全文获取类型
收费全文 | 1377篇 |
免费 | 60篇 |
国内免费 | 5篇 |
专业分类
林业 | 126篇 |
农学 | 35篇 |
180篇 | |
综合类 | 74篇 |
农作物 | 48篇 |
水产渔业 | 201篇 |
畜牧兽医 | 682篇 |
园艺 | 11篇 |
植物保护 | 85篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 40篇 |
2020年 | 24篇 |
2019年 | 27篇 |
2018年 | 31篇 |
2017年 | 32篇 |
2016年 | 51篇 |
2015年 | 33篇 |
2014年 | 40篇 |
2013年 | 81篇 |
2012年 | 65篇 |
2011年 | 75篇 |
2010年 | 36篇 |
2009年 | 43篇 |
2008年 | 81篇 |
2007年 | 71篇 |
2006年 | 65篇 |
2005年 | 63篇 |
2004年 | 60篇 |
2003年 | 67篇 |
2002年 | 47篇 |
2001年 | 66篇 |
2000年 | 57篇 |
1999年 | 37篇 |
1998年 | 12篇 |
1997年 | 4篇 |
1996年 | 10篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 22篇 |
1989年 | 20篇 |
1988年 | 10篇 |
1987年 | 18篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1965年 | 4篇 |
排序方式: 共有1442条查询结果,搜索用时 265 毫秒
91.
The influence of dietary fat level and whole‐body adiposity on voluntary energy intake of juvenile rainbow trout Oncorhynchus mykiss (Walbaum) was examined using self‐feeders. Groups of lean fish [crude fat (CF) = 7%] and fat fish (CF = 11%), pretreated with a commercial diet with or without supplemental pollock oil, were self‐fed one of three fat level diets (CF = 8%, 13.5% and 19%) for 48 days at 17 °C. Final body weight (BW) and total digestible energy (DE) intake (kJ per fish) were positively affected by the initial BW. Relative to the initial BW, however, fat fish consumed less DE than lean fish. Although the effect of dietary fat level was not significant, percentage weight gain and daily DE intake per BW (kJ kg?1 BW day?1) of fat fish were significantly lower than those of lean fish (ancova with initial BW as a covariate, P < 0.05). Energy digestibility, feed efficiency and protein retention were improved with the dietary fat level; however, there was no difference resulting from body fat level. The whole‐body fat levels at the end of the experiment increased with the dietary fat level. Between groups self‐fed the same diet, fat levels of the initially fat fish were still higher than those of the lean fish. The results of the present medium‐term study suggest that rainbow trout adjust DE intake from diets with fat levels ranging from 8% to 19%. Although body fat level affects neither energy digestibility nor protein utilization, a high body fat level may reduce DE intake and consequently depress growth. 相似文献
92.
The duality of teleost gonadotropins 总被引:5,自引:0,他引:5
Hiroshi Kawauchi Kunimasa Suzuki Hiromichi Itoh Penny Swanson Nobuko Naito Yoshitaka Nagahama Masumi Nozaki Yasumitu Nakai Seiga Itoh 《Fish physiology and biochemistry》1989,7(1-6):29-38
The duality of salmon gonadotropins has been proved by biochemical, biological, and immunological characterization of two
chemically distinc gonadotropins. GTH I and GTH II were equipotent in stimulating estradiol production, whereas GTH II appears
to be more potent in stimulating maturational steroid synthesis. The ratio of plasma levels and pituitary contents of GTHs
and the secretory control by a GnRH suggest that GTH I is the predominant GTH during vitellogenesis and early stages of spermatogenesis
in salmonids, whereas GTH II is predominant at the time of spermiation and ovulation. GTH I and GTH II are found in distinctly
separate cells. In trout, GTH I is expressed first in ontogeny, whereas GTH II cells appear coincident with the onset of spermatogenesis
and vitellogenesis, and increase dramatically at the time of final reproductive maturation. Comparison of the amino acid sequences
of polypeptides and the base sequences of cDNA revealed that salmon GTH I β is more similar to bovine FSHβ than bovine LHβ
and salmon GTH II β shows higher homology to bovine LHβ than to bovine FSHβ. The existence of two pituitary gonadotropins
in teleosts as well as tetrapods suggests that the divergence of the GTH gene took place earlier than the time of divergence
of teleosts from the main line of evolution leading to tetrapods. 相似文献
93.
94.
K. Nakamura T. Osuga K. Morishita S. Suzuki T. Morita N. Yokoyama H. Ohta M. Yamasaki M. Takiguchi 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2014,28(6):1746-1752
Background
A strong correlation between left atrial (LA) dysfunction and the severity of cardiac disease has been described in human patients with various cardiac diseases. The role of LA dysfunction in dogs with chronic mitral valvular heart disease (CMVHD) has not been addressed.Objectives
To investigate the correlation between LA function and the prognosis of dogs with CMVHD.Animals
Thirty‐eight client‐owned dogs with CMVHD.Methods
Prospective clinical cohort study. Dogs were divided into 2 groups (survivors and nonsurvivors) based on the onset of cardiac‐related death within 1 year. Physical examination and echocardiographic variables were compared between the groups. For the assessment of the comparative accuracy in identifying patients with cardiac‐related death, receiver operating characteristic (ROC) curves and multivariate logistic analysis were used.Results
The highest accuracy was obtained for the LA active fractional area change (LA‐FAC act), with an area under the ROC curve (AUC) of 0.95, followed by the left atrial to aortic root ratio (LA/Ao), with an AUC of 0.94; peak early diastolic mitral inflow velocity (E), with an AUC of 0.85; and LA total fractional area change (LA‐FAC total), with an AUC of 0.85. In the multivariate logistic regression analysis, LA‐FAC act emerged as the only independent correlate of cardiac‐related death within 1 year (odds ratio = 1.401, P = .002).Conclusions and Clinical Importance
Regarding both the size and function, the LA has a strong correlation with the prognosis of dogs with CMVHD. The most significant independent predictor of mortality in this study was LA‐FAC act. 相似文献95.
