全文获取类型
收费全文 | 19866篇 |
免费 | 1482篇 |
国内免费 | 4篇 |
出版年
2023年 | 147篇 |
2022年 | 262篇 |
2021年 | 553篇 |
2020年 | 436篇 |
2019年 | 525篇 |
2018年 | 612篇 |
2017年 | 592篇 |
2016年 | 798篇 |
2015年 | 1137篇 |
2014年 | 1165篇 |
2013年 | 1484篇 |
2012年 | 1650篇 |
2011年 | 1521篇 |
2010年 | 1040篇 |
2009年 | 896篇 |
2008年 | 1121篇 |
2007年 | 1090篇 |
2006年 | 960篇 |
2005年 | 863篇 |
2004年 | 807篇 |
2003年 | 692篇 |
2002年 | 677篇 |
2001年 | 249篇 |
2000年 | 210篇 |
1999年 | 188篇 |
1998年 | 177篇 |
1997年 | 137篇 |
1996年 | 111篇 |
1995年 | 126篇 |
1994年 | 82篇 |
1993年 | 80篇 |
1992年 | 99篇 |
1991年 | 81篇 |
1990年 | 59篇 |
1989年 | 54篇 |
1988年 | 82篇 |
1987年 | 56篇 |
1986年 | 43篇 |
1985年 | 44篇 |
1984年 | 47篇 |
1983年 | 44篇 |
1982年 | 40篇 |
1981年 | 38篇 |
1980年 | 25篇 |
1979年 | 25篇 |
1978年 | 20篇 |
1977年 | 21篇 |
1976年 | 25篇 |
1975年 | 23篇 |
1974年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
91.
92.
H. M. Canelas F. B. De Jorge W. C. Pereira J. Sallum 《Journal of neurochemistry》1968,15(12):1455-1461
Abstract— Twenty-nine autopsy specimens of intracerebral tumours (nine astrocytomata, ten medulloblastomata and ten glioblastomata multiforme), as well as samples of peritumoral and apparently normal brain tissue, have been studied for Na, K, P, Ca, Mg, Cu, and S contents.
The tumour tissue, irrespective of the histological characteristics, as compared to the 'normal' and perineoplastic tissues, showed higher concentration of Ca, Mg, Cu and S. The peritumoral tissue, regardless of the tumour type, showed a higher concentration of Cu than the 'normal' control brain.
The more malignant glioblatomata and medulloblastomata. The Cu levels did not show a significant diference. 相似文献
The tumour tissue, irrespective of the histological characteristics, as compared to the 'normal' and perineoplastic tissues, showed higher concentration of Ca, Mg, Cu and S. The peritumoral tissue, regardless of the tumour type, showed a higher concentration of Cu than the 'normal' control brain.
The more malignant glioblatomata and medulloblastomata. The Cu levels did not show a significant diference. 相似文献
93.
Isolation of an internal component from adenovirus type 5 总被引:11,自引:0,他引:11
94.
A. S. Rodrigues Pereira 《Planta》1968,80(4):349-358
Summary Staminate flowers of the Acorn squash (Cucurbita pepo, cv. Table Queen) are initiated monosexually, pistillate flowers are initiated bisexually. Pistillate flower primordia are physiologically bisexual from a stage below 0.3 mm until they are 0.8 mm in width.Male and female floral buds were cultivated on White's medium, modified according to Galun et al. (1963). In excised female floral buds the relative development of stamens is better than in in-situ floral buds; the opposite relationship holds for ovary development. The smaller the bud at excision, the greater the stamen growth and the lesser the ovary growth, both in absolute and relative terms. Although smaller pistillate floral buds cultured in vitro showed a greater increase in maleness than larger ones, there was no difference in the percentage of female buds between explants of the two sizes when originating from the mixed stem region (that is, the stem region carrying male and female flowers). Addition of 3-indoleacetic acid and the anti-auxin p-chlorophenoxyisobutyric acid to standard medium in equal amounts resulted in somewhat better development of excised floral buds than addition of each of these compounds alone.The percentage of female buds among explants originating from identical nodes was not significantly influenced by 3-indoleacetic acid or p-chlorophenoxyisobutyric acid.Weizmann Memorial Fellow. The studies reported in this publication were mainly undertaken at the Weizmann Institute of Science 相似文献
95.
