全文获取类型
收费全文 | 25873篇 |
免费 | 1946篇 |
国内免费 | 64篇 |
专业分类
耳鼻咽喉 | 230篇 |
儿科学 | 732篇 |
妇产科学 | 530篇 |
基础医学 | 3094篇 |
口腔科学 | 358篇 |
临床医学 | 2587篇 |
内科学 | 5049篇 |
皮肤病学 | 700篇 |
神经病学 | 2343篇 |
特种医学 | 1009篇 |
外国民族医学 | 1篇 |
外科学 | 3962篇 |
综合类 | 411篇 |
一般理论 | 60篇 |
预防医学 | 2241篇 |
眼科学 | 849篇 |
药学 | 1769篇 |
中国医学 | 18篇 |
肿瘤学 | 1940篇 |
出版年
2021年 | 343篇 |
2020年 | 227篇 |
2019年 | 344篇 |
2018年 | 426篇 |
2017年 | 365篇 |
2016年 | 397篇 |
2015年 | 447篇 |
2014年 | 698篇 |
2013年 | 1021篇 |
2012年 | 1523篇 |
2011年 | 1572篇 |
2010年 | 890篇 |
2009年 | 805篇 |
2008年 | 1519篇 |
2007年 | 1571篇 |
2006年 | 1560篇 |
2005年 | 1631篇 |
2004年 | 1588篇 |
2003年 | 1494篇 |
2002年 | 1476篇 |
2001年 | 411篇 |
2000年 | 322篇 |
1999年 | 354篇 |
1998年 | 344篇 |
1997年 | 316篇 |
1996年 | 286篇 |
1995年 | 267篇 |
1994年 | 235篇 |
1993年 | 231篇 |
1992年 | 274篇 |
1991年 | 251篇 |
1990年 | 234篇 |
1989年 | 232篇 |
1988年 | 208篇 |
1987年 | 193篇 |
1986年 | 188篇 |
1985年 | 221篇 |
1984年 | 211篇 |
1983年 | 214篇 |
1982年 | 239篇 |
1981年 | 247篇 |
1980年 | 204篇 |
1979年 | 162篇 |
1978年 | 171篇 |
1977年 | 165篇 |
1976年 | 108篇 |
1975年 | 130篇 |
1974年 | 143篇 |
1973年 | 108篇 |
1972年 | 92篇 |
排序方式: 共有10000条查询结果,搜索用时 25 毫秒
21.
Greg Guest Laura Johnson Holly Burke Reathe Rain-Taljaard Lawrence Severy Claire von Mollendorf Lut Van Damme 《AIDS education and prevention》2007,19(4):310-320
If proven effective, vaginal microbicides and diaphragms will likely be part of a larger HIV prevention model that includes condoms and other prevention strategies. It is, therefore, important to understand how introducing new prevention methods may affect overall patterns of sexual risk behavior. Data presented were collected as part of a safety and feasibility study of ACIDFORM gel with a diaphragm among 120 women in South Africa. Interviews were administered at enrollment and months 1, 3, 5, and 6 of the trial. Focus groups were conducted at trial exit. Frequency of sex increased significantly after enrollment. This increase appears to be owing to perceived protection from HIV and greater sexual pleasure afforded by the gel. Male condom use was high overall but increased significantly from enrollment. Data suggest this is because of increased partner involvement, increased negotiating power afforded by study participation, and provision of free condoms perceived to be of high quality. 相似文献
22.
Lawrence S Prince Heather I Dieperink Victor O Okoh German A Fierro-Perez Roger L Lallone 《Developmental dynamics》2005,233(2):553-561
We tested the hypothesis that innate immune signaling in utero could disrupt the structural development of the fetal lung, contributing to the pathogenesis of bronchopulmonary dysplasia. Injection of Escherichia coli lipopolysaccharide (LPS) into the amniotic fluid of E15 BALB/cJ mice increased the luminal volume density of fetal mouse lungs at embryonic day (E) 17 and E18. LPS also increased luminal volume and decreased distal lung branching in fetal mouse lung explants. This effect required NF-kappaB activation and functional Toll-Like Receptor 4. Airway branching may require fibronectin-dependent epithelial-mesenchymal interactions, representing a potential target for innate immune signaling. Anti-fibronectin antibodies and LPS both blocked distal lung branching. By immunofluorescence, fibronectin localized to the clefts between newly formed airways but was restricted to peripheral mesenchymal cells in LPS-exposed explants. These data suggest that LPS may alter the expression pattern of mesenchymal fibronectin, potentially disrupting epithelial-mesenchymal interactions and inhibiting distal airway branching and alveolarization. This mechanism may link innate immune signaling with defects in structural development of the fetal lung. 相似文献
23.
