全文获取类型
收费全文 | 106158篇 |
免费 | 17865篇 |
国内免费 | 12655篇 |
专业分类
化学 | 74874篇 |
晶体学 | 1180篇 |
力学 | 6051篇 |
综合类 | 770篇 |
数学 | 13532篇 |
物理学 | 40271篇 |
出版年
2024年 | 107篇 |
2023年 | 2091篇 |
2022年 | 2351篇 |
2021年 | 3384篇 |
2020年 | 4353篇 |
2019年 | 4162篇 |
2018年 | 3775篇 |
2017年 | 3443篇 |
2016年 | 5121篇 |
2015年 | 5037篇 |
2014年 | 6203篇 |
2013年 | 8061篇 |
2012年 | 9735篇 |
2011年 | 10107篇 |
2010年 | 7143篇 |
2009年 | 6896篇 |
2008年 | 7244篇 |
2007年 | 6475篇 |
2006年 | 6025篇 |
2005年 | 5006篇 |
2004年 | 3937篇 |
2003年 | 3100篇 |
2002年 | 2701篇 |
2001年 | 2296篇 |
2000年 | 1930篇 |
1999年 | 2096篇 |
1998年 | 1767篇 |
1997年 | 1586篇 |
1996年 | 1577篇 |
1995年 | 1426篇 |
1994年 | 1303篇 |
1993年 | 1051篇 |
1992年 | 945篇 |
1991年 | 813篇 |
1990年 | 674篇 |
1989年 | 524篇 |
1988年 | 401篇 |
1987年 | 352篇 |
1986年 | 348篇 |
1985年 | 283篇 |
1984年 | 196篇 |
1983年 | 160篇 |
1982年 | 127篇 |
1981年 | 82篇 |
1980年 | 60篇 |
1979年 | 25篇 |
1978年 | 22篇 |
1976年 | 22篇 |
1975年 | 22篇 |
1957年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Qiang Li 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(1):65-68
The title compound, (C20H20P)[Cd(C2N3)3], consists of ethyltriphenylphosphonium (EtPh3P+) cations filling voids in a three‐dimensional anionic cadmium dicyanamide network. In the structure, each CdII atom is connected to six neighbouring CdII atoms through six separate dicyanamide ligands, forming cube‐shaped cages. The three‐dimensional anionic network encloses a solvent‐accessible void space of 1851 Å3, amounting to 69.3% of the unit‐cell volume. Each cage accommodates only one EtPh3P+ cation. 相似文献
992.
采用微波消解技术,建立了一种电感耦合等离子体质谱法测定明胶空心胶囊中Cr,Co,Ni,Cu,Zn,As,Cd,Hg和Pb 9种微量重金属元素的方法。确定了微波消解仪和等离子体质谱仪的最佳操作参数,研究共存离子的干扰和消除方法,选择了各元素的测定同位素,以Ge,Rh和Tl为内标补偿基体效应,建立了样品测定方法。应用拟定的方法测定了不同生产厂家、不同批次的空心胶囊中微量重金属的含量。方法对试样中各元素测定的相对标准偏差为1.5%~14.1%,加标回收率在90.0%~102.0%。结果表明,方法简便、快速、灵敏,满足于空心胶囊中9种重金属元素的测定要求。 相似文献
993.
Dr. Junhong Zhao Youjuan Zhang Zhen Run Pengwei Li Qifei Guo Prof. Huan Pang 《ChemistryOpen》2015,4(3):274-277
Uniformly sized and shape-controlled nanoparticles are important due to their applications in catalysis, electrochemistry, ion exchange, molecular adsorption, and electronics. Several ferric phosphate hydroxide (Fe4(OH)3(PO4)3) microstructures were successfully prepared under hydrothermal conditions. Using controlled variations in the reaction conditions, such as reaction time, temperature, and amount of hexadecyltrimethylammonium bromide (CTAB), the crystals can be grown as almost perfect hyperbranched microcrystals at 180 °C (without CTAB) or relatively monodisperse particles at 220 °C (with CTAB). The large hyperbranched structure of Fe4(OH)3(PO4)3 with a size of ∼19 μm forms with the “fractal growth rule” and shows many branches. More importantly, the magnetic properties of these materials are directly correlated to their size and micro/nanostructure morphology. Interestingly, the blocking temperature (TB) shows a dependence on size and shape, and a smaller size resulted in a lower TB. These crystals are good examples that prove that physical and chemical properties of nano/microstructured materials are related to their structures, and the precise control of the morphology of such functional materials could allow for the control of their performance. 相似文献
994.
