全文获取类型
收费全文 | 4676篇 |
免费 | 266篇 |
国内免费 | 14篇 |
专业分类
林业 | 230篇 |
农学 | 260篇 |
基础科学 | 59篇 |
797篇 | |
综合类 | 377篇 |
农作物 | 199篇 |
水产渔业 | 204篇 |
畜牧兽医 | 2248篇 |
园艺 | 115篇 |
植物保护 | 467篇 |
出版年
2021年 | 38篇 |
2020年 | 80篇 |
2019年 | 62篇 |
2018年 | 85篇 |
2017年 | 102篇 |
2016年 | 79篇 |
2015年 | 65篇 |
2014年 | 85篇 |
2013年 | 205篇 |
2012年 | 178篇 |
2011年 | 234篇 |
2010年 | 190篇 |
2009年 | 173篇 |
2008年 | 228篇 |
2007年 | 188篇 |
2006年 | 183篇 |
2005年 | 181篇 |
2004年 | 159篇 |
2003年 | 153篇 |
2002年 | 168篇 |
2001年 | 136篇 |
2000年 | 131篇 |
1999年 | 110篇 |
1998年 | 54篇 |
1997年 | 38篇 |
1996年 | 45篇 |
1995年 | 44篇 |
1994年 | 55篇 |
1993年 | 58篇 |
1992年 | 85篇 |
1991年 | 76篇 |
1990年 | 85篇 |
1989年 | 74篇 |
1988年 | 45篇 |
1987年 | 63篇 |
1986年 | 50篇 |
1985年 | 57篇 |
1984年 | 63篇 |
1983年 | 53篇 |
1982年 | 54篇 |
1980年 | 38篇 |
1979年 | 41篇 |
1978年 | 46篇 |
1977年 | 46篇 |
1976年 | 44篇 |
1975年 | 34篇 |
1974年 | 41篇 |
1972年 | 34篇 |
1971年 | 34篇 |
1969年 | 44篇 |
排序方式: 共有4956条查询结果,搜索用时 11 毫秒
101.
Rat bite fever (RBF) is a bacterial zoonosis for which two causal bacterial species have been identified: Streptobacillis moniliformis and Spirillum minus. Haverhill fever (HF) is a form of S. moniliformis infection believed to develop after ingestion of contaminated food or water. 相似文献
102.
Millet S Cox E Van Paemel M Raes K Lobeau M De Saeger S De Smet S Goddeeris BM Janssens GP 《Veterinary journal (London, England : 1997)》2006,171(2):301-307
Two consecutive experiments were performed to evaluate the effects on the immune response of corn cob mix (CCM) in an organic pig diet. The immunoglobulin (Ig) M, IgA and IgG responses against an intramuscularly injected model antigen, bovine thyroglobulin, were used as indicator. The experiments were performed in an organic barn with nine pens of four crossbred pigs (two barrows and two sows) from 45 kg to slaughter. In the first experiment, the organic concentrate was mixed with organic CCM-silage to obtain three concentrate: CCM ratios of 100:0, 80:20 and 60:40 (w:w). In the second experiment, three concentrates were produced to obtain diets with equal nutrient levels on a dry matter basis after 0%, 20% and 40% CCM inclusion. Higher inclusion rates of CCM in the ration were accompanied by lower thyroglobulin-specific IgG responses. These effects could not be attributed to one specific component of the CCM, such as fatty acid composition, although there was a degree of correlation with lower vitamin A concentrations. Mycotoxin concentrations were absent or minimal. The study indicated that dietary ingredient composition may affect immunocompetence. 相似文献
103.
