全文获取类型
收费全文 | 182876篇 |
免费 | 9658篇 |
国内免费 | 178篇 |
专业分类
林业 | 7821篇 |
农学 | 5778篇 |
基础科学 | 1192篇 |
22660篇 | |
综合类 | 33380篇 |
农作物 | 7395篇 |
水产渔业 | 8858篇 |
畜牧兽医 | 91376篇 |
园艺 | 2387篇 |
植物保护 | 11865篇 |
出版年
2019年 | 1875篇 |
2018年 | 2582篇 |
2017年 | 2925篇 |
2016年 | 2678篇 |
2015年 | 2200篇 |
2014年 | 2802篇 |
2013年 | 6913篇 |
2012年 | 5199篇 |
2011年 | 6392篇 |
2010年 | 4055篇 |
2009年 | 4156篇 |
2008年 | 6152篇 |
2007年 | 5814篇 |
2006年 | 5477篇 |
2005年 | 5154篇 |
2004年 | 4909篇 |
2003年 | 5048篇 |
2002年 | 4658篇 |
2001年 | 5217篇 |
2000年 | 5243篇 |
1999年 | 4210篇 |
1998年 | 1868篇 |
1997年 | 1789篇 |
1996年 | 1686篇 |
1995年 | 1966篇 |
1994年 | 1798篇 |
1993年 | 1647篇 |
1992年 | 3480篇 |
1991年 | 3637篇 |
1990年 | 3642篇 |
1989年 | 3651篇 |
1988年 | 3350篇 |
1987年 | 3340篇 |
1986年 | 3413篇 |
1985年 | 3314篇 |
1984年 | 2763篇 |
1983年 | 2407篇 |
1982年 | 1702篇 |
1979年 | 2595篇 |
1978年 | 2115篇 |
1977年 | 1803篇 |
1976年 | 1806篇 |
1975年 | 1961篇 |
1974年 | 2367篇 |
1973年 | 2361篇 |
1972年 | 2282篇 |
1971年 | 2144篇 |
1970年 | 2069篇 |
1969年 | 1993篇 |
1967年 | 1813篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Reference ranges for five parameters of blood coagulation were established in clinically normal farmed fallow deer (Dama dama) and red deer (Cervus elaphus). Storage of plasma at -15 degrees C resulted in small increases in activated partial thromboplastin time (APTT) for both species, and in the one stage prothrombin time (OSPT) of fallow deer, between days 1 and 30. These times were then stable between days 30 and 60. The fibrinogen levels of fallow deer plasma showed a small apparent increase over 60 days. These storage artefacts were not of sufficient magnitude to preclude the use of such plasma for diagnostic purposes although they could limit its use in research. Levels of fibrin/fibrinogen degradation products (FDP) were not affected by storage at -15 degrees C. Rabbit brain thromboplastin appeared adequate for OSPT determination in both species. The activated clotting time (ACT) is recommended as a field test for screening the intrinsic and common pathways of blood coagulation in deer. 相似文献
992.
Ten out of eleven subcutaneous abscesses in cats harboured anaerobic bacteria. Seven of the ten abscesses contained a mixture of obligate anaerobes and facultative anaerobes or microaerophilic bacteria. All of the anaerobic isolates were sensitive to the antibiotic metronidazole, but were resistant to streptomycin. Three isolates from one abscess were resistant to penicillin and ampicillin. Clinical resolution of subcutaneous abscesses was poor when procaine penicillin was used alone as treatment. 相似文献
993.
Transitional Cell Carcinoma of the Urinary Bladder in a Beluga Whale (Delphinapterus leucas) 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《The Canadian veterinary journal. La revue veterinaire canadienne》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Martineau D Lagacé A Massé R Morin M Béland P 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(10):297-302
A transitional cell carcinoma of the urinary bladder was found in a beluga whale stranded in the St. Lawrence middle estuary. Various organs of this animal were submitted to high resolution gas chromatography coupled with mass spectrometry analysis. High frequency of urinary bladder cancer in the human population of the same area and the presence of carcinogenic compounds in the marine environment of this animal are discussed.
