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   1659篇
  免费   92篇
  国内免费   9篇
电工技术   24篇
综合类   3篇
化学工业   368篇
金属工艺   33篇
机械仪表   74篇
建筑科学   26篇
能源动力   130篇
轻工业   160篇
水利工程   13篇
石油天然气   9篇
无线电   216篇
一般工业技术   333篇
冶金工业   73篇
原子能技术   7篇
自动化技术   291篇
  2024年   6篇
  2023年   43篇
  2022年   91篇
  2021年   141篇
  2020年   106篇
  2019年   108篇
  2018年   134篇
  2017年   93篇
  2016年   88篇
  2015年   58篇
  2014年   90篇
  2013年   132篇
  2012年   76篇
  2011年   96篇
  2010年   69篇
  2009年   55篇
  2008年   50篇
  2007年   44篇
  2006年   38篇
  2005年   28篇
  2004年   13篇
  2003年   17篇
  2002年   7篇
  2001年   12篇
  2000年   10篇
  1999年   6篇
  1998年   25篇
  1997年   14篇
  1996年   9篇
  1995年   14篇
  1994年   13篇
  1993年   5篇
  1992年   3篇
  1991年   3篇
  1990年   5篇
  1989年   7篇
  1988年   3篇
  1987年   6篇
  1986年   3篇
  1985年   6篇
  1984年   6篇
  1983年   3篇
  1982年   2篇
  1981年   7篇
  1980年   2篇
  1979年   5篇
  1978年   2篇
  1975年   2篇
  1974年   2篇
  1972年   1篇
排序方式: 共有1760条查询结果,搜索用时 15 毫秒
991.
992.
Visual inspection for the quantification of malaria parasitaemiain (MP) and classification of life cycle stage are hard and time taking. Even though, automated techniques for the quantification of MP and their classification are reported in the literature. However, either reported techniques are imperfect or cannot deal with special issues such as anemia and hemoglobinopathies due to clumps of red blood cells (RBCs). The focus of the current work is to examine the thin blood smear microscopic images stained with Giemsa by digital image processing techniques, grading MP on independent factors (RBCs morphology) and classification of its life cycle stage. For the classification of the life cycle of malaria parasite the k‐nearest neighbor, Naïve Bayes and multi‐class support vector machine are employed for classification based on histograms of oriented gradients and local binary pattern features. The proposed methodology is based on inductive technique, segment malaria parasites through the adaptive machine learning techniques. The quantification accuracy of RBCs is enhanced; RBCs clumps are split by analysis of concavity regions for focal points. Further, classification of infected and non‐infected RBCs has been made to grade MP precisely. The training and testing of the proposed approach on benchmark dataset with respect to ground truth data, yield 96.75% MP sensitivity and 94.59% specificity. Additionally, the proposed approach addresses the process with independent factors (RBCs morphology). Finally, it is an economical solution for MP grading in immense testing .  相似文献   
993.
Palyno‐anatomical study of monocots taxa using Light and Scanning Electron Microscopy (SEM) was first time conducted with a view to evaluating their taxonomic significance. Studied plants were collected from different eco‐climatic zones of Pakistan ranges from tropical, sub‐tropical, and moist habitats. The aim of this study is to use palyno‐anatomical features for the correct identification, systematic comparison, and investigation to elucidate the taxonomic significance of these features, which are useful to taxonomists for identifying monocot taxa. A signification variation was observed in quantitative and qualitative characters by using the standard protocol of light microscopy (LM) and SEM. Epidermal cell length varied from maximum in Allium griffthianum (480 ± 35.9) μm at the adaxial surface to minimum in Canna indica (33.6 ± 8.53) μm on abaxial surface. Maximum exine thickness was observed in Canna indica (4.46) μm and minimum in Allium grifthianum (0.8) μm. Variation was observed in shape and exine ornamentation of the pollen, shape of the epidermal cell, number, size, and type of stomata, guard cell shape, and anticlinal wall pattern. Based on these palyno‐anatomical features a taxonomic key was developed, which help in the discrimination of studied taxa. In conclusion, LM and SEM pollen and epidermal morphology is explanatory, significant, and can be of special interest for the plant taxonomist in the correct identification of monocots taxa.  相似文献   
994.
A primitive element for the development of sustainable pyrolysis processes is the study of thermal degradation kinetics of lignocellulosic waste materials for optimal energy conversion. The study presented here was conducted to predict and compare the optimal kinetic parameters for pyrolysis of various lignocellulosic biomass such as wood sawdust, bagasse, rice husk, etc., under both isothermal and non-isothermal conditions. The pyrolysis was simulated over the temperature range of 500–2400 K for isothermal process and for heating rate range of 25–165 K/s under non-isothermal conditions to assess the maximum pyrolysis rate of virgin biomass in both cases. Results revealed that by increasing the temperature, the pyrolysis rate was enhanced. However, after a certain higher temperature, the pyrolysis rate was diminished which could be due to the destruction of the active sites of char. Conversely, a decrease in the optimum pyrolysis rate was noted with increasing reaction order of the virgin biomass. Although each lignocellulosic material attained its maximum pyrolysis rate at the optimum conditions of 1071 K and 31 K/s for isothermal and non-isothermal conditions, respectively, but under these conditions, only wood sawdust exhibited complete thermal utilization and achieved final concentrations of 0.000154 and 0.001238 under non-isothermal and isothermal conditions, respectively.  相似文献   
995.
