全文获取类型
收费全文 | 2724篇 |
免费 | 247篇 |
国内免费 | 1篇 |
出版年
2023年 | 16篇 |
2022年 | 21篇 |
2021年 | 31篇 |
2020年 | 41篇 |
2019年 | 40篇 |
2018年 | 39篇 |
2017年 | 61篇 |
2016年 | 63篇 |
2015年 | 115篇 |
2014年 | 100篇 |
2013年 | 180篇 |
2012年 | 185篇 |
2011年 | 167篇 |
2010年 | 141篇 |
2009年 | 116篇 |
2008年 | 106篇 |
2007年 | 79篇 |
2006年 | 90篇 |
2005年 | 95篇 |
2004年 | 77篇 |
2003年 | 69篇 |
2002年 | 74篇 |
2001年 | 64篇 |
2000年 | 35篇 |
1999年 | 47篇 |
1998年 | 54篇 |
1997年 | 29篇 |
1996年 | 42篇 |
1995年 | 30篇 |
1994年 | 35篇 |
1993年 | 36篇 |
1992年 | 40篇 |
1991年 | 38篇 |
1990年 | 32篇 |
1989年 | 42篇 |
1988年 | 31篇 |
1987年 | 39篇 |
1986年 | 36篇 |
1985年 | 35篇 |
1984年 | 36篇 |
1983年 | 36篇 |
1982年 | 22篇 |
1981年 | 32篇 |
1980年 | 34篇 |
1979年 | 24篇 |
1978年 | 26篇 |
1977年 | 21篇 |
1976年 | 20篇 |
1974年 | 16篇 |
1967年 | 15篇 |
排序方式: 共有2972条查询结果,搜索用时 15 毫秒
101.
Summary A population of nerve fibres in the gastro-intestinal tract of mice showing a high affinity for quinacrine was revealed by fluorescence microscopy. Similar results were obtained in rats and guinea pigs. Whole-mounts of sheets of the smooth muscle layer following incubation in 10-6-10-7 M quinacrine for 15–60 min revealed fine fluorescent varicose nerve fibers in the myenteric plexus of Auerbach both around nerve cell bodies and in the interconnecting strands. Many fibers were also present between the strands of the plexus, especially running parallel to the circular muscle layer. Such fibers were not seen in similarly quinacrine-incubated irides. A proportion of the cell bodies in Auerbach's plexus also showed quinacrine accumulation. These cells were apparently smaller neurons, sometimes with fluorescent processes. Intraperitoneal injections of quinacrine failed to demonstrate nerve fibers, but some cell bodies in Auerbach's plexus were positive. Subsequent paraformaldehyde treatment for monoamine visualization showed persistent adrenergic nerve terminals in the intestine and iris. These nerves seemed to be fewer and had a more yellow fluorescence than normally. The identity of the quinacrine-positive fibers is discussed with respect to recent suggestions that purinergic, substance P, enkephalin, and somatosin-containing nerves, in addition to adrenergic and cholinergic nerves, are present in the gut wall.Supported by the Swedish Medical Research Council (04X-03185). Magnus Bergvalls Stiftelse and Karolinska Institutets Fonder. For generous gifts of Mepacrine we thank Winthrop, Skärholmen, Stockholm, Sweden. The skilful technical assistance of Miss Gerd Boetius and Miss Maud Eriksson is gratefully acknowledged 相似文献
102.
Suspensions of dispersed islet cells were prepared by shaking collagenaseisolated pancreatic islets of in Ca2+-free buffer. The dispersed cells exhibited a glucose uptake with stereospecificity for the d isomer and concentrated Rb+ about 30-fold from a medium containing 70 μm RbCl. These results compare well with previous observations on unbroken islets and indicate that the dispersion procedure does not cause serious damage to the plasma membranes of the β-cells. By double isotope labeling and centrifuging the incubated cells through oil, incubation times as short as only a few seconds can be used. The elimination of the extracellular tissue space and the short incubation times should facilitate the study of transport kinetics in the pancreatic islet cells. 相似文献
103.
104.
105.
E A Erenpre?sa 《Biulleten' eksperimental'no? biologii i meditsiny》1977,83(4):503-504
The author studied the mechanisms and the applicability in histochemistry of the sodium bisulfate treatment with subsequent toluidine and methylene blue staining after Felgen's hydrolysis. Bisulfite treatment proved to increase the reaction intensity 11/2-fold; the stain is bound stoichiometrically. Toludidine blue results in a metachromatic and anisotropic staining of the cell nuclei. The method is recommended as a sensitive test for DNA in cytochemical investigations and for the study of dichroism of the DNA-containing structures. 相似文献
106.
