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   7330篇
  免费   372篇
  国内免费   34篇
耳鼻咽喉   64篇
儿科学   283篇
妇产科学   163篇
基础医学   815篇
口腔科学   69篇
临床医学   756篇
内科学   1631篇
皮肤病学   138篇
神经病学   764篇
特种医学   215篇
外科学   944篇
综合类   31篇
一般理论   1篇
预防医学   702篇
眼科学   41篇
药学   489篇
中国医学   32篇
肿瘤学   598篇
  2024年   10篇
  2023年   64篇
  2022年   106篇
  2021年   193篇
  2020年   120篇
  2019年   172篇
  2018年   199篇
  2017年   160篇
  2016年   201篇
  2015年   181篇
  2014年   271篇
  2013年   352篇
  2012年   489篇
  2011年   559篇
  2010年   263篇
  2009年   248篇
  2008年   440篇
  2007年   475篇
  2006年   447篇
  2005年   438篇
  2004年   409篇
  2003年   377篇
  2002年   365篇
  2001年   140篇
  2000年   152篇
  1999年   119篇
  1998年   57篇
  1997年   43篇
  1996年   30篇
  1995年   24篇
  1994年   32篇
  1993年   31篇
  1992年   60篇
  1991年   54篇
  1990年   49篇
  1989年   38篇
  1988年   46篇
  1987年   40篇
  1986年   34篇
  1985年   43篇
  1984年   30篇
  1983年   19篇
  1982年   11篇
  1981年   14篇
  1980年   12篇
  1979年   19篇
  1975年   11篇
  1972年   10篇
  1969年   11篇
  1967年   11篇
排序方式: 共有7736条查询结果,搜索用时 15 毫秒
21.
OKT3-, OKT4- and OKT8-positive cells were estimated in 303 children with recurrent respiratory infections. The patients (selected by a score method) had experienced 13 or more infections a year. Modifications in T-cell subsets were observed in 154 patients (50.8%). Decreased OKT3- and OKT4-positive cells were present in 80 children (26.4%), while 74 patients (24.4%) showed normal values of OKT3-positive cells but decreased OKT4- and increased OKT8-positive cells. An attempt at treatment with thymostimulin was undertaken in a group of randomly chosen children with modifications in T-cell subsets. The use of thymostimulin induced the treated children more readily than the untreated ones to show improvement in both the score for respiratory infections and the distribution of T-cell subsets.  相似文献   
22.
23.
Rats were trained on an inhibitory avoidance task to study the effects of post-training administration of tetrodotoxin (TTX, which temporarily inactivates neural activity) on memory consolidation. During training, independent groups of rats received either a mild foot shock (0.8 mA) or a stronger (1.0 mA) foot shock. TTX was administered bilaterally into the dorsal hippocampus immediately after training, and memory of the task was measured 48 h later. We corroborated the typical amnesic effect of intrahippocampal infusions of TTX in those rats trained with the mild-intensity foot shock. More importantly, with the stronger foot shock, the same treatment was ineffective in producing amnesia. These results suggest that, after an enhanced learning experience, other brain regions are also activated, which may compensate for the amnesic effect of TTX infusions into the hippocampus.Due to an error in the citation line, this revised PDF (published in December 2003) deviates from the printed version, and is the correct and authoritative version of the paper.  相似文献   
24.
25.
E-selectin, an adhesion molecule of the selectin family, is involved in leukocyte adhesion to the endothelium and in the cellular immunological reactions. Expression of this molecule, in fact, is physiologically absent, but it becomes evident on sinusoidal lining cells during inflammatory liver disease. The aim of this study was to evaluate the behavior of E-selectin in chronic hepatitis C (CH-C) patients with persistently normal transaminase in comparison to patients with CH-C and elevated transaminase, and its changes during alpha-interferon therapy. Immunohistochemical localization of E-selectin was also performed on liver tissue specimens of both groups. Fifty-eight subjects were divided into 3 groups: group A included 18 patients with CH-C and persistently normal transaminase; group B 20 patients with CH-C and persistently elevated transaminase levels and group C included 20 healthy subjects, representing the control group. The first two groups were treated with r-IFN at a dose of 6 MU 3 times a week for 3 months and followed-up with 3 MU 3 times a week for another 3 months. Serum baseline values of E-selectin in groups A and B were significantly higher than those in group C (P < 0.04), but there was no difference between groups A and B. Furthermore, there was a trend toward higher E-selectin values as histological severity increased (r = 0.69; P < 0.0001). Post-treatment E-selectin serum values showed a moderate decrease in both groups, but only among responder patients; while E-selectin levels were unchanged in non responders. Immunohistochemical localization showed no staining for E-selectin in normal liver specimens, while there was a quite similar staining for E-selectin in the two groups of patients. In conclusion, this study shows that serum E-selectin levels in patients with CH-C and persistently normal transaminase are higher than in controls and they are associated with severity of liver disease. Liver of these patients express E-selectin molecules, suggesting an activation of the immune system almost identical to that of patients with CH-C and elevated transaminase. In both groups only responder patients showed a moderate decrease below baseline serum values.  相似文献   
26.
