全文获取类型
收费全文 | 8044篇 |
免费 | 578篇 |
国内免费 | 110篇 |
专业分类
林业 | 752篇 |
农学 | 457篇 |
基础科学 | 74篇 |
1647篇 | |
综合类 | 847篇 |
农作物 | 477篇 |
水产渔业 | 769篇 |
畜牧兽医 | 2866篇 |
园艺 | 175篇 |
植物保护 | 668篇 |
出版年
2024年 | 13篇 |
2023年 | 82篇 |
2022年 | 156篇 |
2021年 | 281篇 |
2020年 | 318篇 |
2019年 | 268篇 |
2018年 | 359篇 |
2017年 | 373篇 |
2016年 | 355篇 |
2015年 | 282篇 |
2014年 | 341篇 |
2013年 | 518篇 |
2012年 | 661篇 |
2011年 | 639篇 |
2010年 | 324篇 |
2009年 | 292篇 |
2008年 | 459篇 |
2007年 | 442篇 |
2006年 | 383篇 |
2005年 | 332篇 |
2004年 | 282篇 |
2003年 | 329篇 |
2002年 | 331篇 |
2001年 | 235篇 |
2000年 | 171篇 |
1999年 | 90篇 |
1998年 | 41篇 |
1997年 | 33篇 |
1996年 | 28篇 |
1995年 | 25篇 |
1994年 | 22篇 |
1993年 | 19篇 |
1992年 | 19篇 |
1991年 | 10篇 |
1990年 | 15篇 |
1989年 | 23篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1985年 | 9篇 |
1984年 | 13篇 |
1983年 | 13篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 5篇 |
1976年 | 7篇 |
1974年 | 5篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 8篇 |
1968年 | 6篇 |
排序方式: 共有8732条查询结果,搜索用时 15 毫秒
41.
OBJECTIVE: To evaluate a technique for preservation of organoleptic tissue characteristics (color, odor, texture, and flexibility) in cadavers used for surgical instruction. STUDY DESIGN: Experimental study. ANIMALS: Forty-three canine cadavers. METHODS: Cadavers were preserved with a modified Larssen solution of the Hospital Cochim, Paris and cryopreservation. Tissue handling qualities were evaluated in surgical laboratory sessions. RESULTS: All cadavers kept texture and tissues consistency, especially skin and muscle, similar to those of live animals. Some skin desquamation and pallor of the mucous membranes occurred with repetitive freeze-thaw cycles. CONCLUSIONS: This preservation technique provides acceptable cadaver quality and tissue handling for use in surgical instruction. CLINICAL RELEVANCE: Preparation of patient cadavers by intravascular injection of modified Larssen solution yielded suitable instructional models for surgical training. 相似文献
42.
Taciana P. Spinelli Edmilson F. Oliveira‐Filho Davi Silva Rinaldo Mota F. B. Sá 《Veterinary ophthalmology》2010,13(Z1):134-136
Objective To determine the normal aerobic bacterial conjunctival population of the Coatis and the Crab‐eating raccoons housed in captivity in the Pernambuco and Paraiba states of Brazil. Animals studied Ten healthy Coatis and 10 healthy Crab‐eating raccoons were selected for this study. Animals are from three zoos situated at the Pernambuco and Paraiba States in the north‐east of Brazil. Procedures After ophthalmologic examination, swabs from healthy animals were carefully collected in order to avoid contamination. Samples were identified and submitted to the laboratory. Swabs were plated for culture on ovine blood agar (8%) and agar Levine and incubated at 37 °C and observed 24 and 48 h. Results Staphylococcus spp. was the most common microorganism isolated from conjunctival sac. Shigella spp. comprised the Gram‐negative genera isolated. Escherichia coli were isolated from the right eye of one Coati that had no growth at contralateral eye. Nine eyes from coatis and 10 from Crab‐eating raccoons had no microorganisms isolated. Conclusion Our results were in accordance with previous studies indicating Staphylococcus sp., followed by Corynebacterium spp. as the most common inhabitant of the eyes of most mammalian species. 相似文献
43.
44.
