全文获取类型
收费全文 | 101053篇 |
免费 | 4736篇 |
国内免费 | 4746篇 |
专业分类
电工技术 | 4619篇 |
技术理论 | 5篇 |
综合类 | 9784篇 |
化学工业 | 14808篇 |
金属工艺 | 6124篇 |
机械仪表 | 3501篇 |
建筑科学 | 5424篇 |
矿业工程 | 2071篇 |
能源动力 | 3091篇 |
轻工业 | 6627篇 |
水利工程 | 2436篇 |
石油天然气 | 4617篇 |
武器工业 | 762篇 |
无线电 | 7915篇 |
一般工业技术 | 14987篇 |
冶金工业 | 3271篇 |
原子能技术 | 2607篇 |
自动化技术 | 17886篇 |
出版年
2024年 | 64篇 |
2023年 | 344篇 |
2022年 | 533篇 |
2021年 | 733篇 |
2020年 | 1233篇 |
2019年 | 1173篇 |
2018年 | 1172篇 |
2017年 | 1208篇 |
2016年 | 1718篇 |
2015年 | 2384篇 |
2014年 | 4359篇 |
2013年 | 5218篇 |
2012年 | 4686篇 |
2011年 | 5420篇 |
2010年 | 4468篇 |
2009年 | 5855篇 |
2008年 | 5906篇 |
2007年 | 6487篇 |
2006年 | 6039篇 |
2005年 | 5058篇 |
2004年 | 4408篇 |
2003年 | 4284篇 |
2002年 | 4267篇 |
2001年 | 3233篇 |
2000年 | 3576篇 |
1999年 | 3285篇 |
1998年 | 2733篇 |
1997年 | 2590篇 |
1996年 | 2706篇 |
1995年 | 2826篇 |
1994年 | 2556篇 |
1993年 | 1577篇 |
1992年 | 1603篇 |
1991年 | 1124篇 |
1990年 | 827篇 |
1989年 | 722篇 |
1988年 | 676篇 |
1987年 | 402篇 |
1986年 | 247篇 |
1985年 | 390篇 |
1984年 | 435篇 |
1983年 | 436篇 |
1982年 | 354篇 |
1981年 | 409篇 |
1980年 | 275篇 |
1979年 | 119篇 |
1978年 | 113篇 |
1977年 | 71篇 |
1976年 | 45篇 |
1975年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
1.
目的 了解近年来传统纺织服饰图案的研究动态及发展趋势,归纳学术研究成果并进行评价,总结研究传统服饰图案的意义和对现代设计的启示。方法 基于史论视角、社会文化视角、工艺美术视角和设计艺术视角梳理相关文献,结合现有研究分析中国传统服饰图案的资料来源及其特色、传统服饰图案的研究热点、新时代传统服饰图案的生存策略及中国传统服饰图案创新设计的应用领域。结果指出传统服饰图案的研究史料取材丰富、研究类型呈现多元;当前传统服饰图案的传承与创新体现了数字化发展、美育引导、政策支持的特点;传统服饰图案在服装设计、公共空间、文创产品中大放异彩。结论 中国传统纺织服饰图案研究多点开花,但缺乏系统整体的“中国传统纺织服饰图案知识谱系”用于指导相关研究和实践,对中国传统纺织服饰图案的研究多处于实证分析的层面且欠缺深入独到的理论,通过综述与价值阐述,提出研究的不足之处,纵深学术研究,同时为中国传统纺织服饰图案的现代设计提供新思路。 相似文献
2.
