全文获取类型
收费全文 | 817篇 |
免费 | 44篇 |
国内免费 | 27篇 |
出版年
2023年 | 8篇 |
2022年 | 19篇 |
2021年 | 16篇 |
2020年 | 8篇 |
2019年 | 30篇 |
2018年 | 30篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 25篇 |
2014年 | 41篇 |
2013年 | 69篇 |
2012年 | 32篇 |
2011年 | 61篇 |
2010年 | 30篇 |
2009年 | 44篇 |
2008年 | 42篇 |
2007年 | 38篇 |
2006年 | 34篇 |
2005年 | 39篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 18篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 3篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 12篇 |
1995年 | 18篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 4篇 |
1990年 | 9篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
排序方式: 共有888条查询结果,搜索用时 31 毫秒
111.
The variation in acid phosphatase (EC 3.1.3.2) activity inAntheraea mylitta was similar in all light and dark groups exposed to different photophases (LD =0:24, 24:0, 18:6, 14:10, 10:14 and 12:12 h)
maintaining all along a higher activity than its alkaline counterpart. The highest activity was recorded on day 82 in LD group
10:14 h. The non-diapausingPhilosamia ricini larvae registered highest activity in LD group 0:24 h on day 5. Alkaline phosphatase (EC 3.1.3.1) activity was low all through
metamorphosis in both the lepidopterans, although significantly elevated activity was observed on day 5 in larvae of allPhilosamia ricini LD regimens and on day 82 inAntherae mylitta. Photoperiodic effect on Phosphorylase (EC 2.3.1.1) activity, glycogen and inorganic phosphates content have also been studied.
Exposure to LD 10:14, 14:10 and 18:6 h provoked early diapause termination inAntheraea mylitta. The non-diapausingPhilosamia ricini was unaffected in moth emergence but the emerged adults of LD 24:0 and 0:24 h groups were unhealthy, small and did not mate
or oviposit. 相似文献
112.
113.
Metabolic responses to acute handling by fingerling inland and anadromous striped bass 总被引:3,自引:0,他引:3
Fed and 3-day fasted inland (average mass: 6.97 g) and anadromous (average mass: 6.54 g) striped bass Morone saxatilis fingerlings were held in dipnets above water for 5 min in groups of six. Severity of the response to this handling was measured by whole-body glucose, glycogen, and lactic acid in non-handled bass (considered control level), and then at 30 min, 1, 6, 12, 24 and 48 h recovery. At resting levels, both fed and fasted inland bass showed significantly higher concentrations of the whole body variables than anadromous bass. All four groups of bass showed an increase in lactic acid and glucose immediately after handling, with a concomitant decrease in glycogen. Peak levels of glucose and lactic acid were similar in the four groups. Fasting did not have an effect on the glucose and lactic acid responses, but did affect the glycogen response. The two fasted groups did not return to control glycogen concentrations during the 48-h recovery period. By 48 h, both glucose and lactic acid had returned to control levels. It is concluded that inland and anadromous strains of fingerling striped bass do not differ in their sensitivity to an acute handling stress. Recovery of glycogen energy stores following handling is much better if fish are not fasted before handling. 相似文献
114.
Effects of central administration of arginine vasotocin on monoaminergic neurotransmitters and energy metabolism of rainbow trout brain 总被引:1,自引:0,他引:1
S. SangiaoAlvarellos M. Lapido J. M. Miguez J. L. Soengas 《Journal of fish biology》2004,64(5):1313-1329
In a first set of experiments, intracerebroventricular (ICV) treatment of 1 μl 100 g−1 body mass of Cortland saline containing different doses (1–20 nmol μl−1 ) of arginine vasotocin (AVT) produced after 180 min dose‐dependent changes in levels of brain neurotransmitters in several brain regions and pituitary of rainbow trout Oncorhynchus mykiss . Thus, an enhancement of serotonergic and dopaminergic activity, together with a decreased noradrenergic activity, were observed both in the hypothalamus and pituitary of AVT‐treated fish. In the other brain regions assessed, only increased serotonergic activity in the optic lobes, and decreased dopaminergic activity in the telencephalon of AVT‐treated fish were noticed. Changes observed in monoamine levels resemble those observed during osmotic adaptation of euryhaline fishes. In a second set of experiments, fish were ICV injected with AVT as described above to assess changes in several variables of brain energy metabolism. The results obtained show a dose‐dependent enhancement of brain glycogenolytic potential in the brain of AVT‐treated fish, that again resemble the changes observed in euryhaline fishes during osmotic acclimation. 相似文献
115.
