首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1921篇
  免费   125篇
  国内免费   42篇
儿科学   2篇
妇产科学   223篇
基础医学   257篇
口腔科学   1篇
临床医学   92篇
内科学   32篇
皮肤病学   10篇
神经病学   9篇
特种医学   33篇
外科学   927篇
综合类   219篇
预防医学   113篇
眼科学   1篇
药学   85篇
中国医学   77篇
肿瘤学   7篇
  2024年   4篇
  2023年   12篇
  2022年   28篇
  2021年   67篇
  2020年   51篇
  2019年   52篇
  2018年   48篇
  2017年   41篇
  2016年   61篇
  2015年   58篇
  2014年   91篇
  2013年   99篇
  2012年   87篇
  2011年   87篇
  2010年   98篇
  2009年   80篇
  2008年   76篇
  2007年   87篇
  2006年   111篇
  2005年   73篇
  2004年   65篇
  2003年   71篇
  2002年   50篇
  2001年   51篇
  2000年   39篇
  1999年   32篇
  1998年   21篇
  1997年   28篇
  1996年   37篇
  1995年   34篇
  1994年   39篇
  1993年   20篇
  1992年   21篇
  1991年   34篇
  1990年   34篇
  1989年   30篇
  1988年   21篇
  1987年   14篇
  1986年   18篇
  1985年   15篇
  1984年   20篇
  1983年   17篇
  1982年   6篇
  1981年   19篇
  1980年   11篇
  1979年   13篇
  1978年   7篇
  1975年   3篇
  1974年   2篇
  1972年   2篇
排序方式: 共有2088条查询结果,搜索用时 15 毫秒
41.
Our purpose was to review and analyse the impact of pyrethroids and organophosphates exposure on human semen parameters. A comprehensive literature search was performed through MEDLINE via PubMed, Scopus and Webscience. Only cohort studies examining semen parameters in workers or general populations exposed to pyrethroids or organophosphates were included. Ejaculate volume, sperm count, concentration, motility, viability, normal morphology and seminal pH alterations were pooled using the Cochran–Mantel–Haenszel Method with the random effect model and expressed as weighted mean difference, risk ratios, 95% confidence intervals and p-values. Seven cross-sectional studies regarding pyrethroids were included. Four of them were eligible for meta-analysis. The only parameter affected by pyrethroid exposure was normal sperm morphology (WMD-7,61%, 95%CI –11,92 to −3,30;p = 0,0,005). Nine studies were selected to evaluate the impact of organophosphates on semen parameters with six of them eligible for meta-analysis. A significant reduction was detected for the following: ejaculate volume (WMD −0,47ml, 95%CI −0,69 to −0,25; p < 0,0001), sperm count (WMD-40,03, 95%CI −66,81 to −13,25;p = 0,003), concentration (WMD-13,69 x10⁶/mL, 95%CI −23, 27 to-4,12;p = 0,005) and motility (WMD −5,70%, 95%CI −12,89 to 1,50;p = 0,12). Despite the increase in sperm abnormality, it has been shown that pyrethroids are unrelated to reduced sperm quality. However, the negative association of organophosphates with spermatogenesis is noteworthy.  相似文献   
42.
