全文获取类型
收费全文 | 9376篇 |
免费 | 812篇 |
国内免费 | 25篇 |
专业分类
电工技术 | 170篇 |
综合类 | 6篇 |
化学工业 | 2350篇 |
金属工艺 | 301篇 |
机械仪表 | 555篇 |
建筑科学 | 127篇 |
矿业工程 | 4篇 |
能源动力 | 455篇 |
轻工业 | 1027篇 |
水利工程 | 55篇 |
石油天然气 | 10篇 |
无线电 | 1550篇 |
一般工业技术 | 2172篇 |
冶金工业 | 463篇 |
原子能技术 | 127篇 |
自动化技术 | 841篇 |
出版年
2024年 | 14篇 |
2023年 | 121篇 |
2022年 | 207篇 |
2021年 | 316篇 |
2020年 | 208篇 |
2019年 | 294篇 |
2018年 | 319篇 |
2017年 | 321篇 |
2016年 | 418篇 |
2015年 | 338篇 |
2014年 | 487篇 |
2013年 | 627篇 |
2012年 | 704篇 |
2011年 | 835篇 |
2010年 | 559篇 |
2009年 | 549篇 |
2008年 | 501篇 |
2007年 | 429篇 |
2006年 | 386篇 |
2005年 | 273篇 |
2004年 | 300篇 |
2003年 | 236篇 |
2002年 | 266篇 |
2001年 | 233篇 |
2000年 | 184篇 |
1999年 | 176篇 |
1998年 | 242篇 |
1997年 | 128篇 |
1996年 | 101篇 |
1995年 | 67篇 |
1994年 | 56篇 |
1993年 | 56篇 |
1992年 | 45篇 |
1991年 | 30篇 |
1990年 | 22篇 |
1989年 | 29篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 11篇 |
1982年 | 6篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 7篇 |
1976年 | 12篇 |
1974年 | 3篇 |
1969年 | 3篇 |
1962年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
Byeong-Lib Ahn Ju Lee Sang-Man Park Sung-Gap Lee 《Journal of Materials Science》2008,43(10):3408-3411
Ferroelectric PZT(70/30) thick films were fabricated by the hybrid technique adding the sol-coating process to the normal
screen-printing process to obtain a good densification. The screen-printing procedure was repeated four times to form PZT(70/30)
thick films, and then PZT(30/70) precursor solution was spin-coated on the PZT thick films. All PZT thick films showed the
typical XRD patterns of a perovskite polycrystalline structure. The thickness of all thick films was approximately 75–80 μm.
The relative dielectric constant and dielectric loss of the PZT-6 thick film were 656 and 1.2%, respectively. The remanent
polarization increased and coercive field decreased with increasing the number of sol coatings and the values of the PZT-6
thick films were 28.3 μC/cm2 and 13.1 kV/cm, respectively. Leakage current density of PZT-6 thick films was 2.4 × 10−9 A/cm2 at 100 kV/cm. 相似文献
953.
Woonghwan Ryu Myung-Jin Yim Seungyoung Ahn Junho Lee Woopoung Kim Kyung-Wook Paik Joungho Kim 《Components and Packaging Technologies, IEEE Transactions on》2000,23(3):542-545
This paper firstly reports on the high-frequency SPICE model of the ACF flip-chip interconnections up to 13 GHz. The extraction process is based on an optimization procedure, called a genetic algorithm, which is known as a robust optimization tool. The proposed equivalent circuit model of the ACF interconnection can readily be used in SPICE circuit simulations for signal integrity analysis of high-frequency packages. Two different ACF interconnections were studied using the Au-coated polymer ball and Ni-filled ball. The extracted models of the two ACFs were found strongly dependent on not only size and rigidity of the conducting balls, but also on their magnetic permeability 相似文献
954.
Caspase-2 activation by formation of PIDDosome is critical for genotoxic stress induced apoptosis. PIDDosome is composed of three proteins, RAIDD, PIDD, and Caspase-2. RAIDD is an adaptor protein containing an N-terminal Caspase-Recruiting-Domain (CARD) and a C-terminal Death-Domain (DD). Its interactions with Caspase-2 and PIDD through CARD and DD respectively and formation of PIDDosome are important for the activation of Caspase-2. RAIDD DD cloned into pET26b vector was expressed in E. coli cells and purified by nickel affinity chromatography and gel filtration. Although it has been known that the most DDs are not soluble in physiological condition, RAIDD DD was soluble and interacts tightly with PIDD DD in physiological condition. The purified RAIDD DD alone has been crystallized. Crystals are trigonal and belong to space group P3121 (or its enantiomorph P3221) with unit-cell parameters a = 56.3, b = 56.3, c = 64.9 Å and γ = 120°. The crystals were obtained at room temperature and diffracted to 2.0 Å resolution. 相似文献
955.
Eun Gyo Lee Seung Hui Lee Kyung Mi Park Jung Eun Baek Sun Hee Yeon Jin‐Ki Park Won‐Kyong Chang Joon‐Ki Jung Bong Hyun Chung 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(5):643-649
BACKGROUND: Human erythropoietin (hEPO), a hydrophobic acidic glycoprotein responsible for the regulation of red blood cell production in mammals, is used for the treatment of anemia. In general, the purification of transgenic animal‐derived therapeutic proteins is not easy due to their low titer concentrations and abundant contaminant proteins. For the first time, here the purification and characterization of rhEPO from the milk of transgenic pigs are described. RESULTS: The rhEPO was purified by heparin chromatography, reverse‐phase chromatography, and gel filtration chromatography, resulting in a 16.5% yield and > 98% purity. The rhEPO purified from the milk of transgenic pigs contained less acidic isoforms and was underglycosylated in contrast to CHO‐derived rhEPO. Cell proliferation of the F‐36/EPO‐dependent cell line was proportional to the dose of transgenic pig‐derived rhEPO. CONCLUSION: Transgenic pig‐derived rhEPO with high purity was achieved after three‐step chromatography following two‐step precipitation. The transgenic pig‐derived rhEPO was demonstrated to have comparable potency with CHO‐derived rhEPO. Transgenic pig‐derived rhEPO may not be therapeutically feasible because of different glycosylation, and thus further studies are required to elucidate the effect of this aberrant glycosylation on the biological activity and stability in vivo. Copyright © 2008 Society of Chemical Industry 相似文献
956.
