首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   23895篇
  免费   2615篇
  国内免费   692篇
电工技术   132篇
技术理论   1篇
综合类   1170篇
化学工业   7200篇
金属工艺   580篇
机械仪表   184篇
建筑科学   734篇
矿业工程   225篇
能源动力   476篇
轻工业   10850篇
水利工程   190篇
石油天然气   803篇
武器工业   24篇
无线电   586篇
一般工业技术   1414篇
冶金工业   1289篇
原子能技术   258篇
自动化技术   1086篇
  2024年   140篇
  2023年   503篇
  2022年   965篇
  2021年   1350篇
  2020年   1036篇
  2019年   961篇
  2018年   970篇
  2017年   1035篇
  2016年   1058篇
  2015年   972篇
  2014年   1315篇
  2013年   1715篇
  2012年   1773篇
  2011年   1954篇
  2010年   1348篇
  2009年   1272篇
  2008年   1109篇
  2007年   1400篇
  2006年   1119篇
  2005年   827篇
  2004年   691篇
  2003年   621篇
  2002年   501篇
  2001年   407篇
  2000年   336篇
  1999年   256篇
  1998年   198篇
  1997年   182篇
  1996年   161篇
  1995年   145篇
  1994年   137篇
  1993年   117篇
  1992年   104篇
  1991年   72篇
  1990年   75篇
  1989年   54篇
  1988年   47篇
  1987年   33篇
  1986年   39篇
  1985年   27篇
  1984年   23篇
  1983年   14篇
  1982年   12篇
  1980年   21篇
  1964年   8篇
  1961年   8篇
  1959年   11篇
  1958年   7篇
  1956年   8篇
  1955年   8篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
121.
The influence of two factors, total concentration and fraction of three pairs of commercial enzymes, which showed statistical significance (Biocellulase W with Hitempase 2XL, Biocellulase W with Amylo 300 and Amylo 300 with Hitempase 2XL), were studied for their overall effect on buckwheat wort quality using response surface methodology (RSM). This study revealed that the addition of increasing levels of Hitempase 2XL to the buckwheat mash increased colour, extract levels, wort filtration, fermentability and total fermentable extract (TFE), along with decreasing viscosity values. Results also determined a high level of fermentability when an enzyme combination of 30% Biocellulase and 70% Hitempase was added to the mash. The addition of increasing levels of Amylo 300 to buckwheat mashes resulted in increases in fermentability and total fermentable extract (TFE), along with increases in total soluble nitrogen (TSN), free amino nitrogen (FAN) and Kolbach index (KI). With regard to the proposed optimal regime, although no synergistic effect was found when the three enzymes were used together, the optimum conditions for the production of buckwheat wort with lowest viscosity, highest extract and optimal fermentability were achieved using a joint model. Overall, the findings of this study demonstrate the feasibility of producing wort suitable for the brewing of gluten‐free beer from 100% malted buckwheat with careful optimisation of enzyme types and dosage levels.  相似文献   
122.
Anacardic acids, 6-pentadec(en)ylsalicylic acids isolated from the cashew Anacardium occidentale L. (Anacardiaceae) nut and apple, were found to possess preventive antioxidant activity while salicylic acid did not show this activity. These anacardic acids prevent generation of superoxide radicals by inhibiting xanthine oxidase (EC 1.1.3.22, Grade IV) without radical-scavenging activity. Notably, the inhibition kinetics of anacardic acids do not follow hyperbolic dependence of enzyme inhibition on inhibitor contents (Michaelis–Menten equation) but follow the Hill equation instead. Anacardic acid (C15:1) inhibited the soybean lipoxygenase-1 (EC 1.13.11.12, Type 1) catalyzed oxidation of linoleic acid with an IC50 of 6.8 μM. The inhibition is a slow and reversible reaction without residual enzyme activity. The inhibition kinetics indicate that anacardic acid (C15:1) is a competitive inhibitor and the inhibition constant, KI, was 2.8 μM. Anacardic acids act as antioxidants in a variety ways, including inhibition of various prooxidant enzymes involved in the production of the reactive oxygen species and chelate divalent metal ions such as Fe2+ or Cu2+, but do not quench reactive oxygen species. The C15-alkenyl side chain is largely associated with the activity.  相似文献   
123.
高沸石配比陶瓷纤维复合纸制备中助留剂的选择   总被引:1,自引:0,他引:1  
考察了沸石复合纸板制备中助留剂对无机物留着的影响。结果表明,PDADMAC或A-PAM单元体系、PVAm/A-PAM二元助留体系的作用效果差,PDADMAC/A-PAM二元助留体系的留着效果显著,PDADMAC的相对分子质量对留着效果的影响不大,PDADMAC与A-PAM的电荷量比是决定无机物留着的主要因素,本研究的条件下,最佳正负电荷量比为3.0~5.0。  相似文献   
124.
125.
126.
Solubility of dimethyl-2,6-naphthalene dicarboxylate in acetic acid, N,N-dimethylfonnamide, N,N-dimethyl acetamide, dimethyl sulphoxide, and N-methyl-2-ketopyrrolidine were determined using a dynamic method. The measured systems were correlated by UNIFAC group contribution method. A new main group (aromatic ester, ACCOO) was defined to express the activity coefficients of the aromatic ester. New interaction parameters of the ACCOO group were expressed as the first-order function of temperature and were determined from the experimental data. The calculated results for the new interaction parameters were satisfactory. The measured systems were also correlated with the Wilson and 2-h models, and the results were compared with those of the UNIFAC model.  相似文献   
127.
丁辛醇装置丁醛加氢催化剂在装置扩能投产以后热点上移 (失活 )的速率较快 ,针对催化剂老化的原因进行分析、判断 ,找出原因 ,采用相应的解决措施 ,可延长催化剂使用寿命 ,增加装置效益  相似文献   
128.
Hypnosis has been demonstrated to reduce analogue pain, and studies on the mechanisms of laboratory pain reduction have provided useful applications to clinical populations. Studies showing central nervous system activity during hypnotic procedures offer preliminary information concerning possible physiological mechanisms of hypnotic analgesia. Randomized controlled studies with clinical populations indicate that hypnosis has a reliable and significant impact on acute procedural pain and chronic pain conditions, Methodological issues of this body of research are discussed, as are methods to better integrate hypnosis into comprehensive pain treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
129.
介绍了JT-1G/JT-4加氢精制催化剂的烯烃饱和功能和有机硫转化功能;阐述了该催化剂在中石油辽河石化分公司、浙江工程设计院共同开发的用于焦化富气制氢原料的烯烃饱和及有机硫转化的新加氢工艺——逆流-等温-绝热加氢精制工艺中的使用情况。原料中体积分数13%~16%的烯烃经过加氢精制后降至0;原料中有机硫得到充分转化;焦化富气经过加氢精制后,满足了作为制氢原料的要求,降低了制氢成本。  相似文献   
130.
We describe the design and operation of a new high-pressure metal ebulliometer which can operate at pressures to at least 3 MPa in the range 220–400 K. Infinite-dilution activity coefficients are presented for the system CHF2Cl + CF3-CH, at 275 K and for the system CF3-CH2F + CH2F2, at 260, 230, and 300 K. The Wilson activity coellicient model and a virial coefficient model are applied to these systems, and the phase equilibrium conditions are calculated. The results are shown to agree well with predicted and with published measured values. The excess enthalpy is calculated and compared with results from a Peng Robinson equation of state. Vapor densities on the dew curves are given.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号