全文获取类型
收费全文 | 192篇 |
免费 | 23篇 |
国内免费 | 1篇 |
专业分类
216篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 11篇 |
2010年 | 14篇 |
2009年 | 15篇 |
2008年 | 13篇 |
2007年 | 11篇 |
2006年 | 10篇 |
2005年 | 3篇 |
2004年 | 9篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有216条查询结果,搜索用时 9 毫秒
181.
Dairy cows often have to choose which of two sides to enter in the milking parlour. Some cows are very consistent in this choice, and it is common to assume that when these cows are more disturbed are being milked in their non-preferred side. Such disturbance might involve significantly poor welfare. In order to assess this assumption, we decided to study the behaviour and milk yield of dairy cows and their relationships with side preference in the milking parlour. The study was carried out at Cambridge University Farm, in a two-sided tandem milking parlour. The data collection followed the daily management routine. We recorded the side chosen by each cow (left or right) during 40 milking sessions. Data from 70 cows, which were present in at least 25 milking sessions (mode=36), were included in the statistical analysis. Cows' reactivity (CR) during premilking udder preparation, time spent fitting the milking cluster (FT), milk yield (MY) and duration of milking (DM) were measured. There was evident individual variation in the consistency of side choice. Individual differences (ANOVA, P<0.001) were also found in CR, FT, MY and DM; although these variables were not significantly affected by the side or the interaction animalxside (ANOVA, P>0.05). The comparison between left and right side means (paired t-test) of these variables did not show significant differences (P>0.05). We concluded that there is no evidence that the cows were discomforted or stressed when milked in the non-preferred side of the milking parlour. 相似文献
182.
Cytochemical demonstration of hydrogen peroxide in polymorphonuclear leukocyte phagosomes 总被引:6,自引:1,他引:6 下载免费PDF全文
Phagocytosis by polymorphonuclear leukocytes (PMN) is accompanied by specific morphological and metabolic events which may result in the killing of internalized micro-organism. Hydrogen peroxide is produced in increased amounts during phagocytosis (17) and in combination with myeloperoxidase and halide ions constitute a potent, microbicidal mechanism (8,9,11). There can be direct iodination of micro-organisms (10), or alternatively, other intermediate reaction products, i.e. chloramines and aldehydes (21), can exert a microbicidal effect. The H2O2-peroxidase-halide system is presumed to operate within the phagocytic vacuole (12,18). Myeloperoxidase, present in the primary granules of PMN, enters the phagocytic vacuole during degranulation (1,4,7), and halide ions are probably derived from the extracellular medium or are present in the PMN (see 11, 18). For the operation of this system in intact cells, the presence of H2O2 in the phagocytic vacuole is necessary, and indeed this has been suggested by the work of several investigators (12, 18, 21). In the present investigation, the diaminobenzidine reaction of Graham and Karnovsky (5), modified to utilize endogenous myeloperoxidase and hydrogen peroxide, has been applied to actively phagocytizing PMN to demonstrate cytochemically the presence of H2O2 in the phagocytic vacuole. 相似文献
183.
A phylogenetic survey using the polymerase chain reaction (PCR) has
identified four major P element subfamilies in the saltans and willistoni
species groups of Drosophila. One subfamily, containing about half of the
sequences studied, consists of elements that are very similar to the
canonical (and active) P element from D. melanogaster. Within this
subfamily, nucleotide sequence differentiation among different copies from
the same species and among elements from different species is relatively
low. This observation suggests that the canonical elements are relatively
recent additions to the genome or, less likely, are evolving slowly
relative to the other subfamilies. Elements belonging to the three
noncanonical lineages are distinct from the canonical elements and from one
another. Furthermore, there is considerably more sequence variation, on the
average, within the noncanonical subfamilies compared to the canonical
elements. Horizontal transfer and the coexistence of multiple,
independently evolving element subfamilies in the same genome may explain
the distribution of P elements in the saltans and willistoni species
groups. Such explanations are not mutually exclusive, and each may be
involved to varying degrees in the maintenance of P elements in natural
populations of Drosophila.
相似文献
184.
