全文获取类型
收费全文 | 653篇 |
免费 | 81篇 |
国内免费 | 18篇 |
出版年
2022年 | 5篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 11篇 |
2014年 | 20篇 |
2013年 | 22篇 |
2012年 | 27篇 |
2011年 | 21篇 |
2010年 | 17篇 |
2009年 | 11篇 |
2008年 | 24篇 |
2007年 | 29篇 |
2006年 | 26篇 |
2005年 | 34篇 |
2004年 | 22篇 |
2003年 | 24篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 17篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 19篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 8篇 |
1986年 | 14篇 |
1985年 | 15篇 |
1984年 | 15篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1974年 | 7篇 |
1973年 | 6篇 |
1972年 | 6篇 |
1931年 | 4篇 |
排序方式: 共有752条查询结果,搜索用时 15 毫秒
721.
Crop‐foraging by animals is a leading cause of human–wildlife “conflict” globally, affecting farmers and resulting in the death of many animals in retaliation, including primates. Despite significant research into crop‐foraging by primates, relatively little is understood about the behavior and movements of primates in and around crop fields, largely due to the limitations of traditional observational methods. Crop‐foraging by primates in large‐scale agriculture has also received little attention. We used GPS and accelerometer bio‐loggers, along with environmental data, to gain an understanding of the spatial and temporal patterns of activity for a female in a crop‐foraging baboon group in and around commercial farms in South Africa over one year. Crop fields were avoided for most of the year, suggesting that fields are perceived as a high‐risk habitat. When field visits did occur, this was generally when plant primary productivity was low, suggesting that crops were a “fallback food”. All recorded field visits were at or before 15:00. Activity was significantly higher in crop fields than in the landscape in general, evidence that crop‐foraging is an energetically costly strategy and that fields are perceived as a risky habitat. In contrast, activity was significantly lower within 100 m of the field edge than in the rest of the landscape, suggesting that baboons wait near the field edge to assess risks before crop‐foraging. Together, this understanding of the spatiotemporal dynamics of crop‐foraging can help to inform crop protection strategies and reduce conflict between humans and baboons in South Africa. 相似文献
722.
723.
724.
The isolation of human-erythrocyte band-3 polypeptide labelled with a photosensitive hydrophobic probe. 下载免费PDF全文
To investigate the intramembranous domains of the major band-3 polypeptide, human erythrocyte membranes were labelled with 1-azido-4-[125I]iodobenzene. The anion-exchange protein has been isolated by a new procedure that decreases possible contamination by other integral membrane proteins of similar molecular weight. After chemical modification, the protein was subjected to proteolytic cleavage by several proteinases to yield a distinct pattern of peptides, a few of which contained radioactivity. 相似文献
725.
Drinking was measured by the rate of uptake of tritiated dextran in fresh water by the alevins and fry of rainbow trout at various stages of development during a 40-day post-hatch period. Drinking increased almost S-fold during the initial 16 day yolk-sac stage. Drinking rate increased most between 16 and 23 days, the transitional period between yolk-sac absorption and first feeding. The maximum weight-specific drinkingrateof 3.24μlg−1 h−1 recorded for 40-day-old fry was higher than previously recorded for adults. Abrupt transfer from an adaptation temperature of 10 to 19° C increased drinking significantly (Q10 = 1.2), but sudden transfer to 1 1‰ salinity sea water caused a substantial fall in drinking rate in 23-day fry. A 24-h period of adaptation to 1 1‰ and 15‰ salinity restored drinking to a rate similar to that in fresh water. The water drunk by 31-day fry fed to satiation was initially higher than by unfed fry, but drinking rates subsequently fell below the control level. The results are discussed in terms of osmoregulation and the uptake of dissolved or suspended substances by the intestinal tract for the purpose of immunization. 相似文献
726.
The epidemiology of sporotrichosis in the Transvaal 总被引:1,自引:0,他引:1
G H Findlay 《Sabouraudia》1970,7(4):231-236
727.
728.
Ovulation rate (OR) was studied in two experiments using mature Border Leicester × Merino ewes in which oestrous cycles were synchronized using a prostaglandin analogue. In both experiments a basal ration of 500 g of lucerne/barley pellets was provided. In the first experiment, ewes were fed individually iso-energy supplements of 500 g of either peas, lupins, soybean pellets or lucerne/barley pellets. The ovulation studied at laparoscopy occurred approximately 34 days after starting the supplementary feeding. Ewes fed lupins or soybean pellets had higher (P < 0.05) OR's than the ewes fed the other diets.In the second experiment, ewes were fed either iso-protein supplements of peas or lupins or casein supplement (170 or 100 g of protein) either formalin treated or untreated. The ovulations studied at laparoscopy occurred approximately either 17 or 34 days after the first feeding of the supplement. Follicle stimulating hormone (FSH) levels in plasma were measured over the 8 days prior to the second ovulation. There were no differences (P < 0.05) in OR's at the first ovulation. However, by the second, ewes fed peas had the highest (P < 0.05) OR while those fed lupins or protected casein had similar OR's. These tended to be higher than in the ewes fed untreated casein. FSH levels were generally higher from 8 days to 3 days prior to ovulation in ewes which were to have twin ovulations compared to those having single ovulations.The results confirm that feeding high energy or high protein will increase OR. There are independent effects of energy and protein. The results suggested that the ovulation rate may be related to FSH levels. 相似文献
729.
I Findlay M P Sauviat 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1990,310(11):489-494
The ATP-sensitive K channel opener, SR 44866, was applied to intact extensor digitorum muscle of the mouse. Electrically stimulated maximal twitch contractions of the muscle were decreased by SR 44866 with a KD of 7.4 microM and a Hill coefficient of 1.2 at 34 degrees C. The effect of SR 44866 was antagonized by glibenclamide and reduced at 24 degrees C. We suggest that these results represent the consequence of activation of ATP-sensitive K channels in mammalian skeletal muscle. 相似文献
730.