He Li Lawrence M Schopfer Florian Nachon Marie-Thérèse Froment Patrick Masson Oksana Lockridge 《Toxicological sciences》2007,100(1):136-145
Some organophosphorus compounds are toxic because they inhibit acetylcholinesterase (AChE) by phosphylation of the active site serine, forming a stable conjugate: Ser-O-P(O)-(Y)-(XR) (where X can be O, N, or S and Y can be methyl, OR, or SR). The inhibited enzyme can undergo an aging process, during which the X-R moiety is dealkylated by breaking either the P-X or the X-R bond depending on the specific compound, leading to a nonreactivatable enzyme. Aging mechanisms have been studied primarily using AChE. However, some recent studies have indicated that organophosphate-inhibited butyrylcholinesterase (BChE) may age through an alternative pathway. Our work utilized matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry to study the aging mechanism of human BChE inhibited by dichlorvos, echothiophate, diisopropylfluorophosphate (DFP), isomalathion, soman, sarin, cyclohexyl sarin, VX, and VR. Inhibited BChE was aged in the presence of H2O18 to allow incorporation of (18)O, if cleavage was at the P-X bond. Tryptic-peptide organophosphate conjugates were identified through peptide mass mapping. Our results showed no aging of VX- and VR-treated BChE at 25 degrees C, pH 7.0. However, BChE inhibited by dichlorvos, echothiophate, DFP, soman, sarin, and cyclohexyl sarin aged exclusively through O-C bond cleavage, i.e., the classical X-R scission pathway. In contrast, isomalathion aged through both X-R and P-X pathways; the main aged product resulted from P-S bond cleavage and a minor product resulted from O-C and/or S-C bond cleavage. 相似文献
24.
Hua Tan Jena Derrick Jin Hong Corneliu Sanda William M Grosse Howard J Edenberg Milton Taylor Scott Seiwert Lawrence M Blatt 《Journal of interferon & cytokine research》2005,25(10):632-649
A role for type II interferon (IFN-gamma) in resolving viral infection is suggested by the correlation of hepatitis C virus (HCV) clearance with enhancement of IFN-gamma-producing activated T cells in the resolution of acute HCV infection. Using vesicular stomatitis virus (VSV), a synergistic direct antiviral effect was documented using IFN-gamma1b and a potent, consensus type I IFN (IFN alfacon-1). Global expression profiling following EC50 exposure to IFN alfacon-1, IFN-gamma1b, or a cocktail of the two allowed the antiviral state to be correlated with induction of a subset of IFN-stimulated genes (ISGs). Genes identified through this analysis corresponded to classic antiviral components, ISGs more recently associated with direct antiviral functions, as well as expressed sequence tags (ESTs) and hypothetical proteins. The magnitude of these antiviral EC50-correlated expression events in human hepatoma (Huh7) cells exposed to clinically relevant doses of IFN alfacon-1, IFN-gamma1b, or a cocktail of the two was also probed because the standard of care for patients with chronic hepatitis C is type I IFN-containing regimens. Relative to type I IFNs used alone, the addition of type II IFN caused enhanced expression not only of many of the genes correlated with the direct antiviral state but also of genes involved in (1) antigen presentation to cytotoxic T lymphocytes (CTLs), (2) macrophage, natural killer (NK), and T helper 1 (Th1) cell recruitment and activation, (3) complement system function, (4) apoptosis, and (5) ISGs with unknown functions. As many of these processes are correlated clinically with resolution of chronic HCV infection, the combined use of these IFNs could display a beneficial effect on viral clearance in patients infected with HCV and other viruses through enhancement of one of these processes or of the direct antiviral state. 相似文献
25.
26.
27.
28.
29.
Anne A. Lawrence 《Archives of sexual behavior》2009,38(6):1050-1056
30.
Topical Metronidazole Gel 总被引:1,自引:0,他引:1
Joseph A. Witkowski M.D. Lawrence Charles Parish M.D. 《International journal of dermatology》1991,30(9):660-661
Ten putrid-smelling decubitus ulcers were successfully treated with metronidazole gel. Anaerobes were cultured from five ulcers and Wood's light examination was positive in four ulcers before treatment. The odor was eliminated after 36 hours of therapy. All results of post-treatment cultures of anaerobes and Wood's light examinations were negative. 相似文献