全文获取类型
收费全文 | 7064篇 |
免费 | 329篇 |
国内免费 | 6篇 |
专业分类
林业 | 487篇 |
农学 | 149篇 |
基础科学 | 36篇 |
1322篇 | |
综合类 | 1226篇 |
农作物 | 228篇 |
水产渔业 | 560篇 |
畜牧兽医 | 2686篇 |
园艺 | 198篇 |
植物保护 | 507篇 |
出版年
2023年 | 59篇 |
2022年 | 75篇 |
2021年 | 147篇 |
2020年 | 151篇 |
2019年 | 179篇 |
2018年 | 180篇 |
2017年 | 150篇 |
2016年 | 177篇 |
2015年 | 162篇 |
2014年 | 185篇 |
2013年 | 266篇 |
2012年 | 477篇 |
2011年 | 601篇 |
2010年 | 296篇 |
2009年 | 241篇 |
2008年 | 495篇 |
2007年 | 522篇 |
2006年 | 462篇 |
2005年 | 432篇 |
2004年 | 407篇 |
2003年 | 379篇 |
2002年 | 387篇 |
2001年 | 69篇 |
2000年 | 50篇 |
1999年 | 63篇 |
1998年 | 51篇 |
1997年 | 50篇 |
1996年 | 42篇 |
1995年 | 47篇 |
1994年 | 43篇 |
1993年 | 43篇 |
1992年 | 30篇 |
1991年 | 34篇 |
1990年 | 32篇 |
1989年 | 34篇 |
1988年 | 28篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 35篇 |
1984年 | 26篇 |
1983年 | 27篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 23篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1973年 | 17篇 |
排序方式: 共有7399条查询结果,搜索用时 0 毫秒
991.
992.
Tamar Akhvlediani Nazibrola Chitadze Rusudan Chlikadze Nino Rostiashvili Medea Betashvili Paata Imnadze Robert G. Rivard Mikeljon P. Nikolich Michael A. Washington Christian T. Bautista 《Zoonoses and public health》2019,66(7):835-841
Zoonotic diseases are endemic in the country of Georgia. Using the non‐linear canonical correlation (NCC) method, the aim of this study was to examine the relationship between thirteen epidemiological risk factors and seropositivity to five zoonotic infections (anthrax, Q fever, tularemia, leptospirosis, and Crimean‐Congo hemorrhagic fever [CCHF]) among Georgian military recruits during 2014–2016. According to this multivariate statistical technique, which is suitable for the analysis of two or more sets of qualitative variables simultaneously, two canonical variables were identified. These variables accounted for 68% of the variation between the two sets of categorical variables (“risk factors” and “zoonotic infections”). For the first canonical variable, there was a relationship among CCHF (canonical loading, which is interpreted in the same way as the Pearson's correlation coefficient, [cl] = 0.715), tick bites (cl = 0.418) and slaughter of animals (cl = 0.351). As for the second canonical variable, Q fever (cl = ?0.604) and leptospirosis (cl = ?0.486) were related to rodents inside and outside home (cl = ?0.346) and sweeping in or around home (cl = ?0.317). The NCC method allows researchers to obtain additional insights into the complex relationship between epidemiological risk factors and multiple zoonotic infections. 相似文献
993.
994.
995.
996.
David Süss Michael Iwersen Vanessa Schweinzer Erika Gusterer Peter Kanz Stefanie Krieger Harald Pothmann Karen Wagener Michael Hoelker Dawit Tesfaye Karl Schellander Ariane Helmbrecht Claudia Parys Marc Drillich 《Reproduction in domestic animals》2019,54(9):1265-1273
There is evidence that supplementing methionine has positive effects on uterine environment, oocyte quality and embryo development in cattle. Thus, the objective of this study was to evaluate reproductive traits of cows supplemented with rumen‐protected methionine (RPM) during early to mid‐lactation in comparison with an untreated control group (CON). An additional focus was on the effect of puerperal diseases on reproductive performance parameters in RPM‐supplemented group MET and in CON. A total of 1,709 multiparous Holstein‐Friesian cows were enrolled in this field trial conducted on a commercial dairy farm in Slovakia. Cows were allocated at approximately 12 days post‐partum (dpp) to either CON or MET, the latter supplemented with 25.0 g–27.2 g RPM per cow per day incorporated into the total mixed ration (TMR) until leaving the study pen at approximately 140 dpp. The amount of RPM was calculated based on individual feed ingredients analysis and adjusted during the study period when TMR changed. Cows were monitored during the post‐partum period by vaginal examination (day 5 pp), measuring of beta‐hydroxybutyrate in blood (3, 5, and 8 dpp) and by vaginal examination, uterine cytology and measuring of back fat thickness by ultrasound (all at 31 ± 3 dpp). Compared with CON, cows supplemented with RPM did not show better reproduction performance parameters (first service submission rate, days to first service, conception risk, days open 140). Results from binary logistic regression model for the risk of conception showed that metritis had a significant effect, but the supplementation of methionine had not. Results of Cox regression analysis for the odds of conception within 140 dpp revealed only metritis and clinical endometritis as significant factors. In conclusion, supplementation of RPM had no beneficial effect on reproductive performance in this study farm compared with an untreated control group. 相似文献
997.
