全文获取类型
收费全文 | 475篇 |
免费 | 50篇 |
国内免费 | 54篇 |
出版年
2023年 | 11篇 |
2022年 | 15篇 |
2021年 | 13篇 |
2020年 | 12篇 |
2019年 | 14篇 |
2018年 | 13篇 |
2017年 | 24篇 |
2016年 | 10篇 |
2015年 | 29篇 |
2014年 | 29篇 |
2013年 | 32篇 |
2012年 | 32篇 |
2011年 | 22篇 |
2010年 | 23篇 |
2009年 | 33篇 |
2008年 | 27篇 |
2007年 | 37篇 |
2006年 | 22篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 24篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 10篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有579条查询结果,搜索用时 234 毫秒
1.
The trend of increasing height can be interpreted as a reflection of the unfolding progress of civilization. Height changes among children and adolescents are good markers of this trend. We analyze the secular trend in the heights of children and adolescents in the Czech Republic on the basis of data from anthropological surveys. The earliest height data pertain to Czech youths who attended the Military Schools in Austria in 1800-1809. Data also exist for 1895 and continue in 1951 and at 10-year intervals thereafter. Growth curves were obtained for separate age groups by fitting mean values via third-order polynomial smoothing splines. Between 1951 and 2001, the mean heights of boys and girls aged 2.5 years increased by 2.7 and 3 cm, respectively. Since 1895, the mean height of 13-year-old boys has increased by 19.4 cm, and the mean height of girls has increased by 18.3 cm. 相似文献
2.
Selective analysis of antitumor drug interaction with living cancer cells as probed by surface-enhanced Raman spectroscopy 总被引:1,自引:0,他引:1
A new technique for the selective measurement of small amounts of antitumor drugs in the nucleus and cytoplasm of a living cancer cell, based on surface-enhanced Raman spectroscopy (SERS), is proposed. The ability to detect SERS signals from very dilute (up to 10–10
M) solutions of doxorubicin or adriamycin (DOX), and 4O-tetrahydropyranyl-adriamycin (THP-ADM), as well as from their complexes with targets in vitro and in vivo, has been demonstrated. SERS spectra were obtained from a population as well as from single living erythroleukaemic K562 cells treated with DOX. The results of the measurements on the population of cells containing DOX in nuclei or in the cytoplasm are well correlated with the microscopic SERS measurements on the single cells treated with DOX, obtained by selectively recording signals from the living cell nucleus or from the cytoplasm. Possibilities for the application of this new technique in different aspects of cancer research are discussed.Abbreviations DNA
deoxyribonucleic acid
- DOX
doxorubicin
- SERS
surface-enhanced Raman spectroscopy
- THP-ADM
4O-tetrahydropyranyl adriamycin
- PBS
phosphate buffered saline
Offprint requests to: M. Manfait 相似文献
3.
Hans Fricke Karen Hissmann Jürgen Schauer Olaf Reinicke Lutz Kasang Raphael Plante 《Environmental Biology of Fishes》1991,32(1-4):287-300
Synopsis In 1987 and 1989 coelacanths were observed for the first time in their natural habitat with the help of submersibles. Coelacanths were found between 150–253 m depth, their preferential depth seems to be around 200 m; the water temperature ranged between 16.5–22.8° C. During the day coelacanths aggregate in small non-aggressive groups in sheltered lava-caves. Caves might be a limiting factor for distribution. At night they leave the caves for hunting by drifting singly along the steep lava slopes. They migrate between different caves located within a large home range covering more than 8 km coastline. Coelacanths are site-attached, some for a period of at least 2 years. Our own observations and earlier catch records show that only the west coast of Grand Comoro is a suitable coelacanth habitat with more structural complexity and prey fish abundance than other coastlines of the island. From our survey we estimated a total coelacanth population off Grand Comoro to be 150–210 individuals; a saturated population would be 370–510 individuals. This small relict population seems to be stable. International protection of coelacanths against commercial interests is needed 相似文献
4.
