全文获取类型
收费全文 | 1999篇 |
免费 | 139篇 |
专业分类
林业 | 195篇 |
农学 | 65篇 |
基础科学 | 30篇 |
445篇 | |
综合类 | 83篇 |
农作物 | 113篇 |
水产渔业 | 288篇 |
畜牧兽医 | 733篇 |
园艺 | 39篇 |
植物保护 | 147篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 54篇 |
2021年 | 102篇 |
2020年 | 86篇 |
2019年 | 115篇 |
2018年 | 97篇 |
2017年 | 87篇 |
2016年 | 100篇 |
2015年 | 77篇 |
2014年 | 106篇 |
2013年 | 151篇 |
2012年 | 153篇 |
2011年 | 173篇 |
2010年 | 83篇 |
2009年 | 99篇 |
2008年 | 88篇 |
2007年 | 101篇 |
2006年 | 98篇 |
2005年 | 64篇 |
2004年 | 63篇 |
2003年 | 67篇 |
2002年 | 41篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1976年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1969年 | 2篇 |
1967年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有2138条查询结果,搜索用时 256 毫秒
181.
Castillo C Benedito JL Méndez J García-Partida P Vázquez P Pereira V López-Alonso M Hernández J 《Berliner und Münchener tier?rztliche Wochenschrift》2006,119(11-12):480-485
The aim of this study was to evaluate the effects of two dietary supplements (monensin and a live yeast culture) on acid-base balance in steers maintained in a commercial feedlot system, considering effects over the growing period (14 to 23 weeks of age). A 63-day feedlot study was performed using 42 double-muscled Belgian Blue steers. Steers were allotted randomly to one of the three study groups: (1) control group [no supplementation, C], (2) monensin supplementation [MON] at a concentration of 30 mg/kg (DM basis), and (3) live Saccharomyces cerevisiae strain supplementation [SACC] at a dose of 500 mg/kg (DM basis).Venous blood samples were collected for the measurement of acid-base parameters and L-lactate. Production parameters were also used as a complementary tool for understanding the internal changes associated with supplementation. Our results show that during the study period no statistical differences were observed between supplemented and control steers, although non-supplemented animals tended to gain more efficiently than those fed monensin or yeast. Nevertheless, taking into account blood parameters, these control animals showed a greater risk of acid overload due to a more marked decline in blood buffer levels over time in comparison with supplemented steers although no differences were observed between monensin or yeast supplemented animals. Additionally, significant effect of supplementation was observed in packed cell volume (PCV) values. 相似文献
182.
Management factors affecting stereotypies and body condition score in nonracing horses in Prince Edward Island 下载免费PDF全文
Christie JL Hewson CJ Riley CB McNiven MA Dohoo IR Bate LA 《The Canadian veterinary journal. La revue veterinaire canadienne》2006,47(2):136-143
In North America, there are few representative data about the effects of management practices on equine welfare. In a randomized survey of 312 nonracing horses in Prince Edward Island (response rate 68.4%), owners completed a pretested questionnaire and a veterinarian examined each horse. Regression analyses identified factors affecting 2 welfare markers: body condition score (BCS) and stereotypic behavior. Horses' BCSs were high (mean 5.7, on a 9-point scale) and were associated with sex (males had lower BCSs than females; P < 0.001) and examination date (P = 0.052). Prevalences of crib biting, wind sucking, and weaving were 3.8%, 3.8%, and 4.8%, respectively. Age (OR = 1.07, P = 0.08) and hours worked weekly (OR = 1.12, P = 0.03) were risk factors for weaving. Straw bedding (OR = 0.3, P = 0.03), daily hours at pasture (OR = 0.94, P = 0.02), and horse type (drafts and miniatures had a lower risk than light horses; P = 0.12) reduced the risk of horses showing oral stereotypies. Some of these results contradict those of other studies perhaps because of populations concerned. 相似文献
183.
Zafra-Gómez A Garballo A Morales JC García-Ayuso LE 《Journal of agricultural and food chemistry》2006,54(13):4531-4536
A fast, simple, and reliable method for the isolation and determination of the vitamins thiamin, riboflavin, niacin, pantothenic acid, pyridoxine, folic acid, cyanocobalamin, and ascorbic acid in food samples is proposed. The most relevant advantages of the proposed method are the simultaneous determination of the eight more common vitamins in enriched food products and a reduction of the time required for quantitative extraction, because the method consists merely of the addition of a precipitation solution and centrifugation of the sample. Furthermore, this method saves a substantial amount of reagents as compared with official methods, and minimal sample manipulation is achieved due to the few steps required. The chromatographic separation is carried out on a reverse phase C18 column, and the vitamins are detected at different wavelengths by either fluorescence or UV-visible detection. The proposed method was applied to the determination of water-soluble vitamins in supplemented milk, infant nutrition products, and milk powder certified reference material (CRM 421, BCR) with recoveries ranging from 90 to 100%. 相似文献
184.
