全文获取类型
收费全文 | 132481篇 |
免费 | 7272篇 |
国内免费 | 93篇 |
专业分类
林业 | 5381篇 |
农学 | 4269篇 |
基础科学 | 831篇 |
17040篇 | |
综合类 | 21482篇 |
农作物 | 5395篇 |
水产渔业 | 6695篇 |
畜牧兽医 | 67967篇 |
园艺 | 1801篇 |
植物保护 | 8985篇 |
出版年
2020年 | 1178篇 |
2019年 | 1376篇 |
2018年 | 2032篇 |
2017年 | 2331篇 |
2016年 | 2095篇 |
2015年 | 1744篇 |
2014年 | 2224篇 |
2013年 | 5293篇 |
2012年 | 4114篇 |
2011年 | 5094篇 |
2010年 | 3246篇 |
2009年 | 3390篇 |
2008年 | 4973篇 |
2007年 | 4666篇 |
2006年 | 4355篇 |
2005年 | 4088篇 |
2004年 | 3850篇 |
2003年 | 3973篇 |
2002年 | 3543篇 |
2001年 | 4150篇 |
2000年 | 4252篇 |
1999年 | 3372篇 |
1998年 | 1474篇 |
1997年 | 1387篇 |
1996年 | 1289篇 |
1995年 | 1529篇 |
1994年 | 1358篇 |
1993年 | 1231篇 |
1992年 | 2584篇 |
1991年 | 2701篇 |
1990年 | 2591篇 |
1989年 | 2611篇 |
1988年 | 2370篇 |
1987年 | 2348篇 |
1986年 | 2427篇 |
1985年 | 2340篇 |
1984年 | 1881篇 |
1983年 | 1677篇 |
1982年 | 1149篇 |
1979年 | 1748篇 |
1978年 | 1398篇 |
1977年 | 1151篇 |
1976年 | 1212篇 |
1975年 | 1292篇 |
1974年 | 1500篇 |
1973年 | 1514篇 |
1972年 | 1405篇 |
1971年 | 1304篇 |
1970年 | 1251篇 |
1969年 | 1283篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
A. Wjtowicz 《EPPO Bulletin》2003,33(3):515-516
A computer system Agrogis has been developed to record information on pest infestation of plants in different regions of Poland. Data can be entered manually or from disks, and can be displayed in the form of charts and maps. Agrogis will be made available on the Internet. 相似文献
152.
Enzyme Immunoassays for the Determination of Ovine LH and FSH 总被引:2,自引:0,他引:2
GM Peclaris A Pappa K Deligiannis K Koutsotolis 《Reproduction in domestic animals》2003,38(5):367-372
The development of competitive enzyme immunoassays for ovine plasma LH (oLH) and FSH (oFSH) is described. Standards and plasma samples were preincubated with diluted antiserum to oLH or oFSH and the reacted solution (100 μl per well) was transferred to plates previously coated with oLH or oFSH, respectively. The second antibody used was anti‐rabbit IgG horseradish peroxidase. The measuring range was 0.39–50 ng/ml for each hormone and the 50% relative binding sensitivity was 9 ng/ml for oLH. The respective value for oFSH was 3.5 or 34 ng/ml with different hormone and antibody preparations used for the assay. The enzyme immunoassays were used to determine oLH and oFSH levels in plasma from ewes of two breeds during the oestrous cycle. The assays detected the first FSH surge coincident with the LH surge, the second FSH surge about 24 h later and the periodic fluctuations of FSH concentrations during the luteal phase of the oestrous cycle. These enzyme immunoassays are an efficient and economic alternative to the established radioimmunoassays (RIA) for oLH and oFSH. 相似文献
153.
A. T. Szabó 《Genetic Resources and Crop Evolution》2005,52(3):347
154.
155.
156.
Melody L. Danley P. Brett Kenney Patricia M. Mazik Rodney Kiser Joseph A. Hankins 《Journal of the World Aquaculture Society》2005,36(3):249-261
Rainbow trout Oncorhynchus mykiss (261.6 × 24.7 g initial weight, mean × SEM) at 13.1 × 0.2 C were exposed for 94 d to one of three CO2 treatments: control (22.1 × 2.8 mg/L), medium (34.5 × 3.8 mg/L), or high (48.7 × 4.4 mg/L). Trout were checked daily for survival, and fish were sampled at 0, 28, 56, and 84 d for physiological responses, growth, and fillet quality assessments. Trout were also challenged to a 15-min crowding stress at 93 d to assess their ability to initiate a stress response during hypercapnia. Chronically exposed trout showed nearly 100% survival through 84 d exposure (1 of 1,500 fish died). Growth and physiological results showed that increasing elevated CO2 , concentrations result in corresponding decreased growth rates and CO2 specific physiological parameters: The medium and high CO2 treatments had significantly slower growth and subsequently smaller fish by 84 d. Exposed trout also showed significantly ( P < 0.05) decreased plasma chloride for medium and high CO2 treatments compared to the control from 28 through 84 d. Decreased growth and smaller fish in the medium and high CO2 treatments resulted in correspondingly smaller fresh and smoked fillet weights. Chronic CO2 exposure did not result in notable changes in ultimate muscle pH. Exposure to 15-min crowding stress at 93 d resulted in significant changes in hematocrit, plasma cortisoI, glucose, and chloride for all treatment groups. CO2 -specific changes were detected in hematocrit, plasma cortisoI, and plasma chloride responses following the 15-min crowding stress. 相似文献
157.
