全文获取类型
收费全文 | 4935篇 |
免费 | 271篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 65篇 |
综合类 | 3篇 |
化学工业 | 1318篇 |
金属工艺 | 176篇 |
机械仪表 | 104篇 |
建筑科学 | 134篇 |
矿业工程 | 15篇 |
能源动力 | 171篇 |
轻工业 | 575篇 |
水利工程 | 10篇 |
石油天然气 | 10篇 |
无线电 | 178篇 |
一般工业技术 | 775篇 |
冶金工业 | 1100篇 |
原子能技术 | 23篇 |
自动化技术 | 555篇 |
出版年
2023年 | 28篇 |
2022年 | 57篇 |
2021年 | 265篇 |
2020年 | 113篇 |
2019年 | 97篇 |
2018年 | 182篇 |
2017年 | 178篇 |
2016年 | 198篇 |
2015年 | 146篇 |
2014年 | 198篇 |
2013年 | 315篇 |
2012年 | 221篇 |
2011年 | 284篇 |
2010年 | 185篇 |
2009年 | 165篇 |
2008年 | 158篇 |
2007年 | 156篇 |
2006年 | 115篇 |
2005年 | 93篇 |
2004年 | 88篇 |
2003年 | 70篇 |
2002年 | 62篇 |
2001年 | 44篇 |
2000年 | 32篇 |
1999年 | 40篇 |
1998年 | 198篇 |
1997年 | 218篇 |
1996年 | 148篇 |
1995年 | 113篇 |
1994年 | 57篇 |
1993年 | 72篇 |
1992年 | 20篇 |
1991年 | 15篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 21篇 |
1987年 | 27篇 |
1986年 | 19篇 |
1985年 | 31篇 |
1984年 | 34篇 |
1983年 | 30篇 |
1982年 | 48篇 |
1981年 | 53篇 |
1980年 | 60篇 |
1979年 | 32篇 |
1978年 | 38篇 |
1977年 | 122篇 |
1976年 | 239篇 |
1975年 | 19篇 |
1973年 | 13篇 |
排序方式: 共有5212条查询结果,搜索用时 15 毫秒
11.
Jan Bilski Agnieszka Irena Mazur-Bialy Marcin Surmiak Magdalena Hubalewska-Mazgaj Janusz Pokorski Jacek Nitecki Ewa Nitecka Joanna Pokorska Aneta Targosz Agata Ptak-Belowska Jerzy A. Zoladz Tomasz Brzozowski 《International journal of molecular sciences》2020,21(22)
Physical exercise is known to influence hormonal mediators of appetite, but the effect of short-term maximal intensity exercise on plasma levels of appetite hormones and cytokines has been little studied. We investigated the effect of a 30 s Wingate Test, followed by a postprandial period, on appetite sensations, food intake, and appetite hormones. Twenty-six physically active young males rated their subjective feelings of hunger, prospective food consumption, and fatigue on visual analogue scales at baseline, after exercise was completed, and during the postprandial period. Blood samples were obtained for the measurement of nesfatin-1, ghrelin, leptin, insulin, pancreatic polypeptide (PP), human growth factor (hGH) and cytokine interleukin-6 (IL-6), irisin and plasma lactate concentrations, at 30 min before exercise, immediately (210 s) after exercise, and 30 min following a meal and at corresponding times in control sedentary males without ad libitum meal intake, respectively. Appetite perceptions and food intake were decreased in response to exercise. Plasma levels of irisin, IL-6, lactate, nesfatin-1 and ghrelin was increased after exercise and then it was returned to postprandial/control period in both groups. A significant rise in plasma insulin, hGH and PP levels after exercise was observed while meal intake potentiated this response. In conclusion, an acute short-term fatiguing exercise can transiently suppress hunger sensations and food intake in humans. We postulate that this physiological response involves exercise-induced alterations in plasma hormones and the release of myokines such as irisin and IL-6, and supports the notion of existence of the skeletal muscle–brain–gut axis. Nevertheless, the detailed relationship between acute exercise releasing myokines, appetite sensations and impairment of this axis leading to several diseases should be further examined. 相似文献
12.
Analysis of non-stationary electrochemical oscillations emerges utilization of the techniques allowing an observation of time evolution of their parameters such as instantaneous frequency, amplitude or frequency band. An algorithm of extraction of these parameters can be based on one of linear or quadratic time-frequency representations of oscillations record. In this paper, the authors present representatives of such transformations (Choi-Williams and Cone-shaped) originating from one of the most popular joint time-frequency energy distribution—Wigner-Ville distribution. Short introduction to the mathematics of the topic discussed is provided, then the authors present an example of application in the analysis of current oscillations of copper dissolution process. 相似文献
13.
