全文获取类型
收费全文 | 740篇 |
免费 | 77篇 |
国内免费 | 2篇 |
出版年
2023年 | 8篇 |
2021年 | 11篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 18篇 |
2014年 | 18篇 |
2013年 | 22篇 |
2012年 | 40篇 |
2011年 | 37篇 |
2010年 | 31篇 |
2009年 | 20篇 |
2008年 | 34篇 |
2007年 | 26篇 |
2006年 | 19篇 |
2005年 | 25篇 |
2004年 | 23篇 |
2003年 | 15篇 |
2002年 | 19篇 |
2001年 | 21篇 |
2000年 | 17篇 |
1999年 | 15篇 |
1998年 | 19篇 |
1997年 | 8篇 |
1995年 | 8篇 |
1993年 | 7篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 17篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 7篇 |
1972年 | 12篇 |
1971年 | 11篇 |
1970年 | 13篇 |
1969年 | 6篇 |
1968年 | 7篇 |
排序方式: 共有819条查询结果,搜索用时 15 毫秒
111.
M.F. Arrigoni-Blank A.R. Antoniolli L.C. Caetano D.A. Campos A.F. Blank P.B. Alves 《Phytomedicine》2008,15(5):334-339
Hyptis pectinata L. Poit (Lamiaceae) is known popularly in Brazil as “sambacaita” or “canudinho” and is used in the treatment of inflammations, bacterial infections and ache. The antinociceptive activity of the volatile oils of six genotypes, at doses of 100, 200 and 400 mg/kg body wt., were investigated using abdominal writhe models induced by acetic acid and hot plate tests. The volatile oils of all the genotypes are composed mainly of sesquiterpenoids. All the genotypes showed antinociceptive effects in both models used; the SAM002 genotype showed the major inhibitory effect at dose of 100 mg/kg body wt. These results suggest that the volatile oil of H. pectinata has peripheral (writhe reduction) and central (time delay of thermal reaction) effects. These observations indicate that H. pectinata may be useful as an analgesic drug. 相似文献
112.
L.J. Quintans-Júnior T.T. Souza B.S. Leite N.M.N. Lessa L.R. Bonjardim M.R.V. Santos P.B. Alves A.F. Blank A.R. Antoniolli 《Phytomedicine》2008,15(8):619-624
Cymbopogon winterianus (Poaceae) is used for its analgesic, anxiolytic and anticonvulsant properties in Brazilian folk medicine. This report aimed to perform phythochemical screening and to investigate the possible anticonvulsant effects of the essential oil (EO) from fresh leaves of C. winterianus in different models of epilepsy. The phytochemical analysis of EO showed presence of geraniol (40.06%), citronellal (27.44%) and citronellol (10.45%) as the main compounds. A behavioral screening demonstrated that EO (100, 200 and 400 mg/kg; ip) caused depressant activity on CNS. When administered concurrently, EO (200 and 400 mg/kg, ip) significantly reduced the number of animals that exhibited PTZ- and PIC-induced seizures in 50% of the experimental animals (p<0.05). Additionally, EO (100, 200 and 400 mg/kg, ip) significantly increased (p<0.05) the latencies of clonic seizures induced by STR. Our results demonstrated a possible activity anticonvulsant of the EO. 相似文献
113.
Michael H. Figler Grant S. Blank Harman V. S. Peeke 《Marine and Freshwater Behaviour and Physiology》2005,38(4):237-248
The shelter defense dynamics of reproductively active (Form I) male red swamp crayfish Procambarus clarkii (Girard) were investigated by staging serial intrusions by male, maternal or non-maternal female conspecifics after one day of residence. The male residents showed a direct contest advantage only against non-maternal females, and won a significantly higher proportion of the encounters against non-maternal females than against either male or maternal female intruders. However, there was no significant difference in success against male or maternal female intruders. Further experiments against male intruders showed that increasing male prior residence to either 2 or 4 days did not significantly improve the residents' proportion of successful encounters. A final experiment revealed extremely low shelter fidelity in male P. clarkii, the most likely reason why male shelter defense against conspecific males and maternal females is not successful. These results, combined with those of past research, suggest that non-maternal females, juveniles and recently molted conspecifics are most vulnerable to predation and cannibalism, since males and maternal females easily out-compete non-maternal females for shelter, and adults out-compete juveniles. These findings may have implications for P. clarkii aquaculture and general management. 相似文献
114.
