全文获取类型
收费全文 | 11464篇 |
免费 | 268篇 |
国内免费 | 1篇 |
专业分类
11733篇 |
出版年
2020年 | 71篇 |
2019年 | 77篇 |
2018年 | 241篇 |
2017年 | 202篇 |
2016年 | 276篇 |
2015年 | 270篇 |
2014年 | 355篇 |
2013年 | 451篇 |
2012年 | 435篇 |
2011年 | 463篇 |
2010年 | 292篇 |
2009年 | 201篇 |
2008年 | 303篇 |
2007年 | 339篇 |
2006年 | 336篇 |
2005年 | 313篇 |
2004年 | 259篇 |
2003年 | 305篇 |
2002年 | 276篇 |
2001年 | 264篇 |
2000年 | 219篇 |
1999年 | 169篇 |
1998年 | 73篇 |
1992年 | 227篇 |
1991年 | 214篇 |
1990年 | 171篇 |
1989年 | 200篇 |
1988年 | 224篇 |
1987年 | 233篇 |
1986年 | 208篇 |
1985年 | 238篇 |
1984年 | 192篇 |
1983年 | 157篇 |
1982年 | 79篇 |
1980年 | 81篇 |
1979年 | 234篇 |
1978年 | 153篇 |
1977年 | 135篇 |
1976年 | 136篇 |
1975年 | 162篇 |
1974年 | 263篇 |
1973年 | 257篇 |
1972年 | 243篇 |
1971年 | 240篇 |
1970年 | 252篇 |
1969年 | 242篇 |
1968年 | 184篇 |
1967年 | 185篇 |
1966年 | 165篇 |
1965年 | 123篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
72.
The group of aged subjects being 66 to 97 years old was compared with the middle-age group with regard to various immunological and cytochemical indices related to lymphocytes and neutrophils. The aged showed a lowered count and percentage of T cells, increased count and percentage of "non-B, non-T" lymphocytes, increased percentage of B cells. These alterations in the composition of lymphocyte subpopulation were associated with characteristic patterns of damage affecting the enzyme-positive lysosomal apparatus of lymphocytes with regard to acid phosphatase, beta-glucuronidase and N-acetyl-beta-D-glucosaminidase. There was a hundredfold smaller number of cells having intact enzyme-positive lysosomes in the aged than in the group of comparison. The changes mentioned above were also associated with the intracellular accumulation of glycogen in lymphocytes, decreased concentration of IgG and IgM in the serum and various changes in IgA concentration. Neutrophils of the aged were fewer in the blood of the aged than in younger subjects. However, an increased activity of myeloperoxidase, alkaline phosphatase, N-acetyl-beta-D-glucosaminidase, and an increased content of glycogen and lipids could be found in these cells. NBT-positive neutrophil numbers in the aged were lowered if the stimulated test was used and if there were no changes of the spontaneous test. 相似文献
73.
Pineal involvement in the regulation of adrenocortical mitotic activity has recently been suggested. It has been shown that melatonin (Mel) decreased the mean mitotic activity rate (MMAR) of the adrenal cortex both in vivo and in organ culture. The goal of the present study was to test the influence of pinealectomy (PX) and/or Mel-treatment on the MMAR of adrenocortical cells, as well as on the adrenal weight in rats. The stathmokinetic method was used in the study. It was found that PX significantly increased the MMAR of the adrenocortical cells. Moreover, Mel suppressed the proliferogenic effect of PX on the rat adrenocortical cells. Melatonin alone did not significantly affect the mitotic activity of the adrenal cortex. None of the three experimental procedures, i.e. Mel, PX and Mel-treatment of pinealectomized animals significantly affected the adrenal weight. The present data suggest that Mel may be involved in the inhibitory control of adrenocortical cell proliferation. 相似文献
74.
W Smielak-Korombel I Kulon J Szerszeń-Motyka T Wasik J Ksiazek J Polaczek-Kornecki A Wator-Brzezińska E Ceckiewicz-Swedzio? 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1992,47(40-41):913-915
The fate of young individuals (to 45 years) with a history of myocardial infarction during 12 years was analysed with the aid of a questionnaire containing questions of both social and medical character. Sudden cardiac death or the second infarction were the most frequent causes of death during the first two years following myocardial infarction. Change in the physical activity mainly involved the return to work. Only 47% of young men and 29.8% of women started full-time jobs. They mainly belonged to so-called white collars. The lack of patients' physicians permission was a main cause of the abstinence of young men from the occupation. A position within the family and social activity usually remained unchanged in the majority of patients, but every third patient greatly reduced sexual activity. Every third patients continued smoking, and did not observe recommended diet despite the systematical medical check-ups. The course of the disease is unclear in the majority of young patients. It is often deformed and requires further, detailed information on young patients' style of life. 相似文献
75.