P. Laffaille A. Acou J. Guillouët B. Mounaix A. Legault 《Ecology of Freshwater Fish》2006,15(4):583-588
Abstract – Changes in the numbers and size-class structure of European silver eels, Anguilla anguilla , in the River Frémur (France) were examined over a 9-year period after installation of downstream eel passes. The number of silver eels migrating downstream peaked in 1999, then decreased strongly and steadily after 2000, reaching relatively low levels. At the same time, a gradual shift in the silver eel sex ratio from a dominance of males (size from 270 to 442 mm, age from 3 to 6 years) to females (size from 366 to 1112 mm, age from 4 to 9 years) was recorded. Possible explanations for the escapement patterns observed are environmental sex determination and the installation of eel passes on the main hydraulic engineering structures in 1992 and 1996. 相似文献
158.
159.
Beth A. Valentine 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1995,9(5):291-297
A study of 57 cutaneous melanocytic tumors from 53 horses revealed 4 distinct clinical syndromes: melanocytic nevus, dermal melanoma, dermal melanomatosis, and anaplastic malignant melanoma. Melanocytic nevus and anaplastic melanoma each had histopathologic features that distinguished them from dermal melanoma and dermal melanomatosis. Dermal melanoma and dermal melanomatosis were histologically similar but could be differentiated by their clinical features. Melanocytic nevi were diagnosed in 29 horses with an average age of 5 years; they were solitary, superficial masses that occurred in both grey and nongrey horses, and in which surgical excision was generally curative. Dermal melanomas were diagnosed in 20 horses with an average age of 13 years; all horses of known coat color were grey. Eight horses with an average age of 7 years had 1 or 2 discrete dermal melanomas. Follow-up information was available for 6 horses; metastases occurred in 2 horses, and surgical excision was apparently curative in 4 horses. Dermal melanomatosis was diagnosed in 12 grey horses with an average age of 17 years; all 6 of these horses evaluated had internal metastases. In 2 aged nongrey horses with anaplastic malignant melanoma, the tumors metastasized within 1 year of diagnosis. Two tumors with features of both melanocytic nevus and dermal melanoma remained unclassified. 相似文献
160.
William F. Krise Michael A. Hendrix Wayne A. Bonney Susan E. Baker-Gordon 《Journal of the World Aquaculture Society》1995,26(4):384-389
The use of saline solutions was tested to determine their efficacy as replacements for ovarian fluid as sperm activators and to eliminate variability encountered with the use of Ovarian fluid. We tested fertilization rate of semen from eight males on Atlantic salmon Salmo salar eggs after five sperm-activating solutions and a non-activating saline were substituted for ovarian fluid. We used solutions shown acceptable for use with other salmonid species. The six solutions tested were a non sperm-activating phosphate-buffered saline (PBS, 7.2 g/L NaCl, 1.48 g/L Na2 HPO4 , 0.43 g/L K H2 PO4 ), a Tris buffer (6.99 g/L NaCl, 3.63 g/L Tris and 2.42 g/L glycine), a Borax buffer (12.2 g boric acid/L in solution 1, 76 g disodium tetraborate/L combined 100:118, then 1 L combined with 3.7 L water and 18 g NaCl), and three solutions of 9.25 g/L (125 mM) NaCl buffered to pH 6.0, 7.5, and 8.9. The latter five solutions activated sperm immediately on contact, while PBS required additional water to activate sperm. The PBS solution was the least effective (mean percent eyed eggs 37.6%) for egg fertilization. The mean percent eyed eggs for the other five saline solutions (range 78% to 86%) were not significantly different. Sperm from one male provided significantly lower egg fertilization (39.6%) when compared with the other seven males (67.2–87.4% egg fertilization). Percent egg fertilization was not related to number of live sperm cells per egg. Our results show that osmotically-balanced sperm-activation solutions, even those with a pH range from 6.0 to 8.9 provide adequate media for fertilization of Atlantic salmon eggs. Fertilization in a deactivation saline and water reactivation of sperm resulted in low egg fertilization. 相似文献