全文获取类型
收费全文 | 1771篇 |
免费 | 69篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 15篇 |
综合类 | 1篇 |
化学工业 | 598篇 |
金属工艺 | 48篇 |
机械仪表 | 22篇 |
建筑科学 | 40篇 |
能源动力 | 164篇 |
轻工业 | 113篇 |
水利工程 | 10篇 |
石油天然气 | 8篇 |
无线电 | 116篇 |
一般工业技术 | 350篇 |
冶金工业 | 106篇 |
原子能技术 | 25篇 |
自动化技术 | 229篇 |
出版年
2024年 | 6篇 |
2023年 | 20篇 |
2022年 | 37篇 |
2021年 | 60篇 |
2020年 | 44篇 |
2019年 | 44篇 |
2018年 | 79篇 |
2017年 | 60篇 |
2016年 | 71篇 |
2015年 | 25篇 |
2014年 | 55篇 |
2013年 | 118篇 |
2012年 | 83篇 |
2011年 | 118篇 |
2010年 | 75篇 |
2009年 | 69篇 |
2008年 | 87篇 |
2007年 | 69篇 |
2006年 | 72篇 |
2005年 | 48篇 |
2004年 | 37篇 |
2003年 | 28篇 |
2002年 | 39篇 |
2001年 | 20篇 |
2000年 | 21篇 |
1999年 | 25篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 27篇 |
1994年 | 18篇 |
1993年 | 31篇 |
1992年 | 27篇 |
1991年 | 25篇 |
1990年 | 33篇 |
1989年 | 20篇 |
1988年 | 19篇 |
1987年 | 21篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 22篇 |
1980年 | 10篇 |
1979年 | 8篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1967年 | 2篇 |
排序方式: 共有1845条查询结果,搜索用时 15 毫秒
131.
Indu Bhushan Anil Kumar Gourav Modi Subika Jamwal 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(2):315-318
In the present investigation a Lipase producing strain, Bacillus subtilis (MTCC‐121) was grown on various media containing different sources of carbon, nitrogen and other nutrients. The best media found for the production of lipase was M2 media containing 0.4% peptone, 0.2% beef extract and 1% NaCl. Lipase produced from this culture was used for the kinetic resolution of racemic acetyl‐1‐phenyl ethanol and its derivatives, which are important as chiral auxiliaries and intermediates in the synthesis of natural products, pharmaceuticals and agrochemicals. The lipase resolved these substrates after 48 h with enantiomeric excess of 90–98% and conversion 40–48%. Copyright © 2010 Society of Chemical Industry 相似文献
132.
Anne Makena Dr. Sander S. van Berkel Dr. Clarisse Lejeune Dr. Raymond J. Owens Dr. Anil Verma Ramya Salimraj Dr. James Spencer Dr. Jürgen Brem Prof. Dr. Christopher J. Schofield 《ChemMedChem》2013,8(12):1923-1929
Serine‐ and metallo‐β‐lactamases present a threat to the clinical use of nearly all β‐lactam antibiotics, including penicillins, cephalosporins, and carbapenems. Efforts to develop metallo‐β‐lactamase (MBL) inhibitors require suitable screening platforms to allow the rapid determination of β‐lactamase activity and efficient inhibition. Unfortunately, the platforms currently available are not ideal for this purpose. Further progress in MBL inhibitor identification requires inexpensive and widely applicable assays. Herein the identification of an inexpensive and stable chromogenic substrate suitable for use in assays of clinically relevant MBLs is described. (6R,7R)‐3‐((4‐Nitrophenoxy)methyl)‐8‐oxo‐7‐(2‐phenylacetamido)‐5‐thia‐1‐azabicyclo[4.2.0]oct‐2‐ene‐2‐carboxylic acid 5,5‐dioxide (CLS405) was synthesised in a three‐step protocol. CLS405 was then characterised spectroscopically, and its stability and kinetic properties evaluated. With a Δλmax value of 100 nm between the parent and hydrolysis product, a higher analytical accuracy is possible with CLS405 than with commonly used chromogenic substrates. The use of CLS405 in assays was validated by MBL activity measurements and inhibitor screening that resulted in the identification of N‐hydroxythiazoles as new inhibitor scaffolds for MBLs. Further evaluation of the identified N‐hydroxythiazoles against a panel of clinically relevant MBLs showed that they possess inhibitory activities in the mid‐ to low‐micromolar range. The findings of this study provide both a useful tool compound for further inhibitor identification, and novel scaffolds for the design of improved MBL inhibitors with potential as antibiotics against resistant strains of bacteria. 相似文献
133.
