全文获取类型
收费全文 | 7010篇 |
免费 | 200篇 |
国内免费 | 30篇 |
学科分类
工业技术 | 7240篇 |
出版年
2023年 | 69篇 |
2022年 | 151篇 |
2021年 | 177篇 |
2020年 | 159篇 |
2019年 | 148篇 |
2018年 | 233篇 |
2017年 | 193篇 |
2016年 | 197篇 |
2015年 | 109篇 |
2014年 | 211篇 |
2013年 | 416篇 |
2012年 | 235篇 |
2011年 | 313篇 |
2010年 | 245篇 |
2009年 | 280篇 |
2008年 | 249篇 |
2007年 | 199篇 |
2006年 | 208篇 |
2005年 | 157篇 |
2004年 | 131篇 |
2003年 | 130篇 |
2002年 | 129篇 |
2001年 | 127篇 |
2000年 | 130篇 |
1999年 | 112篇 |
1998年 | 264篇 |
1997年 | 182篇 |
1996年 | 132篇 |
1995年 | 130篇 |
1994年 | 105篇 |
1993年 | 137篇 |
1992年 | 108篇 |
1991年 | 97篇 |
1990年 | 84篇 |
1989年 | 75篇 |
1988年 | 72篇 |
1987年 | 75篇 |
1986年 | 88篇 |
1985年 | 106篇 |
1984年 | 99篇 |
1983年 | 96篇 |
1982年 | 79篇 |
1981年 | 63篇 |
1980年 | 50篇 |
1979年 | 47篇 |
1978年 | 49篇 |
1977年 | 62篇 |
1976年 | 82篇 |
1975年 | 43篇 |
1973年 | 42篇 |
排序方式: 共有7240条查询结果,搜索用时 15 毫秒
991.
Ajaya K. Gupta Bijan Mohraz 《International journal for numerical methods in engineering》1972,5(1):83-89
A method of formulating and computing numerically integrated stiffness matrices is presented. Through a better organization of the formulation which is easily achieved by the use of index notation, the computations for integrating and evaluating the element stiffness matrix are substantially reduced. For cases in which the terms of the material property tensor are not functions of position co-ordinates (elastic isotropic and anisotropic materials), a further reduction in computation is achieved by multiplying the material property-tensor after the numerical integration has been carried out. 相似文献
992.
993.
From the seeds of Solanum ferox L., a yellow coloured oil has been obtained in 2.7% yield. The fatty acid composition of this oil has been determined and found to be palmitic 12.15%, stearic 9.96%, oleic 39.83% and linoleic acid 38.06%. 相似文献
994.
This paper proposes a development of n-on-p structures for realizing very long wavelength infrared (VLWIR) detector arrays
on mercury cadmium telluride (HgCdTe) epitaxial layers grown on Si substrates. It is shown from a comparative study of zero-bias
resistance-area product (R0A) of diodes in n-on-p and p-on-n configurations that the n-on-p structure has promising potential to control contribution
of dislocations, without actually reducing dislocation density below the current level (mid-106 cm−2) of HgCdTe/Si material technology. The resulting gain will be in terms of both higher numerical magnitudes of R0A and its reduced scatter. 相似文献
995.
In this study, varying weight percentages of multiwalled carbon nanotubes were successfully incorporated into 95.8Sn-3.5Ag-0.7Cu
solder to synthesize novel lead-free composite solders. The composite solders were synthesized using a powder metallurgy route
consisting of blending, compaction, sintering, and extrusion. The extruded materials were then characterized for their physical,
thermal, and mechanical properties. With the addition of increasing weight percentage of carbon nanotubes, the composite solders
experienced a corresponding decrease in density values and an improvement in wetting properties. The melting temperatures
of the composite solders were found to be unchanged with additions of carbon nanotubes. However, improvements in the mechanical
properties, in terms of microhardness and tensile properties, were observed with increasing weight percentages of carbon nanotubes. 相似文献
996.
