全文获取类型
收费全文 | 78905篇 |
免费 | 4263篇 |
国内免费 | 93篇 |
专业分类
林业 | 3190篇 |
农学 | 2044篇 |
基础科学 | 461篇 |
8566篇 | |
综合类 | 15402篇 |
农作物 | 3136篇 |
水产渔业 | 3417篇 |
畜牧兽医 | 41739篇 |
园艺 | 856篇 |
植物保护 | 4450篇 |
出版年
2019年 | 722篇 |
2018年 | 1092篇 |
2017年 | 1211篇 |
2016年 | 1047篇 |
2015年 | 902篇 |
2014年 | 1189篇 |
2013年 | 2624篇 |
2012年 | 2111篇 |
2011年 | 2572篇 |
2010年 | 1614篇 |
2009年 | 1731篇 |
2008年 | 2596篇 |
2007年 | 2409篇 |
2006年 | 2289篇 |
2005年 | 2136篇 |
2004年 | 2080篇 |
2003年 | 2143篇 |
2002年 | 1929篇 |
2001年 | 2387篇 |
2000年 | 2442篇 |
1999年 | 1870篇 |
1998年 | 720篇 |
1997年 | 711篇 |
1996年 | 712篇 |
1995年 | 807篇 |
1993年 | 740篇 |
1992年 | 1555篇 |
1991年 | 1752篇 |
1990年 | 1635篇 |
1989年 | 1650篇 |
1988年 | 1475篇 |
1987年 | 1537篇 |
1986年 | 1598篇 |
1985年 | 1547篇 |
1984年 | 1185篇 |
1983年 | 1057篇 |
1982年 | 705篇 |
1979年 | 1154篇 |
1978年 | 897篇 |
1977年 | 755篇 |
1975年 | 776篇 |
1974年 | 1025篇 |
1973年 | 1028篇 |
1972年 | 1045篇 |
1971年 | 995篇 |
1970年 | 987篇 |
1969年 | 903篇 |
1968年 | 810篇 |
1967年 | 801篇 |
1966年 | 734篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
E. 《Forstwissenschaftliches Centralblatt》1909,31(3):182-184
Ohne Zusammenfassung 相似文献
122.
E. Knoche 《Forstwissenschaftliches Centralblatt》1904,26(7):371-393
Ohne Zusammenfassung 相似文献
123.
Three mature Quarter Horse geldings were used in 2 Latin square experiments to measure the effect of cutting and vacuum cleaning of oats on digestibility. The horses were fed at the maintenance level of digestible energy (DE) as recommended by the NRC.12The data were analyzed by Latin square analysis of variance, and Tukey's t test was used to determine any differences between specific means.No significant differences among treatments were observed during either experiment, indicating that the digestibility of nutrients from oats was not affected by cutting and vacuum cleaning. Differences in the digestibility of the ether extract (EE) fraction between periods of experiment 1 were noted. 相似文献
124.
125.
Sarah A. Slaughter Andrew D. Eitzer Sara E. Tolliver Sarah N. Holman Sara A. Colopy Seamus E. Hoey Samantha J. Loeber 《The Canadian veterinary journal. La revue veterinaire canadienne》2022,63(5):515
A 14-week-old male unilaterally cryptorchid Clumber spaniel was presented for acute lethargy. Physical examination revealed abdominal pain, and a single testis was palpated in the scrotum. Abdominal ultrasound and computed tomography (CT) revealed a poorly vascularized, ovoid structure immediately caudal to the left kidney with scant regional peritoneal effusion. Left intra-abdominal testicular torsion was confirmed at surgery, and routine cryptorchidectomy was performed. The patient recovered uneventfully from anesthesia and surgery.Key clinical message:The most common CT characteristics of testicular torsion were present in this case and correlated well with sonographic findings to allow for rapid, accurate diagnosis and surgical planning of unilateral, non-neoplastic, intra-abdominal cryptorchid testicular torsion in a juvenile dog. Contrast enhanced CT facilitated accurate localization of the undescended testis and evaluation of testicular perfusion and may be a useful alternative to ultrasound for diagnosing testicular torsion, especially in indeterminate cases. 相似文献
126.
M W Verstegen W van der Hel H A Brandsma A M Henken E Kanis P van der Wal 《Journal of animal science》1991,69(7):2961-2970
Effects of recombinant porcine somatotropin (rpST) on metabolic rate were studied in two trials with 24 crossbred barrows (Yorkshire x Landrace) in each. The barrows weighed about 80 kg (SE within trials 2.2 kg) at the start of the measurements and in each trial 12 pigs received 4 mg of rpST and 12 received a placebo. The diet contained 2.57 Mcal NE/kg and 20% CP (about 1% lysine). Animals were fed approximately 2.8 times maintenance (280 kcal ME.kg-.75.d-1). Heat production (gaseous exchange of CO2 and O2) and activity were measured continuously. Heat production associated with activity was calculated from the regression of heat production on activity. Animals treated with rpST exceeded controls in rate of gain by 252 g/d (P less than .001) and in metabolic rate by 14.5 kcal.kg-.75.d-1 (P less than .01). The rpST treatment increased rectal (+ .2 degrees C) and surface (+ .8 degrees C) temperatures. Activity-related heat production in treated pigs was increased, but this was only partly related to the increase in metabolic rate with rpST. The daily patterns of total and activity-related heat production were similar between pigs in both experimental treatments. 相似文献
127.
The conformation of the urethra, the position of the bladder neck and the distance between the external urethral orifice and the cranial pubic brim were compared in 30 continent and 30 incontinent bitches with incompetence of the urethral sphincter mechanism, using the measurements made from vagino-urethrograms. The bladder neck was significantly (P less than 0.001) further caudal in incontinent dogs than in continent dogs. Its position was not affected by neutering and could not be explained by the degree of urethral curvature. The distance from the external urethral orifice to the cranial pubic brim was correlated (P less than 0.001) with bodyweight but was not significantly different in the continent and incontinent bitches. In neutered animals, the distance between the cranial pubic brim and the external urethral orifice was significantly (P less than 0.05) shorter than in entire animals. 相似文献
128.
The capability of field-collected American dog ticks, Dermacentor variabilis, to infect horses with Ehrlichia risticii, causative agent of Potomac horse fever (PHF), was examined by allowing adult ticks collected from horse farms with a history of PHF to feed on susceptible horses. More than 500 male and female ticks attached and fed on 3 test horses; however, no clinical or serologic evidence of PHF was observed in treated or control horses. All horses were challenge exposed with E risticii-infective blood by inoculation at 60 to 65 days after ticks fed, and all developed clinical PHF with subsequent seroconversion. The data, therefore, indicated that adult D variabilis, a common parasite of horses on Maryland premises where PHF is enzootic, may not serve as a vector of E risticii. 相似文献
129.
130.