《Ceramics International》2022,48(24):36802-36813
X-type samarium-cadmium co-substituted hexaferrite with compositions Ba2-xSmxCo2CdyFe28-yO46 (0.00 ≤ x ≤ 0.08, and 0 ≤ y ≤ 0.4) were prepared at 1340 °C using a simple heat treatment technique. All heated samples were characterized using FTIR, XRD, SEM, VSM, M?ssbauer, and low-frequency dielectric measurements. XRD analysis of prepared samples shows the formation of X as a major phase along with hematite. The MS value varied from 67.01 Am2/kg to 50.43 Am2/kg; whereas the Hc value changed from 2.95 kA/m to 6.17 kA/m, A high value of MS (67.01 Am2/kg) is observed in the pure sample, and a very low value of Hc (2.95 kA/m) is observed for x = 0.06, y = 0.3 compositions, but Mr/Ms < 0.5 confirm the multi-domain nature of prepared hexaferrites. Hysteresis loops of all samples are narrow, and confirmed that formed samples belong to magnetically soft. Mössbauer spectra of the three samples (S1, S3, and S5) show the existence of doublets. Significantly low values of coercivity, retentivity, and loss tangent in Sm–Cd substituted samples signified those prepared materials can be used to design electromagnets, transformer cores, electric motors, and maybe a potential candidate for lossless low-frequency applications. 相似文献
3.
4.
《Ceramics International》2022,48(3):3544-3553
In this study the effects of thermal shock on the impact damage resistance, damage tolerance and flexural strength of Nextel 610/alumina silicate ceramic matrix composites were experimentally evaluated. Composite laminates with balanced and symmetric layup were gradually heated to 1200°C in an air-based furnace and held for at least 30 min before being removed and immersed in water at room temperature. The laminates were then subjected to low velocity impacts via a hemispherical steel impactor. The resultant damage was characterized non-destructively, following which the laminates were subjected to compression tests. Three-point bend tests were also performed to evaluate the effect of thermal shock on the flexural strength and related failure modes of the laminates. Thermally shocked laminates showed smaller internal damage and larger external damage areas in comparison to their pristine counterparts. For the impact energy and resultant damage size considered, the residual compressive strengths for the thermally shocked and pristine laminates were similar. 相似文献
5.
In Vivo Simultaneous Analysis of Gene Expression by Dual-Color Luciferases in Caenorhabditis elegans
Both fluorescent and luminescent observation are widely used to examine real-time gene expression patterns in living organisms. Several fluuorescent and luminescent proteins with specific optical properties have been developed and applied for simultaneous, multi-color observation of more than two gene expression profiles. Compared to fluorescent proteins, however, the application of multi-color luminescent imaging in living organisms is still limited. In this study, we introduced two-color luciferases into the soil nematode C. elegans and performed simultaneous analysis of two gene expression profiles. Using a green-emitting luciferase Eluc (emerald luciferase) and red-emitting luciferase SLR (stable luciferase red), the expression patterns of two genes were simultaneously observed in single animals from embryonic to adult stages over its whole life span. In addition, dual gene activities were observed at the single embryo level, with the simultaneous observation of morphological changes. These are the first application of a two-color luciferase system into a whole animal and suggest that precise relationship of expression patterns of multiple genes of interest can be analyzed over the whole life of the animal, dependent on the changes in genetic and/or environmental conditions. 相似文献
6.
7.
《Ceramics International》2022,48(14):20134-20145
M-type calcium hexaferrite- CaFe12O19 (CaM) has been prepared in presence of Azadirachta indica, and Murraya koenigii leaves extracts, followed by calcination at 650 °C for 3h. It was observed that the presence of phytochemicals in both leaves extract plays a vital role in deciding the structural, optical, microstructural, magnetic, and dielectric properties of prepared CaM hexaferrites. Prepared samples were characterized using FT-IR, XRD, UV–Vis, SEM, VSM, and dielectric measurements. FTIR, UV– Vis, and antioxidant assay confirmed the presence of phenolic content and antioxidant property of plant extract. This further resulted in the formation of a pure hexagonal phase as revealed by the XRD analysis. The surface morphology of prepared ferrites modified through this greener route was illustrated by the spongy appearance of ferrites in SEM micrographs.The saturation magnetization for the CaM powder prepared using Murraya koenigii leaves extract is 11.78 Am2/kg, while that prepared from Azadirachta indica leaves extract is 3.56 Am2/kg. Both samples show a magnetically soft nature, with a multidomain structure. The energy bandgap was also observed to be 2.01 eV. Moreover, the calcium ferrite synthesized by Murraya koenigii leaves had ε’max ~ 25 and that synthesized in presence of Azadirachta indica leaves had ε’max ~ 200 at ~20 Hz. 相似文献
8.