Jambur H. Jagannath Chindalaga Nanjappa Dilipkumar Das Gupta & Amarinder S. Bawa 《International Journal of Food Science & Technology》2006,41(5):498-506
An edible coating was formed by blending turmeric (Curcuma longa) and casein in equal proportions at 95 °C for 12 h. Small quantities of polyvinyl alcohol and propylene glycol were added to encourage film formation and plasticizing respectively. The blend was removed from the reaction vessel and homogenized using Tween‐80 as emulsifier. The homogenized blend was sampled at 2‐h intervals for stability by means of the ‘keeping property’ and ‘accelerated stability’ tests. Stability was also determined by differential scanning calorimetry in which a singlet endotherm indicated molecular mixing (miscibility window) of the components. All three tests indicated that the emulsion was stable after 12 h of blending. Colour, carotenoid content, texture retention and antimicrobial properties remained satisfactory for 10 days in the stable emulsion‐coated carrot whereas the control spoiled after 3 days. Thus turmeric and casein based‐emulsion coating could extend the shelf‐life of carrots by 7 days. 相似文献
997.
Dichloromethane extracts of culture broth from three strains of the entomopathogenic fungusHirsutella thompsonii var.synnematosa were toxic to two species of tephritid fruit fly and inhibited conidial germination in vitro in several other entomopathogenic fungi includingBeauveria bassiana, Tolypocladium spp., andMetarhizium anisopliae. A major metabolite, toxic to apple maggot,Rhagoletis pomonella, and inhibitory to conidial germination inB. bassiana, was isolated and identified as the antibiotic (+)-phomalactone, 6-(1-propenyl)-5,-6-dihydro-5-hydroxypyran-2-one. This is the first biologically active compound of low molecular weight isolated from the genusHirsutella.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA. 相似文献
998.
Adjuvants--a balance between toxicity and adjuvanticity 总被引:1,自引:0,他引:1
RK Gupta EH Relyveld EB Lindblad B Bizzini S Ben-Efraim CK Gupta 《Canadian Metallurgical Quarterly》1993,11(3):293-306
Adjuvants have been used to augment the immune response in experimental immunology as well as in practical vaccination for more than 60 years. The chemical nature of adjuvants, their mode of action and the profile of their side effects are highly variable. Some of the side effects can be ascribed to an unintentional stimulation of different mechanisms of the immune system whereas others may reflect general adverse pharmacological reactions. The most common adjuvants for human use today are still aluminium hydroxide, aluminium phosphate and calcium phosphate although oil emulsions, products from bacteria and their synthetic derivatives as well as liposomes have also been tested or used in humans. In recent years monophosphoryl lipid A, ISCOMs with Quil-A and Syntex adjuvant formulation (SAF) containing the threonyl derivative of muramyl dipeptide have been under consideration for use as adjuvants in humans. At present the choice of adjuvants for human vaccination reflects a compromise between a requirement for adjuvanticity and an acceptable low level of side effects. 相似文献
999.
Advances in dehydration techniques and development of novel drying methods have in recentyears enabled the preparation of a wide range of dehydrated products and convenience foods from fruits and vegetables meeting the quality, stability and functional requirements coupled with economy. This has been made possible by the sustained experimental studies over the years to understand the theoretical and fundamental aspects of the process and optimisation of the techniques to achieve a favourable combination of cost and quality. This paper reviews and highlights the developments in the dehydration of fruits and vegetables and their products during the last decade covering the oretical aspects and practical applications with major emphasis on techniques that have received the maximum attention. 相似文献
1000.
The elitist nondominated sorting genetic algorithm (NSGA‐II) and multiobjective simulated annealing (MOSA) with the robust fixed‐length jumping gene adaptation (aJG) are used to solve three computationally intensive multiobjective optimization problems for an industrial semi batch nylon‐6 reactor. In Problems 1 and 2, the batch time and the final concentration of the undesirable side‐product (cyclic dimer) are minimized while maintaining desired values of the degree of polymerization of the product and the monomer conversion (monomer conversion is maximized as a third objective in Problem 3). The histories of two decision variables, pressure [or vapor release rate] and jacket fluid temperature, are used to obtain the Pareto optimal fronts. The study predicts considerable improvement over earlier results when (i) a single‐stage steam jet ejector is used to create subatmospheric pressures in the reactor, (ii) when the jacket fluid temperature is taken as a function of time, and (iii) when some amino caproic acid (from the depolymerization of scrap nylon‐6) is added to the feed. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献