全文获取类型
收费全文 | 4187篇 |
免费 | 190篇 |
国内免费 | 11篇 |
专业分类
林业 | 151篇 |
农学 | 145篇 |
基础科学 | 35篇 |
550篇 | |
综合类 | 575篇 |
农作物 | 160篇 |
水产渔业 | 221篇 |
畜牧兽医 | 2119篇 |
园艺 | 81篇 |
植物保护 | 351篇 |
出版年
2021年 | 44篇 |
2020年 | 50篇 |
2019年 | 54篇 |
2018年 | 63篇 |
2017年 | 56篇 |
2016年 | 62篇 |
2015年 | 57篇 |
2014年 | 67篇 |
2013年 | 209篇 |
2012年 | 166篇 |
2011年 | 176篇 |
2010年 | 93篇 |
2009年 | 97篇 |
2008年 | 206篇 |
2007年 | 180篇 |
2006年 | 178篇 |
2005年 | 178篇 |
2004年 | 141篇 |
2003年 | 160篇 |
2002年 | 160篇 |
2001年 | 130篇 |
2000年 | 111篇 |
1999年 | 77篇 |
1998年 | 49篇 |
1997年 | 50篇 |
1996年 | 46篇 |
1995年 | 50篇 |
1994年 | 40篇 |
1993年 | 34篇 |
1992年 | 47篇 |
1991年 | 68篇 |
1990年 | 71篇 |
1989年 | 62篇 |
1988年 | 62篇 |
1987年 | 62篇 |
1986年 | 70篇 |
1985年 | 68篇 |
1984年 | 62篇 |
1983年 | 59篇 |
1982年 | 39篇 |
1981年 | 35篇 |
1979年 | 37篇 |
1978年 | 42篇 |
1977年 | 46篇 |
1976年 | 35篇 |
1974年 | 37篇 |
1973年 | 37篇 |
1972年 | 35篇 |
1971年 | 33篇 |
1970年 | 35篇 |
排序方式: 共有4388条查询结果,搜索用时 15 毫秒
1.
2.
Comparative effects of mu and kappa opiate agonists on the cecocolic motility in the pony. 下载免费PDF全文
The electrical and mechanical activity of the large intestine and its response to administration of opiate mu and kappa agonists were assessed from electrodes and inductograph coils chronically implanted on the cecocolic segment in six ponies given a diet of hay and concentrates. Before the drugs were given, migrating complexes propagating from the cecum into the colon occurred at the rate of 1.5 to 16/hour. During this propulsive activity, the cecocolic sphincter opened and closed allowing the outflow of cecal contents and preventing the backflow of colic contents. Each pony was used as its own control and was given fentanyl (0.01 and 0.05 mg/kg of body weight, IV) and U50488H (0.1 and 0.5 mg/kg, IV) at weekly intervals. The mu agonist fentanyl elicited a marked phase of inhibition of the propulsive activity and a closure of the cecocolic sphincter that lasted one to two hours depending on the dose. The kappa agonist U50488H induced an inhibition of the short spiking activity, i.e. of the resting muscle tone. It did not disturb the occurrence of migrating complexes nor that of the openings of the cecocolic sphincter. These kappa compounds may be drugs of choice to alleviate visceral pain in colic stases without inducing delay of transit unlike mu compounds. 相似文献
3.
125I-labelling was used to characterise the surface components of five stocks of Trypanosoma evansi. Two components of 67 and 60.5 kD were labelled in two of the stocks, a single 60.5 kD component in two other stocks and no components in the remaining stock. These differences are probably related to the labelling method and biochemical differences between the stocks. 相似文献
4.
5.
Christopher L. Mariani DVM Simon R. Platt BVMS MRCVS Susan M. Newell DVM MS Scott P. Terrell DVM Cheryl L. Chrisman DVM MS EDS Roger M. Clemmons DVM PhD 《Veterinary radiology & ultrasound》2001,42(6):524-531
A 3-year-old neutered female mixed breed dog was examined because of severe, generalized seizure activity, tetraparesis, and encephalopathic signs. Cerebrospinal fluid (CSF) evaluation was unremarkable except for a mild increase in protein. Serum and CSF titers for infectious diseases were negative. Magnetic resonance (MR) imaging examination of the brain was performed and lesions were found within the cerebral gray matter of the temporal and parietal lobes. The lesions had increased signal intensity on T1, T2, and proton density-weighted images. There was mild inhomogeneous enhancement following intravenous contrast medium administration. Neurologic status improved and the seizures were well controlled, but the dog never regained normal mentation and euthanasia was performed 10 weeks after initial evaluation. At necropsy, severe cerebral cortical necrosis was found in the regions corresponding to the lesions seen on MR imaging examination. Large numbers of fat-containing macrophages (gitter cells) were found within these areas, and are thought to be responsible for the characteristic hyperintensity seen on the MR images. 相似文献
6.