Snyder JM Shofer FS Van Winkle TJ Massicotte C 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2006,20(3):669-675
This study investigates the clinical and pathologic findings associated with 173 primary brain tumors in our hospital population of dogs that presented between the years 1986 and 2002. Of the 173 primary brain tumors, 78 (45%) were meningiomas, 29 (17%) were astrocytomas, 25 (14%) were oligodendrogliomas, 12 (7%) were choroid plexus tumors, and 7 (4%) were primary central nervous system lymphomas. Smaller numbers of glioblastomas (n = 5), primitive neuroectodermal tumors (n = 5), histiocytic sarcomas (n = 5), vascular hamartomas (n = 4), and unclassified gliomas (n = 3) were identified. One dog had both a meningioma and an astrocytoma. Most tumors were located within the telencephalon, and seizures were the most common clinical presenting complaint. Of 168 tumors for which a location in the brain was recorded at postmortem examination, 79 were found to involve more than 1 brain division. Other neoplasms unrelated to the primary brain tumor were identified on postmortem examination in 39 dogs (23%). Intrathoracic and intraabdominal neoplasms were present at necropsy in 13 and 24 cases, respectively. Based on the results of this study, thoracic radiographs and abdominal ultrasonography may be indicated to look for extracranial neoplasia prior to advanced imaging of the brain or intracranial surgery. 相似文献
104.
105.
Wellenberg GJ Bruschke CJ Wisselink HJ Barkema HW Van Oirschot JT 《Veterinary microbiology》2002,86(1-2):115-129
In this study, we examined whether an experimental bovine herpesvirus 4 (BHV4) infection can induce bovine mastitis, or can enhance bovine mastitis induced by Streptococcus uberis (S. uberis). Four lactating cows were inoculated intramammarily and intranasally with BHV4, and four lactating control cows were mock-inoculated. After 14 days, two of four cows from each group were inoculated intramammarily with S. uberis. No clinical signs were recorded in cows inoculated only with BHV4, and their milk samples showed no abnormal morphology, despite the fact that BHV4 replicated in inoculated quarters. Somatic cell count increased significantly in milk from three of six BHV4-inoculated quarters, compared to the non-inoculated quarters of the same cows (within-cow) and the quarters of mock-inoculated cows (control group) on days 8, 9 and 11 post-inoculation (pi). BHV4 was isolated from nasal swabs between days 2 and 9 pi. Clinical mastitis was observed in all four cows intramammarily inoculated with S. uberis. A preceding BHV4 infection did not exacerbate the clinical mastitis induced by S. uberis. S. uberis infections appeared to trigger BHV4 replication. From one quarter of each of two cows inoculated with BHV4 and S. uberis, BHV4 was isolated, and not from quarters inoculated with BHV4 only. In conclusion, BHV4 did not induce bovine clinical mastitis after simultaneous intranasal and intramammary inoculation. However, the BHV4 infection did induce subclinical mastitis in 50% of the cows and the quarters. 相似文献
106.
Thermography is a non-contact, non-invasive technique that detects surface heat emitted as infrared radiation. Because skin temperature reflects the status of underlying tissue metabolism and blood circulation, abnormal thermal patterns can signify areas of superficial inflammation. The objective of this study was to determine if thermography could detect the injection of analgesic and neurolytic agents and surgical palmar digital neurectomy. Procedures evaluated include injection of the lumbar region, suspensory ligaments, tibial nerve, palmar digital nerves, and palmar digital neurectomy. Thermographic images were obtained before and after the procedures until a significant difference was no longer detected. Local injection of the lumbar region and the suspensory ligament produced detectable thermal patterns for two days, and tibial nerve infiltration with a neurolytic agent was significant for two days. Analgesia of the palmar nerves was significant for 24h with bupivicaine, compared to five days for ammonium chloride. Palmar digital neurectomy produced more variable thermal patterns. While sensitive enough to detect changes in heat patterns from control regions, thermography is not specific enough to discriminate between procedures and injury inducing an inflammatory response. 相似文献
107.
de Bakker E Saunders J Gielen I van Bree H Coppieters E Van Ryssen B 《Veterinary and comparative orthopaedics and traumatology》2012,25(5):359-365
Objectives: To determine the frequency and radiographic aspect of medial humeral epicondylar lesions as a primary or concomitant finding and to evaluate the association with osteoarthritis. Methods: Medical records of dogs diagnosed with elbow lameness were reviewed. Inclusion criteria for this study were a complete clinical examination, a complete set of digital radiographs and a final diagnosis made by computed tomography or magnetic resonance imaging and arthroscopy. Changes of the medial humeral epicondyle were recorded and correlated with the radiographic osteoarthritis and final diagnosis. Results: Eighty of the 200 elbows showed changes of the medial humeral epicondyle. In 12 of these 80 elbows, changes of the medial epicondyle were the only findings within the joint, and these elbows were diagnosed with primary flexor enthesopathy. In the remaining 68 elbows, other concomitant elbow pathologies were found. In those cases of concomitant epicondylar changes, high grades of osteoarthritis were recorded, while most elbows with primary flexor enthesopathy showed a low grade of osteoarthritis. Clinical significance: Changes of the medial humeral epicondyle are often considered clinically unimportant and are regarded as an expression of osteoarthritis. This study showed the relatively frequent presence of epicondylar changes of which the majority were considered concomitant to a primary elbow problem. If changes of the medial humeral epicondyle are the only pathologic finding (primary flexor enthesopathy) they should be considered as the cause of lameness and not as a sign of osteoarthritis. 相似文献
108.
