全文获取类型
收费全文 | 30516篇 |
免费 | 1030篇 |
国内免费 | 17篇 |
专业分类
化学 | 21033篇 |
晶体学 | 229篇 |
力学 | 556篇 |
数学 | 4167篇 |
物理学 | 5578篇 |
出版年
2023年 | 251篇 |
2022年 | 181篇 |
2021年 | 358篇 |
2020年 | 507篇 |
2019年 | 468篇 |
2018年 | 669篇 |
2017年 | 617篇 |
2016年 | 1189篇 |
2015年 | 960篇 |
2014年 | 954篇 |
2013年 | 1989篇 |
2012年 | 2208篇 |
2011年 | 2351篇 |
2010年 | 1358篇 |
2009年 | 1082篇 |
2008年 | 1981篇 |
2007年 | 1939篇 |
2006年 | 1704篇 |
2005年 | 1522篇 |
2004年 | 1234篇 |
2003年 | 937篇 |
2002年 | 846篇 |
2001年 | 652篇 |
2000年 | 545篇 |
1999年 | 409篇 |
1998年 | 293篇 |
1997年 | 213篇 |
1996年 | 334篇 |
1995年 | 220篇 |
1994年 | 213篇 |
1993年 | 265篇 |
1992年 | 233篇 |
1991年 | 154篇 |
1990年 | 142篇 |
1989年 | 120篇 |
1988年 | 123篇 |
1987年 | 120篇 |
1986年 | 116篇 |
1985年 | 179篇 |
1984年 | 143篇 |
1983年 | 119篇 |
1982年 | 106篇 |
1981年 | 99篇 |
1980年 | 75篇 |
1979年 | 91篇 |
1978年 | 80篇 |
1977年 | 74篇 |
1976年 | 76篇 |
1975年 | 70篇 |
1973年 | 81篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
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
42.
43.
44.
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
45.
Ferric ferrocyanides synthesized from different sources of ferric cations and ferrocyanide anions and those derived from ferrous ferricyanide, ferrous ferrocyanide and ferric ferricyanide have been studied using Mössbauer and XRD techniques. Structural information of the effect of the provenance on the properties of the final compound is obtained. Significant correlations between isomer shift and quadrupole splitting of inner and outer iron cations have been observed. 相似文献
46.
Using the time differential perturbed angular correlation technique, the hyperfine interactions as titanium sites in ZnTiF6·6H2O and its decomposition products were determined between room temperature (300 K) and 1273 K. The different steps in the decomposition pattern were identified and a simple model is given for it. 相似文献
47.
Yi Liu David D. Díaz Adrian A. Accurso K. Barry Sharpless Valery V. Fokin M. G. Finn 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5182-5189
1,2,3‐Triazole‐based polymers generated from the Cu(I)‐catalyzed cycloaddition between multivalent azides and acetylenes are effective adhesive materials for metal surfaces. The adhesive capacities of candidate mixtures of azide and alkyne components were measured by a modified peel test, using a customized adhesive tester. A particularly effective tetravalent alkyne and trivalent azide combination was identified, giving exceptional strength that matches or exceeds the best commercial formulations. The addition of Cu catalyst was found to be important for the synthesis of stronger adhesive polymers when cured at room temperature. Heating also accelerated curing rates, but the maximum adhesive strengths achieved at both room temperature and high temperature were the same, suggesting that crosslinking reaches the same advanced point in all cases. Polytriazoles also form adhesives to aluminum, but copper is bound more effectively, presumably because active Cu(I) ions may be leached from the surface to promote crosslinking and adhesion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5182–5189, 2007 相似文献
48.
František Toman Ludvík Beneš 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):231-236
Differential molar adsorption enthalpies (DMAE) were determined by gas chromatographic measurements of specific retention
volume of vapors on the surface of two forms of Mg–Al hydrotalcite. A linear dependence of the DMAE on the number of the carbon
atoms in hydrocarbons was observed for both form of hydrotalcite. The dependence of the differential molar adsorption enthalpies
on the number of chlorine atoms in organic molecules is discussed. A linear dependence of DMAE on the molecular weight of
chloroderivatives of methane and ethylene on the basic form in an order monochloromethane < dichloromethane < trichloromethane
or vinylidene chloride < 1,1-dichloroethylene < trichloroethylene was found. 相似文献
49.
50.
If a and b are trace-class operators, and if u is a partial isometry, then , where ∥⋅∥1 denotes the norm in the trace class. The present paper characterises the cases of equality in this Young inequality, and
the characterisation is examined in the context of both the operator and the Hilbert–Schmidt forms of Young's inequality.
Received: 20 December 2001 / Revised version: 11 July 2002 / Published online: 10 February 2003
Mathematics Subject Classification (2000): 47A63, 15A60 相似文献