The present paper deals with the synthesis of conducting ferrimagnetic polyaniline nanocomposite embedded with γ-Fe2O3 (9–12 nm) and titanium dioxide (70–90 nm) nanoparticles via a micro-emulsion polymerization. The microwave absorption properties of nanocomposite in 12.4–18 GHz (Ku-band) frequency range shows shielding effectiveness due to absorption (SEA) value of ?45 dB, which is much higher than polyaniline composite with iron oxide and polyaniline–TiO2 composites. The higher EMI shielding is mainly arising due to combined effect of γ-Fe2O3 and TiO2 that leads to more dielectric and magnetic losses which consequently contributed to higher values of shielding effectiveness. XRD analysis of the nanocomposite reveals the incorporation of nanoparticles in the conducting polymer matrix while the thermal gravimetric analysis (TGA) demonstrates that the nanocomposite is stable up to 250 °C. 相似文献
134.
Athabasca bitumen was characterized by dividing it into sixteen pseudo components. Using mean boiling point, molecular weight and specific gravity data, the critical properties of the pseudo components were estimated from available correlations. Two approaches for the prediction of bitumen surface tension were investigated. It was found that the surface tensions predicted by the principle of corresponding states and the Rice-Teja correlations were in general agreement with the published experimental data. In addition, these models successfully predicted the effect of temperature on surface tension at temperatures greater than about 60°C. 相似文献
135.
Purnima Dhall Anil Kumar Abha Joshi Tushya Kumar Saxsena Angamuthu Manoharan Santosh Dayal Makhijani Rita Kumar 《Sensors and actuators. B, Chemical》2008,133(2):478-483
An amperometric biosensor for determination of biochemical oxygen demand in wastewater has been developed to overcome the time consuming monitoring procedures. The performance and stability of the immobilized membrane have been investigated at 37 °C and pH 6.8. Immobilized microbial membranes maintain their stability and activity after intermittent use for 400 cycles when stored at 4 °C in sodium phosphate buffer pH 6.8. The response time of the BOD sensor was only 90 min, being independent of the concentration, and the lower detection limit was 1 mg/l. The obtained BOD values showed correlation with that of the conventional method for BOD determination (BOD5) with a deviation of ±10%. Moreover, the sensor exhibits good repeatability (3.39–4.45%) and reproducibility (1.85–2.25%). Software was added to upgrade this sensor and to make it a promising candidate for online monitoring. 相似文献
136.
Anil G. Khadakkar K. Ravi Sankar P. Rathinam R. Narayanan S. P. Rao J. K. Popli 《Strain》1997,33(2):57-60
This paper describes an experimental investigation carried out involving instrumentation, measurement and monitoring of stresses in a large diameter gas pipeline during its lowering operations. It also highlights the ingenious techniques developed and adopted to overcome the difficulties pertaining to long leadwires, measurement of existing strains on the curved surface of a pipeline and protection of strain gauge installations. These novel methods were used to ensure smooth and proper functioning of strain gauge instrumentation even under the severe field conditions at site for more than two weeks, till the lowering operations and pipeline monitoring was successfully completed. 相似文献
137.
Anil Kumar Mandeep Kaur Rajeev Kumar Pinaki Ranjan Sengupta Vasantha Raman Gopal Bhatia Kedar Nath Sood 《Journal of Materials Science》2010,45(5):1393-1400
Carbon–copper composites with varying copper to carbon ratio of 0.66–1.5 (by weight) were developed from coal-tar-pitch-derived
green coke (as such or modified with natural graphite) as carbon source and electrolytic grade copper powder at different
heat treatment temperatures (HTTs) of 1000–1400 °C. The physical, mechanical, and electrical properties differ depending upon
the HTT and also on copper to carbon ratio (Cu/C). The composites prepared at HTT of 1100 °C having Cu/C ratio of 0.66 and
0.9 exhibited a high bending strength of 150 and 140 MPa, bulk density of 2.63 and 2.81 gm/cm3, electrical resistivity of 1.6 and 0.96 m Ω cm and shore hardness of 88 and 84, respectively, in spite of well-known inadequate
wettability between copper and carbon. Increasing the temperature from 1100 °C for processing of the composites deteriorated
the properties mainly due to the loss of copper through melting above 1100 °C as revealed by X-ray, scanning electron microscopy,
thermal analysis and EDAX studies. 相似文献
138.
