全文获取类型
收费全文 | 3661篇 |
免费 | 342篇 |
国内免费 | 12篇 |
专业分类
4015篇 |
出版年
2022年 | 30篇 |
2021年 | 59篇 |
2020年 | 40篇 |
2019年 | 45篇 |
2018年 | 83篇 |
2017年 | 71篇 |
2016年 | 87篇 |
2015年 | 150篇 |
2014年 | 154篇 |
2013年 | 209篇 |
2012年 | 222篇 |
2011年 | 203篇 |
2010年 | 156篇 |
2009年 | 117篇 |
2008年 | 163篇 |
2007年 | 158篇 |
2006年 | 160篇 |
2005年 | 137篇 |
2004年 | 166篇 |
2003年 | 106篇 |
2002年 | 125篇 |
2001年 | 112篇 |
2000年 | 116篇 |
1999年 | 87篇 |
1998年 | 35篇 |
1997年 | 27篇 |
1996年 | 23篇 |
1995年 | 28篇 |
1994年 | 33篇 |
1993年 | 27篇 |
1992年 | 57篇 |
1991年 | 54篇 |
1990年 | 52篇 |
1989年 | 43篇 |
1988年 | 40篇 |
1987年 | 33篇 |
1986年 | 47篇 |
1985年 | 37篇 |
1984年 | 41篇 |
1983年 | 29篇 |
1979年 | 26篇 |
1978年 | 20篇 |
1977年 | 26篇 |
1976年 | 20篇 |
1972年 | 24篇 |
1970年 | 30篇 |
1969年 | 31篇 |
1968年 | 28篇 |
1967年 | 22篇 |
1965年 | 22篇 |
排序方式: 共有4015条查询结果,搜索用时 7 毫秒
931.
S B Rosas A Calzolari J L La Torre N E Ghittoni C Vsquez 《Journal of bacteriology》1983,155(1):402-406
A plasmid-containing wild-type Escherichia coli strain was treated with two plasmid-curing agents, sodium dodecyl sulfate and ethidium bromide. Plasmid elimination was accompanied by drastic changes in the morphology of the colonies. Analysis of the cured strain by scanning and transmission electron microscopy showed important alterations in size and morphology of the cells. Metabolic differences were also found between the wild-type and cured cells. 相似文献
932.
933.
Stphane La Barre Stphane Singer Evelyne Erard-Le Denn Marcel Jozefowicz 《Journal of biotechnology》1999,70(1-3):207-212
We describe a protocol for preparing cultures of the PSP (paralytic shellfish poisoning) dinoflagellate Alexandrium minutum, towards subsequent studies of cell adhesion onto artificial substrates. First, phenotypic uniformity of the strain used and reproducibility of the standard growth profile are obtained by optimising key parameters. Batches of A. minutum at mid-exponential proliferation phase are radiolabeled with 33P-containing medium in order to later quantify cell adhesion. A mortality corrective index is applied to the latter, using the vital fluorochrome acridine orange, i.e. dead cells show no nuclear incorporation under epifluorescence microscopy. 相似文献
934.
935.
L. Mancuso M. I. Liuzzo S. Fadda M. Pisu A. Cincotti M. Arras G. La Nasa A. Concas G. Cao 《Cell proliferation》2010,43(3):310-320
This study focuses on analysis of in vitro cultures of chondrocytes from ovine articular cartilage. Isolated cells were seeded in Petri dishes, then expanded to confluence and phenotypically characterized by flow cytometry. The sigmoidal temporal profile of total counts was obtained by classic haemocytometry and corresponding cell size distributions were measured electronically using a Coulter Counter. A mathematical model recently proposed ( 1 ) was adopted for quantitative interpretation of these experimental data. The model is based on a 1‐D (that is, mass‐structured), single‐staged population balance approach capable of taking into account contact inhibition at confluence. The model’s parameters were determined by fitting measured total cell counts and size distributions. Model reliability was verified by predicting cell proliferation counts and corresponding size distributions at culture times longer than those used when tuning the model’s parameters. It was found that adoption of cell mass as the intrinsic characteristic of a growing chondrocyte population enables sigmoidal temporal profiles of total counts in the Petri dish, as well as cell size distributions at ‘balanced growth’, to be adequately predicted. 相似文献
936.
