全文获取类型
收费全文 | 19517篇 |
免费 | 1052篇 |
国内免费 | 25篇 |
专业分类
林业 | 986篇 |
农学 | 615篇 |
基础科学 | 131篇 |
2906篇 | |
综合类 | 3076篇 |
农作物 | 1012篇 |
水产渔业 | 1155篇 |
畜牧兽医 | 9352篇 |
园艺 | 255篇 |
植物保护 | 1106篇 |
出版年
2021年 | 194篇 |
2020年 | 222篇 |
2019年 | 250篇 |
2018年 | 355篇 |
2017年 | 431篇 |
2016年 | 333篇 |
2015年 | 246篇 |
2014年 | 381篇 |
2013年 | 783篇 |
2012年 | 660篇 |
2011年 | 812篇 |
2010年 | 541篇 |
2009年 | 495篇 |
2008年 | 798篇 |
2007年 | 716篇 |
2006年 | 685篇 |
2005年 | 614篇 |
2004年 | 552篇 |
2003年 | 568篇 |
2002年 | 514篇 |
2001年 | 511篇 |
2000年 | 498篇 |
1999年 | 398篇 |
1998年 | 201篇 |
1997年 | 233篇 |
1996年 | 175篇 |
1995年 | 221篇 |
1994年 | 177篇 |
1993年 | 181篇 |
1992年 | 291篇 |
1991年 | 329篇 |
1990年 | 320篇 |
1989年 | 329篇 |
1988年 | 299篇 |
1987年 | 258篇 |
1986年 | 299篇 |
1985年 | 265篇 |
1984年 | 220篇 |
1983年 | 220篇 |
1979年 | 254篇 |
1978年 | 170篇 |
1975年 | 173篇 |
1974年 | 237篇 |
1973年 | 218篇 |
1972年 | 253篇 |
1971年 | 232篇 |
1970年 | 206篇 |
1969年 | 193篇 |
1967年 | 160篇 |
1966年 | 161篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
A conservation experiment is described in which the losses in ensiling heavily-wilted herbage, of approximately 50% dry matter, in lined trench silos, with and without a polyethylene film seal, are compared. The composition and digestibility of the silages produced in the sealed silos were comparable with those of the original herbage. The content of organic acids in the sealed silos was low, suggesting that fermentation was suppressed by the partially gas-tight seal. In the unsealed silos there was considerable spoilage, 70% of the material being inedible. In the 2 sealed silos losses of dry matter were 8·2 and 5·2% and losses of SE 11·5 and 7·8%, respectively. The losses recorded are compared with those usually encountered in lined trench silos. 相似文献
22.
23.
24.
25.
26.
27.
O Markusfeld 《The British veterinary journal》1987,143(2):119-127
28.
Taeymans O Peremans K Saunders JH 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2007,21(4):673-684
This review describes the advantages and disadvantages of radiography, ultrasonography, and nuclear medicine in the 2 most frequent thyroid pathologies of the dog: acquired primary hypothyroidism and thyroid neoplasia. Ultrasonography and scintigraphy remain the 2 most indicated imaging modalities for these thyroid abnormalities. However, as in human medicine, computed tomography and magnetic resonance imaging also have potential indications. This is especially the case in the evaluation of the extent, local invasiveness, and local or distant metastases of thyroid neoplasia. Based on experience with different imaging modalities in people, we suggest future directions in the imaging of the canine thyroid gland. 相似文献
29.
Breadmaking quality in wheat is one of several considerations that plant breeders face when developing new cultivars. In routine breeding programs, quality is assessed by small-scale dough-handling and bake tests, and to some extent, by biochemical analysis of gluten proteins. An alternative, not yet fully examined, method for wheat flour quality assessment is near-infrared reflectance (NIR) spectrophotometry. The present study was performed on 30 genotypes of hard red winter wheat grown during two crop years at eight to nine locations in the Great Plains area of the United States. Biochemical testing consisted of measuring protein fractions from size-exclusion HPLC (M r > 100k, M r 25–100k, and M r < 25k designated as glutenin, gliadins, and albumin and globulins, respectively), pentosan content, and SDS sedimentation volume. Dough-handling properties were measured on a mixograph and recorded as the time to peak dough development, the peak resistance, the width of the mixing curve, and the width of the curve at 2 min past peak. Partial least squares analyses on diffuse NIR spectra (1,100–2,498 nm) were developed for each constituent or property. When applied to a separate validation set, NIR models for glutenin content, gliadin content, SDS sedimentation volume, and mixograph peak resistance demonstrated reference vs. predicted correlations ranging from r = 0.87 to r = 0.94. Such models were considered sufficiently accurate for screening purposes in breeding programs. NIR spectra were responsive to each constituent or property at a level higher than expected from a correlation between the constituent or property and protein content (recognizing that protein content is modeled by NIR with high accuracy). 相似文献
30.
C. de Fourmestraux O. Geffroy B. Siliart O. Albaric C. Tessier 《Equine Veterinary Education》2014,26(1):34-39
The surgical success of laparoscopic castration without orchidectomy results from avascular necrosis of the testes. However, failures and subsequent production of testosterone and stallion‐like behaviour have been previously identified. Laparoscopic castration without removal of the testes was performed in 32 horses with 2 normal descended scrotal testes between July 2006 and October 2012. The objectives of our study were to evaluate the success rate of laparoscopic castration without orchidectomy on descended testes in our population and assess complications and recovery time. Endocrine tests were performed after surgery and owners also asked to report on their horse's behaviour and ability to resume exercise. Castration was deemed successful if endocrine test results were in accordance with gelding values. Failed horses were castrated using a conventional technique and histology performed when possible. Basal testosterone levels decreased below 3 nmol/l after surgery in 30/32 cases. However, in 2 horses, stallion behaviour persisted and histological evaluation after inguinal castration showed residual viable tissue. Two horses maintained high testosterone levels after surgery associated with stallion‐like behaviour. Based on these results, 12.5% of horses (4/32 horses) failed to be considered a gelding based on either endocrine tests and/or histology. All horses, with one exception, were able to resume exercise less than a week after the procedure. Laparoscopic castration without orchidectomy appears to be a safe procedure. When assessing the success of laparoscopic castration, our total failure rate was 12.5% (4/32 horses) which is significantly higher than previously reported. 相似文献