全文获取类型
收费全文 | 31613篇 |
免费 | 15987篇 |
国内免费 | 15篇 |
出版年
2023年 | 74篇 |
2022年 | 211篇 |
2021年 | 628篇 |
2020年 | 2271篇 |
2019年 | 3868篇 |
2018年 | 3988篇 |
2017年 | 4253篇 |
2016年 | 4296篇 |
2015年 | 4316篇 |
2014年 | 3937篇 |
2013年 | 4474篇 |
2012年 | 2221篇 |
2011年 | 1910篇 |
2010年 | 3291篇 |
2009年 | 1992篇 |
2008年 | 973篇 |
2007年 | 568篇 |
2006年 | 513篇 |
2005年 | 553篇 |
2004年 | 470篇 |
2003年 | 432篇 |
2002年 | 465篇 |
2001年 | 394篇 |
2000年 | 370篇 |
1999年 | 258篇 |
1998年 | 59篇 |
1997年 | 37篇 |
1996年 | 40篇 |
1995年 | 53篇 |
1994年 | 43篇 |
1993年 | 37篇 |
1992年 | 75篇 |
1991年 | 61篇 |
1990年 | 58篇 |
1989年 | 61篇 |
1988年 | 46篇 |
1987年 | 34篇 |
1986年 | 43篇 |
1985年 | 46篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 14篇 |
1981年 | 18篇 |
1980年 | 9篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1972年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
221.
Replication-defective mutants of herpes simplex virus (HSV) induce cellular immunity and protect against lethal HSV infection. 总被引:9,自引:6,他引:3
Live viruses and live virus vaccines induce cellular immunity more readily than do inactivated viruses or purified proteins, but the mechanism by which this process occurs is unknown. A trivial explanation would relate to the ability of live viruses to spread and infect more cells than can inactivated virus. We have used live but replication-defective mutants to investigate this question. Our studies indicate that the immune responses of mice to live virus differ greatly from the responses to inactivated virus even when the virus does not complete a replicative cycle. Further, these studies indicate that herpes simplex virus-specific T-cell responses can be generated by infection with replication-defective mutant viruses. These data indicate that the magnitude of the cellular immunity to herpes simplex virus may be proportional to the number or quantity of different viral gene products expressed by an immunizing virus. 相似文献
222.
S Shefer L B Nguyen G Salen G C Ness I R Chowdhary S Lerner A K Batta G S Tint 《Journal of lipid research》1992,33(8):1193-1200
223.
Purification and characterization of cytosolic 6-phosphogluconate dehydrogenase isozymes from maize 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Cytosolic isozymes of 6-phosphogluconate dehydrogenase were purified from roots of maize (Zea mays L.). The final preparation contained two 55-kD proteins. Affinity-purified dehydrogenases from a maize line that is null for both cytosolic 6-phosphogluconate dehydrogenase isozymes (Pgd1-null, Pgd2-null) lacked the 55-kD proteins. The substrate kinetics of the purified enzyme were determined. 相似文献
224.
Summary We report here an improved method for nuclei counting utilizing Triton-X 100 to reduce the size of cell debris, thereby allowing the use of a particle sizer/counter. Furthermore, nuclei are completely released within 30 seconds, as compared to 1 hour using hypotonic solution. The method is accurate above 0.3 × 106 cells/mL. 相似文献
225.
226.
The substrate specificity of purified PKC-alpha, -beta and -gamma has been investigated. A series of synthetic peptides based upon the sequence surrounding serine-7 in glycogen synthase were generated and used to determine the basic residue requirements of these PKC isotypes. While PKC-alpha and -beta are indistinguishable in their phosphorylation of these peptides, PKC-gamma shows a distinct specificity profile for these synthetic substrates. 相似文献
227.
Interaction between corticosteroid binding globulin and activated leukocytes in vitro 总被引:1,自引:0,他引:1
G L Hammond C L Smith C M Underhill V T Nguyen 《Biochemical and biophysical research communications》1990,172(1):172-177
The interaction between human corticosteroid binding globulin and activated leukocytes is restricted to the granulocyte population, and is characterized by specific proteolytic cleavage of corticosteroid binding globulin which markedly reduces its steroid binding activity. A direct interaction between corticosteroid binding globulin and the activated cells appears to enhance this event, and does not involve cellular internalization of corticosteroid binding globulin or its proteolytic degradation products, which resemble those obtained after incubation of corticosteroid binding globulin with neutrophil elastase. These data suggest that corticosteroid binding globulin interacts with elastase on the surface of activated neutrophils, and may promote glucocorticoid delivery to these cells during inflammation. 相似文献
228.
Transabdominal fine needle aspiration biopsy of a solitary space-occupying lesion in the liver produced smears containing irregular bundles of smooth muscle cells with granular or fibrillary cytoplasm and slightly pleomorphic nuclei. In a few bundles, aggregates of mature fat cells were present, which is characteristic for an angiomyolipoma. Histologic examination of the resected mass showed it to be a solitary angiomyolipoma of the liver. The diagnosis was further confirmed by immunohistochemical and electron microscopic studies. 相似文献
229.
Twenty independent man-mouse (Cl1D,LA/TK-, HPRT-) and man-hamster (CH,HPRT-) hybrids using female human cells with balanced reciprocal translocation XX,t(X;5)(q21;q11) were analyzed for human genes localized on chromosome 5 (HEXB), on chromosome X (PGK, GALA, HPRT, G6PD) and for the different chromosomes in relation with the balanced reciprocal translocation (chr.5, chr.5q-, chr.Xq+, chr.X). The different results obtained indicate that the genes for human markers HEXB, PGK are on Xq+, and that the genes for human markers GALA, G6PD are on 5q-. These data implicate finally the following localizations: HEXB on 5q11 leads to 5qter; PGK on Xq21 leads to Xpter; GALA, HPRT, G6PD on Xq21 leads to Xqter. 相似文献
230.
Jeffry Reidler Vernon T. Oi William Carlsen T.Minh Vuong Israel Pecht Leonard A. Herzenberg Lubert Stryer 《Journal of molecular biology》1982,158(4):739-746
The rotational motions of monoclonal mouse anti-dansyl immunoglobulins were studied by nanosecond fluorescence emission anisotropic spectroscopy using a mode-locked argon-ion laser as the pulsed excitation source. Three homogeneous antibodies of the immunoglobulin Gl (IgGl) subclass containing different V regions were prepared. The fluorescence emission maxima of these antibodies (designated as DNS1, DNS2 and DNS3) are at 515, 480 and 500 nm, respectively. Their mean rotational correlation times, 〈φ〉, are 84, 109 and 96 ns, respectively. The binding of protein A or a monoclonal anti-allotype antibody to the Fc unit of DNS1 increased 〈φ〉 to 142 and 150 ns, respectively, whereas reduction of the disulfide bond between the heavy chains decreased 〈φ〉 to 48 ns. These nanosecond measurements show that the rotational motion of the Fab arms in mouse IgGl is restricted. 相似文献