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   3070篇
  免费   98篇
  国内免费   18篇
电工技术   55篇
综合类   16篇
化学工业   678篇
金属工艺   46篇
机械仪表   78篇
建筑科学   45篇
矿业工程   3篇
能源动力   143篇
轻工业   282篇
水利工程   19篇
石油天然气   14篇
无线电   320篇
一般工业技术   608篇
冶金工业   466篇
原子能技术   25篇
自动化技术   388篇
  2023年   31篇
  2022年   67篇
  2021年   116篇
  2020年   78篇
  2019年   79篇
  2018年   95篇
  2017年   82篇
  2016年   98篇
  2015年   52篇
  2014年   97篇
  2013年   169篇
  2012年   130篇
  2011年   160篇
  2010年   119篇
  2009年   101篇
  2008年   122篇
  2007年   117篇
  2006年   95篇
  2005年   90篇
  2004年   63篇
  2003年   58篇
  2002年   48篇
  2001年   29篇
  2000年   42篇
  1999年   40篇
  1998年   162篇
  1997年   104篇
  1996年   89篇
  1995年   57篇
  1994年   63篇
  1993年   55篇
  1992年   38篇
  1991年   33篇
  1990年   23篇
  1989年   25篇
  1988年   25篇
  1987年   16篇
  1986年   21篇
  1985年   26篇
  1984年   32篇
  1983年   14篇
  1982年   20篇
  1981年   19篇
  1980年   19篇
  1978年   18篇
  1977年   17篇
  1976年   31篇
  1975年   15篇
  1974年   20篇
  1972年   13篇
排序方式: 共有3186条查询结果,搜索用时 0 毫秒
71.
ABSTRACT:  Lactobacillus acidophilus 4461, L. acidophilus 4962, L. casei 290, and L. casei 2607 were used to hydrolyze isoflavone glycosides (IG) to biologically active forms—isoflavone aglycones (IA)—in soymilk (SM) prepared from soy protein isolate (SPI) and soymilk supplemented with 0.5% (w/v) of lactulose (SML). L. acidophilus 4461 utilized the highest level of lactulose (3.01 mg/mL) and L. acidophilus 4962 utilized the least (0.86 mg/mL) at 24 h of incubation. The pH values decreased to 4.00 to 5.00 in SML, while they remained relatively high (6.15 to 6.36) in SM. Supplementation with lactulose significantly ( P < 0.05) enhanced the viable counts of all the 4 Lactobacillus strains. At the end of incubation, the viable counts of Lactobacillus ranged from 8.08 to 8.25 log CFU/mL in SML compared to 6.99 to 7.11 log CFU/mL in SM. Supplementation with lactulose increased the biotransformation of IG to IA after 6 h of incubation. The presence of lactulose in the medium enhanced the biotransformation level of IG to IA by Lactobacillus up to 21.9%. The hydrolysis level of malonyl genistin and acetyl genistin in SML was much higher than in SM by all the 4 probiotic organisms. The biotransformation of IG to IA occurred rapidly during the 1st 12 h of incubation in both SML and SM. Among the 4 Lactobacillus strains, L. acidophilus 4461 biotransformed the highest level (88.8%) of IG to IA in SML compared to 68.2% in SM after 24 h of incubation.  相似文献   
72.
This study was conducted to investigate the changes in lipids and their effect on the taste of migaki-nishin during drying. Lipid was extracted from herring fillets following different drying stages to measure the degree of lipid oxidation and changes in lipid composition, and fatty acid profile. Peroxide value, carbonyl value and acid value of the lipids were significantly increased (P < 0.05) during the drying period. Marked increase in free fatty acids, with decreases in triglyceride and phospholipid content were observed in proportion to drying time and this result suggested that hydrolysis was induced by lipases and phospholipases. The decreases in polyunsaturated fatty acids (PUFAs), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), were observed in the total lipids and phospholipid fraction. In addition, significant increase in PUFAs especially DHA was found in the free fatty acid fraction. Sensory evaluation showed that an addition of DHA to mentsuyu significantly (P < 0.05) enhances the intensities of thickness, mouthfulness and continuity. These results suggest that during drying period lipid oxidation was not only occurred but also lipolysis predominantly released DHA, which might have a contribution to kokumi enhancement of migaki-nishin.  相似文献   
73.
Computer colour matching of paints is based on the determination of the Kubelka—Munk absorption (K) and scattering coefficients (S) of pigments. K and S are sensitive to particle size in the range of sizes employed in paint technology. The K—M theory does not provide any guidelines for the correction of the values of K and S with a change in particle size. On the other hand the Mie theory linear scattering coefficient can be calculated from a knowledge of size and refractive index of the pigment. A number of relations correlating the K—M scattering coefficient and the linear scattering coefficient have been proposed in the literature. Attempts are made to estimate the K—M scattering coefficient using a relation suggested by Mudgett and Richards and to make a comparison with experimental values. The Mie theory equations being complex, simplified equations applicable to pigment sizes for the calculation of Mie theory parameters are proposed. The viability of the simplified equations has been established by comparing the results with those obtained using the full Mie equations.The K—M scattering coefficient for titanium dioxide pigments has been determined from reflectance measurements. The particle size of titanium dioxide has been determined by a light scattering method. The K—M scattering coefficient calculated from the linear scattering coefficient obtained using the simplified expressions agrees with experimental results. This suggests a method for the correction of the values of K and S with changes in pigment particle size.  相似文献   
74.
