全文获取类型
收费全文 | 2334篇 |
免费 | 225篇 |
国内免费 | 206篇 |
出版年
2024年 | 12篇 |
2023年 | 114篇 |
2022年 | 196篇 |
2021年 | 307篇 |
2020年 | 275篇 |
2019年 | 249篇 |
2018年 | 193篇 |
2017年 | 124篇 |
2016年 | 61篇 |
2015年 | 105篇 |
2014年 | 130篇 |
2013年 | 134篇 |
2012年 | 89篇 |
2011年 | 103篇 |
2010年 | 51篇 |
2009年 | 62篇 |
2008年 | 63篇 |
2007年 | 62篇 |
2006年 | 64篇 |
2005年 | 49篇 |
2004年 | 38篇 |
2003年 | 36篇 |
2002年 | 30篇 |
2001年 | 15篇 |
2000年 | 8篇 |
1999年 | 16篇 |
1998年 | 14篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 15篇 |
1983年 | 6篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1969年 | 3篇 |
排序方式: 共有2765条查询结果,搜索用时 218 毫秒
1.
G. Larivière-Gauthier A. Thibodeau É. Yergeau P. Fravalo 《Letters in applied microbiology》2021,72(2):113-120
Recent studies have shown that Salmonella shedding status affects sows’ microbiota during gestation and that these modifications are reflected in the faecal microbiota of their piglets at weaning. The aims of this study were: (a) to evaluate the persistence, up to the fattening period, of the previously measured link between the microbiota of piglets and their mothers’ Salmonella shedding status; and (b) measure the impact of the measured microbiota variations on their Salmonella excretion at this stage. To achieve this, 76 piglets born from 19 sows for which the faecal microbiota was previously documented, were selected in a multisite production system. The faecal matter of these swine was sampled after 4 weeks, at the fattening stage. The Salmonella shedding status and faecal microbiota of these animals were described using bacteriological and 16S rRNA gene amplicon sequencing respectively. The piglet digestive microbiota association with the Salmonella shedding status of their sows did not persist after weaning and did not affect the risk of Salmonella excretion during fattening, while the birth mother still affected the microbiota of the swine at fattening. This supports the interest in sows as a target for potentially transferrable microbiota modifications. 相似文献
2.
Jun‐juan Wang Qi‐min Zhang Wei‐wei Ni Xin Zhang Ying Li Ai‐li Li Peng Du Chun Li Su‐su Yu 《Microbiology and immunology》2019,63(8):303-315
We investigated the correlation between the beneficial effect of Lactobacillus acidophilus on gut microbiota composition, metabolic activities, and reducing cow's milk protein allergy. Mice sensitized with β‐lactoglobulin (β‐Lg) were treated with different doses of L. acidophilus KLDS 1.0738 for 4 weeks, starting 1 week before allergen induction. The results showed that intake of L. acidophilus significantly suppressed the hypersensitivity responses, together with increased fecal microbiota diversity and short‐chain fatty acids (SCFAs) concentration (including propionate, butyrate, isobutyrate, and isovalerate) when compared with the allergic group. Moreover, treatment with L. acidophilus induced the expression of SCFAs receptors, G‐protein–coupled receptors 41 (GPR41) and 43 (GPR43), in the spleen and colon of the allergic mice. Further analysis revealed that the GPR41 and GPR43 messenger RNA expression both positively correlated with the serum concentrations of transforming growth factor‐β and IFN‐γ (p < .05), but negatively with the serum concentrations of IL‐17, IL‐4, and IL‐6 in the L. acidophilus–treated group compared with the allergic group (p < .05). These results suggested that L. acidophilus protected against the development of allergic inflammation by improving the intestinal flora, as well as upregulating SCFAs and their receptors GPR41/43. 相似文献
3.
4.
5.
6.
Dr. Shigeru Sakiyama Yohko Nakamura Katsuo Tokunaga Hiroshi Takazawa Yoshinori Ohwaki Toshio Nagano 《Cell and tissue research》1989,258(2):225-231
Summary In-situ hybridization experiments have been performed using isoactin ( and )-specific riboprobes in various tissues of the rat and mouse. Distribution of the grains of actin mRNAs for both and types was similar throughout sections of the rat testis. Although both mRNAs were evenly distributed in the seminiferous tubule, extremely heavy labeling was observed in about 10% of the seminiferous tubules that could be identified as stage XII of spermatogenesis. At high magnification, grains of the mRNA were found in the cytoplasm of elongating spermatids and in the Sertoli cell cytoplasm at the adluminal side. Much higher density of the grains of mRNA was observed in the neck region of the spermatids at stage XII. Thus, the dense distribution of cytoskeletal actin mRNAs is stage-specific in the tubule during spermatogenesis in the rat. The high expression of both and actin mRNAs was also observed in the epithelial cells of the intestinal crypts. 相似文献
7.
