全文获取类型
收费全文 | 15204篇 |
免费 | 2570篇 |
国内免费 | 1859篇 |
专业分类
化学 | 11555篇 |
晶体学 | 184篇 |
力学 | 780篇 |
综合类 | 99篇 |
数学 | 1384篇 |
物理学 | 5631篇 |
出版年
2024年 | 29篇 |
2023年 | 270篇 |
2022年 | 514篇 |
2021年 | 513篇 |
2020年 | 639篇 |
2019年 | 636篇 |
2018年 | 549篇 |
2017年 | 462篇 |
2016年 | 742篇 |
2015年 | 701篇 |
2014年 | 836篇 |
2013年 | 1180篇 |
2012年 | 1361篇 |
2011年 | 1351篇 |
2010年 | 932篇 |
2009年 | 938篇 |
2008年 | 1047篇 |
2007年 | 945篇 |
2006年 | 849篇 |
2005年 | 761篇 |
2004年 | 615篇 |
2003年 | 523篇 |
2002年 | 569篇 |
2001年 | 395篇 |
2000年 | 291篇 |
1999年 | 302篇 |
1998年 | 248篇 |
1997年 | 222篇 |
1996年 | 200篇 |
1995年 | 168篇 |
1994年 | 140篇 |
1993年 | 110篇 |
1992年 | 107篇 |
1991年 | 102篇 |
1990年 | 71篇 |
1989年 | 57篇 |
1988年 | 40篇 |
1987年 | 32篇 |
1986年 | 34篇 |
1985年 | 34篇 |
1984年 | 20篇 |
1983年 | 16篇 |
1982年 | 14篇 |
1981年 | 17篇 |
1980年 | 9篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Theoretical Investigation of Detailed Thermodynamic Character of Possible Difunctional Adducts Model
CHANG Guan-Ru ZHOU Li-Xin ② CHEN Dong 《结构化学》2006,25(5):533-542
1 INTRODUCTION Since cisplatin was recognized as an active sub- stance in the antitumor treatment in 1960s, many studies have been devoted to the exploitation of pla- tinum complexes, focusing on the influence of dif- ferent ligands and conformers on the cancer acti- vity[1~7]. Thousands of Pt complexes evaluated for antitumor activity adhered to the set of structure- activity relationship summarized by Cleare and Ho- eschele[1, 8], for instance, cispaltin, carboplatin and oxaliplatin pos… 相似文献
932.
Heung Jae Lee Dong Seok Kim Min Chul Suh Sang Chul Shim 《Journal of polymer science. Part A, Polymer chemistry》1996,34(16):3255-3261
2,4-Hexadiyn-1,6-diol (HDO) was polymerized on glass and silicon plates by chemical vapor deposition without transition metal catalysis to form homogeneous thin films. Structural properties of the films were investigated by FT-IR, UV-visible, Raman, x-ray diffraction, and XPS spectroscopic analyses. The structure of CVD-polymerized HDO (CVD-PHDO) films was different from that of metathesis polymerized HDO (metathesis-PHDO), showing a polyacene-based structure but no polyene structure with acetylenic side groups. © 1996 John Wiley & Sons, Inc. 相似文献
933.
Haidong Zhang Zeneng Sun Chengguo Liu Shurui Dong Yuanyuan Shao Jesse Zhu 《Particuology》2021,(2):1-15
The effects of internals and gas distributors on the local dynamics of the bubbles in the conventional gas-solid fluidized bed were studied.Mesh-type internals with different opening areas(50%,70%and 90%)and different arrangements(two-layer and four-layer);and a sintered plate with a smaller pore size(1μm)and a perforated plate with a larger pore size as distributors were investigated.Differential pressure drops and local solids holdups were measured under various superficial gas velocities to compare the performances of the different types of internals and distributors.The instantaneous solids holdup signals from the optical fibre probe were used to further examine the local bubble dynamics in detail.Smaller bubbles were found,with the installation of internals or using the sintered plate,resulting in lower pressure drops and a higher bed expansion.Internals with reduced opening area or distributor with smaller pore size further leads to a higher changeover rate between the bubbles and dense phase,both axially and radially,and hence a better gas-solid contacting and an earlier transition to the turbulent flow regime of the bed. 相似文献
934.
