全文获取类型
收费全文 | 1328篇 |
免费 | 142篇 |
国内免费 | 101篇 |
专业分类
化学 | 646篇 |
晶体学 | 4篇 |
力学 | 82篇 |
综合类 | 22篇 |
数学 | 569篇 |
物理学 | 248篇 |
出版年
2024年 | 2篇 |
2023年 | 10篇 |
2022年 | 26篇 |
2021年 | 22篇 |
2020年 | 27篇 |
2019年 | 42篇 |
2018年 | 25篇 |
2017年 | 35篇 |
2016年 | 60篇 |
2015年 | 50篇 |
2014年 | 65篇 |
2013年 | 96篇 |
2012年 | 58篇 |
2011年 | 82篇 |
2010年 | 73篇 |
2009年 | 83篇 |
2008年 | 84篇 |
2007年 | 78篇 |
2006年 | 76篇 |
2005年 | 82篇 |
2004年 | 77篇 |
2003年 | 88篇 |
2002年 | 61篇 |
2001年 | 53篇 |
2000年 | 38篇 |
1999年 | 32篇 |
1998年 | 27篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 10篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有1571条查询结果,搜索用时 15 毫秒
941.
Implementation of Hadamard encoding for rapid multisample analysis in liquid chromatography
下载免费PDF全文
![点击此处可从《Journal of separation science》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Multiplexing based on pseudo‐binary modulation sequences is known to increase the signal‐to‐noise ratio. In this work, Hadamard transform multiplexing is used in high‐performance liquid chromatography to increase the sample throughput. Using structured modulation sequences to encode and control sample injections in combination with a fitting algorithm to deconvolute the complex data allowed us to evaluate convoluted chromatograms of up to 128 samples containing three and five analytes, respectively, with good accuracy (<2% deviation). In comparison to conventional high‐performance liquid chromatography the analysis time could be reduced by 30 and 55%, respectively. 相似文献
942.
A FRET Probe for Cell‐Based Imaging of Ganglioside‐Processing Enzyme Activity and High‐Throughput Screening
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Guang‐Yu Yang Dr. Caishun Li Dr. Michael Fischer Prof. Christopher W. Cairo Prof. Yan Feng Prof. Stephen G. Withers 《Angewandte Chemie (International ed. in English)》2015,54(18):5389-5393
Gangliosides are important signaling molecules in the cell membrane and are processed by several enzymes. Deficiencies in these enzymes can cause human lysosomal storage diseases. Building an understanding of the pathways of glycosphingolipid catabolism requires methods for the analysis of these enzymatic activities A GM3‐derived FRET probe was synthesized chemoenzymatically for the detection and quantitation of a range of ganglioside‐degrading enzymes, both in cell lysates and in living cells. This is the first substrate that enables the ratiometric fluorogenic assay of sphingolipid ceramide N‐deacylase and endoglycoceramidase and can detect and localize neuraminidase activity in living cells. It is therefore a valuable tool for building a better understanding of membrane‐confined enzymology. It also enables the robust and reliable assay of ganglioside‐degrading enzymes in a microtiter plate, thus opening the door to screening for novel or engineered biocatalysts or for new inhibitors. 相似文献
943.
助剂和原料气中CO浓度对CuFeZr催化剂用于合成气制混合醇的影响 《燃料化学学报》2017,45(5):547-555
考察了不同助剂(Mn、Zn、Co)对CuFeZr催化剂用于合成气制混合醇的影响。借助BET、XRD、H2-TPR等对其物化性质进行了表征,结果表明,加入助剂可减小颗粒粒径并且增强对CO的吸附能力以及催化剂表面碱性,其中,加入Zn可以增强CuFe间的相互作用,改善CuFeZr催化剂的还原性质,提高对CO的吸附能力,以及提供最强的表面碱性。用固定床反应器对催化剂的反应性能进行了评价,反应结果表明,加入Zn可以显著提高CuFeZr催化剂用于合成气制混合醇的反应活性及醇选择性,使醇时空收率从0.026 g/(gcat·h)提高至0.071 g/(gcat·h)。由于循环条件下,反应产物CO2同时也是原料气的组成成分,进一步地探究了原料气中CO2浓度对催化剂反应性能的影响。结果表明,加入CO2可提高CO转化率和醇以及烃的收率,但阻碍链增长反应并使得产物烯烷比降低。其中,在所考察浓度范围内,原料气中含有2.5%的CO2最有利于醇和烃的生成尤其是低碳醇和低碳烃的生成。 相似文献
944.
K. V. Stepanyantz 《Theoretical and Mathematical Physics》2007,150(3):377-392
We use the Schwinger-Dyson equations and Slavnov-Tailor identities to obtain the contribution of matter fields to the Gell-Mann-Low
function for the
supersymmetric Yang-Mills theory regularized by higher covariant derivatives. We discuss the possible deviation of the result
from the corresponding contribution to the exact Novikov-Shifman-Vainshtein-Zakharov β-function.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 150, No. 3, pp. 441–460, March, 2007. 相似文献
945.
