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排序方式: 共有8468条查询结果,搜索用时 31 毫秒
81.
Jinmao You Fang Zhu Wenchen Zhao Xian'en Zhao Yourui Suo Sujuan Liu 《European Journal of Lipid Science and Technology》2007,109(3):225-236
A sensitive method for the determination of free fatty acids using 2‐(2‐(anthracen‐10‐yl)‐1H‐naphtho[2,3‐d]imidazol‐1‐yl) ethyl‐p‐toluenesulfonate (ANITS) as tagging reagent with fluorescence detection has been developed. ANITS could easily and quickly label fatty acids in the presence of the K2CO3 catalyst at 90 °C for 40 min in N,N‐dimethylformamide solvent. From the extracts of rape bee pollen samples, 20 free fatty acids were sensitively determined. Fatty acid derivatives were separated on a reversed‐phase Eclipse XDB‐C8 column by HPLC in conjunction with gradient elution. The corresponding derivatives were identified by post‐column APCI/MS in positive‐ion detection mode. ANITS‐fatty acid derivatives gave an intense molecular ion peak at m/z [M+H]+; with MS/MS analysis, the collision‐induced dissociation spectra of m/z [M+H]+ produced the specific fragment ions at m/z [M–345]+ and m/z 345.0 (here, m/z 345 is the core structural moiety of the ANITS molecule). The fluorescence excitation and emission wavelengths of the derivatives were λex = 250 nm and λem = 512 nm, respectively. Linear correlation coefficients for all fatty acid derivatives are >0.9999. Detection limits, at a signal‐to‐noise ratio of 3 : 1, are 24.76–98.79 fmol for the labeled fatty acids. 相似文献
82.
用于测定钢液低氧含量的双层固体电解质研究 总被引:1,自引:0,他引:1
采用“毛坯浆料法”在ZrO2(9%摩尔含量MgO)管状固体电解质基体表面制备了厚度为1-4μm的ZrO2(10%摩尔含量Y2O3)固体电解质涂层,并分别对此在本实验室和美国LeedsandNorthrup公司进行了钢液低氧含量测试,结果表明:涂层没有破坏基体的抗热震性:氧浓差电池电动势的重现性偏差由原来的±2mV;电动势的绝对值提高10mV左右;而比日本Toray公司的同类产品提高35mV,这说明 相似文献
83.
84.
本设计以第八届"飞思卡尔"杯全国大学生智能车竞赛为背景,提出了一种根据线性CCD采集图像引导直立小车循迹行驶的方案。本文介绍了这一方案的基本思想,所依据的物理原理,并重点介绍在双速度控制算法下对转向及障碍问题的优化处理,并根据方案实际制作了小车。实践证明该方案是可行的,并且效果较好。 相似文献
85.
Zhe-Feng Zhang Zheng Ming Sun Hitoshi Hashimoto Toshihiko Abe 《Journal of the American Ceramic Society》2003,86(3):431-436
Ti/Si/2TiC powders were prepared using a mixture method (M) and a mechanical alloying (MA) method to fabricate Ti3 SiC2 at 1200°–1400°C using a pulse discharge sintering (PDS) technique. The results showed that the Ti3 SiC2 samples with <5 wt% TiC could be rapidly synthesized from the M powders; however, the TiC content was always >18 wt% in the MA samples. Further sintering of the M powder showed that the purity of Ti3 SiC2 could be improved to >97 wt% at 1250°–1300°C, which is ∼200°–300°C lower than that of sintered Ti/Si/C and Ti/SiC/C powders using the hot isostatic pressing (HIPing) technique. The microstructure of Ti3 SiC2 also could be controlled using three types of powders, i.e., fine, coarse, or duplex-grained, within the sintering temperature range. In comparison with Ti/Si/C and Ti/SiC/C mixture powders, it has been suggested that high-purity Ti3 SiC2 could be rapidly synthesized by sintering the Ti/Si/TiC powder mixture at relatively lower temperature using the PDS technique. 相似文献
86.
