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1.
In the present work it is found that the pyrotechnic composition VS-2 can be initiated with flash lamps IFC-500 and EVIS. VS-2 pyrotechnic composition contains 90% of mercury(Ⅱ) 5-hydrazinotetrazolate perchlorate and 10% of optically transparent copolymer of 2-methyl-5-vinyltetrazole and methacrylic acid (PVMT). We have found that the flash lamps make it possible to initiate combustion of VS-2 composition with its transition to detonation both in cylindrical charges placed in brass caps of 5 mm diameter and 2 mm high, and film charges with 10 mm×80 mm in size and surface weights of 60 mg·cm-2 and 90 mg·cm-2, showing ignition delay times 10 μs and 3 μs, respectively. We also measured detonation velocities for VS-2 composition film charges, which were 4375-4505 m·s-1 (of the charge being surface mass 60 mg·cm-2) and 4221-4281 m·s-1 (of the charge being surface mass 90 mg·cm-2) and their blasting action on the aluminum plate. The depths of the normal shock wave imprints at the charge-barrier interface were 0.6-0.7 mm (for surface mass of the film charges 60 mg·cm-2) and 1.2-1.3 mm (for surface mass of the film charges 90 mg·cm-2).  相似文献   
2.
Phase change materials (PCMs) play a leading role in overcoming the growing need of advanced thermal management for the storage and release of thermal energy which is to be used for different solar applications. However, the effectiveness of PCMs is greatly affected by their poor thermal conductivity. Therefore, in the present review the progress made in deploying the graphene (Gr) in PCMs in the last decade for providing the solution to the aforementioned inadequacy is presented and discussed in detail. Gr and its derivatives ((Gr oxide (GO), Gr aerogel (GA) and Gr nanoplatelets (GNPs)) based PCMs can improve the thermal conductivity and shape stability, which may be attributed to the extra ordinary thermo-physical properties of Gr. Moreover, it is expected from this review that the advantages and disadvantages of using Gr nanoparticles provide a deep insight and help the researchers in finding out the exact basic properties and finally the applications of Gr can be enhanced.In this work, Gr and its derivatives based PCMs was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM) by which crystal structure was known, phase was identified along with the knowledge of surface structure respectively. The increase in the mass fraction (%) of the filler (Gr and its derivatives) led to even better thermo-physical properties and thermal stability. The thermal characterization was also done by differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and thermal conductivity tests. The enthalpy of freezing and melting showed that Gr and its derivatives based PCMs had a very high energy storage capability as reflected in its various applications.  相似文献   
3.
Production routes were recorded on available reactions for 111Ag production from nuclear reactors or cyclotrons using a natural palladium target based on 110Pd(n, γ) and 110pd(d, n) reactions, respectively.natCd(γ,x) based on 110Cd(γ, p) has also been studied as a prospective reaction for the production of 111Ag. Unfortunately, these nuclear reactions are difficult to utilize because, in some cases, they reduce the specific activi...  相似文献   
4.
Suzuki-Miyaura (S-M) is regarded the most powerful way for synthesis biaryls, triaryls, or incorporating of substituted aryl moieties in organic preparation by the cross-coupling of aryl boronic acid with aryl halides using the Pd catalyst. This work reports the combining of the hydrothermal and microwave-assisted protocol to convert the glucose to magnetic carbon spheres (Fe3O4-CSPs) decorated with Pd nanoparticles (NPs) as the catalyst for Suzuki-Miyaura cross-coupling reactions. The physicochemical properties in the produced composite were examined using FESEM, HRTEM, nitrogen isotherms, Raman spectroscopy, FTIR, XPS, and XRD. The as-fabricated composite Pd/Fe3O4-CSPs is mostly spherical with a core–shell structure and possesses a great surface area of 253.2 m2·g-1. Its catalytic performance demonstrates that the composite has excellent stability and high tolerance Suzuki-Miyaura cross-coupling reactions in 30 min at 80 ℃. Both activated and deactivated aryl halides provided excellent yield. The as-fabricated catalyst was recycled for up to four catalytic cycles without a substantial decline in performance. Moreover, this research offers a facile roadmap for synthesizing Pd/Fe3O4-CSPs composites and promoting the practical implementation of Pd/Fe3O4-CSPs catalysts for organic transformation processes.  相似文献   
5.
6.
The uniform refinement mechanisms and methods of deformed mixed and coarse grains inside a solution-treatment Ni-based superalloy during two-stage annealing treatment have been investigated.The two-stage heat treatment experiments include an aging annealing treatment(AT)and a subsequent recrystallization annealing treatment(RT).The object of AT is to precipitate some δ phases and consume part of storage energy to inhibit the grain growth during RT,while the RT is to refine mixed and coarse grains by recrystallization.It can be found that the recrystallization grains will quickly grow up to a large size when the AT time is too low or the RT temperature is too high,while the deformed coarse grains cannot be eliminated when the AT time is too long or the RT temperature is too low.In addition,the mixed microstructure composed of some abnormal coarse recrystallization grains(ACRGs)and a large number of fine grains can be observed in the annealed specimen when the AT time is 3 h and RT tem-perature is 980℃.The phenomenon attributes to the uneven distribution of δ phase resulted from the heterogeneous deformation energy when the AT time is too short.In the regions with a large number of δ phases,the recrystallization nucleation rate is promoted and the growth of grains is limited,which results in fine grains.However,in the regions with few δ phases,the recrystallization grains around grain boundaries can easily grow up,and the new recrystallization nucleus is difficult to form inside grain,which leads to ACRGs.Thus,in order to obtain uniform and fine annealed microstructure,it is a prereq-uisite to precipitate even-distributed δ phase by choosing a suitable AT time,such as 12 h.Moreover,a relative high RT temperature is also needed to promote the recrystallization nucleation around δ phase.The optimal annealing parameters range for uniformly refining mixed crystal can be summarized as:900℃×12 h+990℃×(40-60 min)and 900℃×12 h+1000℃×(10-15 min).  相似文献   
7.
