全文获取类型
收费全文 | 8469篇 |
免费 | 1235篇 |
国内免费 | 1757篇 |
专业分类
化学 | 6605篇 |
晶体学 | 493篇 |
力学 | 85篇 |
综合类 | 52篇 |
数学 | 195篇 |
物理学 | 2051篇 |
无线电 | 1980篇 |
出版年
2024年 | 40篇 |
2023年 | 218篇 |
2022年 | 202篇 |
2021年 | 250篇 |
2020年 | 365篇 |
2019年 | 338篇 |
2018年 | 257篇 |
2017年 | 420篇 |
2016年 | 454篇 |
2015年 | 402篇 |
2014年 | 457篇 |
2013年 | 657篇 |
2012年 | 604篇 |
2011年 | 652篇 |
2010年 | 463篇 |
2009年 | 568篇 |
2008年 | 527篇 |
2007年 | 575篇 |
2006年 | 524篇 |
2005年 | 430篇 |
2004年 | 422篇 |
2003年 | 403篇 |
2002年 | 422篇 |
2001年 | 303篇 |
2000年 | 218篇 |
1999年 | 218篇 |
1998年 | 164篇 |
1997年 | 121篇 |
1996年 | 112篇 |
1995年 | 91篇 |
1994年 | 75篇 |
1993年 | 73篇 |
1992年 | 70篇 |
1991年 | 45篇 |
1990年 | 44篇 |
1989年 | 24篇 |
1988年 | 17篇 |
1986年 | 20篇 |
1985年 | 20篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 17篇 |
1978年 | 14篇 |
1976年 | 11篇 |
1975年 | 13篇 |
1974年 | 14篇 |
1971年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
《中国化学会会志》2018,65(5):523-530
Polyethylene glycol‐(N‐methylimidazolium) hydroxide‐grafted hydroxyapatite encapsulated γ‐Fe2O3 nanoparticles, γ‐Fe2O3@HAp@PEG(mim)OH, were prepared and characterized by FTIR, SEM, TEM, TGA, and EDAX. This nanocomposite was applied as a novel, green, nanomagnetic, and recyclable basic phase‐transfer catalyst for the synthesis of tetrahydrobenzopyrans in high yields via the three‐component reaction of aromatic aldehydes, malononitrile, and dimedone or 1,3‐cyclohexanedione in aqueous media at ambient temperature. 相似文献
92.
《Biomedical chromatography : BMC》2018,32(9)
A rapid and sensitive LC–MS/MS method for therapeutic drug monitoring oral vinorelbine (VRL) metronomic anticancer chemotherapy has been developed and validated. Analysis of VRL and its main active metabolite 4‐O‐deacetylvinorelbine (M1) was performed in whole blood matrix. Both analytes were extracted by protein precipitation and separated on an Onyx monolith C18, 50 × 2 mm column then quantified by positive electrospray ionization and multiple reaction monitoring mode. The LLOQ was 0.05 ng/mL for both VRL and M1. Linearity was up to 25ng/mL with R2 ≥ 0.994. The intra‐ and inter‐assay precisions were ≤ 11.6 and ≤ 10.4% while the ranges of accuracy were [−8.7%; 10.3%] and [−10.0; 7.4%] for VRL and M1, respectively. The clinical suitability of the method has been proved by the determination of the CTrough blood concentrations of VRL and M1 in 64 nonsmall cell lung cancer elderly patients. The analytical performance of the assay was suitable for pharmacokinetic monitoring of VRL and M1, allowing the personalization of the VRL metronomic treatments. 相似文献
93.
Olga Serifi Fotios Tsopelas Anna‐Maria Kypreou Maria Ochsenkühn‐Petropoulou Panagiotis Kefalas Anastasia Detsi 《Journal of Physical Organic Chemistry》2013,26(3):226-231
The electrochemical behaviour of 13 chalcone analogues was systematically studied by means of cyclic voltammetry and chronoamperometry at a glassy carbon (GC), gold and platinum working electrodes using two different supporting electrolyte/solvent combinations. It was found that chalcone analogues can be easily oxidized at both GC and gold working electrodes, but not at a platinum electrode. Principal component analysis was further employed to reveal similarities/dissimilarities between oxidation potentials, chronoamperometric signals and ability of the compounds to scavenge the reactive oxygen species H2O2. The study reveals the inverse proportional relationship between the scavenging ability of H2O2, expressed as IC50, and chronoamperometric signal at 800 mV using gold as working electrode. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
94.