The cationic lipohexapeptide (S)-[2, 3-bis(palmitoyloxy)-(2RS)-propyl]-N-palmitoyl-(R)-Cys-(S)-Ser-(S)- Lys 4-OH, trihydrochloride (Pam3Cys-Ser-Lys4) is a synthetic analog of the triacylated N-terminal part of bacterial lipoproteins. In this study we addressed the question of whether Pam3Cys-Ser-Lys4 could modify the organization of the plasma membrane of Chinese hamster ovary cells. 1-Acyl-2-[6-(7-nitro-2-1, 3-benzoxadiazol-4-yl)amino]caproyl]-sn-glycero-3-phosphocholine (C6-NBD-PC) diffusion was followed by fluorescence recovery after photobleaching experiments carried out on the plasma membrane of Chinese hamster ovary cells. Incubation of cells in the presence of Pam3Cys-Ser-Lys4 induced an increase in the lateral diffusion coefficient and in the immobile fraction of C6-NBD-PC probes. Various control experiments have shown that the increase in the immobile fraction was not due to probe internalization induced by Pam3Cys-Ser-Lys4. Back-exchange experiments showed that a good correlation exists between the fractions of immobilized probes and nonextractable probes in the plasma membrane of Chinese hamster ovary cells. A useful way to analyze the origin of probe immobilization (micrometer-sized domains or aggregated patches of proteins) is to carry out fluorescence recovery after photobleaching experiments at variable observation radii. This type of experiment, carried out on the plasma membrane of Chinese hamster ovary cells incubated with Pam3Cys-Ser-Lys4, confirmed that the lipopeptide induced the aggregation of proteins of Chinese hamster ovary plasma membrane. Lipids which were trapped inside these aggregates were thus prevented from diffusing at long range in the plasma membrane plane and behave as an immobile fraction. 相似文献
185.
Anna E van der Windt Esther Haak Ruud HJ Das Nicole Kops Tim JM Welting Marjolein MJ Caron Niek P van Til Jan AN Verhaar Harrie Weinans Holger Jahr 《Arthritis research & therapy》2010,12(3):R100
Introduction
Chondrocytes experience a hypertonic environment compared with plasma (280 mOsm) due to the high fixed negative charge density of cartilage. Standard isolation of chondrocytes removes their hypertonic matrix, exposing them to nonphysiological conditions. During in vitro expansion, chondrocytes quickly lose their specialized phenotype, making them inappropriate for cell-based regenerative strategies. We aimed to elucidate the effects of tonicity during isolation and in vitro expansion on chondrocyte phenotype. 相似文献186.
187.
Herman MJ Sontrop Perry D Moerland René van den Ham Marcel JT Reinders Wim FJ Verhaegh 《BMC bioinformatics》2009,10(1):389-22
Background
Large discrepancies in signature composition and outcome concordance have been observed between different microarray breast cancer expression profiling studies. This is often ascribed to differences in array platform as well as biological variability. We conjecture that other reasons for the observed discrepancies are the measurement error associated with each feature and the choice of preprocessing method. Microarray data are known to be subject to technical variation and the confidence intervals around individual point estimates of expression levels can be wide. Furthermore, the estimated expression values also vary depending on the selected preprocessing scheme. In microarray breast cancer classification studies, however, these two forms of feature variability are almost always ignored and hence their exact role is unclear. 相似文献188.
Autophagy initiation is strictly dependent on phosphatidylinositol 3-phosphate (PI3P) synthesis. PI3P production is under tight control of PI3Kinase, hVps34, in complex with Beclin-1. Mammalian cells express several PI3P phosphatases that belong to the myotubularin family. Even though some of them have been linked to serious human diseases, their cellular function is largely unknown. Two recent studies indicate that PI3P metabolism involved in autophagy initiation is further regulated by the PI3P phosphatases Jumpy and MTMR3. Additional pools of PI3P, upstream of mTOR and on the endocytic pathway, may modulate autophagy indirectly, suggesting that other PI3P phosphatases might be involved in this process. This review sums up our knowledge on PI3P phosphatases and discusses the recent progress on their role in autophagy. 相似文献
189.
190.
Femke AH van der Linden Jolijn J Kragt Margarethe van Bon Martin Klein Alan J Thompson Henk M van der Ploeg Chris H Polman Bernard MJ Uitdehaag 《BMC neurology》2008,8(1):2