全文获取类型
收费全文 | 518332篇 |
免费 | 8922篇 |
国内免费 | 1742篇 |
专业分类
电工技术 | 9239篇 |
综合类 | 881篇 |
化学工业 | 80361篇 |
金属工艺 | 19422篇 |
机械仪表 | 14694篇 |
建筑科学 | 12646篇 |
矿业工程 | 2713篇 |
能源动力 | 12531篇 |
轻工业 | 47130篇 |
水利工程 | 5199篇 |
石油天然气 | 9531篇 |
武器工业 | 59篇 |
无线电 | 58595篇 |
一般工业技术 | 97592篇 |
冶金工业 | 104041篇 |
原子能技术 | 10610篇 |
自动化技术 | 43752篇 |
出版年
2021年 | 4865篇 |
2020年 | 3618篇 |
2019年 | 4487篇 |
2018年 | 7360篇 |
2017年 | 7215篇 |
2016年 | 7781篇 |
2015年 | 5395篇 |
2014年 | 8556篇 |
2013年 | 23104篇 |
2012年 | 13774篇 |
2011年 | 17918篇 |
2010年 | 14548篇 |
2009年 | 16359篇 |
2008年 | 16714篇 |
2007年 | 16407篇 |
2006年 | 14517篇 |
2005年 | 13461篇 |
2004年 | 12888篇 |
2003年 | 12693篇 |
2002年 | 12737篇 |
2001年 | 12533篇 |
2000年 | 11420篇 |
1999年 | 12011篇 |
1998年 | 32530篇 |
1997年 | 22669篇 |
1996年 | 17301篇 |
1995年 | 12673篇 |
1994年 | 11127篇 |
1993年 | 11178篇 |
1992年 | 7737篇 |
1991年 | 7584篇 |
1990年 | 7340篇 |
1989年 | 7142篇 |
1988年 | 6864篇 |
1987年 | 5746篇 |
1986年 | 5803篇 |
1985年 | 6651篇 |
1984年 | 6127篇 |
1983年 | 5538篇 |
1982年 | 5251篇 |
1981年 | 5522篇 |
1980年 | 5183篇 |
1979年 | 4877篇 |
1978年 | 4920篇 |
1977年 | 6077篇 |
1976年 | 8288篇 |
1975年 | 4428篇 |
1974年 | 4226篇 |
1973年 | 4195篇 |
1972年 | 3618篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
921.
ABSTRACT: This study investigated the effects of 10% (w/v) salt, trisodium phosphate (TSP), sodium tripolyphosphate (STPP), and tetrapotassium pyrophosphate (TKPP) washes on removal of attached Salmonella typhimurium from sterile chicken breast patties, as well as on their injury and survival in a refrigerator for 16 d, in a –20 °C freezer for 10 mo, and after 3 freeze-thaw cycles. S. typhimurium were grown on chicken patties at 20 °C for 20 h, washed, and enumerated by plating on selective and nonselective media. Salt and phosphates washing significantly lowered the survival populations of attached S. typhimurium on patties, but did not cause any significant sublethal injury of attached S. typhimurium , irrespective of storage treatments. The TSP washes showed superior effects of removing and inactivating S. typhimurium compared to other washing treatments. 相似文献
922.
ABSTRACT: :
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. 相似文献
Soybeans ( Glycine max ) were soaked and ground to obtain soymilk. The soymilk was cooked in an open tank and held at 85 to 90 deg;C. Yuba films were picked up in 20 min intervals and dried for 20 min. Yuba films were soaked in chicken-flavor solutions (25% and 35%), and baking soda (BS) solutions (0%, 1%, 2%, and 3% BS), and cooked at 100 °C for 30 min, 60 min, and 90 min. TIA decreased (p < 0.05) with the increase of heating time and BS concentration. In vitro protein digestibility (IVPD) decreased with heating time and BS concentration (p < 0.05). Sensory characteristics were affected by flavor concentration. By using 0% BS, 25% of the chicken flavor concentration, and a short heating time method, meat-like products with low TIA, high IVPD, and good sensory characteristics were obtained. 相似文献
923.
A method for fabricating single crystal blades that combines the techniques of seed crystals and selection is suggested. The method realizes the advantages of both techniques, i.e., the high structural perfection and the possibility of fabricating single crystals with specified spatial orientation. Metallographic and x-ray diffraction analyses are used to study the processes of nucleation of the single crystal structure of blade castings fabricated from high-temperature nickel alloys by the method of selection and seed crystals. A commercial process for fabricating cast single crystal turbine blades by the new method is suggested. 相似文献
924.
