17篇 |
2011年 | 23篇 |
2010年 | 16篇 |
2009年 | 12篇 |
2008年 | 18篇 |
2007年 | 17篇 |
2006年 | 13篇 |
2005年 | 8篇 |
2004年 | 7篇 |
2003年 | 12篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 23篇 |
1998年 | 225篇 |
1997年 | 119篇 |
1996年 | 72篇 |
1995年 | 52篇 |
1994年 | 34篇 |
1993年 | 51篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1978年 | 6篇 |
1977年 | 17篇 |
1976年 | 42篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有959条查询结果,搜索用时 0 毫秒
21.
M. C. S. Perera 《应用聚合物科学杂志》1987,34(7):2591-2600
Epoxidation has been applied to modify the surface of natural rubber laces. When very thin laces of fractionated bleached rubber are used, about 6% of the double bonds could be modified. Using 1H nuclear magnetic resonance (NMR) and infrared (IR) analysis the best condition for the reaction was worked out. Both 13C NMR and differential scanning calorimetry (DSC) results indicate that the 6% epoxide groups are placed in a predominantly block manner. Modification in yellow fraction rubber however gives lower epoxy contents. Increase in glass transition tempreature by epoxidation results in more damping and better abrasion resistance. The resultant polymer acts very similar to a 90/10 natural rubber/50% epoxidized natural rubber (NR/ENR-50) blend. 相似文献
22.
S. Perera 《时间序列分析杂志》2004,25(5):723-732
Abstract. Maximum quasi-likelihood estimation is investigated for the NEAR(2) model, an autoregressive time series model with marginal exponential distributions. In certain regions of the parameter space, simulations indicate that maximum quasi-likelihood estimators perform better than two-stage conditional least squares estimators in terms of the per cent of estimates falling in the parameter space. The problem of out-of-range estimates is shown to be caused by the lack of information in the data rather than the characteristics of the method of estimation. 相似文献
23.
Nitrogen-containing aluminium titanate 总被引:1,自引:0,他引:1
In the Ti-Al-O-N system a phase isostructural to aluminium titanate but with expanded unit cell dimensions was observed. It was stable between 1400 and 1700 °C and has unit cell dimensions of a=0.3719 nm, b=0.9703 nm and c=0.9869 nm with a composition of Ti
1.00
4+
Al
0.54
3+
Ti
1.46
3+
N
0.28
3–
O
4.58
2–
0.14 Several samples were prepared by reaction sintering mixtures of TiN, Al2O3 and AlN powders at 1400 to 1470 °C for 4 h in a nitrogen atmosphere to maximize this phase. One specific advantage of the nitrogen-containing aluminium titanate over aluminium titanate is that the former is unchanged at 1150 °C in a nitrogen atmosphere whereas the latter decomposes. In the Al2O3-TiO2 oxide system Al2TiO5 solid solution extends to approximately Al0.75Ti2.25O5 at 1470 °C under the mildly reducing conditions of a graphite furnace. The unit cell volume increases linearly with the increasing replacement of Al3+ by Ti3+. 相似文献
24.
Davide Ciceri Lachlan R. Mason Dalton J. E. Harvie Jilska M. Perera Geoffrey W. Stevens 《Microfluidics and nanofluidics》2013,14(1-2):213-224
The use of a microfluidic device in determining the extraction kinetics of CoII ions by di-(2-ethylhexyl) phosphoric acid (DEHPA) was demonstrated. Experimental data obtained using a Y-Y-shaped microchannel were modelled using a finite volume method. The contributions of diffusion and reaction transport resistances to the overall rate of mass transfer were obtained. A diffusion-controlled transfer assumption could not account for the experimental data, confirming that transport occurs under a mixed reaction–diffusion resistance regime. The reaction rate constant was determined to be $(2.4 \pm 0.6) \times 10^{-10}$ m/s, in good agreement with corresponding Lewis cell measurements from the literature. 相似文献
25.
