全文获取类型
收费全文 | 7814篇 |
免费 | 215篇 |
国内免费 | 20篇 |
专业分类
化学 | 5401篇 |
晶体学 | 36篇 |
力学 | 113篇 |
数学 | 1248篇 |
物理学 | 1251篇 |
出版年
2021年 | 60篇 |
2020年 | 80篇 |
2019年 | 97篇 |
2018年 | 56篇 |
2017年 | 62篇 |
2016年 | 156篇 |
2015年 | 144篇 |
2014年 | 166篇 |
2013年 | 297篇 |
2012年 | 300篇 |
2011年 | 364篇 |
2010年 | 230篇 |
2009年 | 188篇 |
2008年 | 320篇 |
2007年 | 324篇 |
2006年 | 301篇 |
2005年 | 283篇 |
2004年 | 282篇 |
2003年 | 234篇 |
2002年 | 233篇 |
2001年 | 143篇 |
2000年 | 167篇 |
1999年 | 117篇 |
1998年 | 131篇 |
1997年 | 112篇 |
1996年 | 128篇 |
1995年 | 166篇 |
1994年 | 146篇 |
1993年 | 110篇 |
1992年 | 103篇 |
1991年 | 102篇 |
1990年 | 88篇 |
1989年 | 100篇 |
1988年 | 96篇 |
1987年 | 85篇 |
1986年 | 82篇 |
1985年 | 127篇 |
1984年 | 96篇 |
1983年 | 99篇 |
1982年 | 115篇 |
1981年 | 103篇 |
1980年 | 97篇 |
1979年 | 104篇 |
1978年 | 84篇 |
1977年 | 85篇 |
1976年 | 67篇 |
1975年 | 64篇 |
1974年 | 71篇 |
1973年 | 82篇 |
1971年 | 57篇 |
排序方式: 共有8049条查询结果,搜索用时 234 毫秒
1.
2.
Ralf Freund Christos Allagiannis Peter Schnholzer Karl Bernauer 《Helvetica chimica acta》1994,77(3):615-621
A crude hydrate 6 and a crystalline hemiacetal 7 of glyoxylamide 4 were prepared from crotonamide 5 (Scheme 2). Particularly hemiacetal 7 , but also 6 and the ‘dimer’ 8 (obtained from 7 ) may serve as homochiral auxiliaries. The structure of 8 was determined by X-ray analysis. By arenesulfonyl halides, tryptimines 12–14 of 4 were diastereoselectively transformed into spirotricycles 15–17 and 19 . 相似文献
3.
Werner Leißner 《Results in Mathematics》1991,20(1-2):530-537
4.
We relate the Schramm–Loewner Evolution processes (SLE) to highest-weight representations of the Virasoro Algebra. The restriction properties of SLE that have been recently derived in [19] play a crucial role. In this setup, various considerations from conformal field theory can be interpreted and reformulated via SLE. This enables one to make a concrete link between the two-dimensional discrete critical systems from statistical physics and conformal field theory. To cite this article: R. Friedrich, W. Werner, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 947–952. 相似文献
5.
6.
7.
[3,3]-Sigmatropic rearrangements of allyl tetronates and allyl tetramates to give 3-allyltetronic or -tetramic acids, respectively, proceed within 20-60 min under microwave irradiation (300 W, 130-190 °C). Consecutive (homo)sigmatropic [1,5] H-shifts such as oxa-ene reactions are promoted less effectively, which allows the isolation of Claisen intermediates of sigmatropic domino sequences, in contrast to conventional heating. 相似文献
8.
Viviane Van Hoof Hugo Cluckers Vera Verhaeghe An Hennebel Marleen Truyens Edith Van Loock Pierre Rombouts Dirk Maes Jan Van Elven Katrien Lesage Mark Flothmann Lieve Nijs Filip Colpaert Werner Vercammen Dominique Bolain 《Accreditation and quality assurance》2004,10(1-2):55-59
In response to a change of the Belgian National Directives whereby hospital laboratories became responsible for all point-of-care testing (POCT) performed within hospital walls a standardized and automated POC glucose-testing system was implemented in our hospital. The system consists of 50 AccuCheck Inform instruments (Roche Diagnostics, Vilvoorde, Belgium), 50 docking stations, a DataCare Server, and connections to the medical laboratory information system (MOLIS, Sysmex, Barchon, Belgium) and to the hospital information system. Implementation involved many parties and extensive preparation and communication. Key issues were bar-coded patient and user identification, training, and responsibilities. One year after the hospital wide implementation of this system the quality of POC glucose testing has significantly increased, thereby improving patient safety. This study describes a stepwise change over involving the medical laboratory and with a focus on hands-on quality.Presented at the ninth conference on Quality in the Spotlight, 18–19 March 2004, Antwerp, Belgium. 相似文献
9.
We examine certain special features exhibited by various classes of linear operators acting in a hereditarily indecomposable
Banach space. For instance, we show that the family of all Riesz operators in a H.I. space forms a closed, 2-sided ideal.
We also give further characterizations of the class of scalar-type spectral operators (to those already given in [16]). The
final section discusses some properties of the spectral maximal spaces of (necessarily decomposable) linear operators in such
spaces.
Conferenza tenuta il 16 settembre 1997
The support of the German Academic Exchange Scheme (DAAD) is gratefully acknowledged 相似文献
10.
Entropy analysis and wavelet transforms are used to study the Southern Oscillation index (SOI) and multivariate ENSO index (MEI) indexes for the El Niño–Southern Oscillation. Trends to large decreasing symbolic chains responsible for La Niña and interrupted increasing chains for El Niño are found in the MEI persistence series. These are all located in regions where the wavelet transforms of both indexes reveal the existence of mid-range correlations. The SOI and MEI indexes are mutually correlated in a non-trivial manner in the time. 相似文献