The production of double-yolked eggs and the duration of the rapid growth phase of yolks were measured in parental lines of White Plymouth Rock pullets and their crosses over 30 d, commencing with the day of first egg. Significant differences were found between mating combinations in the incidence of multiple-yolked eggs, but not in the period of rapid yolk growth. Heterosis and recombination effects for multiple ovulation were respectively -9% and -66% of the mean, while the corresponding values for the period required for rapid yolk growth were -1% and -5%. Three double-yolked eggs were observed containing yolks which differed by 3 d in their periods of rapid growth. Hypotheses are were presented for the origin of double-yolked eggs. 相似文献
109.
Ramaekers SP van Beukelen P Kremer WD van Keulen H Pilot A 《Journal of veterinary medical education》2011,38(4):360-372
We examined the design of a course that aims to ease the transition from pre-clinical learning into clinical work. This course is based on the premise that many of the difficulties with which students are confronted in this transition result from a lack of experience in applying knowledge in real practice situations. It is focused on the development of competence in solving clinical problems; uses an instructional model with alternating clinical practicals, demonstrations, and tutorials; and extends throughout the last pre-clinical year. We used a "proof-of-concept" approach to establish whether the core principles of the course design are feasible with regard to achieving the intended results. With the learning functions and processes as a frame of reference, retrospective analysis of the course's design features shows that this design matches the conditions from theories of the development of competence in solving clinical problems and instructional design. Three areas of uncertainty in the design are identified: the quality of the cases (information, openness), effective teaching (student and teacher roles), and adjustment to the development of competence (progress, coherence). 相似文献
110.
E. Kathalijne Visser Elvi E.C. Van Wijk-Jansen 《Journal of Veterinary Behavior: Clinical Applications and Research》2012,7(5):295-304
A reduced level of welfare of horses is related to management factors such as low forage feeding, short feeding time, social isolation, and lack of unrestrained exercise. It has been assumed that welfare problems can be reduced and/or partly prevented by improving the knowledge and skills of horse enthusiasts. It has also been assumed that to improve the provision of information to horse enthusiasts, it is important to explore and gain more insight into horse enthusiasts’ motives, knowledge, and behavior. The aim of this exploratory study was to identify the diversity of horse enthusiasts in the Netherlands, with respect to the way they search and find out information, their emotional involvement with horses, and their attitude, their knowledge, and daily practices with regard to equine welfare. A Web-based survey using a 30-item questionnaire resulted in 4,267 respondents. Most respondents (84.6%) were female; the average age of the respondents was 34.2 (±13.5) years. More than half of the respondents (64.5%) believed that there were welfare problems throughout the whole horse industry. The most important reported source for information was the personal contact with other horse enthusiasts (82.8%), with veterinarians (74.5%), and with farriers (69.5%). It is, therefore, recommended that to disseminate relevant knowledge on equine welfare, particular attention should be paid to the acquisition and dissemination skills within the education programs of veterinarians and farriers. Although most respondents were aware of the issues that can compromise welfare, their knowledge did not always result in appropriate practices. Furthermore, a cluster analysis showed that horse enthusiasts can be categorized into 4 clusters from the way they search and find out information, their emotional involvement with horses, and their attitude, their knowledge, and daily practices with regard to the welfare of horses. To improve the provision of information to horse enthusiasts, it is recommended that the information provision to horse enthusiasts is organized around these 4 clusters of horse enthusiasts. 相似文献