全文获取类型
收费全文 | 143882篇 |
免费 | 8403篇 |
国内免费 | 1459篇 |
专业分类
林业 | 7204篇 |
农学 | 6375篇 |
基础科学 | 1939篇 |
18586篇 | |
综合类 | 22881篇 |
农作物 | 5459篇 |
水产渔业 | 7628篇 |
畜牧兽医 | 72677篇 |
园艺 | 2333篇 |
植物保护 | 8662篇 |
出版年
2021年 | 1514篇 |
2020年 | 1582篇 |
2019年 | 1812篇 |
2018年 | 2531篇 |
2017年 | 3012篇 |
2016年 | 2791篇 |
2015年 | 2527篇 |
2014年 | 3001篇 |
2013年 | 6067篇 |
2012年 | 5012篇 |
2011年 | 5922篇 |
2010年 | 4097篇 |
2009年 | 3946篇 |
2008年 | 5447篇 |
2007年 | 5124篇 |
2006年 | 4966篇 |
2005年 | 4323篇 |
2004年 | 3955篇 |
2003年 | 3981篇 |
2002年 | 3718篇 |
2001年 | 5132篇 |
2000年 | 4907篇 |
1999年 | 3903篇 |
1998年 | 1625篇 |
1997年 | 1621篇 |
1996年 | 1442篇 |
1995年 | 1623篇 |
1994年 | 1460篇 |
1993年 | 1411篇 |
1992年 | 2868篇 |
1991年 | 3001篇 |
1990年 | 3004篇 |
1989年 | 2857篇 |
1988年 | 2589篇 |
1987年 | 2586篇 |
1986年 | 2535篇 |
1985年 | 2376篇 |
1984年 | 1951篇 |
1983年 | 1610篇 |
1982年 | 1137篇 |
1979年 | 1705篇 |
1978年 | 1316篇 |
1975年 | 1206篇 |
1974年 | 1408篇 |
1973年 | 1376篇 |
1972年 | 1345篇 |
1971年 | 1288篇 |
1970年 | 1279篇 |
1969年 | 1214篇 |
1967年 | 1146篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Michelle S Schulte Agnes E Rupley 《Veterinary Clinics of North America: Exotic Animal Practice》2004,7(2):315-50, vi-vii
Birds are becoming more popular as pets, and the need for veterinary professionals to learn more about these pets is crucial. This article introduces the veterinary staff to basic information required to provide high-quality care to avian patients. High-quality nutrition for a variety of species and ages is included in this article. The importance of proper husbandry and intellectual stimulation with toys is also discussed. Special emphasis is placed on instructions for clients when making appointments, as well as recognizing signs of illness for both clients and veterinary staff. Capture, restraint, and sample collection are an important part of this article, as well as medication administration, anesthesia, supportive care, preventive care and grooming. A variety of aspects concerning the care of the avian patient are covered for the benefit of the client and veterinary technician. 相似文献
992.
G Zamaratskaia J Babol A Madej EJ Squires K Lundström 《Reproduction in domestic animals》2004,39(3):168-172
This study describes the age-related variation in boar taint compounds, skatole and androstenone, and testosterone, oestradiol-17 beta (E17 beta), oestrone sulphate (ES), dehydroepiandrosterone sulphate (DHEAS), triiodothyronine (T(3)) and insulin-like growth factor-1 (IGF-1) in six boars. Three pairs of littermates of crossbred entire male pigs (from three Yorkshire x Duroc dams and one Hampshire sire) were included. Blood samples were taken at the age of 9-15 weeks and thereafter at weekly intervals from the age of 20-32 weeks. Plasma concentrations of skatole, androstenone, testosterone, E17 beta, ES, DHEAS, T(3) and IGF-1 were measured. We found that skatole levels in boars increased at the age around puberty after an increase in the levels of testicular steroids. Levels of skatole were not associated with the levels of sex steroids, T(3) and IGF-1. However, the increased level of testicular steroids is probably the underlying factor needed for high skatole levels to occur although the specific mechanism leading to increased skatole levels remains unknown. 相似文献
993.
