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941.
942.
Photocatalytic reduction of CO2 to produce fuels is a promising way to reduce CO2 emission and address the energy crisis. However, the H2 evolution reaction competes with CO2 photoreduction, which would lower the overall selectivity for carbonaceous products. Cu2O has emerged as a promising material for suppressing the H2 evolution. However, it suffers from poor stability, which is commonly regarded as the result of the electron‐induced reduction of Cu2O. This paper describes a simple strategy using Cu2O as a dark cathode and TiO2 as a photoanode to achieve stable aqueous CO2 reduction with a high Faradaic efficiency of 87.4 % and a selectivity of 92.6 % for carbonaceous products. We have shown that the photogenerated holes, instead of the electrons, primarily account for the instability of Cu2O. Therefore, Cu2O was used as a dark cathode to minimize the adverse effects of holes, by which an improved stability was achieved compared to the Cu2O photocathode under illumination. Additionally, direct exposure of the Cu2O surface to the electrolyte was identified as a critical factor for the high selectivity for carbonaceous products.  相似文献   
943.
Two‐dimensional (2D) layered semiconducting transition‐metal dichalcogenides (TMDCs) are promising candidates for next‐generation ultrathin, flexible, and transparent electronics. Chemical vapor deposition (CVD) is a promising method for their controllable, scalable synthesis but the growth mechanism is poorly understood. Herein, we present systematic studies to understand the CVD growth mechanism of monolayer MoSe2, showing reaction pathways for growth from solid and vapor precursors. Examination of metastable nanoparticles deposited on the substrate during growth shows intermediate growth stages and conversion of non‐stoichiometric nanoparticles into stoichiometric 2D MoSe2 monolayers. The growth steps involve the evaporation and reduction of MoO3 solid precursors to sub‐oxides and stepwise reactions with Se vapor to finally form MoSe2. The experimental results and proposed model were corroborated by ab initio Car–Parrinello molecular dynamics studies.  相似文献   
944.
Fluorescence imaging of tyrosinase (a cancer biomarker) in living organisms is of great importance for biological studies. However, selective detection of tyrosinase remains a great challenge because current fluorescent probes that contain the 4‐hydroxyphenyl moiety show similar fluorescence responses to both tyrosinase and some reactive oxygen species (ROS), thereby suffering from ROS interference. Herein, a new tyrosinase‐recognition 3‐hydroxybenzyloxy moiety, which exhibits distinct fluorescence responses for tyrosinase and ROS, is proposed. Using the recognition moiety, we develop a near‐infrared fluorescence probe for tyrosinase activity, which effectively eliminates the interference from ROS. The high specificity of the probe was demonstrated by imaging and detecting endogenous tyrosinase activity in live cells and zebrafish and further validated by an enzyme‐linked immunosorbent assay. The probe is expected to be useful for the accurate detection of tyrosinase in complex biosystems.  相似文献   
945.
We show the successful use of a heralded noiseless linear amplifier on the detection stage in the two-way continuous-variable quantum key distribution to improve the performance. Due to the excess noise, the secret-key rate of the two-way protocol becomes negative for a certain distance of transmission. The use of a heralded noiseless linear amplifier increases this distance by the equivalent of 20 log10g dB of losses, and it also helps the two-way protocol tolerate more excess noise.  相似文献   
946.
Let f(n)be a multiplicative function satisfying |f(n)|≤1,q(≤N~2)be a positive integer and a be an integer with(a,q)= 1.In this paper,we shall prove that ∑n≤N(n,q)=1f(n)e(an/q)■(1/2)(τ(q)/q)N loglog(6N)+ q~(1/4+ε/2)N~(2/1)(log(6N))~(1/2)+N/(1/2)(loglog(6N)),where n is the multiplicative inverse of n such that nn ≡ 1(mod q),e(x)= exp(2πix),and τ(·)is the divisor function.  相似文献   
947.
Let QN be an N-anisotropic Laplacian operator, which contains the ordinary Laplacian operator, N-Laplacian operator and the anisotropic Laplacian operator. We firstly obtain the properties of QN, which contain the weak maximal principle, the comparison principle and the mean value property. Then a priori estimates and blow-up analysis for solutions of QNu in bounded domain in ?N, N ≥ 2 are established. Finally, the blow-up behavior of the only singular point is also considered.  相似文献   
948.
Permanent electric dipole moments (EDMs) arise due to the breaking of time-reversal or, equivalently, CP-symmetry. Although EDM searches have so far only set upper limits, which are many orders of magnitude larger than Standard Model (SM) predictions, the motivation for more sensitive searches is stronger than ever. A new effort at FRM-II incorporating 129Xe and 3He as a co-magnetometer can potentially improve the current limit. The noble gas mixture of 129Xe and 3He is simultanously polarized by spin-exchange optical pumping and then transferred into a high-performance magnetically shielded room. Inside, both species can freely precess in the presence of applied magnetic and electric fields. The precession signals are detected by LTc SQUID sensors. In EDM cells with silicon electrodes we observed spin lifetimes in excess of 2500 s without and with high-voltage applied. This meets one requirement to achieve our goal of improving the EDM limit on 129Xe by several orders of magnitude.  相似文献   
949.
A series of hierarchically structured porous silica sphere (HSPSS) materials are successfully fabricated by a facile, one‐step microemulsion/vesicle bimodal method in a multicomponent microemulsion system of P123/n‐butanol/1,3,5‐trimethylbenzene/KCl/H2O (surfactant/cosurfactant/oil/salt/water). The pore structures of the obtained HSPSS products consist of mesocellular foam and mesostructured vesicles. In contrast to the traditional porous silica materials the new structures combine two separate, distinct mesophases with different‐sized mesovoids in a single porous sphere. Moreover, the proportion of every mesophase in obtained HSPSS can be easily adjusted by tuning the initially added amount of n‐butanol or KCl in this multicomponent microemulsion system. When the molar ratio of KCl/tetraethoxysilane is 2.15, the obtained HSPSS material is turned into uniform mesostructured vesicle silica spheres, which consist of many small diameter vesicle particles. The hydrodesulfurization (HDS) activity of fluid catalytic cracking diesel over the HSPSS was tested. HSPSS‐0.75‐1.43 catalyst support with multiple mesoporous structures shows the highest HDS efficiency (98.5%) among all the studied catalysts.  相似文献   
950.
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