Hydroxyl radicals (.OH) seem to have an important role in the oxidation of wine constituents and the production of important electrophilic aldehydes and ketones. In this experiment, glyceraldehyde, a .OH oxidation product of glycerol, recently described in wine, reacts with (+)-catechin, (-)-epicatechin, and malvidin-3-glucoside (Mv3gl), in model solutions, yielding new condensed phenolic compounds. The adduct compounds formed were separated by means of reversed phase liquid chromatography and detected and characterized using UV-vis and electrospray ionization mass spectrometry. Flavanol-flavanol and anthocyanin-flavanol adducts linked with glyceraldehyde yielded compounds with m/z ratios for their main ions, in positive ion mode, of 653.2 for the (+)-catechin dimer or the (-)-epicatechin dimer and 855.5 for Mv3gl/(+)-catechin or Mv3gl/(-)-epicatechin dimers. The possible occurrence of these compounds in wine is suggested, and the potential role of these and related reactions in wine aging is discussed. 相似文献
185.
Aguiar DM Cavalcante GT Rodrigues AA Labruna MB Camargo LM Camargo EP Gennari SM 《Veterinary parasitology》2006,142(1-2):71-77
For evaluation of the prevalence of anti-Neospora caninum antibodies and its associated risk factors, serum samples from 2109 cattle (11 beef, 50 dairy and 25 mixed farms) and 174 dogs were examined in the State of Rond?nia, Western Amazon, Brazil. An inquiry was applied in each farm. Sera were examined by the Indirect Fluorescence Antibody Test (IFAT) using cut off dilution of 1:25 for cattle and 1:50 for dogs. Statistical association between the serologic status and several variables were analyzed by linear and logistic regression. The overall herd prevalence of anti-N. caninum antibodies for 86 farms was 72% (61.3-81.2%). Prevalence values were 100, 70 and 64% in beef, dairy and mixed herds, respectively. Herd prevalence in beef herds was significantly different (P<0.05) from dairy and mixed herds. The overall animal prevalence of N. caninum in cattle was 8.8%. Prevalence values by animal were similar in different production types (P>0.05), with values of 9.5, 11.2 and 9.7% for beef, dairy or mixed cattle, respectively. Antibodies were found in 12.6% of the 174 examined dogs. Sixteen (22.8%) out of 70 farms with dogs had at least one dog with anti-N. caninum antibodies. The occurrence of antibodies in cattle was statistically associated with farms having more than 25 cows (OR 9.7, 95% IC 2.9-32.2; P=0.0002). There was no significant association between the presence of the dogs, jungle contact or reproductive variables with the occurrence of antibodies in cattle. 相似文献
186.
Trujillo M Mateos R Collantes de Teran L Espartero JL Cert R Jover M Alcudia F Bautista J Cert A Parrado J 《Journal of agricultural and food chemistry》2006,54(11):3779-3785
Antioxidant activities of lipophilic hydroxytyrosyl acetate, palmitate, oleate, and linoleate were compared with those of hydroxytyrosol, alpha-tocopherol, and butylhydroxytoluene (BHT) in both glyceridic matrix and biological systems. Aliquots of a glyceridic matrix spiked with various concentrations of antioxidant were subjected to accelerated oxidation in a Rancimat apparatus operated at 90 degrees C. The relationships between induction time (IT) and antioxidant concentration (mmol/kg) presented by hydroxytyrosol and hydroxytyrosyl acetate, palmitate, oleate, and linoleate were similar. Hydroxytyrosol and its esters showed greater antioxidant activity than alpha-tocopherol or BHT. We also evaluated the capacity of hydroxytyrosyl esters to protect proteins and lipids against oxidation caused by peroxyl radicals, using a brain homogenate as an ex vivo model. All tested compounds showed a protective effect in these systems, which was greater in preventing the generation of carbonyl groups in protein than of malondialdehyde in lipid. Inclusion of a lipophilic chain in the hydroxytyrosol molecule enhanced its antioxidant capacities in this biological model. 相似文献
187.
