全文获取类型
收费全文 | 7351篇 |
免费 | 625篇 |
国内免费 | 2350篇 |
专业分类
化学 | 6333篇 |
晶体学 | 45篇 |
力学 | 1050篇 |
综合类 | 126篇 |
数学 | 1578篇 |
物理学 | 1194篇 |
出版年
2024年 | 17篇 |
2023年 | 84篇 |
2022年 | 133篇 |
2021年 | 222篇 |
2020年 | 303篇 |
2019年 | 274篇 |
2018年 | 239篇 |
2017年 | 274篇 |
2016年 | 371篇 |
2015年 | 281篇 |
2014年 | 360篇 |
2013年 | 674篇 |
2012年 | 471篇 |
2011年 | 465篇 |
2010年 | 409篇 |
2009年 | 442篇 |
2008年 | 430篇 |
2007年 | 527篇 |
2006年 | 463篇 |
2005年 | 506篇 |
2004年 | 531篇 |
2003年 | 428篇 |
2002年 | 381篇 |
2001年 | 321篇 |
2000年 | 285篇 |
1999年 | 239篇 |
1998年 | 192篇 |
1997年 | 150篇 |
1996年 | 128篇 |
1995年 | 144篇 |
1994年 | 125篇 |
1993年 | 99篇 |
1992年 | 73篇 |
1991年 | 53篇 |
1990年 | 47篇 |
1989年 | 31篇 |
1988年 | 25篇 |
1987年 | 27篇 |
1986年 | 12篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 6篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Bifurcation analysis of visual angle model with anticipated time and stabilizing driving behavior 下载免费PDF全文
Xueyi Guan 《中国物理 B》2022,31(7):70507-070507
In the light of the visual angle model (VAM), an improved car-following model considering driver's visual angle, anticipated time and stabilizing driving behavior is proposed so as to investigate how the driver's behavior factors affect the stability of the traffic flow. Based on the model, linear stability analysis is performed together with bifurcation analysis, whose corresponding stability condition is highly fit to the results of the linear analysis. Furthermore, the time-dependent Ginzburg-Landau (TDGL) equation and the modified Korteweg-de Vries (mKdV) equation are derived by nonlinear analysis, and we obtain the relationship of the two equations through the comparison. Finally, parameter calibration and numerical simulation are conducted to verify the validity of the theoretical analysis, whose results are highly consistent with the theoretical analysis. 相似文献
3.
Kai Cheng Xiao-Shuai Zhang Jie An Cheng Li Ruo-Yun Zhang Run Ye Prof. Dr. Bang-Jiao Ye Prof. Dr. Bo Liu Prof. Dr. Yuan-Di Zhao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(31):7553-7560
Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag2S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag2S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag2S had more opportunities to react with surrounding O2, which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag2S and PDA-Ag2S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag2S showed distinctly better therapeutic effects than Ag2S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag2S quantum dots, which extended and enhanced the regulatory effect originating from PDA. 相似文献
4.
Giorgia Scetta Jianzhu Ju Nathan Selles Patrick Heuillet Matteo Ciccotti Costantino Creton 《Journal of polymer science. Part A, Polymer chemistry》2021,59(8):685-696
We investigate the cyclic mechanical behavior in uniaxial tension of three different commercial thermoplastic polyurethane elastomers (TPU) often considered as a sustainable replacement for common filled elastomers. All TPU have similar hard segment contents and linear moduli but sensibly different large strain properties as shown by X-ray analysis. Despite these differences, we found a stiffening effect after conditioning in step cyclic loading which greatly differs from the common softening (also referred as Mullins effect) observed in chemically crosslinked filled rubbers. We propose that this self-reinforcement is related to the fragmentation of hard domains, naturally present in TPU, in smaller but more numerous sub-units that may act as new physical crosslinking points. The proposed stiffening mechanism is not dissimilar to the strain-induced crystallization observed in stretched natural rubber, but it presents a persistent nature. In particular, it may cause a local reinforcement where an inhomogeneous strain field is present, as is the case of a crack propagating in cyclic fatigue, providing a potential explanation for the well-known toughness and wear resistance of TPU. 相似文献
5.
Star copolymers have attracted significant interest due to their different characteristics compared with diblock copolymers, including higher critical micelle concentration, lower viscosity, unique spatial shape, or morphologies. Development of synthetic skills such as anionic polymerization and controlled radical polymerization have made it possible to make diverse architectures of polymers. Depending on the molecular architecture of the copolymer, numerous morphologies are possible, for instance, Archimedean tiling patterns and cylindrical microdomains at symmetric volume fraction for miktoarm star copolymers as well as asymmetric lamellar microdomains for star‐shaped copolymers, which have not been reported for linear block copolymers. In this review, we focus on morphologies and microphase separations of miktoarm (AmBn and ABC miktoarm) star copolymers and star‐shaped [(A‐b‐B)n] copolymers with nonlinear architecture. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1–21 相似文献
6.
7.
8.
This paper deals with the Cauchy–Dirichlet problem for the fractional Cahn–Hilliard equation. The main results consist of global (in time) existence of weak solutions, characterization of parabolic smoothing effects (implying under proper condition eventual boundedness of trajectories), and convergence of each solution to a (single) equilibrium. In particular, to prove the convergence result, a variant of the so-called ?ojasiewicz–Simon inequality is provided for the fractional Dirichlet Laplacian and (possibly) non-analytic (but ) nonlinearities. 相似文献
9.
10.
New thiazole derivatives were synthesized and fully characterized, then coordinated with PtCl4 salt. Also, the newly synthesized Pt(IV) complexes were investigated analytically (elemental and thermogravimetric analyses), spectrally (infrared, UV–visible, mass, 1H NMR, 13C NMR, X‐ray diffraction) as well as theoretically (kinetics, modeling and docking). The data extracted led to the establishment of the best chemical and structural forms. Octahedral geometry was the only formula proposed for all complexes, which is favorable for d6 systems. The molecular ion peaks from mass spectral analysis coincide with all analytical data, confirming the molecular formula proposed. X‐ray diffraction (XRD) and scanning electron microscopy (SEM) allowed discrimination of features between crystalline particles and other amorphous morphology. By applying Gaussian09 as well as HyperChem 8.2 programs, the best structural forms were obtained, as well as computed significant parameters. Computed parameters such as softness, hardness, surface area and reactivity led us towards application in two opposing pathways: tumor inhibition and oxidation activation. The catalytic oxidation for CO was conducted over PtO2, which was yielded from calcination of the most reactive complex. The success of catalytic role for synthesized PtO2 was due to its particulate size and surface morphology, which were estimated from XRD patterns and SEM images, respectively. The antitumor activity was tested versus HCT‐116 and HepG‐2 cell lines. Mild toxicity was recorded for two of the derivatives and their corresponding complexes. This degree of toxicity is more favorable in most cases, due to exclusion of serious side effects, which is coherently attached with known antitumor drugs. 相似文献