全文获取类型
收费全文 | 2457篇 |
免费 | 189篇 |
专业分类
2646篇 |
出版年
2023年 | 11篇 |
2022年 | 39篇 |
2021年 | 76篇 |
2020年 | 37篇 |
2019年 | 51篇 |
2018年 | 54篇 |
2017年 | 47篇 |
2016年 | 63篇 |
2015年 | 121篇 |
2014年 | 147篇 |
2013年 | 181篇 |
2012年 | 218篇 |
2011年 | 250篇 |
2010年 | 146篇 |
2009年 | 130篇 |
2008年 | 124篇 |
2007年 | 135篇 |
2006年 | 90篇 |
2005年 | 104篇 |
2004年 | 106篇 |
2003年 | 81篇 |
2002年 | 82篇 |
2001年 | 17篇 |
2000年 | 11篇 |
1999年 | 21篇 |
1998年 | 28篇 |
1997年 | 10篇 |
1996年 | 12篇 |
1995年 | 22篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1975年 | 7篇 |
1974年 | 8篇 |
1973年 | 5篇 |
1971年 | 6篇 |
1970年 | 7篇 |
1938年 | 4篇 |
排序方式: 共有2646条查询结果,搜索用时 15 毫秒
1.
2.
Sam Mavandadi Steve Feng Frank Yu Stoyan Dimitrov Karin Nielsen-Saines William R. Prescott Aydogan Ozcan 《PloS one》2012,7(10)
We propose a methodology for digitally fusing diagnostic decisions made by multiple medical experts in order to improve accuracy of diagnosis. Toward this goal, we report an experimental study involving nine experts, where each one was given more than 8,000 digital microscopic images of individual human red blood cells and asked to identify malaria infected cells. The results of this experiment reveal that even highly trained medical experts are not always self-consistent in their diagnostic decisions and that there exists a fair level of disagreement among experts, even for binary decisions (i.e., infected vs. uninfected). To tackle this general medical diagnosis problem, we propose a probabilistic algorithm to fuse the decisions made by trained medical experts to robustly achieve higher levels of accuracy when compared to individual experts making such decisions. By modelling the decisions of experts as a three component mixture model and solving for the underlying parameters using the Expectation Maximisation algorithm, we demonstrate the efficacy of our approach which significantly improves the overall diagnostic accuracy of malaria infected cells. Additionally, we present a mathematical framework for performing ‘slide-level’ diagnosis by using individual ‘cell-level’ diagnosis data, shedding more light on the statistical rules that should govern the routine practice in examination of e.g., thin blood smear samples. This framework could be generalized for various other tele-pathology needs, and can be used by trained experts within an efficient tele-medicine platform. 相似文献
3.
Summary . We propose a fully inferential model-based approach to the problem of comparing the firing patterns of a neuron recorded under two distinct experimental conditions. The methodology is based on nonhomogeneous Poisson process models for the firing times of each condition with flexible nonparametric mixture prior models for the corresponding intensity functions. We demonstrate posterior inferences from a global analysis, which may be used to compare the two conditions over the entire experimental time window, as well as from a pointwise analysis at selected time points to detect local deviations of firing patterns from one condition to another. We apply our method on two neurons recorded from the primary motor cortex area of a monkey's brain while performing a sequence of reaching tasks. 相似文献
4.
5.
Resistance of Pseudomonas to Quaternary Ammonium Compounds: II. Cross-Resistance Characteristics of a Mutant of Pseudomonas aeruginosa 总被引:3,自引:0,他引:3 下载免费PDF全文
Tube dilution experiments showed that benzalkonium chloride (BC)-resistant mutants of Pseudomonas aeruginosa grown in the presence of 1,000 mug of BC per ml were at least 20 times more sensitive to polymyxin B and colistin sulfate than the BC-sensitive (BCS) parent strain. BCS cells selected for resistance to 500 mug of polymyxin B per ml remained sensitive to BC. There was little difference in the amount of carbenicillin, gentamicin sulfate, or rifampin needed to prevent growth of either the BCS or BC-resistant (BCR) strains. Growth of BCR cells was inhibited by ethylenediaminetetraacetate at a concentration of 400 mug/ml or less, whereas the BCS strain grew at ethylenediaminetetraacetate levels of 10,000 mug/ml. Phenylmercuric acetate and thimerosal inhibited growth of BCR and BCS cells at concentrations of 10 mug/ml or less. BCR cells were cross-resistant to >1,000 mug/ml concentrations of five other quaternary ammonium compounds, including three with C(16) alkyls and two with alkyl groups of shorter length. The BCS strain was also resistant to >1,000 mug/ml concentrations of the three quaternary ammonium compounds with C(16) alkyl groups but, in addition to BC, was inhibited by 200 mug/ml levels or less of the two quaternary ammonium compounds containing alkyl groups of less than 16 carbon atoms. 相似文献
6.
A motile, predacious bacterium which degraded Pythium debaryanum was strongly attracted to substances released into the medium by the fungus. A nonpredacious bacterium was not attracted to these substances. The predator bacterium was specifically attracted to cellulose and its oligomers which are known to be components of the cell wall of Pythium. Ethanol inhibited chemotaxis of the bacterium without affecting either its motility or its ability to degrade cellulose. A second predacious bacterium was isolated for the alga, Skeletonema costatum. The role of chemoreception in the detection of microbial prey by bacterial predators in natural habitats is discussed. 相似文献
7.
Total skin collagen is greatly increased in women with hirsuties. This is presumably due to androgen, whether locally produced or circulating. 相似文献
8.
J. L. Burton W. J. Cunliffe D. G. Millar Sam Shuster 《BMJ (Clinical research ed.)》1970,2(5712):769-771
Sebum excretion rates from forehead skin were measured serially during and after pregnancy in 10 normal women. Only minor fluctuations occurred during the middle and last trimesters of pregnancy, but there was a pronounced decrease in the postpartum period. Probably a powerful sebotrophic factor is present in pregnancy, but its nature is conjectural. 相似文献
9.
10.