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   9707篇
  免费   552篇
  国内免费   79篇
耳鼻咽喉   94篇
儿科学   177篇
妇产科学   92篇
基础医学   1220篇
口腔科学   211篇
临床医学   634篇
内科学   2650篇
皮肤病学   247篇
神经病学   570篇
特种医学   376篇
外科学   1781篇
综合类   42篇
预防医学   193篇
眼科学   193篇
药学   606篇
中国医学   21篇
肿瘤学   1231篇
  2024年   11篇
  2023年   144篇
  2022年   268篇
  2021年   419篇
  2020年   222篇
  2019年   316篇
  2018年   374篇
  2017年   273篇
  2016年   298篇
  2015年   283篇
  2014年   381篇
  2013年   422篇
  2012年   716篇
  2011年   665篇
  2010年   394篇
  2009年   327篇
  2008年   546篇
  2007年   641篇
  2006年   580篇
  2005年   589篇
  2004年   565篇
  2003年   501篇
  2002年   492篇
  2001年   78篇
  2000年   74篇
  1999年   97篇
  1998年   104篇
  1997年   79篇
  1996年   76篇
  1995年   53篇
  1994年   50篇
  1993年   44篇
  1992年   36篇
  1991年   39篇
  1990年   25篇
  1989年   19篇
  1988年   24篇
  1987年   19篇
  1986年   9篇
  1985年   14篇
  1984年   8篇
  1983年   10篇
  1982年   19篇
  1981年   6篇
  1980年   8篇
  1979年   5篇
  1978年   4篇
  1977年   6篇
  1976年   2篇
  1974年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
We constructed a question and answer system for direct delivery of E-mail queries from the general public to the proper hospital representative and with which the system administrator can monitor E-mail replies. The system consists of two sub-systems; one is an E-mail questionnaire sub-system that automatically delivers E-mail queries to the proper person and an E-mail reply monitor sub-system with which the system administrator can monitor the E-mail replies. The monitor system compares the origin address of the E-mail reply and the destination address on a questionnaire filled out at the time the query is made. In a test of the system, 56 queries were received in 31 days, with 37 replied to. The interval from receipt of an E-mail query to reply was calculated. Nineteen replies were submitted within 2 days.  相似文献   
102.
A 49-yr-old Japanese woman underwent upper gastrointestinal endoscopy because of nonspecific dyspepsia. Endoscopy revealed a flat elevated lesion about 15 mm in diameter adjacent to the duodenal papilla, the surface of which was uneven and covered with whitish granules. Based on the results of histological examination with immunohistochemistry (positive for CD10, CD20, CD79a, and bcl-2 protein, negative for CD5 and cyclin D1), a diagnosis of grade 1/3 follicular lymphoma was established. Systemic staging examinations suggested the lymphoma was restricted to the mucosa and superficial portion of the submucosa in the duodenal wall. The patient was treated with a combination of CHOP chemotherapy (cyclophosphamide, doxorubicin, vincristine, and prednisolone) and monoclonal anti-CD20 antibody (rituximab), in addition to radiotherapy. After six courses of this combination chemotherapy, complete regression of the lymphoma was observed. Although reports of small duodenal lymphoma (<20 mm or localized to the mucosa or submucosa) are extremely rare, the features of this case are characteristic of small duodenal lymphoma in terms of evolution around the ampulla of Vater, low-grade follicular type, occurrence in a women, occurrence in the fourth decade of life, and favorable outcome, and this type of tumor may need to be distinguished by pathogenesis and clinical behavior from various other gastrointestinal lymphomas.  相似文献   
103.
104.
105.
Tumor blood vessels play an important role in tumor progression and metastasis. We previously reported that tumor endothelial cells (TEC) exhibit several altered phenotypes compared with normal endothelial cells (NEC). For example, TEC have chromosomal abnormalities and are resistant to several anticancer drugs. Furthermore, TEC contain stem cell‐like populations with high aldehyde dehydrogenase (ALDH) activity (ALDHhigh TEC). ALDHhigh TEC have proangiogenic properties compared with ALDHlow TEC. However, the association between ALDHhigh TEC and drug resistance remains unclear. In the present study, we found that ALDH mRNA expression and activity were higher in both human and mouse TEC than in NEC. Human NEC:human microvascular endothelial cells (HMVEC) were treated with tumor‐conditioned medium (tumor CM). The ALDHhigh population increased along with upregulation of stem‐related genes such as multidrug resistance 1, CD90, ALP, and Oct‐4. Tumor CM also induced sphere‐forming ability in HMVEC. Platelet‐derived growth factor (PDGF)‐A in tumor CM was shown to induce ALDH expression in HMVEC. Finally, ALDHhigh TEC were resistant to fluorouracil (5‐FU) in vitro and in vivo. ALDHhigh TEC showed a higher grade of aneuploidy compared with that in ALDHlow TEC. These results suggested that tumor‐secreting factor increases ALDHhigh TEC populations that are resistant to 5‐FU. Therefore, ALDHhigh TEC in tumor blood vessels might be an important target to overcome or prevent drug resistance.  相似文献   
106.
