全文获取类型
收费全文 | 7529篇 |
免费 | 338篇 |
国内免费 | 8篇 |
专业分类
林业 | 558篇 |
农学 | 158篇 |
基础科学 | 37篇 |
1492篇 | |
综合类 | 1279篇 |
农作物 | 240篇 |
水产渔业 | 570篇 |
畜牧兽医 | 2780篇 |
园艺 | 209篇 |
植物保护 | 552篇 |
出版年
2023年 | 62篇 |
2022年 | 79篇 |
2021年 | 152篇 |
2020年 | 159篇 |
2019年 | 184篇 |
2018年 | 189篇 |
2017年 | 156篇 |
2016年 | 189篇 |
2015年 | 171篇 |
2014年 | 197篇 |
2013年 | 285篇 |
2012年 | 491篇 |
2011年 | 628篇 |
2010年 | 318篇 |
2009年 | 249篇 |
2008年 | 518篇 |
2007年 | 554篇 |
2006年 | 499篇 |
2005年 | 446篇 |
2004年 | 427篇 |
2003年 | 400篇 |
2002年 | 410篇 |
2001年 | 83篇 |
2000年 | 54篇 |
1999年 | 72篇 |
1998年 | 55篇 |
1997年 | 56篇 |
1996年 | 45篇 |
1995年 | 49篇 |
1994年 | 47篇 |
1993年 | 46篇 |
1992年 | 32篇 |
1991年 | 38篇 |
1990年 | 34篇 |
1989年 | 36篇 |
1988年 | 33篇 |
1987年 | 29篇 |
1986年 | 31篇 |
1985年 | 36篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 23篇 |
1981年 | 21篇 |
1980年 | 30篇 |
1979年 | 28篇 |
1978年 | 22篇 |
1977年 | 21篇 |
1974年 | 13篇 |
1973年 | 18篇 |
1966年 | 14篇 |
排序方式: 共有7875条查询结果,搜索用时 15 毫秒
91.
Fidel JL Pargass IS Dark MJ Holmes SP 《Journal of the American Animal Hospital Association》2008,44(4):210-217
A 5-year-old, spayed female cat was referred because of a mass in the cranial mediastinum noted on thoracic radiographs. A thymoma was diagnosed following ultrasound and biopsy of the mass. Treatment was initiated with coarse-fraction radiation therapy using external-beam therapy (four fractions of 5 Gy). The mass responded, but granulocytopenia developed. Bone marrow examination showed a myeloid to erythroid ratio of approximately 1:1, with a left shift within the myeloid line. These findings, as well as the lack of toxic changes within the peripheral blood neutrophils, suggested immune-mediated destruction of peripheral granulocytes. Immune suppression with prednisone and cyclosporine was instituted. After 7 weeks, the neutrophil count returned to normal. The tumor was removed, and cyclosporine was reduced and eventually discontinued 3 weeks postsurgery. 相似文献
92.
93.
K Jeraj J Basgen R M Hardy C A Osborne A F Michael 《American journal of veterinary research》1984,45(6):1162-1165
Renal tissue from 12 dogs with spontaneous diabetes and 16 control dogs were studied by light, immunofluorescence, and electron microscopies. Significant linear staining for immunoglobulin G and albumin were observed in the glomerular and tubular basement membranes of dogs with spontaneous diabetes--similar to that observed in human diabetes. On immunohistochemical grounds, it would appear that the dog with spontaneous diabetes is an appropriate model of diabetes in persons. 相似文献
94.
95.
The individual embarking on an iridium-192 brachytherapy program is faced with an abundance of concepts, terms and dosimetry techniques. This article introduces the beginning brachytherapist to the basic physical parameters of iridium-192, to the potential units for source strength and to the general concepts of the various dosimetry techniques. Multiple literature references are listed for more in-depth study. 相似文献
96.
The accuracy of heart rate estimation by cardiac auscultation over a 15-second period, and the influence of clinical experience on accuracy were evaluated in a dog with chronic atrial fibrillation by test subjects of varying experience. Only 30% of all test subjects provided accurate heart rate estimates. Board-certified specialists, medicine residents, and experienced nurses were significantly more accurate in their estimates than surgery residents and students. Accurate estimates were provided by 12.5% of surgery residents and students, as opposed to 64% of the other test subjects. Auscultatory estimates of heart rate in atrial fibrillation may be significantly inaccurate, and under some circumstances they may not provide a sound basis for making clinical decisions. 相似文献
97.
Nawrocki MA Mackin AJ McLaughlin R Cantwell HD 《Journal of the American Animal Hospital Association》2003,39(3):257-261
A 10-month-old, intact male Chihuahua presented for a 7-month history of regurgitation and coughing. Survey radiographs revealed a soft-tissue opacity within the distal esophagus. A contrast study confirmed the presence of an esophagobronchial fistula. Endoscopic removal of foreign material within the esophagus allowed for visualization of an esophageal diverticulum. Bronchoscopic examination revealed the presence of an abnormal opening in a right caudal tertiary bronchus. Passage of a cardiac guidewire was accomplished, confirming the presence of the fistula and aiding its subsequent surgical removal. 相似文献
98.
