全文获取类型
收费全文 | 1712131篇 |
免费 | 25628篇 |
国内免费 | 7225篇 |
专业分类
电工技术 | 35798篇 |
综合类 | 6671篇 |
化学工业 | 283013篇 |
金属工艺 | 67984篇 |
机械仪表 | 50062篇 |
建筑科学 | 50594篇 |
矿业工程 | 12088篇 |
能源动力 | 50860篇 |
轻工业 | 136008篇 |
水利工程 | 17643篇 |
石油天然气 | 38593篇 |
武器工业 | 157篇 |
无线电 | 203710篇 |
一般工业技术 | 319397篇 |
冶金工业 | 256467篇 |
原子能技术 | 34907篇 |
自动化技术 | 181032篇 |
出版年
2021年 | 15957篇 |
2020年 | 12234篇 |
2019年 | 15034篇 |
2018年 | 20685篇 |
2017年 | 20570篇 |
2016年 | 24177篇 |
2015年 | 18103篇 |
2014年 | 29272篇 |
2013年 | 89022篇 |
2012年 | 41464篇 |
2011年 | 58366篇 |
2010年 | 48282篇 |
2009年 | 55474篇 |
2008年 | 52901篇 |
2007年 | 51526篇 |
2006年 | 49259篇 |
2005年 | 45469篇 |
2004年 | 46470篇 |
2003年 | 45932篇 |
2002年 | 44108篇 |
2001年 | 41366篇 |
2000年 | 39128篇 |
1999年 | 39763篇 |
1998年 | 73535篇 |
1997年 | 56666篇 |
1996年 | 46802篇 |
1995年 | 37595篇 |
1994年 | 34401篇 |
1993年 | 34068篇 |
1992年 | 27870篇 |
1991年 | 25334篇 |
1990年 | 25482篇 |
1989年 | 24613篇 |
1988年 | 23181篇 |
1987年 | 21268篇 |
1986年 | 20748篇 |
1985年 | 24118篇 |
1984年 | 23433篇 |
1983年 | 21306篇 |
1982年 | 19984篇 |
1981年 | 20151篇 |
1980年 | 18821篇 |
1979年 | 19186篇 |
1978年 | 18391篇 |
1977年 | 19761篇 |
1976年 | 23235篇 |
1975年 | 16505篇 |
1974年 | 15926篇 |
1973年 | 16089篇 |
1972年 | 13498篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
G Mangiapan M Vokurka L Schouls J Cadranel D Lecossier J van Embden AJ Hance 《Canadian Metallurgical Quarterly》1996,34(5):1209-1215
The rapid identification of mycobacterial DNA in clinical samples by PCR can be useful in the diagnosis of tuberculous infections, but several large studies have found that the sensitivity of this approach is not better than that of culture. In order to improve the sensitivity of detection of mycobacterial DNA in clinical specimens from patients with paucibacillary forms of tuberculosis, we have developed a procedure permitting the specific capture of mycobacterial DNA in crude samples prior to amplification, thereby concentrating the target sequences and removing irrelevant DNA and other potential inhibitors of the amplification reaction (sequence capture-PCR). By using this approach to capture and amplify two different sequences specific for organisms of the Mycobacterium tuberculosis complex (IS6110 and the direct repeat region), it was possible to detect as little as one genome of mycobacterial DNA in samples containing up to 750 micrograms of total DNA, representing a 10- to 100-fold increase in sensitivity compared with that obtained by purifying total DNA prior to amplification. Detection of the IS6110 sequence in pleural fluid samples from patients with tuberculous pleurisy by sequence capture-PCR gave positive results in 13 of 17 cases, including 3 of 3 culture-positive samples and 10 of 14 culture-negative samples. In contrast, when total DNA was purified from these samples by adsorption to a silica matrix prior to amplification, only the three culture-positive samples were positive by PCR. The sensitivity of detection of the direct repeat sequence in these samples by sequence capture-PCR was similar to that of IS6110 and, in addition, permitted immediate typing of the strains from some patients. We conclude that sequence capture-PCR improves the sensitivity of detection of mycobacterial DNA in paucibacillary samples. This approach should be useful in detecting rare target sequences from organisms implicated in other pathologic processes. 相似文献
962.
Muralidhar N. Ingale Vijaykumar V. Mahajani 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,64(1):80-86
The effectiveness of the hybrid system sonication followed by wet oxidation (SONIWO) to treat otherwise refractory waste has been demonstrated. In such a hybrid system homogeneous CuSO4 catalyst was found to be very efficient. 相似文献
963.
