全文获取类型
收费全文 | 8411篇 |
免费 | 946篇 |
国内免费 | 1篇 |
专业分类
9358篇 |
出版年
2021年 | 103篇 |
2019年 | 69篇 |
2018年 | 111篇 |
2017年 | 104篇 |
2016年 | 143篇 |
2015年 | 269篇 |
2014年 | 287篇 |
2013年 | 381篇 |
2012年 | 424篇 |
2011年 | 423篇 |
2010年 | 280篇 |
2009年 | 228篇 |
2008年 | 372篇 |
2007年 | 409篇 |
2006年 | 354篇 |
2005年 | 368篇 |
2004年 | 325篇 |
2003年 | 304篇 |
2002年 | 296篇 |
2001年 | 168篇 |
2000年 | 177篇 |
1999年 | 143篇 |
1998年 | 125篇 |
1997年 | 123篇 |
1996年 | 104篇 |
1995年 | 97篇 |
1994年 | 116篇 |
1993年 | 101篇 |
1992年 | 162篇 |
1991年 | 129篇 |
1990年 | 113篇 |
1989年 | 120篇 |
1988年 | 109篇 |
1987年 | 128篇 |
1986年 | 97篇 |
1985年 | 137篇 |
1984年 | 144篇 |
1983年 | 106篇 |
1982年 | 125篇 |
1981年 | 115篇 |
1980年 | 102篇 |
1979年 | 93篇 |
1978年 | 65篇 |
1977年 | 70篇 |
1976年 | 79篇 |
1975年 | 63篇 |
1974年 | 76篇 |
1973年 | 65篇 |
1972年 | 57篇 |
1971年 | 55篇 |
排序方式: 共有9358条查询结果,搜索用时 0 毫秒
41.
Ninety-five yearling beef bulls were given routine Breeding Soundness Examinations, two libido tests and palpated rectally for internal genital disease and measurement of seminal vesicle size. Finger tips were premeasured, and then used as "glandometers". The bulls were examined at the end of a 140-day performance test. Sixteen lines of breeding were examined including 13 Hereford, 2 Angus and 1 Red Angus. Average age was 384 days and average weight was 961 lbs. Line and breed differences (P<.05) were observed for scrotal circumference, scrotal circumference score and second libido test. Similar differences were observed for SV length (P<.01), depth and volume both (P<.05). There were no significant correlations between seminal vesicle (SV) size and libido scores. There were, however, significant correlations between SV size and scrotal circumference (P<.05), BSE score (P<.01), body weight (P<.01), and semen morphology score (P<.05). Proximal droplets and midpiece abnormalities, respectively, were the most common spermatozoal abnormalities observed in semen from this group of bulls. 相似文献
42.
Effect of Glutaraldehyde on the Outer Layers of Escherichia coli 总被引:5,自引:4,他引:1
S ummary : Sodium lauryl sulphate (SLS) at pH 3 and 8 lysed cell walls of Escherichia coli. Pretreatment with glutaraldehyde at pH 3 and at pH 8 prevented this lysis. SLS induced maximum lysis of E. coli cells at 40°; pretreatment of cells with glutaraldehyde prevented this lysis also. Electrophoretic studies indicated that glutaraldehyde accumu lated on the surface of E. coli cells more rapidly in acid than in alkaline conditions, and that it blocked amino groups on the surface layer of Bacillus subtilis spores. The relationship of these findings to the bactericidal efficiency of glutaraldehyde in acid and alkaline solution is discussed. 相似文献
43.
44.
Two forms of the glucoamylase of Aspergillus niger 总被引:3,自引:0,他引:3
45.
46.
47.
48.
R. I. Russell 《BMJ (Clinical research ed.)》1967,3(5568):781-782
49.
1. The rate of metabolism of propionate by aged sheep-liver mitochondria in the presence of oxygen + carbon dioxide (95:5) was 5·0 (± s.e.m. 0·8) μmoles/mg. of mitochondrial N/hr. 2. When aged in the presence of the mitochondrial supernatant the rate was increased. Mitochondria from 0·33g. of liver, when combined with the corresponding mitochondrial supernatant from 0·08g. of liver, metabolized propionate at a rate of 11·4 (± s.e.m. 1·2) μmoles/mg. of mitochondrial N/hr. This rate is comparable with rates previously obtained with aged nuclear-free homogenates. 3. Two factors in the mitochondrial supernatant were detected, which when combined reproduced the effect of the fresh supernatant and prevented loss of activity on aging. One of these was non-diffusible and was recovered by fractionation of the dialysed mitochondrial supernatant with ammonium sulphate. The second factor was present in an ultrafiltrate of fresh mitochondrial supernatant and in boiled mitochondrial supernatant; it was isolated and identified as l(+)-glutamate. 4. The effect of the non-diffusible factor was due to protection of the mitochondria from the aging process, whereas glutamate served both in this capacity and as a direct stimulant of propionate metabolism at low concentration. 相似文献
50.