全文获取类型
收费全文 | 76419篇 |
免费 | 3761篇 |
国内免费 | 52篇 |
专业分类
林业 | 3595篇 |
农学 | 2342篇 |
基础科学 | 392篇 |
7914篇 | |
综合类 | 15524篇 |
农作物 | 3081篇 |
水产渔业 | 3401篇 |
畜牧兽医 | 38508篇 |
园艺 | 904篇 |
植物保护 | 4571篇 |
出版年
2018年 | 856篇 |
2017年 | 927篇 |
2016年 | 857篇 |
2015年 | 779篇 |
2014年 | 952篇 |
2013年 | 2602篇 |
2012年 | 1676篇 |
2011年 | 2070篇 |
2010年 | 1360篇 |
2009年 | 1285篇 |
2008年 | 2036篇 |
2007年 | 2078篇 |
2006年 | 1894篇 |
2005年 | 1831篇 |
2004年 | 1753篇 |
2003年 | 1781篇 |
2002年 | 1690篇 |
2001年 | 2215篇 |
2000年 | 2219篇 |
1999年 | 1846篇 |
1998年 | 700篇 |
1997年 | 698篇 |
1995年 | 812篇 |
1993年 | 696篇 |
1992年 | 1489篇 |
1991年 | 1551篇 |
1990年 | 1666篇 |
1989年 | 1644篇 |
1988年 | 1527篇 |
1987年 | 1477篇 |
1986年 | 1527篇 |
1985年 | 1515篇 |
1984年 | 1247篇 |
1983年 | 1144篇 |
1982年 | 771篇 |
1981年 | 717篇 |
1979年 | 1248篇 |
1978年 | 979篇 |
1977年 | 848篇 |
1976年 | 803篇 |
1975年 | 913篇 |
1974年 | 1201篇 |
1973年 | 1240篇 |
1972年 | 1255篇 |
1971年 | 1182篇 |
1970年 | 1102篇 |
1969年 | 1003篇 |
1968年 | 863篇 |
1967年 | 906篇 |
1966年 | 837篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Zahur AB Irshad H Hussain M Anjum R Khan MQ 《Journal of veterinary medicine. B, Infectious diseases and veterinary public health》2006,53(Z1):19-22
Transboundary animal diseases (TADs) are highly contagious and have the potential to spread very rapidly irrespective of the national borders, causing serious economic losses. These diseases cause high morbidity and mortality in susceptible animal populations. Furthermore, the extent of their consequences may significantly affect the food security and national economics. In Pakistan, the main TADs include rinderpest, peste des petits ruminants, foot and mouth disease and avian influenza. In the present paper the status of these diseases in Pakistan is discussed. 相似文献
992.
993.
Sinkora J Rehakova Z Sinkora M Cukrowska B Tlaskalova-Hogenova H 《Veterinary immunology and immunopathology》2002,87(3-4):301-306
Prenatal and early postnatal immune system development has been studied in minipigs. First leukocytes were observed in the yolk sac and fetal liver (FL) on the 17th day of gestation, the majority of them being SWC3(+). The colonization of the thymus (TH) with leukocytes was observed 21 days later. Two waves of fetal TH colonization with pro-T cells were deduced from the frequency of thymocyte subsets. Thymic B cells and immunoglobulin-secreting cells (Ig-SC) were studied by flow cytometry and ELISPOT, respectively. When the total numbers of fetal Ig-SC were compared, the TH was identified as the main source of natural antibodies and the only site of IgA and IgG synthesis. In germ-free animals, the TH also represented the major site of IgG and IgA production and the number of Ig-SC was not influenced by colonization with microflora. FL and bone marrow were identified as primary B lymphopoietic sites. The phenotype of B precursors was characterized and pre-B II cells were shown to be the dominant mononuclear fraction between DG50 and DG105. In the periphery, relative proportions of lymphocyte subsets were determined. Studies in gnotobiotic piglets have revealed that the appearance of CD4(+)CD8(+) T cells and CD2(-) B cells is absolutely dependent on the contact of immune system with live viruses and bacteria, respectively. 相似文献
994.
