全文获取类型
收费全文 | 17405篇 |
免费 | 928篇 |
国内免费 | 17篇 |
专业分类
林业 | 855篇 |
农学 | 579篇 |
基础科学 | 123篇 |
2580篇 | |
综合类 | 2670篇 |
农作物 | 954篇 |
水产渔业 | 985篇 |
畜牧兽医 | 8471篇 |
园艺 | 203篇 |
植物保护 | 930篇 |
出版年
2021年 | 164篇 |
2020年 | 173篇 |
2019年 | 206篇 |
2018年 | 333篇 |
2017年 | 376篇 |
2016年 | 270篇 |
2015年 | 212篇 |
2014年 | 341篇 |
2013年 | 682篇 |
2012年 | 519篇 |
2011年 | 656篇 |
2010年 | 446篇 |
2009年 | 427篇 |
2008年 | 647篇 |
2007年 | 572篇 |
2006年 | 535篇 |
2005年 | 465篇 |
2004年 | 435篇 |
2003年 | 444篇 |
2002年 | 383篇 |
2001年 | 493篇 |
2000年 | 479篇 |
1999年 | 378篇 |
1998年 | 181篇 |
1997年 | 201篇 |
1996年 | 156篇 |
1995年 | 192篇 |
1993年 | 164篇 |
1992年 | 282篇 |
1991年 | 313篇 |
1990年 | 307篇 |
1989年 | 313篇 |
1988年 | 289篇 |
1987年 | 246篇 |
1986年 | 296篇 |
1985年 | 253篇 |
1984年 | 209篇 |
1983年 | 208篇 |
1979年 | 250篇 |
1978年 | 165篇 |
1975年 | 171篇 |
1974年 | 235篇 |
1973年 | 215篇 |
1972年 | 252篇 |
1971年 | 230篇 |
1970年 | 204篇 |
1969年 | 192篇 |
1968年 | 158篇 |
1967年 | 160篇 |
1966年 | 161篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
981.
O O Barriga F Andujar 《Journal of the American Veterinary Medical Association》1988,192(12):1743-1744
A dog with chronic dirofilariasis (Dirofilaria immitis) was given 15 doses of 12 or 24 mg of levamisole/kg of body weight in 6 treatments within 96 days. Concentration of microfilariae in the blood was determined before and after treatment, and Aedes triseriatus mosquitoes were fed on the dog 1 to 5 days after each treatment and examined for D immitis larvae. Several adult worms were recovered from the dog 160 days after the end of the treatments. 相似文献
982.
983.
The regrowth of Italian ryegrass following a cut in late April was studied at weekly intervals up to 14 weeks. There were four levels of applied N: 28, 84, 140 and 196 kg ha-1. The proportion of green leaf blade declined from 80% of DM yield after 2 or 3 weeks of regrowth to 5% after 13–14 weeks. About three-quarters of the increase in DM yield of total herbage from week 3 to week 11 was attributable to increased yield of ‘stem’. The level of applied N had little effect on the proportion of crop fractions except during the period immediately before and after the begiiming of ear emergence when the higher rates of N increased the proportion of ‘stem’ and reduced that of green leaf. The most digestible crop fractions were green leaf, inflorescence and immature ‘stem’. D-value of ‘stem’ declined by about 20 units from week 1 to week 14, while D-value of green and dead leaf declined at about half this rate and there was little or no decline in D-value of inflorescence. The N content of green leaf was consistently higher than that of the other fractions. The N content of ‘stem’declined markedly to around 0.5% by week 12. The N content of dead leaf and inflorescence was intermediate between that of green leaf and mature ‘stem’. The N content of all fractions was increased by applying more N. The tiller population increased during the flrst 3 weeks of regrowth and declined during the next 4. Applying more N increased both tiller population and weight per tiller. 相似文献
984.
El-Warrak AO Ferrer GA Lanthier T Loureiro Silva B El-Warrak LO 《The Journal of small animal practice》2011,52(3):158-162
Objective : To determine the effect of unilateral condylectomy on dental occlusion in cats. Methods : Twelve feline cadaver heads were randomly submitted to either a right or left unilateral condylectomy of the temporo‐mandibular joint. The distance between the mandibular and maxillary canine tooth was measured before (B0) and after the unilateral condylectomy (P0). A right or left latero‐‐lateral standardised force (4 N) was applied to the mandibular mentus area before and after the surgical procedure. These measurements were analysed with a linear model for repeated measures. Results : The comparative analysis between pre‐ and postsurgical values indicated no significant variation in teeth displacement following condylectomy between B0 and P0 measurements. Statistically significant differences were detected after either left or right condylectomy with respect to all measurements after application of the standardised forces. Occlusion changes are significant when comparing bites before and after surgery. Clinical Significance : Unilateral condylectomy causes a significant increase in latero‐lateral amplitude of jaw movement which might clinically affect feline dental occlusion. Clinical studies are required to determine the effect of unilateral condylectomies on mastication and dental occlusion in feline patients. 相似文献
985.
