全文获取类型
收费全文 | 538018篇 |
免费 | 55625篇 |
国内免费 | 440篇 |
专业分类
594083篇 |
出版年
2018年 | 5054篇 |
2017年 | 4876篇 |
2016年 | 6767篇 |
2015年 | 8423篇 |
2014年 | 10076篇 |
2013年 | 14364篇 |
2012年 | 16055篇 |
2011年 | 16707篇 |
2010年 | 11385篇 |
2009年 | 10234篇 |
2008年 | 14730篇 |
2007年 | 15309篇 |
2006年 | 14324篇 |
2005年 | 13774篇 |
2004年 | 13407篇 |
2003年 | 13055篇 |
2002年 | 12911篇 |
2001年 | 27150篇 |
2000年 | 27427篇 |
1999年 | 21139篇 |
1998年 | 6439篇 |
1997年 | 6739篇 |
1996年 | 6516篇 |
1995年 | 6025篇 |
1994年 | 5887篇 |
1993年 | 5671篇 |
1992年 | 17094篇 |
1991年 | 16700篇 |
1990年 | 16334篇 |
1989年 | 15798篇 |
1988年 | 14640篇 |
1987年 | 13698篇 |
1986年 | 12504篇 |
1985年 | 12695篇 |
1984年 | 10122篇 |
1983年 | 8801篇 |
1982年 | 6363篇 |
1981年 | 5732篇 |
1980年 | 5345篇 |
1979年 | 9561篇 |
1978年 | 7275篇 |
1977年 | 6595篇 |
1976年 | 6201篇 |
1975年 | 7161篇 |
1974年 | 7560篇 |
1973年 | 7468篇 |
1972年 | 6751篇 |
1971年 | 6022篇 |
1970年 | 5363篇 |
1969年 | 5019篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
972.
973.
974.
W Nakamura Y Nagano K Otsuka Y Nishimoto 《Comptes rendus des séances de la Société de biologie et de ses filiales》1980,174(1):104-107
The interferon inducing effect of hyperthermia was studied in normal and tumor-bearing mice. Circulating interferon was temporarily detected one day after subcutaneous transplantation of 1.6 X 10(6) Ehrlich's ascites tumor cells. Hyperthermia of 43.5 degrees C for 5 min did not induce the interferon formation in mice with or without subcutaneous tumor of the cells. These findings showed that the induction of interferon formation was not main cause of the hyperthermia-induced tumor inhibition. 相似文献
975.
Fenestrated capillaries in the ventral sebaceous gland of the Djungarian hamster, Phodopus sungorus 总被引:1,自引:0,他引:1
The ventral sebaceous gland of the Djungarian hamster is a macroscopically visible organ situated in the midventral area of the abdominal wall. It consists of densely packed acini arranged in lobules with common excretory ducts. The rich vascular network of the gland is characterized by fenestrated capillaries. Fenestrated endothelium has not yet been reported as a characteristic and regular finding within sebaceous glands. Results are discussed with regard to proliferation rate of sebocytes and the demand of fluid and nutrient supply. 相似文献
976.
N L Carteron C L Schimenti D Wofsy 《Journal of immunology (Baltimore, Md. : 1950)》1989,142(5):1470-1475
Treatment with mAb to the L3T4 Ag on Th cells can inhibit autoimmunity in mice. However, the mechanism by which anti-L3T4 inhibits autoimmunity is not known. In these studies, lupus-prone NZB/NZW F1 (B/W) mice were treated with F(ab')2 fragments of mAb to L3T4 to determine whether Th cell depletion is required for the beneficial effects of anti-L3T4. We first showed that treatment of female B/W mice with F(ab')2 anti-L3T4 from age 5 to 9 mo significantly reduced autoantibody production without depleting L3T4+ cells. However, treatment was complicated by the development of a host immune response to the rat mAb fragments. To circumvent this problem, female B/W mice were treated with a single high-dose of intact rat mAb to L3T4 (GK1.5) at age two mo. to induce immune tolerance to the mAb. Then, after recovery of L3T4+ cells, the mice were treated from age four to 14 mo with either F(ab')2 anti-L3T4 (0.5 mg 3 times per wk), intact anti-L3T4, or saline. In mice tolerized by this regimen, neither the F(ab')2 rat mAb nor the intact rat mAb elicited a host response. The mAb fragments bound target Ag but did not deplete the Th cells, whereas intact mAb to L3T4 profoundly depleted the L3T4+ cells. Despite this difference, both therapies had the same substantial beneficial effects on autoimmunity. They significantly decreased anti-DNA Ab production, improved renal function and prolonged survival. The initial tolerizing dose, by itself, did not inhibit autoimmunity. These findings show that anti-L3T4 suppresses autoimmunity by directly altering Th cell function through the L3T4 Ag, and not solely by depleting Th cells. They also document the detrimental effects of the host immune response to therapy with anti-L3T4 mAb, and they demonstrate a new strategy by which this response may be prevented. 相似文献
977.
The mass ratio of nitrous oxide reductase to total protein in the soluble protein fraction of Pseudomonas aeruginosa P2 was highest in cells grown on nitrate, decreased in cells grown on N(2)O following the exhaustion of the initial charge of nitrate, and was nearly zero in cells exposed solely to N(2)O. 相似文献
978.
In the Friuli-Venezia Giulia, a region of Italy, where serious epidemics of apple proliferation (AP) are known to occur, varieties resistant to scab (Venturia inaequalis (Cke.) Wint.) are increasingly being used in new orchards. The most important cvs are Florina. Prima and Priscilla. These varieties were cultivated according to organic farming regimes with no insecticides used. The results obtained in two orchards during a 7-year period of investigation indicated that the three varieties resistant to scab are highly susceptible to AP. Florina was most susceptible (high infection rate) to AP while Priscilla was most sensitive (severely affected). The identification of the disease was based on symptom expression, DAPI (4–6-diamidino-2-phenylindole) fluorescence technique, electron microscopy observations and by polymerase chain reaction (PCR). Neither complete spontaneous recovery nor death of AP-infected plants was noticed. The pattern of natural diffusion of AP does not seem to be uniform, the affected trees may be in line or grouped in certain spots of the orchards. This may indicate the activity of a not very mobile vector. It can be concluded that planting of Florina, Prima and Priscilla should be discouraged in areas where AP is a problem, particularly when organic farming regimes are being applied. 相似文献
979.
980.
A fluorescent probe was used to study hydrocortisone (10 microM) action on mitogen-stimulated free cytoplasmic calcium level in lymphocytes of patients with bronchial asthma. The patients were divided into two groups according to their sensitivity to glucocorticoid therapy. Hydrocortisone-specific calcium-blocking effect was absent in hormone-resistant patients. Lymphocytes of hormone-sensitive patients responded to hydrocortisone administration by a decline of mitogen-induced calcium level. 相似文献