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排序方式: 共有653条查询结果,搜索用时 15 毫秒
581.
582.
RD Calixto R Verlengia AH Crisp TB Carvalho MD Crepaldi AA Pereira AK Yamada GR da Mota CR Lopes 《Biology of sport / Institute of Sport》2014,31(4):289-294
This study aimed to compare the effects of different velocities of eccentric muscle actions on acute blood lactate and serum growth hormone (GH) concentrations following free weight bench press exercises performed by resistance-trained men. Sixteen healthy men were divided into two groups: slow eccentric velocity (SEV; n = 8) and fast eccentric velocity (FEV; n = 8). Both groups performed four sets of eight eccentric repetitions at an intensity of 70% of their one repetition maximum eccentric (1RMecc) test, with 2-minute rest intervals between sets. The eccentric velocity was controlled to 3 seconds per range of motion for SEV and 0.5 seconds for the FEV group. There was a significant difference (P < 0.001) in the kinetics of blood lactate removal (at 3, 6, 9, 15, and 20 min) and higher mean values for peak blood lactate (P = 0.001) for the SEV group (9.1 ± 0.5 mM) compared to the FEV group (6.1 ± 0.4 mM). Additionally, serum GH concentrations were significantly higher (P < 0.001) at 15 minutes after bench press exercise in the SEV group (1.7 ± 0.6 ng · mL−1) relative to the FEV group (0.1 ± 0.0 ng · mL−1). In conclusion, the velocity of eccentric muscle action influences acute responses following bench press exercises performed by resistance-trained men using a slow velocity resulting in a greater metabolic stress and hormone response. 相似文献
583.
584.
Cubero J Valero V Narciso D Rivero M Marchena JM Rodríguez AB Barriga C 《Molecular and cellular biochemistry》2006,293(1-2):79-85
The essential amino acid tryptophan is the precursor in the anabolic pathway of melatonin, a hormone with immunomodulatory properties. The present study shows the in vivo effect of tryptophan on the phagocytic function and oxidative metabolism of heterophils from Streptopelia roseogrisea of < 1 year of age, with a parallel evaluation of the plasma levels of melatonin. The L-tryptophan was administered orally (125 and 300 mg/kg b.w.) at 19:00, before the beginning of the period of darkness, for 7 days. At the end of the tryptophan treatment, determinations were made at 21:00 and 02:00 of the Phagocytosis Index, the Phagocytosis Percentage, the Phagocytic Efficiency and the superoxide anion levels in heterophils isolated from blood and of the plasma levels of melatonin. The results showed, for the determinations at 21:00 in the animals that had received 125 mg L-tryptophan/kg b.w., enhanced heterophil phagocytic function and raised levels of plasma melatonin, with no affect on the oxidative metabolism of the phagocytes. For the administration of the greater concentration of tryptophan (300 mg/kg b.w.), there were raised plasma melatonin levels together with increases in heterophil phagocytic capacity and phagocyte oxidative metabolism at 02:00. The results indicate that tryptophan administered orally at night to diurnal animals of less than 1 year in age affects the circulating levels of melatonin at the same time as inducing stimulation of the innate immune function. 相似文献
585.
Robert W. Behle PhD Patricia Tamez-Guerra Michael R. McGuire 《Biocontrol Science and Technology》2006,16(9):941-952
We investigated how altering parameters during the production of spray-dried lignin formulations affected the insecticidal activity of a baculovirus (AfMNPV), which was originally isolated from celery looper, Anagrapha falcifera (Kirby). Exposure to high temperature, varied pH of the dryer feedstock, substitution of formulation ingredients, and different commercial production lots of virus were evaluated for their effect on the insecticidal activity of AfMNPV. Insecticidal activities of treatments were determined by droplet-feeding assays using neonate Trichoplusia ni (Hübner) for dosage response or single-dosage comparisons. Unformulated virus exposed to 68oC for 2 h showed no loss of insecticidal activity, whereas exposure to 90oC for 30 min caused >20% loss of activity. Thus, residence at higher temperatures in drying systems could adversely affect virus activity. Spray-dried formulations made with Indulin AT lignin (pH 8.5, 9.5, and 10.5) lost insecticidal activity with increasing alkalinity of the dryer feedstock. In contrast to Indulin AT, the same formulations made with PC-1307 lignin did not lose insecticidal activity with increased alkalinity. Adding corn flour to spray-dried Indulin AT-based formulations improved insecticidal activity of the virus. These experiments demonstrated the importance of carefully selecting feed-stock ingredients and processing conditions when spray drying AfMNPV. 相似文献
586.
