全文获取类型
收费全文 | 10845篇 |
免费 | 689篇 |
国内免费 | 50篇 |
专业分类
林业 | 722篇 |
农学 | 499篇 |
基础科学 | 89篇 |
2144篇 | |
综合类 | 706篇 |
农作物 | 546篇 |
水产渔业 | 814篇 |
畜牧兽医 | 4884篇 |
园艺 | 168篇 |
植物保护 | 1012篇 |
出版年
2023年 | 105篇 |
2022年 | 189篇 |
2021年 | 327篇 |
2020年 | 357篇 |
2019年 | 401篇 |
2018年 | 371篇 |
2017年 | 398篇 |
2016年 | 396篇 |
2015年 | 293篇 |
2014年 | 414篇 |
2013年 | 650篇 |
2012年 | 636篇 |
2011年 | 734篇 |
2010年 | 374篇 |
2009年 | 408篇 |
2008年 | 568篇 |
2007年 | 567篇 |
2006年 | 493篇 |
2005年 | 446篇 |
2004年 | 418篇 |
2003年 | 359篇 |
2002年 | 407篇 |
2001年 | 266篇 |
2000年 | 264篇 |
1999年 | 222篇 |
1998年 | 68篇 |
1997年 | 75篇 |
1996年 | 65篇 |
1995年 | 54篇 |
1994年 | 52篇 |
1993年 | 44篇 |
1992年 | 86篇 |
1991年 | 60篇 |
1990年 | 69篇 |
1989年 | 73篇 |
1988年 | 69篇 |
1987年 | 56篇 |
1986年 | 48篇 |
1985年 | 59篇 |
1984年 | 41篇 |
1983年 | 43篇 |
1982年 | 32篇 |
1980年 | 26篇 |
1979年 | 38篇 |
1978年 | 21篇 |
1977年 | 21篇 |
1974年 | 23篇 |
1973年 | 25篇 |
1972年 | 24篇 |
1970年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Mutinelli F Vercelli A Carminato A Luchesa L Pasolli C Cova M Marchioro W Melchiotti E Vascellari M 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2012,74(4):527-529
A free-living European red deer calf (Cervus elaphus) was euthanized due to bilateral microphthalmia. Lens was missing, replaced by proliferating squamous epithelial cells; hyperplastic squamous cells, sebaceous and mucinous glands were observed within the cornea with the characteristics of inclusion cyst. Findings were consistent with congenital microphthalmia/aphakia, with multiple eye abnormalities. 相似文献
993.
de Bakker E Saunders J Gielen I van Bree H Coppieters E Van Ryssen B 《Veterinary and comparative orthopaedics and traumatology》2012,25(5):359-365
Objectives: To determine the frequency and radiographic aspect of medial humeral epicondylar lesions as a primary or concomitant finding and to evaluate the association with osteoarthritis. Methods: Medical records of dogs diagnosed with elbow lameness were reviewed. Inclusion criteria for this study were a complete clinical examination, a complete set of digital radiographs and a final diagnosis made by computed tomography or magnetic resonance imaging and arthroscopy. Changes of the medial humeral epicondyle were recorded and correlated with the radiographic osteoarthritis and final diagnosis. Results: Eighty of the 200 elbows showed changes of the medial humeral epicondyle. In 12 of these 80 elbows, changes of the medial epicondyle were the only findings within the joint, and these elbows were diagnosed with primary flexor enthesopathy. In the remaining 68 elbows, other concomitant elbow pathologies were found. In those cases of concomitant epicondylar changes, high grades of osteoarthritis were recorded, while most elbows with primary flexor enthesopathy showed a low grade of osteoarthritis. Clinical significance: Changes of the medial humeral epicondyle are often considered clinically unimportant and are regarded as an expression of osteoarthritis. This study showed the relatively frequent presence of epicondylar changes of which the majority were considered concomitant to a primary elbow problem. If changes of the medial humeral epicondyle are the only pathologic finding (primary flexor enthesopathy) they should be considered as the cause of lameness and not as a sign of osteoarthritis. 相似文献
994.
Favaron PO Rodrigues MN Oliveira MF Biasi CM Miglino MA 《Anatomia, histologia, embryologia》2012,41(4):286-299
Oligoryzomys (Cricetidae, Sigmodontinae) is a common rodent genus from South America that includes a couple of very similar species. Related species have been used as experimental model for understanding several diseases for which these species are reservoirs. In order to provide a better understanding of the embryological aspects of this group, herein we showed data on the embryonic and fetal development in Oligoryzomys sp. Eight specimens of different stages of gestation were obtained from the Collection of the Zoology Museum of University of Sao Paulo, Brazil. Gestational ages were estimated by crown-rump-length according to Evans and Sack (1973). To address our analysis after examining the gross morphology, tissues from several organs were processed for light and scanning electron microscopy. Morphological data on the systems (nervous system, cardiorespiratory system, intestinal tract and urogenital system) were described in detail. Finally, the findings were compared with what is known about embryological aspects in other rodent species in order to establish similarities and differences during the organogenesis in different species. 相似文献
995.