Response time of broiler chickens to cimaterol: meat tenderness, muscle composition fiber size, and carcass characteristics. 总被引:4,自引:0,他引:4
The response time to cimaterol (CIM), a beta-adrenergic agonist, by broiler chickens for carcass characteristics, muscle composition, muscle fiber size, catheptic enzyme activity, and tenderness was determined. Two trials were conducted in which chickens were fed a control diet (CON) containing 0 ppm of CIM or a diet containing 1 ppm of CIM. Trial 1 consisted of 55, 31-d-old broiler chickens individually fed for up to 48 h. At 0, 6, 12, 18, 24, and 48 h, five CON and five CIM-fed chickens were killed. Trial 2 consisted of 160, 33-d-old broiler chickens group-fed for up to 14 d. At 2, 4, 6, 8, 10, 12, and 14 d, 10 CON and 10 CIM-fed chickens were killed. The breast muscle (BM) and leg muscle (LM) weight, cathepsin B and L activities, DNA, RNA, and protein concentration, and BM shear force value (SFV) were measured in both trials. Thigh muscle (TM) SFV were measured in Trial 2 only. Fiber size of BM was measured (five birds per treatment) at d 2, 6, 10, and 14. In Trial 1, BM weight and SFV were lower in CIM-fed birds at 6 h (P less than .05). In Trial 2 BM SFV were higher at d 8 (P = .06) and d 10 (P less than .05) in CIM-fed chickens. The SFV of CIM-fed chickens were higher at d 4, 8, 10, 12, and 14 (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
7.
R. S. Jones 《The Journal of small animal practice》1992,33(9):423-429
There are a variety of factors which are likely to influence the action of muscle relaxants in canine anaesthesia. These include age, body temperature and muscle diseases. Of the anaesthetic agents it is only the inhalational anaesthetic agents which significantly increase the duration of action of muscle relaxants. Antibiotic therapy particularly with the aminoglycoside antibiotics is likely to increase their duration of action. The indications for the use of muscle relaxants and the main contraindications such as the absence of anaesthetic equipment and the inability to ensure unconsciousness are discussed. The choice of anaesthetic technique together with a discussion on the premedication induction and maintenance of anaesthesia are important factors when using relaxants as is the technique of artificial ventilation. The various advantages and disadvantages of neuromuscular block monitoring are discussed as is the reversal of neuromuscular block. 相似文献
8.
Characterization of Brucella canis protein antigens and polypeptide antibody responses of infected dogs 总被引:1,自引:0,他引:1
The cytoplasmic protein antigens (CPAg) of Brucella canis were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and analysis of 35S-labeled polypeptides. Approximate molecular weights of the immunoreactive polypeptides were determined by migration patterns of the immunoprecipitated polypeptides after SDS-PAGE or Western immunoblotting of sera collected at various times after experimental infection of dogs. Polypeptides were specifically precipitated by sera of infected dogs, but not from the sera of normal or false-positive (seropositive, non-infected) animals. During the initial month after infection, proteins with molecular weight masses (MW) of approximately 18, 22, 31, 42 and 54 kDa were commonly recognized. A 20-kDa polypeptide was first recognized at 8-10 weeks after infection, but it was detected inconsistently after 6 months. Additional polypeptides detected from 2 to 12 months post-infection had MW of 22, 66-68 and, less regularly, 42, 60, 82, 100 and greater than 200 kDa. The polypeptides most consistently recognized in sera from B. canis-infected dogs had MW of 18, 22 and 68 kDa. 相似文献
9.
L.E. Young D.H. Bartram M. Diamond A. Gregg R.S. Jones 《Veterinary anaesthesia and analgesia》1991,18(Z1):171-174
10.