全文获取类型
收费全文 | 136790篇 |
免费 | 7134篇 |
国内免费 | 81篇 |
专业分类
林业 | 6332篇 |
农学 | 4316篇 |
基础科学 | 784篇 |
15375篇 | |
综合类 | 25417篇 |
农作物 | 5334篇 |
水产渔业 | 6358篇 |
畜牧兽医 | 69745篇 |
园艺 | 1613篇 |
植物保护 | 8731篇 |
出版年
2018年 | 1648篇 |
2017年 | 1804篇 |
2016年 | 1704篇 |
2015年 | 1483篇 |
2014年 | 1820篇 |
2013年 | 4826篇 |
2012年 | 3272篇 |
2011年 | 3946篇 |
2010年 | 2647篇 |
2009年 | 2603篇 |
2008年 | 3959篇 |
2007年 | 3901篇 |
2006年 | 3598篇 |
2005年 | 3449篇 |
2004年 | 3287篇 |
2003年 | 3440篇 |
2002年 | 3185篇 |
2001年 | 3997篇 |
2000年 | 3979篇 |
1999年 | 3243篇 |
1998年 | 1318篇 |
1997年 | 1337篇 |
1995年 | 1514篇 |
1994年 | 1260篇 |
1993年 | 1306篇 |
1992年 | 2710篇 |
1991年 | 2878篇 |
1990年 | 2962篇 |
1989年 | 2947篇 |
1988年 | 2714篇 |
1987年 | 2658篇 |
1986年 | 2767篇 |
1985年 | 2668篇 |
1984年 | 2292篇 |
1983年 | 2023篇 |
1982年 | 1390篇 |
1979年 | 2191篇 |
1978年 | 1705篇 |
1977年 | 1543篇 |
1976年 | 1482篇 |
1975年 | 1609篇 |
1974年 | 2027篇 |
1973年 | 2069篇 |
1972年 | 2069篇 |
1971年 | 1922篇 |
1970年 | 1858篇 |
1969年 | 1750篇 |
1968年 | 1499篇 |
1967年 | 1605篇 |
1966年 | 1403篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
53.
K Uchio-Yamada N Manabe M Yamaguchi N Akashi Y Goto Y Yamamoto A Ogura H Miyamoto 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(11):1171-1178
Fibrotic degeneration was examined in the kidneys of ICR-derived glomerulonephritis (ICGN) mice, a novel inbred mouse line with a hereditary nephrotic syndrome of unknown etiology considered to be a good model of human idiopathic nephrotic syndrome. In the present study, we histochemically revealed changes in accumulation of extracellular matrix (ECM) components and in localization of integrins, cellular receptors for ECM, in the kidneys of ICGN mice with the progression of renal failure. Excessive accumulation of basement membrane (laminin and collagen IV) and interstitial (type III collagen) ECM components were demonstrated in the glomeruli and tubulointerstitum of ICGN mice. Marked deposition of type I collagen and tenascin was seen only in the glomeruli of ICGN mice but not in those of ICR mice as normal controls. Increased expression of integrin alpha1-, alpha2-, alpha5- and beta1-subunits in glomeruli with fibrotic degeneration and abnormal distribution of alpha6-subunit were noted in the kidneys of ICGN mice. Excessive laminin, a ligand of alpha6beta1-integrin, was demonstrated on the tubular basement membrane, but alpha6-subunit diffusely disappeared on the basal side of the tubular epithelial cells. We presumed that abnormal integrin expression in renal tubules causes epithelial cell detachment, and consequently tubular nephropathy, and results in disorder of ECM metabolism causing excessive accumulation of ECM components in the kidneys of ICGN mice. 相似文献
54.
S. J. Delaney A. S. Hill R. C. Backus G. L. Czarnecki-Maulden & Q. R. Rogers 《Journal of animal physiology and animal nutrition》2001,85(3-4):88-100
The objective of the present study was to examine the interaction between graded levels of leucine and dietary crude protein. Dose–response curves were generated using four 3 × 3 Latin squares (two dogs/square). Each square represented one of two concentrations of crude protein (140 or 280 g/kg diet) and one of two combinations of three concentrations of leucine (5.0, 7.0 and 9.0 g/kg diet or 9.0, 11 and 13 g/kg diet). An additional experiment was performed by feeding crude protein at 210 g/kg diet with either 7.0 or 11 g leucine/kg diet. Weight gain, food intake, nitrogen retention, plasma albumin and plasma amino acids were measured. The requirement was determined to be the minimum leucine concentration required to maximize weight gain and nitrogen retention. For 8–14-week-old male Beagle dogs, 140 g crude protein/kg diet in a diet containing 18 kJ metabolizable energy/g does not appear to support maximal growth. The leucine requirement was not affected by doubling the dietary crude protein level from 140 to 280 g/kg diet. From these results, the leucine requirement of 8–14-week-old Beagle dogs appears to be 11 g leucine/kg diet independent of the level of dietary crude protein, whereas dogs over 14 weeks require only 7 g leucine/kg diet for maximal nitrogen retention. 相似文献
55.