研究了一类亚纯函数系数的高阶线性微分方程的解的不动点问题,应用值分布的理论和方法,得到了复域微分方程亚纯解的不动点性质. 相似文献
946.
Hamberg A Lundgren S Wingstrand E Moberg C Hult K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(15):4334-4341
The yields and optical purities of products obtained from chiral Lewis acid/Lewis base-catalysed additions of alpha-ketonitriles to prochiral aldehydes could be accurately determined by an enzymatic method. The amount of remaining aldehyde was determined after its reduction to an alcohol, whilst the two product enantiomers were analysed after subsequent hydrolysis first by the (S)-selective Candida antarctica lipase B and then by the unselective pig liver esterase. The method could be used for analysis of products obtained from a number of aromatic aldehydes and aliphatic ketonitriles. Microreactor technology was successfully combined with high-throughput analysis for efficient catalyst optimization. 相似文献
947.
Konstantou J Ioannou PC Christopoulos TK 《Analytical and bioanalytical chemistry》2007,388(8):1747-1754
Primer extension reaction (PEXT) is the most widely used approach to genotyping of single nucleotide polymorphisms (SNP).
It is based on the high accuracy of nucleotide incorporation by the DNA polymerase. We propose a dual-analyte bio/chemiluminometric
method for the simultaneous detection of the PEXT reaction products of the normal and mutant allele in a high sample-throughput
format. PCR-amplified DNA fragments that span the SNP of interest are subjected to two PEXT reactions using normal and mutant
primers in the presence of digoxigenin-dUTP and biotin-dUTP. Both primers contain a d(A)30 segment at the 5′-end but differ in the final nucleotide at the 3′-end. Under optimized conditions only the primer that is
perfectly complementary with the interrogated DNA will be extended by DNA polymerase and lead to a digoxigenin- or biotin-labeled
product. The products of the PEXT reactions are mixed, denatured, and captured in microtiter wells through hybridization with
immobilized oligo(dT) strands. Detection is performed by adding a mixture of antidigoxigenin–alkaline phosphatase (ALP) conjugate
and a streptavidin–aequorin conjugate. The flash-type bioluminescent reaction of aequorin is triggered by the addition of
Ca2+. ALP is then measured by adding the appropriate chemiluminogenic substrate. The method was evaluated by genotyping two SNPs
of the human mannose-binding lectin gene (MBL2) and one SNP of the cytochrome P450 gene CYP2D6. Patient genotypes showed 100%
concordance with direct DNA sequencing data. 相似文献
948.
949.
Golotvin SS Vodopianov E Pol R Lefebvre BA Williams AJ Rutkowske RD Spitzer TD 《Magnetic resonance in chemistry : MRC》2007,45(10):803-813
A method for structure validation based on the simultaneous analysis of a 1D (1)H NMR and 2D (1)H - (13)C single-bond correlation spectrum such as HSQC or HMQC is presented here. When compared with the validation of a structure by a 1D (1)H NMR spectrum alone, the advantage of including a 2D HSQC spectrum in structure validation is that it adds not only the information of (13)C shifts, but also which proton shifts they are directly coupled to, and an indication of which methylene protons are diastereotopic. The lack of corresponding peaks in the 2D spectrum that appear in the 1D (1)H spectrum, also gives a clear picture of which protons are attached to heteroatoms. For all these benefits, combined NMR verification was expected and found by all metrics to be superior to validation by 1D (1)H NMR alone. Using multiple real-life data sets of chemical structures and the corresponding 1D and 2D data, it was possible to unambiguously identify at least 90% of the correct structures. As part of this test, challenging incorrect structures, mostly regioisomers, were also matched with each spectrum set. For these incorrect structures, the false positive rate was observed as low as 6%. 相似文献
950.
Masaya Kitamura Kiminori Kawakami Naotoshi Nakamura Kouhei Tsumoto Hidefumi Uchiyama Yoshitaka Ueda Izumi Kumagai Tadao Nakaya 《Journal of polymer science. Part A, Polymer chemistry》1999,37(6):729-736
An expression system for a chemically synthesized gene, encoding a model peptide of marine mussel adhesive protein, was constructed in Escherichia coli under regulation of the T7‐promoter. The model peptide consisted of six repeats of the decapeptide AKPSYPPTYK. Although the product was expressed as an inclusion body, we were able to solubilize it successfully, using acetic acid. The higher‐order structure of this model peptide was investigated using CD spectroscopy and NMR spectroscopy. Using the modified enzyme, mushroom tyrosinase, the tyrosine residue was hydroxylated to 3,4‐dihydoxyphenylalanine (Dopa), and the resulting modified peptide was polymerized, solidified, and insolubilized spontaneously. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 729–736, 1999 相似文献