Ecophysiology of Aufwuchs-eating cichlids in Lake Tanganyika: niche separation by trophic specialization 总被引:1,自引:0,他引:1
Christian Sturmbauer Wolfgang Mark Reinhard Dallinger 《Environmental Biology of Fishes》1992,35(3):283-290
Synopsis The Aufwuchs-eating cichlids of Lake Tanganyika show clear trophic differences that are correlated to their morphology, physiology and foraging behaviour. The species are grouped into three categories of relative intestinal length according to their feeding habits. A correlation between the intestinal length and the diet could be demonstrated, ranging from around 2.5 for species ingesting more animal food, to 7.8 for detritivorous and microalgivorous species. The relative intestinal length of domesticTropheus moorii, raised in aquaria was significantly lower than that of wild individuals by a factor of 1.7, demonstrating a wide range of phenotypic adaptability. The activities of trypsin and amylase were at an equal level in four Aufwuchseating species, but the activity of laminarinase of a detritivorous-microalgivorous species (Petrochromis orthognathus) was 2.6 times higher than that of an algivorous species (Tropheus moorii). The laminarinase seems to be an excellent marker enzyme for detritivorous or microalgivorous feeding. 相似文献
8.
Feces of wild chimpanzees in the Mahale Mountains, Tanzania, were inspected for intestinal parasites under a compound microscope.
Eggs or larvae ofOesophagostomum, Strongyloides, Trichuris, Prosthenorchis, andBertiella were found. Intestinal nematodes significantly increased in the mid-rainy season. This finding supports (or, at least, is
not in conflict with) the hypothesis thatAspilia leaves which are occasionally swallowed by chimpanzees may function as a vermicide, since ingestion of such leaves also increases
significantly in the mid-rainy season. 相似文献
9.
The effects of intracerebroventricular (ICV) and intrathecal (IT) administration of calcitonin gene-related peptide (CGRP) on intestinal motility were examined in conscious rats chronically fitted with intraparietal electrodes in the duodeno-jejunum and a cannula in a cerebral lateral ventricle or catheter in the subarachnoid space. ICV administration of CGRP (0.5–10 μg) restores the fasted pattern of intestinal motility in fed rats in a dose-related manner. Intrathecal administration of CGRP or calcitonin also induces fasted pattern but after a 30 min delay. These effects persisted after transection of the spinal cord and no change in intestinal motility appeared after intravenous administration of CGRP at a dose effective when given IT. This study suggests that CGRP, as calcitonin, has a neuromodulatory role in the control of intestinal motility at both brain and spinal cord levels. 相似文献
10.
A. J. H. de Ruiter Y. L. Hoogeveen S. E. Wendelaar Bonga 《Cell and tissue research》1985,240(1):191-198
Summary Intestinal and gall-bladder epithelial cells in sticklebacks have been examined in ultrathin sections and freeze-etch replicas. Enterocytes throughout the intestine appear to have a well-developed basal labyrinth similar to that of renal tubular cells, consisting of baso-lateral infoldings closely associated with numerous mitochondria. The lumen inside these intracellular membranes is continuous with the intercellular space via pores. Such a membrane system is also present in the epithelial cells lining the gall bladder, distinguishing them from gall-bladder cells of higher vertebrates. Morphometric analysis indicates that the basal labyrinth of enterocytes in the posterior part of the intestine increases markedly in both sexually mature males and androgen-treated females. This does not occur in the anterior part or gall bladder. In sticklebacks, androgens cause reduced urine excretion and enhanced fluid release via the anus. We conclude that the cells lining the intestine and gall bladder possess an extensive basal labyrinth that may function as a backward channel system, enabling fluid to be produced in the intestine of fish. The androgen-induced increase in the extent of the basal labyrinth in the posterior part of the intestine may be related to the enhanced rate of intestinal fluid excretion observed in sexually mature male sticklebacks. 相似文献