Weronika Gonciarz ukasz Lechowicz Mariusz Urbaniak Wiesaw Kaca Magdalena Chmiela 《International journal of molecular sciences》2021,22(1)
Infections due to Gram-negative bacteria Helicobacter pylori may result in humans having gastritis, gastric or duodenal ulcer, and even gastric cancer. Investigation of quantitative changes of soluble biomarkers, correlating with H. pylori infection, is a promising tool for monitoring the course of infection and inflammatory response. The aim of this study was to determine, using an experimental model of H. pylori infection in guinea pigs, the specific characteristics of infrared spectra (IR) of sera from H. pylori infected (40) vs. uninfected (20) guinea pigs. The H. pylori status was confirmed by histological, molecular, and serological examination. The IR spectra were measured using a Fourier-transform (FT)-IR spectrometer Spectrum 400 (PerkinElmer) within the range of wavenumbers 3000–750 cm−1 and converted to first derivative spectra. Ten wavenumbers correlated with H. pylori infection, based on the chi-square test, were selected for a K-nearest neighbors (k-NN) algorithm. The wavenumbers correlating with infection were identified in the W2 and W3 windows associated mainly with proteins and in the W4 window related to nucleic acids and hydrocarbons. The k-NN for detection of H. pylori infection has been developed based on chemometric data. Using this model, animals were classified as infected with H. pylori with 100% specificity and 97% sensitivity. To summarize, the IR spectroscopy and k-NN algorithm are useful for monitoring experimental H. pylori infection and related inflammatory response in guinea pig model and may be considered for application in humans. 相似文献
9.
Saerom Lee Ga-Eun Lim Yong-Nyun Kim Hyeon-Sook Koo Jaegal Shim 《International journal of molecular sciences》2021,22(4)
The extracellular matrix (ECM) is important for normal development and disease states, including inflammation and fibrosis. To understand the complex regulation of ECM, we performed a suppressor screening using Caenorhabditis elegans expressing the mutant ROL-6 collagen protein. One cuticle mutant has a mutation in dpy-23 that encodes the μ2 adaptin (AP2M1) of clathrin-associated protein complex II (AP-2). The subsequent suppressor screening for dpy-23 revealed the lon-2 mutation. LON-2 functions to regulate body size through negative regulation of the tumor growth factor-beta (TGF-β) signaling pathway responsible for ECM production. RNA-seq analysis showed a dominant change in the expression of collagen genes and cuticle components. We noted an increase in the cav-1 gene encoding caveolin-1, which functions in clathrin-independent endocytosis. By knockdown of cav-1, the reduced TGF-β signal was significantly restored in the dpy-23 mutant. In conclusion, the dpy-23 mutation upregulated cav-1 expression in the hypodermis, and increased CAV-1 resulted in a decrease of TβRI. Finally, the reduction of collagen expression including rol-6 by the reduced TGF-β signal influenced the cuticle formation of the dpy-23 mutant. These findings could help us to understand the complex process of ECM regulation in organism development and disease conditions. 相似文献
10.
《Ceramics International》2021,47(24):34695-34703
Li4x/3Zn2–2xTi1+2x/3O4 microwave dielectric ceramics with a spinel phase were prepared via a high-temperature solid-phase method. P–V–L theory, vibration spectra, and XPS were utilized to establish the links between the intrinsic and extrinsic factors and the microwave dielectric properties. According to the characterization, the change in permittivity (εr) was ascribed to the increase in the average bond ionicity of Ti–O(AfiTi-O) and the polar mode of the lattice vibration; the change in quality factor(Q × f) resulted from the change in the Ti–O lattice energy (AUTi-O) and existence of oxygen vacancy; the increase in temperature coefficient of the resonance frequency (τf) was triggered by the increase in the Ti–O bond energy. The Li0.6Zn1.1Ti1.3O4 ceramics (x = 0.45) sintered at 1125 °C finally obtained optimal microwave dielectric constants of εr = 17.3, Q × f = 76,318 GHz and τf = -58 ppm/°C. 相似文献