全文获取类型
收费全文 | 4904篇 |
免费 | 81篇 |
国内免费 | 12篇 |
专业分类
化学 | 2464篇 |
晶体学 | 131篇 |
力学 | 225篇 |
数学 | 667篇 |
物理学 | 1510篇 |
出版年
2022年 | 65篇 |
2021年 | 72篇 |
2020年 | 77篇 |
2019年 | 88篇 |
2018年 | 64篇 |
2017年 | 83篇 |
2016年 | 125篇 |
2015年 | 102篇 |
2014年 | 126篇 |
2013年 | 344篇 |
2012年 | 235篇 |
2011年 | 260篇 |
2010年 | 166篇 |
2009年 | 155篇 |
2008年 | 197篇 |
2007年 | 214篇 |
2006年 | 164篇 |
2005年 | 170篇 |
2004年 | 135篇 |
2003年 | 94篇 |
2002年 | 90篇 |
2001年 | 64篇 |
2000年 | 52篇 |
1999年 | 53篇 |
1998年 | 50篇 |
1996年 | 53篇 |
1995年 | 48篇 |
1994年 | 56篇 |
1993年 | 71篇 |
1992年 | 63篇 |
1991年 | 48篇 |
1990年 | 58篇 |
1989年 | 52篇 |
1988年 | 62篇 |
1987年 | 51篇 |
1986年 | 30篇 |
1985年 | 73篇 |
1984年 | 95篇 |
1983年 | 57篇 |
1982年 | 63篇 |
1981年 | 70篇 |
1980年 | 71篇 |
1979年 | 72篇 |
1978年 | 68篇 |
1977年 | 62篇 |
1976年 | 57篇 |
1975年 | 44篇 |
1974年 | 47篇 |
1973年 | 55篇 |
1972年 | 34篇 |
排序方式: 共有4997条查询结果,搜索用时 15 毫秒
41.
Sen Gupta JG 《Talanta》1985,32(1):1-6
An improved graphite furnace atomic-absorption method has been developed for the determination of Sc, Y and the rare-earth elements in silicate rocks and related materials. The method, which involves the separation of the lanthanides by ion-exchange followed by their determination by electrothermal atomization, with use of an automatic sampling device, is more rapid than a previous method based on separation by co-precipitation with calcium oxalate and hydrous ferric oxide followed by normal injection of the solution into the furnace. Greater sensitivity (~ 10-40-fold) for La, Ce, Pr, Gd, Tb and Lu is also achieved by using a tantalum foil-lined graphite furnace instead of a pyrolytically-coated furnace. Results obtained for five international reference rock samples, NIM-G, SCo-1, MAG-1, SDC-1 and BHVO-1, are compared with those obtained previously by the oxalate-hydrous oxide co-precipitation method and with other published values. Results are given for four new Canadian iron-formation reference materials, FeR-1 to FeR-4. 相似文献
42.
Algebras and Representation Theory - We introduce the concept of a prime band in a string algebra Λ and use it to associate to Λ its finite bridge quiver. Then we introduce a new... 相似文献
43.
44.
45.
T. T. Nguyen A. K. Gupta Y. Wang 《Annals of the Institute of Statistical Mathematics》1996,48(3):573-576
For independent random variables X and Y, define % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiGc9yrFr0xXdbba91rFfpec8Eeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqGaaO% qaaiaabofaruWrL9MCNLwyaGqbciaa-bcacqGHHjIUcaWFGaGaa8hw% aiaa-TcacaWFzbaaaa!4551!\[{\rm{S}} \equiv X + Y\]. When the conditional expectations % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiGc9yrFr0xXdbba91rFfpec8Eeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqGaaO% qaaiaadweacaGGBbqefCuzVj3zPfgaiuGajaaqcaWFNbGccaGGOaGa% amiwaiaacMcacaGG8bGaam4uaiaac2facqGHHjIUcaWGHbGaaiikai% aadofacaGGPaaaaa!4BC4!\[E[g(X)|S] \equiv a(S)\]and % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiGc9yrFr0xXdbba91rFfpec8Eeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqGaaO% qaaiaadweacaGGBbGaamiAaiaacIcacaWGybGaaiykaiaacYhacaWG% tbGaaiyxaiabggMi6kaadkgacaGGOaGaam4uaiaacMcaaaa!4894!\[E[h(X)|S] \equiv b(S)\]are given, then under certain assumptions, the density function of X has the form of u(x)k()eax, where u(x) is uniquely determined by the functions a(·) and b(·). 相似文献
46.
47.
48.
49.
50.
In this paper estimation of the probabilities of a multinomial distribution has been studied. The five estimators considered are: unrestricted estimator (UE), restricted estimator (RE) (under model ), preliminary test estimator (PTE) based on a test of the model , shrinkage estimator (SE) and the positive-rule shrinkage estimator (PRSE). Asymptotic distributions of these estimators are given under Pitman alternatives and the asymptotic risk under a quadratic loss has been evaluated. The relative performance of the five estimators is then studied with respect to their asymptotic distributional risks (ADR). It is seen that neither of the preliminary test and shrinkage estimators dominates the other, though each fares well relative to the other estimators. However, the positive rule estimator is recommended for use for dimension 3 or more while the PTE is recommended for dimension less than 3. 相似文献