全文获取类型
收费全文 | 46209篇 |
免费 | 15681篇 |
国内免费 | 58篇 |
专业分类
化学 | 55946篇 |
晶体学 | 51篇 |
力学 | 2035篇 |
数学 | 2660篇 |
物理学 | 1256篇 |
出版年
2024年 | 372篇 |
2023年 | 4083篇 |
2022年 | 1437篇 |
2021年 | 2472篇 |
2020年 | 4623篇 |
2019年 | 2310篇 |
2018年 | 2278篇 |
2017年 | 594篇 |
2016年 | 5571篇 |
2015年 | 5529篇 |
2014年 | 4941篇 |
2013年 | 5155篇 |
2012年 | 3213篇 |
2011年 | 1053篇 |
2010年 | 3414篇 |
2009年 | 3377篇 |
2008年 | 1053篇 |
2007年 | 777篇 |
2006年 | 140篇 |
2005年 | 115篇 |
2004年 | 91篇 |
1996年 | 98篇 |
1995年 | 152篇 |
1994年 | 102篇 |
1993年 | 224篇 |
1992年 | 110篇 |
1988年 | 126篇 |
1987年 | 108篇 |
1986年 | 91篇 |
1985年 | 110篇 |
1984年 | 121篇 |
1983年 | 107篇 |
1982年 | 136篇 |
1981年 | 169篇 |
1980年 | 202篇 |
1979年 | 191篇 |
1978年 | 199篇 |
1977年 | 326篇 |
1976年 | 374篇 |
1975年 | 469篇 |
1974年 | 480篇 |
1973年 | 293篇 |
1972年 | 373篇 |
1971年 | 360篇 |
1970年 | 543篇 |
1969年 | 418篇 |
1968年 | 459篇 |
1967年 | 119篇 |
1966年 | 91篇 |
1963年 | 114篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
Zur Entscheidungstheorie bei mehrfacher Zielsetzung 总被引:1,自引:0,他引:1
Zusammenfassung Der Begriff eines rationalen Lösunxgsprinzips für Entscheidungsprobleme mit mehrfacher Zielsetzung wird definitorisch eingeführt. Anhand der definierenden Bedingungen werden die neueren Lösungsansätze auf Rationalität untersucht. Zusätzlich wird besonderes Gewicht auf die kritische Untersuchung der den einzelnen Verfahren zugrundeliegenden Informationsannahmen gelegt. Dabei zeigt sich, wie auch aus empirischen Untersuchungen abgeleitet wird, daß es bei der Formulierung von Lösungsansätzen auf eine präzise Darstellung des Lösungsprinzips und der damit im Zusammenhang stehenden Informationsannahme ankommt; erst auf dieser Grundlage kann die entscheidungspraktische Relevanz solcher Verfahren überprüft werden.
Summary For multiobjective decision problems a notion of a rational solution principle is introduced by definition. The recently suggested solution approaches are tested for rationality under the defining conditions. Additionally, great importance is attached to the critical analysis of the information requirements underlying the different methods. It turns out, as well as it will be derived from empirical investigations, that a precise presentation of the solution principle and of the corresponding information requirements is indispensable formulating such approaches; first on this basis the practical relevance of solution procedures can be examined.相似文献
152.
Kevin D. Oliphant Marius Karger Yoichi Nakanishi Ralf R. Mendel 《Molecules (Basel, Switzerland)》2022,27(12)
Molybdenum (Mo) is an essential trace element in all kingdoms of life. Mo is bioavailable as the oxyanion molybdate and gains biological activity in eukaryotes when bound to molybdopterin, forming the molybdenum cofactor. The imbalance of molybdate homeostasis results in growth deficiencies or toxic symptoms within plants, fungi and animals. Recently, fluorescence resonance energy transfer (FRET) methods have emerged, monitoring cellular and subcellular molybdate distribution dynamics using a genetically encoded molybdate-specific FRET nanosensor, named MolyProbe. Here, we show that the MolyProbe system is a fast and reliable in vitro assay for quantitative molybdate determination. We added a Strep-TagII affinity tag to the MolyProbe protein for quick and easy purification. This MolyProbe is highly stable, resistant to freezing and can be stored for several weeks at 4 °C. Furthermore, the molybdate sensitivity of the assay peaked at low nM levels. Additionally, The MolyProbe was applied in vitro for quantitative molybdate determination in cell extracts of the plant Arabidopsis thaliana, the fungus Neurospora crassa and the yeast Saccharomyces cerevisiae. Our results show the functionality of the Arabidopsis thaliana molybdate transporter MOT1.1 and indicate that FRET-based molybdate detection is an excellent tool for measuring bioavailable Mo. 相似文献
153.