Rashid J Weiss DJ Murtaugh MP Bach R 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1997,26(4):198-202
Tissue factor (TF), a cell surface-associated cofactor and activator of coagulation factor VII, has been implicated in the local and systemic activation of coagulation associated with sepsis. This study describes the pattern of TF expression in experimental bovine pneumonic pasteurellosis and endotoxemia. Immunohistochemical techniques were used to localize TF antigen in tissue sections. Tissue factor expression was not observed in tissues from control animals. In response to Pasteurella haemolytica challenge, TF was expressed within alveolar walls, by mononuclear inflammatory cells within alveoli, and in walls of arteries, arterioles, bronchi, and bronchioles. Tissue factor was not detected in unaffected lung, liver, spleen, lymph node or kidney tissue. Administration of Escherichia coli endotoxin intravenously resulted in tissue factor expression in lung, spleen, and lymph node tissue. Results of this study indicate that TF is expressed locally at sites of inflammation and systemically in endotoxemia. Therefore, TF may be involved in coagulation events associated with pneumonic pasteurellosis. 相似文献
998.
Allen AL Scott WM Cook SJ Fretz PB Doige CE 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1997,26(1):10-12
Studies were conducted to determine the effects of delaying the separation of serum from the clot and of long-term storage of serum samples on the measurement of thyroid hormones in blood from horses using a fluorescence polarization immunoassay. The measured concentrations of T3 and T4 were not affected by leaving serum on the clot for as long as 24 hours at room temperatures. Storage of serum for 19 to 22 months at -20 degrees C resulted in significant increases of measured T4, but not T3. These studies support previous work demonstrating that thyroid hormones are resistant to degradation, immunologically stable, and reasonably insensitive to potential problems of routine specimen handling when measured with an immunoassay. 相似文献
999.
1000.
Regina Campbell-Malone Susan G Barco Pierre-Yves Daoust Amy R Knowlton William A McLellan David S Rotstein Michael J Moore 《Journal of zoo and wildlife medicine》2008,39(1):37-55
Vessel-whale collision events represented the ultimate cause of death for 21 (52.5%) of the 40 North Atlantic right whales (Eubalaena glacialis) necropsied between 1970 and December 2006. Injuries seen in vessel-struck whales fall into two distinct categories: 1) sharp trauma, often resulting from contact with the propeller, and 2) blunt trauma, presumably resulting from contact with a vessel's hull. This study analyzes four trauma cases that resulted from vessel-whale collisions, which together provide a framework for a more critical understanding of lethal blunt and sharp trauma resulting from vessel collisions with right whales. In case no. 1, contact with a propeller resulted in three deep lacerations. The animal survived acute trauma only to succumb nearly 14 years later when the lesions reopened and became infected. In case no. 2, anecdotal reports linked the laceration of large arteries of the peduncle and histologic evidence of perimortem trauma at a bone fracture site to vessel-whale collision trauma. Case no. 3 had a laceration of the oral rete and a fracture of the rostrum. Both of the areas displayed histologic evidence of perimortem blunt trauma. Finally, in case no. 4, an antemortem mandibular fracture, two additional skull fractures, and widespread hemorrhage were consistent with severe blunt trauma. Evidence from each case, including the timing of trauma relative to the time of death and identifying characteristics of both trauma types, are presented. Before this study, no detailed comparative analysis of trauma pathology that resulted from lethal interactions between vessels and right whales had been conducted. This study demonstrates the importance of detailed gross and histologic examination in determining the significance and timing of traumatic events. This work represents a new paradigm for the differential diagnosis of lethal sharp and blunt trauma in right whales hit by ships and will enhance the present understanding of the impact of anthropogenic mortality on this critically endangered species. 相似文献