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   141495篇
  免费   9332篇
  国内免费   3097篇
耳鼻咽喉   1730篇
儿科学   3326篇
妇产科学   4358篇
基础医学   21116篇
口腔科学   3928篇
临床医学   12383篇
内科学   25129篇
皮肤病学   2639篇
神经病学   9514篇
特种医学   4995篇
外国民族医学   23篇
外科学   18787篇
综合类   8706篇
现状与发展   5篇
一般理论   38篇
预防医学   10065篇
眼科学   3612篇
药学   12657篇
  34篇
中国医学   2215篇
肿瘤学   8664篇
  2022年   1554篇
  2021年   2296篇
  2020年   1557篇
  2019年   1907篇
  2018年   2503篇
  2017年   1893篇
  2016年   1908篇
  2015年   2437篇
  2014年   3251篇
  2013年   3548篇
  2012年   5186篇
  2011年   5516篇
  2010年   3345篇
  2009年   2938篇
  2008年   4475篇
  2007年   4692篇
  2006年   4751篇
  2005年   4210篇
  2004年   3644篇
  2003年   3480篇
  2002年   3211篇
  2001年   7167篇
  2000年   7466篇
  1999年   6232篇
  1998年   2178篇
  1997年   1741篇
  1996年   1199篇
  1995年   1111篇
  1992年   3912篇
  1991年   3939篇
  1990年   3666篇
  1989年   3646篇
  1988年   3526篇
  1987年   3362篇
  1986年   3164篇
  1985年   3034篇
  1984年   2079篇
  1983年   1819篇
  1982年   1006篇
  1979年   1939篇
  1978年   1198篇
  1977年   1000篇
  1975年   1211篇
  1974年   1393篇
  1973年   1440篇
  1972年   1377篇
  1971年   1269篇
  1970年   1160篇
  1969年   1152篇
  1968年   1047篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A new haplogroup pattern displayed in Fujian Han in China   总被引:1,自引:0,他引:1  
Yu M  Zhang Y  Xue Y  Chen F  Wang Q  Huang X  Wang B  Yu Y  Liu A  Ma L  Shi R  Lu F  Shi Z  Zhang Y  Cheng W  Ai Q  Xu F  Huang C  Chen B  Yang H  Kang X  Sun Y  Zhang G  Li P  Fu S 《Journal of human genetics》2002,47(2):95-98
Human Y-chromosomal binary polymorphisms have been considered to preserve the paternal genetic legacy and provide evidence on human evolution and the genetic relationships among and demographic history of different populations. To reveal the genetic origin and immigration of the Fujian Han, 13 binary markers on the Y chromosome were used to screen Fujian Han by allele-specific polymerase chain reaction. The results indicated that the M9G marker was highly prevalent (96.20%), suggesting a significant genetic drift. In addition, M122C frequency was only 22.78%, and M45A and M103T were default. The distinctive haplogroup frequencies (H1, H5, and H6/7/8) imply that the haplogroup pattern is a relatively ancestral and interim type. Received: October 13, 2001 / Accepted: December 3, 2001  相似文献   
992.
Primary culture of prostatic adenocarcinoma is obtained from surgical material after radical prostatectomy. Typing of the obtained culture with antibodies to vimentin and cytokeratins has shown that the proportion of basic cell components--stromal and epithelial--in vitro correlates with such in the initial tumor tissue. In cultivation in different media active migration and proliferation of all cell types in the presence of embryonal serum and suppression of the stromal component in the medium where the serum was replaced for bovine hypophysis extract were observed. A comparative immunohistochemical analysis registered a release into culture of alpha SMA-positive myofibroblasts and active expression of TGF beta-1 in the medium containing serum. Design of dynamic mixed cell systems may serve a convenient model for investigation of stromal-epithelial interactions and their changes in cancer progression.  相似文献   
993.
The present study documents the characteristics of innervation of the rhinarium or hairless rat snout skin by light and electron microscopy. The outer glabrous surface is covered with a stratified squamous epithelium that forms both rete pegs and rete ridges, the latter on the inferior border near the philtrum. The glabrous skin contains numerous presumptive epidermal and dermal free nerve endings (FNE's), Merkel terminals at the base of the rete ridges and pegs, and simple, nonencapsulated corpuscles. A second region of dense innervation, found on an elevation of the inner wall of the vestibule, contains similar components of innervation, with the exception that no Merkel terminals were identified. Since no Merkel terminals were present in this area of the vestibule, intraepidermal as well as dermal FNE's could be identified with certainty. This skin is covered by a thin squamous epithelium overlying dense connective tissue. The simple corpuscles are similar to those in the rhinarium, as well as resembling those described in other species. FNE's were frequently observed intimately associated with simple corpuscles. Several examples of large FNE's with two to three layers of cytoplasmic lamellae were found, suggestive of transitional forms between FNE's and simple corpuscles. Thus, the pattern of sensory innervation in the glabrous rat snout skin is similar to that found in other furred species described to date, but in addition, the sensory innervation of ridged skin in the rat also resembles that of epidermis organized into rete pegs. This dense sensory innervation may be correlated with whisking behavior of the predominantly nocturnal rat.  相似文献   
994.
Gm allotypes in blacks with systemic lupus erythematosus   总被引:3,自引:0,他引:3  
Serum samples were collected from 328 healthy American Blacks and from 61 American Blacks with systemic lupus erythematosus (SLE). Sera were typed for the Gm1,2,3,5,6,13,17, and 21 allotypes as well as for the Km(1) allotype. The frequency of Gm phenotype 1,17;5,6,13 was significantly increased in the SLE patients (p = 0.0001, RR = 3.19, EF = 0.29). Our data suggest the existence of at least two immunoglobulin allotype associated genes that somehow interact to increase susceptibility to SLE in Blacks. To our knowledge, this is the first report of an association of Gm and SLE in Blacks.  相似文献   
995.