Franciosini MP Fringuelli E Tarhuni O Guelfi G Todd D Casagrande Proietti P Falocci N Asdrubali G 《Avian diseases》2005,49(3):340-343
This paper describes a polymerase chain reaction (PCR)-based method performed on blood samples and intestinal content to detect subclinical pigeon circovirus (PiCV) infection in live pigeons. In addition, two sets of primers (primer set 1 and 2), designed in two different regions of the viral genome, were used to provide evidence of possible differences in PCR responses. Blood and intestinal content samples were randomly collected from a total of 50 apparently healthy meat pigeons, aged 1 to 5 wk, which came from central Italy. Samples of primary lymphoid organs were also collected. Results showed a high level of PiCV infection, although clinical signs were not present. The results obtained with the two sets of primers showed that primer set 2 was able to detect a higher number of PCR-positive pigeons (45 of 50 pigeons) than primer set 1 (11 of 50 pigeons). In both cases an increase in positive results with pigeon age indicates that the major direction of transmission is likely horizontal. In these circumstances feces can play an important epidemiologic role, as supported by the consistent circovirus detection in intestinal content. The high sensitivity of this PCR test, which is able to detect very low amounts of viral DNA (5.5 x 10(-3) fg of plasmid containing the cloned PiCV genome), makes it suitable for possible application as an epidemiologic tool for identifying virus carriers for subsequent removal from lofts. 相似文献
986.
E M Aburto A Cribb I C Fuentealba B O Ikede F S Kibenge F Markham 《Canadian journal of veterinary research》2001,65(2):104-110
This study evaluates the ability of selenium (Se) supplementation to prevent experimental copper (Cu)-induced hepatocellular damage. Weanling male Fischer 344 rats were randomly assigned to groups of 15, 3 groups (A,B,C) were fed Cu-loaded diets (containing 2000 microg/g copper, added as CuSO4) and different levels of Se (added as Na2SeO3 x 5H2O) as follows: A) Cu-loaded/Se adequate diet (0.4 microg/g Se, fed basis); B) Cu-loaded/Se-supplemented diet (2 microg/g Se); and C) Cu-loaded/Se-deficient diet (< 0.2 microg/g). Three additional groups (D,E,F) were fed diets containing adequate levels of Cu (14 microg/g Cu, fed basis) and different levels of Se as follows: D) Cu-adequate/Se-adequate diet; E) Cu-adequate/Se-supplemented diet (2 microg/g Se); and F) Cu-adequate/Se-deficient (< 0.2 microg/g) diet. After 4, 8, and 12 weeks on the experimental diets, liver samples were processed for histology, histochemistry, metal analysis, glutathione peroxidase (GSH-Px) measurement, and quantification of malondialdehyde (MDA). Morphologic changes characteristic of Cu-associated hepatitis, without an increase in hepatic MDA levels, were seen in all Cu-loaded rats in each sampling. Similar changes occurred in rats fed Se-adequate, Se-supplemented and Se-deficient diets. This study demonstrates that Fischer 344 rats fed 2000 microg/g Cu develop morphologic changes due to Cu toxicity without evidence of lipid peroxidation. Furthermore, Se supplementation does not result in protection against Cu-induced liver injury. 相似文献
987.
988.
Bulysheva A. M. Khokhlova O. S. Bakunovich N. O. Rusakov A. V. Myakshina T. N. 《Eurasian Soil Science》2021,54(8):1265-1280
Eurasian Soil Science - Changes in the macro-, meso-, and micromorphological properties of plowed migration-mycelial chernozems (Haplic Chernozems) after their conversion into permanent unmanaged... 相似文献
989.
Bovine embryos obtained from donors six to nine days after oestrus were transferred non-surgically at a rate of one per recipient using a sterile insemination instrument, protected from contamination by the vagina with a plastic sheath. The percentage of recipients pregnant increased with the age of embryo transferred and for day 6 and 7 embryos was 33% compared to 58% for day 9 and 8 embryos. This difference approached statistical significance. Bacterial contamination of the instrument on withdrawal after transfer was not related to the success or failure of pregnancy. Maintenance of pregnancy to term and calving appeared to be normal. It is suggested that this method could be used for the routine transfer of eight and nine day embryos. 相似文献
990.