全文获取类型
收费全文 | 4255篇 |
免费 | 401篇 |
国内免费 | 1篇 |
出版年
2022年 | 45篇 |
2021年 | 92篇 |
2020年 | 49篇 |
2019年 | 67篇 |
2018年 | 71篇 |
2017年 | 68篇 |
2016年 | 95篇 |
2015年 | 157篇 |
2014年 | 207篇 |
2013年 | 251篇 |
2012年 | 300篇 |
2011年 | 346篇 |
2010年 | 203篇 |
2009年 | 173篇 |
2008年 | 189篇 |
2007年 | 193篇 |
2006年 | 135篇 |
2005年 | 171篇 |
2004年 | 173篇 |
2003年 | 144篇 |
2002年 | 138篇 |
2001年 | 77篇 |
2000年 | 74篇 |
1999年 | 66篇 |
1998年 | 58篇 |
1997年 | 30篇 |
1996年 | 39篇 |
1995年 | 44篇 |
1994年 | 33篇 |
1993年 | 37篇 |
1992年 | 47篇 |
1991年 | 46篇 |
1990年 | 46篇 |
1989年 | 56篇 |
1988年 | 50篇 |
1987年 | 28篇 |
1986年 | 33篇 |
1985年 | 45篇 |
1984年 | 37篇 |
1983年 | 41篇 |
1982年 | 31篇 |
1981年 | 29篇 |
1979年 | 39篇 |
1978年 | 23篇 |
1976年 | 31篇 |
1975年 | 21篇 |
1974年 | 23篇 |
1973年 | 28篇 |
1971年 | 28篇 |
1970年 | 29篇 |
排序方式: 共有4657条查询结果,搜索用时 156 毫秒
61.
Total skin collagen is greatly increased in women with hirsuties. This is presumably due to androgen, whether locally produced or circulating. 相似文献
62.
J. L. Burton W. J. Cunliffe D. G. Millar Sam Shuster 《BMJ (Clinical research ed.)》1970,2(5712):769-771
Sebum excretion rates from forehead skin were measured serially during and after pregnancy in 10 normal women. Only minor fluctuations occurred during the middle and last trimesters of pregnancy, but there was a pronounced decrease in the postpartum period. Probably a powerful sebotrophic factor is present in pregnancy, but its nature is conjectural. 相似文献
63.
A Comparator Method of Assessing Bacterial Plate Counts 总被引:1,自引:1,他引:0
64.
65.
Genetic relatedness among six bacterial strains currently classified as vibrios was determined by biochemical tests, deoxyribonucleic acid base composition analysis, and the detection of nucleic acid homology by the membrane filter method. Varying degrees of genetic homology existed among vibrios having similar base compositions. The bovine isolate which had a substantially different per cent guanine plus cytosine content was shown to be genetically different from the remaining vibrio strains. The use of nucleic acid homology studies in classifying vibrio strains is discussed. 相似文献
66.
Decarboxylation rates for a series of C-3 to C-6 alpha-keto acids were determined in the presence of resting cells and cell-free extracts of Streptococcus lactis var. maltigenes. The C-5 and C-6 acids branched at the penultimate carbon atom were converted most rapidly to the respective aldehydes in the manner described for alpha-carboxylases. Pyruvate and alpha-ketobutyrate did not behave as alpha-carboxylase substrates, in that O(2) was absorbed when they were reacted with resting cells. The same effect with pyruvate was noted in a nonmalty S. lactis, accounting for CO(2) produced by some "homofermentative" streptococci. Mixed substrate reactions indicated that the same enzyme was responsible for decarboxylation of alpha-ketoisocaproate and alpha-ketoisovalerate, but it appeared unlikely that this enzyme was responsible for the decarboxylation of pyruvate. Ultrasonic disruption of cells of the malty culture resulted in an extract inactive for decarboxylation of pyruvate in the absence of ferricyanide. Dialyzed cell-free extracts were inactive against all keto acids and could not be reactivated. 相似文献
67.
Various attempts to define the concept of “mental health” are examined. Value judgments permeate much mental health literature. Their use militates against obtaining an objective definition, capable of universal application. The acceptance of a definition including a value judgment implies taking an attitude toward a particular society and its social ideals.Present limits of competence only allow us to describe “mental health” conceptually. Such “untechnical” proposals are liable to be confused with “technical” (“scientific”) propositions. Multiple criteria are likely to be helpful in improving our concept of “mental health”.The intrusion of morals into the world of health is discussed as part of the contemporary intellectual dilemma of determined human behaviour versus human responsibility and the reality of moral values.It is suggested that “mental health” might consist simply of an individual''s possession of insight into his own personality, combined with an honest recognition and acceptance of his condition. 相似文献
68.
Laszlo Ambrus Sam H. Thal Selig B. Weinstein Juanita Warnecke 《The Western journal of medicine》1967,106(5):354-358
Following a six-week program of training in a series of exercises, a significant number of patients with chronic obstructive pulmonary emphysema showed decided improvement in functional activity. Subjective improvement also was noted and kept the patient motivation high.Preliminary observations indicated that the improvement could be maintained long after the end of the training period. 相似文献
69.
The de-repression of thiamine biosynthesis by adenosine. A tool for investigating this biosynthetic pathway 总被引:6,自引:3,他引:3
1. Growth of Salmonella typhimurium LT2 in the presence of adenosine was shown to cause enormous synthesis of thiamine in washed-cell suspensions. 2. Evidence that this was due to de-repression and not an accumulation of precursors was obtained by using a mutant blocked in the biosynthesis of the thiazole moiety, which showed a similarly large synthesis of the pyrimidine of thiamine. 3. The specific requirements for a source of energy, nitrogen and sulphur were investigated, and indicated new synthesis in this system. 相似文献
70.