X-ray fiber diagram of uniaxially-oriented nylon 10/10 sample has been measured at the various temperatures. The 11th layer line originating from the methylene zigzag sequences became diffuse above the Brill transition region (140-170 °C), while the layer reflections corresponding mainly to the original repeating period of the parent nylon chains were kept almost unchanged. This observation makes us confirm that in the Brill transition region, the conformational disordering occurs in the methylene sequential parts with keeping the repeating period of the whole skeletal chain by still forming the intermolecular hydrogen bonds between the amide groups of the neighboring chains. This conclusion is consistent with the already-reported infrared spectral data. The characteristic X-ray diffraction patterns observed at the various temperatures were reproduced well by a computer simulation technique utilizing the previously-reported molecular dynamics calculation results. 相似文献
87.
Physical-chemical properties of phosphorous gypsum, proportion and cemented mechanism of slurry with gypsum as aggregate were
studied to remove the harms of gypsum pile, combining with difficult problems of excessive mined-out gobs, enormous ore body
under roadway and low recovery ratio of Yongshaba Mine, Kaiyang Phosphor Mine Group, Guizhou Province, China. An appropriate
backfill system and craftwork were designed, using shattering milling method to crush gypsum, double-axles mixing and strong
activation mixing way to mix slurry, cemented slurry and mullock backfill alternately process. The results show that gypsum
is fit for backfilling afterwards by adding fly ash, though it is not an ideal aggregate for fine granule and coagulate retardation.
The suggested dosage (the mass ratio of cement to fly ash to gypsum) is 1:1:6–1:1:8 with mass fraction of solid materials
60%–63%. Slurry is transported in suspend state with non-plastic strength, and then in concretion state after backfilling.
The application to mine shows the technology is feasible, and gypsum utilization ratio is up to 100%. Transportation and backfill
effect is very good for paste-like slurry and drenching cemented slurry into mullock, and the compressive strength and recovery
ratio are 2.0 MPa and 82.6%, respectively, with the maximum subsidence of surface only 1.307 mm. Furthermore, the investment
of system is about 7×106 yuan (RMB), only 1/10 of that of traditional paste backfill system.
Foundation item: Project (2006BAB02A03) supported by the National Key Technology Research and Development Program; Project (08MX16) supported
by Mittal Scientific and Technological Innovation Projects of Central South University during 2008 相似文献
88.
粗晶硬质合金强度和致密度影响因素的研究 总被引:2,自引:0,他引:2
针对粗晶WC-Co硬质合金的成分和工艺优化要求,运用正交实验设计,考察了含碳量、烧结工艺、钴含量、镍含量、球磨球料比和球磨时间对试样抗弯强度和体积收缩率的影响。研究表明,烧结制度是影响抗弯强度的最主要因素;其次是碳含量与烧结工艺的交互作用、Co含量与球磨时间的交互作用。烧结工艺是影响体积收缩率的最主要因素。 相似文献
89.
基于Multisim10仿真软件,设计单片机的虚拟串口驱动LCD1602液晶电路。实现了虚拟串口扩展并行输出的功能。该设计适用单片机UART串口被占用时,以最少的单片机I/O口驱动LCD1602,满足显示电路中复杂信息的需求。与传统的设计手段相比,在Multisim10平台支撑下,设计电路更方便快捷,并可通过仿真结果直接观测和验证设计电路是否达到要求,具有省时、低耗、高效的优越性。 相似文献
90.
提出并研究了使用1,10-二氮杂菲分光光度法测定沉淀法白炭黑中铁含量的分析方法。其具体步骤为:首先用氢氟酸处理试样,使沉淀法白炭黑(二氧化硅)转化成四氟化硅气体逸出。而后在pH为4~5条件下,用盐酸羟胺处理剂将残留液中的三价铁离子还原成二价铁离子,加入1,10-二氮杂菲显色剂(与二价铁离子反应可生成橙红色络合物),再用分光光度法测定其中的铁含量。实验表明,本方法原理可靠,分析步骤简便,抗铜、锰离子干扰性强,精密度与准确度较高。 相似文献