Concurrent isolation of Edwardsiella tarda from various organs of this whale is also reported.
相似文献994.
Sources of variation and prospects for improvement of productive efficiency in the dairy cow: a review 总被引:4,自引:0,他引:4
D E Bauman S N McCutcheon W D Steinhour P J Eppard S J Sechen 《Journal of animal science》1985,60(2):583-592
In this review, "productive efficiency" in dairy cows is defined as the yield of milk obtained in ratio to the nutritional costs associated with maintenance, milk synthesis and loss of body condition during lactation. Improvements in efficiency could occur as a result of changes in digestion and nutrient absorption, maintenance requirement, utilization of metabolizable energy for production or nutrient partitioning. Digestibility can be greatly enhanced by appropriate dietary manipulation. Likewise, it may be possible to reduce maintenance requirements and improve the efficiency with which metabolizable energy is used for milk synthesis by manipulation of the pattern of nutrients presented to tissues. However, these factors apparently do not respond to selection for increased milk yield, and little variation is observed among cows. In contrast, individual cows differ substantially in feed intake and in the partitioning of nutrients among body tissues. Techniques associated with genetic engineering and the early prediction of genetic merit have the potential to improve productive efficiency by manipulation of these processes. However, changes in nutrient partitioning and feed intake during lactation are coordinated by a complex network of controls that accommodate the nutrient requirements of each tissue while maintaining homeostatic balance. Future improvements in productive efficiency will therefore depend on our ability to understand the manner in which these controls operate. 相似文献
995.
Shapiro JL Rostkowski C Little PB Smith-Maxie L Julian RJ Van Dreumel AA 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(5):155-158
Caprine β-mannosidosis, a fatal inherited deficiency of the lysosomal enzyme β-mannosidase, was diagnosed in neonatal female Nubian crossbred twin kids from a small herd near Guelph, Ontario. The kids had been tetraplegic since birth, with whole body tremors, abnormal nystagmus and an intention tremor of the head. 相似文献
996.
997.
Akers SW Mitchell CA 《HortScience : a publication of the American Society for Horticultural Science》1985,20(4):684-686
Periodic seismic (shaking) stress influenced the growth of sexual and asexual reproductive structures of three cultivated species. It delayed anthesis of Lycopersicon esculentum Mill. 'Patio' but not of Tagetes erecta L. 'Jubilee' or Solanum tuberosum L. 'Kennebec'. Shaken 'Jubilee' marigold plants produced the same number of flowers as undisturbed plants, but flowers of shaken plants were smaller. In contrast, seismic-stressed 'Patio' tomato produced fewer buds and flowers, but fruit set was enhanced relative to that of controls. Seismic stress also reduced tuber weight of 'Kennebec' potato, whereas tuber number was unaffected. The overall effect of seismic stress was to reduce the growth of reproductive structures and, in some cases, the number of reproductive structures that developed. 相似文献
998.
Wheeler RM Schwartzkopf SH Tibbitts TW Langhans RW 《HortScience : a publication of the American Society for Horticultural Science》1985,20(3):448-449
Polyurethane foam plugs commonly are used as collars or supports to grow plants in solution culture. Despite their utility, these foam plugs can be quite toxic to plants, particularly to small seedlings. We have observed tissue injury in tests using plugs to support lettuce, red beet, and potato plants in solution culture. Typically, the injury is initiated on the hypocotyl or stem tissue in direct contact with the foam, and appears within 30 hr as a brownish discoloration on the tissue surface. This discoloration can be followed by complete collapse of affected tissue and eventual death of the seedling. When injury does not progress beyond surface browning, the seedling survives but growth is slowed. In this paper, we report on different treatments that can be used to remove the toxicity of these plugs so they can be used in plant research. 相似文献
999.
1000.