全文获取类型
收费全文 | 157242篇 |
免费 | 8593篇 |
国内免费 | 373篇 |
专业分类
林业 | 6474篇 |
农学 | 5219篇 |
基础科学 | 1080篇 |
20462篇 | |
综合类 | 25418篇 |
农作物 | 6434篇 |
水产渔业 | 7915篇 |
畜牧兽医 | 80322篇 |
园艺 | 2127篇 |
植物保护 | 10757篇 |
出版年
2020年 | 1425篇 |
2019年 | 1668篇 |
2018年 | 2451篇 |
2017年 | 2803篇 |
2016年 | 2529篇 |
2015年 | 2123篇 |
2014年 | 2682篇 |
2013年 | 6453篇 |
2012年 | 4873篇 |
2011年 | 5969篇 |
2010年 | 3881篇 |
2009年 | 4039篇 |
2008年 | 5818篇 |
2007年 | 5455篇 |
2006年 | 5096篇 |
2005年 | 4736篇 |
2004年 | 4487篇 |
2003年 | 4610篇 |
2002年 | 4109篇 |
2001年 | 4913篇 |
2000年 | 4977篇 |
1999年 | 3934篇 |
1998年 | 1727篇 |
1997年 | 1674篇 |
1996年 | 1505篇 |
1995年 | 1780篇 |
1994年 | 1586篇 |
1993年 | 1437篇 |
1992年 | 3009篇 |
1991年 | 3239篇 |
1990年 | 3043篇 |
1989年 | 3124篇 |
1988年 | 2822篇 |
1987年 | 2768篇 |
1986年 | 2885篇 |
1985年 | 2734篇 |
1984年 | 2203篇 |
1983年 | 1969篇 |
1979年 | 2137篇 |
1978年 | 1730篇 |
1977年 | 1414篇 |
1976年 | 1465篇 |
1975年 | 1556篇 |
1974年 | 1832篇 |
1973年 | 1854篇 |
1972年 | 1752篇 |
1971年 | 1552篇 |
1970年 | 1523篇 |
1969年 | 1573篇 |
1967年 | 1391篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Adamama-Moraitou KK Pardali D Day MJ Prassinos NN Kritsepi-Konstantinou M Patsikas MN Rallis TS 《Veterinary journal (London, England : 1997)》2012,191(2):261-266
Canine bronchomalacia (BM) is characterized by weakness leading to collapse of the bronchial wall. A prospective study of 18 affected dogs (age range: 1-15 years) was undertaken to characterize the clinicopathological and histological features of BM. Poodles and Yorkshire terriers were commonly affected. Half of the dogs were overweight or obese. The clinical presentation was a mild, wheezing, chronic cough and pulmonary crackles were heard in 28% of the dogs. Compatible radiographic changes were present in 61% of the dogs. Using bronchoscopy, both lungs were affected in half of the animals, whereas in the others the disease appeared to affect predominantly the left lung. Analysis of bronchoalveolar lavage fluid and biopsies of bronchial mucosa revealed pure or mixed neutrophilic inflammation. Underlying infectious bronchitis was considered possible in 56% of the dogs. It was concluded that canine BM may present as an isolated clinical entity associated with infection and/or inflammation. 相似文献
992.
U. R. Zargar M. Z. Chishti A. R. Yousuf Fayaz Ahmad 《Veterinary research communications》2013,37(3):197-207
In order to assess the species richness and diversity profile of helminth parasite fauna in an endemic fish, an investigation was carried out in two urban and two rural lakes of Kashmir. Overall nine species of helminth parasites were observed in four lakes. Of these three were autogenic and six were allogenic. Heteroxenous parasite species were more in number than monoxenous species. Results showed significant differences in heteroxenous / monoxenous ratio between different lakes. Core species (Prevalence?>?20) were only found in hypertrophic lake (Anchar Lake). Overall, majority of helminth species were either secondary or satellite species. Prevalence of some helminth parasites showed significant differences in different lakes. In addition mean intensity showed significant differences between autogenic and allogenic parasites (P?<?0.05). Principle Component Analysis based on prevalence showed that Anchar Lake was strongly associated with most of helminth parasites. Diversity indices showed significant variation between different lakes. Maximum helminth species per host was in Anchar Lake. Finally we concluded that helminth parasite fauna showed significant differences in species richness and infection indices between different lakes. Diversity profile was higher in Anchar Lake in comparison to other three lakes. The results clearly show that environmental features of lake ecosystems have got an impact on distribution pattern of helminth parasites in S. esocinus. We suggest comparative parasitological study should be taken between different species of fish in order to have a clear picture regarding the species composition of helminth species in this region. Also we need to characterize the species spectrum of parasitic worms in fish of freshwater bodies of this region as well as other similar type of climatic zones because parasite fauna is an integral part of the inventory of biodiversity and as possible regulators of host populations in aquatic ecosystems. 相似文献
993.
