全文获取类型
收费全文 | 30380篇 |
免费 | 1284篇 |
国内免费 | 8篇 |
专业分类
林业 | 1077篇 |
农学 | 898篇 |
基础科学 | 174篇 |
4571篇 | |
综合类 | 3991篇 |
农作物 | 1175篇 |
水产渔业 | 1160篇 |
畜牧兽医 | 16493篇 |
园艺 | 340篇 |
植物保护 | 1793篇 |
出版年
2021年 | 225篇 |
2020年 | 266篇 |
2019年 | 334篇 |
2018年 | 606篇 |
2017年 | 666篇 |
2016年 | 571篇 |
2015年 | 369篇 |
2014年 | 553篇 |
2013年 | 1672篇 |
2012年 | 866篇 |
2011年 | 1121篇 |
2010年 | 817篇 |
2009年 | 763篇 |
2008年 | 1080篇 |
2007年 | 1055篇 |
2006年 | 892篇 |
2005年 | 713篇 |
2004年 | 721篇 |
2003年 | 662篇 |
2002年 | 587篇 |
2001年 | 744篇 |
2000年 | 743篇 |
1999年 | 544篇 |
1998年 | 244篇 |
1997年 | 227篇 |
1995年 | 269篇 |
1992年 | 402篇 |
1991年 | 417篇 |
1990年 | 434篇 |
1989年 | 440篇 |
1988年 | 348篇 |
1987年 | 354篇 |
1986年 | 383篇 |
1985年 | 342篇 |
1984年 | 332篇 |
1983年 | 303篇 |
1979年 | 481篇 |
1978年 | 328篇 |
1977年 | 371篇 |
1976年 | 468篇 |
1975年 | 485篇 |
1974年 | 523篇 |
1973年 | 480篇 |
1972年 | 438篇 |
1971年 | 354篇 |
1970年 | 372篇 |
1969年 | 435篇 |
1968年 | 442篇 |
1967年 | 446篇 |
1966年 | 439篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
112.
Grieco V Banco B Ferrari A Rota A Faustini M Veronesi MC 《Reproduction in domestic animals》2011,46(5):920-923
Formalin-fixed, paraffin-embedded sections from 32 canine pairs of testes were immunohistochemically examined for Inhibin-α (INHα). Samples were subdivided into two groups (group 1, neonates; group 2, puppies and adults) and results statistically compared. Inhibin-α was significantly expressed only in Sertoli cells of neonatal testes, while in Leydig cells it was expressed without significant difference between groups. These results suggest that, in dogs, INHα expression switches from Sertoli to Leydig cells during testicular maturation and that, in adult, Leydig cells represent the main source of INHα. 相似文献
113.
KELLY L. CARLSON M. KEITH CHAFFIN WAYNE V. CORAPI KAREN F. SNOWDEN DAVID G. SCHMITZ 《Veterinary radiology & ultrasound》2011,52(5):568-572
The starry sky hepatic pattern is an unusual ultrasonographic appearance of equine liver characterized by numerous small, hyperechoic foci, some of which cast an acoustic shadow, distributed randomly throughout the hepatic parenchyma. Our objectives were to describe the signalment, clinical signs, clinicopathological findings, primary disease process, and ultrasonographic findings of horses with this ultrasonographic pattern, as well as determine the associated gross and histologic changes. The starry sky pattern was identified in 18 adult horses of mixed gender and breed. The horses had various clinical signs, with weight loss and anorexia reported most commonly. Liver size and parenchymal echogenicity were normal in most horses. The hyperechoic foci frequently caused acoustic shadowing. Biliary dilation was noted rarely. The ultrasonographic pattern was the result of numerous fibrosing hepatic granulomas in all horses evaluated histologically. γ‐Glutamyltransferase was the most commonly elevated hepatic enzyme, though it was increased in fewer than half the horses. Fifteen horses had an additional disease that was identified as the apparent cause of clinical signs. Three horses had primary hepatic disease while 12 had diseases of other body systems. Therefore, the starry sky ultrasonographic pattern is likely incidental in most horses and not clinically significant. Improved recognition of this pattern and further investigation of affected horses may help refine the etiology and clinical significance of the granulomas. 相似文献
114.
