全文获取类型
收费全文 | 318746篇 |
免费 | 17465篇 |
国内免费 | 684篇 |
专业分类
林业 | 24672篇 |
农学 | 14223篇 |
基础科学 | 3001篇 |
46975篇 | |
综合类 | 42637篇 |
农作物 | 17471篇 |
水产渔业 | 18158篇 |
畜牧兽医 | 137280篇 |
园艺 | 6537篇 |
植物保护 | 25941篇 |
出版年
2019年 | 3744篇 |
2018年 | 4359篇 |
2017年 | 4783篇 |
2016年 | 5098篇 |
2015年 | 4518篇 |
2014年 | 5872篇 |
2013年 | 16621篇 |
2012年 | 7917篇 |
2011年 | 10257篇 |
2010年 | 7988篇 |
2009年 | 8428篇 |
2008年 | 9582篇 |
2007年 | 8697篇 |
2006年 | 9181篇 |
2005年 | 8469篇 |
2004年 | 8202篇 |
2003年 | 8007篇 |
2002年 | 7372篇 |
2001年 | 8415篇 |
2000年 | 8029篇 |
1999年 | 7087篇 |
1998年 | 4398篇 |
1997年 | 4446篇 |
1996年 | 4150篇 |
1995年 | 4827篇 |
1994年 | 4278篇 |
1993年 | 3965篇 |
1992年 | 5824篇 |
1991年 | 6118篇 |
1990年 | 6003篇 |
1989年 | 5912篇 |
1988年 | 5407篇 |
1987年 | 5484篇 |
1986年 | 5517篇 |
1985年 | 5607篇 |
1984年 | 5019篇 |
1983年 | 4569篇 |
1982年 | 3547篇 |
1981年 | 3342篇 |
1980年 | 3290篇 |
1979年 | 4490篇 |
1978年 | 3867篇 |
1977年 | 3527篇 |
1976年 | 3221篇 |
1975年 | 3207篇 |
1974年 | 3836篇 |
1973年 | 3869篇 |
1972年 | 3562篇 |
1971年 | 3370篇 |
1970年 | 3217篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
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
972.
973.
974.
Advances in immunoparasitology 总被引:1,自引:0,他引:1
E J Soulsby 《Veterinary parasitology》1985,18(4):303-319
A selective review of the advances in immunoparasitology is presented. It is selective simply because it is not feasible to embrace the whole field of parasitology within the compass of a single review paper, for if it were attempted, it would suffer undue abbreviation. Emphasis is placed on the advances in helminthology and especially the gastro-intestinal parasites of ruminants, an obvious selection because of the interests of the author. Reviews are always somewhat retrospective in outlook; to write a review at the present time is especially foolhardy since developments in biology are such that totally new concepts can arise almost overnight, as it were. This is a particularly healthy state, and the discipline of parasitology is caught up in the application and interpretation of molecular biological considerations. "Parasitism" is a field of increasing importance and challenge. 相似文献
975.
976.
977.
978.
As a result of the radioactive decay of rhenium-187 (4.6 x 10(10) years) the osmium-187/osmium-186 ratio changes in planetary systems as a function of time and the rhenium-187/osmium-186 ratio. For a value of the rhenium-187/osmium-186 ratio of about 3.2, typical of meteorites and the earth's mantle, the present-day osmium-187/osmium-186 ratio is about 1. The earth's continental crust has an estimated rhenium-187/osmium-186 ratio of about 400, so that for a mean age of the continent of 2 x 10(9) years, a present-day osmium-187/osmium-186 ratio of about 10 is expected. Marine manganese nodules show values (6 to 8.4) compatible with this expectation if allowance for a 25 percent mantle osmium supply to the oceans is allowed. The Cretaceous-Tertiary boundary iridium-rich layer in the marine section at Stevns Klint, Denmark, yields an osmium-187/osmium-186 ratio of 1.65, and the one in a continental section in the Raton Basin, Colorado, is 1.29. The simplest explanation is that these represent osmium imprints of predominantly meteoritic origin. 相似文献
979.
Bittner G 《Science (New York, N.Y.)》1983,222(4624):611-612
980.
B J Culliton 《Science (New York, N.Y.)》1983,220(4596):479-480
On April 14, 1983, federal district court judge Gerhard Gesell overturned, as "arbitrary and capricious," a Department of Health and Human Services regulation that required hospitals to post notices concerning the illegality of denying life-saving care to handicapped infants and encouraged anyone with knowledge of such a case to report it to HHS via a telephone hotline. This article reviews the evolution and implementation of the HHS regulation, the legal challenge to it, and the judge's ruling. 相似文献