全文获取类型
收费全文 | 3640篇 |
免费 | 352篇 |
国内免费 | 470篇 |
专业分类
化学 | 1712篇 |
晶体学 | 19篇 |
力学 | 97篇 |
综合类 | 45篇 |
数学 | 1078篇 |
物理学 | 1511篇 |
出版年
2024年 | 15篇 |
2023年 | 43篇 |
2022年 | 142篇 |
2021年 | 158篇 |
2020年 | 168篇 |
2019年 | 119篇 |
2018年 | 112篇 |
2017年 | 122篇 |
2016年 | 106篇 |
2015年 | 112篇 |
2014年 | 175篇 |
2013年 | 331篇 |
2012年 | 177篇 |
2011年 | 204篇 |
2010年 | 164篇 |
2009年 | 228篇 |
2008年 | 223篇 |
2007年 | 241篇 |
2006年 | 209篇 |
2005年 | 163篇 |
2004年 | 129篇 |
2003年 | 137篇 |
2002年 | 106篇 |
2001年 | 110篇 |
2000年 | 131篇 |
1999年 | 88篇 |
1998年 | 77篇 |
1997年 | 64篇 |
1996年 | 58篇 |
1995年 | 42篇 |
1994年 | 31篇 |
1993年 | 33篇 |
1992年 | 19篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 26篇 |
1987年 | 14篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有4462条查询结果,搜索用时 93 毫秒
111.
Dr. Sarvesh K. Srivastava Prof. Dr. Oliver G. Schmidt 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9072-9076
A proof‐of‐concept design for autonomous, self‐propelling motors towards value‐added product synthesis and separation is presented. The hybrid motor design consists of two distinct functional blocks. The first, a sodium borohydride (NaBH4) granule, serves both as a reaction prerequisite for the reduction of vanillin and also as a localized solid‐state fuel in the reaction mixture. The second capping functional block consisting of a graphene–polymer composite serves as a hydrophobic matrix to attract the reaction product vanillyl alcohol (VA), resulting in facile separation of this edible value‐added product. These autonomously propelled motors were fabricated at a length scale down to 400 μm, and once introduced in the reaction environment showed rapid bubble‐propulsion followed by high‐purity separation of the reaction product (VA) by the virtue of the graphene–polymer cap acting as a mesoporous sponge. The concept has excellent potential towards the synthesis/isolation of industrially important compounds, affinity‐based product separation, pollutant remediation (such as heavy metal chelation/adsorption), as well as localized fuel‐gradients as an alternative to external fuel dependency. 相似文献
112.
V. A. Sapozhnikov N. K. Chameeva V. Ya. Mitrofanov A. E. Nikiforov A. N. Men 《光谱学快报》2013,46(11):571-574
The calculation of relative intensities of the optical absorption lines of the fourth order pair of Cr3+ ions in ruby has been performed assuming the electro-dipole character of the transitions. 相似文献
113.
114.
Residence time spectra and material distributions in an operating caprolactam production plant were measured by means of sodium 24, bromine 82 and technetium 99m. The results of the tracerexperiments contributed to an optimization of the plant. 相似文献
115.
Industrially advanced countries and inereasingly also agricultural countries today use radioisotopes as labelled compounds or scaled sources in order to solve their scientific and technological problems. 相似文献
116.
《Journal of Coordination Chemistry》2012,65(18):1719-1726
Three new 2,2′-diamino-4,4′-bithiazole (DABTZ) lead(II) complexes were synthesized and characterized by elemental analyses, IR-, 1H-NMR-, and 13C-NMR-spectroscopy. The single crystal X-ray structural analysis of [Pb(DABTZ)(μ-SCN)(μ-NO3)] n shows the complex to be a 1D chain polymer as a result of sequential thiocyanate and nitrate bridging. The Pb atoms are seven-coordinated by two nitrogen atoms of the 2,2′-diamino-4,4′-bithiazole, three nitrate and two thiocyanate ligands. The arrangement of the 2,2′-diamino-4,4′-bithiazole, nitrate and thiocyanate ligands does not suggest a gap in the coordination around the PbII ion, caused by a stereo-active lone pair of electrons on lead(II) where the coordination around the lead atoms is the less common holodirected. 相似文献
117.
