全文获取类型
收费全文 | 2796篇 |
免费 | 148篇 |
国内免费 | 176篇 |
专业分类
系统科学 | 8篇 |
丛书文集 | 98篇 |
教育与普及 | 17篇 |
理论与方法论 | 2篇 |
现状及发展 | 79篇 |
综合类 | 2916篇 |
出版年
2024年 | 4篇 |
2023年 | 14篇 |
2022年 | 36篇 |
2021年 | 48篇 |
2020年 | 25篇 |
2019年 | 29篇 |
2018年 | 37篇 |
2017年 | 70篇 |
2016年 | 69篇 |
2015年 | 90篇 |
2014年 | 121篇 |
2013年 | 90篇 |
2012年 | 162篇 |
2011年 | 135篇 |
2010年 | 108篇 |
2009年 | 121篇 |
2008年 | 126篇 |
2007年 | 190篇 |
2006年 | 141篇 |
2005年 | 170篇 |
2004年 | 137篇 |
2003年 | 145篇 |
2002年 | 136篇 |
2001年 | 116篇 |
2000年 | 93篇 |
1999年 | 81篇 |
1998年 | 57篇 |
1997年 | 59篇 |
1996年 | 70篇 |
1995年 | 78篇 |
1994年 | 50篇 |
1993年 | 59篇 |
1992年 | 59篇 |
1991年 | 36篇 |
1990年 | 47篇 |
1989年 | 37篇 |
1988年 | 37篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 2篇 |
1984年 | 1篇 |
排序方式: 共有3120条查询结果,搜索用时 109 毫秒
201.
M.-C. Broillet 《Cellular and molecular life sciences : CMLS》1999,55(8-9):1036-1042
The transfer of a nitric oxide group to cysteine sulfhydryls on proteins, known as S-nitrosylation, is increasingly becoming
recognized as a ubiquitous regulatory reaction comparable to phosphorylation. It represents a form of redox modulation in
diverse tissues, including the brain. An increasing number of proteins have been found to undergo S-nitrosylation in vivo.
These proteins are called S-nitrosothiols, and may play an important role in many processes ranging from signal transduction,
DNA repair, host defense, and blood pressure control to ion channel regulation and neurotransmission. This review focuses
on the importance of the S-nitrosylation reaction and describes some recently identified S-nitrosothiols in various fields
of research. 相似文献
202.
Mulhern S. A. Stroube W. B. Jacobs R. M. 《Cellular and molecular life sciences : CMLS》1986,42(5):551-553
Summary Second generation mice were exposed to normal (50 ppm, Group I) or excess (2000 ppm, Group II) zinc in the maternal diet during gestation and lactation, then weaned and continued on the mother's diet until sacrifice at 8 weeks. Tibia zinc reflected dietary intake. Group II had reduced plasma copper, body weight, and hematocrit; the second coat of hair appeared late and was lighter in color than Group I, possibly as an effect of copper and pigmentation development and hair growth. 相似文献
203.
傅建杭 《南开大学学报(自然科学版)》1994,(1)
本研究介绍了如何应用近红外光谱对N─H、O─H等官能团进行定量分析,以及如何应用近红外光谱法研究金属氧化物的表面羟基与其催化活性的关系。 相似文献
204.
李慎新 《西南民族学院学报(自然科学版)》1996,22(1):62-64
提出了在铬黑T、乙二胺、三乙酸胺体系中连续测定镁、锌、铁的极话催化波.三元素在—0.94V、—1.44V、—1.67V(对SCE、下同)产生灵敏的极谱波.各元素在0~0.8μg/mL范围内浓度和导数峰高里线性关系.提出的方法用于同时测定头发和水中的痕量镁、锌、铁,结果满意. 相似文献
205.
LI Fashen WANG Tao REN Liyuan & SUN Jianrong Key Laboratory for Magnetism Magnetic Materials of the Ministry of Education Lanzhou University Lanzhou China 《科学通报(英文版)》2004,49(14):1532-1535
It is important to find some developing high-density magnetic recording materials in magnetic recording field with the development of information and technique, in which vertical magnetic recording is a very important way and has received considerable attention[1—3]. The vertical magnetic recording materials require high squareness, suitable coercivity, and small size of storage element[4]. Someone used nanoporous anodic aluminum oxide as templates to fabricate uniform arrays of multi magneti… 相似文献
206.