In any Distributed Denial of Service (DDoS) attack, invaders may use incorrect or spoofed Internet Protocol (IP) addresses in the attacking packets and thus disguise the actual origin of the attacks. This is primarily due to the stateless nature of the Internet. IP traceback algorithms provide mechanisms for identifying the true source of an IP datagram on the Internet ensuring at least the accountability of cyber attacks. While many IP traceback techniques have been proposed, most of the previous studies focus and offer solutions for DDoS attacks done on Internet Protocol version 4 (IPv4) environment. IPv4 and IPv6 networks differ greatly from each other, which urge the need of traceback techniques specifically tailored for IPv6 networks. In this paper, we propose a novel traceback architecture for IPv6 networks using Common Open-Policy Service and a novel packet-marking scheme. We also provide complete underlying protocol details required for traceback support in IPv6 networks. The proposed architecture is on demand and only single packet is required to traceback the attack.  相似文献   
996.
The effect of processing temperature on structural changes in wheat, corn, and high amylose corn starch granules was investigated and related to the mechanical properties of gels and microcellular foam (MCF). Scanning electron micrographs (SEM) showed that wheat starch granules form ghosts with thicker walls than dent corn granules. The granule wall was permeable to water and appeared to be at least partially permeable to the solubilized contents of the granule. The ghost walls became visibly porous after heating at 95ºC for 60 min and were completely solubilized by heating to 120ºC. High‐amylose corn starch (HACS) granules were completely dissolved by heating to 140ºC. Gels made with wheat starch had higher gel strength and dynamic modulus compared to dent corn starch gels. The density, compressive strength and modulus of MCF were lower in samples cooked for 60 min. The density of dent corn MCF was higher than that of wheat starch which may have accounted for higher compressive strength and modulus in the corn sample. MCF made from HACS had higher surface area and lower density, compressive strength, and modulus than the other starches tested. There were no significant differences in pore volume or surface area due to extended cooking times.  相似文献   
997.
Chemical composition, antioxidant and antimicrobial activities of the essential oils from aerial parts of basil (Ocimum basilicum L.) as affected by four seasonal, namely summer, autumn, winter and spring growing variation were investigated. The hydro-distilled essential oils content ranged from 0.5% to 0.8%, the maximum amounts were observed in winter while minimum in summer. The essential oils consisted of linalool as the most abundant component (56.7–60.6%), followed by epi-α-cadinol (8.6–11.4%), α-bergamotene (7.4–9.2%) and γ-cadinene (3.2–5.4%). Samples collected in winter were found to be richer in oxygenated monoterpenes (68.9%), while those of summer were higher in sesquiterpene hydrocarbons (24.3%). The contents of most of the chemical constituents varied significantly (p < 0.05) with different seasons. The essential oils investigated, exhibited good antioxidant activity as measurements by DPPH free radical-scavenging ability, bleaching β-carotene in linoleic acid system and inhibition of linoleic acid oxidation. Evaluation of antimicrobial activity of the essential oils and linalool, the most abundant component, against bacterial strains: Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pasteurella multocida and pathogenic fungi Aspergillus niger, Mucor mucedo, Fusarium solani, Botryodiplodia theobromae, Rhizopus solani was assessed by disc diffusion method and measurement of determination of minimum inhibitory concentration. The results of antimicrobial assays indicated that all the tested microorganisms were affected. Both the antioxidant and antimicrobial activities of the oils varied significantly (p < 0.05), as seasons changed.  相似文献   
998.
Comments on the original article, "Intersectionality and research in psychology," by E. R. Cole (see record 2009-04471-001). Cole’s article, says the current author, makes a welcome and valuable contribution to the field of psychology. Particularly useful are the three questions that she posed, highlighting how these questions are relevant and pressing for all researchers, not just those focused on work with subordinated groups. However, there are two additional points that the current author believes need to be addressed as intersectionality moves from the margins of psychology to the mainstream. First, although Cole (2009) nicely traced the history of intersectionality, from feminists of color and critical race theorists to psychology, what the current author found lacking was a discussion about the implications of translating the theory across disciplines. The current author's second point is a methodological one and is related to the disciplinary origins of intersectionality. The current author was surprised to see Cole (2009) discuss at length the role of statistical interactions in intersectionality research. While the current author fully appreciates that Cole may have been attempting to “speak the language” of the vast majority of psychologists, a crucial point about intersectionality research was lost: that qualitative research is central to this approach. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
999.
The purpose in this longitudinal study was to investigate further the link between ethnic identity processes and content through an examination of emerging adults’ narratives of ethnicity-related experiences. Seventy ethnically diverse college students completed an ethnic identity exploration index and told an ethnicity-related narrative on 2 occasions 18 months apart. Results indicated that (a) participants who increased in exploration over time were more likely to change their narrative theme than participants who decreased or remained stable in exploration and (b) these changes were more likely to be to stories of experience of prejudice or connection to culture. This study highlights the costs and benefits of ethnic identity and provides evidence for a linkage between ethnic identity process and content in emerging adulthood. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
1000.
Increasing environmental awareness has persuaded some of the major Asian countries to reassess the feasibility of natural colorants. As one of the most agriculturally rich regions of the world, the emphasis has been on finding new colour sources which have the potential to yield high quality dyes. Syed Ishrat Ali argues that a detailed programme of R & D into the capabilities of natural dyes is of vital importance.  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