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   2722篇
  免费   380篇
  国内免费   244篇
耳鼻咽喉   21篇
儿科学   27篇
妇产科学   7篇
基础医学   312篇
口腔科学   35篇
临床医学   125篇
内科学   225篇
皮肤病学   19篇
神经病学   92篇
特种医学   42篇
外科学   111篇
综合类   376篇
预防医学   243篇
眼科学   35篇
药学   577篇
中国医学   1071篇
肿瘤学   28篇
  2024年   18篇
  2023年   72篇
  2022年   120篇
  2021年   142篇
  2020年   102篇
  2019年   127篇
  2018年   98篇
  2017年   137篇
  2016年   132篇
  2015年   130篇
  2014年   185篇
  2013年   237篇
  2012年   235篇
  2011年   218篇
  2010年   161篇
  2009年   116篇
  2008年   128篇
  2007年   125篇
  2006年   116篇
  2005年   92篇
  2004年   68篇
  2003年   71篇
  2002年   62篇
  2001年   60篇
  2000年   37篇
  1999年   32篇
  1998年   34篇
  1997年   31篇
  1996年   15篇
  1995年   11篇
  1994年   22篇
  1993年   16篇
  1992年   27篇
  1991年   13篇
  1990年   17篇
  1989年   18篇
  1988年   11篇
  1987年   11篇
  1986年   6篇
  1985年   13篇
  1984年   15篇
  1983年   16篇
  1982年   12篇
  1981年   6篇
  1980年   8篇
  1979年   4篇
  1978年   4篇
  1977年   3篇
  1976年   4篇
  1973年   3篇
排序方式: 共有3346条查询结果,搜索用时 15 毫秒
11.
用木瓜蛋白酶对方格星虫(Sipunculus nudus)进行酶促水解,并对酶解物冻干粉的成分进行了分析,其中粗蛋白质量分数为69.02%,多肽质量分数为60.60%,肽的平均链长为3.73个氨基酸残基,肽分子的平均相对分子质量为447.6;游离氨基酸占5.27%。氨基酸分析结果显示,方格星虫酶解物含有17种氨基酸(色氨酸未测),其中人体必需氨基酸含量较高,占总氨基酸数的30.62%。方格星虫酶解物中还含有P、Fe、Mg、Mn、Zn、Cu、Se等至少12种矿质元素,以及含有抗氧化作用的营养成分,并通过动物试验证明了方格星虫酶解物具有显著的抗氧化作用。方格星虫酶解物可用于食品添加或用作功能性食品。  相似文献   
12.
钱国英  朱秋华 《营养学报》2003,25(4):446-448
鳖一直被视作为滋补佳品。但以短期快速促生长方式生产的养殖中华鳖的质量与野生中华鳖有区别 [1 ] ,其主要原因是生长时间的差异 ,还是养殖环境等其他因素所造成 ,尚未见报道。本研究通过对相近环境条件下不同年龄的商品鳖和不同环境中同一年龄的商品鳖的营养成分的比较 ,了解养殖周期对商品鳖营养成分的影响 ,为选择合理的养殖周期提供理论依据。1 材 料 与 方 法  由余杭生泰中华鳖养殖有限公司 (YT)提供 2、3龄相同养殖条件仿生养殖中华鳖各 6只 ,2龄中华鳖体重 450~ 50 0 g,3龄中华鳖体重 51 5~ 552 g,均为雄性。养殖池塘面…  相似文献   
13.
采用原子吸收分光光度法、高效液相色谱等方法对秦巴山区野生与栽培猪苓菌核的氨基酸、水分、灰分、粗蛋白、粗脂肪、粗纤维、矿质元素、猪苓多糖等主要成分及含量进行测定.结果表明,野生和栽培猪苓在所测定的17种氨基酸中,7种必需氨基酸占氨基酸总量的质量分数分别为33.8%,23.6%.每100g野生与栽培猪苓菌核中水分质量分别为13.22g,11.94g;灰分质量分别为2.86g,2.61g;粗蛋白质量分别为6.87g,4.91g;粗纤维质量分别为27.62g,26.02g;粗脂肪质量分别为1.87g,1.71g;每100g野生和栽培猪苓质量分别为1.87g,1.71g;猪苓多糖质量分别为0.51g,0.40g.  相似文献   
14.
Problems that can occur when single implants are utilized to restore first molar teeth include the frequent loosening of screws, as well as screws and/or implant breakage. These may result from torquing and rotational movements of the prosthesis during masticatory and parafunctional mandibular movements. When sufficient bone and mesio-distal restorative space is present, the placement of two implants should be considered.  相似文献   
15.
16.