RICHARD G. HARVEY 《Veterinary dermatology》1993,4(4):175-179
Abstract— The physiology of essential fatty acid metabolism in the cat is reviewed. Emphasis is placed on those aspects of the n:6 and n:3 fatty acids, their metabolites and interactions, which relate primarily to the skin. The functional roles, if known, of the fatty acids are discussed. Recent clinical research into the use of essential fatty acid supplements in the management of feline dermatoses is presented. Current indications for the therapeutic supplementation with essential fatty acids are summarised. 相似文献
56.
J L Becht R D Park S L Kraft P F Steyn R H Wrigley 《Veterinary Clinics of North America: Equine Practice》2001,17(1):1-18
Effective radiographic interpretation requires a veterinarian who is knowledgeable of equine limb anatomy and the various principles that affect the resulting image. The normal and its variations must be recognized and understood before the abnormal can be confidently identified as pathologic. Proper patient positioning and sound radiographic technique are mandatory if reliable diagnostic radiographs are to be produced. This review emphasizes equine foot radiographic variations of normal and pseudolesions that occur with commonly used radiographic views performed in equine practice. 相似文献
57.
The technique of liver puncture as described by Holtenius (1961) was assessed with regard to its practicability and safety in a preliminary study of 26 cattle and a follow-up study of 108 German black pied cattle. The sample material was smeared, stained and examined by light microscope. All animals with changes of grade 5 had to be slaughtered. Liver puncture is a simple, quick and safe technique which supplies useful information about the various stages of hepatic fatty degeneration in individual cattle. 相似文献
58.
Abstract— An objective method for measuring corneocyte numbers before and after antiseborrheic shampoo therapy was assessed in dogs. Corneocytes were collected from six skin regions on the dorsal trunk of nine colony-raised beagles with clinically normal skin. Forty-eight collection sites were randomly assigned a treatment with one of seven medicated shampoos or water alone; six additional sites served as non-treated controls. Corneocytes were collected immediately before the first treatment, and 14 and 28 days after initiation of therapy with a 0.1% Tween 80 surfactant and a quantitative cup-scrub technique. Pretreatment corneocyte counts were not significantly different among the nine dogs nor among the randomly assigned treatment and control sites (3.55 · 104 cells.cm-2 , SEM 0.17). Corneocyte counts increased in all treatment and control sites from days 0 to 14. Corneocyte counts were similar in the non-treated and water-treated sites from days 14 to 28. Corneocyte counts were not significantly different when the same treatments were compared on days 0, 14 and 28, or when different treatments were compared on the same day. The corneocyte collection technique used in this study proved to be a reliable method for assessing the rate of cell desquamation and cell surface cohesion in dogs. 相似文献
59.
Abstract. Changes in chemical and physical properties and erodibility of a vertisol were studied in relation to land use. The vertisol, which occurs extensively in the semi-arid south-east of Zimbabwe, is derived from basalt and has a self mulching surface layer. Irrigated crops show static yields despite introduction of improved varieties. Four uncultivated sites were selected as controls and compared with five irrigated and four dryland sites. Surface soils were analysed for a range of chemical and physical properties, and laboratory rainfall simulation was used to measure soil erodibility under high intensity rain. The irrigated soils had greater exchangeable sodium and available phosphorus than the uncultivated soils. In contrast, dryland soils showed no such changes apart from a decrease in the amount of small water-stable aggregates. The soils are very erodible under high intensity rain but no significant differences were found between sites. We conclude that, although soil chemical changes have taken place in the irrigated soils, significant soil degradation has not occurred at the sites examined. The static yields probably result from management problems. However, immediate measures should be taken to improve drainage and irrigation management in the irrigated soils to avoid further sodium increases. 相似文献
60.
A ten-year-old female poodle was presented for left hindlimb lameness. Radiographically, irregular intramedullary densities of long bones (bone infarcts) and a lytic lesion in the left distal femur were detected. Two years after the first examination, the lesions in the distal femur were definitely identified as osteosarcoma and the dog was euthanized. Pathological and histological changes of the bone infarcts as well as of the osteosarcoma are described. Regarding bibliographical data, occurrence and aetiopathogenesis of osteosarcoma associated with multifocal bone infarction in man and dog are discussed. 相似文献