全文获取类型
收费全文 | 12611篇 |
免费 | 750篇 |
国内免费 | 9篇 |
专业分类
林业 | 630篇 |
农学 | 271篇 |
基础科学 | 85篇 |
1941篇 | |
综合类 | 2654篇 |
农作物 | 415篇 |
水产渔业 | 765篇 |
畜牧兽医 | 5666篇 |
园艺 | 255篇 |
植物保护 | 688篇 |
出版年
2023年 | 75篇 |
2022年 | 90篇 |
2021年 | 178篇 |
2020年 | 197篇 |
2019年 | 223篇 |
2018年 | 246篇 |
2017年 | 215篇 |
2016年 | 250篇 |
2015年 | 215篇 |
2014年 | 269篇 |
2013年 | 485篇 |
2012年 | 633篇 |
2011年 | 772篇 |
2010年 | 388篇 |
2009年 | 335篇 |
2008年 | 676篇 |
2007年 | 706篇 |
2006年 | 656篇 |
2005年 | 606篇 |
2004年 | 577篇 |
2003年 | 553篇 |
2002年 | 541篇 |
2001年 | 208篇 |
2000年 | 217篇 |
1999年 | 204篇 |
1998年 | 104篇 |
1997年 | 99篇 |
1996年 | 81篇 |
1995年 | 95篇 |
1994年 | 83篇 |
1993年 | 82篇 |
1992年 | 151篇 |
1991年 | 156篇 |
1990年 | 150篇 |
1989年 | 148篇 |
1988年 | 124篇 |
1987年 | 119篇 |
1986年 | 158篇 |
1985年 | 187篇 |
1984年 | 145篇 |
1983年 | 140篇 |
1982年 | 90篇 |
1981年 | 98篇 |
1980年 | 88篇 |
1979年 | 133篇 |
1978年 | 112篇 |
1977年 | 74篇 |
1973年 | 94篇 |
1972年 | 82篇 |
1971年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
11.
S. Leibovitch B. L. Ma Wanga E. Maloba D. L. Smith 《Journal of Agronomy and Crop Science》1992,169(3):209-215
Aspects of intensive management practices such as high-yielding cultivars, narrow-row spacings and fungicide treatments could potentially increase cereal yields in regions with a short crop-growing season and occasionally dry and hot weather. A field experiment was carried out at McGill University, Canada for three years (1987 to 1989) to test the effects of triadimefon (1-[4-chlorophenoxy]-3,3-dimethyl-1-[1H-1,2,4-triazol-1-yl]-2-butanone, or Bayleton, a trade name) fungicide (0 vs. 140 g a.i. ha−1 ) and row spacing (10 vs. 20 cm) on the yield components, yield and other agronomic traits (spike emergence, days to maturity, leaf disease and plant height) of spring barley ( Hordeum vulgare L.) cv. Cadette, Laurier and Leger. A cultivar by row spacing interaction resulted in a 11 to 13.5 % increase in grain yield due to narrow rows for Laurier in two out of the three years and up to 16 % for Leger in one year. Over the three years grain yields were on average increased 6 to 12 % due to use of the narrower row spacing. Fungicide application to barley at the early heading stage effectively controlled leaf diseases without influence on yield components or grain yield. Our results indicate that some components of intensive management such as narrow row spacing can be applicable in regions with a short crop-growing season. 相似文献
12.
13.
David E Kenny Michael R Lappin Felicia Knightly Jeffery Baler Melissa Brewer David M Getzy 《Journal of zoo and wildlife medicine》2002,33(2):131-138
In May 1996 the Denver Zoological Gardens obtained two male and two female Pallas' cats (Otocolobus felis manul) that were wild-caught in the Ukraine. These animals were part of a group of 16 wild-caught adults (eight male and eight female) imported to the United States and Canada between 1995 and 1996. The Denver Zoological Gardens cats were quarantined at the zoo hospital for approximately I mo. During the quarantine period they were immobilized for physical examination, and sera were obtained from them to evaluate for exposure to Toxoplasma gondii. All cats were positive for T. gondii antibodies by latex agglutination (titers from 1:512 to 1:1,024). After being paired for breeding, one pair produced two litters, and another pair produced four litters, a total of 17 kittens between 1997 and 2001. Four kittens and two young adults died from a disseminated granulomatous and necrotizing inflammation consistent with toxoplasmosis. Toxoplasma gondii infection was confirmed in all six deceased cats by polymerase chain reaction performed on formalin-fixed tissues. An additional five kittens disappeared and were not available for necropsy. The fatality rate from toxoplasmosis was 35.3% (6/17) for cats that were available for necropsy and could have been as high as 64.7% (11/17) if it were assumed that the disappeared kittens were also affected. The Pallas' kitten survival rate at the Denver Zoological Gardens was 35.3%. This article describes the clinical and pathologic features of toxoplasmosis in a group of Pallas' cats at the Denver Zoological Gardens. 相似文献
14.
