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   15142篇
  免费   718篇
  国内免费   70篇
耳鼻咽喉   104篇
儿科学   186篇
妇产科学   158篇
基础医学   1801篇
口腔科学   366篇
临床医学   962篇
内科学   3348篇
皮肤病学   1099篇
神经病学   1531篇
特种医学   667篇
外科学   2496篇
综合类   97篇
预防医学   397篇
眼科学   130篇
药学   1411篇
中国医学   36篇
肿瘤学   1141篇
  2022年   112篇
  2021年   227篇
  2020年   131篇
  2019年   164篇
  2018年   239篇
  2017年   187篇
  2016年   258篇
  2015年   261篇
  2014年   342篇
  2013年   373篇
  2012年   575篇
  2011年   581篇
  2010年   344篇
  2009年   302篇
  2008年   590篇
  2007年   625篇
  2006年   598篇
  2005年   593篇
  2004年   628篇
  2003年   631篇
  2002年   589篇
  2001年   586篇
  2000年   655篇
  1999年   611篇
  1998年   248篇
  1997年   163篇
  1996年   162篇
  1995年   143篇
  1994年   123篇
  1993年   106篇
  1992年   435篇
  1991年   385篇
  1990年   401篇
  1989年   429篇
  1988年   403篇
  1987年   368篇
  1986年   324篇
  1985年   290篇
  1984年   172篇
  1983年   154篇
  1982年   84篇
  1979年   164篇
  1978年   85篇
  1977年   86篇
  1976年   72篇
  1974年   71篇
  1973年   80篇
  1972年   84篇
  1970年   74篇
  1969年   69篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Of 514 patients with differentiated thyroid carcinoma treated between 1970 and 1987, 34 (6.6%) had distant metastases. Twelve patients died of their distant metastases; eight of these patients died within 5 years from the time of initial diagnosis. Death from cancer was most frequent in the seventh decade. The metastases were most often found in the lungs and bones. In the fatal group, pleural, brain, and pericardial metastases were noted. Local recurrences were found only in 24% of these 34 patients. Histologic types of primary thyroid tumors and metastatic tumors were reexamined and classified using our criteria, which were mainly based on the World Health Organization nomenclature and currently obtained pathologic observations of thyroid tumors. In 31 thyroid tumors, the surgical specimens were available for review. Twenty-four tumors were papillary and seven were follicular. Of the 24 papillary carcinomas, nine were follicular, eight were well-differentiated, and seven were trabecular. On the other hand, the seven follicular carcinomas consisted of four well-differentiated, two solid, and one oxyphilic. The majority of the thyroid tumors showed an extrathyroidal extension; however, two were intrathyroidal carcinomas and two were encapsulated carcinomas, larger than 5 cm in diameter. Distant metastases were confirmed morphologically in 18 patients (11 by surgical or biopsy material, five by autopsy, and two by cytology). The histologic types of metastatic tumors were consistent with those of primary thyroid tumors. Diagnostic 131I uptake was examined in 32 patients and absorption of diagnostic 131I in metastatic tumors was demonstrated in 21 patients. The 10-year survival rate of patients with 131I accumulating metastases (70%) was significantly better than that of patients with metastases lacking such uptake (40%). Immunoreactivity for thyroglobulin in metastatic tumors was correlated with the 131I absorption. This finding indicated that immunostaining of thyroglobulin in metastatic tumors might be useful in the prediction of the effectiveness of 131I therapy.  相似文献   
83.
84.
85.
Summary Cordycepin (3-deoxyadenosine) inhibited viral RNA synthesis in the replication of western equine encephalitis virus, thereby causing a reduction of virus production. The rate of inhibition of viral RNA synthesis was dependent on drug concentration and the period of treatment with the drug. These results suggest that the virus RNA synthesizing system is sensitive to the drug.With 3 Figures  相似文献   
86.
87.
