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121.
122.
为了研究汽车尾气颗粒物的结构和氮的种态,使用扫描透射X射线显微成像(STXM)技术研究了桑塔纳3000和高尔汽车尾气颗粒物.STXM表明单颗粒物的粒径为500nm,颗粒物质量分布不均匀,有中间空洞.比较汽车尾气颗粒物和(NH4)2SO4和NaNO3中N的1sX射线近边吸收精细结构谱(NEXAFS),铵盐在406eV有显著的σ*吸收峰,有肩部结构;汽车尾气颗粒物和NaNO3中N的近边吸收谱在412eV和418.5eV有明显的σ吸收峰;(NH4)2SO4中N的近边吸收谱在413.5eV和421.8eV更宽的σ吸收峰.硝酸盐是汽车尾气颗粒物中的N化学种态的主要存在形式.在395—418eV能量范围内对桑塔纳3000汽车尾气颗粒物进行堆栈扫描,经过主成分分析和聚类分析,发现其表层主要为硝酸盐,内部有少量铵盐. 相似文献
123.
Q Zhang Z Gao F Xu S Tai X Liu S Mo F Niu 《Langmuir : the ACS journal of surfaces and colloids》2012,28(33):11979-11987
A series of novel cationic gemini surfactants with diethylammonium headgroups and a diamido spacer were synthesized, and their surface and bulk properties were investigated by surface tension, electrical conductivity, fluorescence, viscosity, dynamic light scattering (DLS), and transmission electron microscopy (TEM) measurements. An interesting phenomenon, that is, the obvious decline in surface tension upon increasing concentration above the critical micelle concentration (cmc), was found in these gemini surfactant solutions, and two explanations were proposed. This surface tension behavior could be explained by the rapid increase in the counterion activity in the bulk phase or the continued filling of the interface with increasing surfactant concentration above the cmc. More interestingly, not only vesicles but also the surfactant-concentration-induced vesicle to larger aggregate (spongelike aggregate) transition and the salt-induced vesicle and spongelike aggregate to micelle transition were found in the aqueous solutions of these gemini surfactants. The spongelike aggregate that is first reported in the cationic gemini surfactant-water binary system is probably caused by the adhesion and fusion of vesicles at high surfactant concentration. 相似文献
124.
Dynamic and Quantitative Control of the DNA‐Mediated Growth of Gold Plasmonic Nanostructures 下载免费PDF全文
Dr. Jianlei Shen Lifeng Xu Dr. Chunpeng Wang Dr. Hao Pei Prof.Dr. Renzhong Tai Prof.Dr. Shiping Song Prof.Dr. Qing Huang Prof.Dr. Chunhai Fan Prof.Dr. Gang Chen 《Angewandte Chemie (International ed. in English)》2014,53(32):8338-8342
Reproducible and controllable growth of nanostructures with well‐defined physical and chemical properties is a longstanding problem in nanoscience. A key step to address this issue is to understand their underlying growth mechanism, which is often entangled in the complexity of growth environments and obscured by rapid reaction speeds. Herein, we demonstrate that the evolution of size, surface morphology, and the optical properties of gold plasmonic nanostructures could be quantitatively intercepted by dynamic and stoichiometric control of the DNA‐mediated growth. By combining synchrotron‐based small‐angle X‐ray scattering (SAXS) with transmission electron microscopy (TEM), we reliably obtained quantitative structural parameters for these fine nanostructures that correlate well with their optical properties as identified by UV/Vis absorption and dark‐field scattering spectroscopy. Through this comprehensive study, we report a growth mechanism for gold plasmonic nanostructures, and the first semiquantitative revelation of the remarkable interplay between their morphology and unique plasmonic properties. 相似文献
125.
以三聚氰胺和硼酸为原料在水溶液中反应合成出了一种新的BCN化合物先驱体C3N6H6(H3BO3)2。XRD表征结果表明三聚氰胺和硼酸的最佳配比为1∶3(物质的量比)。用单晶X-射线衍射分析法测定了该化合物的晶体结构。该化合物属单斜晶系,空间群为P21/C,晶胞参数为a=0.3597(7)nm,b=2.0105(4)nm,c=1.4112(3)nm,α=90,°β=92.07(3),°γ=90,°V=1.0199(3)nm3,Z=4,D c=1.627g.cm-3,μ(MoKα)=0.144mm-1,F(000)=520。晶体结构经全矩阵最小二乘法修正,最终可靠因子R1=0.0519,wR2=0.1361。该化合物是由C3N6H6分子和H3BO3分子通过氢键加合组装形成的三维超分子结构化合物。 相似文献
126.
