全文获取类型
收费全文 | 3737篇 |
免费 | 447篇 |
国内免费 | 345篇 |
专业分类
化学 | 4341篇 |
晶体学 | 14篇 |
力学 | 4篇 |
综合类 | 52篇 |
数学 | 14篇 |
物理学 | 104篇 |
出版年
2024年 | 8篇 |
2023年 | 41篇 |
2022年 | 277篇 |
2021年 | 252篇 |
2020年 | 211篇 |
2019年 | 139篇 |
2018年 | 107篇 |
2017年 | 112篇 |
2016年 | 172篇 |
2015年 | 185篇 |
2014年 | 185篇 |
2013年 | 259篇 |
2012年 | 275篇 |
2011年 | 155篇 |
2010年 | 159篇 |
2009年 | 193篇 |
2008年 | 188篇 |
2007年 | 165篇 |
2006年 | 192篇 |
2005年 | 164篇 |
2004年 | 164篇 |
2003年 | 155篇 |
2002年 | 157篇 |
2001年 | 64篇 |
2000年 | 73篇 |
1999年 | 67篇 |
1998年 | 66篇 |
1997年 | 63篇 |
1996年 | 51篇 |
1995年 | 49篇 |
1994年 | 33篇 |
1993年 | 27篇 |
1992年 | 20篇 |
1991年 | 11篇 |
1990年 | 15篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 12篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有4529条查询结果,搜索用时 15 毫秒
991.
P. Buisson H. El Rassy S. Maury A.C. Pierre 《Journal of Sol-Gel Science and Technology》2003,27(3):373-379
The effect of the lipase from Burkholderia cepacia (previously known as Pseudomonas cepacia) on the gelation kinetics and gel structure was examined on a type of silica aerogel made from a mixture of methyltrimethoxysilane and tetramethoxysilane. For this purpose, gels were made with increasing concentrations of lipase in otherwise constant other conditions (pH, water and Si precursors concentrations). It was found that the enzyme accelerated the gelation kinetics, hence was participating in some way to the hydrolysis of the silica precursor. The structure of the gel was simultaneously modified to produce an increasing proportion of Q4 silicon sites. 相似文献
992.
Ekilik V. V. Svyataya M. N. Berezhnaya A. G. 《Russian Journal of Electrochemistry》2003,39(8):857-862
Acridine derivatives as inhibitors of diffusion- and diffusion–kinetic-controlled dissolution of -brass are studied. Inhibition coefficients of the dissolution and its steps correlate with parameters of a standard reaction series and wavelengths of the longest-wave absorption band of the electronic spectrum. 相似文献
993.
994.
Summary The use of solid-phase reactors for post-column derivatization in narrow-bore HPLC (1.0mm i.d. analytical columns) is evaluated.
Two systems are described, viz. for the determination of N-methylcarbamate pesticides and for that of urea and ammonia. The
solid-phase reactor is packed with a strong anion exchange resin and urease immobilized on silica, respectively, to effect
the catalytic hydrolysis of the solutes eluting from the analytical column. In both systems, the hydrolysis product is reacted
with o-phthalaldehyde followed by fluorescence monitoring.
Analytical data are presented and band broadening from various parts of the reaction detector system is discussed. An on-line
trace enrichment procedure via a micro precolumn is descried for the trace level determination of N-methylcaramates in surface
water samples. 相似文献
995.
Immobilizing enzymes: how to create more suitable biocatalysts 总被引:8,自引:0,他引:8
Bornscheuer UT 《Angewandte Chemie (International ed. in English)》2003,42(29):3336-3337
996.
J.D. Campbell D.A. Harrington P. van den Driessche J. Watmough 《Journal of mathematical chemistry》2002,32(3):281-301
The linear stability problem for surface mechanisms with free sites and two adsorbed species is investigated under the assumptions of mass action (Langmuir) surface kinetics, fast mass transport to and from the surface, and a conservation condition. The results also apply to enzyme kinetics for systems with a single enzyme occurring in the free form and two combined forms, and with fast mass transport of the substrates and products. Mechanisms are classified according to their stability and the presence or absence of complex eigenvalues, and specific reactions with numerical values of the rate constants and surface concentrations are given to illustrate the results. Some mechanisms, e.g., proportionate reactions, are shown to be stable for all values of the rate constants and stoichiometric coefficients. The two most common types of mechanisms, namely sequential mechanisms and the simple Langmuir–Hinshelwood mechanism (one adsorbate per site), are always stable. The possibility of complex eigenvalues arises for sequential mechanisms (providing a counterexample to a condition for real eigenvalues given previously in the literature). More general Langmuir–Hinshelwood mechanisms can be unstable (e.g., those in which one adsorbate occupies two sites). Some results are generalized to mechanisms with three or more adsorbed species, and global stability is investigated using monotone dynamical systems theory. 相似文献
997.
