全文获取类型
收费全文 | 102694篇 |
免费 | 4832篇 |
国内免费 | 61篇 |
专业分类
林业 | 4581篇 |
农学 | 3117篇 |
基础科学 | 544篇 |
12173篇 | |
综合类 | 18908篇 |
农作物 | 4028篇 |
水产渔业 | 4387篇 |
畜牧兽医 | 52504篇 |
园艺 | 1201篇 |
植物保护 | 6144篇 |
出版年
2018年 | 1398篇 |
2017年 | 1522篇 |
2016年 | 1368篇 |
2015年 | 1096篇 |
2014年 | 1461篇 |
2013年 | 4045篇 |
2012年 | 2429篇 |
2011年 | 3037篇 |
2010年 | 2103篇 |
2009年 | 1973篇 |
2008年 | 3007篇 |
2007年 | 3014篇 |
2006年 | 2694篇 |
2005年 | 2452篇 |
2004年 | 2405篇 |
2003年 | 2356篇 |
2002年 | 2205篇 |
2001年 | 2813篇 |
2000年 | 2832篇 |
1999年 | 2286篇 |
1998年 | 921篇 |
1997年 | 895篇 |
1995年 | 1033篇 |
1993年 | 869篇 |
1992年 | 1820篇 |
1991年 | 1900篇 |
1990年 | 2019篇 |
1989年 | 2007篇 |
1988年 | 1812篇 |
1987年 | 1781篇 |
1986年 | 1852篇 |
1985年 | 1800篇 |
1984年 | 1519篇 |
1983年 | 1392篇 |
1982年 | 945篇 |
1981年 | 888篇 |
1979年 | 1665篇 |
1978年 | 1269篇 |
1977年 | 1171篇 |
1976年 | 1206篇 |
1975年 | 1355篇 |
1974年 | 1663篇 |
1973年 | 1638篇 |
1972年 | 1623篇 |
1971年 | 1465篇 |
1970年 | 1398篇 |
1969年 | 1392篇 |
1968年 | 1256篇 |
1967年 | 1303篇 |
1966年 | 1231篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
H Adam G von Lengerken D Olthoff M Schwalbe M Wicke 《Archiv fuer experimentelle veterinaermedizin》1989,43(2):293-299
Membraneous phospholipids of subcellular structures were determined from the musculature of German Landrace pigs of the GDR, following exposure to halothane. Mating variants A (H+ male X H+ female), B (H+ male X H- female), and C (H- male X H+ female) were used for positive responders (MHS), while variants B, C, and D (H- male X H- female) were used for negative responders (MHN). Four phospholipid fractions were recorded from the muscle samples for mitochondria and microsomes (according to SR section). Differences between the MHS and MHN groups for the above fractions and without consideration of mating variants and genotype were not observed, although unambiguous responses were exhibited by all animals, either positive or negative to halothan. Significant differences with regard to the above phospholipid fractions were recordable only for variant A (MHS group) as compared to D (MHN), in other words, for the homozygous genotypes, once the above results had been rearranged within MHS and MHN along with different mating variants and genotypes. However, no unambiguous results were obtainable for the heterozygous genotypes of mating variants B and C. Possible underlying reasons are discussed in some detail. The results obtained from mating variants A and D are likely to confirm earlier findings and seem to suggest that the sarcoplasmic reticulum is the primary site of origin of susceptibility to halothane or malignant hyperthermia. 相似文献
82.
The kidney's microvascularization of the Pudu pudu is mostly similar to that of domestic animals. The renal parenchymatous arteries do not give off capsular branches. The majority of the Pudu pudu's glomerula shows spherical shape. Glomerula next to the medulla have a diameter which is an average of 25 microns larger than the diameter of those situated more peripherally. Their volume is comparable to that of the angora rabbit. The capillaries form anastomosis in the inner and outer part of the glomerulus. 相似文献
83.
84.
85.
