全文获取类型
收费全文 | 31854篇 |
免费 | 1381篇 |
国内免费 | 8篇 |
专业分类
林业 | 1164篇 |
农学 | 917篇 |
基础科学 | 184篇 |
4794篇 | |
综合类 | 4308篇 |
农作物 | 1214篇 |
水产渔业 | 1248篇 |
畜牧兽医 | 17208篇 |
园艺 | 370篇 |
植物保护 | 1836篇 |
出版年
2021年 | 259篇 |
2020年 | 311篇 |
2019年 | 380篇 |
2018年 | 634篇 |
2017年 | 696篇 |
2016年 | 610篇 |
2015年 | 385篇 |
2014年 | 589篇 |
2013年 | 1720篇 |
2012年 | 963篇 |
2011年 | 1221篇 |
2010年 | 875篇 |
2009年 | 807篇 |
2008年 | 1181篇 |
2007年 | 1131篇 |
2006年 | 978篇 |
2005年 | 781篇 |
2004年 | 777篇 |
2003年 | 730篇 |
2002年 | 645篇 |
2001年 | 761篇 |
2000年 | 756篇 |
1999年 | 557篇 |
1998年 | 249篇 |
1997年 | 231篇 |
1995年 | 276篇 |
1992年 | 413篇 |
1991年 | 426篇 |
1990年 | 442篇 |
1989年 | 449篇 |
1988年 | 352篇 |
1987年 | 363篇 |
1986年 | 401篇 |
1985年 | 357篇 |
1984年 | 341篇 |
1983年 | 312篇 |
1979年 | 492篇 |
1978年 | 340篇 |
1977年 | 378篇 |
1976年 | 476篇 |
1975年 | 495篇 |
1974年 | 533篇 |
1973年 | 492篇 |
1972年 | 445篇 |
1971年 | 367篇 |
1970年 | 378篇 |
1969年 | 446篇 |
1968年 | 447篇 |
1967年 | 459篇 |
1966年 | 443篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
OBJECTIVE: To evaluate effects of butorphanol tartrate and buprenorphine hydrochloride on withdrawal threshold to a noxious stimulus in conscious African grey parrots. ANIMALS: 29 African grey parrots (Psittacus erithacus erithacus and Psittacus erithacus timneh). PROCEDURE: Birds were fitted with an electrode on the medial metatarsal region of the right leg, placed into a test box, and allowed to acclimate. An electrical stimulus (range, 0.0 to 1.46 mA) was delivered to each bird's foot through an aluminum perch. A withdrawal response was recorded when the bird lifted its foot from the perch or vigorously flinched its wings. Baseline threshold to a noxious electrical stimulus was determined. Birds then were randomly assigned to receive an i.m. injection of saline (0.9% NaCl) solution, butorphanol (1.0 mg/kg of body weight), or buprenorphine (0.1 mg/kg), and threshold values were determined again. RESULTS: Butorphanol significantly increased threshold value, but saline solution or buprenorphine did not significantly change threshold values. CONCLUSIONS AND CLINICAL RELEVANCE: Butorphanol had an analgesic effect, significantly increasing the threshold to electrical stimuli in African grey parrots. Buprenorphine at the dosage used did not change the threshold to electrical stimulus. Butorphanol provided an analgesic response in half of the birds tested. Butorphanol would be expected to provide analgesia to African grey parrots in a clinical setting. 相似文献
92.
93.
94.
B. Monteiro P. V. M. Steagall B. D. X. Lascelles S. Robertson J. C. Murrell P. W. Kronen B. Wright K. Yamashita 《The Journal of small animal practice》2019,60(8):459-462
This is the first of a series of capsule reviews published by the World Small Animal Veterinary Association ‐ Global Pain Council (WSAVA‐GPC). Each of these short articles provides a brisk assessment of the scientific evidence in specific aspects of pain management, including analgesic techniques, recommendations and controversies surrounding their use. In this first capsule review, the scientific evidence available on the long‐term use of non‐steroidal anti‐inflammatory drugs in cats with concomitant chronic pain and chronic kidney disease is discussed. 相似文献
95.
96.
Teratogenic effects of methylparathion / Wofatox 50 EC/ and Parathion 20 WP as positive control material were tested in pheasant embryos. On the 12th day of incubation 0.1 ml of the emulsions or suspensions of the insecticides at different concentrations was inoculated into the air space of embryonated eggs. The following dose levels were employed: 27 and 270 mg/kg egg of Wofatox 50 EC, and 10 mg/kg of Parathion 20 WP. Morphological changes were evaluated by macroscopic, skeletal staining and light microscopic examinations of the embryos. Primary hypoplasia or atrophy developed in the cervical musculature /m. longus colli/ accompanied by lordosis and scoliosis of the cervical spine. In most cases we also found cyllosis . 相似文献
97.
