全文获取类型
收费全文 | 1919篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 40篇 |
综合类 | 1篇 |
化学工业 | 183篇 |
金属工艺 | 20篇 |
机械仪表 | 23篇 |
建筑科学 | 24篇 |
矿业工程 | 3篇 |
能源动力 | 13篇 |
轻工业 | 114篇 |
水利工程 | 7篇 |
石油天然气 | 8篇 |
武器工业 | 2篇 |
无线电 | 234篇 |
一般工业技术 | 164篇 |
冶金工业 | 950篇 |
原子能技术 | 3篇 |
自动化技术 | 160篇 |
出版年
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 16篇 |
2014年 | 22篇 |
2013年 | 38篇 |
2012年 | 36篇 |
2011年 | 34篇 |
2010年 | 15篇 |
2009年 | 29篇 |
2008年 | 40篇 |
2007年 | 53篇 |
2006年 | 38篇 |
2005年 | 46篇 |
2004年 | 32篇 |
2003年 | 49篇 |
2002年 | 42篇 |
2001年 | 43篇 |
2000年 | 32篇 |
1999年 | 63篇 |
1998年 | 343篇 |
1997年 | 178篇 |
1996年 | 129篇 |
1995年 | 85篇 |
1994年 | 71篇 |
1993年 | 90篇 |
1992年 | 35篇 |
1991年 | 29篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 15篇 |
1987年 | 25篇 |
1986年 | 22篇 |
1985年 | 25篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 17篇 |
1979年 | 5篇 |
1977年 | 21篇 |
1976年 | 29篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1972年 | 5篇 |
排序方式: 共有1949条查询结果,搜索用时 15 毫秒
1.
The ability of oral lactobacilli to coaggregate with streptococci and actinomycetes was investigated. Of the 7 species of lactobacilli studied, only two were capable of coaggregation and the coaggregation was restricted to streptococci. Lactobacillus salivarius strains (2/4) coaggregated with Streptococcus salivarius, Streptococcus gordonii, Streptococcus crista and tufted Streptococcus sanguis II strains. Lactobacillus fermentum (2/3) coaggregated with S. gordonii and S. sanguis. The coaggregation between L. salivarius and S. salivarius, S. gordonii or tufted S. sanguis II strains was mediated by a protein on the surface of the lactobacilli and was not inhibited by lactose. The coaggregation between L. fermentum and the streptococci was mediated by protein on the surface of the streptococci and was inhibited by lactose. 相似文献
2.
3.
In this study we have investigated the role of CD4+, MHC class II-restricted cytotoxic T lymphocytes (CTLs) in the disease caused by lymphocytic choriomeningitis virus (LCMV) in beta 2-microglobulin deficient (beta 2m-) mice. Intracranial (i.c.) infection with LCMV resulted in death of six out of 11 beta 2m- mice. Mice that survived showed a marked loss in body weight. Death and loss of body weight could be prevented by immunosuppressing the mice with irradiation or cyclosporine prior to i.c. injection of LCMV. This treatment also prevented induction of virus-specific, MHC class II-restricted CTL following peripheral inoculation with LCMV. In vivo depletion of CD4+ cells with antibody also prevented death following i.c. injection whereas in vivo depletion of CD8+ cells had no effect. Disease could be transferred to recipient beta 2m- mice by adoptive transfer of beta 2m- derived immune spleen cells. Transfer of non-immune spleen cells did not result in illness. In vitro treatment of immune spleen cells with anti-CD4 antibody and complement eliminated class II-restricted CTL activity and also prevented mortality of recipients after adoptive transfer. Treatment with anti-CD8 antibody had no effect. We were unable to transfer LCM disease to beta 2m- recipients by adoptive transfer of immune spleen cells from C57BL/6 mice. These results suggest that, unlike normal mice, the pathology of LCM disease in beta 2m- mice is dependent upon virus-specific, CD4+CD8-, MHC class II-restricted T cells. 相似文献
4.
Gunapala S.D. Bundara S.V. Liu J.K. Winn Hong Mani Sundaram Maker P.D. Muller R.E. Shott C.A. Carralejo R. 《Electron Devices, IEEE Transactions on》1998,45(9):1890-1895
A 9-μm cutoff 640×486 snap-shot quantum well infrared photodetector (QWIP) camera has been demonstrated. The performance of this QWIP camera is reported including indoor and outdoor imaging. The noise equivalent differential temperature (NEΔT) of 36 mK has been achieved at 300 K background with f/2 optics. This is in good agreement with expected focal plane array sensitivity due to the practical limitations on charge handling capacity of the multiplexer, read noise, bias voltage, and operating temperature 相似文献
5.
LG Westergaard PE Rasmussen S Maigaard HJ Ingerslev AN Andersen JF Larsen J Starup PJ Hornnes CY Andersen 《Canadian Metallurgical Quarterly》1993,155(33):2511-2514
Medical indications for in vitro fertilization and embryo transfer (IVF-ET) internationally and in Denmark are reviewed. Reports from large international centres document that tubal infertility, unexplained infertility, endometriosis and male infertility are equally good indications for IVF. Traditionally, tubal infertility has been the only medical indication qualifying for IVF treatment within the National Health Service in Denmark. Thus, in this country, couples with unexplained and male infertility and with endometriosis have to pay up to 25,000 D.Kr. per IVF-ET treatment in private fertility clinics. Since there is no scientific basis for this discrimination, it is urged that the present rules are changed, so that couples with unexplained and male infertility and endometriosis are also allowed IVF treatment free of charge in the public fertility clinics. 相似文献
6.
7.
SiC-based field-effect gas sensors with catalytic platinum electrodes (Pt-MOSiC) have been subjected to a series of gas response measurements. Structural analysis of the Pt electrodes revealed that the gas sensitivity and the selectivity of Pt-MOSiC gas sensors depend on two major parameters: the porosity and the catalytic activity of the Pt electrodes. Pt-MOSiC gas sensors with thick, dense Pt electrodes only exhibit hydrogen sensitivity, whereas Pt-MOSiCs with thin porous gates exhibit a broad range of gas sensitivities similar to resistive metal-oxide gas sensors. A model is put forward that explains the nonhydrogen gas response of Pt-MOSiC devices and of conventional polycrystalline metal-oxide materials on a common basis. 相似文献
8.
9.
Averin S.V. Kohl A. Muller R. Mesquida Kusters A. Wisser J. Heime K. 《Electronics letters》1992,28(11):992-995
The p/sup +/-cap layer was used to fabricate a metal-semiconductor-metal (MSM) interdigitated photodetector on Ga/sub 0.47/In/sub 0.53/As. The measured barrier height was Phi /sub Bn=/0.52 V, the ideality factor n=1.1 and average dark current density 2 mA/cm/sup 2/. A rise time of 45 ps at lambda =1.3 mu m under 2 V bias was measured for an MSM photodiode with 3 mu m finger width and finger gaps and an active area of 100*100 mu m/sup 2/.<> 相似文献
10.