全文获取类型
收费全文 | 543篇 |
免费 | 270篇 |
国内免费 | 193篇 |
专业分类
化学 | 379篇 |
晶体学 | 13篇 |
力学 | 33篇 |
综合类 | 36篇 |
数学 | 186篇 |
物理学 | 359篇 |
出版年
2024年 | 2篇 |
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 17篇 |
2019年 | 14篇 |
2018年 | 13篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 29篇 |
2012年 | 31篇 |
2011年 | 35篇 |
2010年 | 38篇 |
2009年 | 39篇 |
2008年 | 48篇 |
2007年 | 49篇 |
2006年 | 57篇 |
2005年 | 58篇 |
2004年 | 57篇 |
2003年 | 40篇 |
2002年 | 33篇 |
2001年 | 44篇 |
2000年 | 50篇 |
1999年 | 27篇 |
1998年 | 20篇 |
1997年 | 29篇 |
1996年 | 20篇 |
1995年 | 22篇 |
1994年 | 12篇 |
1993年 | 20篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 16篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1973年 | 1篇 |
排序方式: 共有1006条查询结果,搜索用时 15 毫秒
1.
2.
Enyuan Wang Xiangguo Kong Shaobin Hu Zhonghui Li Quanlin Liu 《Transport in Porous Media》2018,121(3):703-724
With coal mining entering the geological environment of “high stress, rich gas, strong adsorption and low permeability,” the difficulty of joint coal and gas extraction clearly augments, the risk of solid–gas coupling dynamic disasters greatly increases, and the underlying mechanisms become more complex. In this paper, based on the characteristics of coal’s multi-scale structure and spatiotemporal variation, the multi-scale fractured coal gas–solid coupling model (MSFM) was built. In this model, the interaction between coal matrix and its fractures and the mechanical characteristics of gas-bearing coal were considered, as well as their coupling relationship. By MATLAB software, the stress–damage–seepage numerical computation programs were developed, which were applied into Comsol Multiphysics to simulate gas flow caused by coal mining. The simulation results showed the spatial variability of coal elastic modulus and cross-flow behaviors of coal seam gas, which were superior to the results of traditional gas–solid coupling model. And the numerical results obtained from MSFM were closer to the measured results in field, while the computation results of traditional model were slightly higher than the measured results. Furthermore, the MSFM in a large scale was verified by field engineering project. 相似文献
3.
水火联合调度问题是电力系统中一类复杂的优化问题。合理安排调度周期内的水火电出力,确定一个最优发电计划,可以带来巨大的经济效益。在实际系统中,汽轮机调汽阀开启时出现的拔丝现象会使机组耗量特性产生阀点效应。忽略阀点效应,在一定程度上降低求解的精度。本文考虑带阀点效应的水火联合调度问题。该问题非凸非光滑,且带有非线性约束,直接使用确定性全局优化方法求解是相当困难的。本文使用高效的半定规划求解此问题。首先用耗量特性函数的初始周期代替其余有限的周期,并对其进行二次拉格朗日插值拟合。再通过引进0-1变量,得到整个耗量特性函数的近似,进而把问题松弛为半定规划模型。最后,采用凸规划应用软件包CVX求解一个仿真算例,得到一个近似全局最优解。 相似文献
4.
5.
6.
采用玻璃微米管支撑的液/液界面通过循环伏安法(CV)研究了二环己基-18冠6(DCH18C6)加速Sr2+在水/1,2-二氯乙烷(W/DCE)界面上的转移反应,考察了DCH18C6加速Sr2+在W/DCE界面转移的影响因素,如DCH18C6和Sr2+浓度等,并求算其络合物的稳定常数。实验结果表明,Sr2+与DCH18C6发生的是一个1:1的扩散控制的界面络合转移过程,其络合常数β为5.31×1023。本研究可为理解溶剂萃取Sr2+行为提供基础理论数据。 相似文献
7.