107.
We report herein the case of a 70-year-old man who was found to have a gastrointestinal stromal tumor (GIST) in the stomach following sigmoid colon resection. Preoperative gastroscopic and barium examinations revealed a submucosal tumor, measuring 10cm, on the upper part of the stomach. Using computed tomography (CT) images (i.e., computed tomographic volumetry) the doubling time of this tumor was calculated, accurately, as 3.3 months, which suggested a high growth rate and malignancy. A laparotomy and partial gastric resection were performed. Histologically, the tumor consisted of spindle-shaped cells with oval nuclei. In immunohistochemical studies, the tumor cells were positive with respect to c-kit, CD34, and vimentin, but negative with respect to smooth muscle actin and S-100 protein. There were 15–16 mitoses per 50 high-power fields (HPFs), and the Ki-67 antigen (MIB-1) index was 25.5% in the most active areas, which also indicated malignancy. The final pathological diagnosis of this tumor was malignant GIST. The patient was found to have hepatic metastasis 27 months after the surgery, and he subsequently received a hepatic subsegmentectomy. To our knowledge, there are very few reports concerning the growth rate of GISTs. Computed tomographic volumetry is useful for the follow-up of small or irregularly shaped gastric submucosal tumors, and for making decisions regarding surgical intervention.  相似文献   
108.
The anti-tumor and anti-metastatic effects of TNP-470, an angiogenesis inhibitor, and mitomycin C (MMC), a representative anti-neoplastic agent, were investigated using our established liver-metastasizing gastric carcinoma line, AZ-H5c. AZ-H5c was injected into the spleen of nude mice which had been randomly divided into 4 groups; a control group given saline solution, a group receiving 15 mg/kg TNP-470, a group receiving 30 mg/kg TNP-470 and a group receiving 2 mg/kg MMC. TNP-470 was given s.c. on alternate days for 5 weeks from day 10 after intrasplenic injection, and MMC was administered intraperitoneally (i.p.) once a week from day 10 after intrasplenic injection. In the control group, liver metastasis developed in 13 of 16 mice (81%). Liver metastasis developed in 6 of 11 mice (55%) receiving MMC. In contrast, liver metastasis developed in 4 of 8 mice (50%) receiving 15 mg/Kg TNP-470, and in 0 of 14 mice (0%) receiving 30 mg/kg TNP-470. However, TNP-470 had no effect on the tumor growth. These results indicate that the angiogenesis inhibitor TNP-470 has a strong inhibitory activity against in vivo liver metastasis of human gastric carcinoma.  相似文献   
109.
Strong adhesion between recyclable thermoplastic (TP) polymer and carbon fiber (CF) has always been highly sought after. Therefore, for an interlayered CF reinforced TP polypropylene (CFRTPP) composite composed of 3 sized CF plies, alternating between 4 PP sheets, designated [PP]4[CF]3, a process of activating CF plies directly on both sides with homogeneous low energy electron beam irradiation (EBI) under N2 gas, prior to lamination assembly and hot press of 4.0 MPa at 493 K for 3 min was carried out. Experimental results showed EBI dose of 43.2, 129, or 216 kGy significantly raised Charpy impact values, auc at all fracture probabilities, Pf. The 129 kGy dose appeared to be at or near optimum increasing auc 103%, 83%, and 65% at low-, median-, and high-Pf = 0.07, 0.50, and 0.93; while raising statistically lowest impact value, as at Pf = 0 calculated by 3-dimensional Weibull equation about 110%, indicating increased safety and reliability. It is assumed dangling bonds generated by the EBI rapidly form covalent bonds CF:C:O:C:PP and CF:C:C:PP at the interface, along with cross-linking in the PP near the CF. This is by charge transfer from CF to PP.  相似文献   
110.
So far, poly(L-lactic acid), PLLA nanosheets proved to be promising for wound healing. Such biodegradable materials are easy to prepare, bio-friendly, cost-effective, simple to apply and were shown to protect burn wounds and facilitate their healing. At the same time, certain metal ions are known to be essential for wound healing, which is why this study was motivated by the idea of incorporating PLLA nanosheets with Zn2+ ion containing nanoparticles. Upon being applied on wound, such polymer nanosheets should release Zn2+ ions, which is expected to improve wound healing. The work thus focused on preparing PLLA nanosheets embedded with several kinds of Zn-containing nanoparticles, their characterization and ion-release behavior. ZnCl2 and ZnO nanoparticles were chosen because of their different solubility in water, with the intention to see the dynamics of their Zn2+ ion release in liquid medium with pH around 7.4. Interestingly, the prepared PLLA nanosheets demonstrated quit similar ion release rates, reaching the maximum concentration after about 10 h. This finding implies that such polymer materials can be promising as they are expected to release ions within several hours after their application on skin.  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