全文获取类型
收费全文 | 26813篇 |
免费 | 62篇 |
国内免费 | 137篇 |
专业分类
系统科学 | 147篇 |
丛书文集 | 195篇 |
教育与普及 | 63篇 |
理论与方法论 | 72篇 |
现状及发展 | 11970篇 |
研究方法 | 1179篇 |
综合类 | 13064篇 |
自然研究 | 322篇 |
出版年
2013年 | 177篇 |
2012年 | 409篇 |
2011年 | 687篇 |
2008年 | 480篇 |
2007年 | 554篇 |
2006年 | 563篇 |
2005年 | 528篇 |
2004年 | 470篇 |
2003年 | 491篇 |
2002年 | 487篇 |
2001年 | 928篇 |
2000年 | 896篇 |
1999年 | 569篇 |
1994年 | 350篇 |
1992年 | 539篇 |
1991年 | 409篇 |
1990年 | 476篇 |
1989年 | 417篇 |
1988年 | 401篇 |
1987年 | 455篇 |
1986年 | 452篇 |
1985年 | 558篇 |
1984年 | 449篇 |
1983年 | 385篇 |
1982年 | 370篇 |
1981年 | 357篇 |
1980年 | 354篇 |
1979年 | 895篇 |
1978年 | 687篇 |
1977年 | 593篇 |
1976年 | 578篇 |
1975年 | 571篇 |
1974年 | 649篇 |
1973年 | 570篇 |
1972年 | 555篇 |
1971年 | 676篇 |
1970年 | 866篇 |
1969年 | 643篇 |
1968年 | 696篇 |
1967年 | 657篇 |
1966年 | 600篇 |
1965年 | 421篇 |
1964年 | 175篇 |
1959年 | 226篇 |
1958年 | 373篇 |
1957年 | 247篇 |
1956年 | 229篇 |
1955年 | 213篇 |
1954年 | 202篇 |
1948年 | 173篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Zusammenfassung Vorbehandlung mit 10 mg/kg Chlorpromazin (CPZ) i.p. bewirkt bei Ratten, denen14C-Tyrosin injiziert wurde, eine Zunahme der spezifischen Radioaktivität von14C-Dopamin im Gehirn. CPZ beschleunigt bei Tieren, deren zerebrale Katecholamine durchl-214C-Dopa markiert wurden, den Abfall der spezifischen Radioaktivität von Dopamin und Noradrenalin. Daraus wird geschlossen, dass CPZ den Umsatz zerebraler Katecholamine erhöht. 相似文献
972.
973.
974.
975.
976.
Summary A comparison of the frequencies of chromosomal aberrations and the rates of SV40 transformation was made using fibroblasts obtained from 2 patients with Bloom's syndrome (BS) and from a normal individual. BS cells were found to be more susceptible to chromosome damage, in confirmation of earlier reports, but surprisingly, BS cells were distinctly less prone to transformation.Supported in part by the Michael J. Connell Foundation Medical Genetics Fund, and Health, Education and Welfare, MCH project 422. 相似文献
977.
The in situ activity of 3 beta-hydroxysteroid dehydrogenase was detected in clustered cells which showed steroid-producing morphology, within the capsule of the paraaortic lymph node. In light and electron microscopic studies, the positive reaction products were detected on intracapsular cell clusters. This result indicates that these unique cells may have a steroid secreting function within the lymph nodes. 相似文献
978.
This article studies Man and Tiao's (2006) low‐order autoregressive fractionally integrated moving‐average (ARFIMA) approximation to Tsai and Chan's (2005b) limiting aggregate structure of the long‐memory process. In matching the autocorrelations, we demonstrate that the approximation works well, especially for larger d values. In computing autocorrelations over long lags for larger d value, using the exact formula one might encounter numerical problems. The use of the ARFIMA(0, d, d?1) model provides a useful alternative to compute the autocorrelations as a really close approximation. In forecasting future aggregates, we demonstrate the close performance of using the ARFIMA(0, d, d?1) model and the exact aggregate structure. In practice, this provides a justification for the use of a low‐order ARFIMA model in predicting future aggregates of long‐memory process. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
979.
This study examined the individual and simultaneous adsorption of SOx(SO2)and NOx(NO-NO2)on activated carbon prepared from waste palm shell.The adsorption process was examined in a fixed bed reactor at low temperatures(100 300°C).For individual adsorption without any catalytic activation,SOx showed good adsorption whereas NOx was very much poor.In the simultaneous adsorption of SOx and NOx,SOx showed greater adsorption affinity than NOx.For palm shell activated carbon(PSAC)impregnated with metal catalyst(Ni and Ce)the concentration adsorbed profile showed that the amount of SOx adsorbed decreased regularly,while the amount of the adsorbed NOx increased irregularly.The properties of the pure and impregnated PSAC were analyzed by BET,SEM and EDX.These investigations indicated that PSAC impregnated with metal catalyst is the determining factor in the adsorption of SOx and NOx simultaneously. 相似文献
980.
K. Ikemoto T. Utsunomiya M. A. Ball M. Kobayashi R. B. Pollard F. Suzuki Ph.D. 《Cellular and molecular life sciences : CMLS》1994,50(5):456-460
The antiviral activity of Shigyaku-to (TJS-109), a traditional Chinese herbal medicine, was investigated in mice infected with herpes simplex virus type 1 (HSV-1). TJS-109 is a combination of the medicinal plant extracts fromZingiberis siccatum rhizoma,Aconiti tuber andGlycyrrhizae radix in a specific proportion. Mice infected with a 10 LD50 dose of HSV-1 were treated with TJS-109 orally at doses of 1.25 to 20 mg/kg 2 days before, and 1 and 4 days after the infection. The treated groups had 80% (1.25 mg/kg), 40% (5 mg/kg) and 23% (20 mg/kg) mortality rates 25 days after the infection as compared with a 100% mortality rate in control mice treated with saline. When HSV-1 infected mice (recipients) received CD8+T cell fractions derived from spleens of mice treated with TJS-109 (donors), 70% of recipients survived, as compared with 0% survivors in the groups of mice treated with saline, B cell fractions, CD4+ T cell fractions or macrophage-enriched fractions prepared from the same donors. TJS-109 did not show any virucidal activities against HSV-1 or any virostatic activities on the growth of HSV-1 in Vero cells. These results suggest that TJS-109 protected mice exposed to lethal amounts of HSV-1 through the activation of CD8+ T cells. 相似文献