Resistance to nisin and production of nisin-inactivating enzymes by several Bacillus species 总被引:7,自引:0,他引:7
B Jarvis 《Journal of general microbiology》1967,47(1):33-48
107.
Katharina Meurer Jennie Barron Claire Chenu Elsa Coucheney Matthew Fielding Paul Hallett Anke M. Herrmann Thomas Keller John Koestel Mats Larsbo Elisabet Lewan Dani Or David Parsons Nargish Parvin Astrid Taylor Harry Vereecken Nicholas Jarvis 《Global Change Biology》2020,26(10):5382-5403
Soil degradation is a worsening global phenomenon driven by socio‐economic pressures, poor land management practices and climate change. A deterioration of soil structure at timescales ranging from seconds to centuries is implicated in most forms of soil degradation including the depletion of nutrients and organic matter, erosion and compaction. New soil–crop models that could account for soil structure dynamics at decadal to centennial timescales would provide insights into the relative importance of the various underlying physical (e.g. tillage, traffic compaction, swell/shrink and freeze/thaw) and biological (e.g. plant root growth, soil microbial and faunal activity) mechanisms, their impacts on soil hydrological processes and plant growth, as well as the relevant timescales of soil degradation and recovery. However, the development of such a model remains a challenge due to the enormous complexity of the interactions in the soil–plant system. In this paper, we focus on the impacts of biological processes on soil structure dynamics, especially the growth of plant roots and the activity of soil fauna and microorganisms. We first define what we mean by soil structure and then review current understanding of how these biological agents impact soil structure. We then develop a new framework for modelling soil structure dynamics, which is designed to be compatible with soil–crop models that operate at the soil profile scale and for long temporal scales (i.e. decades, centuries). We illustrate the modelling concept with a case study on the role of root growth and earthworm bioturbation in restoring the structure of a severely compacted soil. 相似文献
108.
Özgür Aykut Kara Altan Gökşen Tosun Nazan Tekin Şaban Gökçe İsa 《Molecular biology reports》2021,48(4):3439-3449
Molecular Biology Reports - Heat shock protein 90 (Hsp90) is a key chaperone that is abnormally expressed in cancer cells, and therefore, designing novel compounds to inhibit chaperone activities... 相似文献
109.
Henrique Barbosa Thais A. Costa-Silva Geanne A. Alves Conserva Adelson J. Araujo Ana Luísa L. Lordello Guilherme M. Antar Maiara Amaral Marisi G. Soares Andre G. Tempone João Henrique G. Lago 《化学与生物多样性》2021,18(4):e2001022
One new aporphine, dicentrine-β-N-oxide ( 1 ), together with five related known alkaloids dehydrodicentrine ( 2 ), predicentrine ( 3 ), N-methyllaurotetanine ( 4 ), cassythicine ( 5 ), and dicentrine ( 6 ) were isolated from the leaves of Ocotea puberula (Lauraceae). Antiprotozoal activity of the isolated compounds was evaluated in vitro against trypomastigote forms of Trypanosoma cruzi. Among the tested compounds, alkaloid 1 exhibited higher potential with EC50 value of 18.2 μM and reduced toxicity against NCTC cells (CC50>200 μM – SI>11.0), similar to positive control benznidazole (EC50 of 17.7 μM and SI=10.7). Considering the promising results of dicentrine-β-N-oxide ( 1 ) against trypomastigotes, the mechanism of parasite death caused by this alkaloid was investigated. As observed, this compound reached the plasma membrane electric potential directly after 2 h of incubation and triggered mitochondrial depolarization, which probably leads to trypomastigote death. Therefore, dicentrine-β-N-oxide ( 1 ), reported for the first time in this work, can contribute to future works for the development of new trypanocidal agents. 相似文献
110.
Reagan M. Jarvis Jana Göttert Reagan M. Jarvis Jana Göttert Michael P. Murphy 《Free radical research》2013,47(9):1041-1046
Mitochondrial production of reactive oxygen species (ROS) is widely reported as a central effector during TNF-induced necrosis. The effect of a family of mitochondria-targeted antioxidants on TNF-induced necrosis of L929 cells was studied. While the commonly used lipid–soluble antioxidant BHA effectively protected cells from TNF-induced necrosis, the mitochondria-targeted antioxidants MitoQ3, MitoQ5, MitoQ10 and MitoPBN had no effect on TNF-induced necrosis. Since BHA also acts as an uncoupler of mitochondrial membrane potential, two additional uncouplers were tested. FCCP and CCCP both provided dose-dependent inhibition of TNF-induced necrosis. In conclusion, the generation of mitochondrial ROS may not be necessary for TNF-induced necrosis. Instead, these results suggest alternative mitochondrial functions, such as a respiration-dependent process, are critical for necrotic death. 相似文献