全文获取类型
收费全文 | 25576篇 |
免费 | 1443篇 |
国内免费 | 1038篇 |
专业分类
耳鼻咽喉 | 76篇 |
儿科学 | 471篇 |
妇产科学 | 501篇 |
基础医学 | 6405篇 |
口腔科学 | 294篇 |
临床医学 | 2220篇 |
内科学 | 2939篇 |
皮肤病学 | 354篇 |
神经病学 | 869篇 |
特种医学 | 512篇 |
外国民族医学 | 4篇 |
外科学 | 855篇 |
综合类 | 3301篇 |
现状与发展 | 2篇 |
预防医学 | 1899篇 |
眼科学 | 658篇 |
药学 | 4120篇 |
2篇 | |
中国医学 | 676篇 |
肿瘤学 | 1899篇 |
出版年
2024年 | 22篇 |
2023年 | 166篇 |
2022年 | 379篇 |
2021年 | 480篇 |
2020年 | 534篇 |
2019年 | 542篇 |
2018年 | 478篇 |
2017年 | 545篇 |
2016年 | 653篇 |
2015年 | 676篇 |
2014年 | 1188篇 |
2013年 | 1519篇 |
2012年 | 1285篇 |
2011年 | 1546篇 |
2010年 | 1148篇 |
2009年 | 1171篇 |
2008年 | 1180篇 |
2007年 | 1273篇 |
2006年 | 1135篇 |
2005年 | 1134篇 |
2004年 | 1072篇 |
2003年 | 926篇 |
2002年 | 858篇 |
2001年 | 751篇 |
2000年 | 656篇 |
1999年 | 596篇 |
1998年 | 563篇 |
1997年 | 573篇 |
1996年 | 520篇 |
1995年 | 538篇 |
1994年 | 409篇 |
1993年 | 387篇 |
1992年 | 365篇 |
1991年 | 314篇 |
1990年 | 293篇 |
1989年 | 236篇 |
1988年 | 244篇 |
1987年 | 198篇 |
1986年 | 208篇 |
1985年 | 270篇 |
1984年 | 209篇 |
1983年 | 189篇 |
1982年 | 160篇 |
1981年 | 116篇 |
1980年 | 105篇 |
1979年 | 91篇 |
1978年 | 45篇 |
1977年 | 39篇 |
1976年 | 12篇 |
1974年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
R. Rybar P. Markova Z. Veznik L. Faldikova M. Kunetkova A. Zajicova V. Kopecka & J. Rubes 《Andrologia》2009,41(3):141-149
Damage to the genetic component of spermatozoa seems to play the main role in a majority of cases where current approaches fail to reveal the specific cause of male infertility. In this study, we compared semen quality in men assigned to two defined groups: men from couples with unexplained infertility – idiopathic infertility (A) and young men with no experiences of infertility (B). All samples were examined by standard ejaculate analysis and sperm chromatin structure assay (SCSA). Sperm chromatin damage was significantly higher in men from group A than in those from group B. Similar results were obtained by comparison of men from group A (all men were normozoospermic) with normozoospermic men from group B. According to these results, we can suppose that chromatin disorders may be the causal factor of subfertility or infertility in some of these men. No evidence for a strong association between chromatin disorders and standard parameters of ejaculates was found. We failed to confirm a relationship between smoking and sperm quality in men from any of the investigated groups. SCSA is a method that facilitates the identification of infertile men who otherwise show normal semen variables. 相似文献
32.
目的对纳米锶磷灰石进行体外细胞毒性试验,评价其生物安全性,为将其应用于骨折临床修复奠定基础。方法将不同浓度的纳米锶磷灰石浸提液与小鼠成纤维细胞L929体外共培养2d、4d、7d,倒置相差显微镜下观察细胞的形态变化;用四氮唑盐比色法(MTT)检测,计算细胞相对增殖度,用六级毒性分类法进行评级。结果培养期细胞贴壁生长,形态良好,随着培养天数的增加细胞大量增殖,毒级为0~1级。相同时间点不同浓度的纳米锶磷灰石浸提液的吸光度值无明显差异性(p>0.05)。结论初步证实纳米锶磷灰石具有人体应用的生物安全基础,无细胞毒性。 相似文献
33.
目的 探讨遗传缺陷在无精子、严重少精子症中的检测意义。方法 采用细胞遗传学技术及多重聚合酶链反应(PCR)技术对65例无精子及严重少精子症患者进行染色体核型分析、Y染色体无精子因子(AZF)检测,同时行精索输精管诊察,阴性者行精液果糖定量实验。结果 染色体核型异常8例(12.3%),AZF因子缺失7例(10.8%),输精管缺如2例(3.1%)。结论 遗传学检测在男性无精子、严重少精子症有重要意义。 相似文献
34.