Chronic glutamine supplementation increases nasal but not salivary IgA during 9 days of interval training. 总被引:1,自引:0,他引:1
Oral glutamine supplementation during and after exercise abolishes exercise-induced decreases in plasma glutamine concentration but does not affect secretory IgA (sIgA) salivary output. Whether chronic glutamine supplementation during high-intensity interval training influences salivary and nasal sIgA concentration is unknown. The purpose of this study was examine the effects of chronic glutamine supplementation on sIgA during intense running training. Runners (n = 13, body mass 69.9 +/- 2.8 kg, peak whole body oxygen uptake 55.5 +/- 2 ml.kg(-1).min(-1), age 29.1 +/- 2.8 yr) participated in twice-daily interval training for 9-9.5 days, followed by recovery (5-7 days). Oral glutamine supplement (0.1 g/kg) or placebo was given four times daily for the first 14 days. After an overnight fast, venous blood, nasal washes, and stimulated saliva were collected at baseline (T1), midtraining (T2), posttraining (T3), and after recovery (T4). Mood states were assessed by using Profile of Mood States (POMS) inventories. We found that glutamine concentration in resting subjects decreased from T1 to T4 (P < 0.05) and was not altered by supplementation. Salivary IgA concentration and output were unchanged by training or supplementation. Mean nasal IgA across the study period was greater in runners receiving glutamine (264.7 +/- 35.0 microg/mg protein) vs. placebo (172.4 +/- 33.7 microg/mg protein; P < 0.05). POMS analyses indicated that vigor was lower at T3 vs. T1 (P < 0.05) and fatigue was higher at T2 vs. T1 and T4 (P < 0.05). We conclude that chronic glutamine supplementation during interval training results in higher nasal IgA than placebo but does not affect salivary IgA concentration or output. 相似文献
115.
116.
Paloma Rocha Arakaki Paula Andrea Borges Salgado Joo Diego de Agostini Losano Marcel Henrique Blank Marcílio Nichi Ricardo Jos Garcia Pereira 《American journal of primatology》2019,81(8)
The golden‐headed lion tamarin (Leontopithecus chrysomelas) is an endangered species endemic to Brazil's Atlantic Forest, a shrinking biodiversity hotspot. As in other Neotropical primates, its semen characteristics and freezability are poorly studied. Hence, reproductive technologies for callitrichids would greatly benefit from reliable methods of semen analysis. In a bid to promote reproductive research in tamarins, we validated simple and inexpensive sperm function tests that can be used to monitor sperm‐egg binding, plasma membrane and acrosome integrity, mitochondrial activity, and DNA fragmentation. Ejaculates from adult males were individually diluted and divided into control and damage‐induced aliquots, and then samples comprising assorted amounts of damaged spermatozoa were examined by organelle‐specific tests. Our findings showed that sperm‐binding in chicken egg perivitelline membrane (EPM) positively correlated with the number of spermatozoa injured by snap‐freezing. Eosin‐nigrosin (EN) and propidium iodide readings were correlated with each other, and both provided robust measurements of plasma membrane integrity. A high correlation between expected and measured amounts of acrosome‐intact spermatozoa was found using Fast Green‐Rose Bengal (FG‐RB), Coomassie Blue (CB), and FITC‐PSA stains, and all three methods exhibited comparable results. Likewise, different percentages of UV‐irradiated spermatozoa were accurately assessed for DNA integrity by Toluidine Blue (TB) and sperm chromatin dispersion (SCD) tests. Comparisons between 3,3′‐diaminobenzidine (DAB) and JC‐1 stains also indicated the reliability of the former assay to ascertain gradual increases in spermatozoa with greater mitochondrial function. These data confirmed that different parts of the tamarin spermatozoa can be simply and consistently evaluated by EPM, EN, FG‐RB, CB, TB, and DAB protocols. 相似文献
117.
118.
Animals receive anti-predator benefits from social behavior. As part of a group, individuals spend less time being vigilant, and vigilance decreases with increasing group size. This phenomenon, called “the many-eyes effect”, together with the “encounter dilution effect”, is considered among the most important factors determining individual vigilance behavior. However, in addition to group size, other social and environmental factors also influence the degree of vigilance, including disturbance from human activities. In our study, we examined vigilance behavior of Khulans (Equus hemionus) in the Xinjiang Province in western China to test whether and how human disturbance and group size affect vigilance. According to our results, Khulan showed a negative correlation between group size and the percentage time spent vigilant, although this negative correlation depended on the groups’ disturbance level. Khulan in the more disturbed area had a dampened benefit from increases in group size, compared to those in the undisturbed core areas. Provision of continuous areas of high-quality habitat for Khulans will allow them to form larger undisturbed aggregations and to gain foraging benefits through reduced individual vigilance, as well as anti-predator benefits through increased probability of predator detection. 相似文献
119.
120.