937.
Abstract We study the properties of ring polymers in disordered systems using a Monte Carlo algorithm. The algorithm is used to generate a ring on a two dimensional lattice, and the disorder is represented by the random dilution of the lattice. We show how the ring undergoes a cross-over from obeying self avoiding statistics at low concentrations of disorder, to behaving like a branched polymer as the concentration of disorder is increased. We find a scaling behavior to characterize this cross-over phenomenon. We further show how this scaling behavior is also present in another class of problems, namely two dimensional vesicles subjected to a pressure differential. 相似文献
938.
Motor proteins display widely different stepping patterns as they move on microtubule tracks, from the deterministic linear or helical motion performed by the protein kinesin to the uncoordinated random steps made by dynein. How these different strategies produce an efficient navigation system needed to ensure correct cellular functioning is still unclear. Here, we show by numerical simulations that deterministic and random motor steps yield different outcomes when random obstacles decorate the microtubule tracks: kinesin moves faster on clean tracks but its motion is strongly hindered on decorated tracks, while dynein is slower on clean tracks but more efficient in avoiding obstacles. Further simulations indicate that dynein’s advantage on decorated tracks is due to its ability to step backwards. Our results explain how different navigation strategies are employed by the cell to optimize motor driven cargo transport. 相似文献
939.
Fernando M. Carvajal-Vallejos Rémy Bigorne América J. Zeballos Fernández Jaime Sarmiento Soraya Barrera Takayuki Yunoki Marc Pouilly José Zubieta Evans De La Barra Michel Jegú Mabel Maldonado Paul Van Damme Ricardo Céspedes Thierry Oberdorff 《Hydrobiologia》2014,732(1):19-27
The Bolivian part of the Amazon Basin contains a mega diverse and well-preserved fish fauna. Since the last decade, this fish fauna has received an increasing attention from scientists and the national authorities as fishes represent one of the most important sources of proteins for local human communities. However, this fish fauna still remains poorly documented. Here, we present a database for fishes from the Bolivian Amazon. To build the database, we conducted an extensive literature survey of native and non-native (exotic) fishes inhabiting all major sub-drainages of the Bolivian Amazon. The database, named Fish-AMAZBOL, contains species lists for 13 Amazonian hydrological units, covering 100% of the Bolivian Amazon and approximately 65% (722,137 km2) of the all territory. Fish-AMAZBOL includes 802 valid species, 12 of them being non-native, that have been checked for systematic reliability and consistency. To put this number in perspective, this represents around 14% of the all Neotropical ichthyofauna and around 6% of all strictly freshwater fishes inhabiting the planet. This database is currently the most comprehensive database of native and non-native fish species richness available so far for the Bolivian Amazon. 相似文献
940.
Jong-Yun Choi Seong-Ki Kim Kwang-Hyeon Chang Myoung-Chul Kim Geung-Hwan La Gea-Jae Joo Kwang-Seuk Jeong 《PloS one》2014,9(4)
In this study, we examined the effects of two phytoplankton species, Chlorella vulgaris and Stephanodiscus hantzschii, on growth of the zooplankton Daphnia magna. Our experimental approach utilized stable isotopes to determine the contribution of food algae to offspring characteristics and to the size of adult D. magna individuals. When equal amounts of food algae were provided (in terms of carbon content), the size of individuals, adult zooplankton, and their offspring increased significantly following the provision of S. hantzschii, but not after the provision of C. vulgaris or of a combination of the two species. Offspring size was unaffected when C. vulgaris or a mixture of the two algal species was delivered, whereas providing only S. hantzschii increased the production of larger-sized offspring. Stable isotope analysis revealed significant assimilation of diatom-derived materials that was important for the growth of D. magna populations. Our results confirm the applicability of stable isotope approaches for clarifying the contribution of different food algae and elucidate the importance of food quality for growth of D. magna individuals and populations. Furthermore, we expect that stable isotope analysis will help to further precisely examine the contribution of prey to predators or grazers in controlled experiments. 相似文献