Armelle de Laforcade 《Topics in companion animal medicine》2012,27(2):59-64
Coagulation abnormalities are commonly encountered in critical illness. Traditionally, clinically relevant coagulation disorders have consisted mostly of bleeding associated with advanced stages of disseminated intravascular coagulation or toxin ingestion. However, advances in critical care have highlighted hypercoagulability as a clinically relevant state that must be recognized and treated to optimize the chances of a positive outcome. Retrospective studies of dogs with confirmed thrombosis in varying locations have identified populations most likely to experience hypercoagulable states. Diseases most frequently complicated by thrombosis include immune-mediated disease, neoplasia, systemic inflammation and sepsis, cardiac disease, protein-losing states, and infectious diseases. In this report, the existing retrospective studies will be discussed along with a review of specific disease processes that predispose to a hypercoagulable state. Studies targeting those populations most at risk for thrombotic complications are necessary for better understanding the need for prophylactic anticoagulant therapy. 相似文献
996.
The aim of this work was to establish the prevalence of methicillin-resistant Staphylococci (MRS) in the animals and staff of a teaching and research farm. Samples of dairy cattle (36), beef cattle (26), sheep (19), horses (21), pigs (23), goats (23) and humans (13) were collected and screened for the presence of MRS. The detection of mecA gene was performed by PCR to determine the resistance of the samples to methicillin. Antimicrobial-resistance testing to penicillin, meropenem, ceftriaxone, cephalothin, oxacillin, levofloxacin, enrofloxacin, chloramphenicol, ciprofloxacin, gentamicin, clindamycin, erytromycin, linezolid, sulfamethoxazole/trimethoprim, tetracycline, doxycycline and vancomycin was performed on the mecA+ isolates. From the 161 samples, four methicillin-resistant coagulase-negative Staphylococci (MRCoNS) were isolated from human beings (31%), whereas none was isolated from animals (0%). No methicillin-resistant Staphylococcus aureus (MRSA) were isolated. All of the MRCoNS isolates from this work presented different antimicrobial resistance patterns. MRCoNS may be present in humans associated with animals while not present in the animals. Selective pressure outside of the farm and a lack of MRCoNS transmission between humans and animals may be responsible for this lack of correlation. 相似文献
997.
998.
Juliano Ferreira Fernandes de Souza Eduardo Raposo Monteiro Daniela Campagnol Renata Conti Ramos Antonio Manoel Ferreira Frasson 《Journal of Equine Veterinary Science》2012
This study aimed to evaluate the effects of a constant rate infusion (CRI) of xylazine or xylazine in combination with lidocaine on nociception, sedation, and physiologic values in horses. Six horses were given intravenous (IV) administration of a loading dose (LD) of 0.55 mg/kg of xylazine followed by a CRI of 1.1 mg/kg/hr. The horses were randomly assigned to receive three treatments, on different occasions, administered 10 minutes after initiation of the xylazine CRI, as follows: control, physiologic saline; lidocaine low CRI (LLCRI), lidocaine (LD: 1.3 mg/kg, CRI: 0.025 mg/kg/min); and lidocaine high CRI (LHCRI), lidocaine (LD: 1.3 mg/kg, CRI: 0.05 mg/kg/min). A blinded observer assessed objective and subjective data for 50 minutes during the CRIs. In all treatments, heart and respiratory rates decreased, end-tidal carbon dioxide concentration increased, and moderate to intense sedation was observed, but no significant treatment effect was detected in these variables. Ataxia was significantly higher in LHCRI than in the control treatment at 20 minutes of infusion. Compared with baseline values, nociceptive threshold increased to as much as 79% in the control, 190% in LLCRI, and 158% in LHCRI. Nociceptive threshold was significantly higher in LLCRI (at 10 and 50 minutes) and in LHCRI (at 30 minutes) than in the control treatment. The combination of CRIs of lidocaine with xylazine produced greater increases in nociceptive threshold compared with xylazine alone. The effects of xylazine on sedation and cardiorespiratory variables were not enhanced by the coadministration of lidocaine. The potential to increase ataxia may contraindicate the clinical use of LHCRI, in combination with xylazine, in standing horses. 相似文献
999.
Kathryn Rose Owen Guy J. HinniganEllen R. Singer DCM DVSc DipACVS/ECVS MRCVS 《Journal of Equine Veterinary Science》2012
The following report documents an unusual anatomical finding in two cases of aseptic tenosynovitis of the digital flexor tendon sheath. Disruption of the vinculum attachment between the palmar/plantar border of the superficial digital flexor tendon and the adjacent palmar/plantar annular ligament was identified in combination with other tendon pathology within the digital flexor tendon sheath. This tenoscopic finding has not been described previously in the literature. 相似文献
1000.
Phenological and water-use patterns underlying maximum growing season length at the highest elevations: implications under climate change 总被引:1,自引:0,他引:1
Consequences of climate change on tree phenology are readily observable, but little is known about the variations in phenological sensitivity to drought between populations within a species. In this study, we compare the phenological sensitivity to temperature and water availability in Abies pinsapo Boiss., a drought-sensitive Mediterranean fir, across its altitudinal distribution gradient. Twig growth and needle fall were related to temperature, precipitation and plant water status on a daily scale. Stands located at the top edge of the distributional range showed the most favourable water balance, maximum growth rates and little summer defoliation. Towards higher elevations, the observed delay in budburst date due to lower spring temperatures was overcome by a stronger delay in growth cessation date due to the later onset of strong water-deficit conditions in the summer. This explains an extended growing season and the greatest mean growth at the highest elevation. Conversely, lower predawn xylem water potentials and early partial stomatal closure and growth cessation were found in low-elevation A. pinsapo trees. An earlier and higher summer peak of A. pinsapo litterfall was also observed at these water-limited sites. Our results illustrate the ecophysiological background of the ongoing altitudinal shifts reported for this relict tree species under current climatic conditions. 相似文献