全文获取类型
收费全文 | 84716篇 |
免费 | 16530篇 |
国内免费 | 1510篇 |
专业分类
化学 | 82320篇 |
晶体学 | 368篇 |
力学 | 2819篇 |
综合类 | 10篇 |
数学 | 8336篇 |
物理学 | 8903篇 |
出版年
2024年 | 388篇 |
2023年 | 4251篇 |
2022年 | 1894篇 |
2021年 | 3057篇 |
2020年 | 5094篇 |
2019年 | 2860篇 |
2018年 | 3005篇 |
2017年 | 1350篇 |
2016年 | 6779篇 |
2015年 | 6458篇 |
2014年 | 6011篇 |
2013年 | 7647篇 |
2012年 | 6036篇 |
2011年 | 4218篇 |
2010年 | 5133篇 |
2009年 | 5104篇 |
2008年 | 3476篇 |
2007年 | 3159篇 |
2006年 | 2240篇 |
2005年 | 2101篇 |
2004年 | 2150篇 |
2003年 | 1584篇 |
2002年 | 1441篇 |
2001年 | 931篇 |
2000年 | 765篇 |
1999年 | 595篇 |
1998年 | 494篇 |
1997年 | 455篇 |
1996年 | 534篇 |
1995年 | 475篇 |
1994年 | 381篇 |
1993年 | 562篇 |
1992年 | 394篇 |
1985年 | 343篇 |
1984年 | 323篇 |
1982年 | 279篇 |
1981年 | 302篇 |
1980年 | 312篇 |
1979年 | 307篇 |
1978年 | 292篇 |
1977年 | 411篇 |
1976年 | 456篇 |
1975年 | 549篇 |
1974年 | 553篇 |
1973年 | 383篇 |
1972年 | 424篇 |
1971年 | 406篇 |
1970年 | 599篇 |
1969年 | 478篇 |
1968年 | 519篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
J. A. Murillo J. M. Lemus L. F. García 《Analytical and bioanalytical chemistry》1994,349(10-11):761-767
First-derivative spectrophotometric method with a “zero-crossing” technique of measurement has been used for the quantification of two-components mixtures of cephalothin and clavulanic acid. As the absorption bands of these drugs overlap, both direct and derivative spectrophotometric methods have been investigated and evaluated by a rigorous statistical analysis of the experimental data. The first-derivative spectrophotometric method was found to be more accurate, direct and reproducible. Beer's law was valid over the concentration range 2.0–28.0 mg/l for both compounds. The detection limits of cephalothin and clavulanic acid, at a 0.05 level of significance, were calculated to be 0.13 and 0.15 mg/l. The method was applied for determining these antibiotics in mixtures, some of them containing inject-able dosage forms of cephalothin, and so to determine both compounds in saline and glucosed physiological sera. 相似文献
102.
Introduction The studies of diorganotin(IV) complexes are of current interest owing to their wide range of applica-tions such as biocides and homogeneous catalysts in industry.1 In recent years there have been more and more reports on the synthesis, antitumour activities and structural elucidation of various diorganotin(IV) deriva-tives of carboxylic acid.2-5 In particular, people take considerable interest in structural studies of diorgano-tin(IV) complexes of carboxylic acid, because there… 相似文献
103.
Juan F García-Reyes Pilar Ortega-Barrales Antonio Molina-Díaz 《Analytical sciences》2007,23(4):423-428
A combined approach based on solid-phase optosensing and multicommutation principles has been applied to develop a method for the simultaneous analysis of two pharmaceuticals (naproxen and salicylic acid) in biological fluids. The multicommuted flow-through optosensor was based on direct native fluorescence measurements of both analgesics using a non-polar sorbent (C18 silica gel) as a solid sensing zone. The flow system was controlled by Java-written home-made software and designed using three-way solenoid valves for an independent automated manipulation of sample and carrier solutions. Using an optimized sampling time, the method was calibrated in the range of 1 - 25 and 5 - 200 ng mL(-1). The obtained detection limits were 0.3 and 1.3 ng mL(-1) for naproxen and salicylic acid, respectively, with RSD (%) values of better than 2% for both analytes. The proposed methodology was successfully applied to urine, serum and pharmaceutical preparations. Recovery percentages ranging from 96.1 to 104% were obtained for both analytes. 相似文献
104.
Dr. S. Jayaraj 《Heat and Mass Transfer》1995,30(3):167-173
This paper deals with the analysis of two dimensional laminar thermophoretic flow over inclined plates. Cold wall conditions are assumed and the governing equations are solved by a finite difference marching technique. Results for the hydrodynamic, thermal and particle concentration boundary layers are obtained over a wide range of parameters. Special emphasis is placed on the external aerosol particle deposition process. 相似文献
105.
106.
Univ.-Prof. Dr-Ing. J. Betten Univ.-Prof. Dr.-Ing. E. El-Magd Dr.-Ing. S. C. Meydanli Dipl.-Ing. P. Palmen 《Archive of Applied Mechanics (Ingenieur Archiv)》1995,65(2):121-132
Übersicht Ziel der Untersuchung ist es, den Einfluß von Kriechschädigung und Belastungsvorgeschichte auf das weitere Kriechverhalten nach einer Änderung der Belastungsrichtung zu bestimmen. Die ermittelten Kriechbruchzeiten werden stark von der Änderung der Belastungsrichtung beeinflußt. Dieses Verhalten wird mit einer tensoriell nichtlinearen Theorie erklärt, indem man den Einfluß der Vorschädigung mit einem zweistufigen Tensor darstellt.
相似文献
相似文献
107.
The concept of a self-consistent field is developed within the version of density functional theory based on local-scaling transformations. It is shown that in this context there arise two types of consistency: one relating to the charge-consistency within an orbit and another to “orbit jumping.” The latter is analyzed in terms of one-particle equations. The connection with other methods is discussed. © 1992 John Wiley & Sons, Inc. 相似文献
108.
109.
Cooperative games are considered where only those coalitions of players are feasible that respect a given precedence structure on the set of players. Strengthening the classical symmetry axiom, we obtain three axioms that give rise to a unique Shapley value in this model. The Shapley value is seen to reflect the expected marginal contribution of a player to a feasible random coalition, which allows us to evaluate the Shapley value nondeterministically. We show that every exact algorithm for the Shapley value requires an exponential number of operations already in the classical case and that even restriction to simple games is #P-hard in general. Furthermore, we outline how the multi-choice cooperative games of Hsiao and Raghavan can be treated in our context, which leads to a Shapley value that does not depend on pre-assigned weights. Finally, the relationship between the Shapley value and the permission value of Gilles, Owen and van den Brink is discussed. Both refer to formally similar models of cooperative games but reflect complementary interpretations of the precedence constraints and thus give rise to fundamentally different solution concepts. 相似文献
110.
In this article we prove a local existence and uniqueness theorem for the Kadomtsev-Petviashvili Equation (u
t
+u
xxx
+uu
x
)
x
−u
yy
=0) in the Sobolev spaces of orders≥3, with initial values in the same spaces, and periodic boundary conditions. This theorem improves previous results based
upon the application of singular perturbation techniques. 相似文献