全文获取类型
收费全文 | 108202篇 |
免费 | 5693篇 |
国内免费 | 331篇 |
专业分类
林业 | 4989篇 |
农学 | 3535篇 |
基础科学 | 687篇 |
12821篇 | |
综合类 | 20230篇 |
农作物 | 4343篇 |
水产渔业 | 4933篇 |
畜牧兽医 | 54537篇 |
园艺 | 1287篇 |
植物保护 | 6864篇 |
出版年
2018年 | 1529篇 |
2017年 | 1630篇 |
2016年 | 1487篇 |
2015年 | 1293篇 |
2014年 | 1621篇 |
2013年 | 4164篇 |
2012年 | 2770篇 |
2011年 | 3359篇 |
2010年 | 2270篇 |
2009年 | 2221篇 |
2008年 | 3273篇 |
2007年 | 3178篇 |
2006年 | 2904篇 |
2005年 | 2701篇 |
2004年 | 2581篇 |
2003年 | 2625篇 |
2002年 | 2440篇 |
2001年 | 3165篇 |
2000年 | 3185篇 |
1999年 | 2561篇 |
1998年 | 1022篇 |
1997年 | 1055篇 |
1995年 | 1144篇 |
1994年 | 939篇 |
1992年 | 2016篇 |
1991年 | 2188篇 |
1990年 | 2229篇 |
1989年 | 2235篇 |
1988年 | 2052篇 |
1987年 | 2002篇 |
1986年 | 2085篇 |
1985年 | 1997篇 |
1984年 | 1625篇 |
1983年 | 1487篇 |
1982年 | 998篇 |
1981年 | 984篇 |
1979年 | 1715篇 |
1978年 | 1347篇 |
1977年 | 1164篇 |
1976年 | 1124篇 |
1975年 | 1267篇 |
1974年 | 1597篇 |
1973年 | 1643篇 |
1972年 | 1640篇 |
1971年 | 1456篇 |
1970年 | 1401篇 |
1969年 | 1352篇 |
1968年 | 1182篇 |
1967年 | 1219篇 |
1966年 | 1136篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
29 samples of commonly used surfaces were tested for their water characteristics (litre weight, water capacity, water binding, water evaporation) and their contribution to airborne fungal spores (dust formation, dust setting). The results are discussed in comparison to the literature with regard to the environment. The results are: 1. Any surface--no matter of what material--eventually causes air pollution with fungal spores and dust. 2. Correct watering prevents air pollution by any surface. 3. Artificial products have no advantage over natural materials in the parameters tested. 4. The question of proper disposal of old surface material has to be clarified before purchase. The results show that a mixture of sand and wood shavings should be recommended as a surface for indoor arenas, especially in regard to environmental protection and proper disposal. 相似文献
92.
93.
L Cauzinille J N Kornegay 《Journal of the American Veterinary Medical Association》1992,201(8):1225-1228
Acquired syringomyelia was diagnosed in an 11-year-old Fox Terrier with progressive paresis in the left pelvic limb. Myelography and magnetic resonance imaging confirmed an intramedullary lesion involving the left dorsolateral portion of the spinal cord at the level of L-2 and L-3 vertebrae. Clinical signs improved after surgical syringotomy. Microscopic evaluation of a biopsy specimen from the cyst wall did not establish a definitive histologic diagnosis. The cyst was decreased in size on magnetic resonance imaging 7 months later. 相似文献
94.
G W De Lisle D M Collins H F Huchzermeyer 《The Onderstepoort journal of veterinary research》1992,59(2):163-165
Restriction endonuclease analysis and DNA hybridization revealed five ovine strains of Mycobacterium paratuberculosis from South Africa had identical DNA patterns to an ovine strain from Canada. Genetically this strain type has features in common with the two major groups of M. paratuberculosis. 相似文献
95.
