全文获取类型
收费全文 | 3485篇 |
免费 | 71篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 114篇 |
化学工业 | 715篇 |
金属工艺 | 116篇 |
机械仪表 | 46篇 |
建筑科学 | 51篇 |
能源动力 | 96篇 |
轻工业 | 256篇 |
水利工程 | 3篇 |
石油天然气 | 5篇 |
无线电 | 364篇 |
一般工业技术 | 602篇 |
冶金工业 | 916篇 |
原子能技术 | 95篇 |
自动化技术 | 186篇 |
出版年
2023年 | 20篇 |
2022年 | 64篇 |
2021年 | 78篇 |
2020年 | 30篇 |
2019年 | 30篇 |
2018年 | 55篇 |
2017年 | 50篇 |
2016年 | 66篇 |
2015年 | 38篇 |
2014年 | 79篇 |
2013年 | 118篇 |
2012年 | 102篇 |
2011年 | 145篇 |
2010年 | 91篇 |
2009年 | 112篇 |
2008年 | 116篇 |
2007年 | 112篇 |
2006年 | 96篇 |
2005年 | 93篇 |
2004年 | 99篇 |
2003年 | 95篇 |
2002年 | 89篇 |
2001年 | 58篇 |
2000年 | 58篇 |
1999年 | 60篇 |
1998年 | 375篇 |
1997年 | 212篇 |
1996年 | 153篇 |
1995年 | 95篇 |
1994年 | 121篇 |
1993年 | 93篇 |
1992年 | 41篇 |
1991年 | 44篇 |
1990年 | 47篇 |
1989年 | 43篇 |
1988年 | 41篇 |
1987年 | 35篇 |
1986年 | 33篇 |
1985年 | 44篇 |
1984年 | 16篇 |
1983年 | 20篇 |
1982年 | 24篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 43篇 |
1975年 | 13篇 |
1972年 | 10篇 |
排序方式: 共有3565条查询结果,搜索用时 15 毫秒
991.
992.
Brain activity associated with graphic emoticons. The effect of abstract faces in communication over a computer network 总被引:1,自引:0,他引:1
In this paper, we describe the brain activities that are associated with graphic emoticons by using functional MRI (fMRI). We use various types of faces, from abstract to photorealistic, in computer network applications. A graphics emoticon is an abstract face in communication over a computer network. In this research, we created various graphic emoticons for the fMRI study and the graphic emoticons were classified according to friendliness and level of arousal. We investigated the brain activities of participants who were required to evaluate the emotional valence of the graphic emoticons (happy or sad). The experimental results showed that not only the right inferior frontal gyrus and the cingulate gyrus, but also the inferior and middle temporal gyrus and the fusiform gyrus, were found to be activated during the experiment. Furthermore, it is possible that the activation of the right inferior frontal gyrus and the cingulate gyrus is related to the type of abstract face. Since the inferior and middle temporal gyrus were activated, even though the graphic emoticons are static, we may perceive graphic emoticons as dynamic and living agents. Moreover, it is believed that text and graphics emoticons play an important role in enriching communication among users. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 177(3): 36–45, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21162 相似文献
993.
Yuta Osawa Kenichiro Iwasaki Takayuki Nakanishi Atsuo Yasumori Yoshio Matsui Toshiyuki Nishimura Takeo Ohsawa Hiroyo Segawa Naoki Ohashi 《Journal of the American Ceramic Society》2021,104(9):4420-4432
The development of transparent glass for use in high-temperature applications is continuing. In this study, we synthesized bulk silicon oxynitride glasses (a-Si(O,N)x) through the nitridation of SiO2 aerogels containing methyl (CH3-) groups and evaluated their bulk properties, including their glass transition temperature (Tg). Tetramethyl orthosilicate and methyltrimethoxysilane were added into the precursor gels, and those gels were subjected to a supercritical CO2 drying process. The presence of CH3-group in the gel avoided cracking during ammonolysis at 750°C–1400°C, and the transparency of the gel was remained even after ammonolysis at 1300°C. The ammonolysis successfully introduced nitrogen into the gels even at relatively low temperatures, for example, 750°C, and the highest nitrogen content (11.7 mass%) was achieved in the gel after ammonolysis at 1300°C. As the nitrogen-related signals in electron spectroscopy indicated presence of nitride ions (N3−) after ammonolysis and the infrared absorption signals attributed to Si–N bonds were enhanced with the increase of nitrogen concentration, we successfully obtained oxynitride glasses. Those oxynitride glasses showed increase of Tg with their nitrogen concentration. 相似文献
994.