W Tadeusiak M J Krawczyński B Balicka 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1992,47(44-45):1029-1030
Lithium concentration was determined in both sputum and blood serum of 31 patients treated with lithium carbonate. It was found that lithium concentration rate in the sputum/blood serum is 2.17 +/- 0.16, and is constant in all patients, except one, for a long time. A high correlation index between lithium concentration in the sputum and blood serum (r = 0.9025, and without two assays in the above mentioned patient r = 0.9858) as well as stability of sputum/serum lithium levels enable -- in the opinion of the authors -- to control lithium concentration in the body, using sputum for the assays. These assays are easy to perform with the aid of the kit called "Salivette" (Sarstedt, Germany). Its principle was discussed, too. 相似文献
76.
Lead chloride (10-5 M) inhibited the growth of the main root, the duration of development, the number and growth of lateral roots, primary and
trifoliate leaves, and also the mitotic index in root apical meristems. Lead strongly inhibited root growth rate, mainly by
reducing the number of dividing cells. Other mechanisms of this inhibition are discussed. 相似文献
77.
M Gajewski H Laskowska-Bozek S Ma?liński J Ryzewski 《Journal of physiology and pharmacology》1991,42(4):407-415
Isolated, cultured rat neonatal cardiac myocytes were placed in medium supplemented with mitochondrial respiratory inhibitor potassium cyanide which caused a rapid adenosine triphosphate (ATP) depletion. These myocytes with the impaired energy metabolism ("hypoxia-like state") were exposed to unstimulated human neutrophils. Effect of human neutrophils on the myocytes in the "hypoxia-like state" was quantified as a total change in the amount of ATP in cardiac cells. After 5 hours of incubation of neutrophils with the myocytes in the "hypoxia-like state" an additional decrease (of 50 per cent) in ATP content was observed. Since catalase (which destroys hydrogen peroxide) prevented the further decline in ATP level in the myocytes with impaired energy metabolism, it seem that hydrogen peroxide and possibly their products are responsible for this effect. These results suggest that unstimulated human neutrophils after activation by the contact with injured cardiac cells caused further decrease of ATP level in target cells. 相似文献
78.
M Luciak L Pawlicki J Kedziora K Trznadel J B?aszczyk A Buczyński 《Free radical biology & medicine》1991,10(6):397-401
Six chronic uremic patients on regular hemodialysis treatment were given recombinant human erythropoietin (r-huEPO) in a dose of 50 U/kg of body weight intravenously thrice weekly for 14 weeks. Following r-huEPO therapy, unstimulated whole blood superoxide anion (
2) generation did not change significantly, while opsonized zymosan-stimulated whole blood
2 generation increased. At the same time, erythrocyte superoxide dismutase and, in particular, glutathione peroxidase activities were found to be reducing with concomitant lowering of erythrocyte malonydialdehyde (MDA) concentrations and increase in plasma MDA concentrations. 相似文献
79.
80.
H. Sztajer E. Zboińska I. Zbyryt J. Kleleczawa B. Lejczak P. Kafarski 《Biologia Plantarum》1990,32(1):28-34
Two classes of phosphonopeptides, those containing P-terminal 9-aminofluoren-9-ylphos-phonic acid and those of dialkyl 9-aminofluoren-9-ylphosphine
oxides, influence plant growth according to different mechanisms. The effect of these compounds on the growth of several bacterial
species, including the photosynthetic bacteriumRhodospirillum rubrum, as well as on the activity of photosystems 1 and 2 in isolatedPisum sativum andSpirodela oligorrhiza chloroplasts was studied. The peptides of free, unblocked 9-aminofluoren-9-ylphosphonic acid acted in a morphactin-like manner,
whereas those of dialkyl 9-aminofluoren-9-ylphosphine oxides influenced photosynthesis indirectly. 相似文献