Fossils of a giant sauropod dinosaur, Turiasaurus riodevensis, have been recovered from terrestrial deposits of the Villar del Arzobispo Formation (Jurassic-Cretaceous boundary) of Riodeva (Teruel Province, Spain). Its humerus length (1790 millimeters) and estimated mass (40 to 48 metric tons) indicate that it may have been the most massive terrestrial animal in Europe and one of the largest in the world. Phylogenetic analysis indicates that the fossil represents a member of a hitherto unrecognized group of primitive European eusauropods that evolved in the Jurassic. 相似文献
188.
Cheong I Huang X Bettegowda C Diaz LA Kinzler KW Zhou S Vogelstein B 《Science (New York, N.Y.)》2006,314(5803):1308-1311
Clostridium novyi-NT is an anaerobic bacterium that can infect hypoxic regions within experimental tumors. Because C. novyi-NT lyses red blood cells, we hypothesized that its membrane-disrupting properties could be exploited to enhance the release of liposome-encapsulated drugs within tumors. Here, we show that treatment of mice bearing large, established tumors with C. novyi-NT plus a single dose of liposomal doxorubicin often led to eradication of the tumors. The bacterial factor responsible for the enhanced drug release was identified as a previously unrecognized protein termed liposomase. This protein could potentially be incorporated into diverse experimental approaches for the specific delivery of chemotherapeutic agents to tumors. 相似文献
189.
Baird JD Arroyo LG Vengust M McGurrin MK Rodriguez-Palacios A Kenney DG Aravagiri M Maylin GA 《Journal of the American Veterinary Medical Association》2006,229(1):104-110
CASE DESCRIPTION: 4 racehorses were examined because of markedly abnormal behavior following administration of fluphenazine decanoate. CLINICAL FINDINGS: Clinical signs included restlessness, agitation, profuse sweating, hypermetria, aimless circling, intense pawing and striking with the thoracic limbs, and rhythmic swinging of the head and neck alternating with episodes of severe stupor. Fluphenazine was detected in serum or plasma from all 4 horses. The dose of fluphenazine decanoate administered to 3 of the 4 horses was within the range (25 to 50 mg) routinely administered to adult humans. TREATMENT AND OUTCOME: In 2 horses, there was no response to IV administration of diphenhydramine hydrochloride, but the abnormal behavior in these 2 horses appeared to resolve following administration of benztropine mesylate, and both horses returned to racing. The other 2 horses responded to diphenhydramine administration. One returned to racing. The other was euthanized because of severe neurologic signs, respiratory failure, and acute renal failure. CLINICAL RELEVANCE: Findings indicate that adverse extrapyramidal effects may occur in horses given fluphenazine decanoate. These effects appear to be unpredictable and may be severe and life threatening. Use of fluphenazine decanoate as an anxiolytic in performance horses is not permitted in many racing and horse show jurisdictions, and analytic procedures are now available to detect the presence of fluphenazine in serum or plasma. 相似文献
190.
Brisson BA Reggeti F Bienzle D 《Journal of the American Veterinary Medical Association》2006,229(6):980-983
CASE DESCRIPTION: A 10-year-old Golden Retriever evaluated because of recurrent pericardial and pleural effusion underwent thoracoscopy with biopsy of the pleura and mediastinum. CLINICAL FINDINGS: Before thoracoscopy, 5 L of serosanguinous fluid was removed from the pleural cavity via thoracocentesis. During thoracoscopic exploration, it was observed that the parietal pleura and mediastinum were covered by miliary white to tan nodules 1 to 3 mm in diameter. Biopsy specimens were obtained, and partial pericardiectomy was performed. Portal sites were closed routinely. Cytologic evaluation of the pleural fluid revealed high protein concentration and cellularity, with cellular changes consistent with an exfoliating carcinoma. Results of bacterial culture were negative. TREATMENT AND OUTCOME: Carboplatin was administered via intracavitary instillation, and prednisone was administered orally. Twenty-one days later, 1 firm, irregularly shaped 6.5 x 3-cm mass and 4 smaller masses were detected in the area of the left thoracic wall where the cannula had been inserted during thoracoscopy. Histologic analysis of tissue from the masses collected at necropsy confirmed that they were malignant tumors with similar appearance to the pleural mesothelioma and immunohistochemical staining properties identical to those of the primary tumor. CLINICAL RELEVANCE: Although thoracoscopy is associated with less postoperative pain, shorter hospitalization times, and faster patient recovery than sternotomy procedures, complications are also possible with minimally invasive endoscopic surgery. Portal site metastasis can develop from contamination of portal sites with cells on instruments or cannulas or via leakage of effusion fluid. Although rare, this potential complication should be discussed with owners prior to performing the procedure. 相似文献