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   1692篇
  免费   36篇
  国内免费   3篇
电工技术   80篇
综合类   4篇
化学工业   352篇
金属工艺   33篇
机械仪表   54篇
建筑科学   32篇
能源动力   50篇
轻工业   141篇
水利工程   6篇
石油天然气   4篇
无线电   205篇
一般工业技术   282篇
冶金工业   340篇
原子能技术   45篇
自动化技术   103篇
  2023年   6篇
  2022年   19篇
  2021年   37篇
  2020年   12篇
  2019年   16篇
  2018年   34篇
  2017年   24篇
  2016年   26篇
  2015年   16篇
  2014年   39篇
  2013年   86篇
  2012年   69篇
  2011年   80篇
  2010年   67篇
  2009年   59篇
  2008年   76篇
  2007年   58篇
  2006年   51篇
  2005年   56篇
  2004年   46篇
  2003年   54篇
  2002年   55篇
  2001年   31篇
  2000年   37篇
  1999年   49篇
  1998年   127篇
  1997年   71篇
  1996年   68篇
  1995年   53篇
  1994年   45篇
  1993年   35篇
  1992年   18篇
  1991年   19篇
  1990年   24篇
  1989年   25篇
  1988年   14篇
  1987年   10篇
  1986年   15篇
  1985年   9篇
  1984年   10篇
  1983年   9篇
  1982年   14篇
  1981年   6篇
  1980年   12篇
  1979年   7篇
  1978年   4篇
  1977年   13篇
  1976年   11篇
  1975年   3篇
  1973年   2篇
排序方式: 共有1731条查询结果,搜索用时 46 毫秒
91.
Immunoglobulin A1 (IgA1) concentration in the plasma of patients with IgA nephropathy (IgAN) as the cause of renal failure is higher than that in the plasma of normal controls. IgA1 with abnormal sugars is considered to deposit in the glomerular mesangium, aggravating nephritis in IgAN. Jacalin is a lectin that recognizes sugars on IgA1. However, its selective-recognition for normal-type (ST type, NeuAc-α(2,3)-Gal-β(1,3)-GalNAc) and abnormal-type (T type, Gal-β(1,3)-GalNAc; Tn type, GalNAc; STn type, NeuAc-α(2,6)-GalNAc) sugars α-O-linked to serine/threonine in IgA1 is weak. Therefore, jacalin cannot be used for recognizing specific sugar types on IgA1. We attempted to develop a new recognition method for specific sugar types on IgA1 by utilizing the multirecognition capability of jacalin. Its binding abilities were regulated by heat denaturation with suitable template sugar (galactose or N-acetylgalactosamine). Further, we successfully prepared denatured-jacalin derivatives, which recognized ST-/T-type sugars on IgA1, by sugar-immobilized affinity chromatography. Enzyme-linked immunosorbent assay of denatured-jacalin derivatives, showed the ratios of abnormal sugars on IgA1 in the plasma of IgAN patients and normal controls to be approximately 60% and 20%, respectively. The results proved that profiling of sugar types in IgAN can successfully be performed by solely using jacalin derivatives.  相似文献   
92.
A novel cycloaliphatic monomer for polyimides (PI), 1S,2S,4R,5R-cyclohexanetetracarboxylic dianhydride (H′-PMDA) is proposed in this work. H′-PMDA shows high polymerizability with various diamines in contrast to its isomer, i.e., conventional hydrogenated pyromellitic dianhydride (H-PMDA) and leads to highly flexible and colorless PI films with very high Tg's. In particular, the combinations with rigid structures of diamines give rise to PIs with significantly decreased coefficients of thermal expansion (CTE) owing to high extents of in-plane chain orientation induced by thermal imidization, whereas the H-PMDA-based counterparts do not. The decreased CTE reflects structural rigidity/linearity of the H′-PMDA-based diimide units as supported by liquid crystallinity observed in the corresponding model compound. Solution casting of a chemically imidized PI derived from H′-PMDA and 2,2′-bis(trifluoromethyl)benzidine (TFMB) results in a lower CTE than that of the thermally imidized counterpart, suggesting the presence of a self-orientation phenomenon during solvent evaporation. The mechanism is proposed in this work. H′-PMDA/TFMB and its copolymer systems can be useful as plastic substrates in image display devices and/or novel coating-type optical compensation films.  相似文献   
93.
Aqueous solutions of gellan gum with comparable molecular mass but with different acyl contents were investigated by atomic force microscopy and rheological measurements in the presence of sodium chloride (NaCl). Results obtained were discussed in relation to our previous report using potassium chloride (KCl) as an added salt. For a low-acyl sample, continuous fibrous network structures were identified microscopically as in the case of KCl. The network structures were more heterogeneous than those formed with KCl in terms of the height distribution of molecular assemblies. Rheological thermal hysteresis between sol–gel transitions was detected as in the case of KCl. The storage modulus (G′) of the gelled system was ca. 15% of the corresponding data with KCl at 20 °C. For a high-acyl sample, no continuous network structures were identified but branches with observable ends were identified as in the case of KCl. The hysteresis was less evident than the corresponding data with KCl and for the low-acyl sample with NaCl. Also, G′ values at 20 °C were ca. 30% and 20% of the corresponding data with KCl and for the low-acyl sample with NaCl, respectively. Continuousness and homogeneity of network structures related to the hysteresis and elasticity of the system, respectively.  相似文献   
94.