Retrospective Evaluation of Horses Diagnosed with Neuroborreliosis on Postmortem Examination: 16 Cases (2004–2015) 下载免费PDF全文
994.
Effect of feeding different levels of wheat roti on nutrient utilization and blood metabolite profile in semi‐captive Asian elephants (Elephas maximus) 下载免费PDF全文
A. Das M. Saini S. Katole S. S. Kullu D. Swarup A. K. Sharma 《Journal of animal physiology and animal nutrition》2015,99(2):367-378
This experiment was conducted to study the effect of different levels of wheat roti (WR) on nutrient utilization and blood metabolites in Asian elephants fed roughages ad libitum. Nine (3 M, 6 F) Asian elephants (14–52 years of age, 1909–3968 kg BW) were used in an experiment based on replicated Latin square design. Animals in each group (n = 3) were assigned to one of the three dietary treatments in a manner that animals in all the three groups were exposed to all the three treatments in three different periods. Each feeding trial comprised 30 days (25 days of adaptation and 5 days collection period). The amount of WR fed to the elephants was 0.18, 0.12 and 0.06% of BW in groups I, II and III, respectively. They were allowed to forage in the nearby forests for 6 h/day and to bathe for 2 h/day. The animals had ad libitum access to cut Rohini (Mallotus philippensis) trees in their night shelter. Intake and apparent digestibility of dry matter (DM), crude protein (CP), gross energy (GE), Ca, P, Fe, Cu and Zn were measured. Feed consumption was not significantly different among the groups. Significant (p < 0.01) decrease in digestibility of DM and GE and blood glucose concentration was observed with decreased level of WR in the diet. Feeding of WR at 0.06% of BW supplied adequate amount of DE, CP, Ca, P, Fe, Cu and Zn to meet requirement for adult maintenance. Feeding of WR in excess of 0.06% of BW supplied DE in excess of requirement, increased blood glucose concentration which may cause obesity and other associated health problems. It was concluded that the amount of WR should be restricted to 0.06% of BW in the diet of captive Asian elephants. 相似文献
995.
Journal of Plant Diseases and Protection - Mixtures of micro-organisms may lead to more effective control of plant pathogens than biocontrol with single species, but little data exists on the... 相似文献
996.
M. Makungu H. B. Groenewald W. M. du Plessis M. Barrows K. N. Koeppel 《Anatomia, histologia, embryologia》2014,43(3):190-202
In family Lemuridae, anatomical variations exist. Considering its conservation status (near threatened) and presence of similarities between strepsirrhines and primitive animals, it was thought to be beneficial to describe the gross osteology and radiographic anatomy of the pelvis and hind limb of ring‐tailed lemurs (Lemur catta) as a reference for clinical use and species identification. Radiography was performed in 14 captive adult ring‐tailed lemurs. The radiographic findings were correlated with bone specimens from two adult animals. Additionally, computed tomography of the hind limbs was performed in one animal. The pelvic bone has a well‐developed caudal ventral iliac spine. The patella has a prominent tuberosity on the cranial surface. The first metatarsal bone and digit 1 are markedly stouter than the other metatarsal bones and digits with medial divergence from the rest of the metatarsal bones and digits. Ossicles were seen in the lateral meniscus, inter‐phalangeal joint of digit 1 and in the infrapatellar fat pad. Areas of mineral opacity were seen within the external genitalia, which are believed to be the os penis and os clitoris. Variations exist in the normal osteology and radiographic appearance of the pelvis and hind limb of different animal species. The use of only atlases from domestic cats and dogs for interpretative purposes may be misleading. 相似文献
997.