OBJECTIVE: To evaluate the postoperative morbidity and long-term outcome of dogs after dorsal laminectomy for caudal cervical spondylomyelopathy (CCSM). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Twenty dogs with CCSM. METHODS: Medical records of dogs treated by dorsal laminectomy for CCSM at North Carolina State University and Colorado State University between 1989 and 1999 were reviewed. Information on signalment, onset, progression and duration of clinical signs, diagnostic testing, sites of dorsal laminectomy, postoperative complications, length of hospitalization, and the ambulatory status on discharge was recorded. A minimum follow-up of 7 months was required for inclusion in the study. Neurologic status was graded (0 to 5) preoperatively, 2 days after surgery, and at the time of the study (final score). Improvement or worsening of the neurologic status was assessed by comparison of different scores for each dog. Additional follow-up information was obtained by means of a detailed telephone questionnaire directed at both the owner and referring veterinarian. RESULTS: Mean duration of clinical signs before surgery was 4.9 months. At admission, 15 dogs were ambulatory and 5 were nonambulatory. Neurologic status worsened in 70% of dogs 2 days after surgery but improved in all but 1 dog over the long term. Mean time to optimal recovery was 3.6 months. Long-term follow-up ranged from 7 months to 9 years (mean +/- SD, 3.2 +/- 2.4 years). Four dogs had confirmed recurrence; 2 other dogs may have had recurrence. CONCLUSIONS: Dorsal cervical laminectomy is an effective treatment for CCSM in those dogs with dorsal compression or multiple sites of involvement. CLINICAL RELEVANCE: Although most dogs' neurologic status transiently worsened after surgery, long-term outcome and recurrence rates were comparable to those seen with other surgical techniques for CCSM. 相似文献
995.
Talcott KW Schulz KS Kass PH Mason DR Stover SM 《American journal of veterinary research》2002,63(11):1520-1526
OBJECTIVE: To develop a model for measuring rotary stability of the canine elbow joint and to evaluate the relative contribution of the anconeal process (AN), lateral collateral ligament (LCL), and medial collateral ligament (MCL). SAMPLE POPULATION: 18 forelimbs from 12 canine cadavers. PROCEDURE: Forelimbs were allocated to 3 experimental groups (6 forelimbs/group). Each intact forelimb was placed in extension at an angle of 135 degrees and cycled 50 times from -16 degrees (pronation) to +28 degrees (supination) in a continuous manner at 2.0 Hz. Cycling was repeated following sectioning of the structure of interest (group 1, AN; group 2, LCL; and group 3, MCL). Torque at -12 degrees (pronation) and +18 degrees (supination) was measured for each intact and experimentally sectioned limb. A Student t test was performed to compare torque values obtained from intact verses experimentally sectioned limbs and for comparison with established criteria for differentiation of primary (> or = 33%), secondary (10 to 33%), and tertiary rotational stabilizers (< 10%). RESULTS: In pronation, the AN was the only primary stabilizer (65%). For supination, the LCL was a primary stabilizer (48%), AN was a secondary stabilizer (24%), and MCL was a tertiary stabilizer (7%). CONCLUSIONS AND CLINICAL RELEVANCE: With the elbow joint in extension at an angle of 135 degrees, the AN is a primary rotational stabilizer in pronation, and the LCL is a primary stabilizer in supination. Disruption of the AN or LCL may affect rotary range of motion or compromise stability of the elbow joint in dogs. 相似文献
996.
Objective and design Retrospective study of the outcomes of Heimlich valve drainage in dogs.
Procedure Medical records of the past 3 years were retrospectively reviewed. Heimlich valve drainage was used in 34 dogs (median body weight 30 ± 5 kg): lobectomy (n = 15), pneumonectomy (n = 9), intrathoracic oesophageal surgery (n = 2), diaphragmatic hernia repair (n = 1), traumatic open pneumothorax (n = 2), bilobectomy (n = 2), ligation of the thoracic duct (n = 1), and chylothorax and pneumothorax (n = 1 each). Evacuation of air and/or fluid from the pleural cavity was performed with the Heimlich valve following thoracostomy tube insertion. During drainage, the dogs were closely monitored for possible respiratory failure. Termination of Heimlich valve drainage was controlled with underwater seal drainage and assessed with thoracic radiography.
Results Negative intrathoracic pressure was provided in 29 dogs without any complications. Post pneumonectomy respiratory syncope and post lobectomy massive hemothorax, which did not originate from the Heimlich valve, were the only postoperative complications. Dysfunction of the valve diaphragm, open pneumothorax and intrathoracic localisation of an acute gastric dilatation–volvulus syndrome caused by a left-sided diaphragmatic hernia following pneumonectomy were the Heimlich valve drainage complications.
