全文获取类型
收费全文 | 4269篇 |
免费 | 585篇 |
专业分类
4854篇 |
出版年
2021年 | 38篇 |
2018年 | 37篇 |
2016年 | 59篇 |
2015年 | 112篇 |
2014年 | 97篇 |
2013年 | 129篇 |
2012年 | 195篇 |
2011年 | 163篇 |
2010年 | 110篇 |
2009年 | 102篇 |
2008年 | 145篇 |
2007年 | 181篇 |
2006年 | 136篇 |
2005年 | 112篇 |
2004年 | 156篇 |
2003年 | 138篇 |
2002年 | 134篇 |
2001年 | 147篇 |
2000年 | 140篇 |
1999年 | 152篇 |
1998年 | 51篇 |
1997年 | 51篇 |
1996年 | 58篇 |
1995年 | 46篇 |
1994年 | 44篇 |
1993年 | 40篇 |
1992年 | 97篇 |
1991年 | 115篇 |
1990年 | 123篇 |
1989年 | 101篇 |
1988年 | 115篇 |
1987年 | 97篇 |
1986年 | 98篇 |
1985年 | 102篇 |
1984年 | 87篇 |
1983年 | 85篇 |
1982年 | 75篇 |
1981年 | 60篇 |
1980年 | 55篇 |
1979年 | 92篇 |
1978年 | 59篇 |
1977年 | 62篇 |
1976年 | 51篇 |
1975年 | 62篇 |
1974年 | 50篇 |
1973年 | 58篇 |
1972年 | 37篇 |
1971年 | 39篇 |
1969年 | 40篇 |
1967年 | 37篇 |
排序方式: 共有4854条查询结果,搜索用时 15 毫秒
81.
82.
The blood flow through an arterial stenosis can theoretically be increased by gradual expansion of the stenosis. This hypothesis was tested by comparing the flow through abruptly expanding and gradually expanding stenosed plastic conduits. The conduits were tested in non-pulsatile flow with water and bank blood and in pulsatile flow in dog's descending aorta. It was found that:
- (a)The pressure drop in arterial stenoses is larger than that predicted by non-pulsatile theory. 相似文献
83.
84.
85.
Induction and repression of the histidine-degrading enzymes in Aerobacter aerogenes 总被引:19,自引:0,他引:19
B Magasanik P Lund F C Neidhardt D T Schwartz 《The Journal of biological chemistry》1965,240(11):4320-4324
86.
Isolation of skeletal muscle nuclei 总被引:3,自引:2,他引:1
87.
88.
Eli Shapiro Steven D. Brown Alan R. Saltiel James H. Schwartz 《Developmental neurobiology》1991,22(1):55-62
In mollusks as in other animals, peptides can act as hormones, growth factors, and neurotransmitters. The presence of insulin in vertebrate brain as well as its actions on nerve cells led us to examine the electrophysiological effects of the mammalian hormone on Aplysia neurons. Application of insulin extracellularly causes hyperpolarization of L14 and L10, identified neurons of the abdominal ganglion. This hyperpolarization is associated with a decreased membrane conductance that reverses at ?35 mV. We also injected inositol phosphate glycan (IPG) into the identified neurons. This complex sugar, which was purified from rat liver and which is a putative second messenger for insulin in nonneural vertebrate cells (Saltiel and Cuatrecasas, 1986; Saltiel, Osterman, and Darnell, 1988), causes hyperpolarization with decreased membrane conductance in L14 and L10 similar to the effects of insulin. Furthermore, exposure of isolated ganglia to insulin results in the generation of IPG with a compensating decrease in its glycosyl-phosphatidylinositol precursor. We suggest that, in addition to its other roles, insulin may function as a neuropeptide transmitter using IPG as a second messenger. 相似文献
89.
Genetic and physical mapping of a novel region close to the fragile X site on the human X chromosome 总被引:11,自引:0,他引:11
M. N. Patterson M. V. Bell J. Bloomfield T. Flint H. Dorkins S. N. Thibodeau D. Schaid G. Bren C. E. Schwartz b. Wieringa H. -H. Ropers D. F. Callen G. Sutherland U. Froster-Iskenius H. Vissing K. E. Davies 《Genomics》1989,4(4):570-578
We report the isolation and characterization of a novel DNA marker (1A1) in Xqter in the region of the fragile X. Genetic studies in families segregating for the fragile X syndrome suggest that 1A1 lies between the disease mutation and the distal locus, DXS52. Studies in normal and fragile X families show that 1A1 is tightly linked to DXS52 (Zmax = 17.20; theta max = 0.03) and F8 (Zmax = 7.01; theta max = 0.08). Multipoint mapping of families supports the order Xcen-DXS105-FRAXA-1A1-DXS52-(F8, DXS115)-Xqter. Pulsed-field gel electrophoresis (PFGE) studies demonstrate that 1A1 defines a new region of at least 2 Mb of DNA not physically linked to DXS52 or F8, thus extending the physical map of Xq27-qter to over 4 Mb. Complex partial digestion PFGE patterns, probably due to differing degrees of methylation, are observed with 1A1 in unrelated normal and fragile-X-positive individuals, whereas other distal markers give uniform digestion profiles. Physical data suggest that 1A1 lies in a region less CpG rich than other distal markers in Xq27-qter. 相似文献
90.
The genomic organization of platelet glycoprotein IIIa 总被引:13,自引:0,他引:13
A B Zimrin S Gidwitz S Lord E Schwartz J S Bennett G C White M Poncz 《The Journal of biological chemistry》1990,265(15):8590-8595