The most important aspect of diminished ovarian reserve is the associated decline in reproductive potential. Assessment of ovarian reserve is mainly based on measurement of early follicular phase follicle stimulating hormone (FSH) concentration. The objective of this study was to report the identification of a group of 12 infertile women initially diagnosed as having unexplained or anovulatory infertility, who had a normal baseline hormonal profile and did not respond to repeated ovarian stimulation with gonadotrophins. All developed ovarian failure within a relatively short time span. Non-response to ovarian stimulation was defined by failure to achieve development of follicles >12 mm and failure to raise oestradiol concentration >350 pmol/l in two successive cycles of human menopausal gonadotrophin (HMG) doses of up to five ampoules per day for 5-8 days. Within a mean of 9 months following the failed attempts of ovarian stimulation the mean day 3 FSH concentrations rose from 5.4 +/- 2.7 IU/l to 53.5 +/- 19.7 IU/l. In these patients, day 3 FSH concentration failed to indicate the low ovarian reserve manifested only by lack of clinical response to treatment with gonadotrophins which was the first sign of impending ovarian failure. We conclude that women with normal early follicular phase serum FSH concentrations who do not respond to ovarian stimulation by HMG are at risk of developing ovarian failure within several months.   相似文献   
996.
Splenic T cells were primed, after removal of alloreactive cells, to beef insulin on allogeneic antigen-presenting cells (APC). The fine specificity of in vitro secondary response was tested in combinations H-2b (responder) T cell-H-2k (nonresponder) APC, and vice versa, using separated chains of beef and pork insulin. The response in both combinations exhibited identical specificity patterns demonstrating that both responder and nonresponder APC could present the same array of insulin epitopes to allogeneic T cells. The determinants presented to allogeneic T cells include the A-chain loop epitope and the B-chain determinant(s) that were found to be immunogenic for H-2b and H-2d T cells, respectively, in the context of syngeneic major histocompatibility complex (HC) molecules. In addition, minor determinants were detected in the A chain outside the loop that are not immunogenic in syngeneic T cell-APC combinations. Inhibition of T cell proliferation with monoclonal antibodies has shown that class II MHC molecules of the nonresponder (Ak alpha Ak beta, Ek alpha Ek beta) as well as those of the responder APC (Ab alpha Ab beta) are equally capable of presenting virtually all insulin epitopes recognizable by T cells. The data, therefore, demonstrate that the selective recognition of different insulin epitopes observed in syngeneic or semisyngeneic T cell-APC combinations does not result from determinant selection at the level of APC.  相似文献   
997.
G Z Hastings  D S Burt    D R Stanworth 《Immunology》1988,65(1):149-151
A mouse monoclonal antibody (mAb) has been produced by conventional cell fusion methods against a synthetic peptide, p123, representative of a portion of the CH4 domain of rat immunoglobulin E (IgE). This monoclonal antibody was reactive with both peptide and purified rat IgE (p.rat IgE) by indirect enzyme immunosorbent assay (ELISA), and its binding to p.rat IgE was found to be inhibitable by pre-incubation with rat ascitic fluid containing the immunocytoma 162 (IR162) IgE. Heating of the immunocytoma IgE in solution at 56 degrees for 1 hr resulted in its enhanced binding of the mAb. The effect of this treatment was investigated further using p.rat IgE heated at 56 degrees for various time intervals between 0 and 60 min. The mAb showed enhanced binding to IgE heated for as little as 10 min, a similar level of binding being shown by samples heated for 30 and 60 min. The degree of aggregation of the IgE molecules brought about by the heat treatments was measured by differential UV absorption. This revealed a decrease in the proportion of monomeric IgE with an accompanying increase in the percentage of dimer and larger aggregates with increased time of heating at 56 degrees. These absorption data, together with the ELISA inhibition data, suggest that, rather than inducing changes mediated by aggregation of the IgE molecules in solution, heating at 56 degrees causes subtle alterations in the conformation of individual IgE molecules at specific sites within their CH4 domains, one of which is detected by this mAb.  相似文献   
998.
999.
Initial reaction-velocity versus substrate-concentration curves for serotonin oxidation catalyzed by monoamine oxidase (MAO) from fragments of rat liver or bovine brain mitochondrial membranes have a complex, nonhyperbolic shape; this is regarded as a kinetic manifestation of substrate cooperativeness for membrane-bound MAO. The possibility of interaction between different types of MAO based on conformational changes in the membrane itself is discussed.Scientific-Research Institute for Biological Trials of Chemical Compounds, Ministry of the Medical Industry of the USSR. Institute of Biological Medical Chemistry, Academy of Medical Sciences of the USSR. All-Union Vitamin Scientific-Research Institute, Ministry of the Medical Industry of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR V. N. Orekhovich.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 83, No. 3, pp. 288–289, March, 1977.  相似文献   
1000.
From the analysis of the fatty acid spectrum of the individual lipid fractions of the cerebral white matter in cyanide induced encephalopathy would appear that essentially the phosphatidyl ethanolamine and plasmalogen fractions showed appreciable deviations from the control spectra. The observed changes in the cholesteryl ester composition did not correlate with the macrophage reaction, which is known to appear as late as 14 days after HCN intoxication when morphological signs of demyelination become apparent. Neither was there a correlation between the alterations of the phosphatide fatty acid composition and that of cholesteryl esters. It thus would appear that esterification of cholesterol in the myelin of rats occurring during early stages following cyanide intoxication constitutes one of the primary factors injuring the myelin sheath. The same conclusion seems to be applicable to the changes in fatty acid composition of the white matter phospholipids.  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