全文获取类型
收费全文 | 14756篇 |
免费 | 2420篇 |
国内免费 | 1901篇 |
专业分类
化学 | 10816篇 |
晶体学 | 176篇 |
力学 | 856篇 |
综合类 | 141篇 |
数学 | 1857篇 |
物理学 | 5231篇 |
出版年
2024年 | 95篇 |
2023年 | 332篇 |
2022年 | 533篇 |
2021年 | 531篇 |
2020年 | 607篇 |
2019年 | 595篇 |
2018年 | 478篇 |
2017年 | 388篇 |
2016年 | 681篇 |
2015年 | 671篇 |
2014年 | 853篇 |
2013年 | 1087篇 |
2012年 | 1287篇 |
2011年 | 1275篇 |
2010年 | 929篇 |
2009年 | 784篇 |
2008年 | 903篇 |
2007年 | 866篇 |
2006年 | 788篇 |
2005年 | 721篇 |
2004年 | 535篇 |
2003年 | 474篇 |
2002年 | 498篇 |
2001年 | 437篇 |
2000年 | 306篇 |
1999年 | 299篇 |
1998年 | 272篇 |
1997年 | 241篇 |
1996年 | 256篇 |
1995年 | 214篇 |
1994年 | 200篇 |
1993年 | 168篇 |
1992年 | 139篇 |
1991年 | 126篇 |
1990年 | 91篇 |
1989年 | 94篇 |
1988年 | 64篇 |
1987年 | 42篇 |
1986年 | 37篇 |
1985年 | 46篇 |
1984年 | 45篇 |
1983年 | 23篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 13篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
881.
P. F. Wu J. B. Shi Y. C. Chang M. Z. Tsai Chia‐Tze Kao F. C. Cheng H. W. Lee M. Y. Chen Y. J. Huang R. Y. Huang S. K. Lin 《Crystal Research and Technology》2014,49(11):873-877
Large area and uniform nanosheets Co3O4 have been fabricated by thermal annealing of cobalt thin film under the DC magnetron sputtering method. The synthesis is based on controlling the simple thermal oxidative formation of precursor Co films. The Co films were heated at 300, 400, and 500 °C for two hours in a pure oxygen atmosphere. At 300 °C, CoO and Co3O4 phases appear to survive together. An amount of pure polycrystalline Co3O4 nanosheets were observed at 400 °C. The structural and morphological properties of the nanosheets Co3O4 were characterized by means of transmission electron microscopy (TEM) and Raman spectroscopy. 相似文献
882.
Microchimica Acta - Diethylene glycol (DEG) can be determined in toothpaste via capillary electrophoresis at 16 kV using a fused silica capillary of 75 cm length and of... 相似文献
883.
884.
High‐level theoretical methods (BMK, B3LYP, B98, B3P86, B3PW91, PBE1PBE, PBE1KIS, MPWPW91, MPW1KCIS, TPSS1KCIS, G3, G3//BMK, and CBS‐Q) were utilized to study the carbon–sulfur bond dissociation enthalpies (BDEs) of hydrocarbons in petroleum chemistry. The performance of these methods was evaluated on the basis of a training set including the available experimental BDEs, and it was found that the BMK (Boese‐Martin for Kinetics) method had the best agreement with experimental values. By using the BMK method to calculate C S BDEs of saturated hydrocarbon, the main factors, which determine the changing trend of BDE values, were discussed. Results revealed that the repulsive energies played an important role in determining a change in the trend of BDEs as well as the radical effect. Good agreements were obtained between further calculated BDEs and the experimental ones for C S and C O bonds. Moreover, the same calculation method was applied to predict C S BDEs for which the experimental values were still unavailable. A range of predicted bond dissociation enthalpy values were provided according to the calculations. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:97–105, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20662 相似文献
885.
Shi Y. G. 《Journal of Approximation Theory》1995,82(3)
Existence of a generalized Gaussian Birkhoff quadrature formula is proved for a wide class of incidence matrices which satisfy the delayed Pólya conditions and contain no odd non-Hermitian sequences in the interior rows. 相似文献
886.
887.
A new mercury iodide complex of dppf, [HgI2(dppf)] (adduct 1 , dppf = 1,1‐bis(diphenylphosphino)ferrocene) was prepared and characterized. Single crystal X‐ray diffraction analysis established that the compound crystallizes in the monoclinic system, space group C2c, with a = 34.992(3), b = 10.236(5), c = 18.765(4) Å, β = 99.410(2)°, Z = 8, V = 6631.2(9) Å3. The coordination about the mercury atom is tetrahedral with two equivalent Hg–I and Hg–P bonds. Dppf functions as a chelating ligand. The nonlinear optical (NLO) properties were studied with an 8 ns‐pulsed laser at 532 nm. Its optical responses to the incident light exhibit weak optical absorptive and strong refractive effects, with n2 = 6.86 × 10–18 m2 · W–1 in a 2.48 × 10–4 mol · dm–3 DMF solution. 相似文献
888.
简略介绍了“尾流”效应(wakeeffect)的等离子体模型,并依之模拟计算了1.915MeVH、2.060MeVH在100A碳膜中分解后0°方向的能谱形式。给出了相同条件下的实验结果,将两者做了比较。 相似文献
889.
Zirconia and ultra-high molecular weight polyethylene (UHMWPE) are common materials for artificial joints. However, the failure of artificial joints is mainly caused by the wear of UHMWPE. Therefore, the development of effective measures to enhance the service life of UHMWPE is one of the most important facets of research on total joint replacement. The purpose of this study is to use an atmospheric-pressure plasma system to modify zirconia and UHMPWE surfaces, which is expected to increase the adsorption of joint-lubricating fluids, thus reducing the abrasion and wear of UHMWPE (73% improvement). Surface modification experiments were carried out using an atmospheric-pressure plasma system, while fourier transform infrared spectroscopy was used to characterize the surfaces treated with atmospheric-pressure plasma. The results of water contact angle tests indicated that the plasma-treated material surfaces exhibited excellent hydrophilicity (70% improvement). In addition, the treatment of materials with atmospheric plasma was confirmed to increase the adsorption of lubricating fluid and reduce wear, thus extending the service life of UHMWPE. 相似文献
890.
There are abundant supplies of mixture gases containing CH, and C,H, from natural gas,FCC (Fluidized Catalytic Cracking) dry gas, refinery gas, elc. Commonly, the amount ofC,H, is relatively lower than that of CH,. With regard to the utilization of methane,partial oxidation of methane to syngas over nickel based catalysts has received intensiveallention l'2. For mixture gases containing CH# and C,H,, their conversion to syngas isalso of significance (but has not gained adequate attentio… 相似文献