以介孔二氧化硅MCM-41为硅源,采用低温水热反应与后续煅烧相结合的方法合成Sr2-xZnSi2O7∶xEu3+红色荧光粉。实验结果表明,150℃水热处理16 h后的反应产物含Sr2ZnSi2O7相,经后续950℃煅烧3h得到Sr2ZnSi2O7纯相。在392 nm近紫外光的有效激发下,Sr2-xZnSi2O7∶xEu3+荧光粉显示Eu3+离子的特征跃迁发射,以615 nm的5D0→7F2跃迁发射峰为最强。适量Eu3+的掺杂对Sr2ZnSi2O7相结构几乎没有影响,当Eu3+离子的掺杂量x=0.10时,荧光粉发光强度最大。 相似文献
95.
96.
H.M. Martínez J. Torres M.E. Rodríguez-García L.D. López Carreño 《Physica B: Condensed Matter》2012,407(16):3199-3202
Thin films of molybdenum trioxide (MoO3) were deposited on common glass using the chemical spray pyrolysis technique. A (NH4)6Mo7O244H20 solution 0.1 M was used as the precursor one. The influence of substrate temperature on the crystallographic structure, surface morphology and electrical behavior of MoO3 thin films was studied. MoO3 can exist in two crystalline forms, the thermodynamically stable orthorhombic α-MoO3 and the metastable monoclinic β-MoO3 phase. XRD-spectra showed a growth of α-MoO3 phase percentage as substrate temperature increases from 420 K up to 670 K. Films deposited in the 500–600 K range have a clearly porous surface structure of nanometer order as can be seen in SEM images. Changes up to six magnitude orders were observed in MoO3 thin films electrical resistance when films temperature varied from 100 K up to 500 K. The sensing property of these MoO3 films was also studied. The sensitivity was investigated in the temperature range 160 and 360 K for H2O and CO gases, respectively. Both of them are of reducing nature. In all studied cases sensitivity decreases slowly as film temperature is raised. At room temperature the sensitivity changes from 12 up to 75% depending on substrate temperature. The sensitivity for CO gas was found to be lower than that of H2O. 相似文献
97.
Monte Carlo study of the universal area distribution of clusters in the honeycomb O(n) loop model 下载免费PDF全文
We investigate the area distribution of clusters (loops) in the honeycomb O(n) loop model by means of the worm algorithm with n = 0.5, 1, 1.5, and 2. At the critical point, the number of clusters, whose enclosed area is greater than A, is proportional to A-1 with a proportionality constant C. We confirm numerically that C is universal, and its value agrees well with the predictions based on the Coulomb gas method. 相似文献
98.
利用发射光谱技术在大气压下测量了空气中多针对板负直流电晕放电和正电晕流光放电产生的O(3p5 P→3s 5 S02777.4nm)活性原子发射光谱。在负电晕放电中,研究了放电功率、电极间距、N2含量和相对湿度等因素对O活性原子产生过程的影响;在正电晕流光放电阶段,研究了O活性原子相对密度在放电反应空间的分布特点。结果表明:O活性原子产量随放电功率的增加而增大,随电极间距增大而减少,随相对湿度和氮气含量的增加,其产量先增大后减少;O活性原子相对密度沿针尖轴向呈先增大后减小的趋势。 相似文献
99.
100.
Single GPU scaling is unable to keep pace with the soaring demand for high throughput computing. As such executing an application on multiple GPUs connected through an off-chip interconnect will become an attractive option to explore. However, much of the current code is written for a single GPU system. Porting such a code for execution on multiple GPUs is difficulty task. In particular, it requires programmer effort to determine how data is partitioned across multiple GPU cards and then launch the appropriate thread blocks that mostly accesses the data that is local to that card. Otherwise, cross-card data movement is an expensive operation. In this work we explore hardware support to efficiently parallelize a single GPU code for execution on multiple GPUs. In particular, our approach focuses on minimizing the number of remote memory accesses across the off-chip network without burdening the programmer to perform data partitioning and workload assignment. We propose a data-location aware thread block scheduler to schedule the thread blocks on the GPU that has most of its input data. The scheduler exploits well known observation that GPU workloads tend to launch a kernel multiple times iteratively to process large volumes of data. The memory accesses of the thread block across different iterations of a kernel launch exhibit correlated behavior. Our data location aware scheduler exploits this predictability to track memory access affinity of each thread block to a specific GPU card and stores this information to make scheduling decisions for future iterations. To further reduce the number of remote accesses we propose a hybrid mechanism that enables migrating or copying the pages between the memory of multiple GPUs based on their access behavior. Hence, most of the memory accesses are to the local GPU memory. Over an architecture consisting of two GPUs, our proposed schemes are able to improve the performance by 1.55× when compared to single GPU execution across widely used Rodinia [17], Parboil [18], and Graph [23] benchmarks. 相似文献