Flavonoids are important dietary constituents owing to their health-promoting properties. As a result, simplified analytic techniques are required for the population of databases with food values so that associations between dietary intake and disease risk/incidence can be established. The current research provides a simplified sample preparation procedure for the accurate estimation of food anthocyanidins, flavones, and flavonols as aglycons. Traditionally, flavonoid aglycons have been formed by acidic hydrolysis. However, some flavonoid aglycons are slowly degraded by acid. A procedure has been developed whereby anthocyanidins and flavonols are deglycosylated with HCl in 50% aqueous methanol and the resulting aglycons subsequently quantified by application of pseudo-first-order kinetics to their degradation. Flavones are also deglycosolated under similar conditions but, at appropriate temperatures, their aglycons are stable in acid, so kinetics were not required for the quantitation of this subclass of flavonoids. Catechins and flavanones were rapidly degraded under the hydrolytic conditions used in these studies. 相似文献
96.
T Nishita M Sakomoto T Ikeda H Amasaki M Shino 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(10):1147-1149
Salivary or secreted carbonic anhydrase (CA), which constitutes a new class of CA, designated CA-VI, was isolated. Swine CA-VI purified from swine saliva by inhibitor-affinity chromatography and ion exchange chromatography had a specific activity of 5,468 units/mg. The molecular weight was 250,000, as determined by gel filtration under non-denaturing conditions, and the subunit molecular weight was found to be 37,000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis, indicating that swine CA-VI consists of 7 subunits. The treatment of the enzyme with endo-N-acetylglucosaminidase F reduced its subunit molecular weight from 37,000 to 35,000 and 32,000. We raised a rabbit antibody against purfied swine CA-VI. Double immunodiffusion showed that anti-swine CA-VI serum reacted with swine CA-VI and swine saliva, but not with hemolysate (containing CA-I and CA-Il) or muscle extracts (containing CA-III). The concentration of CA-VI in swine saliva, measured using single radial immunodiffusion, was 0.027 +/- 0.017 mg/mg total protein. 相似文献
97.
Results are given of a survey on the occurrence of pathotypes (races) of Synchytrium endobioticum (potato wart) in both parts of re-unified Germany. An assortment of six differential cultivars appears to be sufficient to distinguish between the seven presently important German wart pathotypes. A total of ten pathotypes was recorded. Two West and two East German pathotypes seem to be identical, based on the results obtained with presently available cultivars. In contrast to pathotype 1 (common race) which prior to 1945 was distributed over the whole German territory, the 'new' pathotypes seem to prefer the central and south German mountain areas. 相似文献
98.
Ovarian follicular dynamics and embryo yield were studied during 2 different FSH regimens for superovulation of cattle. Twenty heifers were given intramuscular injections of FSH (total of 35 mg NIH) either once daily for 3 days (Group 3×1) or twice daily for 4 days (Group 4×2). At 72 h after the first FSH injection, each animal was injected with 0.75 mg cloprostenol. Inseminations were performed at 12 h and 24 h after the onset of heat. Transrectal ultrasonography was performed on the day of the first FSH injection, the day of cloprostenol injection, the day of insemination and finally on the day of embryo recovery (day 6 or 7 after heat). The numbers of small (2–4 mm), medium (5–9 mm) and large (>10 mm) size follicles were recorded. The total number of corpora lutea, eggs and transferable embryos were recorded on the day of embryo recovery. No differences were found between the 2 groups in either of the parameters studied (p>0.05). It can be concluded that treatment with this FSH preparation once daily for 3 days gives a folliculogenic and superovulatory response similar to a treatment regimen where it is given twice daily for 4 days. 相似文献
99.
R. N. White 《The Journal of small animal practice》1995,36(4):151-158
The surgical repair of tracheal collapse in 25 dogs is described. The initial presenting signs included coughing, dyspnoea, gagging, retching, exercise intolerance, cyanosis and collapse. Diagnosis was based upon the clinical signs, plain radiography and tracheal endoscopy. The collapse was corrected by the application of a number of extraluminal polypropylene prosthetic rings applied to the affected trachea. Additionally, a left arytenoid lateralisation was also performed. The perioperative complication rate was approximately 4 per cent, while the success rate was 75 per cent. The technique reduces the likelihood of catastrophic postoperative complications associated with iatrogenic laryngeal paralysis which is a possible complication of placement of extraluminal tracheal support devices. 相似文献
100.