目的 探讨脂蛋白残粒RLP-c作为新的脂质指标的临床意义。方法 采用免疫分离法测定正常对照组(NC)、冠心病组(CHD)和2型糖尿病组(T2DM)的RLP-c水平,并比较RLP-c与其他脂质指标的相关性。结果 CHD组和T2DM组RLP-c水平明显高于NC组(P<0.01),其水平与甘油三脂(TG)和极低密度脂蛋白胆固醇(VLDL-c)高度相关(P<0.01)。结论 RLP-c可用于对动脉粥样硬化的危险性评估。 相似文献
35.
采用~(125)I 标记小鼠抗人IL—2受体(P55)的抗Tac(CD_(25))单克隆抗体,成功地建立了人IL—2受体的免疫放射分析法,动态观察了人外周血淋巴细胞经PHA 刺激24、48和72h 后IL—2受体表达的时间曲线,通过Scatchard 作图分析表明~(125)I—抗Tac 单克隆抗体与PHA 活化的上述三个时间点的T 淋巴细胞的最大结合容量(B_(max))分别为43000位点/细胞、54000位点/细胞和61000位点/细胞。本研究为临床IL—2受体检测提供一种简便的免疫放射测定法。 相似文献
36.
Eugenia Cordelli Anna Maria Fresegna Alessia D'Alessio Patrizia Eleuteri Marcello Spanò Francesca Pacchierotti Paola Villani 《Toxicological sciences》2007,99(2):545-552
The increasing request of chemical safety assessment demands for the validation of alternative methods to reduce the resort to animal experimentation. Methods that evaluate reproductive toxicity are among those requiring the largest use of animals. Presently, no validated in vitro alternative exists for the assessment of reproductive toxicity. Mammalian sperm are sensitive targets of DNA-reactive chemicals, which form premutagenic adducts. Here, we propose a new method based on comet assay to detect DNA damage induced by potential germ cell mutagens in bull sperm available from assisted reproduction practices. In somatic cells, chemical-induced adducts can be revealed by comet assay that detects DNA breaks produced during adduct repair. Mature sperm, however, are devoid of repair enzymes, and adducts are processed only after fertilization. For this reason, comet assay is not sensitive to detect DNA lesions induced in sperm by most chemicals. To overcome such limitation, we developed a modified comet assay based on the addition of a protein extract from HeLa cells to agarose-embedded sperm on microscopic slides. To test the method, sperm were treated in vitro with methyl methanesulfonate (MMS) or melphalan (MLP) and comet assay was conducted both with and without protein supplementation. No effect of MMS or MLP was detected without protein supplementation; on the contrary, a clear-cut dose-dependent effect was measured after addition of the cell extract. These results represent a proof of concept of a novel in vitro mutagenicity test on sperm that could offer a promising approach to complement previously validated in vivo germ cell genotoxicity assays. 相似文献
37.
Ted Van Noord D. Scott Wright Be-Sheng Kuo 《Journal of pharmaceutical and biomedical analysis》1996,14(12):1709-1716
CAM 4515 and CAM 4750 are new nonpeptide tachykinin NK1 receptor antagonists with different lipophilicities. Two separate, simple, and sensitive HPLC methods for the quantitation of these two compounds in plasma and the evaluation of their oral bioavailability in rats were developed and validated. Extraction of CAM 4515 from plasma involved protein precipitation with acetonitrile, while that for CAM 4750 involved a one-step liquid-liquid extraction with methylene chloride. The analytes in extracts were chromatographed on a C18 column using two different separation buffers, 47% 0.02 M sodium citrate (pH 3.5)-53% acetonitrile for CAM 4515 and 59% 0.02 M potassium phosphate dibasic (pH 7.0)-41% acetonitrile for CAM 4750, and both compounds were detected by fluorescence (excitation 278 nm; emission 342 nm). Stability profiles of both drugs at −20°C or room temperature in plasma and in reconstituted buffers were good. The limit of quantitation for both drugs was 5 ng ml−1 with good linearity from 5 to 1000 ng ml−1 using 100–200 μl of plasma. Excellent precision (relative standard deviation < 8.3%) and accuracy (relative error ± 9.2%) were observed for both CAM 4515 and CAM 4750. Oral bioavailability studies were conducted for each compound in rats receiving a p.o. dose of 20 mg kg−1 and an i.v. dose of 5 mg kg−1. The absolute oral bioavailability of CAM 4750 (80%) was estimated to be 40-fold greater than that of CAM 4515 (2%). The experimental results suggest that incorporation of a pyridine group into the structural backbone may greatly improve bioavailability. 相似文献
38.
ltiswellknownthattheskinofextensivelyburnedcasesthemselvesisinsufficienttoprovidecoverageforwounds.Thoughallogeneicskincancoverthewoundstemporari1y,itwillberejectedwithin2-3weeks.Thiscanthreatenthepatient'slifeifthereisnoenoughautogenousskintoreplacetherejectedoneontime.GreenetalL1]reportedthattheburnwoundsofpatientswithextensiveburnscouldbetreatedbytransplantingepidermalautograftsafterautologousepidermalcellsmulti-plyforthousandsoftimesinvltrowithinashortperiodoftime-Butittakesatleast2-3weeks… 相似文献
39.
40.