全文获取类型
收费全文 | 29255篇 |
免费 | 803篇 |
国内免费 | 235篇 |
专业分类
化学 | 19817篇 |
晶体学 | 143篇 |
力学 | 662篇 |
综合类 | 1篇 |
数学 | 5485篇 |
物理学 | 4185篇 |
出版年
2022年 | 191篇 |
2021年 | 282篇 |
2020年 | 350篇 |
2019年 | 318篇 |
2018年 | 278篇 |
2017年 | 295篇 |
2016年 | 607篇 |
2015年 | 629篇 |
2014年 | 673篇 |
2013年 | 1424篇 |
2012年 | 1432篇 |
2011年 | 1750篇 |
2010年 | 973篇 |
2009年 | 837篇 |
2008年 | 1484篇 |
2007年 | 1491篇 |
2006年 | 1591篇 |
2005年 | 1437篇 |
2004年 | 1348篇 |
2003年 | 1125篇 |
2002年 | 1065篇 |
2001年 | 489篇 |
2000年 | 439篇 |
1999年 | 410篇 |
1998年 | 400篇 |
1997年 | 453篇 |
1996年 | 432篇 |
1995年 | 399篇 |
1994年 | 415篇 |
1993年 | 367篇 |
1992年 | 337篇 |
1991年 | 330篇 |
1990年 | 291篇 |
1989年 | 289篇 |
1988年 | 275篇 |
1987年 | 235篇 |
1986年 | 250篇 |
1985年 | 367篇 |
1984年 | 378篇 |
1983年 | 325篇 |
1982年 | 363篇 |
1981年 | 330篇 |
1980年 | 353篇 |
1979年 | 282篇 |
1978年 | 310篇 |
1977年 | 295篇 |
1976年 | 236篇 |
1975年 | 200篇 |
1974年 | 210篇 |
1973年 | 176篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
12.
13.
Peter Imkeller 《Probability Theory and Related Fields》1996,106(1):105-135
Summary. The analytic treatment of problems related to the asymptotic behaviour of random dynamical systems generated by stochastic
differential equations suffers from the presence of non-adapted random invariant measures. Semimartingale theory becomes accessible
if the underlying Wiener filtration is enlarged by the information carried by the orthogonal projectors on the Oseledets spaces
of the (linearized) system.
We study the corresponding problem of preservation of the semimartingale property and the validity of a priori inequalities
between the norms of stochastic integrals in the enlarged filtration and norms of their quadratic variations in case the random
element F enlarging the filtration is real valued and possesses an absolutely continuous law. Applying the tools of Malliavin’s calculus,
we give smoothness conditions on F under which the semimartingale property is preserved and a priori martingale inequalities are valid.
Received: 12 April 1995 / In revised form: 7 March 1996 相似文献
14.
15.
Stefan Peterli Dieter Hubmann Urs Squin Helmut Mett Peter Traxler 《Helvetica chimica acta》1994,77(1):59-69
β-Nitrostyrene derivatives of adenosine 5′-glutarates are potent and selective bisubstrate-type inhibitors of the epidermal growth factor receptor protein tyrosine kinase (EGF-R PTK). In an attempt to improve the inhibitory activity, this type of compounds was modified with alkyl spacers of varying length between the nitrostyrene and the glutaryl units. The spacers consisted of 1, 3, 4, and 5 atoms to give compounds of the benzyl, oxyethyl, oxypropyl, and oxybutyl series, respectively (Schemes 1 and 2). Adenosine 5′-esters were prepared in the benzyl and oxypropyl series only. Compared to the compounds in the parent series without spacer (IC50 = 0.7–12 μM ), most of the modified compounds inhibited the EGF-R PTK only marginally or were inactive (IC50 ≥ 100 μM ). The only exceptions were the free acids 19 and 20 with IC50 values of ca. 5 μM . It is noteworthy that esterification of these two hydrogen glutarates with either MeOH or adenosine yielded inactive compounds, which is in contrast to the corresponding substances without spacers. 相似文献
16.
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
17.
Helmut Schmidhammer Eva Scherb-Bukowiecki Thomas A. Mayer Peter Schnholzer 《Helvetica chimica acta》1994,77(6):1590-1594
The synthesis of benzazepine analogues of the opium alkaloid noscapine ( 1 ) is described. The benzazepines 2 and 3 were prepared starting from nornarceine ethyl ester ( 4 ; readily available from 1 ) in several steps. X-Ray analysis of compound 2 revealed that it is not a diastereosisomer mixture but a racemate of the threo-form and thus has the same configuration as 1 . 相似文献
18.
19.
Peter Dräxler 《Journal of Pure and Applied Algebra》2002,169(1):33-42
We show that the cleaving functors introduced in [Bautista et al., Invent. Math. 81 (1985) 217] as a tool for proving infinite representation type of finite-dimensional algebras can also be used to establish controlled wildness. The main application is that an algebra is controlled wild if there is an indecomposable projective module with a Loewy factor having a homogeneous direct summand which is of length at least 3. As a second application we derive Han's covering criterion. 相似文献
20.