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31.
液晶聚酯由于具有特异的液晶行为和高强高模性能而越来越受到人们的关注。本文对液晶聚酯的液晶态形成原因、液晶态类型与链结构的关系、液晶态热稳定性及其成型加工性能进行了讨论,指出了提高液晶态热稳定性的方法及液晶聚酯的发展趋势。 相似文献
32.
到目前为止TiO2是较为成熟的半导体光催化材料,但因TiO2分散性差、量子利用率低、比表面积小、难回收等问题难以工业化。多孔金属有机框架MOFs的引入可增强TiO2/MOFs复合材料的光吸收性能,提高电子-空穴对分离和提高回收率。基于TiO2/MOFs制备时前驱体添加顺序不同,综述了TiO2/MOFs的三种制备方法(即Ship-in-a-bottle法、Bottle-around-ship法、One-pot法)及TiO2/MOFs光催化机理与性能影响因素,并探讨不同MOFs与TiO2结合的作用机理。最后,对TiO2/MOFs存在的问题提出建议。 相似文献
33.
The dynamics of the crystal size distribution in a continuous mixed suspension, mixed product removal crystallizer is modeled stochastically. The model is fairly general in that it involves a size-dependent growth rate function: this size-dependent growth rate as a possible cause of deviation on the behavior of the crystallizer from that of an idealized or simplified counterpart has been investigated based upon the model. 相似文献
34.
Li-Na Zhu Lei Z. Zhang Wen-Zhen Wang Dai-Zheng Liao Peng Cheng Zong-Hui Jiang Shi-Ping Yan 《Inorganic chemistry communications》2002,5(12):434
A novel coordination polymer [Zn(BDC)(H2O)2]n 1 (where BDC = 1,4-benzenedicarboxylate), has been synthesized and characterized by X-ray diffraction. 1 crystallizes in the monoclinic space group C2/c, a=15.09(2) Å, b=5.058(7) Å, c=12.196(16) Å, β=103.62(2)°,
, Z=4. The most striking feature of 1 is that it consists of a high-dimensional network structure constructed from BDC-bridged 1-D chains via interchain hydrogen bonds. The coordination sphere of the zinc(II) ion is a distorted tetrahedron completed by four oxygen atoms from two water molecules and two BDC ligands. BDC adopts the bis-monodentated (syn–anti) coordination mode linking two adjacent zinc(II) ions. 1 shows strong blue photoluminescence as the result of the fluorescence from the intraligand emission excited state. 相似文献
35.
Byoung Chul Kim Hyun Woog Kang Young Han Kim 《Korean Journal of Chemical Engineering》2006,23(5):789-794
A crystallization monitoring system using a quartz crystal oscillator was utilized to predict different shapes of crystal
formation by measuring crystal growth rate and to measure supersaturation. Applying different rates of cooling, crystal formation
of different shapes was induced, and the frequency variation of the oscillator and the crystal shape observed with an SEM
were compared to determine how the frequency variation can be interpreted for the prediction of produced crystal shape. The
experimental results obtained from the crystallization of potassium nitrate and cupric sulfate solutions showed that the proposed
frequency measurement technique could be applied in the prediction of crystal shape of cooling crystallization processes.
In addition, supersaturation was determined from the measurements of solution and coolant temperatures. 相似文献
36.
研究与开发(Research and Development,R&D)投资、传统贴现现金流量(DiscountedCash Flow,DCF)方法忽略了项目自身管理弹性的价值;实物期权虽能较好地捕捉管理弹性的价值,却未能有效解决高度不确定环境下参变量的波动性问题;蒙特卡罗模拟能解决参变量的波动性问题,但需要复杂的计算机程序来解决算法问题.作者在分析实物期权的基础上,运用蒙特卡罗理论,使用水晶球软件来进行R&D决策分析.通过实例证明,水晶球模拟方法可以更为科学有效地解决高度不确定条件下的R&D决策问题. 相似文献
37.
