全文获取类型
收费全文 | 18280篇 |
免费 | 2426篇 |
国内免费 | 2236篇 |
专业分类
化学 | 5313篇 |
晶体学 | 226篇 |
力学 | 1049篇 |
综合类 | 216篇 |
数学 | 4674篇 |
物理学 | 11464篇 |
出版年
2024年 | 29篇 |
2023年 | 142篇 |
2022年 | 341篇 |
2021年 | 379篇 |
2020年 | 387篇 |
2019年 | 460篇 |
2018年 | 449篇 |
2017年 | 642篇 |
2016年 | 670篇 |
2015年 | 616篇 |
2014年 | 1058篇 |
2013年 | 1472篇 |
2012年 | 1082篇 |
2011年 | 1126篇 |
2010年 | 983篇 |
2009年 | 1270篇 |
2008年 | 1393篇 |
2007年 | 1379篇 |
2006年 | 1214篇 |
2005年 | 1026篇 |
2004年 | 898篇 |
2003年 | 798篇 |
2002年 | 692篇 |
2001年 | 576篇 |
2000年 | 581篇 |
1999年 | 490篇 |
1998年 | 439篇 |
1997年 | 445篇 |
1996年 | 325篇 |
1995年 | 248篇 |
1994年 | 216篇 |
1993年 | 178篇 |
1992年 | 157篇 |
1991年 | 107篇 |
1990年 | 90篇 |
1989年 | 104篇 |
1988年 | 143篇 |
1987年 | 59篇 |
1986年 | 36篇 |
1985年 | 41篇 |
1984年 | 36篇 |
1983年 | 14篇 |
1982年 | 29篇 |
1981年 | 38篇 |
1980年 | 17篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1974年 | 6篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
NOROUZI Parviz GANJALI Mohammad Reza SHAHTAHERI Sayed Jamaleddin DINARVAND Rasoul HAMZEHPOOR Ali 《中国化学》2009,27(4):732-738
A continuous cyclic voltammetric study of methyldopa at gold micro electrode was carried out. The drug in phosphate buffer (pH 2.0) is adsorpted at 400 mV, giving rise to change in the current of well-defined oxidation peak of gold in the flow injection system. The proposed detection method has some of advantages, the greatest one of which are as follows: first, it is no more necessary to remove oxygen from the analyte solution and second, this is a very fast and appropriate technique for determination of the drug compound in a wide variety of chromatographic analysis methods. Signal-to-noise ratio has significantly increased by application of discrete Fast Fourier transform (FFT) method, background subtraction and two-dimensional integration of the electrode response over a selected potential range and time window. Also in this work some parameters such as sweep rate, eluent pH, and accumulation time and potential were optimized. The linear concentration range was of 1.0×10-7—1.0×10-11 mol•L-1 (r=0.9975) with a limit of detection and quantitation 0.004 nmol•L-1 and 0.03 nmol•L-1, respectively. The method has the requisite accuracy, sensitivity, precision and selectivity to assay methyldopa in tablets. The influences of pH of eluent, accumulation potential, sweep rate, and accumulation time on the determination of the methyldopa were considered. 相似文献
993.
994.
我们利用稀土直接掺杂工艺 ,通过向带隙宽为 4~ 5eV的ⅡA ⅥA族化合物中掺入稀土离子Eu、Sm ,合成了电子俘获材料 (ETM ElectronTrap pingMaterial)CaS :Eu ,Sm。该材料具有红外上转换和光存储特性 ,其红外响应光谱宽 ( 0 .8~ 1 .6μm)、量子转换效率高达 76% [1 ,2 ] 、热稳定性好、使用方便 (室温下工作 ,不需制冷 )、造价低 ,并且具有“常光充能”特性 ,即不需紫外线预激发就能在室温下将红外光 ( 0 .8~ 1 .6μm)直接转换为醒目的可见红光 ,是一种优良的红外探测材料 ,利用该材料制作的… 相似文献
995.
Jinghua Yu Bo Li Ping Dai Shenguang Ge 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2009,74(1):277-281
The interaction between 3-(4′-methylphenyl)-5-(4′-methyl-2′-sulfophenylazo) rhodanine (M4MRASP) and bovine serum albumin (BSA) was studied by using spectrofluorimetry. It was shown in fluorescence spectrums that the quenching mechanism of BSA by M4MRASP was a static quenching. Meanwhile, the binding constant and binding site numbers were calculated. The action distance (r = 8.03 nm) and energy transfer efficiency (E = 0.12) between donor (BSA) and acceptor (M4MRASP) were obtained according to the theory of Förster non-radiation energy transfer. The effect of M4MRASP on the conformation of BSA was further analyzed by using synchronous fluorescence spectrometry. A new model of the interaction between small organic molecule and biomacromolecule was established. The results offered a reference for the studies on the biological effects and action mechanism of small molecule with protein. 相似文献
996.
扩频雷达探测一阶海洋回波 总被引:1,自引:1,他引:0
利用扩频通信良好的抗干扰性和低功率谱密度下工作的特点,本文把扩频技术引入高频海洋探测雷达来探测海洋一阶回波,研究结果表明,该技术对回波质量无不良影响,同时可降低雷达发射功率,增加雷达探测距离. 相似文献
997.
O. Safronov 《Journal of Functional Analysis》2008,255(3):755-767
We consider an elliptic random operator, which is the sum of the differential part and the potential. The potential considered in the paper is the same as the one in the Andersson model, however the differential part of the operator is different from the Laplace operator. We prove that such an operator has absolutely continuous spectrum on all of (0,∞). 相似文献
998.
ZHANG Yan-Bin PING Jia-Lun LV Xiao-Fu ZONG Hong-Shi 《理论物理通讯》2008,50(7):125-128
In this paper, the gluon propagator in Landau gauge has been studied on a lattice, including the quenched and the unquenched one. The small geometry size of lattice we use is 16^3 × 32, and the big one is 20^3 × 64. For the quenched approximation, we fit the numerical results and give a little different fitting values. We also obtain unquenched effects by comparing the gluon propagator resulting from the quenched and unquenched configurations, for both the two-flavor and three-flavor cases. For the unquenched configurations, an obvious quark mass dependence has not been found in the small quark mass case, but is found in the three-flavor case when the quark mass is big. 相似文献
999.
Ryszard Struzak 《Annals of Operations Research》2001,107(1-4):339-347
This paper addresses the operation of radio links under mutual interference conditions, an important problem in spectrum management and radio link design. It introduces the capacity loss and isolation index as measures of effective use of radio links and radio frequency spectrum resources. 相似文献
1000.
马米佳 《新疆大学学报(理工版)》2000,17(1):16-19
利用一类紧abelian群G上的函数空间L2(G)上以及D(R)上平移不变线性泛函的自动连续性并结合闭图象定理证明这些空间上的平移不变线性算子连续。 相似文献