Pincer‐Type Platinum(II) Complexes Containing N‐Heterocyclic Carbene (NHC) Ligand: Structures,Photophysical and Anion‐Binding Properties,and Anticancer Activities 下载免费PDF全文
Dr. Kai Li Dr. Taotao Zou Prof. Dr. Yong Chen Dr. Xiangguo Guan Prof. Dr. Chi‐Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7441-7453
Two classes of pincer‐type PtII complexes containing tridentate N‐donor ligands ( 1 – 8 ) or C‐deprotonated N^C^N ligands derived from 1,3‐di(2‐pyridyl)benzene ( 10 – 13 ) and auxiliary N‐heterocyclic carbene (NHC) ligand were synthesized. [Pt(trpy)(NHC)]2+ complexes 1 – 5 display green phosphorescence in CH2Cl2 (Φ: 1.1–5.3 %; τ: 0.3–1.0 μs) at room temperature. Moderate‐to‐intense emissions are observed for 1 – 7 in glassy solutions at 77 K and for 1 – 6 in the solid state. The [Pt(N^C^N)(NHC)]+ complexes 10 – 13 display strong green phosphorescence with quantum yields up to 65 % in CHCl3. The reactions of 1 with a wide variety of anions were examined in various solvents. The tridentate N‐donor ligand of 1 undergoes displacement reaction with CN? in protic solvents. Similar displacement of the N^C^N ligand by CN? has been observed for 10 , leading to a luminescence “switch‐off” response. The water‐soluble 7 containing anthracenyl‐functionalized NHC ligand acts as a light “switch‐on” sensor for the detection of CN? ion with high selectivity. The in vitro cytotoxicity of the PtII complexes towards HeLa cells has been evaluated. Complex 12 showed high cytotoxicity with IC50 value of 0.46 μM , whereas 1 – 4 and 6 – 8 are less cytotoxic. The cellular localization of the strongly luminescent complex 12 traced by using emission microscopy revealed that it mainly localizes in the cytoplasmic structures rather than in the nucleus. This complex can induce mitochondria dysfunction and subsequent cell death. 相似文献
8.
Dr. Yungen Liu Dr. Chun-Wai Tse Dr. Kar-Yee Lam Dr. Xiao-Yong Chang Dr. Xiangguo Guan Meng-Yao Chao Dr. Jie-Sheng Huang Prof. Dr. Chi-Ming Che 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(46):10828-10833
Ruthenium(II) complexes bearing a tridentate bis(N-heterocyclic carbene) ligand reacted with iminoiodanes (PhI=NR) resulting in the formation of isolable ruthenium(III)–amido intermediates, which underwent cleavage of a C−N bond of the tridentate ligand and formation of an N-substituted imine group. The RuIII–amido intermediates have been characterized by 1H NMR, UV/Vis, ESI-MS, and X-ray crystallography. DFT calculations were performed to provide insight into the reaction mechanism. 相似文献
9.
光引发的固态聚合反应一直是令人感兴趣的研究领域.本文综述了固态光聚合的研究进展.着重介绍了双炔类体系,二烯类体系以及(甲基)丙烯酸酯体系的固态光聚合的研究工作以及应用前景. 相似文献
10.
The ligand of N-(2-hydroxybenzylideneamino)-1,8-naphthalimide (HL) and its metal complexes of CuL2 (1) and CoL2 (2) have been synthesized. Elemental analysis, IR and X-ray single-crystal diffraction characterizations for 1 and 2 have been carried out. In the complexes of 1 and 2, the central metallic ions of Cu2+ and Co2+ coordinate with two deprotonated ligands of L-, respectively and adopt distorted square planar geometries. The thermal analysis result shows that the two complexes undergo two similar decomposition processes because of their similar geometric configurations. For the two complexes, fluorescence spectra measurements indicate that complex CoL2 emits stronger blue fluorescence than HL and the complex CuL2 does not emit fluorescence at all. 相似文献