27.
A questionnaire-based retrospective clinical and immunological survey was conducted in 73 males with a definite diagnosis of X-linked agammaglobulinemia based on BTK sequence analysis. Forty-four were sporadic and 29 familial cases. At December 2000, the patients' ages ranged from 2 to 33 years; mean age at diagnosis and mean duration of follow-up were 3.5 and 10 years respectively. After the mid-1980s all but 2 were on intravenous immunoglobulin (IVIG) substitution therapy, with residual IgG >500 mg/dl in 94% of the patients at the time of enrollment. Respiratory infections were the most frequent manifestation both prior to diagnosis and over follow-up. Chronic lung disease (CLD) was present in 24 patients, in 15 already at diagnosis and in 9 more by 2000. The cumulative risk to present at diagnosis with CLD increased from 0.17 to 0.40 and 0.78 when the diagnosis was made at the ages of 5, 10, and 15 years respectively. For the 9 patients who developed CLD during follow-up, the duration of follow-up, rather than age at diagnosis; previous administration of intramuscular immunoglobulin; and residual IgG levels had a significant effect on the development of CLD. Chronic sinusitis was present in 35 patients (48%), in 15 already at diagnosis and in 20 by 2000. Sistemic infections such as sepsis and meningitis/meningoencephalitis decreased over follow-up, probably due to optimal protection provided by high circulating IgG levels reached with IVIG.  相似文献   
28.
Thirty-six cases of enterococcal septicemia in patients with hematological malignancies were reviewed retrospectively and categorized according to their clinical significance using strict previously described definitions. Overall, most of the infected patients were males (77 %), had acute leukemia (64 %), had recently received cytotoxic drug therapy (86 %), were granulocytopenic at the onset of septicemia (77 %), and acquired the infection during hospitalization (77 %). The source of septicemia was unknown in 18 (50 %) patients, intestinal in 15 (42 %) and intravascular in three (8 %). Mortality was 19 % among 21 inpatients who had clinically significant septicemia and 30 % among patients with septicemia of uncertain clinical significance. The fatal outcome could be definitively attributed to enterococcal septicemia in only one of the nine inpatients who died. Clinically significant septicemia appeared somewhat more frequently to be polymicrobial (p=0.06), whereas septicemia of unknown significance presented more frequently as breakthrough septicemia (p=0.013). Unless associated with intravascular infection, enterococcal septicemia in patients with hematological malignancies seems to represent a marker of cytotoxic drug damage of the intestinal mucosa rather than a truly invasive infection.  相似文献   
29.
Antibodies were raised against a synthetic dodecameric peptide KGAGQVVAGPWK (K12K), encompassing sequences thought to be important for the function of the cysteine proteinase inhibitors of the cystatin superfamily. These antibodies specifically recognized molecules of family 3, i.e., kininogens, in the serum of seven mammalian species tested in this study. The only notable exception was that of rat thiostatin (T kininogen) which is structurally related to the kininogen family. The antibodies also discriminated between family 2 (cystatins) and family 3 (kininogens) of the cystatin superfamily, since neither chicken cystatin nor human and rat cystatins C and S, which all belong to family 2 were recognized. The cystatin-like inhibitory domains resulting from fragmentation of human low molecular weight kininogen by bovine trypsin, were still recognized by antibodies, indicating that discrimination does not require two neighbouring inhibitory sites on the kininogen heavy chain. The antibodies blocked the capacity of kininogens to inhibit papain, suggesting that they recognize a conformational epitope at or near the kininogen inhibitory sites. The inhibitory properties of family 2 cystatins remained unchanged, confirming that members of this family do not interact with anti K12K antibodies. These antibodies are thus a new tool able to discriminate functionally and structurally between the members of the cystatin superfamily.  相似文献   
30.
Maternal and Child Health Journal - To measure the association between dental and medical insurance with the receipt of dental cleaning during pregnancy. We analyzed Pregnancy Risk Assessment...  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