研究功能梯度泡沫填充管(FGFTs)在落锤冲击载荷作用下的变形行为和耐撞性。采用液态工艺制备的闭孔泡沫铝、A356合金泡沫和锌泡沫作为轴向梯度填料,用于制备不同构造的单层和多层结构。结果表明,多层泡沫填充管的变形由低强度部位开始,然后通过应力的逐渐增加在高强度部位中扩展。使用更多的A356合金和泡沫铝层可为梯度结构提供更大的比吸能(SEA),而高强度的锌泡沫对碰撞性能没有积极的影响。由泡沫铝和A356合金泡沫组成的梯度结构在准静态和落锤冲击条件下以对称模式发生连续倒塌。使用锌泡沫会引起对称模式和扩展模式倒塌,样品在动态加载下产生更大的局部变形,在准静态加载下产生更大的局部破裂。Al?A356泡沫填充管具有最高的SEA(10 J/g)和最低的初始峰值应力(σmax=10.2 MPa),是最好的轻质耐撞结构。  相似文献   
8.
Potassium carbonate-based sorbents are prospective materials for direct air capture (DAC). In the present study, we examined and revealed the influence of the temperature swing adsorption (TSA) cycle conditions on the CO2 sorption properties of a novel aerogel-based K2CO3/ZrO2 sorbent in a DAC process. It was shown that the humidity and temperature drastically affect the sorption dynamic and sorption capacity of the sorbent. When a temperature at the sorption stage was 29 ℃ and a water vapor pressure in the feed air was 5.2 mbar (1 bar = 105 Pa), the composite material demonstrated a stable CO2 sorption capacity of 3.4% (mass). An increase in sorption temperature leads to a continuous decrease in the CO2 absorption capacity reaching a value of 0.7% (mass) at T = 80 ℃. The material showed the retention of a stable CO2 sorption capacity for many cycles at each temperature in the range. Increasing PH2O in the inlet air from 5.2 to 6.8 mbar leads to instability of CO2 sorption capacity which decreases in the course of 3 consecutive TSA cycles from 1.7% to 0.8% (mass) at T = 29 ℃. A further increase in air humidity only facilitates the deterioration of the CO2 sorption capacity of the material. A possible explanation for this phenomenon could be the filling of the porous system of the sorbent with solid reaction products and an aqueous solution of potassium salts, which leads to a significant slowdown in the CO2 diffusion in the composite sorbent grain. To investigate the regeneration step of the TSA cycle in situ, the macro ATR-FTIR (attenuated total reflection Fourier-transform infrared) spectroscopic imaging was applied for the first time. It was shown that the migration of carbonate-containing species over the surface of sorbent occurs during the thermal regeneration stage of the TSA cycle. The movement of the active component in the porous matrix of the sorbent can affect the sorption characteristics of the composite material. The revealed features make it possible to formulate the requirements and limitations that need to be taken into account for the practical implementation of the DAC process using the K2CO3/ZrO2 composite sorbent.  相似文献   
9.
为了更好地对应县木塔进行保护,需要分析其形变程度,了解木塔的健康状况,进而制定科学的保护方案。利用地面激光雷达、高精度全站仪等测量传感器,通过激光雷达扫描和全站仪控制测量相结合的方案采集监测数据。首先对采集的点云数据进行预处理,外部点云采用整体配准算法进行配准,通过特征进行粗配准和迭代最近点(ICP)算法进行精配准的两次配准,配准后根据控制点完成内、外点云坐标转换,通过罗德里格矩阵求解空间转换参数,最终得到绝对坐标系下的整体点云模型。对点云模型进行多种剖切,测量出柱子的倾斜角度、偏移距离以及整体倾斜角度等数据,定量分析单柱、单层及整体的形变。结果表明:应县木塔各层柱子都存在形变,木塔第2层形变较大,其中M2W23号柱子倾斜最严重; 各层均向东北方向有不同程度的倾斜,西南面柱子的位移量普遍较大; 从整体上看,木塔向东北方向倾斜并存在着复杂的扭转变形,木塔西侧由南向北发生顺时针扭转,东侧由南向北发生逆时针扭转; 应县木塔正处于严重的形变中,急需进行保护。  相似文献   
10.
3D打印属于叠加式制造方式,可创造出多种三维模型。3D打印的缺点之一是制造大型物体时耗时较长。因此,目前最先进的技术仅限于制造小型物体。3D打印与其他材料相结合有助于克服由印刷时间所造成的缺点。如使用传统技术制造的大型物体的特定位置,可由3D打印完成,以创建所需的功能。此前,将聚合物3D打印在机织物上的试验研究结果表明:印刷材料和机织物结构的不同,导致二者之间的黏附力差异较大。该结果也适用于针织物的3D打印。试验所用材料均为聚乳酸(PLA),因其与机织物的黏合力最强。熔融沉积成型(FDM)打印项目,研究了针织织物种类、材料、结构、织机机号等变化,对喷嘴的尺寸、打印高度、印刷床温度等的影响,并对结果进行了总结。同时,对针织物3D打印过程中必需进行的测试进行了展望。  相似文献   
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