“引黄济青”输水沿线水生生物分布与蓄水库富营养化关系的研究 总被引:3,自引:0,他引:3
“引黄济青”是国家“七五”重点工程,由黄河下游博兴县境内打渔张闸引水,在渠首沉沙后,再经惠民、东营、潍坊和青岛的10个县区约253km的明渠输送,到达唠山县棘洪滩蓄水库蓄存,实现向青岛市日供水3.0×10~5m~3。明渠输水过程中,来白沿线的营养物质会污染水体,加之输水在库中滞留时间长,会不会发生富营养化,这是社会普遍关注的问题。 相似文献
5.
6.
我们检测10例普通猪的胄组织,有8例分离到螺杆菌样细菌(HLO)。其菌落、菌体形态和某些生化反应与幽门螺杆菌(HP)相似,但其尿素酶活性较低,HLO全菌蛋白的SDS一pAGE图谱也与HP的不同。本文就HP和HLO及其伴发的人、猪慢性胃炎的特点,作了比较和讨论。 相似文献
7.
Organisms modify their development and function in response to the environment. At the same time, the environment is modified by the activities of the organism. Despite the ubiquity of such dynamical interactions in nature, it remains challenging to develop models that accurately represent them, and that can be fitted using data. These features are desirable when modeling phenomena such as phenotypic plasticity, to generate quantitative predictions of how the system will respond to environmental signals of different magnitude or at different times, for example, during ontogeny. Here, we explain a modeling framework that represents the organism and environment as a single coupled dynamical system in terms of inputs and outputs. Inputs are external signals, and outputs are measurements of the system in time. The framework uses time-series data of inputs and outputs to fit a nonlinear black-box model that allows to predict how the system will respond to novel input signals. The framework has three key properties: it captures the dynamical nature of the organism–environment system, it can be fitted with data, and it can be applied without detailed knowledge of the system. We study phenotypic plasticity using in silico experiments and demonstrate that the framework predicts the response to novel environmental signals. The framework allows us to model plasticity as a dynamical property that changes in time during ontogeny, reflecting the well-known fact that organisms are more or less plastic at different developmental stages. 相似文献
8.
Mary Beverley-Burton 《Environmental Biology of Fishes》1978,3(4):369-377
Synopsis The extent to which data concerning the population genetics of a parasite — namely larvalAnisakis simplex, may be used as an auxilliary source of information on various aspects of the marine migrations of Atlantic salmon (Salmo salar) is examined.Frequencies of the various acid phosphatase alleles could not be used in distinguishing between or estimating the proportions of North American and European salmon occurring off west Greenland. The genetic structure of larvae from salmon taken in Scotland was different from that taken in Ireland and England confirming an earlier conclusion that the feeding habits of the fish from Scotland were significantly different. In the western Atlantic, salmon from northern Newfoundland and also salmon from the Bay of Fundy had apparently ingested different populations (or different proportions of the same nematode population) than salmon from Miramachi and Chaleur Bay areas. Samples from northern Newfoundland and Labrador were also genetically different. These findings are discussed in relation to the available literature concerning salmon migrations, explanations are put forward and areas of future research suggested. 相似文献
9.
Ten strains of fungi were tested for tolerance to the fungicide benomyl. Verticillium chlamydosporium strain 2 did not grow in the presence of benomyl; Drechraeria coniospora strains 1 and 2 and Chaetomium sp. tolerated only 0.1 μg benomyl/ml medium; Acremonium bacillisporum, an unidentified fungus, and Phoma chrysanthemicola uniformly grew at 1 μg/ml, but some hyphae grew at higher benomyl concentrations; Fusarium sp. tolerated 475 μg/ml, but some hyphae grew on medium amended with 1,000 μg/ml; Verticillium lecanii and V. chlamydosporium strain 1 routinely tolerated 1,000 μg/ml. Fungi generally grew more slowly at higher than at lower benomyl concentrations. Strains with elevated tolerance to benomyl were selected from Acremonium bacillisporum, Drechmeria coniospora, Fusarium sp., and an unidentified fungus. These strains retained the increased tolerance after repeated transfers on unamended medium. 相似文献
10.