全文获取类型
收费全文 | 48862篇 |
免费 | 2376篇 |
国内免费 | 706篇 |
专业分类
林业 | 3112篇 |
农学 | 1991篇 |
基础科学 | 612篇 |
8167篇 | |
综合类 | 7233篇 |
农作物 | 2318篇 |
水产渔业 | 3141篇 |
畜牧兽医 | 20871篇 |
园艺 | 1117篇 |
植物保护 | 3382篇 |
出版年
2022年 | 598篇 |
2021年 | 838篇 |
2020年 | 790篇 |
2019年 | 834篇 |
2018年 | 1304篇 |
2017年 | 1517篇 |
2016年 | 1405篇 |
2015年 | 1350篇 |
2014年 | 1464篇 |
2013年 | 2261篇 |
2012年 | 2564篇 |
2011年 | 2595篇 |
2010年 | 1768篇 |
2009年 | 1598篇 |
2008年 | 2025篇 |
2007年 | 1906篇 |
2006年 | 1580篇 |
2005年 | 2331篇 |
2004年 | 1893篇 |
2003年 | 1625篇 |
2002年 | 1072篇 |
2001年 | 1133篇 |
2000年 | 1037篇 |
1999年 | 934篇 |
1998年 | 330篇 |
1997年 | 325篇 |
1992年 | 584篇 |
1991年 | 694篇 |
1990年 | 620篇 |
1989年 | 587篇 |
1988年 | 591篇 |
1987年 | 547篇 |
1986年 | 537篇 |
1985年 | 535篇 |
1984年 | 460篇 |
1983年 | 389篇 |
1979年 | 522篇 |
1978年 | 396篇 |
1977年 | 394篇 |
1976年 | 370篇 |
1975年 | 438篇 |
1974年 | 468篇 |
1973年 | 447篇 |
1972年 | 447篇 |
1971年 | 379篇 |
1970年 | 315篇 |
1969年 | 387篇 |
1968年 | 366篇 |
1967年 | 438篇 |
1966年 | 385篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
I.-S. Park G. C. Choi D. S. Kim Y. K. Nam 《Journal of the World Aquaculture Society》2002,33(4):494-500
For the evaluation of hormonal control of spermiation in fish, a method to quanify the spermiation response of mature Rhynchocypris oxycephalus (Sauvage and Dabry) to hormonal therapy is described. Spermatocrit was determined after 7 min centrifugation at 18,000 ± g and sperm density was estimated by a standard hemocytomer method. Sperm density can be predicted from spermatocrit since their relationship is linear as described by the regression equation, Y = 3.68X - 27.18 ( R 2 = 0.82, N = 50). where Y is spermatocrit and × is sperm density. Milt production by mature R. oxycephalus was highest at 24 h after injection of 1,000 IU human chorionic gonadotropin (HCG) and 50 μg luteinizing hormone-releasing hormone analogue (LHRHa) per kg body weight. Increased milt production coincided with low spermatocrit and sperm density levels. These results demonstrate that spermiation in mature R. oxycephalus can be reliably evaluated by a spermatocrit method and that HCG and LHRHa are effective in stimulating of spermiation in this species. 相似文献
12.
We compared the results of the ACTH stimulation tests with measurements of alkaline phosphatase and serum cholesterol during Lysodren therapy in 23 dogs with pituitary-dependent hyperadrenocorticism. The ACTH stimulation test proved to be a very sensitive parameter, by which the extent of Lysodren under- or overdosage could be reliably estimated. On the other hand, regulation of the individual Lysodren requirement was not possible by measuring AP and serum cholesterol only. However, it is highly probable that those two parameters can be used to evaluate the general state of metabolism, and they appear to be of prognostic value when greatly elevated. 相似文献
13.
14.
P I Rekwot E O Oyedipe O O Akerejola A A Voh P M Dawuda 《The British veterinary journal》1989,145(1):85-88
Twenty-one Bunaji (White Fulani, Zebu) and 21 Friesian X Bunaji cross-bred bull calves, approximately 6 months of age, were each divided after weaning into two groups and fed isocaloric rations containing 14.45% (high protein) and 8.51% (low protein) crude protein for 10 months. Serum samples were collected biweekly for 10 months and analysed for serum proteins. Age had no significant effect. The Bunaji had significantly (P less than 0.05) higher total protein, albumin, and alpha 1-globulin than Friesian X Bunaji. While there was no significant difference in body condition score between the two breeds, the Friesian X Bunaji had a significantly (P less than 0.05) higher growth rate. Animals on high protein diets had significantly (P less than 0.05) higher total protein, albumin, alpha 2-globulin, gamma-globulin and total globulin than those on low protein. However, alpha 1-globulin and beta-globulin were not significantly (P greater than 0.05) different for the two treatment groups. 相似文献
15.
An account is given of the methodology for fractionation of cock spermatozoa into head and tail fractions by ultrasonication, followed by sucrose density gradient centrifugation. Quantitative estimates of DNA attested to 89.4% purity of the head fraction and low contamination of tails with heads. Recovery of protein and malic dehydrogenase (MDH) activity, following sperm fractionation, averaged 94.3% and 95.7%, respectively. Contamination of the head fraction with tails, as assessed by MDH assay, was only 4.65%, and the purity of the tail fraction was 91%. Intensive succinic dehydrogenase (SDH) activity was histochemically localised in the separated tail fraction and in the tail portion of intact spermatozoa. However, SDH activity was discernible neither in the head fraction nor in the head of intact spermatozoa. 相似文献
16.
17.
18.
19.
Platelet aggregation in healthy and sick cats after adding various aggregating agents is described. Feline platelets aggregate irreversibly in response to 0.15-1.0 micrograms/ml collagen, 1 microM ADP, 0.3 IU/ml test-thrombin and 0.71 NIH/ml Topostasin. Epinephrine, ristocetin and kaolin failed to cause aggregation. The aggregation function was decreased in a cat with liver damage and icterus; in 2 cats with uremia platelet aggregation was normal. Acetylsalicylic acid (ASA) (10 mg/kg iv) inhibits platelet aggregation in the presence of collagen in low concentrations; high concentrations of collagen succeeded in inducing platelet aggregation. 相似文献
20.
The technique of cystocentesis in dogs and cats was studied. The indications and contraindications of this method are discussed, using illustrations. 相似文献