全文获取类型
收费全文 | 35591篇 |
免费 | 2000篇 |
国内免费 | 121篇 |
专业分类
林业 | 1926篇 |
农学 | 1207篇 |
基础科学 | 242篇 |
6433篇 | |
综合类 | 3991篇 |
农作物 | 1500篇 |
水产渔业 | 2513篇 |
畜牧兽医 | 16909篇 |
园艺 | 463篇 |
植物保护 | 2528篇 |
出版年
2021年 | 458篇 |
2020年 | 473篇 |
2019年 | 527篇 |
2018年 | 912篇 |
2017年 | 1024篇 |
2016年 | 973篇 |
2015年 | 726篇 |
2014年 | 908篇 |
2013年 | 1669篇 |
2012年 | 1643篇 |
2011年 | 1750篇 |
2010年 | 1186篇 |
2009年 | 1098篇 |
2008年 | 1547篇 |
2007年 | 1499篇 |
2006年 | 1289篇 |
2005年 | 1210篇 |
2004年 | 1040篇 |
2003年 | 1079篇 |
2002年 | 902篇 |
2001年 | 1003篇 |
2000年 | 997篇 |
1999年 | 804篇 |
1998年 | 323篇 |
1997年 | 332篇 |
1995年 | 291篇 |
1992年 | 477篇 |
1991年 | 555篇 |
1990年 | 478篇 |
1989年 | 455篇 |
1988年 | 439篇 |
1987年 | 446篇 |
1986年 | 404篇 |
1985年 | 434篇 |
1984年 | 378篇 |
1983年 | 320篇 |
1982年 | 261篇 |
1979年 | 415篇 |
1978年 | 317篇 |
1977年 | 319篇 |
1976年 | 310篇 |
1975年 | 325篇 |
1974年 | 361篇 |
1973年 | 346篇 |
1972年 | 321篇 |
1971年 | 274篇 |
1969年 | 303篇 |
1968年 | 273篇 |
1967年 | 331篇 |
1966年 | 312篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Tecles F Martínez Subiela S Bernal LJ Cerón JJ 《Veterinary journal (London, England : 1997)》2000,160(3):242-249
Whole blood has been compared with erythrocytes and plasma for spectrophotometric cholinesterase determination in the dog. Cholinesterase activity was characterized using two substrates: acetylthiocholine and butyrylthiocholine. Acetylcholinesterase was the only form of cholinesterase present on erythrocytes and hydrolysed only acetylthiocholine. Butyrylcholinesterase (pseudocholinesterase) was predominant in plasma, hydrolysing mainly butyrylthiocholine. Based on these results, a method based on the use of two substrates (acetylthiocholine for monitoring acetylcholinesterase and butyrylthiocholine for determining butyrylcholinesterase) in the same whole blood sample is recommended for canine cholinesterase analysis. This way of monitoring both enzymes can be easily automated, yielding good within (CVs < 5%) and between-run (CVs < 7%) precision. 相似文献
92.
M Hertel U Kersten R Mischke I Nolte 《Berliner und Münchener tier?rztliche Wochenschrift》1999,112(6-7):239-242
Based on results of holter ecg recordings taken from 38 dogs the computerized analyses system turned out as method not exactly valuing the frequency and sensitivity of arrhythmias. Despite there was a significant correlation between the computerized and visual arrhythmia analysis for ventricular respectively supraventricular premature beats, in individual cases there was an important aberration between the particular values. 相似文献
93.
94.
Atrial fibrillation is a disorder of cardiac rhythmicity, and its importance in the horse depends on the underlying cause and the function of the horse. Before the decision is taken to start treatment, it has first to be ascertained whether treatment is worthwhile and whether the horse is an appropriate candidate for treatment. This article gives a short overview of current opinion on the cause and treatment of atrial fibrillation in the horse. The most used treatment at the moment, oral chinidine sulphate, is discussed. The hemodynamic consequences of atrial fibrillation and the response of a patient to treatment with chinidine sulphate are also discussed. 相似文献
95.
Multiple apparent Sarcocystis abortion in four bovine herds 总被引:1,自引:0,他引:1
Foetuses recovered from multiple abortions in four dairy herds had multifocal nonsuppurative encephalitis, myocarditis and hepatitis. Focal placentitis was usually present. Sarcocystis-like protozoa were found in the brains of foetuses from two of the outbreaks. Apart from excess salivation in a few cows in one herd, farmers reported no clinical abnormalities prior to the abortions, and all cows remained normal after the abortions. Dogs and cats fed an affected foetus and neonatal calves from the affected herds failed to excrete protozoa in their faeces. The identity of the protozoa in the foetal brain was not confirmed. 相似文献
96.
