全文获取类型
收费全文 | 1108篇 |
免费 | 70篇 |
国内免费 | 1篇 |
专业分类
林业 | 120篇 |
农学 | 24篇 |
基础科学 | 2篇 |
186篇 | |
综合类 | 136篇 |
农作物 | 42篇 |
水产渔业 | 50篇 |
畜牧兽医 | 552篇 |
园艺 | 11篇 |
植物保护 | 56篇 |
出版年
2021年 | 14篇 |
2020年 | 22篇 |
2019年 | 15篇 |
2018年 | 23篇 |
2017年 | 22篇 |
2016年 | 31篇 |
2015年 | 17篇 |
2014年 | 14篇 |
2013年 | 43篇 |
2012年 | 35篇 |
2011年 | 35篇 |
2010年 | 32篇 |
2009年 | 34篇 |
2008年 | 44篇 |
2007年 | 42篇 |
2006年 | 39篇 |
2005年 | 35篇 |
2004年 | 41篇 |
2003年 | 41篇 |
2002年 | 21篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 25篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1992年 | 19篇 |
1991年 | 30篇 |
1990年 | 15篇 |
1989年 | 30篇 |
1988年 | 10篇 |
1987年 | 21篇 |
1986年 | 22篇 |
1985年 | 20篇 |
1984年 | 12篇 |
1982年 | 9篇 |
1980年 | 9篇 |
1979年 | 15篇 |
1978年 | 13篇 |
1976年 | 9篇 |
1974年 | 15篇 |
1973年 | 11篇 |
1972年 | 14篇 |
1970年 | 20篇 |
1969年 | 11篇 |
1968年 | 14篇 |
1967年 | 21篇 |
1966年 | 9篇 |
排序方式: 共有1179条查询结果,搜索用时 484 毫秒
1.
Ovarian follicular dynamics and embryo yield were studied during 2 different FSH regimens for superovulation of cattle. Twenty heifers were given intramuscular injections of FSH (total of 35 mg NIH) either once daily for 3 days (Group 3×1) or twice daily for 4 days (Group 4×2). At 72 h after the first FSH injection, each animal was injected with 0.75 mg cloprostenol. Inseminations were performed at 12 h and 24 h after the onset of heat. Transrectal ultrasonography was performed on the day of the first FSH injection, the day of cloprostenol injection, the day of insemination and finally on the day of embryo recovery (day 6 or 7 after heat). The numbers of small (2–4 mm), medium (5–9 mm) and large (>10 mm) size follicles were recorded. The total number of corpora lutea, eggs and transferable embryos were recorded on the day of embryo recovery. No differences were found between the 2 groups in either of the parameters studied (p>0.05). It can be concluded that treatment with this FSH preparation once daily for 3 days gives a folliculogenic and superovulatory response similar to a treatment regimen where it is given twice daily for 4 days. 相似文献
2.
AM Mwanza A Madej H Kindahl N Lundeheim & S Einarsson 《Reproduction in domestic animals》2001,36(3-4):157-161
The effects of lipopolysaccharide ( Escherichia coli , O55:B5), administered 18 h after ovulation in the second oestrus after weaning on the hormonal profiles in 14 Swedish cross-bred (Landrace × Yorkshire) multiparous sows were studied. The endotoxin group (E-group) sows were administered with 300 ng/kg of lipopolysaccharide (LPS) whereas the control group (C-group) sows were administered 5 ml of saline intravenously via an indwelling jugular cannula. Blood samples for hormonal analyses were collected from all sows until slaughter. In the E-group, progesterone, cortisol and prostaglandin F2α metabolite levels increased significantly (p < 0.05) following LPS compared with the C-group. It can be concluded from this study that apart from elevating cortisol and prostaglandin F2α metabolite, LPS also elevates progesterone levels. 相似文献
3.
Regulation of Capacitation of Canine Spermatozoa during Co-culture with Heterologous Oviductal Epithelial Cells 总被引:2,自引:0,他引:2
AM Petrunkina K Simon A-R Günzel-Apel E Töpfer-Petersen 《Reproduction in domestic animals》2003,38(6):455-463
Progress of essential steps of the capacitation is coordinated in the oviductal isthmus, where sperm are stored in close contact with the epithelium. A crucial capacitational event is the phosphorylation of sperm membrane proteins. Regulation of the tyrosine phosphorylation by the oviduct has not been examined in dog sperm yet. The aim of this work was to study the effect of dog sperm binding to porcine oviductal epithelium on capacitation‐induced cellular and molecular changes. Epithelial cells were stripped from the oviducts of post‐puberal sows and cultured for 5–7 days at 39°C and 5% CO2 on Biomatrix‐covered Chamber slides. Sperm washed through Percoll was co‐incubated with the oviductal epithelium cell cultures in a bicarbonate Tyrode's medium. During co‐incubation, sperm membrane changes, the state of tyrosine phosphorylation and motility were determined after 3, 30, 90, 180, 240 and 360 min. Significant increases in the percentage of capacitated and dead cells were observed in unbound sperm, while bound sperm remained uncapacitated, live and motile. An increasing tyrosine phosphorylation of tail proteins in bound, unbound and control sperm suspensions and a subsequent phosphorylation of head proteins in unbound and control sperm suspensions were observed. A significant difference regarding head phosphorylation (p < 0.05) was found between sperm bound to oviductal epithelium and unbound sperm. Binding occurred mainly in sperm with non‐ phosphorylated heads, while higher proportions of phosphorylated cells were found in unbound populations. The head phosphorylation progressed significantly during incubation in unbound spermatozoa (p < 0.05); however, it was suppressed in population of sperm attached to oviductal epithelium. Significant correlations between motility parameters related to hyperactivation and tail phosphorylation were found in unbound sperm. These observations support the hypothesis that spermatozoa with non‐phosphorylated heads preferentially attach to epithelial cells. It can be concluded that tyrosine phosphorylation of head membrane proteins and capacitation are delayed in canine spermatozoa being in closed contact with oviductal epithelium. 相似文献
4.