The kinetics of growth of Mg(OH)2, seed crystals at 298, 308 and 318 K from an a~ueous supersaturated solution of initial concentrations of Mg(OH)2 0,48, 0.60 and 0.73 mol-3 were determined. The growth was followed by measuring the conductivity of a seeded system as a function of time. The growth kinetics satisfied a first order kinetic equation. Within the examined range of variables the kinetic constant is independent of temperature and the initial concentration and dependenl on the surface area of seeds added at the start of the experiment. The growth of crystals under the studied conditions is controlled by the surface reaction mechanism. 相似文献
38.
We report here the solvothermal synthesis and crystal structure of the hybrid inorganic-organic framework material Al2[O3PC4H8PO3](H2O)2F2⋅2H2O (monoclinic, 1P21/m, a = 4.961(2) ?, b = 11.930(5) ?, c = 10.727(5) ?, β = 93.972(6)∘, Z = 2, R(F, F2 > 2σ) = 0.094, Rw(F2, all data) = 0.262), the third member of the Al2[O3PCnH2nPO3](H2O)2F2 framework series. The structure is formed from corrugated chains of corner-sharing AlO4F2 octahedra in which alternating AlO4F2 octahedra contain two fluorine atoms in a trans or a cis configuration. The diphosphonate groups link the chains together through Al-O-P-O-Al bridges and through the butyl groups
to form a three-dimensional framework structure containing a one-dimensional channel system consisting of one type of channel
only. The channels contain four extra-framework water molecules per unit cell. The formation of this member of the series
shows that the form of the alkyl chain can successfully define the number of channel types and the channel length in this
hybrid framework system. 相似文献
39.
Teaching and learning through Virtual Reality(VR) is an emerging technology in the last few years. In this article, the development and use of a VR based teaching–learning system for crystal structures are discussed. The VR system is designed as a lab environment where a user can do experiments related to crystal structures. The VR system is designed in Unity,1 and Oculus Rift S2 is used as a VR headset. Currently, the system consists of three phases; in the first phase user can visualize the crystal lattice structures, wherein the second one a user can visualize the light interaction with the crystal lattice structure using a virtual torch ray. The third phase is the X-ray Diffraction (XRD) experiment. In this phase, users can perform the XRD experiment in the lab environment by taking a random crystal from a crystal dispenser machine and placing it in the X-ray machine which identifies the chosen crystalline material and analyses the unit cell. The incident ray colour changes when there is a peak found in the crystal for a better understanding of the user. There is also an interactive display where users can increase/decrease the angles of the radiation and also lock and unlock the experiment to view the diffraction plot for the crystal structure. In many cases, it was found that XRD and the crystal structure is available in the course syllabus but there are no experiments to enhance their learning. Therefore an experiment with 39 participants was performed where the maximum participants are new to crystallography. The study was conducted in two phases; in the first phase, participants are asked to watch video tutorials of the topic followed by questionnaires; in the second phase participants are asked to do the VR based experiment and followed by questionnaires related to overall study and experiment. From the analysis of the study we found that everyone found VR based teaching methods are better than traditional book/video studies. Study results give an average score of 56.74% in comparison to VR based learning approach with an average score of 93.81%. Participants who took part in the experiment found the experience interactive and motivating and found it helpful to learn elusive concepts, which can be learned when simulated. For example, one participant wrote: “The VR experience was surreal and was easy to control. Lucid user experience. Got a view of XRD like never seen before”. 相似文献
40.
Michael P. Balogh Camille Y. Jones J.F. Herbst Louis G. Hector Jr. Matthew Kundrat 《Journal of Alloys and Compounds》2006,420(1-2):326-336
Half-Heusler compounds of Sn-doped TiCoSb “TiCoSnxSb1−x (x = 0.0, 0.01, and 0.05)” were prepared and their thermoelectric properties were measured above room temperature. From the EDX analysis, all the samples have three phases: the TiCoSnxSb1−x, Co-rich, and Ti-rich phases. The values of the thermoelectric power increase with Sn doping, and a positive thermoelectric power is obtained in the sample of TiCoSn0.05Sb0.95. The thermal conductivity decreases both with increasing temperature and with Sn content. The maximum value of ZT for p-type material is 0.030 at 988 K in the sample of TiCoSn0.05Sb0.95. 相似文献