Anil Kumar 《Atomic Data and Nuclear Data Tables》2010,96(6):567-585
The intensity ratios, ILk/ILα1 (k = l, η, α2, β1, β2,15, β3, β4, β5,7, β6, β9,10, γ1,5, γ6,8, γ2,3, γ4), have been evaluated for elements with atomic number 36 ? Z ? 92 at incident photon energies ranging EL1 < Einc ? 200 keV using currently considered to be more reliable theoretical data sets of different physical parameters, namely, Li (i = 1-3) subshell photoionization cross sections based on the relativistic Hartree-Fock-Slater model, the X-ray emission rates based on the Dirac-Fock model, and the fluorescence and Coster-Kronig yields based on the Dirac-Hartree-Slater model. At incident photon energies above the K-shell ionization threshold, the contribution to the production of different L X-ray lines due to the additional Li (i = 1-3) subshell vacancies created following decay of the primary K-shell vacancies have also been included in the present calculations. The important features pertaining to dependence of the tabulated intensity ratios on the incident photon energy and atomic number have been discussed. 相似文献
139.
Anil Maheshwari 《Information Systems Management》1999,16(2):85-88
Securing databases requires IS managers to have the utmost attention paid to all kinds of breaches of security, within and outside the organizations. Dynamic page generation and cookies are two of the newer issues that cause IS managers to be forever open to new ways of solving security problems. 相似文献
140.
Thermodynamic and Kinetic Effects of Oxygen Removal on the Thermal Conductivity of Aluminum Nitride 总被引:12,自引:0,他引:12
Anil V. Virkar T. Barrett Jackson Raymond A. Cutler 《Journal of the American Ceramic Society》1989,72(11):2031-2042
High thermal conductivity, low dielectric constant, high electrical resistivity, low density, and a thermal expansion coefficient that matches well with that of silicon are the principal attributes of AIN that have attracted much attention over the past decade. It is also now well established that oxygen as an impurity lowers the thermal conductivity of AIN. Processing techniques have been developed which not only facilitate pressureless densification of AIN but also enhance its thermal conductivity. The present work explores the thermodynamics and the kinetics of oxygen removal and the resultant enhancement of thermal conductivity. Polycrystalline AIN ceramics were fabricated with Y2O3, Dy2O3, Yb2O3, CaO, BaO, or MgO as additives. Samples were sinter/annealed at 1850°C for up to 1000 min. The AIN grain size of sintered samples ranged between 2 and 9 μm. The samples typically contained two or three phases with the predominant phase being AIN. Secondary phases in Y2O3-doped AIN consisted of yttrium aluminates which were along three grain junctions and along grain facets. The presence of Y3Al5O12, YAIO3, and Y4Al2O9, as well as Y2O3, depending upon the Y2O3/Al2O3 ratio, was revealed by X-ray diffraction. Thermal conductivity increased with the amount of additive and annealing time. Thermal conductivity also depended on the type of additive. Samples with thermal conductivity up to 200 W/(m · K) were fabricated. The variation in thermal conductivity with the type and the amount of the additive is explained on the basis of the thermodynamics of oxygen removal. In particular, the higher thermal conductivity of CaO-doped, in comparison with MgO-doped, samples is rationalized on the basis that the free energy of formation, ΔG°, of CaAl2O4 is less than that of MgAl2O4. It is proposed that the higher the |ΔG°|, with ΔG° < 0, the higher is the resultant thermal conductivity. An increase in the thermal conductivity with annealing time is attributed to the kinetics of oxygen removal from AIN grains. 相似文献