Xiu-Zhen Zhang Xue-Juan Li Hong-Fang Ji 《Biochemical and biophysical research communications》2009,383(3):275-279
Despite the rapid technical progress in pharmaceutical industry in the past decade, it is still a great challenge to find new drugs and the situation seems more and more serious. However, the history of pharmaceutical industry clearly indicated that the significance of drug discovery went far beyond providing new drugs. For instance, drugs or candidates could be used as selective probes to reveal novel cellular mechanisms, which is a fundamental tenet of chemical biology. More interestingly, accumulating evidence indicates that drugs and candidates can find important use in stem cell biology. Not only approved drugs but also undeveloped pharmacological agents could serve as efficient agents to regulate stem cell fate. Moreover, the target and activity knowledge accumulated during the drug discovery process will help select the stem cell fate modulators in a rational manner. As the progress in stem cell biology will bring positive influence to drug discovery, it can be expected that the current drug discovery efforts will finally bear great fruits in the future. 相似文献
116.
Multitargeting involves the application of molecules that are deliberately intended to bind to two or more unrelated cellular targets with high affinity. In epigenetic chemical biology and drug discovery, the rational design of multitargeting agents has evolved to a sophisticated level, and there are now five examples that have reached clinical trials. This review covers recent developments in the field and future prospects. 相似文献
117.
An extreme oligotroph, Rhodococcus erythropolis N9T-4, showed intracellular accumulation of trehalose and glycogen under oligotrophic conditions. No trehalose accumulation was observed in cells grown on the rich medium. Deletion of the polyphosphate kinase genes enhanced the trehalose accumulation and decreases the intracellular glycogen contents, suggesting an oligotrophic relationship between among the metabolic pathways of trehalose, glycogen, and inorganic polyphosphate biosyntheses. 相似文献
118.
A. David Purdon James L. Daniel Gwendolyn J. Stewart Holm Holmsen 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,800(2):178-187
Mechanisms are assumed to exist in the resting platelet which maintain the concentration of cytoplasmic free calcium below that level required to activate cellular responses. To assess such processes the porcine platelet plasma membrane was selectively lysed with digitonin and the uptake (or flux) of free calcium monitored by an extracellular calcium electrode. Lysis resulted in an immediate lowering of the extracellular free calcium, due to the action of intracellular organelle(s) acting on the extracellular space through the permeabilized plasma membrane. In resting platelets, the rate of calcium uptake was first order with respect to the extracellular prelytic calcium concentration, and hence the cytoplasmic free concentration was found to be 1·10?7 M by extrapolation to a point of zero flux (i.e., the null point). This approach could not be used with thrombin-stimulated platelets, as external calcium was required for both secretion of ATP + ADP and aggregation. Nevertheless, evidence for an increase in cytoplasmic free calcium after thromin stimulation was obtained. Metabolic inhibitors and agents known to inhibit calcium uptake by mitochondria had no effect on the calcium flux following lysis, indicating different mechanisms for calcium homeostasis in the platelet when compared with other cell types (e.g., liver). Levels of ionophore A23187, which caused platelet aggregation, gave a massive release of the nonmitochondrial pool of calcium into the cytoplasmic space. Thus, in porcine platelets an intracellular energy-requiring calcium pump, which sequesters calcium in a nonmitochondrial membranous compartment, is crucial for intracellular calcium homeostasis. 相似文献
119.
120.