Zhihua Qiao Qilong Tai Lei Song Yuan Hu Pin Lv Ganxin Jie Wei Huang Yi Fu Deqing Zhang 《先进技术聚合物》2011,22(12):2602-2608
An intumescent flame retardant system composed of ammonium polyphosphate (APP) and pentaerythritol (PER) was used for flame retarding ethylene–propylene–diene‐modified elastomer (EPDM)/polypropylene (PP) blends. Cerium phosphate (CeP) was synthesized and the effect on flame retardancy and thermal stability of EPDM/PP composites based on intumescent flame retardant (IFR) were studied by limiting oxygen index (LOI), UL‐94, and thermogravimetic analysis (TGA), respectively. Scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR) were used to analyze the morphological structure and the component of the residue chars formed from the EPDM/PP composites, and the mechanical properties of the materials were also studied. The addition of CeP to the EPDM/PP/APP/PER composites gives better flame retardancy than that of EPDM/PP/APP/PER composites. TGA and RT‐FTIR studies indicated that an interaction occurs among APP, PER, and EPDM/PP. The incorporation of CeP improved the mechanical properties of the materials. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
127.
Ling Tian TANG Yi WANG Xin Qi LIU Shao Wen HU Tai Wei CHU Xiang Yun WANG* College of Chemistry Molecular Engineering Peking University Beijing 《中国化学快报》2005,16(3):345-348
Benzimidazole compounds have attracted a renewed interest recently owing to theirpotential applications in high-performance composite materials, electronic chemicals,photosensitive materials, and their special potentials in biological and/or medicinalapplication1,2. Typically, aromatic compounds with near planar structures and contain-ing hydrogen-donor groups or groups, which are capable of being protonated, havespecial interactions with DNA via intercalation, hydrogen-bonding, and so on3.Me… 相似文献
128.
Tai Shan YI Li Hong HUANG 《数学学报(英文版)》2007,23(8):1375-1384
The authors investigate the asymptotic behavior of solutions to a class of systems of delay differential equations. It is shown that every bounded solution of such a class of systems tends to a constant vector as t→∞. Our results improve and extend some corresponding ones already known. 相似文献
129.
Yun Long ZHANG Liang Ren ZHANG* Zhen Jun YANG Ji Mei MIN Li He ZHANG* Yang LU Ning Bo GONG Qi Tai ZHENG National Research Laboratory of Natural Biomimetic Drugs Peking University Beijing Institue of Materia Medica Chinese 《中国化学快报》2001,(5)
Tubercidin (4-amino-7--D-riobofuranosyl-7-H-pyrrolo[2,3-d]pyrimidine) 1, an antibio-tic substance produced in the culture broth of Streptomyces tubericidus1, is an adenosine analog in which N-7 is replaced by a carbon atom. It has attracted much attention due to the biological activities for the growth inhibition of certain tumors, and many derivatives of tubercidin have been synthesized2-5.For the synthesis of tubercidin analogs, 4-chloro-7-H-pyrrolo[2,3-d]pyrimidine-2,3,5-tri-O-acetyl--D-r… 相似文献
130.
In this study, we detail a method for estimating the flux-averaged solid fraction of a steady granular flows moving down an
inclined rectangular chute using velocity measurements from along the perimeter cross section, combined with knowledge of
the mass flow rate through the cross section. The chute is 5 cm wide and 150 cm long with an adjustable inclination angle.
Four inclination angles, from 27° to 36° at 3° intervals, are tested. This angle range overlaps the internal friction angle
of the glass beads, which are 4 mm nominal in diameter. Two slender mirrors are installed at the top and the bottom of the
transparent chute to reflect images of the flow down the chute of the two surfaces. This allows photographic recording of
the flow with a PIV imaging system and measurement of the flow depth. The mass flow rate can be calibrated simultaneously
by collecting the accumulated mass at the chute exit. A linear interpolation scheme is proposed to interpolate the volume
flow rate in each section of the chute. Sensitivity analysis suggests that the relative standard deviation of this scheme
is about ±6%, i.e., the resultant solid volume fraction is only moderately dependent on the interpolation scheme for the tested
cases. This is further confirmed by a direct intercepting method. Compared to the sophisticated magnetic resonance imaging
(MRI) or the radioactive positron emission particle tracking (PEPT) methods, the present method is verified as a cost-effective
and nonhazardous alternative for ordinary laboratories. Two distinct groups of streamwise dependence of the solid fractions
are found. They are separated by the inclination angle of the chute and agreed with the internal friction angle. In the experiments
using the two smaller inclination angles, the solid fraction ratios are found to be linear functions of the streamwise distance,
while for the two larger inclination angles, the ratios have a nonlinear concave shape. All decrease with growing downstream
distance. 相似文献