Novel aspects of glypican glycobiology 总被引:5,自引:0,他引:5
Fransson LA Belting M Cheng F Jönsson M Mani K Sandgren S 《Cellular and molecular life sciences : CMLS》2004,61(9):1016-1024
Mutations in glypican genes cause dysmorphic and overgrowth syndromes in men and mice, abnormal development in flies and worms, and defective gastrulation in zebrafish and ascidians. All glypican core proteins share a characteristic pattern of 14 conserved cysteine residues. Upstream from the C-terminal membrane anchorage are 3–4 heparan sulfate attachment sites. Cysteines in glypican-1 can become nitrosylated by nitric oxide in a copper-dependent reaction. When glypican-1 is exposed to ascorbate, nitric oxide is released and participates in deaminative cleavage of heparan sulfate at sites where the glucosamines have a free amino group. This process takes place while glypican-1 recycles via a nonclassical, caveolin-1-associated route. Glypicans are involved in growth factor signalling and transport, e.g. of polyamines. Cargo can be unloaded from heparan sulfate by nitric oxide-dependent degradation. How glypican and its degradation products and the cargo exit from the recycling route is an enigma.Received 27 November 2003; received after revision 8 January 2004; accepted 13 January 2004 相似文献
207.
Overview of mammalian zinc transporters 总被引:27,自引:0,他引:27
208.
A tetranuclear zinc benzoate Zr4O(C6H5CO2)6 was synthesized and characterized by X-ray single crystal determination. It crystallizes in cubic, space group Ia-3d. Its crystal cell is very large, α=4.10063(18)nm, V=68.953(5)nm^3 and Z=48. The structure is composed of discrete Zr4O(C6H5CO2)6 molecules. In each molecule, four zinc atoms are held together by a central oxygen atom, which results in the formation of a regular tetrahedron. All benzoate ligands coordinate to zinc atoms in a bidentate bridging mode. Each zinc atom is in a slightly distorted tetrahedral geometry, coordinated by three benzoate oxygen atoms and the central oxygen atom. The intermolecular interactions result in the formation of a three-dimensional supramolecular framework, with non-intersecting parallel channels. 相似文献
209.
Schaefer U Schneider A Rudroff C Neugebauer E 《Cellular and molecular life sciences : CMLS》2003,60(9):1968-1981
During agonist-dependent long-term stimulation of cells, histamine receptor subtypes are frequently down-regulated. However, the mechanisms underlying the modulation of receptor expression during long-term histamine stimulation have yet to be resolved. Based on our recently reported results showing an H1-mediated down-regulation of histamine H2 receptor mRNA in endothelial cells, our aim was to characterize the mechanism controlling rapid and long-term histamine-mediated modulation of H2 receptor expression in more detail. We were able to show that the histamine-induced down-regulation of H2 receptor mRNA and cell surface expression lasting for 24 h was accompanied by augmentation of the receptor protein level in the cytoplasmatic fraction of endothelial cells for this time period. Furthermore, changes in receptor protein levels in whole-cell lysate were negligible, indicating that the rapid and prolonged modulation of cell surface H2 receptor levels by histamine was regulated solely via internalization. The role of nitric oxide (NO) as a key mediator in histamine-stimulated cell responses was underlined by subsequent studies showing the attenuation of histamine-induced H2 receptor mRNA down-regulation and protein trafficking following NO synthase isozyme inhibition.Received 11 March 2003; received after revision 11 June 2003; accepted 17 June 2003 相似文献
210.
HUANG Xiaochun ZHANG Jiepeng & CHEN Xiaoming . School of Chemistry Chemical Engineering Sun Yat-Sen Uiniversity Guangzhou China . Department of Chemistry Shantou University Shantou China Correspondence should be addressed to Chen Xiaoming 《科学通报(英文版)》2003,48(15):1531-1534
Considerable efforts have been focused on the crystal engineering of the supramolecular architectures with desired properties such as zeolitic, magnetic and electric conducting materials[1—3]. But crystal engineering is still a great challenge to the chemists since lack of control over the coordination modes of metal centers and ligands during assembly of extended structures[4]. Some successful synthetic strategies based on topologic control of building blocks have been developed especially i… 相似文献