全文获取类型
收费全文 | 11040篇 |
免费 | 810篇 |
国内免费 | 862篇 |
学科分类
生物科学 | 12712篇 |
出版年
2023年 | 64篇 |
2022年 | 83篇 |
2021年 | 76篇 |
2020年 | 76篇 |
2019年 | 94篇 |
2018年 | 88篇 |
2017年 | 86篇 |
2016年 | 71篇 |
2015年 | 95篇 |
2014年 | 129篇 |
2013年 | 93篇 |
2012年 | 1193篇 |
2011年 | 1273篇 |
2010年 | 239篇 |
2009年 | 181篇 |
2008年 | 951篇 |
2007年 | 1009篇 |
2006年 | 971篇 |
2005年 | 812篇 |
2004年 | 812篇 |
2003年 | 781篇 |
2002年 | 694篇 |
2001年 | 562篇 |
2000年 | 638篇 |
1999年 | 278篇 |
1998年 | 50篇 |
1997年 | 57篇 |
1996年 | 59篇 |
1995年 | 33篇 |
1994年 | 46篇 |
1993年 | 48篇 |
1992年 | 48篇 |
1991年 | 58篇 |
1990年 | 39篇 |
1989年 | 48篇 |
1987年 | 38篇 |
1986年 | 30篇 |
1985年 | 31篇 |
1982年 | 25篇 |
1959年 | 28篇 |
1958年 | 52篇 |
1957年 | 61篇 |
1956年 | 57篇 |
1955年 | 46篇 |
1954年 | 43篇 |
1953年 | 37篇 |
1952年 | 31篇 |
1951年 | 29篇 |
1950年 | 24篇 |
1949年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
2.
3.
4.
丝裂霉素C(MMC)是一种抗癌的双功能烷化剂,能诱发染色体畸变和使姐妹染色单体互换率显著增高,本实验以弥猴为实验材料,探讨强烈致癌因子黄曲霉素D(AFB_1),乙型肝炎病毒(HBV)和MMC在诱发SCE时的相互关系。 四只2—3年龄的猕猴(Macaca mulatta),一只雄性猕猴按公斤体重100微克剂量肌肉注射AFB_1(溶剂为二甲亚砜),另一只雄性猕猴静脉注射乙型肝炎患者血清0.2毫升。半个月后再次静脉注射患者的全血0.5毫升。一只雌性猕猴在注射AFB_1后再按上法注射乙型肝炎患者的血清和全血。另一只雄性猕猴为对照。最后一次注射的次日,抽取静脉 相似文献
5.
6.
7.
Klainer AS 《The Western journal of medicine》1988,148(4):429-441
Obesity--defined by a body mass index above 30 kg per m2--is a major problem for affluent nations. Its prevalence is higher in North America than in Europe--between 9% and 12% of the population. Reduced energy expenditure from exercise or metabolism or both may be an important contributory factor in the development of obesity because of a failure to reduce food intake sufficiently to maintain energy balance. A high ratio of abdominal circumference relative to gluteal circumference carries a twofold or greater risk of heart attack, stroke, hypertension, diabetes mellitus, gallbladder disease, and death. The effect of increased quantities of abdominal fat is greater than that of a similar increase in total body fat on the risks of ill health associated with obesity. Genetic factors appear to contribute about 25% to its etiology. 相似文献
8.
Stromal low temperature compartment derived from the inner membrane of the chloroplast envelope 总被引:3,自引:0,他引:3 下载免费PDF全文
Leaf discs of four dicotyledonous species, when incubated at temperatures of 4 to 18°C (optimum at 12°C) for 30 or 60 minutes, responded by accumulations of membranes in the chloroplast stroma in the space between the inner membrane of the envelope and the thylakoids. The accumulated membranes, here referred to as the low temperature compartment, were frequently continuous with the envelope membrane and exhibited kinetics of formation consistent with a derivation from the envelope. Results were similar for expanding leaves of garden pea (Pisum sativum), soybean (Glycine max), spinach (Spinacia oleracea), and tobacco (Nicotiana tabacum). We suggest that the stromal low temperature compartment may be analogous to the compartment induced to form between the transitional endoplasmic reticulum and the Golgi apparatus at low temperatures. The findings provide evidence for the possibility of a vesicular transfer of membrane constituents between the inner membrane of the chloroplast envelope and the thylakoids of mature chloroplasts in expanding leaves. 相似文献
9.
10.
Two buffaloes with full-term pregnancy suffered from dystocia because the cervix did not dilate in spite of strong labour pains and other parturition signs shown by each animal. The urinary bladder, cervix, vagina and surrounding area were very firm. Dead, emphysemated fetuses were removed by caesarean in each case and anuria was also noticed. One buffalo died and the other was euthanised after surgery because it did not improve. The post-mortem examinations revealed transitional cell carcinoma of urinary bladder infiltrating the cervix, vagina and surrounding area in each case. 相似文献