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991.
欧劲松李蓉尹辉王华建 《应用数学和力学》2023,(5):513-524
针对二连杆柔性关节机械臂,提出了一种基于奇异摄动理论和Udwadia-Kalaba(U-K)方法的控制方法.设计步骤主要分为两步:第一,基于奇异摄动法对系统进行降阶,把系统拆分为快、慢系统,不仅降低了求解系统的阶次,而且克服了系统柔性;第二,基于U-K方法设计了快、慢系统的状态反馈约束跟随控制律,能使快、慢系统约束跟随误差收敛到零,即使系统初始不满足约束条件,该方法不需要借助Lagrange乘子和伪广义速度等辅助变量,可以同时处理完整约束和非完整约束.将以上方法运用在二连杆柔性关节机械臂系统中,解决了二连杆柔性关节机械臂的柔性振荡和约束跟随的问题.使用MATLAB进行仿真,并且与传统PID控制进行了对比,验证了所提出的方法的有效性与优越性. 相似文献
992.
Sessler JL Karnas E Kim SK Ou Z Zhang M Kadish KM Ohkubo K Fukuzumi S 《Journal of the American Chemical Society》2008,130(46):15256-15257
A new supramolecular system, consisting of an expanded porphyrin, cyclo[8]pyrrole (C8) and a pyrene carboxylate (Py) is capable not only of electron transfer upon photoexcitation, but results in "umpolung" or a reversal of the predicted charge-separation behavior in that the higher energy radical ion pair, C8.+-Py.- (2.58 eV) is formed as opposed to C8.--Py.+ (1.31 eV). This observation is rationalized in terms of the latter radical ion pair, C8.--Py.+ being in the Marcus inverted region. Transient absorption spectral studies reveal a charge-separated lifetime of 300 micros, which decays to the triplet state of cyclo[8]pyrrole, also an exceedingly long-lived species. The novel features of this noncovalent dyad highlight the potential utility of anion binding in the construction of supramolecular electron transfer systems. 相似文献
993.
Jiaxiao Yuan Xiaomin Zhang Dawei Zhou Feixiang Ge Jingxian Zhong Sihan Zhao Zhenwei Ou Guixiang Zhan Xu Zhang Congzhou Li Jin Tang Qi Bai Junran Zhang Chao Zhu Ti Wang Longfei Ruan Chongqin Zhu Xuefen Song Wei Huang Lin Wang 《Angewandte Chemie (International ed. in English)》2023,62(19):e202218546
The liquid-air interface offers a platform for the in-plane growth of free-standing materials. However, it is rarely used for inorganic perovskites and ultrathin non-layered perovskites. Herein the liquid-air interfacial synthesis of inorganic perovskite nanosheets (Cs3Bi2I9, Cs3Sb2I9) is achieved simply by drop-casting the precursor solution with only the addition of iodine. The products are inaccessible without iodine addition. The thickness and lateral size of these nanosheets can be adjusted through the iodine concentration. The high volatility of the iodine spontaneously drives precursors that normally stay in the liquid to the liquid-air interface. The iodine also repairs in situ iodine vacancies during perovskite growth, giving enhanced optical and optoelectronic properties. The liquid-air interfacial growth of ultrathin perovskites provides multi-degree-of-freedom for constructing perovskite-based heterostructures and devices at atomic scale. 相似文献
994.
Dr. Yufei Zhao Ziyan Shen Dr. Juanjuan Huo Dr. Xianjun Cao Dr. Pengfei Ou Junpeng Qu Prof. Xinming Nie Dr. Jinqiang Zhang Prof. Minghong Wu Prof. Guoxiu Wang Prof. Hao Liu 《Angewandte Chemie (International ed. in English)》2023,62(36):e202308349
Electrocatalysts for highly efficient oxygen reduction reaction (ORR) are crucial for energy conversion and storage devices. Single-atom catalysts with maximized metal utilization and altered electronic structure are the most promising alternatives to replace current benchmark precious metals. However, the atomic level understanding of the functional role for each species at the anchoring sites is still unclear and poorly elucidated. Herein, we report Fe single atom catalysts with the sulfur and oxygen functional groups near the atomically dispersed metal centers (Fe1/NSOC) for highly efficient ORR. The Fe1/NSOC delivers a half-wave potential of 0.92 V vs. RHE, which is much better than those of commercial Pt/C (0.88 V), Fe single atoms on N-doped carbon (Fe1/NC, 0.89 V) and most reported nonprecious metal catalysts. The spectroscopic measurements reveal that the presence of sulfur group induces the formation of epoxy groups near the FeN4S2 centers, which not only modulate the electronic structure of Fe single atoms but also participate the catalytic process to improve the kinetics. The density functional theory calculations demonstrate the existence of sulfur and epoxy group engineer the charges of Fe reactive center and facilitate the reductive release of OH* (rate-limiting step), thus boosting the overall oxygen reduction efficiency. 相似文献
995.