Dharani Perera R. T. Jim Eales Kathy Blashki 《Universal Access in the Information Society》2009,8(2):77-88
For people with upper limb disabilities visual art is an important activity that allows for expression of individuality and
independence. They show remarkable endurance, patience and determination to adapt their remaining capabilities to create visual
art. There are significant advantages of digital technologies in assisting artists with upper limb disabilities. Paralinguistic
voice recognition technologies have proven to be a particularly promising mode of interaction. Despite these benefits, technological
support for people with upper limb disabilities to create visual art is scarce. This paper reports on a number of case studies
of several artists with upper limb disabilities. These case studies illustrate the struggles they face to be creative and
also show the significant advantages of digital technologies in assisting such artists. An investigation into people’s ability
to use the volume of their voice to control cursor movement to create drawings on the screen is also reported. With motivation,
training and practise, use of volume to control drawing tasks shows great promise. It is believed that paralinguistic voice
has wider implications beyond assisting artists with upper limb disabilities, such as: an alternative mode of interaction
for disabled people to perform tasks other than creating visual art, alternative mode of interaction for hands busy environments
and as a voice training system for people with speech impairments. 相似文献
26.
The prevalence of 18 selected bacterial species was assessed by means of "checkerboard" DNA-DNA hybridisation in a group of 12 Saudi-Arabian adolescents with Papillon-Lefèvre syndrome. A total of 36 tooth sites were investigated. The patients exhibited severe periodontal disease with deep pockets. All 12 patients harboured the putative bacterial pathogens P. intermedia, F. nucleatum, P. micros and S. intermedius while T. denticola, B. forsythus, P. nigrescens, E. corrodens, S. noxia and C. rectus were recovered from 11 patients. P. gingivalis was recovered from 9 patients and 18 sites while corresponding figures for A. actinomycetemcomitans were 8 and 19, respectively. A number of the investigated species (B. forsythus, T. denticola, P. intermedia, C rectus) reached high levels (> or =10(6) cells) in more than 1/2 of the patients. On the other hand, bacteria such as A. actinomycetemcomitans and P. gingivalis were infrequently encountered at high levels in these subgingival samples. In conclusion, the analysis failed to demonstrate a PLS-specific profile of the subgingival infection, since the bacterial composition of the sampled sites closely resembled that characterising deep pockets in adult periodontitis patients. 相似文献
27.
OBJECTIVES: To evaluate the postoperative analgesic efficacy, side effects and acceptance by patients and nurses of intravenous "patient-controlled analgesia" (PCA) with morphine, metamizole and buprenorphine. MATERIAL AND METHODS: In this randomized double blind prospective study of 150 patients in three groups receiving morphine (group A), metamizole (group B) or buprenorphine (group C), the patients had undergone low abdominal surgery with the same anesthetic protocol. Pain was recorded during the first 48 h after surgery on an orally-communicated scale of none or slight = 0, moderate = 1 and severe = 2. Upon the first report of moderate pain, patients were administered an intravenous bolus containing 5 mg morphine, 1 g metamizole or 0.15 mg buprenorphine. A perfusion pump was then connected and set with one bolus of 1.2 mg morphine, one of 333 mg metamizole or one of 0.04 buprenorphine. The maximum dose allowed in 24 h was 40 mg morphine, 8 g metamizole or 1.2 mg buprenorphine. The minimum interval between doses was 30 min for all three groups. Side effects reported were respiratory depression, sedation, nausea, vomiting, pruritus, perspiration and pain upon administration. Patients and nurses were asked to evaluate the system when the pump was disconnected and the results were then analyzed statistically. RESULTS: The analgesic effect was satisfactory in all three groups, with no significant differences among them. The percentages of patients reaching the maximum allowed dose on the first day were 2% with morphine, 18% (p < 0.05) with metamizole and 8% with buprenorphine. No respiratory depression was observed. Sedation was greater with morphine and buprenorphine than with metamizole (p = 0.0001). Pruritus was also greater with morphine and buprenorphine than with metamizole (p = 0.02) and pain upon infusion was greater with metamizole (p = 0.0002). CONCLUSIONS: Intravenous postoperative PCA was effective with all three drugs studied. Patient and nurse acceptance was good and side effects were few in the three groups. The lower rate of side effects for metamizole makes it the drug of choice. 相似文献
28.
