全文获取类型
收费全文 | 31914篇 |
免费 | 4717篇 |
国内免费 | 3154篇 |
专业分类
化学 | 17905篇 |
晶体学 | 310篇 |
力学 | 1531篇 |
综合类 | 110篇 |
数学 | 2914篇 |
物理学 | 9333篇 |
无线电 | 7682篇 |
出版年
2024年 | 113篇 |
2023年 | 790篇 |
2022年 | 1027篇 |
2021年 | 1251篇 |
2020年 | 1234篇 |
2019年 | 1175篇 |
2018年 | 1008篇 |
2017年 | 931篇 |
2016年 | 1386篇 |
2015年 | 1400篇 |
2014年 | 1646篇 |
2013年 | 2180篇 |
2012年 | 2786篇 |
2011年 | 2777篇 |
2010年 | 1942篇 |
2009年 | 1873篇 |
2008年 | 2056篇 |
2007年 | 1853篇 |
2006年 | 1667篇 |
2005年 | 1524篇 |
2004年 | 1030篇 |
2003年 | 837篇 |
2002年 | 798篇 |
2001年 | 579篇 |
2000年 | 615篇 |
1999年 | 731篇 |
1998年 | 607篇 |
1997年 | 565篇 |
1996年 | 607篇 |
1995年 | 490篇 |
1994年 | 399篇 |
1993年 | 321篇 |
1992年 | 301篇 |
1991年 | 250篇 |
1990年 | 205篇 |
1989年 | 160篇 |
1988年 | 116篇 |
1987年 | 122篇 |
1986年 | 103篇 |
1985年 | 93篇 |
1984年 | 56篇 |
1983年 | 47篇 |
1982年 | 38篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1976年 | 9篇 |
1975年 | 11篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
951.
Qiaoli Yue Lijun Sun Tongfei Shen Xiaohong Gu Shuqiu Zhang Jifeng Liu 《Journal of fluorescence》2013,23(6):1313-1318
In the present work, gold nanocluster (GNC) induced by bovine serum albumin (BSA) was synthesized as a novel fluorescence probe to detect nitrite (NO2 ?) sensitively and selectively. The fluorescence of GNC was found to be quenched effectively by NO2 ?. Under the optimum conditions, it was found that the change of fluorescence intensity was proportional with the concentration of NO2 ? in the linear range of 0.1–50 μM (R?=?0.9990), with a detection limit (S/N?=?3) of 30 nM. The absorption spectroscopy, circular dichroism (CD), and X-ray photoelectron spectroscopy (XPS) studies were employed to discuss the quenching mechanism. In addition, the present approach was successfully applied in real water samples. 相似文献
952.
Xiao‐Jie Liu Zhen‐Yu Li Zhong‐Feng Li Xiao‐Xia Gao Yu‐Zhi Zhou Hai‐Feng Sun Li‐Zeng Zhang Xiao‐Qing Guo Guan‐Hua Du Xue‐Mei Qin 《Magnetic resonance in chemistry : MRC》2012,50(3):187-192
Chronic unpredictable mild stress (CUMS) is a well‐validated model of depression. In this study, a urinary metabonomics method based on the NMR spectrometry was used to study the metabolic perturbation in CUMS‐induced rat depression model. With pattern recognition analysis, a clear separation of CUMS rats and healthy controls was achieved, and nine endogenous metabolites contributing to the separation were identified. CUMS‐treated rats were characterized by the increase of glycine, pyruvate, glutamine, and asparagines, as well as the decrease of 2‐oxoglutarate, dimethylglycine, citrate, succinate, and acetate. The urinary biochemical changes related to the metabolic disturbance in CUMS induced depression, and the possible correlations with live qi stagnation in traditional Chinese medicine are discussed. The work shows that CUMS is a reliable model for studying depression, and the noninvasive urinary metabolomic method is a valuable tool to investigate the biochemical pertubations in depression as an early diagnostic means. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
953.
S Sun J Kroll Y Luo L Zhang 《Synlett : accounts and rapid communications in synthetic organic chemistry》2012,2012(1):54-56
A gold-catalyzed regioselective homodimerization of aliphatic terminal alkynes is described. Bulky and less Lewis acidic tBuXPhosAuNTf(2) is the preferred catalyst, and the additive, anhydrous NaOAc, substantially facilitates the reaction. 相似文献
954.
955.
Mingyu Sun 《国际流体数值方法杂志》2013,73(2):130-151
A general and robust subgrid closure model for two‐material cells is proposed. The conservative quantities of the entire cell are apportioned between two materials, and then, pressure and velocity are fully or partially equilibrated by modeling subgrid wave interactions. An unconditionally stable and entropy‐satisfying solution of the processes has been successfully found. The solution is valid for arbitrary level of relaxation. The model is numerically designed with care for general materials and is computationally efficient without recourse to subgrid iterations or subcycling in time. The model is implemented and tested in the Lagrange‐remap framework. Two interesting results are observed in 1D tests. First, on the basis of the closure model without any pressure and velocity relaxation, a material interface can be resolved without creating numerical oscillations and/or large nonphysical jumps in the problem of the modified Sod shock tube. Second, the overheating problem seen near the wall surface can be solved by the present entropy‐satisfying closure model. The generality, robustness, and efficiency of the model make it useful in principle in algorithms, such as ALE methods, volume of fluid methods, and even some mixture models, for compressible two‐phase flow computations. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
956.
The title complex [Ni4(SPri)8] was confirmed by single crystal X-ray crystal diffraction analysis. The crystals are monoclinic, space group P2/n with a = 12.760(3), b = 10.059(2), c = 14.484(3) Å, α = 90, β = 93.70(3), γ = 90°, V = 1855.3(6) Å3, Z = 4, F(000) = 880, Dc = 1.496 g/cm3, μ = 2.463 mm?1, the final R = 0.0352 and wR = 0.0580. A total of 18,588 reflections were collected, of which 4404 were independent (Rint = 0.0631). In the crystal packing diagram, intermolecular C—H···Ni hydrogen bonds stabilize the solid state of the title complex. 相似文献
957.
A class of nonlinear difference equations is considered. We show how their polynomial solutions can be computed in a systematic manner. 相似文献
958.
A one‐pot method for synthesis of reduced graphene oxide‐supported Cu–Cu2O and catalytic application in tandem reaction of halides and sodium azide with terminal alkynes
下载免费PDF全文
![点击此处可从《应用有机金属化学》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhuofei Li Hongyan Zhao Huatao Han Jinyi Song Yang Liu Weihao Guo Zhizhong Sun Wenyi Chu 《应用有机金属化学》2018,32(4)
Reduced graphene oxide (RGO)‐supported Cu–Cu2O nanocomposite material (Cu‐Cu2O@RGO) was prepared through a one‐pot reflux synthesis method. The morphology, crystal structure and composition of the prepared Cu‐Cu2O@RGO were characterized using transmission electron microscopy, X‐ray diffraction, and X‐ray photoelectron, infrared and Raman spectroscopies. Cu‐Cu2O@RGO as a heterogeneous catalyst was applied to tandem reactions of halides and sodium azide with terminal alkynes to synthesize effectively 1,4‐disubstituted 1,2,3‐triazoles. Moreover, the catalyst showed excellent recyclability performance with very little leaching of the metal. Compared with homogeneous catalysts, Cu‐Cu2O@RGO as a green and efficient catalyst was recoverable, easy to separate and highly stable in the tandem method for the synthesis of 1,2,3‐triazole compounds. 相似文献
959.
960.