全文获取类型
收费全文 | 405435篇 |
免费 | 46083篇 |
国内免费 | 174篇 |
专业分类
451692篇 |
出版年
2018年 | 3492篇 |
2017年 | 3481篇 |
2016年 | 4671篇 |
2015年 | 6211篇 |
2014年 | 7228篇 |
2013年 | 10808篇 |
2012年 | 12092篇 |
2011年 | 12219篇 |
2010年 | 8183篇 |
2009年 | 7636篇 |
2008年 | 11104篇 |
2007年 | 11252篇 |
2006年 | 10840篇 |
2005年 | 10237篇 |
2004年 | 10133篇 |
2003年 | 9819篇 |
2002年 | 9578篇 |
2001年 | 18886篇 |
2000年 | 19076篇 |
1999年 | 15487篇 |
1998年 | 5422篇 |
1997年 | 5684篇 |
1996年 | 5498篇 |
1995年 | 4994篇 |
1994年 | 5111篇 |
1993年 | 4977篇 |
1992年 | 12909篇 |
1991年 | 12332篇 |
1990年 | 12268篇 |
1989年 | 12229篇 |
1988年 | 11136篇 |
1987年 | 10595篇 |
1986年 | 9818篇 |
1985年 | 9857篇 |
1984年 | 7992篇 |
1983年 | 6958篇 |
1982年 | 5288篇 |
1981年 | 4667篇 |
1980年 | 4547篇 |
1979年 | 7660篇 |
1978年 | 5928篇 |
1977年 | 5290篇 |
1976年 | 5113篇 |
1975年 | 5529篇 |
1974年 | 5778篇 |
1973年 | 5700篇 |
1972年 | 5161篇 |
1971年 | 4561篇 |
1970年 | 4031篇 |
1969年 | 3732篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
221.
222.
223.
P. Marion Handford 《Journal of applied microbiology》1974,37(4):559-570
S ummary . This paper describes the development and use of a selective diagnostic medium for the detection and enumeration of Clostridium perfringens in foods. The medium gives higher counts of Cl. perfringens and fewer false positives than existing media. 相似文献
224.
225.
226.
227.
Sukhraj S. Dhillon Graeme P. Berlyn Jerome P. Miksche 《American journal of botany》1978,65(2):192-196
Five populations of Pinus rigida growing in contrasting ecological situations ranging from North Carolina (35°53'N latitude) to Quebec (45°06'N latitude) showed no significant variation in amounts of nuclear DNA with respect to germinating seedlings. Nuclear volume of dormant nuclei also showed no significant variation between and within populations, a finding that is consistent with the concept that the basic 2C DNA value of Pinus rigida is uniform under all habitats. This finding is in contrast to numerous reports for other coniferous species. 相似文献
228.
Indomethacin and substance BW-755C in experiments on isolated myometrium striae of pregnant white rats exert an inhibiting effect on the contractile uterus function due to inhibition of cyclooxygenase or lipoxygenase ways of the arachidonic acid transformation. Prostaglandin F2 alpha is sensitive to functioning of the cyclooxygenase and lipoxygenase ways of the arachidonic acid transformation, while oxytocin--only lipoxygenase one. Conclusions rest on results from multiparametric analysis of the contractile uterus function suggested by authors and confirmed by the pattern recognition method--the Karunen-Loev orthogonal decomposition. 相似文献
229.
Isoproterenol-stimulated cyclic AMP (cAMP) accumulation in lymphocytes is an index of beta-adrenergic receptor functioning. It is not known if a delay between blood collection and subsequent cell preparation influences cAMP accumulation. We compared cAMP levels in lymphocytes processed from whole blood immediately after collection and following a 3.5 hour delay. There were no significant changes in either basal or stimulated levels of cAMP. This information may alleviate time constraints in certain experimental designs where immediate isolation of lymphocytes from whole blood may not be practical. 相似文献
230.
The aquatic larvae of the genus Chironomus (Diptera, Insecta) contain at least 12 different hemoglobin (Hb) variants in their hemolymph. In the present study we have analysed the structure and part of the nucleotide sequence of a Hb gene cluster cloned from the genomic DNA of Chironomus thummi piger. The cluster contains probably 6 different genes, separated by intergenic regions of various lengths. The nucleotide sequence of three putative Hb genes including the intergenic regions is presented. The inferred amino-acid sequences show clearly that two of these putative genes code for subvariants of the Hb variant VIIB. The third gene codes for a so far unknown Hb protein. As known already for other chironomid Hb genes, there are no intron sequences present in the coding regions. 相似文献