Hanley CS MacWilliams P Giles S Paré J 《The Canadian veterinary journal. La revue veterinaire canadienne》2006,47(10):1015-1017
A domestic ferret was presented for episodic regurgitation. Cytologic examination and culture of an enlarged submandibular lymph node revealed Cryptococcus neoformans variety grubii (serotype A). The ferret was successfully treated with itraconazole. This is the first documented case of Cryptococcus neoformans variety grubii in a ferret in the United States. 相似文献
45.
del Río ML Navas J Martín AJ Gutiérrez CB Rodríguez-Barbosa JI Rodríguez Ferri EF 《Veterinary research》2006,37(1):49-59
Bacteria have evolved a set of highly specialized proteins to capture iron in iron-depleted environments. The acquisition and uptake of iron present in the extracellular milieu of eukaryotic organisms is indispensable for the growth and survival of microbial pathogens in the course of infection. Haemophilus parasuis is the causative agent of Gl?sser disease, which is responsible for considerable financial losses in pig-rearing worldwide. To gain insight into the mechanisms involved in siderophore-mediated iron uptake in H. parasuis, genes in the H. parasuis ferric hydroxamate uptake (Fhu) region were amplified in the work being reported here. As has been described in A. pleuropneumoniae, an Fhu genomic region was also present in H. parasuis, being composed of four potential consecutive open reading frames (ORF) designated as fhuC, fhuD, fhuB, and fhuA, respectively. By immunoblotting, using a cross-reactive polyclonal antibody raised against Actinobacillus pleuropneumoniae FhuA protein, it was demonstrated that this protein was constitutively expressed in H. parasuis and its level of expression was not modified under conditions of restricted iron availability. This is the first report describing the presence of the fhu genes in H. parasuis. Our results indicate that FhuA protein expression is not affected under iron-restricted conditions, however, it is one of the targets of the humoral immune response. 相似文献
46.
Bussières G Jacques C Lainay O Beauchamp G Leblond A Cadoré JL Desmaizières LM Cuvelliez SG Troncy E 《Research in veterinary science》2008,85(2):294-306
This study addresses development and validation of a composite multifactorial pain scale (CPS) in an experimental equine model of acute orthopaedic pain. Eighteen horses were allocated to control (sedation with/without epidural analgesia - mixture of morphine, ropivacaine, detomidine and ketamine) and experimental groups: amphotericin-B injection in the tarsocrural joint induced pain and analgesia was either i.v. phenylbutazone administered post-induction of synovitis, or pre-emptive epidural mixture, or a pre-emptive combination of the 2. Inter- and intra-observer reproducibility was good (0.8相似文献
47.
48.
49.
Canola PA Perotta JH Laskoski LM Escobar A Melo e Silva CA Canola JC Johnson PJ Valadão CA 《Equine veterinary journal》2011,43(4):446-450
Reasons for performing study: Standing surgical procedures are being employed to an ever‐greater extent in horses. Pneumoperitoneum during abdominal surgery might adversely affect the work of breathing. Objectives: To determine whether development of pneumoperitoneum during abdominal surgery adversely influences the work of breathing. Methods: Eight healthy mature horses were equipped with carotid artery and thoracic vena cava catheters and an intraluminal manometry system. The following measurements were obtained before and at +5, +10, +15 and +30 min following establishment of pneumoperitoneum by paralumbar puncture using an 8 gauge needle: vital signs, oesophageal pressure, gastric pressure, arterial and central venous blood pressures, and arterial and mixed venous blood gas analyses. Results: Significant changes in oesophageal pressure, central venous pressure and results of arterial and mixed venous blood gas analysis were not detected. Arterial diastolic and mean pressures and rectal temperature increased slightly (P≤0.05). Conclusions: Passive pneumoperitoneum did not adversely affect breathing mechanics or haemodynamic variables under experimental conditions. Changes in arterial pressure could have occurred as a response to the passive pneumoperitoneum or be related to handling stress. Subtle variations in rectal temperature were not clinically relevant and likely resulted from stress associated with restraint. Potential relevance: It is unlikely that mature horses will develop signs of respiratory difficulty as a result of the development of passive pneumoperitoneum during standing laparoscopy. 相似文献
50.
The combined occurrence of ocular pigment deposition and glaucoma has been described in Cairn Terriers. Recently, this condition was also observed in two other breeds: the Boxer (two cases) and the Labrador Retriever (one case). Six dogs were referred to the Ophthalmology section of the Department of Clinical Sciences of Companion Animals and to a private referral clinic because of glaucoma or blindness in one or both eyes. In five cases ophthalmic examination showed pigment depositions in the sclera around the entire circumference of the perilimbal zone. Eight enucleated eyes (four eyes of two Cairn Terriers, three eyes of two Boxers and one eye of a Labrador Retriever) were examined microscopically. All eyes showed the same findings: an extensive infiltration of large melanin-containing cells with an eccentric nucleus, located in the iris, ciliary body, retina, choroids and sclera. Transmission electron microscopy of two of the examined eyes revealed that the morphology of most of these cells was consistent with melanophages. While reports in the veterinary literature concerning this condition are limited the cells concerned have been described to be melanocytes. Further research is needed to conclusively identify the cell type. As described in the present report, the histologic and transmission electron microscopic findings suggest a different etiology of the ocular pigment deposition and glaucoma compared with the pigment dispersal syndrome in humans. 相似文献