全文获取类型
收费全文 | 4277篇 |
免费 | 128篇 |
国内免费 | 20篇 |
专业分类
化学 | 2774篇 |
晶体学 | 19篇 |
力学 | 129篇 |
数学 | 743篇 |
物理学 | 760篇 |
出版年
2023年 | 31篇 |
2022年 | 73篇 |
2021年 | 86篇 |
2020年 | 82篇 |
2019年 | 87篇 |
2018年 | 71篇 |
2017年 | 48篇 |
2016年 | 114篇 |
2015年 | 104篇 |
2014年 | 114篇 |
2013年 | 183篇 |
2012年 | 226篇 |
2011年 | 318篇 |
2010年 | 184篇 |
2009年 | 175篇 |
2008年 | 232篇 |
2007年 | 225篇 |
2006年 | 222篇 |
2005年 | 170篇 |
2004年 | 152篇 |
2003年 | 135篇 |
2002年 | 143篇 |
2001年 | 55篇 |
2000年 | 45篇 |
1999年 | 41篇 |
1998年 | 29篇 |
1997年 | 39篇 |
1996年 | 62篇 |
1995年 | 36篇 |
1994年 | 48篇 |
1993年 | 38篇 |
1992年 | 35篇 |
1991年 | 33篇 |
1990年 | 31篇 |
1989年 | 22篇 |
1988年 | 31篇 |
1987年 | 21篇 |
1986年 | 27篇 |
1985年 | 54篇 |
1984年 | 59篇 |
1983年 | 41篇 |
1982年 | 36篇 |
1981年 | 42篇 |
1980年 | 45篇 |
1979年 | 49篇 |
1978年 | 25篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1974年 | 19篇 |
1970年 | 17篇 |
排序方式: 共有4425条查询结果,搜索用时 15 毫秒
21.
22.
23.
Bassan Bruno Gossner Olivier Scarsini Marco Zamir Shmuel 《International Journal of Game Theory》2003,32(1):17-31
We exhibit a general class of interactive decision situations in which all the agents benefit from more information. This class includes as a special case the classical comparison of statistical experiments à la Blackwell.
AMS 2000 Subject Classification:Primary 91A35.The work of Bruno Bassan and Marco Scarsini was partially supported by MIUR-COFIN. The authors express their thanks to Sylvain Sorin for enlightening comments. 相似文献
24.
25.
26.
The role of the tunneling mechanisms in metal-disordered layer-semiconductor structure under spin injection at the interface is investigated. The non-ideal metal-semiconductor structure as prepared by ionized cluster beam deposition is considered, and it is shown that the depletion region of the semiconductor can be tailored to include a suitably heavily doped region near the interface. The tunneling is described within a simplified model in which the expression for the interface resistance of the metal-disordered layer-semiconductor structure is obtained. It is argued that in the case of ionized cluster beam deposited non-ideal Schottky structure a significant spin injection is achieved. 相似文献
27.
Giovanni Bruno Maria M. Giangregorio April S. Brown Soojeong Choi 《Applied Surface Science》2006,253(1):219-223
GaN is grown on Si-face 4H-SiC(0 0 0 1) substrates using remote plasma-assisted methods including metalorganic chemical vapour deposition (RP-MOCVD) and molecular beam epitaxy (MBE). Real time spectroscopic ellipsometry is used for monitoring all the steps of substrate pre-treatments and the heteroepitaxial growth of GaN on SiC. Our characterization emphasis is on understanding the nucleation mechanism and the GaN growth mode, which depend on the SiC surface preparation. 相似文献
28.
A rapid, selective and reproducible high-performance liquid chromatographic (HPLC) method with ultraviolet detection was developed for the determination of the anti-cancer agent Taxotere in biological fluids. The method involves a solid-phase extraction step (C2 ethyl microcolumns) using a Varian Advanced Automated Sample Processor (AASP) followed by reversed-phase HPLC. The validated quantitation range of the method is 10-2500 ng/ml in plasma with coefficients of variation < or = 11%. The method is also suitable for the determination of Taxotere in urine samples under the same conditions. The method was applied in a phase I tolerance study of Taxotere in cancer patients, allowing the pharmacokinetic profile of Taxotere to be established. 相似文献
29.
The self‐complementary tetrameric propargyl triols 8, 14, 18 , and 21 were synthesized to investigate the duplex formation of self‐complementary, ethynylene‐linked UUAA, AAUU, UAUA, and AUAU analogues with integrated bases and backbone (ONIBs). The linear synthesis is based on repetitive Sonogashira couplings and C‐desilylations (34–72% yield), starting from the monomeric propargyl alcohols 9 and 15 and the iodinated nucleosides 3, 7, 11 , and 13 . Strongly persistent intramolecular H‐bonds from the propargylic OH groups to N(3) of the adenosine units prevent the gg‐type orientation of the ethynyl groups at C(5′). As such, an orientation is required for the formation of cyclic duplexes, this H‐bond prevents the formation of duplexes connected by all four base pairs. However, the central units of the UAUA and AAUU analogues 18 and 14 associate in CDCl3/(D6)DMSO 10 : 1 to form a cyclic duplex characterized by reverse Hoogsteen base pairing. The UUAA tetramer 8 forms a cyclic UU homoduplex, while the AUAU tetramer 21 forms only linear associates. Duplex formation of the O‐silylated UUAA and AAUU tetramers is no longer prevented. The self‐complementary UUAA tetramer 22 forms Watson–Crick‐ and Hoogsteen‐type base‐paired cyclic duplexes more readily than the sequence‐isomeric AAUU tetramer 23 , further illustrating the sequence selectivity of duplex formation. 相似文献
30.
V. Nastro D. Vuono M. Guzzo G. Niceforo I. Bruno P. De
Luca 《Journal of Thermal Analysis and Calorimetry》2006,84(1):181-184
The aim of this paper is to characterize some raw
materials used for ceramics material production. Five samples of clay have
been analyzed. It has been carried out a patterned sampling in a quarry in
Rosarno (South Italy).
Chemical-physical
properties on clay samples are determined. Test pieces have been prepared
and physical properties after firing are determined by DSC thermal analysis,
XRD analysis and X-ray fluorescence. It is important to note the high amount
of Fe2O3. The mixture principally
contains quartz, illite and oligoclase. It has been observed the colour and
the shape after firing: predominant colour is red. In this case the clay has
been used in mixtures covered with glazes. The colour of internal clay is
hidden by opaque of glazes. The analysed raw materials can be used in a slip
for single fired red tiles. The A2sp clay produces best ceramics at 1000°C. 相似文献