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   5294篇
  免费   373篇
  国内免费   1篇
  5668篇
  2023年   25篇
  2022年   62篇
  2021年   159篇
  2020年   95篇
  2019年   100篇
  2018年   159篇
  2017年   120篇
  2016年   164篇
  2015年   238篇
  2014年   301篇
  2013年   388篇
  2012年   435篇
  2011年   457篇
  2010年   268篇
  2009年   242篇
  2008年   295篇
  2007年   342篇
  2006年   305篇
  2005年   267篇
  2004年   243篇
  2003年   231篇
  2002年   200篇
  2001年   50篇
  2000年   35篇
  1999年   34篇
  1998年   44篇
  1997年   29篇
  1996年   22篇
  1995年   37篇
  1994年   27篇
  1993年   33篇
  1992年   21篇
  1991年   16篇
  1990年   24篇
  1989年   15篇
  1988年   12篇
  1987年   11篇
  1986年   12篇
  1985年   18篇
  1984年   15篇
  1983年   10篇
  1982年   14篇
  1981年   11篇
  1979年   10篇
  1978年   7篇
  1977年   10篇
  1976年   9篇
  1975年   9篇
  1974年   6篇
  1970年   7篇
排序方式: 共有5668条查询结果,搜索用时 0 毫秒
41.
The effect of Leu5-enkephalin on growth hormone (GH) and prolactin (PRL) release was studied in vivo in the infant rat and compared to that of morphine. In 10 day-old pups, intracerebroventricular injection of Leu5-enkephalin (50, 75 and 100 μg) resulted in a dose-related increase in plasma GH; morphine was active as GH releaser at the dose of 5 and 10 μg, but not at 2.5 μg. Pretreatment with naloxone (2 mg/kg ip) suppressed the GH-releasing effect of either Leu5-enkephalin (100 μg) or morphine (10 μg). Leu5-enkephalin (75 and 100 μg) induced a rise in plasma PRL which was neither dose-related nor antagonized by naloxone; morphine (5 and 10 μg) was active as PRL releaser and its effect was antagonized by naloxone. These results indicate that: 1) Leu5-enkephalin stimulates both GH and PRL release; 2) the release of GH by Leu5-enkephalin but likely not that of PRL involves specific opiate receptors; 3) morphine releases GH and PRL through specific opiate receptors.  相似文献   
42.
Summary From November 1973 to December 1974, 20 patients with advanced malignant melanoma were treated with BCG given by intralymphatic route at the Cancer Institute of Milan. The lyophilized Pasteur BCG was used. Patients were treated with a single dose ranging from 0.2–80 mg. Patients' performance status was never severely impaired.The most frequent side effects were fever, lymphangitis, and lymph node enlargement.Variations were observed in white cell count, ERS and immunoglobulins; in no case did we find evidence of liver toxicity or tumor growth enhancement. It is concluded that the intralymphatic route is a safe way of administrating BCG.  相似文献   
43.
44.
Nigericin is a monocarboxylic polyether molecule described as a mobile K+ ionophore unable to transport Li+ and Cs+ across natural or artificial membranes. This paper shows that the ion carrier molecule forms complexes of equivalent energy demands with Li+, Cs+, Na+, Rb+, and K+. This is in accordance with the similar values of the complex stability constants obtained from nigericin with the five alkali metal cations assayed. On the other hand, nigericinalkali metal cation binding isotherms show faster rates for Li+ and Cs+ than for Na+, K+, and Rb+, in conditions where the carboxylic proton does not dissociate. Furthermore, proton NMR spectra of nigericin-Li+ and nigericin-Cs+ complexes show wide broadenings, suggesting strong cation interaction with the ionophore; in contrast, the complexes with Na+, K+, and Rb+ show only clear-cut chemical shifts. These latter results support the view that nigericin forms highly stable complexes with Li+ and Cs+ and contribute to the explanation for the inability of this ionophore to transport the former cations in conditions where it catalyzes a fast transport of K+>Rb+>Na+.Part of the results of this paper were presented at the 14th International Congress of Biochemistry in Prague, Czechoslovakia.  相似文献   
45.
Summary Androgenic plants have been obtained via anther culture in four natural populations of Hordeum spontaneum. Microscopic observations revealed that androgenesis started with the formation of two vegetative-type nuclei derived from the mitotic division of the uninucleate microspores. In this species androgenesis was affected by the type and concentration of the sugars added to the culture medium: the highest response (17% of callusing anthers) was observed on media containing 80 g l–1 maltose. The highest production of androgenic plants (per 100 anthers, 5.9 green and 4.3 albino plants) was obtained from callus grown on these same media. About half of the green plants regenerated were haploid, while the others were diploid and set seed.Abbreviations IAA indolacetic acid - BAP 6-benzylaminopurine  相似文献   
46.
Shoot tips of M.4 apple clone were excised from actively growing one year-old stoolbed branches, and cultured in order to determine the optimal nutrient medium for each stage of their in vitro culture. The basal medium (BM) used was that described by Murashige and Skoog, supplemented with vitamins, glycine, myoinositol, sucrose, with or without agar, and different combinations of plant growth regulators. Best media for each stage were: BM+0.5 mg 1-1 indole-3yl-butyric acid (IBA)+0.5 mg 1-1 6-benzylaminopurine (BAP) for explant establishment (Stage I); BM+0.1 mg 1-1 IBA+1.0 mg 1-1 BAP for multiplication and internode enlargement (Stage II); and 2.0 mg 1-1 IBA+0.1 mg 1-1 BAP without agar for the rooting of the plantlets (Stage III).  相似文献   
47.
48.
BackgroundAntigen tests for diagnosis and disease monitoring in some types of neurocysticercosis (NCC) are useful but access to testing has been limited by availability of proprietary reagents and/or kits.Methods/Principal findingsThree previously identified IgM-secreting hybridomas whose IgM products demonstrated specificity to Taenia solium underwent variable heavy and light chain sequencing and isotype conversion to mouse IgG. Screening of these recombinantly expressed IgG anti-Ts hybridomas, identified one (TsG10) with the highest affinity to crude Taenia antigen. TsG10 was then used as a capture antibody in a sandwich antigen detection immunoassay in combination with either a high titer polyclonal anti-Ts antibody or with biotinylated TsG10 (termed TsG10*bt). Using serum, plasma, and CSF samples from patients with active NCC and those from NCC-uninfected patients, ROC curve analyses demonstrated that the TsG10-TsG10-*bt assay achieved a 98% sensitivity and 100% specificity in detecting samples known to be antigen positive and outperformed the polyclonal based assay (sensitivity of 93% with 100% specificity). By comparing levels of Ts antigen (Ag) in paired CSF (n = 10) or plasma/serum (n = 19) samples from well-characterized patients with extra-parenchymal NCC early in infection and at the time of definitive cure, all but 2 (1 from CSF and 1 from plasma) became undetectable. There was a high degree of correlation (r = 0.98) between the Ag levels detected by this new assay and levels found by a commercial assay. Pilot studies indicate that this antigen can be detected in the urine of patients with active NCC.Conclusions/SignificanceA newly developed recombinant monoclonal antibody-based Ts Ag detection immunoassay is extremely sensitive in the detection of extra-parenchymal NCC and can be used to monitor the success of treatment in the CSF, serum/plasma and urine. The ability to produce recombinant TsG10 at scale should enable use of this antigen detection immunoassay wherever NCC is endemic.Clinical Trial RegistrationClinicalTrials.gov Identifiers: NCT00001205 - & NCT00001645.  相似文献   
49.
50.
Occupancy as a measure of territory quality   总被引:7,自引:2,他引:7  
  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