Eighty-four male white leghorn chickens were killed by CO2 gas to determine the type, rate, and sequence of microscopic postmortem changes in the adrenal glands of dry and wet intact carcasses. They were held at 29 or 18 C with 50% relative humidity for different times postmortem. The sequence of microscopic postmortem changes was similar in all chickens except at 18 C, when karyorrhexis of cortical and medullary cells was observed. Cellular changes occurred earlier at 29 C than at 18 C and in dry chickens but not in chickens wet with detergent solution before storage, although slight quantitative and qualitative differences between wet and dry chickens were noted. Medullary cells underwent postmortem changes earlier than cortical cells. Nuclei of medullary cells decreased in size, with chromatin clumping leading to pyknosis, followed by cytoplasmic vacuolation, cellular shrinkage, and finally karyolysis and cell dissociation. Cortical cells had nuclear chromatin marginated, nuclei reduced in size initially, and some nuclear fading, followed by pyknosis and karyolysis. Karyorrhexis was not a prominent feature of cortical and medullary cells, although it occasionally occurred before pyknosis. Cytoplasm of cortical cells remained eosinophilic, granular, and vacuolated, but vacuoles became finer later. Pyknotic medullary cells with vacuolated cytoplasm were observed as early as 3 hr postmortem, regardless of the temperature. Diffuse pyknosis of medullary cells was noted at 18 hr in chickens held at 29 C and at 48 hr in chickens held at 18 C. Marked cortical pyknosis was noted only at 36 hr in wet chickens held at 29 C, when bacterial invasion started. Dry chickens held 36 hr at 29 C had diffuse cellular dissociation, karyolysis and cytoplasmic acidophilia, and marked bacterial invasion. Erythrocytes were pyknotic and had cytoplasmolysis. It was concluded that adrenal glands may still be useful for histopathological examination before 18 hr at 29 C and before 48 hr at 18 C. 相似文献
98.
G.J. Benson D.V.M. M.S. S.K. Kneller D.V.M. M.S. M. Manohar B.V.Sc. Ph.D. J.C. Thurmon D.V.M. M.S. 《Journal of Equine Veterinary Science》1982,2(3):90-94
A radiographic technique was used to identify and characterize segmental diaphragmatic movement in anesthetized ponies breathing spontaneously and with controlled ventilation with and without muscle relaxant-induced paralysis. Paralyzed mechanically ventilated ponies were also studied at varying peak inspiratory pressures. Controlled ventilation induced a change in pattern of diaphragmatic displacement which was accentuated by paralysis and increased inspiratory pressure. In conclusion, these results indicate that uneven distribution of inspired gases is not corrected by mechanical ventilation. Furthermore, increased tidal volume during mechanical ventilation is largely wasted because this increased volume is distributed principally to the poorly perfused nondependent lung. Thus, while mechanical ventilation can alleviate hypoventilation, i.e., will decrease PaCO2, it will be of limited value in relieving arterial hypoxemia due to venous admixture in anesthetized patients. 相似文献
99.
Four- and six-week-old turkeys were vaccinated subcutaneously using avian influenza virus (AIV) A/Duck/613/MN/79 (H4N2) killed oil-emulsion vaccine. Sequential serological tests using agar gel precipitin (AGP), hemagglutination inhibition (HI), and enzyme-linked immunosorbent assay (ELISA) for measuring antibodies to AIV were performed up to 4 weeks postvaccination, when birds were challenged intranasally using A/Turkey/MN/80 (H4N2) live AIV. The ELISA was 25 to 1600 times more sensitive than the HI test and was able to detect antibody production earlier than the HI test. All turkeys with an ELISA titer of greater than or equal to 800 were protected against homologous challenge, as measured by virus recovery 3 days postchallenge. Four turkeys out of 20 serologically negative by AGP and HI tests but ELISA-positive were protected. 相似文献
100.
J. E. Van Dijk A. Fledderus J. M. V. M. Mouwen C. Holzhauer 《Veterinary research communications》1988,12(1):47-59
The significance of food allergy as a primary cause for gastrointestinal disturbances in domestic animals, especially calves and piglets, is discussed. The immunological backgrounds and pathogenesis are described in some detail. The clinical and pathological manifestations in animals are related to those in man. Diagnostic possibilities, therapy and prevention, as far as known in animals, are mentioned and, based on human experiences, further extensions are proposed. 相似文献