Dominique G. Penninck DVM Antony S. Moore BVSc MVSc Amy S. Tidwell DVM Michael E. Matz DVM Greg O. Freden DVM 《Veterinary radiology & ultrasound》1994,35(4):299-306
Clinical, radiological and ultrasonographic findings from 22 cats with gastrointestinal lymphosarcoma were reviewed. The most common clinical findings were anorexia, weight loss, vomiting, lethargy, depression, fever, anemia and a palpable abdominal mass. Abdominal radiographs of 12 cats revealed a mass associated with the gastrointestinal tract and/or mesentery, and decreased serosal detail, suggestive of peritoneal effusion. The most common ultrasonographic finding was transmural gastric or intestinal thickening associated with loss of normal wall layering, reduced wall echogenicity and localized hypomotility. As is noted in people, other patterns such as transmural-segmental, transmural-nodular, transmural-bulky and mucosal infiltration were represented. In 3 cats, mesenteric lymph-adenopathy was responsible for most of the mass-effect. Fine-needle aspiration biopsy, automated microcore biopsy, endoscopic biopsy or necropsy confirmed the diagnosis of lymphosarcoma in all cats. Chemotherapy was instituted in 19 cats. Only 6 cats had a complete response to treatment. The results of this study indicate that ultrasonography is a valuable tool for the diagnosis of feline alimentary lymphosarcoma and that biopsies can be obtained under ultrasonographic guidance. 相似文献
15.
The objective of these experiments was to examine methods of modifying the fatty acid composition of bovine tissues. In the first experiment, four steers were fitted with duodenal fistulas and were assigned to four diets in a Latin square design. The steers were fed a control diet or the same diet containing 10% high-oleate partially crushed sunflower seeds, serum-coated sunflower seeds, and heat-treated, serum-coated sunflower seeds for 5 d. Samples of digesta and feces were collected on d 5. The inclusion of sunflower seeds (plain or serum-coated) in the diet increased (P less than .05) the digesta concentration of stearate. The percentage of stearate in the digesta and feces was increased (P less than .05) from 51 to 67% and from 64 to 74%, respectively, when steers were fed the untreated sunflower seed. The fecal concentration of oleate was increased (P less than .05) by dietary sunflower seeds in steers that were fed the serum-coated, unheated sunflower seeds. In a second experiment, heifers (four per group) were fed a corn-based control diet or diets containing 10% of high-oleate sunflower oil encapsulated with calcium alginate, either plain, coated with blood meal, or with blood meal integrated into the pellet. After 50 d on treatment, samples of perianal adipose tissue were obtained by biopsy. The fatty acid composition of the adipose tissue was not modified by the inclusion of the encapsulated oleate in the diet. In summary, limited ruminal bypass of sunflower seed oleate was accomplished with sunflower seed but not with encapsulated oleate. 相似文献
16.
George J. Brewer MD William Schall DVM Robert Dick BS Vilma Yuzbasiyan-Gurkan PhD Michael Thomas DVM George Padgett DVM 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1992,6(1):41-43
Inherited canine copper toxicosis is a serious problem in Bedlington terriers and West Highland White terriers, and may also be a problem in other less-studied breeds. Affected dogs become ill at midlife with progressive and ultimately fatal liver disease. Treatments for removal of copper and prevention of copper accumulation are available, but are most effective if begun before the dog becomes ill. Until recently diagnosis has not been available until the dog is 1 year of age, and then only by an invasive liver biopsy with determination of liver copper concentration. The authors studied the use of 64copper for early diagnosis of canine copper toxicosis. Two procedures were evaluated. The first involved measuring the concentration of 64copper in blood 24 hours after oral administration of the radioisotope. At this time, 64copper was associated primarily with ceruloplasmin secreted into the blood by the liver. This procedure is useful in the diagnosis of the human counterpart, Wilson's disease. However, the authors found it to be nondiscriminatory between affected and unaffected dogs. In contrast, the second procedure, which involved measuring 64copper excreted in stool during 48 hours after an intravenous dose of radioisotope, yielded results that differentiated most affected and unaffected dogs. 相似文献
17.