Conclusions The Heimlich valve can be used as a continuous drainage device in dogs, but the complications reported here should be considered by veterinary practitioners. 相似文献
Procedure Medical records of the past 3 years were retrospectively reviewed. Heimlich valve drainage was used in 34 dogs (median body weight 30 ± 5 kg): lobectomy (n = 15), pneumonectomy (n = 9), intrathoracic oesophageal surgery (n = 2), diaphragmatic hernia repair (n = 1), traumatic open pneumothorax (n = 2), bilobectomy (n = 2), ligation of the thoracic duct (n = 1), and chylothorax and pneumothorax (n = 1 each). Evacuation of air and/or fluid from the pleural cavity was performed with the Heimlich valve following thoracostomy tube insertion. During drainage, the dogs were closely monitored for possible respiratory failure. Termination of Heimlich valve drainage was controlled with underwater seal drainage and assessed with thoracic radiography.
Results Negative intrathoracic pressure was provided in 29 dogs without any complications. Post pneumonectomy respiratory syncope and post lobectomy massive hemothorax, which did not originate from the Heimlich valve, were the only postoperative complications. Dysfunction of the valve diaphragm, open pneumothorax and intrathoracic localisation of an acute gastric dilatation–volvulus syndrome caused by a left-sided diaphragmatic hernia following pneumonectomy were the Heimlich valve drainage complications.
Conclusions The Heimlich valve can be used as a continuous drainage device in dogs, but the complications reported here should be considered by veterinary practitioners. 相似文献
997.
Khan HA Siddique M Arshad M Abubakar M Akhtar M Arshad MJ Ashraf M 《Tropical animal health and production》2009,41(4):427-430
A total of 70 sheep and 330 goats were selected randomly. All the animals were kept under same housing and management conditions.
Serum samples were collected from all the animals and tested for the presence of antibodies against Peste des petits ruminants
(PPR) virus using competitive ELISA (cELISA). All the animals were found negative showing percentage inhibition (PI) values
<50. The animals were vaccinated against PPR with Nig/75/1 strain vaccine of PPR Serum samples were collected from randomly
selected 12 sheep and 30 goats at 10, 30 and 45 days post-vaccination. The samples were subjected to cELISA to determine the
presence of antibodies against PPRV. The samples with PI >50 were considered as sero-positive. The sheep found positive at
10, 30 and 45 days post-vaccination were 1(8.3%), 7(58.3%) and 12(100%) respectively. In case of goats 3(10.0%), 29(96.6%)
and 27(90.0%) animals gave positive results at 10, 30 and 45 days post-vaccination respectively. Mean PI values in sheep at
10, 30 and 45 days post-vaccination were recorded as 37, 65 and 91 respectively, whereas in goats these values were 43, 78
and 86 respectively. 相似文献
998.
J. Plendl M. Bahramsoltani O. Gemeinhardt H. Hünigen S. Käßmeyer P. Janczyk 《Anatomia, histologia, embryologia》2009,38(5):355-360
Teaching morphology, a fundamental part of medicine curricula is traditionally based on lectures and practical trainings. We introduced peer-assisted learning (PAL) and student expert teams to the courses to give the students the possibility to improve their free speech and self-confidence. We involved students in active preparation of online materials such as labelled e-slides and e-pics . We offered online digital microscopy (ZoomifyTM ) and dissection (CyberPrep) allowing repeating the learned material and studying veterinary morphology outside the dissection theatre. Over 60% of first and third semester students profited from being a peer or being taught by a peer and 50% said the expert teams were an excellent method to learn the topographic anatomy. Almost all students applied ZoomifyTM and CyberPrep and 75% of them found the digital microscopy and dissection to be a helpful or very helpful learning tool. In face of reduced contact hours, these forms of education compensated in part the lost teaching time. We observed improvement of rhetoric and presentation skills and self-confidence. The approaches should therefore find their constant place in the veterinary medicine curricula. 相似文献
999.
Immature worms were recovered from the liver parenchyma of rats which received extracts of metacercariae or adult worms of Fasciola gigantica, after challenge infection. When resistance was assessed by counting the number of immature worms, exposure of the animals to extracts of these two stages of the flukes conferred a significant degree of protection against challenge with F gigantica metacercariae. Rats given the extract of metacercariae were more resistant to infection than rats immunised with the extract of adult worms. 相似文献
1000.
In a series of 4 papers computerized herd reports on various aspects of dairy farming, the Index Lists, are presented for herd health and production control purposes. This fourth paper regards Index List 4 on nutritional disorders, body condition and ration composition. The information from this list is suitable to monitor nutritional efficiency and feeding management, especially when used in combination with information from the other index lists. Methods for interpretation and evaluation of the data listed are provided. Evaluations should take into account the aspects related to nutrition. It is demonstrated how deviations of index figures are detected and how advice to farm management is built up by means of actual information and prompt computerized analysis. 相似文献