IntroductionSemen induces mucosal changes in the female reproductive tract to improve pregnancy outcomes. Since semen‐induced alterations are likely short‐lived and genital inflammation is linked to HIV acquisition in women, we investigated the contribution of recent semen exposure on biomarkers of genital inflammation in women at high HIV risk and the persistence of these associations.MethodsWe assessed stored genital specimens from 152 HIV‐negative KwaZulu‐Natal women who participated in the CAPRISA 008 trial between November 2012 and October 2014. During the two‐year study period, 651 vaginal specimens were collected biannually (mean five samples per woman). Cervicovaginal lavage (CVL) was screened for prostate‐specific antigen (PSA) by ELISA, whereas Y‐chromosome DNA (YcDNA) detection and quantification were conducted by RT‐PCR, representing semen exposure within 48 hours (PSA+YcDNA+) and semen exposure within three to fifteen days (PSA−YcDNA+). Soluble protein concentrations were measured in CVLs by multiplexed ELISA. T‐cell frequencies were assessed in cytobrushes by flow‐cytometry, and vulvovaginal swabs were used to detect common vaginal microbes by PCR. Linear mixed models adjusting for factors associated with genital inflammation and HIV risk were used to assess the impact of semen exposure on biomarkers of inflammation over multiple visits.ResultsHere, 19% (125/651) of CVLs were PSA+YcDNA+, 14% (93/651) were PSA−YcDNA+ and 67% (433/651) were PSA−YcDNA−. Semen exposure was associated with how often women saw their partners, the frequency of vaginal sex in the past month, HSV‐2 antibody detection, current gonorrhoea infection and Nugent Score. Both PSA detection (PSA+YcDNA+) and higher cervicovaginal YcDNA concentrations predicted increases in several cytokines, barrier‐related proteins (MMP‐2, TIMP‐1 and TIMP‐4) and activated CD4+CCR5+HLA‐DR+ T cells (β = 0.050; CI 0.001 to 0.098; p = 0.046) and CD4+HLA‐DR+ T cells (β = 0.177; CI 0.016 to 0.339; p = 0.032) respectively. PSA detection was specifically associated with raised pro‐inflammatory cytokines (including IL‐6, TNF‐α, IP‐10 and RANTES), and with the detection of BVAB2 (OR = 1.755; CI 1.116 to 2.760; p = 0.015), P. bivia (OR = 1.886; CI 1.102 to 3.228; p = 0.021) and Gardnerella vaginalis (OR = 1.815; CI 1.093 to 3.015; p = 0.021).ConclusionsMore recent semen exposure was associated with raised levels of inflammatory biomarkers and the detection of BV‐associated microbes, which declined by three to fifteen days of post‐exposure. Although transient, semen‐induced alterations may have implications for HIV susceptibility in women.  相似文献   
43.
Dr.  E. Bendvold  A. Aanesen 《Andrologia》1990,22(1):42-54
The CellSoft automated semen analysis system was studied concerning the effect of gray scale (GSc) variation on cell motion parameters and to establish an appropriate setting for human spermatozoal sizes (PixMin and PixMax) based on the cell's instant velocities (InsVels). GSc could be set within a range from "optimum" till +10 units without, except for curvilinear velocity, the CellSoft generated sperm measures being altered (p greater than 0.05). The aspect of a sample specific GSc setting according to certain criteria is stressed. Considering the area of immobilized spermatozoa (at GSc + 20) and of motile cells with low InsVel, PixMin should be set at 3 pixels. Correspondingly, the InsVel determined setting for PixMax (at a maximum velocity threshold set at 200 microns/sec.) was 28 pixels. A final recommendation on the setting for cell sizes can, however, only be determined in considering sizes of nonsperm seminal elements and in studying the appropriate setting for the maximum velocity threshold.  相似文献   
44.
无精子症患者精液检查与血清性激素含量的分析   总被引:1,自引:0,他引:1  
目的:对无精子症病因进行诊断分析.方法:对28例无精子症患者进行精液分析和用放射免疫法检测其血清中性激素含量,并结合文献进行病因分析、讨论.结果:无精子症患者精液量、PH值、液化时间及果糖含量等均显著下降,与对照组比较有非常显著差异(P<0.01);无精子患者的果糖含量与精液量、PH值之间呈正相关(P<0.01),随着果糖含量的下降,其精液量和PH值也会下降;无精子症患者血清以配子生成素(FSH)、黄体生成素(LH)显著高于对照组(P<0.01),睾酮(T)、雌二醇(E2)、催乳素(PRL)与对照组比较无显著差异(P>0.05).结论:无精子症患者要依据果糖含量、精液量、PH值、液化时间以及性激素的高低等综合分析才能正确地诊断其产生无精子的原因.  相似文献   
45.