A novel class of narrow-band tunable wavelength filters is proposed and evaluated. Wavelength selectivity of the proposed filters Is derived from the finite time response of an optical nonlinearity. The nonlinearity is gain saturation in semiconductor optical amplifier structures. The filters are shown to have very narrow passbands tunable over the entire semiconductor gain bandwidth. The key to filter implementation is a device configuration in which the wave-mixing products can be isolated from the amplified inputs. Three integrated optics compatible configurations are considered and shown to have high filter throughputs 34 to 180% and subangstrom bandwidths 相似文献
964.
This paper explains the principle of a method which avoids printing of phantom resist lines due to undesired intensity minima appearing on Cr-less edge line phase-shifting masks. The method combines principles of grey-tone lithography and attenuated phase-shifting masks to give, what we call, a Cr-Less Attenuated Phase-shifting mask (CLAP). Rules for generating a CLAP design and a paradigm setup of a CLAP mask are presented. The capabilities and possible limitations of the CLAP method based on simulated results for a standard wafer stepper setup using the SOLID lithography simulator are being assessed. 相似文献
965.
Particles and gases can deposit from the atmosphere to polar snow by several mechanisms. Dry deposition can be considered to consist of three steps: aerodynamic transport from the free atmosphere to the viscous sublayer near the surface, boundary layer transport across the sublayer, and interactions with the surface. The particle dry deposition mass flux is dominated by the largest particles present in a size distribution. Wet deposition includes in-cloud and below-cloud scavenging, where the former refers to uptake of particles during nucleation of cloudwater as well as scavenging of particles and gases by existing droplets and ice crystals. Of all the wet deposition mechanisms, nucleation scavenging is often the most important mechanism for particles in the polar regions. Finally, incorporation of particles and gases into fog droplets and subsequent settling of the fog to the snow surface can be an important removal process in regions of frequent fog. For Summit, Greenland, the total deposition of MSA, SO42-, Na+, K+, and Ca2+ during May 24-July 13, 1993 was dominated by wet deposition: this mechanism accounted for an average of 62% of the total deposition for these species. Fog and dry deposition accounted for 21% and 17% of the total, respectively. These results suggest that all three mechanisms may need to be considered when estimating total deposition of certain chemical species to polar snow. 相似文献
966.
V. A. Arzamastsev N. L. Sardaev A. S. Kochergin 《Metal Science and Heat Treatment》1996,38(11):477-479
The technological process of cold forging applied for the first time in the production of the casing of the internal joint with races is described. The process operations of cold forging and the annealing and carburizing regimes for this part me described. 相似文献
967.
E. I. Khodorov 《Fibre Chemistry》1995,27(2):117-121
Low- and medium-temperature regeneration of active carbons saturated with caprolactam was investigated in regenerating medium (nitrogen, vapor–gas mixture) and without it. The optimum conditions of conducting the process were determined. The results of laboratory studies of thermal regeneration of active carbons were confirmed in experimental-industrial tests.All-Union Scientific-Research Institute of Synthetic Fibres, Tver'. Translated from Khimicheskie Volokna, No. 2, pp. 43–47, March–April, 1995. 相似文献
968.
969.
F. J. Carrière H. Sekiguchi N. N. Surin V. A. Kotelnikov Ya. S. Vygodskii 《Polymer Bulletin》1995,35(4):441-448
Summary Polyimides (PI) having different molecular weights were prepared by condensation of oxydiphthalic anhydride with 9,9-bis-(4-aminophenyl)fluorene in nitrobenzene solution at 180°C. These polyimides carried two amino chain ends which allowed us to fix polycaprolactam chains (PA6) to obtain PA6-PI-PA6 type copolymers. The elemental analysis and infrared spectroscopic determination gave the proportion of PA6 (or PI) in the copolymers. The studies of thermal properties-DSC and TGA-allowed us to characterize the copolymers. 相似文献
970.
Patrick R. Taylor Ph.D. Milton Manrique Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1996,48(6):43-45
Due to several inherent advantages, plasma processing technology may become a very useful tool in the production of new materials. An increasing research effort based on experimental as well as theoretical investigations has been invested in this area for the synthesis of advanced materials. In describing the thermal-plasma processing technique, this article employs examples from research at the Plasma Processing Laboratory at the University of Idaho. 相似文献