全文获取类型
收费全文 | 14142篇 |
免费 | 1946篇 |
国内免费 | 7篇 |
出版年
2021年 | 130篇 |
2019年 | 139篇 |
2018年 | 151篇 |
2017年 | 148篇 |
2016年 | 254篇 |
2015年 | 308篇 |
2014年 | 417篇 |
2013年 | 551篇 |
2012年 | 650篇 |
2011年 | 591篇 |
2010年 | 442篇 |
2009年 | 370篇 |
2008年 | 566篇 |
2007年 | 570篇 |
2006年 | 486篇 |
2005年 | 546篇 |
2004年 | 491篇 |
2003年 | 489篇 |
2002年 | 446篇 |
2001年 | 459篇 |
2000年 | 449篇 |
1999年 | 397篇 |
1998年 | 184篇 |
1997年 | 167篇 |
1996年 | 169篇 |
1995年 | 152篇 |
1994年 | 184篇 |
1993年 | 150篇 |
1992年 | 317篇 |
1991年 | 304篇 |
1990年 | 299篇 |
1989年 | 287篇 |
1988年 | 308篇 |
1987年 | 281篇 |
1986年 | 246篇 |
1985年 | 259篇 |
1984年 | 235篇 |
1983年 | 195篇 |
1982年 | 150篇 |
1981年 | 150篇 |
1980年 | 147篇 |
1979年 | 197篇 |
1978年 | 200篇 |
1977年 | 147篇 |
1976年 | 164篇 |
1975年 | 175篇 |
1974年 | 210篇 |
1973年 | 193篇 |
1972年 | 153篇 |
1970年 | 146篇 |
排序方式: 共有10000条查询结果,搜索用时 654 毫秒
101.
102.
Human placental α-l-fucosidase has been purified 670-fold with a 57% yield by a one-step affinity chromatographic procedure using agaroseepsilon-amino-caproyl-fucosamine. 相似文献
103.
104.
105.
106.
Reginald Miller 《BMJ (Clinical research ed.)》1927,1(3463):937-938
107.
108.
109.
J A Zanghi A E Schmelzer T P Mendoza R H Knop W M Miller 《Biotechnology and bioengineering》1999,65(2):182-191
Accumulation of CO(2) in animal cell cultures can be a significant problem during scale-up and production of recombinant glycoprotein biopharmaceuticals. By examining the cell-surface polysialic acid (PSA) content, we show that elevated CO(2) partial pressure (pCO(2)) can alter protein glycosylation. PSA is a high-molecular-weight polymer attached to several complex N-linked oligosaccharides on the neural cell adhesion molecule (NCAM), so that small changes in either core glycosylation or in polysialylation are amplified and easily measured. Flow-cytometric analysis revealed that PSA levels on Chinese hamster ovary (CHO) cells decrease with increasing pCO(2) in a dose-dependent manner, independent of any change in NCAM content. The results are highly pH-dependent, with a greater decrease in PSA at higher pH. By manipulating medium pH and pCO(2), we showed that decreases in PSA correlate well with bicarbonate concentration ([HCO(3)(-)]). In fact, it was possible to offset a 60% decrease in PSA content at 120 mm Hg pCO(2) by decreasing the pH from 7.3 to 6.9, such that [HCO(3)(-)] was lowered to that of control (38 mm Hg pCO(2)). When the increase in osmolality associated with elevated [HCO(3)(-)] was offset by decreasing the basal medium [NaCl], elevated [HCO(3)(-)] still caused a decrease in PSA, although less extensive than without osmolality control. By increasing [NaCl], we show that hyperosmolality alone decreases PSA content, but to a lesser extent than for the same osmolality increase due to elevated [NaHCO(3)]. In conclusion, we demonstrate the importance of pH and pCO(2) interactions, and show that [HCO(3)(-)] and osmolality can account for the observed changes in PSA content over a wide range of pH and pCO(2) values. 相似文献
110.