Chiaki Uchida Hiroki Mizukami Yutaro Hara Takeshi Saito Satoko Umetsu Akiko Igawa Sho Osonoi Kazuhiro Kudoh Yasuhiko Yamamoto Hiroshi Yamamoto Soroku Yagihashi Kenichi Hakamada 《International journal of molecular sciences》2021,22(21)
Pancreatic stellate cells (PSCs) mainly consist of cancer-associating fibroblasts in pancreatic ductal adenocarcinoma (PDAC). The receptor for advanced glycation end products (RAGE) is implicated in the pathophysiology of diabetic complications. Here, we studied the implication of RAGE in PSC activation in PDAC. The activation of cultured mouse PSCs was evaluated by qPCR. The induction of epithelial mesenchymal transition (EMT) in PDAC cell lines was assessed under stimulation with culture supernatant from activated PSCs. A total of 155 surgically resected PDAC subjects (83 nondiabetic, 18 with ≦3-years and 54 with >3-years history of diabetes) were clinicopathologically evaluated. A high-fat diet increased the expression of activated markers in cultured PSCs, which was abrogated by RAGE deletion. Culture supernatant from activated PSCs facilitated EMT of PDAC cells with elevation of TGF−β and IL−6, but not from RAGE−deleted PSCs. Diabetic subjects complicated with metabolic syndrome, divided by cluster analysis, showed higher PSC activation and RAGE expression. In such groups, PDAC cells exhibited an EMT nature. The complication of metabolic syndrome with diabetes significantly worsened disease−free survival of PDAC subjects. Thus, RAGE in PSCs can be viewed as a new promoter and a future therapeutic target of PDAC in diabetic subjects with metabolic syndrome. 相似文献
995.
Yoshinori Ohmura Naoki Ishimori Akimichi Saito Takashi Yokota Shunpei Horii Satoshi Tokuhara Kazuya Iwabuchi Hiroyuki Tsutsui 《International journal of molecular sciences》2021,22(22)
The infiltration and activation of macrophages as well as lymphocytes within atherosclerotic lesion contribute to the pathogenesis of plaque rupture. We have demonstrated that invariant natural killer T (iNKT) cells, a unique subset of T lymphocytes that recognize glycolipid antigens, play a crucial role in atherogenesis. However, it remained unclear whether iNKT cells are also involved in plaque instability. Apolipoprotein E (apoE) knockout mice were fed a standard diet (SD) or a high-fat diet (HFD) for 8 weeks. Moreover, the SD- and the HFD-fed mice were divided into two groups according to the intraperitoneal injection of α-galactosylceramide (αGC) that specifically activates iNKT cells or phosphate-buffered saline alone (PBS). ApoE/Jα18 double knockout mice, which lack iNKT cells, were also fed an SD or HFD. Plaque instability was assessed at the brachiocephalic artery by the histological analysis. In the HFD group, αGC significantly enhanced iNKT cell infiltration and exacerbated atherosclerotic plaque instability, whereas the depletion of iNKT cells attenuated plaque instability compared to PBS-treated mice. Real-time PCR analyses in the aortic tissues showed that αGC administration significantly increased expressional levels of inflammatory genes such as IFN-γ and MMP-2, while the depletion of iNKT cells attenuated these expression levels compared to those in the PBS-treated mice. Our findings suggested that iNKT cells are involved in the exacerbation of plaque instability via the activation of inflammatory cells and upregulation of MMP-2 in the vascular tissues. 相似文献
996.
Acyl glucuronides, which are biosynthesized by the action of glucuronosyltransferases to material for detoxification, are
water-soluble and chemically active; they produce irreversible protein adducts via both the transacylation mechanism and the imine mechanism. The acyl group at the C-1 position migrates from the anomeric
carbon to the C-2 position of the glucuronic acid moiety, producing the aldehyde group at the C-1 position, where the protein
easily condenses through a Schiff's base, in the open-chain aldose form. The elimination of the hydroxyl group at the C-2
position therefore may prevent a protein-bound adduct via the imine mechanism. In this paper, we describe the synthesis and characterization of an acyl 2-deoxyglucuronide of deoxycholic
acid as a model compound to investigate its possible utility as a water-soluble affinity labeling reagent for lipophilic carboxylic
acids. The solubility of deoxycholyl 2-deoxyglucuronide in an aqueous solution was sufficient under physiological conditions,
and the desired material reacted with model peptides to produce covalently bound adducts only via the transacylation mechanism. 相似文献
997.
