全文获取类型
收费全文 | 21088篇 |
免费 | 642篇 |
国内免费 | 589篇 |
专业分类
化学 | 2180篇 |
晶体学 | 14篇 |
力学 | 140篇 |
综合类 | 174篇 |
数学 | 766篇 |
物理学 | 694篇 |
综合类 | 18351篇 |
出版年
2024年 | 28篇 |
2023年 | 105篇 |
2022年 | 268篇 |
2021年 | 280篇 |
2020年 | 257篇 |
2019年 | 242篇 |
2018年 | 215篇 |
2017年 | 287篇 |
2016年 | 328篇 |
2015年 | 449篇 |
2014年 | 1022篇 |
2013年 | 763篇 |
2012年 | 1161篇 |
2011年 | 1406篇 |
2010年 | 1246篇 |
2009年 | 1341篇 |
2008年 | 1550篇 |
2007年 | 1947篇 |
2006年 | 1652篇 |
2005年 | 1437篇 |
2004年 | 1171篇 |
2003年 | 1071篇 |
2002年 | 801篇 |
2001年 | 691篇 |
2000年 | 605篇 |
1999年 | 405篇 |
1998年 | 291篇 |
1997年 | 263篇 |
1996年 | 180篇 |
1995年 | 159篇 |
1994年 | 150篇 |
1993年 | 115篇 |
1992年 | 83篇 |
1991年 | 78篇 |
1990年 | 61篇 |
1989年 | 67篇 |
1988年 | 50篇 |
1987年 | 24篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
231.
232.
SUN Ying LIU Shi-chun LIU Xia SONG Da-qian BI Shu-yun ZHANG Han-qi 《高等学校化学研究》2006,22(3):324-327
Introduction Humanserumalbumin(HSA)isawell known transportproteinforavarietyofmoleculesandions[1].Thebindingofadrugtoserumalbuminhasimportant pharmacokineticconsequencesbecauseitinfluences distribution,excretionandpharmacologicaleffectsof thedruginthebody… 相似文献
233.
超临界流体萃取仪器的研制 总被引:1,自引:1,他引:1
本文报道了以国产原配件为基础,成功地研制了分析规模的超临界流体萃取仪器、并对仪器性能进行了全面考察,仪器性能稳定,重现性良好(RSD<3.1%),定量线性关系可靠,可满足定量萃取的要求。 相似文献
234.
应用活化鲁米诺,用优化的增强化学发光酶联免疫分析体系测定人绒毛膜促性腺激素,检测限为0.2mIU/ml。线性范围0~200mIU/ml,与放射免分析测定结果比较,相关性良好。进而又发展了一种半定量的照相测定法,通过实际血清样品测定,效果良好。 相似文献
235.
Procion red HE-3B (RR120) is an example of dye currently used in affinity purification. A method is described for determining trace amounts of RR120 dye contaminant in human serum albumin by cathodic stripping voltammetry. The method is based on a measure of a well-defined peak at −0.58 V, obtained when samples of HSA protein (0.01-2% w/v) containing dye concentrations are submitted to a heating time of 330 min at 80 °C in NaOH, pH 12.0 and the samples are removed to a solution containing Britton-Robinson buffer, pH 4.0. Using an optimum accumulation potential and time of 0 V and 240 s, respectively, linear calibration curves were obtained from 1.0×10−9 to 1.0×10−8 mol l−1 for RR120 dye. Leakage/hydrolysis of reactive red 120 from an agarose support (e.g. at pH 2 or 12) can also be conveniently determined at very low levels (sub-μg ml−1) by means of cathodic stripping voltammetry, which involves adsorptive accumulation of the dye onto the hanging mercury-drop electrode. 相似文献
236.
