全文获取类型
收费全文 | 6771篇 |
免费 | 661篇 |
国内免费 | 3篇 |
专业分类
7435篇 |
出版年
2022年 | 50篇 |
2021年 | 105篇 |
2020年 | 51篇 |
2019年 | 51篇 |
2018年 | 71篇 |
2017年 | 83篇 |
2016年 | 137篇 |
2015年 | 256篇 |
2014年 | 265篇 |
2013年 | 369篇 |
2012年 | 412篇 |
2011年 | 378篇 |
2010年 | 278篇 |
2009年 | 236篇 |
2008年 | 370篇 |
2007年 | 382篇 |
2006年 | 360篇 |
2005年 | 348篇 |
2004年 | 350篇 |
2003年 | 364篇 |
2002年 | 330篇 |
2001年 | 78篇 |
2000年 | 41篇 |
1999年 | 66篇 |
1998年 | 121篇 |
1997年 | 75篇 |
1996年 | 66篇 |
1995年 | 74篇 |
1994年 | 45篇 |
1993年 | 68篇 |
1992年 | 51篇 |
1991年 | 47篇 |
1990年 | 48篇 |
1989年 | 39篇 |
1988年 | 36篇 |
1987年 | 57篇 |
1986年 | 49篇 |
1985年 | 50篇 |
1984年 | 70篇 |
1983年 | 38篇 |
1982年 | 54篇 |
1981年 | 67篇 |
1980年 | 52篇 |
1978年 | 49篇 |
1977年 | 40篇 |
1976年 | 39篇 |
1974年 | 54篇 |
1973年 | 49篇 |
1972年 | 34篇 |
1961年 | 36篇 |
排序方式: 共有7435条查询结果,搜索用时 15 毫秒
41.
Therapeutic antibodies include polyclonal immunoglobulins isolated from regular or high-titered human plasma, sera from immunized animals, and monoclonal antibodies. This array of therapeutic antibodies is used for the prevention and treatment of many infectious diseases, antibody immunodeficiencies, autoimmune and inflammatory diseases, neurological disorders, and cancers. Polyclonal human immunoglobulins are available for intramuscular injection (IGIM), intravenous infusion (IGIV) and subcutaneous infusion (SCIG). We review these products and detail the therapeutic use of polyclonal human antibodies in the treatment of antibody immunodeficiencies, including their occasional local side effects (tenderness, sterile abscesses), minor systemic side effects (chills, muscle aches, malaise, headaches) and major side effects (aseptic meningitis, nephropathy, thrombosis). 相似文献
42.
43.
Margaret R. Clark John C. Guatelli Anthony T. White Stephen B. Shohet 《生物化学与生物物理学报:生物膜》1981,646(3):422-432
Using the antibiotic Nystatin, we have developed a systematic method for the preparation of red blood cells with independently selected levels of intracellular Na+ concentrations and water content. Such cells provided an experimental model to study the effect of Na+/K+ pump stimulation on red cell water content. Even in initially dehydrated cells, stimulation of the Na+/K+ pump by elevated intracellular Na+ caused subsequent further loss of cell water. Cell water loss was reflected in decreased monovalent cation content per unit mass of hemoglobin and by a shift in the density distribution of the cell populations to higher densities on discontinuous Stractan gradients. We conclude that the 3 Naout+ : 2 Kin+ stoichiometry of the Na+/K+ pump results in a net desalting effect with increased pump activity. Under the conditions of these experiments, the cell appears to have no effective mechanism to compensate for a net loss of ions and water. 相似文献
44.
The endoplasmic reticulum (ER) possesses the structural and functional features expected of an organelle that supports the integration and coordination of major cellular processes. Ca(2+) sequestered within the ER sustains lumenal protein processing while providing a reservoir of the cation to support stimulus-response coupling in the cytosol. Release of ER Ca(2+) sufficient to impair protein processing promotes ER stress and signals the "unfolded protein response" (UPR). The association of the UPR with an acute suppression of mRNA translational initiation and a longer term up-regulation of ER chaperones and partial translational recovery is discussed. Regulatory sites in mRNA translation and the mechanisms responsible for the early and later phases of the UPR are reviewed. The regulatory significance of GRP78/BiP, a multifunctional, broad-specificity ER chaperone, in the coordination of ER protein processing with mRNA translation during acute and chronic ER stress is addressed. The relationship of ER stress to protein misfolding in the cytoplasm is examined. Translational alterations in embryonic cardiomyocytes during treatments with various Ca(2+)-mobilizing, growth-promoting stimuli are described. The importance of ER Ca(2+) stores, ER chaperones, and cytosolic-free Ca(2+) in translational control and growth promotion by these stimuli is assessed. Some perspectives are provided regarding Ca(2+) as an integrating factor in the generation or diversion of metabolic energy. Circumstances impacting upon cellular adaptability during exposure to growth stimuli or during stressful conditions that require rapid adjustments in ATP for continued viability are considered. 相似文献
45.