96.
Twenty-two patients with chronic productive bronchitis or bronchiectasis were treated by direct instillations of normal saline and N-acetylcysteine into the trachea through a percutaneous catheter following a period of conventional routine therapy.The instillation, using either normal saline or varying concentrations of N-acetylcysteine did not produce significant change in alveolar gas exchange as reflected by measurement of arterial PaCO2 and the alveolar arterial gradient for oxygen during and after the introduction of the medication into the bronchial tree. Studies were carried out after patients had been stabilized breathing pure oxygen on an IPPB machine for 30 minutes.Evaluation of the treatment by means of pulmonary function tests demonstrated significant improvement in overall function following therapy.The results indicate that the technique of tracheobronchial lavage is physiologically benign and that overall improvement in pulmonary function can be obtained by this means in cases of the type described in this study. 相似文献
97.
Jorge Briozzo Lidia Núncez Jorge Chirife León Herszage Miguel D'aquino 《Journal of applied microbiology》1989,66(1):69-75
Essential oil of clove, dispersed (0.4%v/v) in a concentrated sugar solution, had a marked germicidal effect against various bacteria and Candida albicans. Staphyloccus aureus (five strains), Klebsiella pneumoniae, Pseudomonas aeruginosa, Clostridium perfringens , and Escherichia coli inoculated at a level of 107 cfu/ml, and C. albicans (inoculum 4.0×105 cfu/ml) were killed (< 99.999%) after 2–7 min in a laboratory broth supplemented with 63% (v/w) of sugar, and containing 0.4% (v/w) of essential oil of clove. Added organic matter (i.e. human or bovine serum) did not impair its antimicrobial activity.
Sugar was not necessary for the antimicrobial activity of clove oil, but the concentrated sugar solution provided a good vehicle for obtaining an oil dispersion that is relatively stable for certain practical applications. 相似文献
Sugar was not necessary for the antimicrobial activity of clove oil, but the concentrated sugar solution provided a good vehicle for obtaining an oil dispersion that is relatively stable for certain practical applications. 相似文献
98.
Sirlei D. Pereira Osvaldo Marinotti Antonio G. de Bianchi 《Archives of insect biochemistry and physiology》1989,11(4):245-255
During vitellogenesis in Musca domestica, a major hemolymph protein, in addition to vitellogenin, appears preferentially in females. This protein is synthesized by the adult fat bodies, secreted into the hemolymph, and is not taken up by the ovaries during vitellogenesis. We have designated this protein nonvitellogenic female protein (NVFP). It is composed of only one type of polypeptide (Mr=70,000) and occurs in two different forms. Synthesis of NVFP is induced by a protein diet, attaining maximum concentrations in females at the middle of the gonotrophic cycle. In males its maximum concentration never surpasses 10% of the concentration in females. The quantitative variation of the NVFP is cyclic and coincident with the gonotrophic cycles of Musca domestica. 相似文献
99.
CAP 37, a 37 kD human neutrophil granule cationic protein shares homology with inflammatory proteinases 总被引:6,自引:0,他引:6
H A Pereira J K Spitznagel J Pohl D E Wilson J Morgan I Palings J W Larrick 《Life sciences》1990,46(3):189-196
We have previously shown that a major granule-associated cationic protein CAP 37 (Mr = 37 kD) derived from human PMN is a monocyte-specific chemoattractant. The N-terminal amino acid sequence of this novel chemotactic protein shares significant homology with a number of inflammatory molecules with protease activity including elastase and cathepsin G. However, a critical substitution of a serine for a histidine at position 41, results in its lack of serine protease activity. 相似文献
100.
Between November and December 1987, 201 subjects from three communities of the Cordillera Province, Santa Cruz Department, South-East Bolivia (Camiri, Boyuibe, and Gutierrez) were examined for serum iron levels. Sixty-three (31.3%) were iron deficient. There were no significant differences between males and females (37.2% and 26.9%, respectively) and among the three localities studied. Iron deficiency was highest in the 3- to 9-year-old age group and lowest in the 30- to 39-year-old group. Considering the prevalence in the same localities of infections by hookworms, Trichuris trichiura, Strongyloides stercoralis, and Trichostrongylus, it is suggested that hookworms and possibly other intestinal parasites may be an important cause of the observed iron deficiency. 相似文献