全文获取类型
收费全文 | 129124篇 |
免费 | 6583篇 |
国内免费 | 134篇 |
专业分类
林业 | 5369篇 |
农学 | 3411篇 |
基础科学 | 823篇 |
13671篇 | |
综合类 | 27520篇 |
农作物 | 5088篇 |
水产渔业 | 5408篇 |
畜牧兽医 | 65850篇 |
园艺 | 1395篇 |
植物保护 | 7306篇 |
出版年
2018年 | 1511篇 |
2017年 | 1665篇 |
2016年 | 1486篇 |
2015年 | 1277篇 |
2014年 | 1625篇 |
2013年 | 4161篇 |
2012年 | 3045篇 |
2011年 | 3714篇 |
2010年 | 2358篇 |
2009年 | 2431篇 |
2008年 | 3691篇 |
2007年 | 3480篇 |
2006年 | 3356篇 |
2005年 | 3220篇 |
2004年 | 3088篇 |
2003年 | 3217篇 |
2002年 | 3009篇 |
2001年 | 3511篇 |
2000年 | 3517篇 |
1999年 | 2801篇 |
1997年 | 1147篇 |
1995年 | 1286篇 |
1993年 | 1197篇 |
1992年 | 2557篇 |
1991年 | 2853篇 |
1990年 | 2799篇 |
1989年 | 2792篇 |
1988年 | 2595篇 |
1987年 | 2608篇 |
1986年 | 2730篇 |
1985年 | 2624篇 |
1984年 | 2115篇 |
1983年 | 1879篇 |
1982年 | 1326篇 |
1981年 | 1269篇 |
1980年 | 1185篇 |
1979年 | 2049篇 |
1978年 | 1644篇 |
1977年 | 1445篇 |
1976年 | 1294篇 |
1975年 | 1467篇 |
1974年 | 1941篇 |
1973年 | 1890篇 |
1972年 | 1964篇 |
1971年 | 1847篇 |
1970年 | 1796篇 |
1969年 | 1628篇 |
1968年 | 1381篇 |
1967年 | 1492篇 |
1966年 | 1313篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
W L?scher 《DTW. Deutsche tier?rztliche Wochenschrift》1992,99(2):51-54
The article considers the attractions and dangers of homeopathic therapy from the view of a pharmacologist. Homeopathic drugs may exert pharmacodynamic (but also toxic) effects at low dilutions (D0-D6), but there is no scientific proof for specific effects of higher dilutions except for substances with a high toxic potential. Most homeopathic drugs have no reasonable basis for clinical use but, in case of toxic compounds, especially those with carcinogenic or allergic potential, homeopathy may bear risks for the animal and, because of residues in food animals, also for humans. Thus, homeopathic treatment should not be used when effective conventional treatments are available, and the use of homeopathic drugs with toxic potential should be avoided. 相似文献
42.
43.
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
44.
45.
Abstract. In field and laboratory experiments the conditioner‘Agri-SC’has shown improvements in the structure of loamy sand soils in east Shropshire, UK. It resulted in statistically significant decreases in soil bulk density values and increases in soil porosity and aggregate stability. Further experiments are in progress on both loamy sand and silt loam soils. 相似文献
46.
Nephrogenic diabetes insipidus is characterized by polyuria, hyposthenuria and compensatory polydipsia. With conventional clinical and laboratory examinations the diagnosis can be established and the differential diagnostic diseases excluded. In order to verify the diagnosis, differentiate the condition from central and nephrogenic diabetes insipidus and rule out psychogenic polydipsia, additional laboratory studies are required: of these, the concentration test, modified Carter-Robbins test and AVP stimulation test are described. 相似文献
47.
48.
The horses studied were of the Swiss Warmblood breed and most were ELA-typed to assess a possible association of dermal hypersensitivity to insect bites with the major histocompatibility complex. Firstly, the occurrence of the condition was examined in 304 half-siblings sired by six stallions (A to F). Fourteen cases of dermal hypersensitivity were recognized and all were in the 153 offspring of Stallions C, E and F. Most animals of this group were also investigated for chronic hypersensitivity bronchitis: none of the sires displayed clinical signs of dermal hypersensitivity, but Stallions D, E and F were affected by chronic bronchitis. Among the animals investigated for both conditions only one horse showed coincidence of the two diseases as can be expected when the diseases are not correlated. The frequency of manifest dermal hypersensitivity and/or chronic hypersensitivity bronchitis varied in the half-sibling groups of individual sires. These findings suggest that the allergic conditions are independent entities. Secondly, the occurrence of dermal hypersensitivity was studied in three generations of horses at a stud at which Stallion C had exerted a particularly strong influence. A total of 302 animals, all born and raised at this stud, were surveyed over a period of 12 years. The descendants of Stallion C showed a significantly higher incidence (P less than 0.01) of dermal hypersensitivity (two daughters out of 19; eight second generation offspring out of 103; one third generation offspring out of 85) than did the controls of the same age classes but unrelated to Stallion C at the same stud (0 out of 95).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
49.
The study describes plumage modifications and specific feather malformations, as related to the domestication process of different poultry species. The modifications include naked necks, leg feathering, frizzle feathering, silky feathering, fat quills, and feather abnormalities caused by behavioural hypertrophies. Most of these plumage modifications correspond to the breed standard for exhibition poultry fancy. However, they impair the normal function of these animals. The negative influences comprise disorders in social behaviour, loss of typical plumage functions and disabilities of normal mobility, as well as genetic defects and pathogenic predispositions. 相似文献
50.
Plasma triglyceride concentration during intravenous infusions of propofol and Intralipid in sheep 总被引:1,自引:0,他引:1
B. M. Q. Weaver D. Raptopoulos † G. E. Staddon W. W. Mapleson‡ 《Veterinary anaesthesia and analgesia》1996,23(1):15-19
Plasma triglyceride concentrations were measured in sheep given Intralipid or propofol, which is carried in a vehicle very similar to 10% Intralipid. A bolus dose was administered followed immediately by an infusion of the same agent for 2 h. In the animals that received propofol, the measured concentration increased by a mean amount of 3.39 mmol/l when the infusion rate was l ml/min (Group Pl) and by 7.13 mmol/l when it was 2 ml/min (Group P2). When 10% Intralipid was administered and infused at 1 ml/min (Group I10), the measured concentration increased only by 0.95 mmol/l. One hour after stopping the infusion, the excess of measured concentration over baseline had decreased in the Pl and I 10 groups to 0.52 and 0.13, respectively, of the corresponding maximum excess. The method adopted for measuring plasma triglycerides is widely used in hospitals; however, an incidental observation revealed that it is inappropriate in the presence of injections of propofol or Intralipid. Despite this, evidence and argument are presented to support the conclusion that, with propofol, plasma triglyceride concentrations increased more rapidly during the infusions and returned to baseline more slowly than with a corresponding amount of Intralipid. 相似文献