A Sawicka-Grzelak F Meisel-Miko?ajczyk SM S?otwińska M Wierzbicka 《Canadian Metallurgical Quarterly》1997,49(1-2):95-100
The aim of study was the evaluation of periodontal pockets microflora in patients with advanced periodontitis. From each subject 16-20 samples were taken using paper points. Pooled sample after 60 s. mixing was serially diluted in reduced BHI. For total cell counts and for the isolation of black pigmented anaerobes Brucella agar supplemented with 5% sheep blood, hemin, menadione, with and without Kanamycin-Vancomycin mixture and BM agar plates were used. For isolation of A. actinomycetemcomitans TSBV agar plates were used. Cultures were incubated in anaerobic chamber at 37 degrees C for 7 days and TSBV agar plates in an atmosphere of 95% air-5% CO2 at 37 degrees C for 5 days. Microorganisms were identified by Gram staining, colony morphology, fluorescence in UV-light, haemagglutination of 3% sheep erythrocytes, fermentation of sugars, production of indole, urease (API 20A), specific enzymes (Rapid ID 32A). Twenty seven subjects with clinically recognized periodontitis were examined. Microorganisms important in periodontitis were isolated from periodontal pockets of almost all examined subjects. The number of bacteria obtained from the sample of one patient ranged from 1 x 10(4) CFU/ml to 3,6 x 10(6) CFU/ml. Porphyromonas gingivalis was identified in the samples taken from 17 patients, Prevotella intermedia-19, Actinobacillus actinomycetemcomitans -11, Fusobacterium nucleatum-9, Peptostreptococcus spp.-22. 相似文献
14.
The effect of a novel flavonoid, venoruton (a mixture of mono-, di-, tri- and tetrahydroxyethylrutosides) has been investigated in healthy rat lenses and compared with diabetic cataract modelled in vitro. One mM venoruton was added to medium simulating healthy and diabetic conditions for the incubated lenses; damage was followed by either stereoscopic photography of the lenses under a Cooperative Cataract Research Group operating microscope or with our recently developed method: the leakage of lactate dehydrogenase (LDH) into the lens culture media. The increased LDH activity in the medium and observable development of the opacity were correlated with cell damage, which has been found to be associated with globular degeneration and cataract formation. The extent of opacification and LDH release is reduced if 1 mM venoruton is included in the medium. The protective effect may be related to antioxidant activity against reactive oxygen species: decreased luminol luminescence was shown after venoruton addition to either superoxide-generating hypoxanthine plus xanthine oxidase, or hydrogen peroxide. 相似文献
15.
16.
The development of porosity in the course of carbonization of a flame coal, original and pre-oxidized, was studied by means of the adsorption of benzene and carbon dioxide. The results were compared with corresponding data for cokes from a xylitic brown coal. The influence of coal oxygen content on the formation of coke porosity and its thermal dependence is discussed. 相似文献
17.
S. Suppan J. Trawczyski J. Kaczmarczyk G. Djga-Mariadassou A. Hynaux C. Sayag 《Applied Catalysis A: General》2005,280(2):209-214
Carbon black composites (CBCs) have been prepared by pyrolyzing mixture of a carbon black with polyfurfuryl alcohol and then pretreated by oxidation with nitric acid, gasification with water steam or ammoxidation. The effects of the chemical character of the carrier surface, nature of the active metal phase and pH value of the impregnation solution on the catalytic activity towards the hydrodesulfurization (HDS) of thiophene of the CBC supported Mo (Co) catalysts were determined. It was stated that the catalytic properties of the CBC supported sulfides of Mo or Co and of Mo carbides are affected by the chemical character of the carrier surface. Generally, catalysts supported over basic surface CBC exhibit higher activity than those ones supported over CBC possessing acidic surface character. Co catalysts supported on acidic surface show lower activity (per mol of active metal) than Mo based ones supported on the same carrier. In the case of catalysts supported on basic CBC, Co exhibits distinctly higher activity than Mo. At the experimental conditions adopted for this study, CBC surface properties, active phase nature, and catalyst impregnation pH were found to exert a relatively small influence on both HDS and hydrogenation activities. 相似文献
18.
The effect of drying and atomization conditions on the physical properties of powders for agglomerate-like materials and skin-forming material are studied in this article. A neural model is used for powder bulk and tapped density predictions. 相似文献
19.
Textured milk proteins were tested in a meat model system with an exchange level of 34-87% of the meat proteins. The correlation between the substitution index and the calcium and phosphorus content was statistically significant. 相似文献
20.
Victor Chabanenko Roman Puźniak Adam Nabiałek Sergei Vasiliev Vladimir Rusakov Loh Huanqian Ritta Szymczak Henryk Szymczak Jan Jun Janusz Karpiński Vitaly Finkel 《Journal of Low Temperature Physics》2003,130(3-4):175-191
We present a study of magneto-thermal instabilities in polycrystalline MgB2 superconductor, by magnetic hysteresis loop measurements and by investigations of magnetic flux dynamics with a miniature Hall probe. Temperature and magnetic field ranges where the flux jumps may be observed have been determined. On the basis of measurements of the magnetic flux dynamics, an average magnetic diffusivity describing the process of the flux jump is estimated. This parameter is compared with the thermal and magnetic diffusivities calculated on the basis of available data for thermal conductivity, heat capacity and resistivity. It is shown that the estimated value of the field of the first flux jump is influenced significantly by the field dependence of specific heat. In order to explain the observed phenomenon, the temperature reached by the sample during the flux jump at different magnetic fields is calculated. 相似文献