全文获取类型
收费全文 | 88604篇 |
免费 | 2392篇 |
国内免费 | 45篇 |
专业分类
91041篇 |
出版年
2021年 | 209篇 |
2018年 | 1064篇 |
2017年 | 1239篇 |
2016年 | 2980篇 |
2015年 | 6439篇 |
2014年 | 6041篇 |
2013年 | 5873篇 |
2012年 | 5198篇 |
2011年 | 2386篇 |
2010年 | 2325篇 |
2009年 | 2241篇 |
2008年 | 834篇 |
2007年 | 782篇 |
2006年 | 768篇 |
2005年 | 6837篇 |
2004年 | 5518篇 |
2003年 | 3716篇 |
2002年 | 1273篇 |
2001年 | 1119篇 |
2000年 | 336篇 |
1999年 | 1500篇 |
1998年 | 382篇 |
1992年 | 1933篇 |
1991年 | 2023篇 |
1990年 | 2116篇 |
1989年 | 2005篇 |
1988年 | 1962篇 |
1987年 | 1825篇 |
1986年 | 1635篇 |
1985年 | 1664篇 |
1984年 | 1109篇 |
1983年 | 852篇 |
1982年 | 471篇 |
1981年 | 441篇 |
1980年 | 375篇 |
1979年 | 1083篇 |
1978年 | 768篇 |
1977年 | 609篇 |
1976年 | 634篇 |
1975年 | 879篇 |
1974年 | 1001篇 |
1973年 | 1011篇 |
1972年 | 956篇 |
1971年 | 930篇 |
1970年 | 821篇 |
1969年 | 831篇 |
1968年 | 739篇 |
1967年 | 753篇 |
1966年 | 584篇 |
1965年 | 431篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
A biological method was used in addition to the chemical methods of identification in the screening programme of new antibiotics. The method consists of evaluation of the effect of the crude antibiotic preparations on microbial forms resistant to various antibiotics. The efficiency of the biological method is shown. It provides more complete and rapid characterization of the properties of the new antibiotics and their rough identification at early screening stages. 相似文献
952.
B Ia Ryzhavski? 《Arkhiv anatomii, gistologii i émbriologii》1978,74(4):40-46
To elucidate factors producing destructive changes in the adrenal cortex under severe stress, the following experiments were performed: 1) severe combined stress (KC) including unilateral adrenalectomy and fixation in supin position for 24 h (control group); 2)hypophysectomy KC; 3) thyroidectomy KC; 4) bilateral orchiectomy KC; 5) injection of vitamine "E" for 14 days + KC. The adrenals were studied by a complex of morphometrical and histochemical methods. Hypophysectomy prevented estructive changes in the adrenal cortex under KC. This effect was not connected with hypofunction of the thyroid gland and the testes, as their excision (in rats without hypophysectomy) did not prevent the development of necrobiotic changes in the adrenal cortex. A suggestion is made on a "corticolytic" effect of ACTH which reveals itself under severe stress. Destruction of adrenocorticocytes is supposed to result from activation of peroxide oxidation of lipids. This is indirectly supported by a large number of lipofuscin containing cells, by decrease in the activity of alkaline phosphatase and ATPh-ase, by activation of acid phosphatase and also by decreasing alterative phenomena at the injection of vitamine "E". 相似文献
953.
Polyamines in rapid growth and cancer. 总被引:79,自引:0,他引:79
954.
P L?uger 《Biochimica et biophysica acta》1978,507(2):337-349
A formulism is described for the treatment of noise resulting from the transport of ions in channels containing an arbitrary number of activation energy barriers. The analysis is based on Nyquist's theorem and is therefore restricted to fluctuations around the equilibrium state. Within this limit the spectral intensities of current and voltage noise are given by the frequency-dependent admittance, which in turn is closely linked to the relaxation-time spectrum of the transport system. Explicit expressions for the spectral intensity of current noise are derived for channels with two and three energy barriers. The analysis may be used to predict the spectral intensity of noise from the gating system in nerve. 相似文献
955.
J Ko?cielak W Ma?liński J Zieleński E Zdebska T Brudzyński H Miller-Podraza B Cedergren 《Biochimica et biophysica acta》1978,530(3):385-393
Major neutral glycosphingolipids were isolated from human plasma and their structures and fatty acid compositions studied. The four neutral glycosphingolipids of plasma were characterized as Glc beta(1 leads to 1)ceramide, Gal beta(1 leads to 1)- ceramide, Gal beta(1 leads to 4) Glc beta (1 leads to 1)ceramide, Gal alpha(1 leads to 4) Gal beta(1 leads to 4) Glc beta(1 leads to 1)ceramide and GalNAc beta(1 leads to 3) Gal (1 leads to 4) Gal (1 leads to 4) Glc beta(1 leads to 1)-ceramide. The glycosphingolipids contained mostly short chain fatty acids of which most prominent was C16. Erythrocyte glucosylceramide and lactosylceramide exhibited similar fatty acid compositions as their plasma counterparts. Triglycosylceramide and globoside of erythrocytes contained almost exclusively long-chain fatty acids. In lactosylceramide obtained from "p" erythrocytes, an accumulation of long-chain fatty acids was found; this accumulation was not observed, however, in lactosylceramide isolated from "p" plasma. It was concluded that plasma and erythrocyte glycosphingolipids are synthesized at separate sites where short- and long-chain fatty acids, respectively, are available. Plasma and erythrocyte glucosylceramide, and probably a fraction of lactosylceramide, exchange between plasma and erythrocyte pools. The latter conclusion is discussed in the light of the relative roles of carbohydrate and lipid moieties of the glycosphingolipids in maintaining their association with erythrocyte membranes. 相似文献
956.
Mesoheme monosulfuric anhydride reacts at three distinct sites in soybean apoleghemoglobin a, at lysine-6, lysine-19 and lysine-57, the last one being the major site of reaction. The heme peptides obtained from thermolytic and pronase hydrolysates of the anhydride-leghemoglobin a were purified and correlated with the known amino acid sequence of the protein. Mesoheme bissulfuric anhydride also reacts with soybean apoleghemoglobin a giving a complex mixture of hemepeptides after hydrolysis with pronase. The visible spectrum of anhydride leghemoglobin is that of low spin heme. This suggests that anhydride leghemoglobin has a conformation with a covalent attachment via propionic acid side chain to lysine-57 and the sixth coordination position of the heme iron occupied by the distal histidine at position 61. Native leghemoglobin is assumed to exist in a similar type of configuration at low temperature, but with the heme propionate side chain being involved in a salt bridge with lysine-57. 相似文献
957.
958.
Karyometric and morphometric investigations on the thyroids of Wistar rats had the following results: complexing of methallibure (Turisynchron) with zinc lowers the inhibiting action of the parent substance on the thyroid in a short time test period. 相似文献
959.
In 25 patients having a history of acute pancreatitis (AP) in anamnesis one year ago and in 12 control subjects the insulin response to oral glucose was investigated and in some cases the exocrine function of pancreas was evaluated. The disturbances in glucose tolerance occurred in about 30% of the patients and were associated with impairment of insulin response and deterioration of exocrine pancreatic function. The double cortisone and glucose load did not influence the glucose tolerance in the patients. In persons investigated during AP and one year later only slight improvement of insulin response was noted. The results support the significance of follow-up studies of carbohydrate tolerance and insulin response in patients after AP for the evaluation of the diabetic risk in such cases. 相似文献
960.
Streptomycin uptake via an inducible polyamine transport system in Escherichia coli. 总被引:10,自引:0,他引:10
J V H?ltje 《European journal of biochemistry》1978,86(2):345-351