97.
The feline one-way mixed leukocyte reaction (MLR) was accomplished by a microtechnique assay using gradient purified mononuclear leukocytes from the peripheral blood of specific-pathogen-free (SPF) cats. An eight day assay was required with an appropriate serum supplement of rabbit or cat serum and obtainable cell concentrations of 1×105 mononuclear cells per well of each responder and stimulator population. This assay was devised as an correlate of cell-mediated immunity and to demonstrate that feline histocompatibility differences can be detected in culture. 相似文献
98.
99.
Carlos N. Marcos Trinidad de Evan Paloma García‐Rebollar Carlos de Blas Maria Dolores Carro 《Journal of animal physiology and animal nutrition》2019,103(5):1303-1312
Olive oil extraction generates olive cake (OC) that could be used in ruminant feeding. However, the chemical composition of OC is affected by multiple factors, being therefore highly variable. The objective of this study was to analyse the influence of storage time and further processing: crude, exhausted (subjected to a second oil extraction) and cyclone (obtained from a cyclone separator) on nutritive value of OC samples. Twelve samples (six crude and six exhausted) were obtained monthly from the same pond from 1 to 6 storage months, and nine samples (three crude, three exhausted and three cyclone) were obtained monthly from a different pond from 6 to 9 months storage. Chemical composition was analysed, and OC samples were fermented in vitro with sheep rumen fluid. Increasing storage time up to 6 months decreased sugars and total soluble polyphenols content but increased fibre content in OC. Dry matter effective degradability (DMED) decreased linearly (p < 0.001) by 35.9 and 45.5% as storage time augmented from 1 to 6 months for crude and exhausted OC, respectively. Crude OC had lower DMED values than exhausted OC (averaged values 0.255 and 0.294 g/g, respectively). Both potential production and rate of gas production were lower (p ≤ 0.018) in crude compared with exhausted OC, which was attributed to the high fat content of crude OC (≥86 g/kg dry matter). For samples stored longer than 6 months, cyclone had greater (p < 0.05) DMED than crude and exhausted OC (averaged values 0.207, 0.164 and 0.164 g/g, respectively). The results indicate that ruminal degradability of OC is reduced with advancing storage time, but only subtle changes were observed during the first two months. Cyclone showed greater degradability than crude and exhausted OC, but differences between crude and exhausted OC became negligible after five storage months. 相似文献
100.
Caspe SG Moore DP Leunda MR Cano DB Lischinsky L Regidor-Cerrillo J Alvarez-García G Echaide IG Bacigalupe D Ortega Mora LM Odeón AC Campero CM 《Veterinary parasitology》2012,189(2-4):171-181
The Nc-Spain 7 isolate of Neospora caninum, which was newly obtained from an asymptomatic congenitally infected calf, demonstrated a similar virulence as Nc-1 strain in mouse models. The aim of this study was to characterize the pathogenesis of Nc-Spain 7 isolate in cattle after experimental infection at 65 days of gestation. For this purpose, thirteen pregnant heifers were divided into three groups as follows: group A: 7 heifers inoculated with 1×10(8) tachyzoites of Nc-Spain 7 isolate; group B: 4 heifers inoculated with 1×10(8) tachyzoites of Nc 1 strain; and group C: 2 heifers received PBS. Serum samples were collected weekly and heparinized blood samples were collected three times (0, 28 and 42 days after inoculation) by jugular venipuncture. Placenta and fetal tissue samples were collected at time of necropsy. Specific antibody response in the dams was tested by IFAT, indirect ELISA, and rNcGRA7 and rNcSAG4 based-ELISA. Specific antibody response in fetal fluids was tested by IFAT. IFN-γ production was measured after in vitro culture of PBMC and the supernatant was assessed using a commercial kit (BOVIGAM). A significant increase in N. caninum antibody responses was detected in groups A and B by IFAT and by i-ELISA from day 14 after inoculation onwards. Besides, antibody response against rNCGra7 protein was also detected in all inoculated heifers by rNcGra7-based ELISA. Four fetuses from group A and one from group B were aborted between 3 and 5 weeks after infection. In the recovered fetuses, only 3 out of 4 fetal fluids from fetuses of group A and 1 out of 3 of group B were seropositive by IFAT, but all of them were positive by PCR. Transplacental transmission could be determined in all fetuses from groups A and B by PCR and/or IHC. Heifers of group C and their fetuses remained negative by all techniques. The results of this study demonstrate that the NC-Spain 7 isolate could be transmitted transplacentally, and produced fetal death and abortion in cattle. 相似文献