全文获取类型
收费全文 | 3618篇 |
免费 | 231篇 |
国内免费 | 1篇 |
专业分类
林业 | 112篇 |
农学 | 71篇 |
基础科学 | 15篇 |
430篇 | |
综合类 | 569篇 |
农作物 | 172篇 |
水产渔业 | 215篇 |
畜牧兽医 | 2019篇 |
园艺 | 72篇 |
植物保护 | 175篇 |
出版年
2021年 | 38篇 |
2020年 | 56篇 |
2019年 | 71篇 |
2018年 | 62篇 |
2017年 | 60篇 |
2016年 | 68篇 |
2015年 | 48篇 |
2014年 | 76篇 |
2013年 | 160篇 |
2012年 | 149篇 |
2011年 | 191篇 |
2010年 | 91篇 |
2009年 | 91篇 |
2008年 | 155篇 |
2007年 | 156篇 |
2006年 | 152篇 |
2005年 | 160篇 |
2004年 | 166篇 |
2003年 | 147篇 |
2002年 | 133篇 |
2001年 | 91篇 |
2000年 | 83篇 |
1999年 | 67篇 |
1998年 | 40篇 |
1997年 | 34篇 |
1996年 | 39篇 |
1995年 | 28篇 |
1994年 | 25篇 |
1993年 | 30篇 |
1992年 | 48篇 |
1991年 | 73篇 |
1990年 | 51篇 |
1989年 | 49篇 |
1988年 | 47篇 |
1987年 | 36篇 |
1986年 | 67篇 |
1985年 | 60篇 |
1984年 | 38篇 |
1983年 | 33篇 |
1982年 | 22篇 |
1980年 | 31篇 |
1979年 | 35篇 |
1978年 | 33篇 |
1975年 | 26篇 |
1974年 | 32篇 |
1973年 | 30篇 |
1972年 | 42篇 |
1971年 | 39篇 |
1970年 | 33篇 |
1967年 | 27篇 |
排序方式: 共有3850条查询结果,搜索用时 15 毫秒
1.
American Journal of Potato Research - 相似文献
2.
Karen R. Muñana Patricia J. Luttgen Mary Anna Thrall Thomas W. Mitchell David A. Wenger 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1994,8(2):117-121
Seven Domestic shorthair cats with a lysosomal storage disorder analogous to human Niemann-Pick disease type C, from a breeding colony were studied to characterize the neurological manifestations of this disorder. Affected cats were identified by means of liver biopsies at 4 to 6 weeks of age. Neurological examinations were performed at 2 week intervals from the onset of clinical signs. All cats displayed signs referrable to the cerebellum, with a subtle intention tremor noticed initially at 8 to 12 weeks of age; the disease was rapidly progressive. The tremor became more pronounced, menace response was lost, and severe dysmetria and ataxia developed. Three cats also had signs referrable to other areas of the central nervous system. Cats died or were euthanized between 12 and 43 weeks of age. Pathological findings included accumulation of substrate within neurons throughout the central nervous system, and axonal spheroid formation. The clinical and pathological findings in these cats are comparable to those in the human form of the disease. 相似文献
3.
D V Wilson 《Veterinary Clinics of North America: Small Animal Practice》1992,22(2):491-494
Any patient presenting for anesthesia and surgery who has a severe debilitating problem is at great risk for a prolonged recovery, renal failure, or hypotension. A stable hemodynamic state should be maintained. Fluid homeostasis should be ensured. Anesthetic induction techniques using narcotics and benzodiazepines are my preferred approach, with maintenance of anesthesia incorporating isoflurane, narcotics, or both or the use of regional anesthesia. 相似文献
4.
An experiment was conducted to examine the effect of progesterone prior to a GnRH‐PGF2α treatment on oestrus and pregnancy in seasonally anoestrous Awassi ewes. Twenty‐four ewes were randomly assigned to three groups to be pre‐treated with 60 mg medroxyprogesterone acetate sponges (group A), 600 mg progesterone sponges (group B) or blank sponges (group C) for 4 days. All ewes were injected with 100 μg of GnRH 24 h after sponge removal followed, 5 days later, by 20 mg PGF2α injection. Ewes were exposed to three fertile rams at the time of PGF2α injection (day 0, 0 h) and were checked for breeding marks at 6‐h intervals for 5 days. Blood samples were collected from all ewes 1 day (day ?10) prior to sponge insertion, at the time of sponge removal (day ?6), 1 day following sponge removal (day ?5, at the time of GnRH injection) and at the time of PGF2α injection (day 0) for analysis of progesterone. Progesterone concentrations on days ?10 and ?5 were basal and averaged 0.2 ± 0.04 and 0.2 ± 0.2 ng/ml, respectively. Progesterone concentrations on day ?6 were elevated only in group B ewes and were higher (p < 0.0001) than those of groups A and C. Progesterone concentrations on day 0 were higher (p = 0.002) in groups A and B than group C. Oestrous responses occurred only in ewes of groups A and B (p > 0.05). Induced oestrus conception rate was greater (p < 0.01) in group A than groups B and C. Ewes returned to oestrus 17–20 days following day 0 were two of eight, six of eight and three of eight of groups A, B and C, respectively, all of which eventually lambed. The overall lambing rate was 82% in progesterone‐primed ewes compared with only 38% non‐progesterone‐primed ewes (p < 0.05). Progesterone priming apparently sensitizes GnRH‐PGF2α‐treated seasonally anoestrous ewes and increases their response in oestrus and pregnancy rates. 相似文献
5.
Adult wethers (n = 750) were lot-fed for 13 days, 8 days or 3 days before a simulated voyage lasting 18 days to examine whether the period of lot-feeding affected the proportion of sheep that ate pelleted feed and their body weight change during simulated shipping. There was no significant difference in the proportion of non-feeders between treatment groups on days 7 and 14 of the voyage. Body weights were not significantly different between the treatment groups on days 14 and 18 of the voyage. Overall body weight loss, from the farm to the end of simulated shipping, was 4.08 kg (+/- 0.28, s.e.m.), 4.58 kg (+/- 0.28) and 4.51 kg (+/- 0.28) in sheep lot-fed for 13 days, 8 days and 3 days, respectively, and was not significantly different between treatments. It was concluded that lot-feeding for 13 days conferred no advantage in body weight or numbers of non-feeders compared with shorter periods in this study. 相似文献
6.
7.
The effect of exploratory laparotomy on the serum and peritoneal haptoglobin concentrations of the pony. 总被引:1,自引:0,他引:1 下载免费PDF全文
Serum haptoglobin concentration was used as an indicator of the acute phase response in ponies undergoing exploratory laparotomy. Preoperative, 1 h intraoperative, 3 h, 6 h, 12 h and 24 h postoperative blood samples and 48 h postoperative peritoneal fluid samples were obtained for haptoglobin analysis. A spectrophotometric assay based on cyanmethemoglobin binding capacity (CyanBC) was used to determine haptoglobin concentrations. The preoperative reference range for serum haptoglobin concentrations in these ponies was 25-60 mg CyanBC/dL. Intraoperative and 3 h postoperative blood samples had decreased haptoglobin concentrations when compared to preoperative values. Serum haptoglobin concentrations began to rise by the 6 h postoperative sample and were generally elevated above preoperative values by the 24 h postoperative sample. Two of the ten ponies had mild signs of postoperative colic which were associated with twofold elevations in serum haptoglobin concentrations and fivefold elevations in peritoneal fluid haptoglobin concentrations. 相似文献
8.
9.
10.