全文获取类型
收费全文 | 10463篇 |
免费 | 992篇 |
国内免费 | 8篇 |
出版年
2021年 | 108篇 |
2020年 | 64篇 |
2019年 | 75篇 |
2018年 | 103篇 |
2017年 | 93篇 |
2016年 | 180篇 |
2015年 | 268篇 |
2014年 | 334篇 |
2013年 | 437篇 |
2012年 | 537篇 |
2011年 | 577篇 |
2010年 | 485篇 |
2009年 | 436篇 |
2008年 | 560篇 |
2007年 | 560篇 |
2006年 | 533篇 |
2005年 | 509篇 |
2004年 | 566篇 |
2003年 | 525篇 |
2002年 | 502篇 |
2001年 | 135篇 |
2000年 | 141篇 |
1999年 | 178篇 |
1998年 | 170篇 |
1997年 | 110篇 |
1996年 | 102篇 |
1995年 | 108篇 |
1994年 | 98篇 |
1993年 | 99篇 |
1992年 | 130篇 |
1991年 | 122篇 |
1990年 | 111篇 |
1989年 | 115篇 |
1988年 | 102篇 |
1987年 | 94篇 |
1986年 | 96篇 |
1985年 | 101篇 |
1984年 | 96篇 |
1983年 | 87篇 |
1982年 | 102篇 |
1981年 | 89篇 |
1980年 | 102篇 |
1979年 | 88篇 |
1978年 | 78篇 |
1977年 | 91篇 |
1976年 | 85篇 |
1975年 | 72篇 |
1974年 | 98篇 |
1973年 | 86篇 |
1969年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Joong Kyu Kim Mark Klinger Jonathan Benjamin Yuanyuan Xiao David J. Erle Dan R. Littman Nigel Killeen 《PloS one》2009,4(8)
Signaling through the T cell antigen receptor (TCR) is important for the homeostasis of naïve and memory CD4+ T cells. The significance of TCR signaling in regulatory T (Treg) cells has not been systematically addressed. Using an Ox40-cre allele that is prominently expressed in Treg cells, and a conditional null allele of the gene encoding p56Lck, we have examined the importance of TCR signaling in Treg cells. Inactivation of p56Lck resulted in abnormal Treg homeostasis characterized by impaired turnover, preferential redistribution to the lymph nodes, loss of suppressive function, and striking changes in gene expression. Abnormal Treg cell homeostasis and function did not reflect the involvement of p56Lck in CD4 function because these effects were not observed when CD4 expression was inactivated by Ox40-cre.The results make clear multiple aspects of Treg cell homeostasis and phenotype that are dependent on a sustained capacity to signal through the TCR. 相似文献
12.
Rachel J. Primrose Toral Zaveri Alyssa J. Bakke Gregory R. Ziegler Howard R. Moskowitz John E. Hayes 《PloS one》2016,11(3)
Vaginal microbicides potentially empower women to protect themselves from HIV and other sexually transmitted infections (STIs), especially when culture, religion, or social status may prevent them from negotiating condom use. The open literature contains minimal information on factors that drive user acceptability of women’s health products or vaginal drug delivery systems. By understanding what women find to be most important with regard to sensory properties and product functionality, developers can iteratively formulate a more desirable product. Conjoint analysis is a technique widely used in market research to determine what combination of elements influence a consumer’s willingness to try or use a product. We applied conjoint analysis here to better understand what sexually-active woman want in a microbicide, toward our goal of formulating a product that is highly acceptable to women. Both sensory and non-sensory attributes were tested, including shape, color, wait time, partner awareness, messiness/leakage, duration of protection, and functionality. Heterosexually active women between 18 and 35 years of age in the United States (n = 302) completed an anonymous online conjoint survey using IdeaMap software. Attributes (product elements) were systematically presented in various combinations; women rated these combinations of a 9-point willingness-to-try scale. By coupling systematic combinations and regression modeling, we can estimate the unique appeal of each element. In this population, a multifunctional product (i.e., broad spectrum STI protection, coupled with conception) is far more desirable than a microbicide targeted solely for HIV protection; we also found partner awareness and leakage are potentially strong barriers to use. 相似文献
13.
The Devonian cemented brachiopod Schuchertellopsis durbutensis has proved difficult to classify and its possible taxonomic relationships are unknown. Morphologically Schuchertellopsis resembles more closely members of the Orthotetidina than the Davidsoniidina. Examination of the shell structure, a key diagnostic feature of the Orthotetidina, shows that Schuchertellopsis has the cross laminar secondary shell typical of all orthotetidines. However, the presence of both pseudopunctate and incipient an extropunctate fabric within the ventral valve is unique amongst orthotetidine brachiopods and is thought to represent a phase of shell fabric experimentation. Schuchertellopsis probably fits most comfortably within the Schuchertellidae, and is the earliest representative of that family. 相似文献
14.
15.
16.
17.
Relationship Between Solute Permeability and Osmotic Remediability in a Galactose-Negative Strain of Saccharomyces cerevisiae 总被引:3,自引:1,他引:2 下载免费PDF全文
An osmotic remedial allele, gal 7-1, in the galactose pathway of Saccharomyces cerevisiae responds to either penetrating (ethylene glycol and diethylene glycol) or nonpenetrating (KCl, NaCl, and sorbitol) solutes in the growth medium. Extracts from cells grown under restrictive conditions gave no increase in enzyme activity (gal-1-phosphate, uridylyl transferase) when exposed to the penetrating solutes; thus protein synthesis or possibly polymer assembly is proposed as the critical step remedied by the addition of the solutes. 相似文献
18.
19.
20.
Cory Bystrom Shijun Sheng Ke Zhang Michael Caulfield Nigel J. Clarke Richard Reitz 《PloS one》2012,7(9)
Measurement of insulin-like growth factor-1 (IGF-I) has utility for the diagnosis and management of growth disorders, but inter-assay comparison of results has been complicated by a multitude of reference standards, antibodies, detection methods, and pre-analytical preparation strategies. We developed a quantitative LC-MS method for intact IGF-I, which has advantages in throughput and complexity when compared to mass spectrometric approaches that rely on stable isotope dilution analysis of tryptic peptides. Since the method makes use of full-scan data, the assay was easily extended to provide quantitative measurement of IGF-II using the same assay protocol. The validated LC-MS assay for IGF-I and IGF-II provides accurate results across the pediatric and adult reference range and is suitable for clinical use. 相似文献