Shao ZH Hsu CW Chang WT Waypa GB Li J Li D Li CQ Anderson T Qin Y Schumacker PT Becker LB Hoek TL 《Cell biology and toxicology》2006,22(3):149-158
Grape seed proanthocyanidin extract (GPSE) at high doses has been shown to exhibit cytotoxicity that is associated with increased
apoptotic cell death. Nitric oxide (NO), being a regulator of apoptosis, can be increased in production by the administration
of GSPE. In a chick cardiomyocyte study, we demonstrated that high-dose (500 μg/ml) GSPE produces a significantly high level
of NO that contributes to increased apoptotic cell death detected by propidium iodide and terminal deoxynucleotidyl transferase-mediated
dUTP nick-end labeling (TUNEL) staining. It is also associated with the depletion of intracellular glutathione (GSH), probably
due to increased consumption by NO with the formation of S-nitrosoglutathione. Co-treatment with L-NAME, a NO synthase inhibitor, results in reduction of NO and apoptotic cell death.
The decline in reduced GSH/oxidized GSH (GSSG) ratio is also reversed. N-Acetylcysteine, a thiol compound that reacts directly with NO, can reduce the increased NO generation and reverse the decreased
GSH/GSSG ratio, thereby attenuating the cytotoxicity induced by high-dose GSPE. Taken together, these results suggest that
endogenous NO synthase (NOS) activation and excessive NO production play a key role in the pathogenesis of high-dose GSPE-induced
cytotoxicity. 相似文献
587.
Administration of a mutated myostatin propeptide to neonatal mice significantly enhances skeletal muscle growth 总被引:1,自引:0,他引:1
Zicong Li Baoping Zhao Yong Soo Kim Ching Yuan Hu Jinzeng Yang PhD 《Molecular reproduction and development》2010,77(1):76-82
Myostatin is a dominant inhibitor of skeletal muscle development and growth. As transgenic over‐expression of myostatin propeptide dramatically enhanced muscle mass, we hypothesized that administration of myostatin propeptide will increase muscle growth. In this study, the wild‐type form of porcine myostatin propeptide and its mutated form at the cleavage site of metalloproteinases of BMP‐1/TLD family were produced from insect cells. In vitro A204 cells reporter assays showed that both wild‐type and the mutated propeptides depressed myostatin activity. The recombinant propeptides at four‐fold myostatin concentration can effectively block myostatin function during co‐incubation with A204 cells. In particular, the mutated propeptide appeared much more effective than wild‐type propeptide over a long period during the in vitro co‐incubation. Administration of the mutated propeptide to neonatal mice at the age of 11 and 18 days was tested and showed significant increase in growth performance by 11–15% from the age of 25 to 57 days (P < 0.05). The major skeletal muscles of mice that were injected with mutated propeptide were 13.5–24.8% heavier than the control group (P < 0.05) as a result of muscle fiber hypertrophy. In conclusion, administration of the mutated myostatin propeptide during the neonatal period is an effective way for promoting muscle growth. Mol. Reprod. Dev. 77: 76–82, 2010. © 2009 Wiley‐Liss, Inc. 相似文献
588.