Edwin H. Robinson JamesA. Steeby J. Robert Brent 《Journal of the World Aquaculture Society》1989,20(4):256-260
Two 7 day feeding trials were conducted with channel catfish swim-up fry to evaluate growth, feed conversion ratio, and body composition of fish fed one of the following feeds: salmon starter, catfish starter, or trout starter. Fish fed the salmon or trout starter feeds gained 50–75% more weight, converted feed more efficiently, and had higher body fat stores than fish fed the catfish starter feed. This may be related to the higher protein and energy content of these two feeds. It may be advantageous to feed salmonid starter feeds to hatchery reared catfish fry; however, it is not known whether or not the improved performance observed in the hatchery continues once the fish are stocked into nursery and grow out ponds. 相似文献
86.
The anatomical-pathological findings of 15 woolly monkeys were comparable with those described in man with essential benign or malignant hypertension. Kidneys revealed arterio- and arteriolosclerosis or an onion peel-like proliferation, in some cases necrotizing endarteritis. Obesity due to restricted physical activity, unnatural feeding, and psychical and physical stress could have contributed to the development of this condition. Further, high vulnerability of the genus woolly monkey is postulated. Thus, essential hypertension of woolly monkeys appears to be a multifactorial disease. 相似文献
87.
The ultrastructure of sarcocysts of macro- and microscopic species of Sarcocystis was compared from naturally infected water buffalo from India. Grossly visible sarcocysts had walls consisting of cauliflower-like villar protrusions, typical of S. fusiformis. The sarcocyst wall of the microscopic species of Sarcocystis was 6.4 microns thick and consisted of tightly packed conical villar protrusions that were 9.6 microns long and 3.7 microns wide at the base. At approximately 3 microns above the base, the distal two-thirds of the villar protrusion became conical shaped and was bent laterally at an angle of 45 degrees to the sarcocyst surface. The granular layer beneath the villar protrusions was 0.9 microns thick. In S. levinei the granular layer was 1.9 microns thick, the villar protrusions were narrow and it had a highly undulating primary cyst wall. Whether the microscopic S. levinei-like sarcocysts of Indian and Malaysian water buffalo are distinct species of Sarcocystis will require further investigation. 相似文献
88.
Effect of pelleting and beta-glucanase supplementation on the ileal and fecal digestibility of a barley-based diet in the pig 总被引:5,自引:0,他引:5
The influences of pelleting and beta-glucanase supplementation on the digestibility of dietary components in a barley-based diet were investigated in pigs fitted with cannulas in the terminal ileum. The diet contained 49.0% starch, 18.9% crude protein and 14.8% dietary fiber, with arabinoxylans (4.9%), mixed-linked beta-glucans (3.4%) and cellulose (3.3%) as the main fiber components. Pelleting increased mixed-linked beta-glucan solubility from 45 to 62%. Neither treatment influenced the ileal or fecal apparent digestibilities of dry matter (64 and 80%, respectively), energy (62 and 79%), crude protein (53 and 75%), crude fat (26 and 27%) or dietary fiber (58 and 72%). However, pelleting increased (P less than .01) the pre-ileal apparent digestibility of starch from 91.5 to 95.3% and decreased (P less than .03) that of ash from -10 to -23%, while increasing (P less than .005) the fecal apparent digestibility of starch from 98.6 to 99.7%. The solubility of mixed-linked beta-glucans in ileal digesta was lower (P less than .001) in pelleted (26%) than in unpelleted (58%) diets. beta-glucanase supplementation also increased (P less than .05) the ileal apparent digestibility of starch, from 92.6 to 94.3%, and of mixed-linked beta-glucans, from 95.7 to 97.1%. Significant between-pig differences in the apparent digestibility of dietary components were observed. In conclusion, treatments that disrupt the endosperm cell walls in barley can increase the proportion of the diet digested prior to the large intestine. 相似文献
89.
90.
The state of mucus synthesis in the goblet cells of the small intestine was studied in conventional piglets infected with a dose of 200,000 oocytes of the coccidium Isospora suis the first and fifth day after parturition. The synthesis of mucus and its chemical characteristics undergo significant changes during the third and fourth day after infection. The activity of acid and neutral mucous substances declines; their level and the physiological synthetic function of goblet cells begin to return to the normal during the period starting on the eight to tenth day after infection. However, there were no fully functioning goblet cells in the broken numerical ratio even at the end of the period of investigation, i.e. the 13th day after infection. The thin surface layer of mucus remained almost unchanged within the whole extent of the small intestine parts studied. 相似文献