Li-Zhao Huang Yue Shui Wei Chen Zhong-Ming Li Hong-Tao Song Guang-Ai Sun Jia-Zhuang Xu Gan-Ji Zhong Dong Liu 《高分子科学》2021,39(3):365-376
The correlation between aggregates and bound rubber structures in silicone rubbers(S(phr)) with various silica fractions(ΦSi) has been investigated by contrast matching small-angle neutron scattering(SANS), swelling kinetics, and low-field nuclear magnetic resonance(NMR).Mixed solvents with deuterated cyclohexane fractions of 4.9% and 53.7% were chosen to match the scattering length densities of the matrix(SMP(phr)) and the filler(SMS(phr)), respectively. All the data consistently suggest that:(i) There is a critical threshold ΦSic between 10 and 30 phr;below ΦSic, the isolated aggregates are dominant, while beyond ΦSic, some rubber fraction is trapped among the agglomerate;(ii) ΦSiindependent thicknesses around 7.5 nm(NMR) and 8.6 nm(SANS) suggest that the bound rubber formation is determined by inherent properties of the components, and the power-law around 4.2 suggests an exponential changed gradient density of the bound rubber;(iii) SMS(80) presents a bicontinuous bound rubber with three characteristic lengths of 41, 100, and 234 nm. The expanded correlation length, a 20 nm smaller aggregate sizes suggest that such existent bicontinuous network in dry samples with less ΦSi is kind of impacted by swelling. With the obtained bound rubber models, the reinforcing mechanism of filled silicone rubber is elucidated. 相似文献
935.
Dong-Zhao Yang Zhen-Zhen Chen Mei Chi Ying-Ying Dong Shou-Zhi Pu Qi Sun 《Molecules (Basel, Switzerland)》2022,27(3)
5-Hydroxymethyl-2′-deoxycytidine (5hmdC) phosphoramidite and triphosphate are important building blocks in 5hmdC-containing DNA synthesis for epigenetic studies. However, efficient and practical methods for the synthesis of these compounds are still limited. The current research provides an intensively improved synthetic method that enables the preparation of commercially available cyanoethyl-protected 5hmdC phosphoramidite with an overall yield of 39% on 5 g scale. On the basis of facile and efficient accesses to cyanoethyl protected-5hmdU and 5hmdC intermediates, two efficient synthetic routes for 5hmdC triphosphate were also developed. 相似文献
936.
The growth rates of crystal interfaces have been measured by using a new technique — the laser diffraction metering technique. It is simple, visualized, fast and has high precision. This paper describes the basic principle, operation method and the precision of the technique. 相似文献
937.
938.
以钨酸(H2WO4)为钨前驱体,十二烷胺(DDA)为模板剂,利用模板剂的结构导向功能,合成了比表面积为57.3 m2·g-1的介孔三氧化钨(DDA-WO3),是未用DDA制备的非介孔WO3(H2WO4-WO3)的2.35倍。X射线衍射(XRD)结果表明,400 ℃下煅烧的DDA-WO3是具有单斜晶型结晶孔壁的无序介孔结构。此外,400~550 ℃下煅烧的DDA-WO3的结晶度均高于同条件的H2WO4-WO3。400 ℃下的DDA-WO3/FTO(掺氟氧化锡)在1.0 V的Ag/AgCl偏压作用下,可以产生0.18 mA·cm-2的饱和光电流,是H2WO4-WO3/FTO(0.06 mA·cm-2)的3倍。增强的光电化学(PEC)活性主要因为DDA-WO3/FTO的大表面积降低了低结晶度对PEC性能的不利影响,成为影响PEC活性的主要因素。500 ℃煅烧导致了DDA-WO3/FTO介孔结构的坍塌,但高的结晶度仍然保持其优越的PEC催化活性。 相似文献
939.
Nonlinear Dynamics - It is an effective way to improve network robustness by adding connectivity links. Although some addition strategies have been proposed, the addition cost in spatial networks... 相似文献
940.
Nonlinear Dynamics - This paper proposes the consensus tracking control problem for a class of uncertain nonlinear multi-agent systems. By using a group of nonnegative functions, an adaptive neural... 相似文献