Despite the huge number of colonized Gram-negative bacteria in the colon, the normal colon maintains its homeostasis without any excessive immune response. To investigate the potential mechanisms involved, human colonic lamina propria mononuclear cells (LPMCs) obtained from uninflamed mucosa were cultured with lipopolysaccharide (LPS) prepared from Bacteroides vulgatus (BV-LPS) or Bacteroides fragilis (BF-LPS), as representatives of indigenous flora, or pathogenic Salmonella minnesota (SM-LPS). Colonic LPMCs failed to produce inflammatory cytokines in response to any type of LPS. Colonic macrophages barely expressed mRNA for MD-2, an essential association molecule for LPS signaling via Toll-like receptor 4. Further, BV-LPS induced CD25 and Foxp3 expression in lymphocytes and CD4(+)CD25(+) cells expressed IL-10 mRNA. Thus, the low expression of functioning LPS receptor molecules and induction of IL-10-producing CD4(+)CD25(+) lymphocytes by indigenous LPS may play a central role in the maintenance of colonic immunological homeostasis.  相似文献   
88.
An implantable secondary battery is one of the key components in a total artificial heart system. Because a 2 year cycle life is required, the cycle life of the secondary battery as well as its charge and discharge properties are important parameters for selection of an appropriate battery. We carried out cycle life tests on four kinds of rechargeable batteries (a Ni-MH secondary battery, a Ni-Cd secondary battery, a Li-ion battery with a graphite anode, and a Li-ion battery with a nongraphitizable carbon electrode) to determine their suitability as implanted back-up batteries. Each of the batteries was charge/discharge cycled at 37 degrees C to 39 degrees C using a charge current of 1 C ampere, and they were each fully discharged under either pulsatile discharge loads, which mimicked pulsatile operation, or a nonpulsatile load equivalent to the average of the pulsatile loads. The two Li-ion batteries made by different manufacturers both met the minimum requirement of cycle life of more than 1,500 cycles, considering safety coefficient regardless of the discharge pattern. In addition, the temperature increase of these Li-ion batteries (3 degrees C) was lower than that of Ni-Cd and Ni-MH batteries (15-25 degrees C). Out of these four batteries, the two Li-ion batteries are the most suitable for use in a totally implantable artificial heart system.  相似文献   
89.
Using a flexible piezoelectric film, the authors developed a simple system to determine noninvasively the heart rate of chicken embryos and hatchlings. The film was piezoelectric polyvinylidene fluoride (PVDF), which is sensitive enough to detect cardiogenic ballistic movements of the egg (ballistocardiogram (BCG)) and precordial movements of the hatchling attributable to cardiac contractions (apexcardiogram (ACG)). The BCG could be detected, during the second half of incubation, by placing the egg on the PVDF film on a soft substrate. The detected signal was found to be a measure of movement velocity. The ACG could be measured when the hatchling's chest wall made contact with the PVDF film installed in a box in which the hatchling was confined. The heart rate was counted from the lag time of autocorrelation calculated for a certain time segment (e.g. 2s) of the BCG and ACG recordings.  相似文献   
90.
We found M-proteins with two peaks by agarose electrophoresis in the serum of a myeloma patient. The M-proteins were identified as both IgG 1-kappa type, and classified as IgG-F (fast mobility) and IgG-S (slow mobility). 1) The possibility that the two M-proteins were derived from the post translational differences of sugar moieties of the same IgG molecule was unlikely, because no migration changes were observed in IgG-F and IgG-S after the treatment with 4 different sugar enzymes. 2) Fab fractions of IgG-F and IgG-S were analyzed. After papain or pepsin digestion, western blotting with anti-Fab antiserum revealed that the Fab fraction of IgG-F and IgG-S had identical mobility by agarose electrophoresis. However the Fc fractions of IgG-F and IgG-S analyzed by the same procedures with anti-Fe antiserum, were different. 3) Anti-idiotype antiserum prepared in rabbits against IgG-S, or -F, and absorbed by normal IgG and normal human serum showed a fused precipitin line with IgG-F and IgG-S. These findings suggest that two M-proteins with both IgG 1 and kappa type, have the same VH and VL regions but have different constant regions of heavy chain. Since one copy of IgG 1 constant gene is found in each human haploid gene. It is speculated that the switching of the rearranged VDJ gene to constant region gene occurred not only between cis chromosome but also between trans chromosome.  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