Formation mechanism, crystallinity, porosity and chemical reactivity were studied on the carbon prepared by pyrolysis of single phase, stage-1 fluorine-graphite intercalation compound (fluorine-GIC; CxF). The stage-1 C2.5F directly decomposes to fluorocarbon gases and carbon above 650 K, without forming higher stage compounds. The pyrocarbon prepared from C2.5F gives hkl diffraction peaks indicating graphite-like stacking order of graphene layers. This carbon possesses average crystallite sizes along the c- and a-axes (Lc and La) of about 5 and 50 nm, respectively. The specific surface area of the pyrocarbon (about 40 m2 g−1) is only twice as large as that of the original crystalline graphite. Chemical behavior of the pyrocarbon as an intercalation host for sodium and potassium is similar to that of crystalline graphite, but it is easily fluorinated by elemental fluorine even at 573 K to give poly(carbon monofluoride) [(CF)n] probably due to the small crystallite size and the mesopores formed by formation/decomposition processes of C2.5F. 相似文献
998.
Yuta Komano Kazunori Shimada Hisashi Naito Kosuke Fukao Yoshihiko Ishihara Toshio Fujii Takeshi Kokubo Hiroyuki Daida 《Journal of the International Society of Sports Nutrition》2018,15(1):39
Background
Lactococcus lactis JCM 5805 (LC-Plasma) is a unique lactic acid bacteria (LAB) which activates plasmacytoid dendritic cells (pDC). We aimed to evaluate the effect of LC-Plasma on dendritic cell (DC) activity and subjective indices of upper respiratory tract infections (URTI) and fatigue in athletes under high intensity exercise.Methods
We conducted a randomized, placebo-controlled, double-blinded trial. Fifty-one male subjects belonging to a university sports club were randomized into placebo (n?=?25) and LC-Plasma (n?=?26) groups. Individuals ingested placebo capsules containing cornstarch or LC-Plasma capsules containing 100 billion cells of heat-killed LC-Plasma per day for 13 days. During the intervention period, subjects performed high intensity exercise according to their sports club training regime. Blood and saliva sampling were obtained at days 1 and 14, and physical conditions were recorded in a diary. We investigated expression of maturation markers on DCs, muscle damage and stress markers and used student’s t test adjusted by Bonferoni’s method for multiple comparison between groups. These data were presented as mean?±?SD. We also investigated cumulative days of symptoms regarding infections and fatigue and used Chi-square test for comparison between groups. These data were presented as cumulative number.Results
CD86 as maturation marker on pDC was significantly increased in the LC-Plasma group at day 14 (Placebo: 296?±?70 vs. LC-Plasma: 365?±?115; Mean Fluorescent Intensity; p?=?0.013). Cumulative days of URTI were significantly lower in the LC-Plasma group (Placebo: URTI positive 56, URTI negative 256 vs. LC-Plasma: URTI positive 39, URTI negative 299; days; p?=?0.028) and symptoms like sneeze or running nose were significantly lower in the LC-Plasma group (Placebo: Symptom positive 52, Symptom negative 258, vs. LC-Plasma: Symptom positive 36, Symptom negative 301; days; p?=?0.032). Moreover, the cumulative days of fatigue were significantly fewer in the LC-Plasma group (Placebo: Symptom positive 128, Symptom negative 182, vs. LC-Plasma: Symptom positive 110, Symptom negative 225; days; p?=?0.032). Markers of muscle damage and stress markers were not significantly different between groups.Conclusion
We consider that heat-killed LC-Plasma supplementation relieves morbidity and symptoms of URTI via activation of pDC and decreases fatigue accumulation during consecutive high intensity exercise in athletes. However, LC-Plasma ingestion did not affect markers of muscle damage and stress.Trial registration
UMIN-CTR, UMIN000020372. Registered 28 December 2015.999.
The crystalline morphology of poly(ethylene 2,6-naphthalate) (PEN) film obtained by uniaxial stretching at 145 °C (Tg + 25 °C) was investigated by use of a light scattering photometer equipped with a CCD camera system. The Hv scattering showed a symmetric, circular pattern at a low stretch ratio of λ < 3. The intensity profile became sharper with an increase in λ, suggesting that anisotropic crystal rods are randomly assembled and that the length of the rods increases with λ. At a high stretch ratio of λ ≥ 3, a double-cross-type pattern consisting of a broad rod-like pattern and sharp cross streaks was observed. The rod-like pattern became smaller and the streaks became sharper with an increase in λ. By the model calculation of the scattering pattern, the double-cross-type pattern is explained by the stacking of anisotropic crystal rods oriented in the stretch direction. As λ increases, the thickness of the rods and the number per stack increase, and the stacks and rods are slightly oriented in the stretch direction. The change in the wide angle X-ray diffraction pattern suggested that the ordering of the molecular chain in the crystal rods increases with increasing λ. 相似文献