全文获取类型
收费全文 | 54562篇 |
免费 | 4650篇 |
国内免费 | 35篇 |
出版年
2022年 | 287篇 |
2021年 | 954篇 |
2020年 | 770篇 |
2019年 | 836篇 |
2018年 | 1204篇 |
2017年 | 1007篇 |
2016年 | 1641篇 |
2015年 | 2356篇 |
2014年 | 2318篇 |
2013年 | 2896篇 |
2012年 | 3438篇 |
2011年 | 3167篇 |
2010年 | 1934篇 |
2009年 | 1882篇 |
2008年 | 2301篇 |
2007年 | 2277篇 |
2006年 | 2071篇 |
2005年 | 2381篇 |
2004年 | 2354篇 |
2003年 | 1964篇 |
2002年 | 1583篇 |
2001年 | 1471篇 |
2000年 | 1397篇 |
1999年 | 1238篇 |
1998年 | 564篇 |
1997年 | 524篇 |
1996年 | 577篇 |
1995年 | 461篇 |
1994年 | 469篇 |
1993年 | 439篇 |
1992年 | 933篇 |
1991年 | 834篇 |
1990年 | 768篇 |
1989年 | 764篇 |
1988年 | 759篇 |
1987年 | 689篇 |
1986年 | 648篇 |
1985年 | 625篇 |
1984年 | 586篇 |
1983年 | 444篇 |
1982年 | 340篇 |
1981年 | 336篇 |
1980年 | 316篇 |
1979年 | 438篇 |
1978年 | 363篇 |
1977年 | 297篇 |
1976年 | 252篇 |
1975年 | 299篇 |
1974年 | 302篇 |
1973年 | 300篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
J. A. M. van Eekelen N. Y. Rots W. Sutanto M. S. Oitzl E. R. de Kloet 《The Journal of steroid biochemistry and molecular biology》1991,40(4-6):679-683
The present study examined the stress responsiveness of the hypothalamic-pituitary-adrenal axis in relation to the properties of corticosteroid receptors in the brain and pituitary in old (30 months) and young (3 months) male Brown Norway rats. The data demonstrate that circulating ACTH rather than the corticosteroid plasma level was elevated under basal conditions and following stress. Furthermore, a reduction of mineralocorticoid receptor (MR) number in the hippocampus and of glucocorticoid receptor (GR) number in the hypothalamus and the pituitary correspond to increased neuroendocrine responsiveness and negative feedback following stress. The changes in receptor binding do not parallel the changes in the amount of MR and GR mRNA measured with in situ hybridization. This suggests that the processing rather than the receptor gene expression is affected in senescence. 相似文献
32.
I. Albesa P. Bogdanov A. Eraso N.R. Sperandeo M.M. de Bertorello 《Journal of applied microbiology》1995,78(4):373-377
I. ALBESA, P. BOGDANOV, A. ERASO, N.R. SPERANDEO AND M.M. DE BERTORELLO. 1995. The antibiotic activity of new synthetic isoxazolylnaphthoquinone imines was studied. Pseudomonas aeruginosa ATCC 27853 and Escherichia coli ATCC 25922 were resistant to the four compounds studied (MIC > 128 µg ml−1 ), but Staphylococcus aureus ATCC 25923, ATCC 29213 and 30 clinical isolates of Staph. aureus were inhibited by 2-hydroxy- N -(3,4-dimethyl-5-isoxazolyl)-1,4-naphthoquinone-4-imine (I). This compound diminished bloodstream infection of mice injected i.m. with Staph. aureus; septicaemia decayed significantly when I was applied at the beginning of the infection while when I was given 3 d after bacterial challenge, a significant protection was afforded. Bactericidal activity in serum increased during the 5 h after I was administered i.p.
The acetyl derivative of I had a high MIC but when inoculated orally in mice decreased the Staph. aureus counts in circulation. This protection occurred only when the schedule of administration started close to the bacterial challenge. Antibiotic activity in vivo may be associated with in vitro effects. 相似文献
The acetyl derivative of I had a high MIC but when inoculated orally in mice decreased the Staph. aureus counts in circulation. This protection occurred only when the schedule of administration started close to the bacterial challenge. Antibiotic activity in vivo may be associated with in vitro effects. 相似文献
33.
34.
Several strains of photoautotrophically grown Spirulina spp. contained poly-beta-hydroxybutyrate (PHB) at concentrations never exceeding a few milligrams per gram of dry weight. Under mixotrophic growth conditions in the presence of acetate, PHB reached values greater than 2.5% of dry weight. With pyruvate, no significant effect on PHB accumulation was obtained. 相似文献
35.
The production of a proteinase from Lactobacillus helveticus CRL 581 was studied. The highest specific activity was found at the early exponential growth phase of cells cultured in milk.
The lowest levels of proteinase were detected in MRS broth, while in the casein–yeast extract–glucose broth enzyme production
increased gradually during the fermentation and reached maximal values at the stationary phase. The proteinase, found to be
associated with the cell membrane fraction, hydrolyzed β-casein more rapidly than α-casein. The enzyme was not released from
washed cells in the presence or absence of calcium, which suggests that the enzyme did not undergo self-digestion.
Received: 28 January 1997 / Accepted: 8 March 1997 相似文献
36.
Herein, we report the results of irreversible inhibition of guinea pig liver transglutaminase (TGase) by a series of 24 novel dipeptides containing either an alpha,beta-unsaturated amide or an epoxide functional group. Their inactivation rate constants were measured using a direct continuous spectrophotometric method and were found to vary between 421 x 10(3) and 3000 x 10(3)M(-1)min(-1). 相似文献
37.
Predictivity of an in vitro model for acute and chronic skin irritation (SkinEthic) applied to the testing of topical vehicles 总被引:2,自引:0,他引:2
A. de Brugerolle de Fraissinette V. Picarles S. Chibout M. Kolopp J. Medina P. Burtin M.E. Ebelin S. Osborne F. K. Mayer A. Spake M. Rosdy B. De Wever R.A. Ettlin A. Cordier 《Cell biology and toxicology》1999,15(2):121-135
An in vitro human reconstructed epidermis model (SkinEthic) used for screening acute and chronic skin irritation potential
was validated against in vivo data from skin tolerability studies. The irritation potential of sodium lauryl sulfate (SLS),
calcipotriol and trans-retinoic acid was investigated. The in vitro epidermis-like model consists of cultures of keratinocytes
from human foreskin on a polycarbonate filter. The modulation of cell viability, the release and gene expression of proinflammatory
cytokines, interleukins 1α and 8, and morphological changes were evaluated during 3 days as endpoints representative for an
inflammatory reaction. The cumulative irritation potential of the topical products was evaluated in a human clinical study
by visual scoring and biophysical measurement of inflammatory skin reaction after repeated 24 h applications over 3 weeks
under Finn chamber patches. All topical products that were nonirritating in the human study were noncytotoxic and did not
induce cytokine expression in the in vitro acute model (day 1 exposure). All irritating controls exhibited specific cell viability
and cytokine patterns, which were predictive of the in vivo human data. The ranking of mild to moderate skin irritation potential
was based on the lack of cytotoxicity and the presence of cytokine patterns including gene expression specific for each irritant,
using the chronic in vitro model (up to 3 days exposure).
The human reconstructed epidermis model SkinEthic was shown to be a reliable preclinical tool predicting the irritation potential
of topical products. Moreover, it is a useful model in a two-step tiered strategy for screening acute and chronic irritation
potential for the selection of vehicles for new topical drugs.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
38.
39.