Satyasankar Jana Vivek Arjunan Vasantha Ludger Paul Stubbs Anbanandam Parthiban Julius G. Vancso 《Journal of polymer science. Part A, Polymer chemistry》2013,51(15):3260-3273
Vinylimidazole‐based asymmetric ion pair comonomers ( IPC s) which are free from nonpolymerizable counter ions have been synthesized, characterized and polymerized by free radical polymerization (FRP), atom transfer radical polymerization (ATRP), and reversible addition‐fragmentation chain transfer (RAFT) mediated polymerizations in solution and by dispersion polymerization in water. The asymmetric nature of IPC s is due to the fact that cationic component of these IPCs is derived from vinylimidazole (VIm) and anionic component is derived from either styrenesulfonate (SS) or 2‐acrylamido‐2‐methyl‐1‐propanesulfonate. Although under ATRP, conversions are either very low or negligible, FRP and RAFT produces polymers with high to moderate monomer conversions but with different solubility characteristics. This investigation provides insight to the polymerization behavior of each component of the asymmetric IPCs and also its effects on composition and solubility characteristics of the resulting polymers. The IPCs studied here are high temperature ionic liquid and thus the polymers synthesized from these IPCs are highly ionic in nature and possess very strong intermolecular interactions which makes some of these IPC based polymers completely insoluble in organic and aqueous solvents. This highly ionic interaction is exploited to synthesize ionically crosslinked PMMA. MMA on copolymerization with 5–6 mol % of IPC yielded copolymer which is insoluble in common organic solvents like THF, DMF, etc., unlike homo PMMA. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3260–3273 相似文献
118.
结合新课标要求,揭示塑料薄膜撕扯实验在聚合物教学中的重要性、必要性。通过教学片段设计,发展学生“宏观辨识与微观探析、证据推理与模型认知”化学学科核心素养,并让学生认识物质的性能不仅取决于结构,也取决于生产工艺。并对人教版初、高中化学教材和教参中相关问题展开讨论和解释,以期更好地服务教学。 相似文献
119.
Dr. Xu Guo Xing Liu Prof. Junqing Yan Prof. Shengzhong Frank Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(69):e202202662
Solar-driven water splitting to produce clean and renewable hydrogen offers a green strategy to address the energy crisis and environmental pollution. Heterostructure catalysts are receiving increasing attention for photocatalytic hydrogen generation. ZnO/ZnS/CdS and ZnO/CdS heterostructures have been successfully designed and prepared according to two different strategies. By introducing a heterointerface layer of ZnS between ZnO and CdS, a Z scheme charge-transfer channel was promoted and achieved superior photocatalytic performance. A highest hydrogen generation rate of 156.7 μmol g−1 h−1 was achieved by precise control of the thickness of the heterointerface layer and of the CdS shell. These findings demonstrated that heterostructures are promising catalysts for solar-driven water splitting, and that heterointerface engineering is an effective way to improve the photocatalytic properties of heterostructures. 相似文献
120.
Dr. Christoph Ludwig Teske Dr. Anna-Lena Hansen Prof. Dr. Richard Weihrich Prof. Dr. Lorenz Kienle Marius Kamp Kasper Pieter van der Zwan Prof. Dr. Jürgen Senker Dr. Carsten Dosche Prof. Dr. Gunther Wittstock Prof. Dr. Wolfgang Bensch 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(27):6763-6772
A new preparation route is developed for the synthesis of needle-like crystals of [Au(S2CNH2)2]SCN, which avoids disproportionation of the AuI salt used as a starting material. In the crystal structure, the two crystallographically independent AuIII centers are in a square-planar environment of two S2CNH2 ligands. The Hirshfeld surface analysis reveals the presence of noncovalent intermolecular S⋅⋅⋅S interactions, which are essential for the spatial arrangement of the molecules. Density functional theory (DFT) calculations including dispersion and damping corrections result in a unit cell volume very close to the value determined experimentally. Thermal decomposition in an inert atmosphere generates black needles with lengths of up to 500 μm. X-ray powder diffraction and pair distribution function analyses demonstrate that the needles are composed of nanosized crystals with a volume-weighted average domain size of 20(1) nm. According to results of X-ray photoemission experiments, the black needles are covered by a nitrogen-rich carbon nitride with composition near (CN)2N. 13C solid-state NMR investigations indicate that two different carbon species are present, with signals corresponding well to heptazine units as in melon and triazine units as in poly(triazin imide) type compounds. Scanning transmission electron microscopy tomography evidences that the needles are composed of slightly elongated nanoparticles. 相似文献