Environmental contaminants such as trace elements may be present in all foods. Foods, raw materials and ingredients for food production are to an increasing extent traded across borders. Hence, there is a need for international legislation on trace elements as contaminants in food. In 1961, the FAO and WHO established the Codex Alimentarius to elaborate international food legislation. Contaminants in food are handled by the Codex Committee for Food Additives and Contaminants (CCFAC). The Codex Alimentarius system for developing legislation concerning trace elements as contaminants in food is based upon the Codex General Standard for Contaminants and Toxins in Food (GSCTF). By October 2001, the principles for setting maximum limits (MLs) for contaminants in food are agreed, and work is in progress on MLs for trace elements such as lead and cadmium in the various food categories. The status for the proposals is presented and discussed. The EU Regulation 466/2001 of 8 March 2001 sets MLs for lead and cadmium in various foods. This regulation will apply from 5 April 2002. The EU regulation is more detailed but similar to the Codex draft standards for lead and cadmium in food. In future, legislators and administrators in the Codex and EU and analytical chemists will discuss how to use more and better analytical data as risk-management tools to protect public health. Trace elements' speciation is an important aspect of this discussion. 相似文献
925.
An investigation into the effects of pressure (helium gas) on the isothermal fluid behavior includes: (1) the effect of pressure on the rate of melting and coking as evidenced by the rate constants k(melt) and k(coke); (2) the effect of pressure on the energies of activation of melting and coking; (3) the effects of pressure on the characteristic times; (4) the effects of pressure on the maximum isothermal fluidity. Results from the effects of pressure on k(melt) revealed that it was generally the high total sulfur, low nitrogen, low reactives/mineral matter ratio, medium rank coals which show the greatest increase in k(melt), whereas the highest rank coals show the least decrease in k(coke). The energies of activation of melting and coking were not significantly affected by pressure. The investigation also reveals increases or decreases in the respective times of softening, maximum fluidity, resolidification and total time of fluid behavior under isothermal pressurized conditions. There appears the possibility that these shifts may be rank dependent. Additionally, the lower rank coals show the largest relative increase in their fluidities when subjected to pressure. Empirical relationships were derived in order to quantitatively predict the maximum isothermal fluidity for most (fluid) coals at a given pressure. 相似文献
926.
A simple apparatus for elongational test of molten polymers is presented. Its realiability is demonstrated by means of stress growth in constant stretching rate experiments and relaxation test on a low density polyethylene sample. 相似文献
927.
The emergence of neural networks as a significant subdiscipline with corresponding attempts at application to engineering problems is traced back to the 1960s, when Frank Rosenblatt, a Cornell University psychologist, showed by mathematical analysis, digital computer simulation, and experiments with special-purpose parallel analog systems that neural networks with variable-weight connections could be trained to classify spatial patterns into prespecified categories. In his attempts to provide biologically plausible explanations of the function of the central nervous system, he investigated relatively simple networks that were amenable to analysis and more complex networks whose behavior could be predicted only in terms of gross characteristics. He assembled a sizable group involving theoreticians, experimentalists, technologists, and, later, biologists. His work caught the imagination of the press and led to the wave of febrile activity that subsided at the end of that decade. 相似文献
928.
929.
The maintenance of the MACRO (a Monopoles, Astrophysics and Cosmic Ray Observatory), a large-area detector that will be used to search for rare constituents or phenomena in cosmic radiation penetrating deep underground, is addressed. A real-time expert system for diagnosing detector and data acquisition system anomalies, which is based on the NEXPERT commercial tool, is described. It performs online diagnosis and, if an abnormal condition is identified, takes the appropriate action to reduce the unavailability of the apparatus. The data acquisition system is CAMAC-based, and the sensor modules, which gather the significant values for diagnosis, are implemented in the VME crate 相似文献
930.
Statistics on the backscatter coefficient σ0 from the Ku -band Seasat-A Satellite Scatterometer (SASS) collected over the world's land surfaces are presented. This spaceborne scatterometer provided data on σ0 between latitude 80° S and 80° N at incidence angles up to 70°. The global statistics of vertical (V ) and horizontal (H ) polarization backscatter coefficients for 10° bands in latitude are presented for incidence angles between 20° and 70° and compared with the Skylab and ground spectrometer results. Global images of the time-averaged V polarization σ0 at a 45° incidence angle and its dependence on the incidence angle are presented and compared to a generalized map of the terrain type. Global images of the differences between the V an H polarization backscatter coefficients are presented and discussed. The most inhomogeneous region, which contains the deserts of North Africa and the Arabian Peninsula, is studied in greater detail and compared with the terrain type 相似文献