Nanomaterials with both superhydrophobic surface properties as well as photocatalytic activities could have important industrial applications. Herein, we synthesized CeVO4 nanocrystals with hexagonal nanoplate structures from the reaction of decavanadate (K6V10O28⋅9 H2O) and CeCl3⋅H2O precursors via a hydrothermal method. This synthetic route has four advantages: 1) the reaction condition is relatively mild, 2) it doesn′t need surfactants or templates, 3) it requires no expensive equipment, and 4) products are of higher purity. During synthesis, solution pH, and reaction temperature were found to play important roles in determining the growth process and final morphologies of the CeVO4 products. These products were characterized spectrophotometrically and via scanning and transmission electron microscopy. Furthermore, the wettability of the as-synthesized film CeVO4 nanoplates was studied by measuring water contact angle (CA). The largest CA measured was at 169.5 ° for a glass substrate treated with 0.06 g mL−1 CeVO4 followed by 2 % 1 H, 1 H, 2 H, 2 H-perfluorodecyltriethoxysilane. Finally, the CeVO4 nanoplates exhibited excellent photocatalytic activity in degradation of rhodamine B (RhB) under UV irradiation and was stable even after repeated cycles of use. 相似文献
995.
Jiaolong Chen Peijin Li Swadesh Kumar Sahoo Xiantao Wang 《Israel Journal of Mathematics》2017,220(1):453-478
We first investigate the Lipschitz continuity of (K,K’)-quasiregular C 2 mappings between two Jordan domains with smooth boundaries, satisfying certain partial differential inequalities concerning Laplacian. Then two applications of the obtained result are given: As a direct consequence, we get the Lipschitz continuity of ρ-harmonic (K,K’)-quasiregular mappings, and as the other application, we study the Lipschitz continuity of (K,K’)- quasiconformal self-mappings of the unit disk, which are the solutions of the Poisson equation Δw = g. These results generalize and extend several recently obtained results by Kalaj, Mateljevi? and Pavlovi?. 相似文献
996.
997.
We consider three special cases of the initial value problem of the first Painlevé (PI) equation. Our approach is based on the method of uniform asymptotics introduced by Bassom et al. A rigorous proof of a property of the PI solutions on the negative real axis, recently revealed by Bender and Komijani, is given by approximating the Stokes multipliers. Moreover, we build more precise relation between the large initial data of the PI solutions and their three different types of behavior as the independent variable tends to negative infinity. In addition, some limiting form connection formulas are obtained. 相似文献
998.
In this paper, we consider strict comparison theorems in the framework of G-expectation, which is a type of sublinear expectation associated with fully nonlinear parabolic partial differential equations. In particular, we first apply Krylov–Safonov estimates to establish the strict comparison theorem for functions from the Lipschitz class \(Lip(\Omega )\). Then we prove generalized strict comparison theorems on the enlarged space \(L_G^1(\Omega )\), which is the Banach completion of \(Lip(\Omega )\) under the G-expectation. 相似文献
999.
In this paper, we give some estimates for the essential norm and a new characterization for the boundedness and compactness of weighted composition operators from weighted Bergman spaces and Hardy spaces to the Bloch space. 相似文献
1000.
Zhi-Wei Li 《Czechoslovak Mathematical Journal》2017,67(2):329-337
We show that there is a model structure in the sense of Quillen on an arbitrary Frobenius category F such that the homotopy category of this model structure is equivalent to the stable category F as triangulated categories. This seems to be well-accepted by experts but we were unable to find a complete proof for it in the literature. When F is a weakly idempotent complete (i.e., every split monomorphism is an inflation) Frobenius category, the model structure we constructed is an exact (closed) model structure in the sense of Gillespie (2011). 相似文献