全文获取类型
收费全文 | 2140篇 |
免费 | 155篇 |
国内免费 | 16篇 |
专业分类
2311篇 |
出版年
2023年 | 21篇 |
2022年 | 33篇 |
2021年 | 53篇 |
2020年 | 42篇 |
2019年 | 40篇 |
2018年 | 70篇 |
2017年 | 69篇 |
2016年 | 91篇 |
2015年 | 113篇 |
2014年 | 117篇 |
2013年 | 149篇 |
2012年 | 160篇 |
2011年 | 170篇 |
2010年 | 89篇 |
2009年 | 76篇 |
2008年 | 70篇 |
2007年 | 103篇 |
2006年 | 83篇 |
2005年 | 61篇 |
2004年 | 56篇 |
2003年 | 65篇 |
2002年 | 57篇 |
2001年 | 51篇 |
2000年 | 53篇 |
1999年 | 43篇 |
1998年 | 20篇 |
1997年 | 9篇 |
1996年 | 16篇 |
1993年 | 7篇 |
1992年 | 26篇 |
1991年 | 28篇 |
1990年 | 12篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 15篇 |
1986年 | 12篇 |
1985年 | 22篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1975年 | 12篇 |
1974年 | 11篇 |
1973年 | 11篇 |
1972年 | 11篇 |
1971年 | 12篇 |
1967年 | 7篇 |
排序方式: 共有2311条查询结果,搜索用时 7 毫秒
1.
A Ba?sset J Cotonat P Montastruc 《Comptes rendus des séances de la Société de biologie et de ses filiales》1975,169(2):444-448
The authors have studied in the dog--normal or diabetic insipidus after hypothalamic lesion--submitted to oral ingestion of ethanol the effects of a few antidiuretic drug: chlorpropamid, atromid-S, carbamazepin and carisoprodol. The carisoprodol only can reduce the diuresis and the drinking provoked by ethanol. 相似文献
2.
We isolated a recombinant H9N2 avian influenza virus (AIV) from fresh egret feces in the Ardeidae protection region of the Dongting Lake wetland area in China, and it was designated A/Egret/Hunan/1/2012(H9N2). This is the first report of isolating H9N2 AIV from wild birds in the Dongting Lake wetland. Its eight gene segments are generated by reassortment of gene segments of different AIV subtypes. These results are helpful for understanding the epidemiology and evolution of AIV in wild birds during migration. 相似文献
3.
5''-Nucleotidases in rat heart. Evidence for the occurrence of two soluble enzymes with different substrate specificities. 总被引:7,自引:3,他引:4 下载免费PDF全文
Chromatography of soluble proteins from rat heart on phosphocellulose columns separates two 5'-nucleotidases. The first to emerge from the column shows a preference for AMP over IMP as substrate, whereas the second shows a preference for IMP over AMP. The properties of the IMP-preferring enzyme, including the conditions under which it is eluted from phosphocellulose columns, show it to be the enzyme studied by Itoh, Oka & Ozasa [Biochem. J. (1986) 235, 847-851]. The kinetic properties of the AMP-preferring enzyme indicate that it is likely to be the enzyme responsible for the production of adenosine under conditions of hypoxia and increased work load, and with metabolic stresses such as a high load of acetate. 相似文献
4.
5.
M S Ba?zhomartov S V Prozorovski? V I Vasil'eva I I Efremova M A Furman 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1979,(5):83-87
A complex of immunological cell tests with M. pneumoniae antigen (the lymphocyte blast-cell transformation test, the allergic neutrophil alteration test) was carried out in order to establish the correlation between the results of positive seroconversion and the sepcific immunological reactivity of lymphoid cells in pneumonia patients. Mycoplasmic cutireactive allergen, when used for the accelerated diagnosis of mycoplasmic pneumonia in humans, was shown to be specific and safe. Cuti-allergic tests with mycoplasmic allergen allowed to diagnose mycoplasmic pneumonia at early stages (beginning from days 5--7), which ensures the possibility of indicating etiotropic treatment to patients in due time. 相似文献
6.
Monoamine oxidase inhibitory properties of milacemide in rats 总被引:1,自引:0,他引:1
Milacemide is a glycine prodrug with reported antiepileptic antimyoclonic properties. In this study, milacemide increased "wet dog shakes" in rats pretreated with 5-Hydroxytryptophan (5-HTP) and carbidopa. Moreover, it worsened the serotonin behavior syndrome precipitated by 5-HTP and the monoamine oxidase inhibitor tranylcypromine. The serotonin syndrome was also elicited by the combination of milacemide and 5-HTP without tranylcypromine. In vitro, milacemide inhibited both monoamine oxidase A and B from the frontal cortex of rats, to a greater extent for MAO B. This drug is currently under investigation in humans as an antiepileptic agent and precautions for the consequences of monoamine oxidase inhibition should be considered when the drug is used in high doses. 相似文献
7.
J. Šťovíčková J. Turková B. Urbánek V. Bažant J. Kavalírová 《Biotechnology Techniques》1988,2(2):121-126
Summary The effect was studied of the method of drying chymotrypsin attached to bead cellulose on its chemical and physical characteristics. These characteristics are not deteriorated when replacing the commonly used lyophilisation by fluid drying in the air stream. The preparations saved essentially the same proteolytic activity as well as stability even when increasing the drying air temperature to 70°C. 相似文献
8.
9.
Normal endothelin 1/2 levels and their correlation with age were evaluated. For clinical application of the endothelin 1/2 RIA test, optimum storage conditions were investigated. Plasma endothelin 1/2 (ET) levels were measured in 36 healthy blood donors, mostly males, of mean age 36 +/- 8 years, subdivided into three age groups: 17-30, 31-40 and above 40 years old. The mean normal ET levels in the three age groups, and corresponding standard deviations, were: 0.58 +/- 0.19, 0.62 +/- 0.31, and 0.80 +/- 0.28 fmol/ml, respectively. The mean ET level for the whole normal population was 0.66 +/- 0.28 fmol/ml. Only differences between mean ET levels for the first and last groups were statistically significant (p < 0.05). Differences between mean ET levels in smokers (53% of total population) and non-smokers, women and men, irrespective of age, were found not to be statistically significant. At this stage of our work, we conclude that other factors than age alone play a role in enhancing ET levels above the age of 41 years. In our study of optimum storage conditions for endothelin 1/2, we found that after one week of storage at -24 degrees C the mean level of ET measured in frozen plasma dropped to 85% of the initial activity, while after the same period the respective decrease in ET activity in frozen extracts was 49%. Over the next two weeks, ET levels in plasma and extracts dropped to 57% and 32% of "zero time" activities, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
10.
The understanding of sex determination in general, but in particular in mammals, has been a subject of scientific speculation for a long time. It has been shown that in many vertebrate and invertebrate species, the sex of an individual is determined by the individual's chromosomal constitution. Initial studies of classical genetic searching for sex-transforming mutations and the scrupulous analyses of modified phenotypes have shed light on the mechanism(s) of sex-determination. They paved the road to successful studies at molecular level. After a brief review on sex determination in chosen model species, the “Drosophila system” is presented to exemplify a possible general principle for sex determinism. 相似文献