Eugene Mazimpaka Francis Mbuza Tukei Michael Eugene N. Gatari E. M. Bukenya Okwee-Acai James 《Tropical animal health and production》2017,49(8):1645-1656
A study was conducted to characterize the cattle production systems in Nyagatare District, Eastern Province of Rwanda using pre-tested questionnaires, interviews with key informants as well as focus group discussions in a period of 2 months. The respondents were selected by multi-stage sampling at sector and cell levels. Based on the procedure of Krejcie and Morgan (Educational and Psychological Measurement 30:607–610, 1970) to determine the overall sample size, the result indicated that the majority (98.3%) of farms were privately owned by large families of five to seven members, and most farmers (53.9%) had only primary education. Most respondents (52.6%) were in the age bracket of 41–50 years and were mainly (48.3%) located within 3 km from trading centers. The farm size averaged 6.5 ± 0.8 ha and most farms (64.7%) were fenced except in Rukomo Sector (50%) where zero grazing prevailed. Natural pastures (savanna grass land) were the main feed resource; tethering (9%) and communal grazing had diminished. Napier grass was the main planted forage (93.2%), followed by Chloris guyana (3.1%) and Brachiara (1.2%). Leguminous forages were rarely (2.5%) reported. Vita-mineral and salt block supplements, hay, and crop residues were the predominant supplementary feed stuffs used except in Karangazi and Rwemiyaga Sectors where only vita-mineral block predominated. However, maize and rice brans were reported to be the main feed stuffs used in supplementary feeding of lactating cows. Most farmers (89.7%) reported shortage of water as most of the farmers trekked their cattle to the nearest valley dams (59.2%), rivers (21.1%), and a few 6% had water on farms. Indigenous cattle were predominant (67.03%) followed by cross-breeds (28.37%) and exotics (4.6%) while all farmers kept small ruminants. Natural breeding predominated (74.9%) and most farms (60.6%) had animal houses most of which were temporary (52.8%). The reported mean age at first calving (AFC) was highest (40.2 ± .33) for Ankole and the lowest (29.1 ± .50) months for exotic cattle. Calving interval was shorter in local breeds than 65.7 ± 3.0 in exotic. The mean dairy milk yield was lowest for Ankole cattle 2.4 ± .08 as compared to the exotics (10.42 ± .36) and their crosses (7.2 ± .34). The main challenges were diseases, shortage of water, feeds, and inadequate extension services. Same observation was reported by Okello (African Journal of Range and Forage Science 22(3), 2005) in Uganda. 相似文献
99.
Michael J. Murray DVM MS D. Michael Cavey Bernard F. Feldman Steven S. Trostle Nathaniel A. White 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1997,11(4):199-203
Sympathetic denervation in a 20-year-old, gray, Thorough-bred-Percheron gelding was manifested by cutaneous hyperthermia and sweating over the right side of the body, demarcated by a line from the withers to the elbow and extending cranially. There was cutaneous hyperthermia over the right side of the head, but other signs of Horner's syndrome (sweating, ptosis, miosis, enophthalmos) were not present. The pattern of cutaneous hyperthermia and sweating was consistent with sympathetic denervation localized to the cervicothoracic ganglion, and thoracic radiographs revealed increased density in the craniodorsal thorax. Cytologic evaluation of a sample of pleural effusion revealed mesothelial cells containing melanin and cells suggestive of melanocytes or melanoblasts. Treatment with oral cimetidine and intrapleural cisplatin was not successful. A necropsy was not performed, but the clinical findings supported a diagnosis of thoracic melanoma involving the cervicothoracic ganglion. 相似文献
100.
A multiplex PCR assay for differentiating strongyle eggs from cattle has recently been described; however, the egg disruption and DNA extraction procedures, though effective, are inadequate for large studies or clinical application. The purpose of this research was to evaluate methods for disrupting trichostrongyle eggs, then assess commercial kits for extracting egg DNA using Ostertagia ostertagi as a model species. Egg disruption procedures tested included probe sonication, bath sonication, bead beating, boiling, microwaving, proteinase K/SDS digestion, freezing, and various combinations of the above with the incorporation of sodium dodecyl sulfate. These procedures were evaluated in conjunction with four commercial DNA extraction kits: DNA Stool mini kit and DNeasy Plant kit (Qiagen), Fast DNA kit (QBiogene), and the MAP extraction kit (Tetracore). Results showed that egg disruption was best accomplished with the bead beater and ceramic beads, resulting in 100% disruption within 1min. When DNA extraction was preceded by the isolation of eggs from feces, all procedures except the Fast DNA kit produced PCR-ready DNA from at least two eggs. The DNeasy Plant kit allowed consistent detection of DNA released from one egg. Due to the morphological similarities among trichostrongyle eggs in ruminants, strongyle eggs in equids, and hookworm eggs, the methods described herein may have broad application to other nematodes. 相似文献