Sugar beet mash silage (BMS) was offered in amounts up to 35% of DM to dairy cows as a component of a total-mixed-ration (TMR). Barley and molasses in the control ration were replaced by BMS half in ration BMS 1/2 and in total in ration BMS 1/1 on the basis of the calculated contents of net energy for lactation. Two trials were carried out. In trial I each ration was tested on parameters of rumen fermentation and digestibility of crude nutrients using 4 Holstein cows with rumen fistula. Chewing activity was tested on 2 Holstein cows for each ration. With the BMS rations the ruminal NH3 concentration was lower and the drop in pH was less than in the control ration. The pattern of volatile fatty acids in the rumen fluid from the BMS groups tended towards more propionic and butyric acid. The feeding of BMS showed no negative impact on chewing and rumination. Energy digestibility raised significantly from 59.8% in the control ration to 72.6% in the BMS 1/1 ration. In trial II the same rations were fed in a change-overdesign to a herd of 24 Holstein cows to test feed intake and animal performance. The results showed no significant effects of BMS rations on DM intake and milk production. The results of both trials indicate that even high amounts of cereals can be replaced by BMS without negative effects on rumen fermentation, milk yield and milk composition with slight drop in fat content. For a better handling of BMS, it is of advantage to include it in a TMR. 相似文献
5.
6.
The effects of sufficient milk intake as well as of 32 hours of fasting after birth, administration of actinomycin D (intraperitoneal application of 1 mg/kg five weight), and fasting in combination with actinomycin D on the development of body and liver weights, crude protein levels in homogenate and supernatant of liver, kidneys, and M. semitendinosus as well as on the activities of certain tissue enzymes were analysed with four groups of piglets (n = 4). Fasting, administration of actinomycin, and fasting in combination with actinomycin D resulted in rapid reduction in body and liver weights, while the crude protein levels in those tissues were not affected with significance. GOT and fructose-1,6-diphosphatase activities in supernatant from liver tended to decline under fasting conditions. The ATPase activity in the homogenate of the above tissues did not change in response to differentiated treatment. 相似文献
7.
8.
9.
Studies were performed on 25 egg batches ofThaumetopoea pityocampa (Den. & Schiff.) collected onPinus pinaster Ait. on 29. XI. 1995, in the Atlas Mountains of Morocco near Marrakech at 1400-1800 m above sea level. All the egg masses
had been deposited in the autumn of 1995 and were exposed to the parasitoids throughout the developmental period of the host.
In 1996, the egg batches, kept singly in test tubes, were observed almost daily. Emerged parasitoids were recorded and separated.
The final analyses were made in November 1996 based on the meconia and remains of the emerged or the dead parasitoids in the
eggs. In all cases, oviposition occurred from the base to the tip of the needles, distances varying up to 62 mm from the base.
The mean number of eggs per batch was 175 (range 34-245), the number of egg-rows varied between 6 and 11, and a 1-cm egg-row
contained a mean of 9 eggs. Caterpillars hatched from 72. 7% of the eggs; total mortality of the eggs was thus 27. 3%. The
impact of egg parasitoids was 21. 4%. Most of the parasitized eggs were attacked byBaryscapus servadeii (Dom.) followed byOoencyrtus pityocampae (Mercet). Males (1. 5%) were found only in B. servadeii. The emergence rate ofO. pityocampae was much higher in the year of host oviposition than in the following year. B. servadeii emerged in equal numbers before
and after hibernation, and in the subsequent year in equal numbers in spring and autumn. The high rate of emergence ofB. servadeii in April-May is discussed in relation to the embryonic development ofThaumetopoea bonjeani (Powel) until the end of winter, as an alternative host ofB. servadeii in the Atlas region. 相似文献
10.
S. Gilbert V. K. Affolter P. Schmidt S. Kosten P. M. Kramme T. L. Gross P. Ihrke P. F. Moore 《Veterinary dermatology》2004,15(Z1):24-24
A previous study described cutaneous lymphocytosis (CL) in 23 cats. The process resembles cutaneous pseudolymphoma in humans, a heterogeneous group of benign reactive proliferations of well‐differentiated lymphocytes in the skin of humans. Morphological and immunophenotypic characteristics do not offer reliable criteria to accurately predict the clinical outcome of feline CL or pseudolymphoma in humans. Presence of clonal cell populations is more consistent with a neoplastic process. In a previous study, feline CL lesions (20 cats) were evaluated for clonality using PCR, and only two cats had monoclonal T‐cell populations. Because false‐negative results may occur, the purpose of this study was to repeat the PCR using a revised primer set based on analysis of additional feline T‐cell receptor γ (TCRγ) sequences. DNA was isolated from 29 skin lesions and six internal organs of 20 cats. DNA integrity was assessed by glyceraldehyde‐3‐phosphate dehydrogenase PCR. Polymerase chain reaction clonality was performed using the revised primer set specific for feline TCRγ, and duplicate samples were evaluated. The PCR products were assessed by heteroduplex analysis. Clonal rearrangement of TCRγ was detected in 14 cats (24 of 35 tissues: 21 of 29 skin lesions and three of six internal organs); eight of these cats are still alive and six were euthanized. Monoclonal populations were seen in three of five cats that had involvement of internal organs. These findings indicate that feline CL is best considered as a slowly progressive process which may be reactive, but often evolves into a low‐grade indolent lymphoma. Funding: George H. Muller Fund for Research in Dermatology. 相似文献