The present studies were undertaken to examine the influence of mu (beta-endorphin, DAMGO, FK 33-824), delta (met-enkephalin, leu-enkephalin, DPLPE) and kappa opioid receptor agonists (dynorphin A, dynorphin B, U 50488) used at different doses (1-1000 nM) alone and in combination with LH (100 ng/ml) on steroidogenesis in porcine granulosa cells derived from large follicles. The effects of mu, delta and kappa receptor agonists on both basal and LH-induced progesterone (P4) secretion were negligible. Agonists of mu opioid receptors reduced basal androstenedione (A4), testosterone (T) and oestradiol (E2) release. Co-treatment with LH entirely abolished the inhibitory effect of these agonists on A4 and E2 secretion and resulted in an increase in T release. The addition of delta receptor agonists was followed by a decrease in basal A4, T and E2 secretion. The cells incubated in the presence of LH increased the androgen production and abrogated the inhibitory effect of delta agonists on E2 output. Basal A4, T and E2 release was also suppressed by kappa receptor agonists. The presence of LH in culture media extended the inhibitory effect of these opioids on E2 output and caused either abolition of the inhibitory influence of kappa agonists or even augmentation of both androgen release in response to the opioids. In conclusion, these data support the involvement of three major types of opioid receptors in the regulation of porcine granulosa cell steroidogenesis. 相似文献
994.
Jennifer E Stokes S Dru Forrester 《Veterinary Clinics of North America: Small Animal Practice》2004,34(4):909-22, vi
This article provides a source for easy reference, summarizing in one location newly recognized and unusual causes of acute renal failure (ARF) in dogs and cats. Several of the causes discussed in this article have been described previously. New or unusual causes of ARF in dogs and cats include infectious diseases (leptospirosis,borreliosis, and babesiosis), nephrotoxicants (aminoglycosides,vitamin D, and nonsteroidal anti-inflammatory drugs), and plant material (lilies and raisins/grapes). 相似文献
995.
K Christiana Grim Thomas McCutchan Jun Li Margery Sullivan Thaddeus K Graczyk Glenn McConkey Michael Cranfield 《Journal of zoo and wildlife medicine》2004,35(2):154-161
Captive juvenile African black-footed penguins (Spheniscus demersus) housed in an outdoor enclosure at the Baltimore Zoo have an average 50% mortality from avian malarial (Plasmodium sp.) infection each year without intense monitoring for disease and chemotherapeutic intervention. During the 1996 malaria transmission season, the safety and efficacy of an anti-circumsporozoite (CSP) DNA vaccine encoding the Plasmodium gallinaceum CSP protein against P. relictum were studied. The goal was to reduce clinical disease and death without initiating sterile immunity after release into an area with stable, endemic avian malaria. The birds were monitored for adverse clinical signs associated with vaccination, the stimulation of an anti-CSP antibody response, and protection afforded by the vaccine. The presence of P. relictum in trapped culicine mosquitoes within the penguin enclosure was monitored to assess parasite pressure. Among the vaccinated penguins, the parasitemia rate dropped from approximately 50% to approximately 17% despite intense parasite pressure, as determined by mosquito infection rate. During the year of the vaccine trial, no mortalities due to malaria occurred and no undesirable vaccination side effects occurred. This is the first trial of an antimalarial vaccine in a captive penguin colony. 相似文献
996.
Jennifer E Graham Michael S Kent Alain Théon 《Veterinary Clinics of North America: Exotic Animal Practice》2004,7(3):757-81, vii
The majority of information on oncology therapies has been reported in humans, canine, and feline patients, and laboratory animals with experimentally induced tumors. A variety of treatments,including radiation therapy, chemotherapy, photodynamic therapy, and others have been used with exotic animals. There are many species of exotic pets, and anatomic differences, as well as husbandry and nutritional requirements, must be taken into account to provide optimal care. By providing a broad overview of therapies and considerations for treatment, this article is intended to provide the practitioner with an overview of approach and options when addressing oncology cases in exotic animals. 相似文献
997.
Anna R M Gelzer Marc S Kraus 《Veterinary Clinics of North America: Small Animal Practice》2004,34(5):1127-44, vi
Atrial fibrillation (AF) is the most common clinically important arrhythmia in veterinary medicine. Electrical cardioversion of AF to sinus rhythm is feasible, but pharmacologic rate control is an effective and achievable treatment strategy for most veterinary patients. Recent human trials suggest that rate control and rhythm control are almost equally beneficial. Nevertheless, AF can be a challenging arrhythmia to manage, because most affected animal shave numerous other concurring problems associated with the underlying heart disease that dictate or influence the clinician's choice of treatment and monitoring strategy for each patient. 相似文献
998.
J. Fraser McConnell BVM&S Laurent S. Garosi DVM 《Veterinary radiology & ultrasound》2004,45(4):327-330
Intervertebral disk extrusion is rarely reported in the cat. In this case, the clinical, radiologic, and magnetic resonance imaging findings of an acute intramedullary intervertebral disk extrusion in a 5-year-old domestic shorthaired cat are described. Radiographically, there was mineralized disk material within the vertebral canal. On magnetic resonance images, the disk material was found to be within the spinal cord. A linear disk trail extending from the disk space into the spinal cord may be specific for intramedullary disk extrusion. 相似文献
999.