Diego A. Portela Marta Romano Gustavo A. Zamora Fernando Garcia-Pereira Luisito S. Pablo Bonnie J. Gatson Alana N. Johnson Pablo E. Otero 《Veterinary anaesthesia and analgesia》2021,48(1):116-124
ObjectiveTo compare the perioperative use of analgesics and complication rates in dogs administered an erector spinae plane (ESP) block or a traditional opioid-based (OP) treatment as part of analgesic management during hemilaminectomy.Study designRetrospective cohort study.AnimalsMedical records of 114 client-owned dogs.MethodsGeneral data included demographics, duration of procedure, number of laminae fenestrated, perioperative use of steroid and non-steroidal anti-inflammatory drugs. Intra- and postoperative analgesics used in 48 hours and complications rates were compared between groups. Opioid use was expressed in morphine equivalents [ME (mg kg?1)]. Continuous data were compared using the Mann–Whitney U test and incidence of events with a Fisher's exact tests. Multiple linear regression was used to evaluate association between perioperative ME consumption (dependent variable) with other independent variables. Data are presented as median (range). Differences were considered significant when p < 0.05.ResultsGroup ESP comprised 42 dogs and group OP 72 dogs. No differences were observed in the general data. Intraoperative ME was 0.65 (0.20–3.74) and 0.79 (0.19–5.60) mg kg?1 in groups ESP and OP, respectively (p = 0.03). Intraoperative infusion of lidocaine was administered intravenously (IV) to 23.8% and 68% of groups ESP and OP, respectively (p < 0.0001). Intraoperative infusion of ketamine was administered IV to 21% and 40% of groups ESP and OP, respectively (p = 0.04). Regression analysis revealed the ESP block as the only independent variable affecting the perioperative ME consumption. Pharmacological intervention to treat cardiovascular complications was administered to 21.4% and 47.2% of dogs in groups ESP and OP, respectively (p = 0.008). There were no differences in postoperative complication rates.Conclusions and clinical relevanceESP block was associated with reduced perioperative opioid consumption, intraoperative adjuvant analgesic use and incidence of pharmacological interventions to treat cardiovascular complications in dogs undergoing hemilaminectomy. 相似文献
998.
Schwan EV Miller DB de Kock D van Heerden A 《Journal of the South African Veterinary Association》2000,71(3):197-200
Acute liver failure was diagnosed in a 12-year-old cat. Fine needle aspirate cytology revealed high numbers of unsheathed microfilariae and a hepatocellular reaction with no evidence of bacterial infection. The microfilariae were identified as those of Dirofilaria repens by acid phosphatase staining. The high number of microfilariae seen in both the blood and the liver aspirate samples as well as the favourable response to ivermectin amongst other drugs administered, is suggestive that D. repens was the cause of the liver insult. A positive result obtained with an antigen-capture ELISA (Dirochek) for Dirofilaria immitis antigen was interpreted as false. This is the 1st report of Dirofilaria repens for South Africa. 相似文献
999.
A Baumberger 《Schweizer Archiv für Tierheilkunde》1979,121(4):179-185
1000.
Reproductive and growth data were obtained on 779 and 564 yearling beef heifers and bulls, respectively, that had sires with yearling scrotal circumference data at the San Juan Basin Research Center, Hesperus, CO. Partial regression coefficients of reproductive and growth traits on inbreeding (FXC) and age of the individual and adjusted scrotal circumference of sire (SCSI) were obtained. Growth and reproductive traits of heifers and growth and breeding soundness traits of bulls were analyzed. Separate analyses for each sex were performed, but least squares models were similar. Models included fixed effects of breed, birth year (BY), age of dam (AOD) and the covariates FXC, age (day of birth in heifer analyses) and SCSI. Scrotal circumference of sire was adjusted for age, FXC, AOD and BY using values obtained in a separate analysis. Seminal traits improved as age increased, and there was a seasonal effect present for age of puberty. Inbreeding had a detrimental effect on reproductive traits. Partial regression coefficients for the reproductive traits on SCSI were: age of puberty, -.796 d/cm; age of first calving, -.826 d/cm; julian day of first calving, -.667 d/cm; julian day of second calving, .597 d/cm; most probable producing ability, .132 %/cm; percent sperm motility, -.74 %/cm; percent primary sperm abnormalities, .08 %/cm; percent secondary sperm abnormalities, .92 %/cm; percent normal sperm, -1.28 %/cm; total breeding soundness examination score, .28 units/cm and scrotal circumference, .306 cm/cm. A heritability of .39 was obtained for scrotal circumference. 相似文献