Joyce Lim Dr. Ariff Bongso PhD Shan Ratnam 《Molecular reproduction and development》1993,36(4):482-487
Slow cleavage rate has been a major contributory factor influencing embryo morphology in in vitro fertilization (IVF) programs. The role of transforming growth factor-b̃ (TGFb̃1) in improving this characteristic was evaluated using the murine model. Replicate batches of eight-cell compacting embryos from superovulated mice were divided into three groups. Group A were treated with 0.3 ng/ml TGFb̃1 at the initial compacting stage, followed by a second treatment of 0.1 ng/mL 22 h later at the cavitating stage; group B received 0.3 ng/ml TGFb̃1 at the cavitating stage; group C were controls. The percentages of treated embryos reaching fixed embryonic stages, total cell number (TCN), mitotic index, and incidence of chromosome anomalies were monitored. The percentage of embryos reaching the cavitating, expanded, hatching, and hatched stages in both treatment groups were not significantly different from control (96.6% ± 4.2% to 37.7% ± 12.7% vs. 95.3% ± 7.3% to 47.0% ± 3.5%; P > 0.05). Values between the two treatment groups were also not significantly different. Embryos in groups A and B produced significantly greater TCN at expanded blastocyst and hatching stages compared to controls (Group A: 107.0 ± 18.9 vs. 89.9 ± 17.4, P < 0.05 and 125.5 ± 16.4 vs. 113.9 ± 12.1, P < 0.05; Group B: 107.9 ± 14.0 vs. 89.9 ± 17.4, P < 0.05 and 124.9 ± 17.4 vs. 113.9 ± 12.1, P < 0.05). Values, however, were not significantly different between treatment groups. The mean mitotic index for eight-cell compacting embryos treated with a single dose of 0.3 ng/ml TGFb̃1 was significantly greater than control (0.1944 ± 0.1376 vs. 0.1282 ± 0.2573, P < 0.05). No significant increase in the incidence of chromosome anomalies was observed in embryos exposed to TGFb̃1. The results demonstrate that TGFb̃1 had a tremendous mitogenic effect on late murine embryonic stages and may thus be useful to improve embryo morphology in IVF programs and to produce adequate metaphases from biopsied embryos for preimplantation cytogenetic diagnosis. © 1993 Wiley-Liss, Inc. 相似文献
589.
Hend M. Nawara PhD Said M. Afify PhD Ghmkin Hassan MSc Maram H. Zahra PhD Marwa N. Atallah PhD Akimasa Seno PhD Masaharu Seno PhD 《Cell biology international》2021,45(4):749-756
Angiogenesis is generally involved in tumor growth and metastasis. Cancer stem cells (CSCs) are considered to facilitate the angiogenesis. Therefore, CSCs could be the effective targets to stop angiogenesis. Recently, our group successfully generated CSC models from induced pluripotent stem cells (iPSCs) in the presence of conditioned medium derived from cancer derived cells. These novel model CSCs has been characterized by highly tumorigenic, angiogenic and metastatic potentials in vivo. The angiogenic potential of CSCs has been explained by the expression of both angiogenic factors and their receptors implying the angiogenesis in autocrine manner. In this protocol we optimized the method to evaluate tumor angiogenesis with the CSC model, which was described effective to assess sorafenib as an antiangiogenic drug, on chick chorioallantoic membrane (CAM) assay. Our results demonstrate that CSCs developed from iPSCs and CAM assay are a robust and cost-effective tool to evaluate tumor angiogenesis with CSCs. Collectively, CSCs in CAM assay could serve as a very useful model for the screening of potential therapeutic agents targeting tumor angiogenesis. 相似文献
590.
Yuping Gou PhD Sufan Guo Ms Peter Quandahor PhD Chunchun Li PhD Qiangyan Zhang PhD Jing-Jiang Zhou PhD Chang-Zhong Liu PhD 《Journal of Applied Entomology》2021,145(5):449-457
In this study, the effects of temperature on the growth, development, survival, fecundity and other population parameters of two local Bradysia species B. odoriphaga and B. impatiens were studied at four constant temperatures (25, 28, 31 and 34°C). The results show that 25°C is the optimum temperature for the growth and development of B. odoriphaga, while 28°C is more favourable for B. impatiens. The temperature of 31°C restricted the growth and development, while the temperature of 34°C inhibited the eggs hatching in both species, resulting in no egg survival and no subsequent development. High temperatures (>28°C) prolonged the 4th larval stage duration, mean generation time (T) and population doubling time (Dt) of both species. The high temperature of 31°C greatly shortened the female longevity, weakened the oviposition and reduced the survival of both species. Moreover, the life table parameters R0, rm and λ were also suppressed by this high temperature. However, the high temperature of 31°C had little impact on the egg survival, pupal weight and male longevity. In addition, at 31°C, the values of R0, rm and λ of B. odoriphaga were higher than those of B. impatiens, suggesting that B. odoriphaga is more tolerant to high temperature than B. impatiens. The differences between two Bradydsia species seem determined genetically. Our findings are important for better understanding their biological characteristics at a certain constant temperature and demonstrate the possibility to control and manage those two Bradysia species by increasing ambient temperature. 相似文献