全文获取类型
收费全文 | 2278篇 |
免费 | 28篇 |
国内免费 | 42篇 |
专业分类
林业 | 173篇 |
农学 | 115篇 |
基础科学 | 48篇 |
199篇 | |
综合类 | 671篇 |
农作物 | 41篇 |
水产渔业 | 23篇 |
畜牧兽医 | 916篇 |
园艺 | 98篇 |
植物保护 | 64篇 |
出版年
2024年 | 5篇 |
2023年 | 38篇 |
2022年 | 52篇 |
2021年 | 37篇 |
2020年 | 34篇 |
2019年 | 37篇 |
2018年 | 45篇 |
2017年 | 16篇 |
2016年 | 36篇 |
2015年 | 34篇 |
2014年 | 47篇 |
2013年 | 31篇 |
2012年 | 139篇 |
2011年 | 154篇 |
2010年 | 83篇 |
2009年 | 63篇 |
2008年 | 145篇 |
2007年 | 142篇 |
2006年 | 158篇 |
2005年 | 120篇 |
2004年 | 113篇 |
2003年 | 132篇 |
2002年 | 133篇 |
2001年 | 63篇 |
2000年 | 111篇 |
1999年 | 65篇 |
1998年 | 16篇 |
1997年 | 17篇 |
1996年 | 18篇 |
1995年 | 14篇 |
1994年 | 25篇 |
1993年 | 18篇 |
1992年 | 18篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 5篇 |
1987年 | 13篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1971年 | 4篇 |
1967年 | 6篇 |
1963年 | 4篇 |
1957年 | 5篇 |
1956年 | 4篇 |
排序方式: 共有2348条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
6.
7.
A case of selenium poisoning was suspected following the administration of 325 micromol selenium a day as sodium selenate (25 mg Se) for five consecutive days. The main signs were confined to changes in the integument which were loss of hair from the mane and tail, disintegration of the skin of the anus, lips, prepuce and scrotum, and separation of the hooves from the coronary corium. Periodic analyses of blood, hair and hoof parings from the sole correlated strongly with blood and identified horn and hair as important additional routes of excretion. 相似文献
8.
Knowlen GG Kittleson MD Nachreiner RF Eyster GE 《Journal of the American Veterinary Medical Association》1983,183(9):991-996
The plasma aldosterone concentration (PAC) among clinical status groups of 23 dogs with chronic heart failure was compared at various times after diagnosis of the problem. Eighteen dogs admitted in New York Heart Association (NYHA) class IV clinical status had significant elevations in PAC (P<0.0001), when compared with clinically normal dogs. Five dogs admitted in NYHA class III status and 4 dogs that responded with a change to NYHA class III status had significant elevations in PAC (P<0.01), when compared with clinically normal dogs. In patients with NYHA class IV status, the PAC was significantly greater (P<0.01) than in patients in NYHA class III status. For patients with the poorest prognosis, ie, severe signs of NYHA class IV status, the PAC was not markedly different, when compared with that for patients with a favorable prognosis, ie, recent onset of signs of NYHA class IV status. Patients treated with captopril had significantly lower PAC after therapy (P<0.01), whereas patients treated with hydralazine had significantly higher PAC (P<0.05) after therapy. It was concluded that heart failure in the dog increases PAC, most likely because of renin-angiotensin-aldosterone-system activation, and that the increase is related directly to the clinical status of the patient. Further, it was concluded that treatment of dogs in heart failure with captopril causes a decrease in circulating PAC, whereas treatment with hydralazine causes an increase in circulating PAC. 相似文献
9.
Sources of stray electrical leakage from Power Supply Authority alternating current (AC), fence energiser pulses and randomly generated pulses and spikes on 55 dairy farms in the Waikato area were identified between December 1986 and March 1988. The electrical measurements were made using a specifically designed voltmeter able to detect voltages between 0.1V and 1500V, from single voltage spikes of two microseconds or greater duration from direct current (DC) as well as 50 Hz AC. Ninety-five sources of stray voltage were identified, and 53 per cent of properties had more than one source of >0.5V. The major source was from electric fence energisers. Rotary platform parlours were among the commonest sources of random or transient voltage spikes. Leakage of AC into one or other of the components of the milk transport system such as vat, plate cooler, milk lift pump and milk line was common. Owners acknowledged the improvements in milk production, reproductive performance and growth rate of calves after reduction of the exposure of dairy cattle to stray electrical leakage. A representative summary of five case records helps define the range of improvements that may possibly be achieved. 相似文献
10.
Magnitude of shear stress on the san andreas fault: implications of a stress measurement profile at shallow depth 总被引:1,自引:0,他引:1
A profile of measurements of shear stress perpendicular to the San Andreas fault near Palmdale, California, shows a marked increase in stress with distance from the fault. The pattern suggests that shear stress on the fault increases slowly with depth and reaches a value on the order of the average stress released during earthquakes. This result has important implications for both long- and shortterm prediction of large earthquakes. 相似文献