The fluoride adsorption onto the hydroxide flocs of Al(III), Fe(III), or a mixture of the two was studied. The optimum pH was influenced by the flocs’ solubility and surface charge. Although the Al(III) hydroxide flocs had a maximum adsorption capacity at the equilibrium concentration of 8 mg-F/L, the two-stage adsorption process revealed that the mixture of the Al(III) and Fe(III) hydroxide flocs required the smallest adsorbent dose as the concentration changed from 40 to 8 mg-F/L. Thus, the simultaneous dosing of Al(III) and Fe(III) combined with a two-stage adsorption process appears to be an effective option for fluoride removal.  相似文献   
95.
96.
97.
Nakagawa T  Sato S  Yamamoto Y  Fukui M 《Water research》2002,36(11):2813-2823
The microbial community structure and successive changes in a mesophilic ethylbenzene-degrading sulfate-reducing consortium were for the first time clarified by the denaturing gradient gel electrophoresis (DGGE) analysis of the PCR amplified 16S rRNA gene fragments. At least ten bands on the DGGE gel were detected in the stationary phase. Phylogenetic analysis of the DGGE bands revealed that the consortium consisted of different eubacterial phyla including the delta subgroup of Proteobacteria, the order Sphingobacteriales, the order Spirochaetales, and the unknown bacterium. The most abundant band C was closely related to strain mXyS1, an m-xylene-degrading sulfate-reducing bacterium (SRB), and occurred as a sole band on DGGE gels in the logarithmic growth phase that 40% ethylbenzene was consumed accompanied by sulfide production. During further prolonged incubation, the dominancy of band C did not change. These results suggest that SRB corresponds to the most abundant band C and contributes mainly to the degradation of ethylbenzene coupled with sulfate reduction.  相似文献   
98.
Abstract— A common‐decoder architecture for a data‐driver circuit fabricated by using a polysilicon process has been developed. The architecture achieves a compact circuit and low‐power consumption. In application to an integrated polysilicon data driver for small‐sized displays, this architecture reduces the area of the data driver by removing the vertical bus lines that occupy a large area. It also suppresses the power consumption of the data bus by reducing the number of driven lines in the data bus during word‐to‐word transitions from six to two. By using a conventional 4‐μm design rule, we fabricated an active‐matrix OLED (AMOLED) panel with an integrated six‐bit data‐driver circuit with 384 outputs. The driver circuit had a height of 2.6 mm and a pitch between output lines of 84 μm. The maximum power consumption of the driver was only 5 mW, i.e., 3.8 mW for logic‐data transfer and 1.2 mW for reference‐voltage source. Furthermore, we also fabricated an active‐matrix LCD (AMLCD) panel including driver circuits of the same type as the integrated elements. Six‐bit full‐color images were successfully displayed on both panels.  相似文献   
99.
The In this paper, a simulator of a one‐wheel Electric Vehicle system is designed for testing an anti‐slip controller using the Motor‐Generator system. The drive motor of the M‐G system is used to simulate the drive wheel of the Electric Vehicle, and the load motor is used to simulate the load force of the chassis. In the driving process, the torque of the load motor is changed according to the drive force of the chassis that is calculated by the program. So it can simulate the dynamic process of the tire‐road system. Based on this simulator system, an anti‐slip controller based on an Adhesion Status Analyzer is proposed. Information about the wheel speed is acquired by using a Back EMF Observer. A load torque disturbance observer is designed to stabilize the acceleration of the wheels. The Adhesion Status Analyzer is used to generate safe acceleration commands for the anti‐slip controller. When a slip occurs, the anti‐slip controller will decrease the torque quickly, and at the same time, by estimating the dynamic status of adhesion, the Adhesion Status Analyzer will restrain the acceleration command within a safe area. The effectiveness of the proposed approach is verified by using the EV slip simulator.  相似文献   
100.
The anisotropic scattering effect to keff is studied for UO2 and MOX fueled BWR assemblies. The anisotropic scattering effect increases the assembly k by 0.44% Δk for the UO2 assembly with 0% void fraction, and by 0.21% Δk for the MOX assembly with 0% void fraction. This is because the anisotropic scattering effect flattens the intra-assembly thermal flux, and the absorption rate in the surrounding water gap is decreased, but the absorption rates in the MOX fuel rods are increased compared to the UO2 rods. Therefore, the total decrease in absorption rates in the UO2 assembly is relatively large, and the k is increased in the UO2 assembly. The dependence of the anisotropic scattering effect on the void fraction is investigated, and the significant difference of 0.62% Δk/k is found for the 0% and the 80% void fractions. The BWR assemblies with Gd rods are also considered. Furthermore, the usefulness of the transport cross section is investigated, and it is found that the transport cross section gives reasonable anisotropic scattering effect, though not satisfactory.  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