998.
Marija Berendika Sandra Domjani Drozdek Dyana Odeh Nada Oroli Petar Dragi
evi Marijana Sokolovi Ivona Elez Garofuli Domagoj iki Irena Landeka Jur
evi 《Molecules (Basel, Switzerland)》2022,27(2)
Polyphenols of Laurel and Myrtle exhibit structural diversity, which affects bioavailability, metabolism, and bioactivity. The gut microbiota plays a key role in modulating the production, bioavailability and, thus the biological activities of phenolic metabolites, particularly after the intake of food containing high-molecular-weight polyphenols. The aim of this study was to investigate whether the polyphenolic components of Laurel and Myrtle aqueous extract have beneficial effects on rat health. The growth of lactic acid bacteria (LAB), β-glucuronidase, β-glucosidase, β-galactosidase activity, pH value, body weight change and food efficacy ratio after intragastric treatment of rats with Laurel and Myrtle extract at doses of 50 and 100 mg/kg for two weeks were investigated. The endogenous populations of colonic probiotic bacteria (Lactobacilli and Bifidobacteria) were counted on selective media. According to the obtained data, Laurel extract in the applied dose of 50 and 100 and Myrtle extract (100 mg/kg) positively affects the rats health by increasing the number of colonies of Lactobacilli and Bifidobacteria compared to the control group, causes changes in glycolytic enzymatic activity and minor change in antioxidative tissue activity. In addition, high doses of Laurel increase food efficiency ratio, while Myrtle has the same effect at a lower dose. 相似文献
999.
Dibyendu Dana Tuhin Das Athena Choi Ashif I. Bhuiyan Tirtha K. Das Tanaji T. Talele Sanjai K. Pathak 《Molecules (Basel, Switzerland)》2022,27(2)
Cell cycle kinases represent an important component of the cell machinery that controls signal transduction involved in cell proliferation, growth, and differentiation. Nek2 is a mitotic Ser/Thr kinase that localizes predominantly to centrosomes and kinetochores and orchestrates centrosome disjunction and faithful chromosomal segregation. Its activity is tightly regulated during the cell cycle with the help of other kinases and phosphatases and via proteasomal degradation. Increased levels of Nek2 kinase can promote centrosome amplification (CA), mitotic defects, chromosome instability (CIN), tumor growth, and cancer metastasis. While it remains a highly attractive target for the development of anti-cancer therapeutics, several new roles of the Nek2 enzyme have recently emerged: these include drug resistance, bone, ciliopathies, immune and kidney diseases, and parasitic diseases such as malaria. Therefore, Nek2 is at the interface of multiple cellular processes and can influence numerous cellular signaling networks. Herein, we provide a critical overview of Nek2 kinase biology and discuss the signaling roles it plays in both normal and diseased human physiology. While the majority of research efforts over the last two decades have focused on the roles of Nek2 kinase in tumor development and cancer metastasis, the signaling mechanisms involving the key players associated with several other notable human diseases are highlighted here. We summarize the efforts made so far to develop Nek2 inhibitory small molecules, illustrate their action modalities, and provide our opinion on the future of Nek2-targeted therapeutics. It is anticipated that the functional inhibition of Nek2 kinase will be a key strategy going forward in drug development, with applications across multiple human diseases. 相似文献
1000.
Deep machine learning is expanding the conceptual framework and capacity of computational compound design, enabling new applications through generative modeling. We have explored the systematic design of covalent protein kinase inhibitors by learning from kinome-relevant chemical space, followed by focusing on an exemplary kinase of interest. Covalent inhibitors experience a renaissance in drug discovery, especially for targeting protein kinases. However, computational design of this class of inhibitors has thus far only been little investigated. To this end, we have devised a computational approach combining fragment-based design and deep generative modeling augmented by three-dimensional pharmacophore screening. This approach is thought to be particularly relevant for medicinal chemistry applications because it combines knowledge-based elements with deep learning and is chemically intuitive. As an exemplary application, we report for Bruton’s tyrosine kinase (BTK), a major drug target for the treatment of inflammatory diseases and leukemia, the generation of novel candidate inhibitors with a specific chemically reactive group for covalent modification, requiring only little target-specific compound information to guide the design efforts. Newly generated compounds include known inhibitors and characteristic substructures and many novel candidates, thus lending credence to the computational approach, which is readily applicable to other targets. 相似文献