A selected group of pharmaceutical compounds were evaluated for the ability to inhibit the biochemical activity of fibrinoligase (coagulation factor XIIIa*) in pooled equine plasma. Criteria for the pharmaceuticals selected were based on the mechanism of the transglutamination biochemical reaction mediated by coagulation factor XIIa*. These criteria were complemented by recognition of the molecular configuration and chemical composition of amino acid residue side chains involved in the process of covalent fibrin monomer polymerization (cross-linking, transglutamination) mediated by this enzyme. Each pharmaceutical was evaluated individually and in combination with other potential coagulation factor XIIIa* inhibitors in an effort to detect additive and synergistic phenomenon. In this context, pharmaceuticals with a carbonylamide (eg, cefuroxime, Girard's reagent-P, prolinamide) were applied in concert with compounds with a terminal amine (eg, D-arginine, L-lysine) functional group. In concept, this method theoretically served to competitively simulate glutamine and lysine amino acid residues within strands of fibrin monomer substrate involved in phase I (carbonylamide) and phase II (terminal amine) of the transglutamination reaction (covalent fibrin monomer cross-linking). Halogen-dinitro and ethylene compounds were also evaluated because of their reported ability to inactivate enzyme systems dependent on an intact sulfhydryl group located at their biochemically active site (eg, cystine amino acid residue). This group of pharmaceutical compounds failed to inhibit the biochemical activity mediated by coagulation factor XIIIa* in equine plasma. 相似文献
18.
This report describes the use of 99m technetium pertechnetate (99m TcO4 − ) and 131 [for imaging of a metastatic thyroid carcinoma in a dog. The 131 ] imaging showed metastatic lesions undetected by the 99m TcO4 − imaging on 2 separate occasions. The possible mechanisms for the discrepancies between 131 I and 99m TcO4 − imaging of thyroid carcinomas are discussed. The use of 131 I for the imaging of functional thyroid carcinomas in the dog is recommended. 相似文献
19.
Matthew M. Nelson Ben D. Mooney Peter D. Nichols Charles E Phleger Greg G. Smith Piers Hart Arthur J. Ritar 《Journal of the World Aquaculture Society》2002,33(2):146-157
The lipid class and fatty acid (FA) composition of juvenile Artemia fed continuously on four diets—the microalga Tetraselmis suecica , a mix of oat bran-wheat germ-lecithin (OWL), OwL-eicosapentaenoic acid (EPA), and OWL-EPA-arachidonic acid (AA)—were examined over a 9-d experiment in an attempt to approximate the FA profile of phyllosoma larvae of wild southern rock lobster Jasus edwardrii . The main difference in lipid class composition of Artemia fed the four diets was the relative level of polar lipid (PL) and triacylglycerol (TAG). By day 9, the algal-fed Artemia were highest in PL (95% of total lipid) and lowest in TAG (2%), whereas the remaining diets resulted in Artemia with 16–30% PL and 41–82% TAG. After 2 d, the relative FA composition of all Artemia treatments closely reflected those of the diets, with no marked change after further feeding (to day 9). In terms of the content of essential polyunsaturated fatty acids (PUFA), by day 5 Artemia fed: 1) with the algal diet contained 7 mg/g FA dry mass (0.3% DHA, 6.3% EPA, 3.4% AA of total FA); 2) with the OWL diet contained 3 mg/g (0.3% DHA, 0.9% EPA, 0.7% AA); 3) with the OWL-EPA diet contained 55 mg/g (6.2% DHA, 11.6% EPA, 1.1% AA); and 4) with the OWL-EPA-AA contained 83 mg/g (3.8% DHA, 7.5% EPA, 17.4% AA). The PUFA profiles of Artemia using the OWL-oil diets were similar to wild rock lobster phyllmmata, although levels of doco-sahexaenoic acid (DHA) were lower (10% DHA) than in J. edwardsii larvae. On the basis of PUFA composition data alone, the results suggest the suitability of the OWL-oil mixed diets for consideration for feeding to Artemia used in the culture of southern rock lobster larvae, particularly if the level of DHA can be further enhanced. 相似文献
20.