全文获取类型
收费全文 | 3095篇 |
免费 | 65篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 192篇 |
综合类 | 5篇 |
化学工业 | 1034篇 |
金属工艺 | 97篇 |
机械仪表 | 105篇 |
建筑科学 | 93篇 |
能源动力 | 143篇 |
轻工业 | 194篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 152篇 |
一般工业技术 | 703篇 |
冶金工业 | 97篇 |
原子能技术 | 117篇 |
自动化技术 | 238篇 |
出版年
2023年 | 18篇 |
2022年 | 45篇 |
2021年 | 50篇 |
2020年 | 21篇 |
2019年 | 32篇 |
2018年 | 52篇 |
2017年 | 45篇 |
2016年 | 58篇 |
2015年 | 49篇 |
2014年 | 69篇 |
2013年 | 163篇 |
2012年 | 104篇 |
2011年 | 198篇 |
2010年 | 140篇 |
2009年 | 146篇 |
2008年 | 171篇 |
2007年 | 113篇 |
2006年 | 135篇 |
2005年 | 116篇 |
2004年 | 83篇 |
2003年 | 116篇 |
2002年 | 84篇 |
2001年 | 62篇 |
2000年 | 72篇 |
1999年 | 63篇 |
1998年 | 79篇 |
1997年 | 83篇 |
1996年 | 70篇 |
1995年 | 46篇 |
1994年 | 34篇 |
1993年 | 45篇 |
1992年 | 30篇 |
1991年 | 30篇 |
1990年 | 32篇 |
1989年 | 45篇 |
1988年 | 31篇 |
1987年 | 34篇 |
1986年 | 53篇 |
1985年 | 45篇 |
1984年 | 58篇 |
1983年 | 50篇 |
1982年 | 33篇 |
1981年 | 24篇 |
1980年 | 19篇 |
1979年 | 28篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 11篇 |
1974年 | 15篇 |
1973年 | 10篇 |
排序方式: 共有3179条查询结果,搜索用时 15 毫秒
41.
42.
43.
Kawase M He F Kubota A Hiramatsu M Saito H Ishii T Yasueda H Akiyama K 《International journal of food microbiology》2009,128(3):429-434
There has been much interest in the potential of using probiotic bacteria for treating allergic diseases. A double-blind, placebo-controlled study was conducted to examine the effectiveness of Lactobacillus GG (LGG) and L. gasseri TMC0356 (TMC0356) in alleviating Japanese cedar pollinosis (JCP), a seasonal allergic rhinitis caused by Japanese cedar pollen. Fermented milk prepared with the tested bacteria or placebo yoghurt was administered to 40 subjects with a clinical history of JCP for 10 weeks. Subjective symptoms, self-care measures and blood samples were compared between the two groups. Peripheral blood mononuclear cells (PBMCs) were collected from seven patients with JCP and in vitro cytokine production by the isolated PBMCs was analysed in the presence of heat-killed lactic acid bacteria. Consumption of the fermented milk significantly decreased the mean symptom score for nasal blockage after 9 weeks (P<0.05) and mean symptom-medication scores after 9 and 10 weeks when compared with the placebo group (P<0.01 and P<0.05 respectively). The tested strains of lactic acid bacteria affected cytokine production by isolated PBMCs in vitro in a strain-dependent manner. LGG significantly inhibited IL-4 and IL-5 production by PBMCs stimulated by both Cry j 1 and PHA. TMC0356 only suppressed IL-5 production stimulated by PHA. The fermented milk prepared with LGG and TMC0356 might be beneficial in JCP because of its effect on nasal blockage. The effects of LGG and TMC0356 might arise at least partly from their specific down-regulation of the human Th2 immune response. 相似文献
44.
45.
Bioaccumulation, temporal trend, and geographical distribution of synthetic musks in the marine environment 总被引:3,自引:0,他引:3
Nakata H Sasaki H Takemura A Yoshioka M Tanabe S Kannan K 《Environmental science & technology》2007,41(7):2216-2222
Bioaccumulation of synthetic musks in a marine food chain was investigated by analyzing marine organisms at various trophic levels, including lugworm, clam, crustacean, fish, marine mammal, and bird samples collected from tidal flat and shallow water areas of the Ariake Sea, Japan. Two of the polycyclic musks, HHCB and AHTN, were the dominant compounds found in most of the samples analyzed, whereas nitro musks were not detected in any of the organisms, suggesting greater usage of polycyclic musks relative to the nitro musks in Japan. The highest concentrations of HHCB were detected in clams (258-2730 ng/g lipid wt.), whereas HHCB concentrations in mallard and black-headed gull were low, and comparable with concentrations in fish and crab. These results are in contrast to the bioaccumulation pattern of polychlorinated biphenyls; for which a positive correlation between the concentration and the trophic status of organisms was found. Such a difference in the bioaccumulation is probably due to the metabolism and elimination of HHCB in higher trophic organisms. Temporal trends in concentrations of synthetic musks were examined by analyzing tissues of marine mammals from Japanese coastal waters collected during 1977-2005. HHCB concentrations in marine mammals have shown significant increase since the early 1990s, suggesting a continuous input of this compound into the marine environment. Comparison of the time trend for HHCB with those for PCBs and PBDEs suggested that the rates of increase in HHCB concentrations were higher than the other classes of pollutants. To examine the geographical distribution of HHCB, we have analyzed tissues of fish, marine mammals, and birds collected from several locations. Synthetic musks were not detected in a sperm whale (pelagic species) from Japanese coastal water and in eggs of south polar skua from Antarctica. While the number of samples analyzed is limited, these results imply a lack of long-range transportation potential of synthetic musks in the environment. 相似文献
46.