In a pot culture experiment, the effect of gypsum (50% of soil requirement), pyrites (equivalent to gypsum), farmyard manure (0.5 g per 100g soil) and Zn (10mg Zn kg–1 soil) on Zn equilibria in Ghabdan and Langrian series of sodic soils was studied. The equilibrium soil solutions collected anaerobically after 1, 14, 28, 42, 56, 70 and 84 days of submergence were analysed for pH, EC, HCO3 and Zn. Submergence markedly decreased soil solution pH and Zn up to 14 days and thereafter, the former slightly increased and the latter continued to decrease. Addition of amendments decreased soil solution pH in the order gypsum, pyrites and farmyard manure (FYM) and increased Zn concentration in the order FYM, gypsum and pyrites. The values of Zn potential (pZn + 2pOH) were within the range of pKsp for Zn(OH)2-Zn2+ (aq) from 16 to 84 days of submergence in Ghabdan soil and from 9 to 42 days of submergence in Langrian soil, where later it shifted to ZnCO3-Zn2+ (aq) system. Addition of FYM, pyrites and gypsum shortened the period of predominant existence of Zn(OH)2-Zn2+ (aq) system to 40, 30 and 12 days in Ghabdan soil and 30, 20 and 6 days in Langrian soil respectively. After these periods the system was saturated with respect to ZnCO3-Zn2+ (aq) except gypsum treatment where Zn-soil (unknown solid phases) -Zn2+ (aq) system controlled the solubility of Zn after 38 and 28 days of submergence of Ghabdan and Langrian soil respectively. 相似文献
29.
When buildings are subjected to earthquakes, it is imperative to dissipate some of the input energy through pre-determined and well designed mechanisms. This study investigates the influence of mechanical control on structural systems through the application of strategically located component elements with reliable damping and stiffness properties that can modulate the response. The effects of installing such damping elements at two particular locations have been investigated. These positions are between the shear walls near the coupling beams and within cut out sections of the wall elements in multi-storey structures. Finite element time history analysis is used in the study and results indicate that the proposed procedure is able to achieve reasonable improvements in seismic response. 相似文献
30.
Z Shao IR Mellor MJ Brierley J Harris PN Usherwood 《Canadian Metallurgical Quarterly》1998,286(3):1269-1276
Nicotinic acetylcholine receptors (nAChR) of the TE671 cell line were investigated using whole-cell and membrane patch recording techniques. At negative holding potentials (VH), pulses of acetylcholine (ACh) elicited whole-cell inward currents that rapidly desensitized. The EC50 value for ACh at VH = -60 mV was 7.8 microM. The ACh-induced current reversed at approximately 0 mV. Desensitization of nAChR by ACh was biphasic and reversible within approximately 20 sec. Spermine (1-100 microM) potentiated responses to ACh (10 microM - 1 mM) by reducing the rate of onset of desensitization; potentiation was inhibited by arcaine (10-100 microM). Spermine (1 mM) noncompetitively antagonized the AChinduced current. Antagonism by 1 to 5 mM spermine was voltage-dependent, increasing with negative VH. In 100 microM arcaine, this antagonism was shown to contain a voltage-independent component. Spermine (10 mM) increased the EC50 values for ACh, suggesting that at this concentration the polyamine is also a competitive antagonist. Single channel openings elicited during application of ACh to outside-out patches had a conductance of 47 pS at VH = -60 mV. At 10 and 100 microM, spermine increased channel open probability (po), but at 1 mM spermine, po was not significantly different from controls. The single channel conductance for ACh was unaffected by 10 and 100 microM spermine, but was decreased by 1 mM spermine. Spermine promoted the occurrence of approximately 27 pS openings. It is proposed that spermine acts at an excitatory modulatory site similar to that present on N-methyl-D-aspartate receptors and at least three inhibitory sites on nAChR of TE671 cells. 相似文献