46.
A fundamental question concerning group-living species is what factors influence the evolution of sociality. Although several studies link adult social bonds to fitness, social patterns and relationships are often formed early in life and are also likely to have fitness consequences, particularly in species with lengthy developmental periods, extensive social learning, and early social bond-formation. In a longitudinal study of bottlenose dolphins (Tursiops sp.), calf social network structure, specifically the metric eigenvector centrality, predicted juvenile survival in males. Additionally, male calves that died post-weaning had stronger ties to juvenile males than surviving male calves, suggesting that juvenile males impose fitness costs on their younger counterparts. Our study indicates that selection is acting on social traits early in life and highlights the need to examine the costs and benefits of social bonds during formative life history stages. 相似文献
47.
Nguyen D Dhanasekaran P Nickel M Nakatani R Saito H Phillips MC Lund-Katz S 《Biochemistry》2010,49(51):10881-10889
Human apolipoprotein (apo) E4 binds preferentially to very low-density lipoproteins (VLDLs), whereas apoE3 binds preferentially to high-density lipoproteins (HDLs), resulting in different plasma cholesterol levels for the two isoforms. To understand the molecular basis for this effect, we engineered the isolated apoE N-terminal domain (residues 1-191) and C-terminal domain (residues 192-299) together with a series of variants containing deletions in the C-terminal domain and assessed their lipid and lipoprotein binding properties. Both isoforms can bind to a phospholipid (PL)-stabilized triolein emulsion, and residues 261-299 are primarily responsible for this activity. ApoE4 exhibits better lipid binding ability than apoE3 as a consequence of a rearrangement involving the segment spanning residues 261-272 in the C-terminal domain. The strong lipid binding ability of apoE4 coupled with the VLDL particle surface being ~60% PL-covered is the basis for its preference for binding VLDL rather than HDL. ApoE4 binds much more strongly than apoE3 to VLDL but less strongly than apoE3 to HDL(3), consistent with apoE-lipid interactions being relatively unimportant for binding to HDL. The preference of apoE3 for binding to HDL(3) arises because binding is mediated primarily by interaction of the N-terminal helix bundle domain with the resident apolipoproteins that cover ~80% of the HDL(3) particle surface. Thus, the selectivity in the binding of apoE3 and apoE4 to HDL(3) and VLDL is dependent upon two factors: (1) the stronger lipid binding ability of apoE4 relative to that of apoE3 and (2) the differences in the nature of the surfaces of VLDL and HDL(3) particles, with the former being largely covered with PL and the latter with protein. 相似文献
48.
Paul W. R. Harris Margaret A. Brimble 《International journal of peptide research and therapeutics》2012,18(1):63-70
As a first step towards the preparation of a functional biomolecule, a chemical synthesis of the collagenous domain of adiponectin is described. The 76 residue polypeptide (without post-translational modifications) could be assembled efficiently from smaller unprotected peptides using two native chemical ligation reactions followed by a reductive desulfurisation step. In turn, the polypeptides were synthesised in high purity by microwave enhanced solid phase synthesis. 相似文献
49.
Background
Extracting biological information from high-density Affymetrix arrays is a multi-step process that begins with the accurate annotation of microarray probes. Shortfalls in the original Affymetrix probe annotation have been described; however, few studies have provided rigorous solutions for routine data analysis. 相似文献50.
During the past two years a pilot project was conducted in which 19 inactive physicians were retrained in preparation for resumption of active practice. The initial program consisted of a flexible training program of six months to one year patterned after conventional internship-residency concepts. During the second year the program was modified by providing an initial condensed indoctrination period of two months'' duration especially designed for this purpose, followed by a preceptorship type of training.The project was considered successful in permitting trainees to enter some form of active medical work, or to enroll in formal specialty training. The observations made by the faculty of the program and its accomplishments are discussed in the light of the effort expended and the cost of the project. 相似文献