全文获取类型
收费全文 | 26501篇 |
免费 | 58篇 |
国内免费 | 107篇 |
专业分类
系统科学 | 86篇 |
丛书文集 | 243篇 |
教育与普及 | 88篇 |
理论与方法论 | 87篇 |
现状及发展 | 11984篇 |
研究方法 | 1037篇 |
综合类 | 12834篇 |
自然研究 | 307篇 |
出版年
2013年 | 168篇 |
2012年 | 343篇 |
2011年 | 618篇 |
2008年 | 405篇 |
2007年 | 460篇 |
2006年 | 413篇 |
2005年 | 448篇 |
2004年 | 478篇 |
2003年 | 447篇 |
2002年 | 432篇 |
2001年 | 741篇 |
2000年 | 738篇 |
1999年 | 517篇 |
1994年 | 338篇 |
1992年 | 456篇 |
1991年 | 370篇 |
1990年 | 431篇 |
1989年 | 396篇 |
1988年 | 411篇 |
1987年 | 433篇 |
1986年 | 412篇 |
1985年 | 547篇 |
1984年 | 374篇 |
1983年 | 382篇 |
1982年 | 356篇 |
1981年 | 324篇 |
1980年 | 393篇 |
1979年 | 831篇 |
1978年 | 681篇 |
1977年 | 638篇 |
1976年 | 528篇 |
1975年 | 610篇 |
1974年 | 718篇 |
1973年 | 682篇 |
1972年 | 722篇 |
1971年 | 850篇 |
1970年 | 967篇 |
1969年 | 829篇 |
1968年 | 869篇 |
1967年 | 770篇 |
1966年 | 685篇 |
1965年 | 472篇 |
1964年 | 170篇 |
1959年 | 257篇 |
1958年 | 493篇 |
1957年 | 353篇 |
1956年 | 305篇 |
1955年 | 294篇 |
1954年 | 265篇 |
1948年 | 235篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
J. W. Faigle H. Stierlin H. Mory T. Winkler H. -P. Kriemler 《Cellular and molecular life sciences : CMLS》1985,41(4):476-478
Summary Indoxyl derivatives were detected as minor products among the urinary metabolites of two trial drugs, a benzodiazepine (GP 55 129) and a benzophenone (CGP 11 952). Their structures were elucidated by NMR and mass spectroscopy. Presumably, metabolites containing potential aldehyde functions react spontaneously with endogenous indoxyl. Such derivatives have not hitherto been encountered in drug metabolism. 相似文献
12.
就近几年图书馆界关于新世纪馆员意识转换及社会角色转换等方面的研究进行了综述,指出新时期的馆员要实现自我社会角色的转换,首先是要明确转换的必要性,然后采取有效的策略逐步地、系统地推进转换,才能取得较好的效果。 相似文献
13.
We investigated the sound communication associated with mating inNezara viridula (L.) to clarify conflicting reports on the medium through which acoustic signals are borne. Recordings made from virgin pairs ofN. viridula during precopulatory and compulatory behaviour have revealed that signals transmitted as vibrations through the substrate are a more likely means of communication than signals transmitted by a radiation of sound pressure waves through the air (at least in Australian populations). We present evidence (additional to that already in the literature) that air-borne acoustics are an unlikely mechanism of sexual communication in this species. Specifically, the recorded pulse train patterns showed no consistency or repeatability in relation to different stages of mating behaviour. In contrast, frequency spectrograms of substrate-borne signals reveal repeatable patterns that do correspond with the stage of mating behaviour. 相似文献
14.
Aspirin-like drugs may block pain independently of prostaglandin synthesis inhibition 总被引:2,自引:0,他引:2
K. Brune W. S. Beck G. Geisslinger S. Menzel-Soglowek B. M. Peskar B. A. Peskar 《Cellular and molecular life sciences : CMLS》1991,47(3):257-261
Summary Using flurbiprofen, a chiral anti-inflammatory and analgesic 2-arylpropionic acid derivative, the enantiomers of which are not converted to each other (less than 5%) in rats or man, we obtained evidence that prostaglandin synthesis inhibition is primarily mediating the anti-inflammatory activity but prostaglandin synthesis independent mechanisms contribute to the analgesic effects. Thus, the S-form inhibited prostaglandin synthesis, inflammation and nociception in rats. The R-form had much less effect on prostaglandin synthesis and did not affect inflammation. It did, however, block nociception in rats almost as potently as the S-form. S-flurbiprofen, in contrast to the R-form, was clearly ulcerogenic in the gastrointestinal mucosa. These results indicate additional molecular mechanisms of analgesia and suggest the use of R-arylpropionic acids as analgesics. 相似文献
15.
16.
Aeromonas caviae isolated from stools of diarrheic formula-fed infants and environmental sources produce acetic acid when grown in glucose broth, which is bactericidal (suicide phenomenon). A. caviae grows anaerobically in a minimal medium or under permissive conditions such as the intestinal tract of formula-fed infants. These isolates adhered to HEp-2 cells and produced a cytotoxic and a cytotonic enterotoxin which underscore their enteropathogenicity. 相似文献
17.
M E MacDonald A Novelletto C Lin D Tagle G Barnes G Bates S Taylor B Allitto M Altherr R Myers 《Nature genetics》1992,1(2):99-103
Analysis of 78 Huntington's disease (HD) chromosomes with multi-allele markers revealed 26 different haplotypes, suggesting a variety of independent HD mutations. The most frequent haplotype, accounting for about one third of disease chromosomes, suggests that the disease gene is between D4S182 and D4S180. However, the paucity of an expected class of chromosomes that can be related to this major haplotype by assuming single crossovers may reflect the operation of other mechanisms in creating haplotype diversity. Some of these mechanisms sustain alternative scenarios that do not require a multiple mutational origin for HD and/or its positioning between D4S182 and D4S180. 相似文献
18.
19.
20.