全文获取类型
收费全文 | 14841篇 |
免费 | 1734篇 |
国内免费 | 664篇 |
专业分类
化学 | 4119篇 |
晶体学 | 30篇 |
力学 | 815篇 |
综合类 | 188篇 |
数学 | 1942篇 |
物理学 | 2452篇 |
无线电 | 7693篇 |
出版年
2024年 | 35篇 |
2023年 | 194篇 |
2022年 | 433篇 |
2021年 | 513篇 |
2020年 | 587篇 |
2019年 | 372篇 |
2018年 | 330篇 |
2017年 | 551篇 |
2016年 | 683篇 |
2015年 | 674篇 |
2014年 | 1106篇 |
2013年 | 894篇 |
2012年 | 1044篇 |
2011年 | 986篇 |
2010年 | 752篇 |
2009年 | 806篇 |
2008年 | 810篇 |
2007年 | 937篇 |
2006年 | 844篇 |
2005年 | 725篇 |
2004年 | 597篇 |
2003年 | 588篇 |
2002年 | 458篇 |
2001年 | 381篇 |
2000年 | 324篇 |
1999年 | 241篇 |
1998年 | 234篇 |
1997年 | 175篇 |
1996年 | 165篇 |
1995年 | 172篇 |
1994年 | 127篇 |
1993年 | 106篇 |
1992年 | 97篇 |
1991年 | 56篇 |
1990年 | 41篇 |
1989年 | 33篇 |
1988年 | 19篇 |
1987年 | 17篇 |
1986年 | 17篇 |
1985年 | 34篇 |
1984年 | 22篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1971年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
122.
Simultaneous optimization of separation quality and analysis time of the micellar liquid chromatography of nine chlorophenol isomers was investigated. The effect on retention of three experimental parameters was studied using multivariate analysis. The factors studied were the concentration of sodium dodecyl sulfate, propanol content and pH of the mobile phase. The experiments were performed according to the face-centred cube central composite design and the inverse form of the experimental retention times for analytes were fitted to the polynomial models. The results of the analysis of variance showed that the models obtained explain greater than 99% of the variance observed in the chromatograms. Good predictive ability of the models was verified as high values of the statistics R2 and F were obtained for the linear relationship between predicted cross-validated and experimental values of the dependent variable. The study showed that the use of Pareto-optimality method, an approach from multi-criteria decision-making, allows the selection of the best possible combinations of separation and analysis time in micellar liquid chromatography of chlorophenols. 相似文献
123.
Christopher M. Micklitsch 《Tetrahedron letters》2006,47(35):6277-6280
A family of penta- and hexadentate metal ligating α-amino acids, suitably protected for Fmoc solid-phase chemistry, has been prepared. These residues incorporate the mono-amides of ethanolaminetriacetic acid, ethylenediaminetriacetic acid, and ethylenediaminetetraacetic acid as side chains. Side chains are tethered varying distances (n) from the Cα-carbon to allow metal binding events to occur at distinct distances from the peptide backbone. These residues are designed to allow the facile installation of metal chelates along a peptide backbone. 相似文献
124.
125.
Huwe A Mazitschek R Giannis A 《Angewandte Chemie (International ed. in English)》2003,42(19):2122-2138
Cell division (mitosis) is one of the basic requirements for multicellular oranisms. The capability of a cell to replicate enables a complex assembly to be created. Faulty regulation of the control mechanism in the cell cycle leads to an excessive cell proliferation and is the cause of cancer. The key position of the cyclin-dependent kinases (CDKs) and their direct partners, as well as the fact that the majority of malign illnesses show defects in at least one of these key players of the cell cycle, is of great interest for the development of low-molecular-weight CDK inhibitors. In this Review an overview of the different structural classes of ATP-competitive inhibitors of CDKs are given, whose devlopment was aimed at battling cancer. The Review shows how far the development of selective CDK inhibitors has progressed and to what extent the expectations for such drugs have so far been fulfilled. 相似文献
126.
An experimental mixture design was applied to a differential scanning calorimetry (DSC) study performed to evaluate naproxen
compatibility in tablet formulations consisting of four classic excipients (sorbitol, sodium carboxymethylcellulose, poly(ethylene
glycol) 20000 and Veegum) each in adequate concentration ranges accounting for the relevant values actually used in pharmaceutical
formulations. Twenty-seven different tablets were obtained from as many mixtures prepared according to the experimental design
plan and analyzed in a random order by DSC. Statistical evaluation of experimental data enabled correlation of both enthalpy
and onset temperature variations of drug melting endotherm (selected as responses indicative of the presence of drug-excipient
interactions) with the mixture composition. Variance analysis (Anova) confirmed the reliability of the postulated polynomial
model in providing adequate prediction of true system behaviour.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
127.
128.
One of the major techniques used for the method development of ternary and quaternary high performance liquid chromatography (HPLC) systems has been to use mixture designs, often referred to as "Glajch's Triangle". This technique does not allow for the systematic and simultaneous optimization of other factors such as gradient time, pH and temperature that affect the quality of separations. An alternative approach is to use experimental designs. The condition, however, that the composition of all components of the mobile phase must total 100% presents a problem when trying to mathematically represent ranges of each mobile phase constituent of a ternary or quaternary system. A method is described here, based on spherical coordinate representations, that adheres to the constraints of the mobile phase composition and allows experimental designs, such as central composite and factorial designs, to be applied to the simultaneous optimization of the mobile phase composition. Other factors, in particular temperature and gradient time, can then be included in the design. As a result of applying these designs to the HPLC separation of phenols and corticosteroids, it was found necessary to include three-way interactions between experimental factors in the model. The significance of these interactions shows that they need to be considered in HPLC method development. 相似文献
129.
Summary In this paper an application is presented of the median molecule workflow to the de novo design of novel molecular entities with a property profile of interest. Median molecules are structures that are optimised to be similar to a set of existing molecules of interest as an approach for lead exploration and hopping. An overview of this workflow is provided together with an example of an instance using the similarity to camphor and menthol as objectives. The methodology of the experiments is defined and the workflow is applied to designing novel molecules for two physical property datasets: mean molecular polarisability and aqueous solubility. This paper concludes with a discussion of the characteristics of this method. 相似文献
130.
Haifang Liu Yuanqiang Sun Zhaohui Li Ran Yang Jie Yang Aaron Albert Aryee Xiaoge Zhang Jia Ge Lingbo Qu Yuehe Lin 《中国化学快报》2019,30(9):1647-1651
Intracellular pH plays a significant role in various biological processes, including cell proliferation, apoptosis, metabolism, enzyme activity and homeostasis. In this work, a novel design strategy for the preparation of pH responsive carbon dots (CDs-pH) for ratiometric intracellular imaging was reported. By using SciFinder database, fluorescent CDs-pH with the required pKa value of 6.84 were rationally designed, which is vital important for precise sensing of intracellular pH. As a result, the synthesized CDs-pH demonstrated robust ability to test pH fluctuations within the physiological range of 5.4-7.4. The CDs-pH was further utilized for fluorescent ratiometric imaging of pH in living HeLa cells, effectively avoided the influence of autofluorescence from native cellular species. Moreover, real-time monitoring of intracellular pH fluctuation under heat shock was successfully realized. This SciFinder-guided design strategy is simple and flexible, which has a great potential to be used for the development of other types of CDs for various applications. 相似文献