全文获取类型
收费全文 | 7259篇 |
免费 | 652篇 |
国内免费 | 3篇 |
专业分类
7914篇 |
出版年
2023年 | 63篇 |
2022年 | 160篇 |
2021年 | 271篇 |
2020年 | 137篇 |
2019年 | 134篇 |
2018年 | 156篇 |
2017年 | 148篇 |
2016年 | 245篇 |
2015年 | 368篇 |
2014年 | 426篇 |
2013年 | 510篇 |
2012年 | 640篇 |
2011年 | 660篇 |
2010年 | 353篇 |
2009年 | 313篇 |
2008年 | 374篇 |
2007年 | 398篇 |
2006年 | 354篇 |
2005年 | 318篇 |
2004年 | 266篇 |
2003年 | 282篇 |
2002年 | 267篇 |
2001年 | 70篇 |
2000年 | 78篇 |
1999年 | 102篇 |
1998年 | 71篇 |
1997年 | 73篇 |
1996年 | 49篇 |
1995年 | 53篇 |
1994年 | 46篇 |
1993年 | 31篇 |
1992年 | 37篇 |
1991年 | 31篇 |
1990年 | 31篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 28篇 |
1982年 | 17篇 |
1981年 | 14篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1976年 | 22篇 |
1975年 | 12篇 |
1974年 | 17篇 |
1971年 | 8篇 |
1960年 | 8篇 |
排序方式: 共有7914条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
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
6.
An unusual case of neurofibrosarcoma of the cranio-orbital-maxillary region was resected by a combined neurosurgical and plastic surgical team. The resulting defect was reconstructed in one stage with a free rectus abdominis myocutaneous flap, obviating the need for subsequent prosthetic obturation of the maxillary defect. This reconstructive technique expedited the patient's convalescent period, allowing him to return to work 3 weeks following surgery. Wound healing was uneventful, and the cosmetic result was acceptable to the patient. 相似文献
7.
Summary Auxin-induced highly vacuolated thin-walled callus cells of several plant species, when ruptured, released large numbers of subcellular units most of which were enucleate. These enucleate microplasts are surrounded by an inner membrane of the cell, most probably derived from the tonoplast. When microplasts isolated fromSaintpaulia callus were cultured in a medium supplemented with growth substances they formed a thin wall and underwent budding. Microplasts could be useful for various studies in plant cell biology and for genetic manipulations. 相似文献
8.
Jerome S. Kaye Rachel McMaster-Kaye 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,696(1):44-51
Typical somatic cell type histones are lost from the nucleus during late spermiogenesis in the house cricket; they are replaced by unusual basic proteins specific to the spermatid. We wish to characterize these proteins because they appear to determine the unusual chromatin structures of the spermatid. Molecular weights of the unusual basic proteins were estimated by chromatographing them on Bio-Gel A 0.5 M agarose columns eluted with 6 M guanidine hydrochloride. Two proteins named TH1 and TH2 have molecular weights in the range spanned by the somatic histones. The molecular weight of TH1 is 17 500 and that of TH2 is 15 500. Three additional spermatid proteins were also analyzed by molecular weight determination. They are called here protamines A, B and C, and they have molecular weights in the range typical of protamines. That of A is 6200, of B is 5500 and of C is 3800. They span the range from the large protamines typical of mammalian sperm to the small protamines of salmonid fish. The molecular weights of the TH proteins were also examined by electrophoresis on SDS-polyacrylamide gels. Amino acid compositions determined for TH1 and TH2 show that both are basic proteins rich in arginine relative to lysine. Their compositions are histone-like, but they appear to be distinct histone types rather than variant forms of the somatic histones. 相似文献
9.
Rachel M. Haywood Andrew W. D. Claxson Geoffrey E. Hawkes David P. Richardson Declan P. Naughton Gregory Coumbarides Jane Hawkes Edward J. Lynch Martin C. Grootveld 《Free radical research》1995,22(5):441-482
High field (400 and 600 MHz) proton NMR spectroscopy has been employed to investigate the thermally-induced autoxidation of glycerol-bound polyunsaturated fatty acids present in intact culinary frying oils and fats. Heating of these materials at 180°C for periods of 30, 60 and 90 min. generated a variety of peroxidation products, notably aldehydes (alkanals, trans-2-alkenals and alka-2, 4-dienals) and their conjugated hydroperoxydiene precursors. Since such aldehydes appear to be absorbed into the systemic circulation from the gut in vivo, the toxicological significance of their production during standard frying practices is discussed. 相似文献
10.
Rachel Lacroix 《Evolution; international journal of organic evolution》2020,74(9):2168-2169
It is recognized that biodiversity changes across the planet latitudinally; however, the timing of and reasons for diversity loss at higher latitudes are not well understood. Meseguer and Condamine investigate phylogenies and fossil evidence of reptilian species and determine that global warming and cooling events allowed asymmetric extinction and dispersion across latitudes, suggesting a hypothesis where climate profoundly shapes the latitudinal diversity gradient in certain taxa. 相似文献