全文获取类型
收费全文 | 25713篇 |
免费 | 1114篇 |
国内免费 | 3篇 |
专业分类
26830篇 |
出版年
2023年 | 198篇 |
2021年 | 259篇 |
2020年 | 181篇 |
2019年 | 191篇 |
2018年 | 246篇 |
2017年 | 237篇 |
2016年 | 333篇 |
2015年 | 541篇 |
2014年 | 624篇 |
2013年 | 1258篇 |
2012年 | 932篇 |
2011年 | 927篇 |
2010年 | 643篇 |
2009年 | 720篇 |
2008年 | 755篇 |
2007年 | 756篇 |
2006年 | 600篇 |
2005年 | 579篇 |
2004年 | 576篇 |
2003年 | 490篇 |
2002年 | 499篇 |
2001年 | 218篇 |
1999年 | 216篇 |
1998年 | 187篇 |
1996年 | 206篇 |
1995年 | 202篇 |
1993年 | 276篇 |
1992年 | 287篇 |
1991年 | 281篇 |
1990年 | 276篇 |
1989年 | 446篇 |
1988年 | 388篇 |
1987年 | 496篇 |
1986年 | 434篇 |
1985年 | 448篇 |
1984年 | 382篇 |
1983年 | 302篇 |
1982年 | 336篇 |
1981年 | 358篇 |
1980年 | 345篇 |
1979年 | 343篇 |
1978年 | 396篇 |
1977年 | 443篇 |
1976年 | 457篇 |
1975年 | 471篇 |
1974年 | 335篇 |
1973年 | 191篇 |
1972年 | 204篇 |
1971年 | 191篇 |
1970年 | 185篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
We have compared the species richness of medicinal plants and the differential patterns of use amongst settlements in the
Andean communities of Northwest Argentina which have differing levels of isolation. About 259 ethnoespecies, belonging to
74 plant families, were included, representing between 70 and 80% of the total estimate. The results indicate that Coronopus didymus is the most relevant and important species. The method of use of medicinal plants and the ailments treated by rural doctors compared to those of the layperson is different. Native and exotic plants are used differently according to the body system
treated. There are some relationships between internal and external use and body systems and recipes. The greater medicinal
species richness found in the less isolated locations is due to external enriching cultural influences. 相似文献
12.
13.
Oliver Goldschmidt Jonathan F. Bard Alexan Takvorian 《Flexible Services and Manufacturing Journal》1997,9(3):251-272
Mixed-model assembly lines are becoming increasingly interesting as the use of just-in-time principles in manufacturing continues to expand. This paper presents, for the first time, complexity results for the underlying problem of product sequencing. It is shown that the problem is intractable for both the single station and the multiple station case. Nevertheless, efficient 1.5-approximation algorithms are developed for the early- and late-start models associated with the former case. Empirical results demonstrate that these algorithms perform extremely well in practice. 相似文献
14.
15.
16.
By means of radioimmunoassay a clear-cut peak of melatonin concentration was found in the pineal organ of the pigeon at the middle of the scotophase (Coisin et al. 1982a). The aim of the present study was to identify the cell type responsible for the nocturnal indole metabolism, including melatonin synthesis, in the pineal of this avian species. After a short-term incubation or organ culture in the presence of [3H]-indolic precursors, [3H]-5-hydroxytryptophan or [3H]-5-hydroxytryptamine, the relative amounts of deaminated and acetylated products occurring in the pineal organ were measured by the use of thin layer chromatography and liquid-scintillation counting. It was possible to modify the relative amounts of deaminated and acetylated indoles by the application of some inhibitors of monoamine oxidase and cyclic nucleotide phosphodiesterase. Irrespective of the experimental conditions, high-resolution autoradiography combined with the above-mentioned radiochemical experiments showed that the cells of the receptor line (modified photoreceptor cells) are responsible for indole storage and metabolism, and very probably also for melatonin biosynthesis. The other cell types of the pineal parenchyma did not display significant labeling. 相似文献
17.
18.
A case of chromomycosis in which hyperthermia proved effective is reported. The patient was a 56-year-old male bean curd maker who, without any previous history of minor trauma, developed on the extensor side of the left upper arm an eczematous lesion that underwent gradual radial expansion. The lesion showed a well-defined, 7×10 cm infiltrated erythematous plaque with the central area healed and, at the upper and lower borders, adherent scales and crusts on the surface. Histological examination revealed granulomatous changes in the dermis, as well as sclerotic cells within giant cells and microabscesses. On culturing,Fonsecaea pedrosoi was isolated. The patient was treated with disposable chemical pocket warmers, which were secured over the lesion with a rather tight elastic bandage, so that they kept the affected area warm for 24 hours a day. After a month of such hyperthermic treatment, the erythema and infiltration had decreased considerably, and microscopic examination and culture of the crusts both yielded negative results. Examination of biopsy specimens of the lesion after the third month showed that it had cicatrized. The treatment was stopped after 4 months, and no relapse occurred. We also summarize the published results of local hyperthermic treatment of chromomycosis in Japan. 相似文献
19.
20.