Breast cancer is one of the most common types of cancer among women globally. It is caused by mutations in the estrogen/progesterone receptors and conventional treatment methods are commonly utilized. About 70–80 percent of individuals with the early-stage non-metastatic disease may be cured. Conventional treatment is far less than the optimal ratio, as demonstrated through the high mortality rate of women with this cancer. However, conventional treatment methods like surgery, radiotherapy, and chemotherapy are not as effective as expected and lead to concerns about low bioavailability, low cellular uptake, emerging resistance, and adverse toxicities. A nanomedicine-based approach is a promising alternative for breast cancer treatment. The present era is witnessing rapid advancements in nanomedicine as a platform for investigating novel therapeutic applications and modern intelligent healthcare management strategies. This paper focuses on nanomedicine-based therapeutic interventions that are becoming more widely accepted for improving treatment effectiveness and reducing undesired side effects in breast cancer patients. By evaluating the state-of-the-art tools and taking the challenges involved into consideration, various aspects of the proposed nano-enabled therapeutic approaches have been discussed in this review.  相似文献   
75.
We present systematic measurements of CPM on two independent series of slightly phosphorous and boron doped films. For “n-type” samples of both series, the CPM deep defect absorption is proportional to the square root of the gas dopant ratio. For these samples we discuss the influence of Fermi level on the CPM spectra. For slightly “p-type” samples, CPM deep defect absorption as evaluated by CPM becomes higher than the corresponding PDS-values. This fundamental problem can be traced back to the violation of two basic conditions necessary for a correct evaluation of the absorption from CPM measurements: (1) the power law exponent γ (Rose factor) of the photoconductivity must be spectrally independent, and (2) the generation rate G, which corresponds to the CPM photocurrent, also has to be spectrally independent. Further, we compare the annealed and the “saturated” light soaked states of selected slightly doped samples and an undoped sample: the variations in the CPM deep defect absorption and in photoconductivity due to light-soaking are discussed.  相似文献   
76.
3D Numerical study of temperature variation for subsonic rarefied gas flow in a microchannel is carried out using an in-house MPI-based parallelized DSMC code. The temperature drop in the microchannel decreases with an increase in the aspect ratio whereas it increases with an increase in the pressure ratio, the cross-aspect ratio (CAR), and the Knudsen number. 3D and 2D simulations results are compared and effect of the CAR and Knudsen number are brought out. Finally, a correlation that predicts the temperature drop is formulated along with a list of conditions that ensures a near isothermal flow.  相似文献   
77.
Magnetic induction applications mostly rely on resonance for inducing maximum magnetic fields to system loads and hence for each resonant frequency dedicated circuits are required. Unfortunately, the frequency responses of such inductive systems manifest several peaks (frequency splitting) when their coupling coefficients are equal to or larger than critical coupling. Such frequency responses with several peaks are detrimental when the objective is to transfer maximum energy. Frequency splitting between inductive coils have been seen to date as detrimental to wireless power transfer and inductive communication systems. In this paper it is demonstrated that frequency splitting is a welcome phenomenon with advantage in the design of inductive filter banks and multi-frequency inductive systems. The centre frequencies of the filter banks result from split bands of inductive systems. This phenomenon is applied in conjunction with an innovative recursive algorithm to design inductive filter banks. The filters straddle both sides of the resonant frequency position and can be resolved individually.  相似文献   
78.
The Journal of Supercomputing - In the current era of the Internet of Things (IoT), massive number of sensors are used in our daily lives. Sensors are everywhere around us. They exist in our homes,...  相似文献   
79.
正在印度文化中,钻石在3000年的时间长河里占据着稀罕珍贵又非凡的地位。作为一种象征着勇气和生命力的法宝,钻石深受皇宫贵族的喜爱而常常被佩戴于身上。爱美钻石集团成立于半世纪以前。多年来,秉持创业之初对于钻石的热爱,爱美钻石集团成为专门为行业内高端珠宝品牌公司提供美钻的供应商,并享誉全球。得益于我们多年来对于钻石制造工艺的精益求精,如今我们终于有能力推出一款拥有完美切工  相似文献   
80.
Electrocatalytical conversion of CO2 into various chemicals like hydrocarbons and CO is regarded as a promising approach to mitigate carbon emission and, meanwhile, to provide sustainable energy and value-added chemicals. Two different reactors are used in this work. One is based upon the two-electrode configuration powered by a DC power supply or Si solar cell, which is suitable for practical applications. Another is three-electrode one powered by a potentiostat, which is feasible to study the electrode performance. Polycrystalline Cu electrode is used as the cathode, and hematite is the anode. Performance of CO2 reduction using the two- and three-electrode configurations is studied by measuring electrode potential, cell voltage, current density, Faradaic efficiency, and reduction selectivity of CO2. Cu cathode used here exhibits a low overpotential for CO2 reduction, specifically for the cell with two-electrode configuration. No obvious difference can be observed between the two types of configurations at a low bias like −0.3 and −0.4 V; while the reactor with two-electrode configuration exhibits better performance at a high bias like −0.8 V than the one with three-electrode configuration. Thus, the reactors with two-electrode configuration are desirable for practical applications, specifically considering solar cells can be used as the power source to provide green and sustainable energy.  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