首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   120994篇
  免费   6998篇
  国内免费   802篇
林业   4595篇
农学   3890篇
基础科学   875篇
  14601篇
综合类   22948篇
农作物   4243篇
水产渔业   5947篇
畜牧兽医   62833篇
园艺   1613篇
植物保护   7249篇
  2020年   1048篇
  2019年   1291篇
  2018年   1892篇
  2017年   2164篇
  2016年   1942篇
  2015年   1764篇
  2014年   2050篇
  2013年   4312篇
  2012年   3810篇
  2011年   4707篇
  2010年   3193篇
  2009年   3015篇
  2008年   4335篇
  2007年   4180篇
  2006年   3827篇
  2005年   3620篇
  2004年   3353篇
  2003年   3407篇
  2002年   3094篇
  2001年   3982篇
  2000年   4064篇
  1999年   3136篇
  1998年   1265篇
  1997年   1126篇
  1996年   1033篇
  1995年   1244篇
  1994年   1102篇
  1993年   1052篇
  1992年   2434篇
  1991年   2650篇
  1990年   2564篇
  1989年   2456篇
  1988年   2326篇
  1987年   2388篇
  1986年   2388篇
  1985年   2169篇
  1984年   1846篇
  1983年   1570篇
  1979年   1556篇
  1978年   1256篇
  1977年   1060篇
  1976年   1044篇
  1975年   1136篇
  1974年   1438篇
  1973年   1424篇
  1972年   1402篇
  1971年   1248篇
  1970年   1200篇
  1969年   1183篇
  1967年   1029篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
In a feeding trial lasting for months Halothane-positive fattening pigs were put on a diet containing different concentrations of vitamin E and selenium. After a Myostress application vitamin E and selenium were additionally injected in order to examine stress resistance (CK-test) and regenerative capacity (histological examination of Musculus longissimus dorsi) of skeletal muscle. The study revealed that neither high dietary levels of vitamin E/selenium nor a vitamin E/selenium treatment applied after stress are capable of preventing stress related myopathy nor can they influence its healing up favourably.  相似文献   
2.
Seven of 30 canaries in an aviary in New Zealand developed ophthalmic problems. Clinically, 5 birds had unilateral and 2 birds had bilateral lesions characterized by conjunctivitis, crusty exudates on eyelids, and collapse of the eyeball. Microscopic lesions in 12 of 14 eyes examined included inflammation of the choroid and retina, with osseous replacement of the globe in some. Numerous Toxoplasma gondii tachyzoites were seen in the detached retina and vitreous humor of acutely affected birds. The diagnosis of toxoplasmosis was confirmed by immunohistochemical staining with T gondii antiserum. Affected birds had encephalitis, and T gondii was localized in the brains of these by immunohistochemical examination and by use of bioassays in mice. Toxoplasmosis should be considered in differential diagnosis of ophthalmitis in canaries.  相似文献   
3.
4.
Abstract. A humoral antibody response was demonstrated by ELISA in rainbow trout immunized intraperitoneally with extracts from the branchiuran ectoparasite Argulus foliaceus. A similar immunization protocol produced a higher titre response in a rabbit. Both trout and rabbit identified several antigenic components on immunoblots. ELISA and immunoblotting indicated that rainbow trout and rabbit anti-A. foliaceus sera identified components from the parasitic copepods Lepeophtheirus salmonis and Caligus elongatus.  相似文献   
5.
Monoclonal antibody c143 against tumor-associated antigen (TAA) expressed on bovine leukemia cells was conjugated to liposomes containing adriamycin (ADM), and therapeutic effects of conjugates were examined in leukemic or preleukemic cows to prevent the progression of the disease. Five cows with TAA-positive in their peripheral blood lymphocytes were divided into two groups. Each group of cows received 4 injections of ADM alone (0.4 mg/kg) or c143-conjugated liposomes containing the same dose of ADM (L-AMD-c143) through the jugular vein at about 4 day intervals. In three animals treated with L-ADM-c143, the TAA-positive cells gradually decreased with treatment and finally two animals became TAA-negative during a 6 week period and a 14 week period after treatment, respectively. In the control, two animals treated with ADM alone showed only a slight decrease of TAA-positive cells.  相似文献   
6.
The purpose of this study was to evaluate seasonal influences on thyroid hormone levels of healthy outdoor dogs in Hokkaido. We surveyed serum basal total thyroxine (tT4), free thyroxine (fT4), and canine thyroid-stimulating hormone (cTSH) levels, and tT4 levels after administration of TSH for a year. Basal tT4 levels decreased in January, and increased in August and September. fT4 levels increased in January and November. No significant seasonal variation was found in cTSH. tT4 levels after administration of TSH in August and November increased. These results suggested that the thyroid gland may have been activated in November. We should take seasonal variation into consideration when thyroid function is tested.  相似文献   
7.
8.
Grain yield and yield components (grains per ear, grain weight, 1000-grain weight, ear weight, ear seed ratio and dry matter partitioning between ear and seed) were examined in a wheat genotype (PBW-343) with well-filled grains and a Triticale genotype (DT-46) with poorly filled grains (showing grain shrivelling) grown in pots. Six days after anthesis (DAA), benzyladenine (BA) @2 µg ear−1 and abscisic acid (ABA) @4 µg ear−1 were injected at the base of the mother shoot ear in both species. It was observed that, in both wheat and Triticale , BA increased the grain weight, grain number and partitioning of dry matter between ear and seed, whereas ABA decreased the grain weight, grain number and dry matter partitioning between ear and seed. However, these decreases were slower in Triticale than in wheat. BA treatment increased the grain dry matter accumulation, which in turn resulted in better filling of grains and increased the grain weight in both wheat and Triticale . The average grain weight of Triticale was lower than that of wheat. Thus, it appears that variation in grain weight between wheat and Triticale might be due to different availabilities of growth-promoting phytohormones such as cytokinins and assimilates.  相似文献   
9.
Twelve (54.5%) of 22 free-roaming dogs in Ishigaki Island had tick infestation identified as Rhipicephalus sanguineus. There were 121 ticks recovered and consisted of 28 females, 58 males, 22 nymphs and 3 larvae. Infection of dogs possibly with canine ehrlichial pathogens was examined by both indirect immunofluorescence assay and polymerase chain reaction (PCR). Two dogs of the 13 examined were sero-positive for the human granulocytic ehrlichia agent, and one of two dogs was PCR positive for Ehrlichia platys. This dog had platelet numbers slightly lower than normal value, however, no morulae were found within platelet on peripheral blood smear stained with Giemsa.  相似文献   
10.
The isolation of (+)-totarol as active compound against Mycobacterium tuberculosis is reported from Chamaecyparis nootkatensis outerbark.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号