Dr. Mingruo Ding Pengcheng Ou Xuening Li Yinghua Yu Mengmeng Niu Yongjian Yang Yewei Huang Prof. Dr. Zhi-Xiang Wang Prof. Dr. Xueliang Huang 《Angewandte Chemie (International ed. in English)》2023,62(18):e202300703
“Through space” palladium/hydrogen shift is an efficient strategy to achieve selective functionalization of a specific remote C−H bond. Compared with relatively extensive exploited 1,4-palladium migration process, the relevant 1,5-Pd/H shift was far less investigated. We herein report a novel 1,5-Pd/H shift pattern between a vinyl and an acyl group. Through the pattern, rapid access to 5-membered-dihydrobenzofuran and indoline derivatives has been achieved. Further studies have unveiled an unprecedented trifunctionalization (vinylation, alkynylation and amination) of a phenyl ring through 1,5-palladium migration relayed decarbonylative Catellani type reaction. A series of mechanistic investigations and DFT calculations have provided insights into the reaction pathway. Notably, it was unveiled that the 1,5-palladium migration in our case prefers a stepwise mechanism involving a PdIV intermediate. 相似文献
996.
We proved the existence of convex solution to a class of fully nonlinear elliptic equations with second boundary condition on uniformly convex domains in \(\mathbb {R}^{n}\), and then applied it to solve a boundary value problem for minimal Lagrangian graphs in the pseudo-Euclidean space \(\mathbb {R}^{2n}_n\). 相似文献
997.
Haiyang Zhang Junjie Ou Yinmao Wei Hongwei Wang Zhongshan Liu Lianfang Chen Hanfa Zou 《Analytica chimica acta》2015
Low column efficiency for small molecules in reversed-phase chromatography is a major problem commonly encountered in polymer-based monoliths. Herein, a novel highly crosslinked porous polymeric monolith was in situ prepared by using a multi-acrylate monomer, dipentaerythritol penta-/hexa-acrylate (DPEPA), as crosslinker, which copolymerized with lauryl methacrylate (LMA) as functional monomer in a UV-transparent fused-silica capillary via photo-initiated free-radical polymerization within 5 min. The mechanical stability and permeability of the resulting poly(LMA-co-DPEPA) monolith were characterized in detail. One series of highly crosslinked poly(LMA-co-DPEPA) columns were prepared with relatively higher content of crosslinker (63.3%) in the precursor. Although they exhibited lower permeability, high column efficiency for alkylbenzenes was acquired in cLC, and the minimum plate height (column B) was in the range of 6.04–9.00 μm, corresponding to 111,000–165,000 N m−1. Meanwhile, another series of poly(LMA-co-DPEPA) columns prepared with relatively lower content of crosslinker (52.7%) in the precursor exhibited higher permeability, but the minimum plate height (column E) was relatively low in the range of 10.75–20.04 μm for alkylbenzenes, corresponding to 50,000–93,000 N m−1. Compared with common poly(LMA-co-EDMA) columns previously reported, the highly crosslinked poly(LMA-co-DPEPA) columns using a multi-acrylate monomer as crosslinker possessed remarkably high column efficiency for small molecules in cLC. By plotting of plate height (H) of alkylbenzenes versus the linear velocity (u) of mobile phase, the results revealed a retention-independent efficient performance of small molecules in the isocratic elution, indicating that the use of multi-functional crosslinker possibly prevents the generation of gel-like micropores in the poly(LMA-co-DPEPA) monolith, reducing the mass transfer resistance (C-term). 相似文献
998.
纳米TiO2修饰的La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)阴极被直接应用于YSZ电解质电池上. TiO2可阻止LSCF和YSZ间的化学反应,抑制SrZrO3的形成. LSCF-0.25 wt% TiO2阴极电池在0.7 V和600°C下的电流密度是LSCF阴极电池的1.6倍.电化学阻抗谱结果表明, TiO2修饰显著加快了氧离子注入电解质的过程,这可能与TiO2抑制了阴极/电解质界面处高电阻SrZrO3层的形成有关.本文为在ZrO2基电解质上使用高性能的(La,Sr)(Co,Fe)O3阴极材料提供了一种简单有效的方法. 相似文献
999.
1000.
There are several barriers to gene delivery. One of the biggest challenges is the design of appropriate vectors. Currently, nonviral vectors have received significant attention because of low toxicity, potential for tissue specificity, stability during storage, lack of immunogenicity, and relatively low production cost. Despite the high efficiency of viral vectors, they show limited clinical applications because of potentially fatal adverse effects and because of the likelihood of the immune response shutting down the transgene expression system. Nonviral technologies comprise plasmid‐based expression systems harboring a gene that encodes a therapeutic protein along with a synthetic gene delivery system. This review provides a broad perspective on recent improvements in the development of four kinds of nonviral vectors that are based on polymers, peptides, lipids, and DNA and discusses the cytotoxicity associated with gene therapy. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献