Rhombencephala from rat embryos were processed as whole-mounts for immunocytochemical detection of monoaminergic cell populations, using antibodies to tyrosine hydroxylase (TH) and serotonin (5-HT). Specific advantages of the whole-mount technique over the classical serial-section method were that even isolated immunoreactive (IR) cells could be detected easily, and three-dimensional relationships could be ascertained without the need for serial reconstruction. Embryos between embryonic days (E) 12 and 16 (the day following nocturnal mating being considered as E1) were used in this study. Both TH and 5-HT immunoreactivities were already detectable at E12, even in the smallest embryos (crown-rump length: 6 mm), but there was a striking difference in the number and regional distribution of these two types of IR cells. TH was expressed in several cell groups located in the rostral rhombencephalon (the presumed anlage of the A4-7 complex) as well as in the caudal rhombencephalon (the presumed anlagen of groups A1-2 and C1-3), whereas 5-HT was expressed in very few cells located near the rostral border of the rhombencephalon (presumed anlage of the B4-9 complex). Although the three-dimensional distribution of the TH-IR cell groups underwent some modifications during the period studied, its general pattern remained relatively stable after E12. This contrasted with the sequential appearance of the 5-HT-IR cell groups and their spatial transformations during this period. Using the rhombencephalic isthmus as a landmark, we found that conspicuous 5-HT-IR fibre bundles penetrated into the mesencephalon from E13 onwards, but that the 5-HT IR cell bodies were exclusively located caudal to the borderline between the mesencephalon and the rhombencephalon (the rhombencephalic isthmus). We therefore suggest the term "rostral rhombencephalic raphe nuclei" for the rostral 5-HT cell groups instead of "mesencephalic raphe nuclei," which is a misnomer. Close spatial association between TH and 5-HT-IR elements was observed mainly in the caudal rhombencephalon, where 5-HT-IR fibres coursed through an area containing numerous TH-IR cell bodies (the presumed anlagen of groups A1-2 and C1-3).  相似文献   
17.
A solid phase radioimmunoassay has been compared with an enzyme-linked immunosorbent assay (ELISA) for efficacy in measuring anti-chromatin antibodies. The low backgrounds achieved with the radioimmunoassay method produced a high signal-to-noise ratio and enabled detection of the human test antiserum at a dilution of 1:102,400. By contrast, the ELISA could detect the same antiserum only at a dilution of 1:3200 and above. The radioimmunoassay was consistently more sensitive than the ELISA for detection of anti-chromatin antibodies in a number of human and mouse sera and ascites fluid containing a monoclonal antibody. Factors affecting sensitivity in both assays are discussed.  相似文献   
18.
Sephadex beads were placed carefully in the uterus on days 2 and 3 and left for 6 to 8 h to absorb uterine secretion. The beads were then removed with volatile silicon oil and mounted on small pieces of nitrocellulose paper. Immuno-staining of these bead blots showed they contained the complement components C1q, C3, C4, and C5. We demonstrated that complement component C3 in the uterine secretion could be activated and deposited on model immune complexes, and also that antibody-coated erythrocytes were lysed in utero, that is, a membrane attack complex was produced. Thus, the mouse uterine secretion at the preimplantation stage contains a functionally active complement system.  相似文献   
19.
Macrophages from peripheral blood of leprosy patients, both multi-bacillary and paucibacillary are unable to kill phagocytosed Mycobacterium leprae due to their inability to produce superoxide (O2-) and hydroxyl radicals (OH.). The macrophages from healthy individuals are able to kill M. leprae along with release of O2- and OH. radicals. The deficiency in the macrophages of both types of leprosy patients is removed by activation of these cells when exposed to a culture supernatant obtained after stimulation of peripheral blood mononuclear cells from the same patients with delipidified cell components of M. leprae which are most likely cell wall proteins. The activation of macrophages also leads to recognition of whole live M. leprae as an antigen by cells from lepromatous patients. This activation of the phagocytes by delipidified cell components is blocked by cyclosporin A, indicating the possible role of several steps involved in immune activation of cells. The observations thus indicate the significant ability of delipidified cell components to eliminate the deficiencies in the macrophages from leprosy patients and restore them to behave like the cells from healthy individuals. Considering all these, it is suggested that delipidified cell components could be potential modulators, and are probably capable of functioning as a vaccine for leprosy.  相似文献   
20.
Z. N. Chang    L. C. Tsai    C. W. Chi    M. C. Wang    H. D. Shen    D. T. LEE  S. H. Han 《Allergy》1991,46(7):520-528
A panel of 16 monoclonal antibodies (MoAbs) directed against Bermuda grass (Cynodon dactylon) pollen (BGP) were generated for identification and purification of the major allergenic components of the eliciting antigen (Ag). Radioimmunoprecipitation (RIP) analysis revealed that there were at least eight antigenic components with molecular weights (MW) ranging from 12 kilodalton (12 kDa) to 200 kDa. Each of these components has distinct biochemical characteristics based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing (IEF). Among them, Cyn d Bd67K and Cyn d Bd58K were basic proteins, Cyn d Bd35K consisted of at least four isomeric components with isoelectric points ranging from 6.2 to 7.2. The other antigens (Cyn d Bd68K, 48K, 38K, Cyn d Bd200K, Cyn d Bd46K, Cyn d Bd25K and Cyn d Bd12K) were all acidic proteins. The IgE binding capacity of all these antigens was determined with sera from 11 BGP-allergics by using a modified radioallergosorbent test. All but one of the antigens (Cyn d Bd200K) were found to react with human IgE from sera of BGP-allergic patients. Among those human IgE-binding molecules, Cyn d Bd35K reacted with allergic sera most frequently (10 of 11), followed by Cyn d Bd58K (8 of 11) and Cyn d Bd46K (7 of 11) respectively. Our results suggest that Cyn d Bd35K, Cyn d Bd58K, and Cyn d Bd46K are major allergens of BGP, and the MoAbs we obtained should be valuable tools for further purification of these allergens.  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