154.
Keitaro Tanoi Natsuko I. Kobayashi Takayuki Saito Naoko Iwata Atsushi Hirose Yoshimi Ohmae Ren Iwata Hisashi Suzuki Tomoko M. Nakanishi 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(2):749-751
The time course of Mg uptake and release using intact rice plants and 28Mg as a tracer is presented. Since there is no conventional Mg tracer available, 28Mg was produced via 27Al(α, 3p)28Mg reaction using a cyclotron. Using the purified 28Mg tracer, it was found that the uptake amount of 28Mg by the rice plants increased linearly during 30 min of application. After 28Mg treatment for 90 min, the roots were sequentially washed with iced solution for 120 min. Within about 10 min, almost all of the 28Mg, that was thought to be weakly bound to the apoplast, was washed away. 相似文献
155.
156.
157.
A solid state metathesis (SSM) reaction was investigated with respect to the formation of rare‐earth carbodiimides, the role of the co‐produced salt (LiCl), and the eutectic flux medium (LiCl/KCl). A SSM reaction is characterized by an exothermic reaction in which a salt (often LiCl) is coproduced. When the salt melts, it can serve as a useful medium for the crystallization of a desired product. An improved crystal growth can be observed by using an eutectic flux. However, the composition of an eutectic LiCl/KCl flux is altered when LiCl is produced during the reaction. The thermal effects concerning the endothermic melting of the flux and the exothermic ingnition of the SSM reaction may compensate each other, which is not necessarily a drawback for the reaction to proceed. 相似文献
158.
Maurits Kuiper Manfred Speldrich Helmut Schilder Prof. Dr. Heiko Lueken 《无机化学与普通化学杂志》2012,638(10):1432-1436
Abstract. The magnetic behavior of the mononuclear nd1 systems MCp2Cl2 (M = V4+[3d1], Nb4+[4d1], Ta4+[5d1], space group P21/c, pseudosymmetry of the molecules C2v) deviates from pure single ion spin magnetism on account of ligand field effect (Hlf), spin‐orbit coupling (Hso), and intermolecular spin‐spin exchange interactions (Hex). For both VCp2Cl2 and NbCp2Cl2 excellent adaptations to the measured susceptibility data were obtained (2 K ≤ T ≤ 300 K) on the basis of spectroscopic data (lf, so) and cooperative metal–metal interactions (ex) of antiferromagnetic nature [molecular field model (mf)]. For TaCp2Cl2 experimental term structure data are not available. Therefore, Jørgensen's spectroscopical series (g‐factor of the central ion) was applied to extrapolate the data set for TaCp2Cl2. Hlf, Hso, and Hex (antiferromagnetic) increase in the order 3d1 → 4d1 → 5d1 leading, with rising atomic number of the metals, to a distinct enhancement of the magnetic anisotropy. At 4 K the μeff components μeff,y (oriented perpendicular to the cg–M–cg plane; “cg” = center of gravity of the Cp ring), μeff,z (oriented along the twofold pseudoaxis), and μeff,x are 1.73, 1.69, 1.68 (V), 1.73, 1.62, 1.59 (Nb), and 1.71, 1.59, 1.49 (Ta). While μeff,y is independent of T, both μeff,z and μeff,x decrease with decreasing T. 相似文献
159.
160.