Two cases of urinary bladder eversion are described in association with third-degree perineal lacerations in the mare. One case of eversion followed surgical repair of the perineal defect. The other occurred spontaneously in a 5-month postpartum mare awaiting repair of a third-degree perineal laceration. Both everted bladders contained the pelvic flexure of the large colon, and in 1 case a bladder rent allowed evisceration. Surgical intervention was required, and was successful in one case. 相似文献
115.
1. Growth of the oesophagus, proventriculus, gizzard, intestine, liver and pancreas weight was investigated in Mallards, White Pekins, Muscovies and a Muscovy x White Pekin cross. The birds varied in age between hatching and 154 d. The data were analysed by fitting both the Janoschek growth curve and the allometric formula. 2. The growth rate of all organs, except the oesophagus, peaked earlier (30 d for Muscovies and 14 d for the other breeds) than body weight and they grew faster to any given percentage of their final weight. In contrast, oesophagus weight showed growth curve characteristics similar to body weight. 3. Oesophagus weight showed simple, slightly negative allometry. The remaining organs followed complex allometry that can approximately be described by 2 allometric stages. The 1st phase was isometric to positive allometric. The 2nd showed marked negative allometry. 4. These growth patterns are assumed to be generally present in birds. 相似文献
116.
117.
V E Mendel M R Witt B S Gitchell D N Gribble Q R Rogers H J Segall H D Knight 《American journal of veterinary research》1988,49(4):572-578
Nine adult horses were fed alfalfa hay cubes containing approximately 10% Senecio vulgaris until all horses had consumed approximately the same amount of toxic components of S vulgaris, pyrrolizidine alkaloids (PA). The amount of PA consumed was determined by the amount that induced clinical signs of PA toxicosis in 3 horses. The 6 other horses were given similar amounts per kilogram of body weight. An initial decrease of feed intake was observed when horses' diets were changed from alfalfa cubes to alfalfa/Senecio cubes, and feed intake was decreased further over 89 to 98 days. From 50 to 159 days, body weight decreased in all horses. Liver disease was induced in all 9 horses after they ate an average of 233 +/- 9.2 mg of PA/kg of body weight. Eight horses died or were euthanatized. Treatment with branched chain amino acids had no effect on mortality, but appeared to reduce neurologic problems. Clinical signs of PA-induced liver disease included ataxia, head pressing, and decreased feed intake. Other clinical signs of toxicosis were observed individual horses, but did not develop in most horses. Megalocytic hepatopathy developed. Liver abnormalities proceeded as PA was consumed and were severe in 8 of 9 horses before clinical signs of toxicosis appeared. Sulfobromophthalein sodium clearance did not decrease until PA-induced liver disease was advanced. Bile acid (BA) concentrations increased to greater than or equal to 50 mumol/L, in the 8 horses that died. One horse had hepatopathy and increased BA concentration, but survived. In this horse, BA concentration peaked at 33 mumol/L and then decreased.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
118.
119.
Höglund OV Olsson K Hagman R Öhlund M Olsson U Lagerstedt AS 《Research in veterinary science》2011,91(1):159-163
The aim was to investigate if intraoperative registrations of blood pressure and heart rate could be used to estimate surgical trauma. In a prospective clinical trial, registrations in eight dogs neutered by laparoscopic ovariectomy (LOE) were compared with eight dogs subjected to open ovariohysterectomy (OHE). For comparisons phases were used: phase zero = steady state after induction of anaesthesia; phase one = opening of abdomen; phase two = severing of ovarian pedicles; and, phase three = abdominal closure. During LOE, mean systolic blood pressure increased by 7 mm Hg (p = 0.05) and 15 mm Hg (p = 0.01) from phase zero to phase one and two, respectively, and during OHE by 3 mm Hg (ns) and 29 mm Hg (p < 0.0001), respectively. The increase from phase one to phase two differed between groups (p = 0.03). Heart rate did not change. Frequent intraoperative measurements of blood pressure appear a promising method for evaluating surgical trauma. 相似文献
120.
The effect of parturition on the blood picture of sheep 总被引:1,自引:0,他引:1
Parturition in sheep was associated with significant increases in the packed cell volume, haemoglobin concentration and red cell counts. Subsequently these values gradually declined, attaining prepartum levels by the seventh day post partum. Blood leucocyte counts were also elevated at parturition and this was associated with marked neutrophilia, lymphocytopenia and mild eosinopenia. These changes were gradually reversed thereafter, with normal values being attained by the fourteenth day post partum. 相似文献