Parameterization of OPLS-AA force field for the conformational analysis of macrocyclic polyketides 总被引:1,自引:0,他引:1
The parameters for the OPLS-AA potential energy function have been extended to include some functional groups that are present in macrocyclic polyketides. Existing OPLS-AA torsional parameters for alkanes, alcohols, ethers, hemiacetals, esters, and ketoamides were improved based on MP2/aug-cc-pVTZ and MP2/aug-cc-pVDZ calculations. Nonbonded parameters for the sp(3) carbon and oxygen atoms were refined using Monte Carlo simulations of bulk liquids. The resulting force field predicts conformer energies and torsional barriers of alkanes, alcohols, ethers, and hemiacetals with an overall RMS deviation of 0.40 kcal/mol as compared to reference data. Densities of 19 bulk liquids are predicted with an average error of 1.1%, and heats of vaporization are reproduced within 2.4% of experimental values. The force field was used to perform conformational analysis of smaller analogs of the macrocyclic polyketide drug FK506. Structures that adopted low-energy conformations similar to that of bound FK506 were identified. The results show that a linker of four ketide units constitutes the shortest effector domain that allows binding of the ketide drugs to FKBP proteins. It is proposed that the exact chemical makeup of the effector domain has little influence on the conformational preference of tetraketides. 相似文献
237.
Patricia C DamianiMariano D Borraccetti Alejandro C Olivieri 《Analytica chimica acta》2002,471(1):87-96
A direct method for the simultaneous determination of naproxen and salicylate in human serum is reported, based on a combination of spectrofluorometric measurements with two multivariate calibration techniques: partial least-squares (PLS-1) and the novel net analyte preprocessing (NAP). The method is rapid, selective and sensitive, and is based on the measurement of the fluorescence spectra of NH3 alkalinized whole human sera at the excitation wavelength of 315 nm. It can be applied within the ranges of concentrations 50-200 ng ml−1 for naproxen and 100-300 ng ml−1 for salicylate. The employed chemometric techniques have been compared on the basis of the statistical indicators for calibration and validation. Reproducibility and interference studies in abnormal sera have also been carried out. 相似文献
238.
A method for the determination of the major serotonin metabolite — 5-hydroxyindole-3-acetic acid (5-HIAA) in human gastric juice by cyclic voltammetry was described. The measurement conditions were investigated. The potential window was chosen from +0.1 to +0.9 V, the supporting electrolyte was 0.025 M PBS solution (pH 2.0). The method allowed determination in the concentration range from 2.0 ×10−7 to 2.0 ×10 −5 M and a detection limit of 80 nM. When samples of gastric juice were analyzed with the method, we obtained the mean content of 5-HIAA in the gastric juice. Meanwhile, interference from other ions and substances were examined. The experimental results indicate that the method for the determination of gastric juice samples is successful. 相似文献
239.
Piotr Kowalski Marcin Marszałł Ilona Olędzka Wojciech Czarnowski 《Chromatographia》2007,66(5-6):357-361
Two rapid and popular methods—capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC) have been compared
for analysis of cotinine in human urine. Cotinine was analyzed in less than 7 min, with detection limits of 5 and 3.2 ng mL−1 for CE and HPLC, respectively. The performance of the methods was evaluated in terms of sensitivity, specificity, precision,
accuracy, and limits of detection and quantification. Calibration plots were linear in the range 50–4,000 ng mL−1, at least, and mean recoveries were satisfactory for both techniques. The methods were successfully used for quantification
of cotinine in urine. 相似文献
240.
四川地区宫颈癌组织HPV18和HPV45 E6基因突变分析 总被引:1,自引:0,他引:1
采用聚合酶链反应技术对四川地区2003~2004年收集的60例宫颈癌患者的癌组织DNA进行人乳头瘤病毒(HPV) E6基因扩增, 获得HPV18和45型E6基因. 序列分析发现, 18型三例E6基因有同样的两处同义突变; 45型两例E6基因发生突变, 一例有两处碱基突变, 另一例发生六处碱基突变, 其中两处涉及氨基酸变化, 均位于E6抗原决定簇区. HPV45型E6基因中134位c→t, 157位c→t, 259位g→t和341位t→c的碱基点突变未见报道. 另外, 该地区HPV18和45型突变株之间存在碱基互变, 它们之间的最小差异比野生型HPV18和HPV45之间的差异小4.05%, 该数值比在非洲发现的突变株的要小很多, 该结果支持HPV18和HPV45可能起源于非洲的观点. 相似文献