In this study, the expressions of VEGF in dog follicles were detected by immunohistochemistry and the effects of VEGF treatment on the primordial to primary follicle transition and on subsequent follicle progression were examined using a dog ovary organ culture system. The frozen‐thawed canine ovarian follicles within slices of ovarian cortical tissue were cultured for 7 and 14 days in presence or absence of VEGF. After culture, the ovaries were fixed, sectioned, stained and counted for morphologic analysis. The results showed that VEGF was expressed in the theca cells of antral follicles and in the granulosa cells nearest the oocyte in preantral follicle but not in granulosa cells of primordial and primary follicles; however, the VEGF protein was expressed in CL. After in vitro culture, VEGF caused a decrease in the number of primordial follicles and concomitant increase in the number of primary follicles that showed growth initiation and reached the secondary and preantral stages of development after 7 and 14 days. Follicular viability was also improved in the presence of VEGF after 7 and 14 days in culture. In conclusion, treatment with VEGF was found to promote the activation of primordial follicle development that could provide an alternative approach to stimulate early follicle development in dogs. 相似文献
96.
In northern Europe and America, the acidification of lakes and rivers induced by acid precipitation has damaged fish populations. At present, rapidly expanding industrial activities in East Asia have led to continuous increases in the quantity of emission of acidic pollutants, and rain of acidic levels of pH4 has precipitated throughout Japan. In this way, the effects of acid rain on fish populations have also been manifested in Japan. In order to examine the effects of low pH on the reproductive behavior of salmonids which are known to be acid-sensitive species, changes in the frequency of upstream behavior and spawning-related female nest-digging behavior in response to changes in pH were observed in mature hime salmon (land-locked sockeye salmon) Oncorhynchus nerka, brown trout Salmo trutta and Japanese char Salvelinus leucomaenis. Digging and upstream behavior were significantly inhibited in weakly acidic water of pH 5.8–6.4 formulated using sulfuric acid. Land-locked sockeye salmon was the most sensitive to changes in pH among the three species. 相似文献
97.
98.
Manami Inaba Takeshi Kimura Rika Kikukawa Mitsuko Iwasaki Masato Nose Satoru Suzuki 《Fisheries Science》2007,73(3):615-622
ABSTRACT: Seasonal changes in the infection state of marine birnavirus (MABV) in Japanese flounder Paralichthys olivaceus and in rearing sea water are described. Sea water and 10–11 healthy fish were sampled monthly from April 2002 to February 2003. The MABV genome was detected throughout the year in > 80% of the fish examined at each sampling. The virus was isolated from the liver, kidney, and spleen, but not from the brain. The detection rate in each organ increased from April to October, and then decreased. Detection of virus antigen by the indirect fluorescent antibody technique also showed that the virus was present from spring to autumn (June–September) in the liver, kidney, and spleen, but not the brain. Sequence analysis of the MABV genome at the VP2–NS region revealed two specific mutations compared to the standard yellowtail strain (Y-6). It is suggested that the infection state of MABV in Japanese flounder changes to a latent or persistent infection after autumn. MABV was detected in sea water between September and February, suggesting that virus particles in the environment are relatively higher during cool seasons. 相似文献
99.
Accumulation of organotin compounds and marine birnavirus detection in Korean ascidians 总被引:1,自引:0,他引:1
Kaoru Azumi Shinji Nakamura Shin-Ichi Kitamura Sung-Ju Jung Keisuke Kanehira Hisato Iwata Shinsuke Tanabe Satoru Suzuki 《Fisheries Science》2007,73(2):263-269
ABSTRACT: Recently, a serious disease spread extensively in aquaculture sites of the ascidian Halocynthia roretzi in Korea. To understand circumstances of ascidians in Korean aquaculture sites, residue levels of organotin compounds were analyzed, and detection of a marine birnavirus (MABV) in tissues of H. roretzi was attempted. Korean H. roretzi showed high concentrations of butyltins (mono, di, and tributyltins), especially in the gill, hepatopancreas, and digestive tract. However, there was no significant difference in the residues of butyltins in the hepatopancreas between diseased and non-diseased ascidians. The positive rate of MABV detection was high in the hepatopancreas, but also no significant difference was observed between diseased and non-diseased individuals. These observations suggest that an accumulation of tributyltin and a latency of MABV in H. roretzi tissues does not directly relate to the occurrence of the disease. 相似文献