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971.
Adulteration of herbal supplements with synthetic drugs is illegal. A rapid and reliable method which utilizes direct analysis in real time mass spectrometry (DART-MS) was developed for the identification of seven synthetic antidiabetic drugs used as adulterants in herbal dietary supplements. The supplement sample was simply extracted with methanol/water by manually shaking several times and directly analyzed using DART-MS. The presence of synthetic drug adulterants was confirmed through the accurate m/z values and MS/MS data obtained via quadruple time of flight mass spectrometry (QTOF MS). Parameters for the DART source were systematically optimized, and the limits of detection (LODs) in herbal supplement matrices were measured. This method was successfully applied to examine five commercial herbal dietary supplements, and two of them proved to be adulterated with metformin without labeling. 相似文献
972.
A simple molecular mechanics force field for graphene (PPBE-G) was created by force matching the density functional theory Perdew-Burke-Ernzerhof forces using the adaptive force matching method recently developed in our group. The PPBE-G potential was found to provide significantly more accurate forces than other existing force fields. Several properties of graphene, such as Young's modulus, bending rigidity, and thermal conductivity, have been studied with our potential. The calculated properties are in good agreement with corresponding density functional theory and experimental values. The thermal conductivity calculated with reverse non-equilibrium molecular dynamics depends sensitively on graphene size thus requiring the simulation of large sheets for convergence. Since the PPBE-G potential only contains simple additive energy expressions, it is very computationally efficient and is capable of modeling large graphene sheets in the μm length scale. 相似文献
973.
Chen L Han X Yang J Zhou J Song W Zhao B Xu W Ozaki Y 《Journal of colloid and interface science》2011,360(2):482-487
We have employed the proposed Silica-Silver Core-Shell (SSCS) SERS-active substrates to detect four model proteins: lysozyme (a protein without chromophore), cytochrome c (a protein with chromophore of heme), fluorescein isothiocyanate (FITC)-anti human IgG (labeled with FITC) and atto610-biotin/avidin (recognition with labeled small molecules). SERS spectra of these proteins and Raman labels on the SSCS substrates show both high sensitivity and reproducibility, which are due to electromagnetic SERS enhancement with additional localization field within closely packed Ag nanoparticles decorated on the SiO(2) nanoparticles and the aggregation of SiO(2)@Ag particles. We have found that the SERS intensities of atto610-biotin/avidin adsorbed on the SSCS substrates are about 20 times stronger than those from Ag plating on Au-decorated substrate. Moreover, the broad surface plasmon resonance (SPR) of the proposed substrates will extend SERS applications to more biological molecules with different laser excitations. 相似文献
974.
提出了应用气相色谱法与顶空固相微萃取样品预处理技术相结合的方法测定饮用水中2,4,6-三氯酚(TCP)和五氯酚(PCP)。选用20mL顶空瓶,其中预置0.1mol·L~(-1)盐酸溶液0.5mL及氯化钠4.0g,加入水样10.0mL,立即封盖。插入85μm聚丙烯酸酯萃取头,在500r·min~(-1)转速振荡条件下于60℃萃取40 min,随之进入色谱仪解吸并测定。测定中采用HP-5毛细管柱和程序升温(40℃~280℃)条件,并用载气流量为3mL·min~(-1)。测得2,4,6-TCP及PCP的线性范围依次为55μg·L~(-1)和12μg·L~(-1)以内,其检出限(3S/N)依次为0.15μg·L~(-1)和0.13μg·L~(-1),加入3个浓度水平的标准溶液对方法的回收率及精密度作了试验,测得回收率在90.0%~112.8%之间,相对标准偏差(n=6)在3.0%~4.9%之间。 相似文献
975.
Wen-Hua Zhang Xiu-Bao Wei Ping-Ning Jin Jun-Feng Kou Guang Yang 《Transition Metal Chemistry》2011,36(5):459-463
Reactions of 3(5)-methyl-5(3)-phenyl-1H-1,2,4-triazole (3-Me-5-Ph-tzH) with AgNO3 in the absence/presence of NH3 yield a mononuclear [Ag(3-Me-5-Ph-tzH)2]NO3·3H2O (1) and a polymeric [Ag(3-Me-5-Ph-tz)]n (2), respectively. Two structurally different infinite chains, however, with the same formula of AgC9H8N3—one is double-decked and the other single zigzag—coexist in 1:1 ratio in the crystal of 2. As far as we know, 2 is the first binary silver(I) complex based on an asymmetric triazole and represents a rare case of two supramolecular isomers coexisting in the same crystal. 相似文献
976.
977.
重型汽车制动器管在潮湿的环境中使用时发生破裂,采用化学成分分析、力学性能试验、断口分析和金相分析等方法对破裂的制动器管进行分析.结果表明,制动器管的裂纹主要产生于存在加工应力的弯曲部位,应力腐蚀是造成其破裂的主要原因.同时在选材方面提出建议. 相似文献
978.
Liqiang Tan Yeling Jin Xiaochun Cheng Jie Wu Wei Zhou Liangdong Feng 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(3):575-585
Batch sorption experiments were performed to remove Eu(III) ions from aqueous solutions by using attapulgite under ambient
conditions. Different experimental conditions, such as contact time, solid content, foreign ions, pH, ionic strength, fulvic
acid and temperature, have been investigated to study their effect on the sorption property. The results indicated that the
sorption of Eu(III) onto attapulgite was strongly dependent on pH, ionic strength and temperature. The sorption increased
from about 8.9 to 90% at pH ranging from 2 to 6 in 0.01 mol/L NaNO3 solution. The Eu(III) kinetic sorption on attapulgite was fitted by the pseudo-second-order model better than by the pseudo-first-order
model. The sorption of Eu(III) onto attapulgite increased with increasing temperature and decreasing ionic strength. The Langmuir
and Freundlich models were used to simulate the sorption isotherms, and the results indicated that the Freundlich model simulated
the data better than the Langmuir model. The thermodynamic parameters (∆G
o, ∆S
o, ∆H
o) were determined from the temperature dependent isotherms at 298.15, 318.15 and 338.15 K, and the results indicated that
the sorption reaction was an endothermic and spontaneous process. The results suggest that the attapulgite is a suitable material
as an adsorbent for preconcentration and immobilization of Eu(III) from aqueous solutions. 相似文献
979.
Yong-Sheng Jin Jing-Ling Du Yan Yang Li Jin Yan Song Wei Zhang Hai-Sheng Chen 《Chemistry of Natural Compounds》2011,47(2):257-260
A new natural product (N-acetyltryptophan), together with 22 known constituents, including seven alkaloids, six flavonoids, six organic acids, and
other compounds, were isolated from Salsola collina Pall. Their structures were elucidated on the basis of chemical reaction and spectral evidence. Among the isolated compounds,
N-acetyltryptophan (8) showed moderate inhibition of a-amylase activity, and terrestric acid (9) showed positive antifungal activity. 相似文献
980.