A guest–host approach was used to fabricate a one-layer organic light emitting diode (OLED). The thick film ink approach allows the two-dimensional OLED to be processed using traditional methods such as silk-screen printing. The I–V–L characteristics of the polymer thick film (PTF)-OLED were studied as a function of the device chemical compositions and physical configurations. Different polymers, hole and electron transporters, and emitters at different weight ratios were studied for its composition dependence. Device configuration also plays a significant role on its overall performance. Dependence on film thickness, electrode type, and the usage of additional charge injection layers were also investigated. The simplified one-layer device allows a straightforward interpretation for the charge-transport and recombination phenomena which shed light for its future improvement. 相似文献
957.
Comparison of physical, chemical and cellular responses to nano- and micro-sized calcium silicate/poly(epsilon-caprolactone) bioactive composites. 下载免费PDF全文
Jie Wei S J Heo D H Kim S E Kim Y T Hyun Jung-Woog Shin 《Journal of the Royal Society Interface》2008,5(23):617-630
In this study, we fabricated nano-sized calcium silicate/poly(epsilon-caprolactone) composite (n-CPC) and micro-sized calcium silicate/poly(epsilon-caprolactone) composite (m-CPC). The composition, mechanical properties, hydrophilicity and degradability of both n-CPC and m-CPC were determined, and in vitro bioactivity was evaluated by investigating apatite forming on their surfaces in simulated body fluid (SBF). In addition, cell responses to the two kinds of composites were comparably investigated. The results indicated that n-CPC has superior hydrophilicity, compressive strength and elastic modulus properties compared with m-CPC. Both n-CPC and m-CPC exhibited good in vitro bioactivity, with different morphologies of apatite formation on their surfaces. The apatite layer on n-CPC was more homogeneous and compact than on m-CPC, due to the elevated levels of calcium and silicon concentrations in SBF from n-CPC throughout the 14-day soaking period. Significantly higher levels of attachment and proliferation of MG63 cells were observed on n-CPC than on m-CPC, and significantly higher levels of alkaline phosphatase activity were observed in human mesenchymal stem cells (hMSCs) on n-CPC than on m-CPC after 7 days. Scanning electron microscopy observations revealed that hMSCs were in intimate contact with both n-CPC and m-CPC surfaces, and significantly cell adhesion, spread and growth were observed on n-CPC and m-CPC. These results indicated that both n-CPC and m-CPC have the ability to support cell attachment, growth, proliferation and differentiation, and also yield good bioactivity and biocompatibility. 相似文献
958.
959.
Jong Hoon Kim Hyun Jung Kim Chulyoung Kim Heeyong Jung Yong Ook Kim Jae Yeong Ju Chul Soo Shin 《Food chemistry》2007,101(1):357-364
Derivatives of monascus pigment having high lipase-inhibitory activities were developed and characterized. Various derivatives of monascus pigment were produced during Monascus fermentation with added l-, d-amino acids. From them, compounds having high inhibitory activities against a porcine pancreatic lipase were selected. Monascus pigments produced with aromatic and non-polar aliphatic l-, d-amino acids revealed strong inhibitory activities against the lipase. l-Trp and d-Tyr derivatives showed especially low IC50 values of 61.2 and 103 μM, respectively. Further structure modifications of pigment derivatives were made with amino acid esters and dipeptides for enhanced inhibitory activity. l-Leu-OEt and l-Tyr-OEt derivatives made via further structure modifications showed high lipase-inhibitory activities with IC50 values of 12.2 and 13.8 μM, respectively. The l-Leu-OEt derivative exhibited some specificity against porcine pancreatic lipase but not exhibit high activities against other digestive enzymes. Some compounds were developed from modification of monascus pigment followed by lipase-inhibitory activity tests. 相似文献
960.
Water removal characteristics of proton exchange membrane fuel cells using a dry gas purging method 总被引:1,自引:0,他引:1
Sang-Yeop Lee Sang-Uk Kim Hyoung-Juhn Kim Jong Hyun Jang In-Hwan Oh Eun Ae Cho Seong-Ahn Hong Jaejun Ko Tae-Won Lim Kwan-Young Lee Tae-Hoon Lim 《Journal of power sources》2008,180(2):784-790
Water removal from proton exchange membrane fuel cells (PEMFC) is of great importance to improve start-up ability and mitigate cell degradation when the fuel cell operates at subfreezing temperatures. In this study, we report water removal characteristics under various shut down conditions including a dry gas-purging step. In order to estimate the dehydration level of the electrolyte membrane, the high frequency resistance of the fuel cell stack was observed. Also, a novel method for measuring the amount of residual water in the fuel cell was developed to determine the amount of water removal. The method used the phase change of liquid water and was successfully applied to examine the water removal characteristics. Based on these works, the effects of several parameters such as purging time, flow rate of purging gas, operation current, and stack temperature on the amount of residual water were investigated. 相似文献