60例男性不良患者精液标本,采用一种免疫组织化学技术分析精液中白细胞类型和数量。结果显示高浓度的中性粒细胞和单核/巨噬细胞可减少精液量;高浓度的中性粒细胞对精子总数和总活动精子数有降低作用。高浓度的T淋巴细胞可显著的降低精子活率。  相似文献   
46.
47.
Purpose This study examined sperm motion parameters as measured by computerized automated semen analysis before and after a Percoll wash and determined if differences in any parameter were correlated with fertility subsequent to intrauterine insemination (IUI).Results Total motile sperm decreased following the washing procedure from 79.0 ± 9.0 to 37.2 ± 7.6 million sperm. Motility increased from a mean of 43.4% to 61.7% (P<0.001). Other motility parameters also changed significantly (P<0.001) as follows: curvilinear velocity (VCL), 43.4 to 61.7 m/s; straight-line velocity (VSL), 21.3 to 26.7 m/s; linearity 53.1 to 45.2%; lateral head displacement (ALH), 2.97 to 3.94 m. Similar changes occurred following a swim-up preparation, although changes in mean motility, VCL, and ALH were significantly greater when compared to Percoll. The postwash changes were not accounted for merely by time lapse in preparation since reanalyzed untreated controls did not show the same changes in motion parameters. Prewash linearity in those specimens which resulted in pregnancies was greater than in those which did not (P=0.28). No other significant differences in pre-or post-Percoll washed sperm motion parameters were found between pregnant vs nonfertile cycles.Conclusion Following Percoll wash all CASA-generated motility parameters were significantly altered, but there was little association between these parameters and pregnancy achieved in IUI cycles.Presented at the 50th Annual Meeting of the American Fertility Society, San Antonio, Texas, November 5–10, 1994.  相似文献   
48.
长期饮酒对男性生殖系统功能影响   总被引:1,自引:0,他引:1  
目的探讨饮酒对男性生殖系统的损害及其机理。方法选择45名男性饮酒者和9名慢性酒精中毒者为研究对象,以15名不吸烟不接触毒物的男性为对照组。结果长期大量饮酒和酒精中毒者血清中T和CS水平下降,而LH和FSH水平升高;精浆和精子中LDH,LDH-x和G-6PD活力下降,以LDH-x下降为敏感;精子数量和活动精子年均降低,精子畸形率及异常精液检出率均升高。上述各指标与对照组比较差异均有高度显著性(P<0.01)。结论长期饮酒可损害男性生殖系统功能。  相似文献   
49.
猪精液抑制素的制备及其放射免疫分析   总被引:5,自引:0,他引:5  
本文报道以猪精液为原料制备的抑制素的生物活性、氨基酸组成、分子量以及抑制素的放射免疫分析。新鲜猪精液经乙醇沉淀、丙酮清洗和Sephadex G-100凝胶过滤,获得抑制素活性组分UⅡ。生物测定表明:所得抑制素单位重量的生物活性稍高于Chari氏牛精液抑制素纯品的活性;UⅡ含17种氨基酸,分子量为18,500道尔顿,用UⅡ免疫家兔,获得亲和为强(Ka=6.58×10~(10)L/M)、效价高的特异抗血清,终稀释度可达1:100,000;用双抗体法进行猪精液抑制素放射免疫分析,检测灵敏度为87.5微微克,经Logit转换,标准曲线的直线化较好。按Cerceo效点法综合评价,积分值达28,表明此法较优。  相似文献   
50.
Summary A simple qualitative method for identification of seminal stains based on a high activity of -glutamyltransferase (-GTP) in human semen is described. It employs the release of -naphthylamine from N--glutamyl--naphthylamide by the -GTP action; -naphthylamine couples with Fast Garnet GBC salt to produce a strong brownish-red color. The data on its simplicity, specificity, and stability show that the present method is suitable for medicolegal examination of seminal stains as a preliminary test.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号