47.
Saitoh M Asaka K Arai M Kawabata A Kanoh S Kanoh T 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2002,43(4):243-249
In order to evaluate the relationship between nasal carriers of S. aureus and their history of allergic diseases, the total serum IgE titer, the hemogramme pattern, and the titers of specific IgE antibody to Staphylococcal enterotoxins A and B (SEA and SEB) and of specific IgG antibody to SEB were investigated in 98 trade school students. Fifteen (15.3%) of the 98 students were sensitized to SEA and/or SEB (40.0% to SEA and 93.3% to SEB). In this group, 11 subjects were S. aureus carriers (73.0%) and 12 had a history of allergic diseases (80.0%). Low levels of specific IgG antibody to SEB were identified from both S. aureus carriers and non-carriers. The S. aureus carriers had significantly higher levels of total IgE titer than the non-carriers and the individuals with a history of allergic diseases had significantly higher total IgE titer levels than those having no history of allergic diseases (p < 0.01). In the hemogramme patterns of S. aureus carriers, a significant positive correlation was observed between the total IgE antibodies and the eosinophil rate (p < 0.05), and a negative correlation (p < 0.001) was recognized between the neutrophil and the lymphocyte rates. 相似文献
48.
Sakai K Mori M Fujii A Iwami Y Chukeatirote E Shirai Y 《Journal of Bioscience and Bioengineering》2004,98(1):48-56
Reproducible amounts of lactic acid accumulate in minced kitchen refuse under open conditions with intermittent pH neutralization [Sakai et al., Food Sci. Technol. Res., 6, 140 (2000)]. Here, we showed that such pH-controlled open fermentation of kitchen refuse reproducibly resulted a selective proliferation of a major lactic acid bacterial (LAB) species. In one experiment, the predominant microorganisms isolated during the early phase (6 h) were Gammaproteobacteria. In contrast, those that predominated during the late phase (48 h) were always Lactobacillus plantarum in three independent experiments. To further quantify the microbial community within open lactic acid fermentation, we performed fluorescent in situ hybridization (FISH) analysis targeting 16S (23S) rRNA. We designed two new group-specific DNA probes: LAC722(L) was active for most LAB including the genera Lactobacillus, Pediococcus, Leuconostoc and Weisella, whereas Lplan477 was specific for L. plantarum and its related species. We then optimized sample preparation using lysozyme and hybridization conditions including temperature, as well as the formamide concentration and the salt concentration in the washing buffer. We succeeded in quantification of microorganisms in semi-solid, complex biological materials such as minced kitchen refuse by taking color microphotographs in modified RGB balance on pre-coated slides. FISH analysis of the fermentation of kitchen refuse indicated that control of the pH swing leads to domination by the LAB population in minced kitchen refuse under open conditions. We also confirmed that L. plantarum, which generates lactic acid in high quantities but with low optical activity, became the dominant microorganism in kitchen refuse during the late phase of open fermentation. 相似文献
49.
The semi-empirical CNDO/2 SCF (self-consistent field) MO (molecular orbital) method using the tight-binding approximation for polymers was applied to polyglycine. The CNDO/2 calculations were also performed on model systems of this polymer. From the calculated results, the characteristics of the hydrogen bond in the α-helix were derived by comparison with those in the model systems. It was found that the hydrogen bond in the α-helix is very stable against proton transfer whereas the hydrogen bond in the model system is not so stable; this characteristic difference between the two systems is due to the coupling of two π-electron systems through hydrogen bonding in the α-helix. 相似文献
50.
Dimethylsiloxane-tetramethyl-p-silphenylenesiloxane-dimethylsiloxane (DMS-TMPS-DMS) triblock copolymer was synthesized by employing living anionic polymerization of hexamethylcyclotrisiloxane (D3). Two synthetic methods were carried out for the polymerization. One of those methods was the anionic polymerization of D3 initiated at the silanolate anion which was prepared from the terminal hydroxyl group of silanol-terminated TMPS prepolymer by reaction with n-butyllithium (method 1). The other was the coupling reaction of vinyl-terminated TMPS prepolymer with hydrosilyl-terminated DMS prepolymer obtained from the anionic polymerization of D3 by using diphenylmethylsilanolate anion as initiator (method 2). In method 1, DMS contents of the copolymers ranged from 25.8 to 72.5 wt% and the values agreed with the ratio of D3 to TMPS prepolymer. The weight-average molecular weights ranged from 1.36×104 to 19.4×104 and were close to the predicted values calculated from the of the TMPS prepolymer and the amount of D3 added. In the case of method 2, weight-average molecular weights ranged from 19.5×104 to 24.2×104. The high molecular weight copolymer could thus be obtained by method 2. Intrinsic viscosity values of the triblock copolymers agreed with calculated values obtained by considering the copolymer as a binary mixture of these homopolymers. Differential scanning calorimetry and thermogravimetry were carried out on the triblock copolymers. The equilibrium melting temperatures of each of the copolymers were very close to that of poly-TMPS (160°C). The glass transition temperature and heat of fusion were decreased as the DMS content was increased. The thermogravimetric curves for the copolymers indicated that the thermal stability of the triblock copolymer was intermediate between the DMS and TMPS homopolymers. 相似文献