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   9886篇
  免费   610篇
  国内免费   65篇
耳鼻咽喉   84篇
儿科学   266篇
妇产科学   141篇
基础医学   1373篇
口腔科学   222篇
临床医学   713篇
内科学   2676篇
皮肤病学   357篇
神经病学   766篇
特种医学   341篇
外科学   979篇
综合类   69篇
一般理论   1篇
预防医学   517篇
眼科学   194篇
药学   723篇
中国医学   66篇
肿瘤学   1073篇
  2023年   61篇
  2022年   112篇
  2021年   247篇
  2020年   157篇
  2019年   185篇
  2018年   243篇
  2017年   223篇
  2016年   248篇
  2015年   235篇
  2014年   379篇
  2013年   429篇
  2012年   584篇
  2011年   687篇
  2010年   406篇
  2009年   390篇
  2008年   541篇
  2007年   654篇
  2006年   579篇
  2005年   638篇
  2004年   609篇
  2003年   581篇
  2002年   528篇
  2001年   181篇
  2000年   130篇
  1999年   151篇
  1998年   104篇
  1997年   88篇
  1996年   77篇
  1995年   57篇
  1994年   38篇
  1993年   41篇
  1992年   85篇
  1991年   69篇
  1990年   85篇
  1989年   89篇
  1988年   66篇
  1987年   60篇
  1986年   45篇
  1985年   60篇
  1984年   47篇
  1983年   37篇
  1981年   22篇
  1980年   27篇
  1979年   30篇
  1978年   28篇
  1977年   21篇
  1975年   18篇
  1974年   29篇
  1973年   16篇
  1970年   21篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
22.
To determine the prognostic factors for patients with pathological T1 (pT1) carcinoma of the ampulla of Vater, 36 consecutive patients with carcinoma of the ampulla of Vater who underwent surgery were retrospectively analyzed in terms of clinicopathological features. The overall 5-year Kaplan-Meier survival in all patients was 50.2%, and the median survival of all patients was 64.0 months. Factors favorably influencing a long-term outcome were the absence of lymph node metastasis (P<0.0001), the absence of ulcer formation of the tumor (P=0.0062), and the absence of tumor invasion into the duodenum (P = 0.0025) and the pancreas (P=0.0098). In a multivariate analysis, lymph node metastasis was the only predictor of survival (P=0.0023). In the pT1 stage patients, 20% of the patients had lymph node metastasis, and their survival was statistically poor compared to the pT1 patients without lymph node metastasis (P=0.017). As for survival after the operation, there was no significant difference between pancreatoduodenectomy and pylorus-preserving pancreatoduodenectomy.  相似文献   
23.
US findings of 81 patients with breast cancer were analyzed respectively to evaluate the usefulness of US in the preoperative diagnosis of internal mammary mode metastases. The internal mammary area (I.M.A.) in which internal mammary nodes lie was shown as a hypoechoic stripe in a sagittal scan along the sternum and as a triangular or spindle-shaped hypoechoic area in a transverse scan in the intercostal space. The US features of each I.M.A. in the first three intercostal spaces were divided into three patterns: Pattern-A wad defined as widening of the ipsilateral side of the I.M.A. compared with the contralateral side; Pattern-C was defined as normal at both sides of the I.M.A. Pathological examination confirmed the node metastases in 85.7% of intercostal scans showing Pattern-A and in 35% of intercostal scans showing Pattern-B. Only one of 189 intercostal scans showing Pattern-C had nodal metastases. The overall accuracy was 88.1% in 243 intercostal scans and 90.1% in 81 patients. We conclude that US is useful in the detection of internal mammary node metastases in patients with breast cancer.  相似文献   
24.
N Uemura  K Ozawa  A Tojo  K Takahashi  A Okano  H Karasuyama  K Tani  S Asano 《Blood》1992,80(12):3198-3204
Since the ras family of proto-oncogenes is supposed to be involved in leukemogenesis by point-mutational activation, we studied the effect of the activated ras gene on the growth of a murine interleukin-3 (IL-3)-dependent cell line, FDC-P2. The human activated c-H-ras gene was transfected into FDC-P2 cells by electroporation using a high-level expression vector, BMGhph, which contains a partial DNA sequence from bovine papillomavirus (BPV) and a hygromycin B (hmB)-resistant gene as a selectable marker. The transformed FDC-P2 cells showed a high incidence of IL-3-independent growth and tumorigenicity in nude mice. These clones did not express or secrete IL-3, suggesting the acquisition of IL-3 independence by a nonautocrine mechanism. The high incidence of autonomous growth may be due to the use of the BMG vector, because (1) the activated ras gene in pBR322 vector (pHs-49) was not so efficient in the induction of IL-3 independence, (2) the c-H-ras genome copies per cell increased in number up to about 50 copies by using the BMG vector, and (3) cotransfection with the activated ras gene and the BPV gene in separate plasmids partly enhanced the incidence of autonomous growth without increasing the copy number of the ras gene compared with transfection with the activated ras gene alone. The present study supports the idea that the activation of ras gene is an important step in malignant transformation of hematopoietic cells and suggests that the BPV gene products may cooperate with ras gene activation probably by affecting the cellular genes that may be involved in multistep leukemogenesis. The BMG vector may be useful to test the transforming ability of oncogenes whose oncogenic potential is relatively low.  相似文献   
25.
26.
Perceptual dysfunction in hemiplegia and automobile driving.   总被引:1,自引:0,他引:1  
Sixteen post-stroke, hemiplegic patients, who requested that they be allowed to return to driving, were extensively evaluated by a physiatrist, psychologist, occupational therapist, and driver training specialist. After they completed a driver training program, the patients were divided into three groups based on their driving program success and follow-ups. Significant differences in the psychological test results were found between Group I (those who drove without any difficulty) and Groups II and III (those who drove limited distance or who failed driver training). Results suggest that patients with significant cognitive and perceptual problems who take training and limit their driving can be safe drivers when they return to driving.  相似文献   
27.
Flavobacterium meningosepticum IFO 12535, a menaquinone (MK) producer, was mutagenized to improve productivity. A mutant, which was resistant to 1-hydroxy-2-naphthoate (HNA), was found to produce MK more abundantly: 34 mg/liter of culture broth and 5.5 mg/g of dry cells. The mutant was less sensitive to inhibition by HNA on MK biosynthesis than the wild-type strain. MK was isolated from cells of the mutant and identified as MK-6 based on its physicochemical characteristics. Mutants, which were given each KCN resistance, aromatic amino acid auxotrophy and no carotenoid productivity, did not show further increase of productivity.  相似文献   
28.
The efficacy and safety of MTX in active RA were evaluated based on patient medical records. The study population consisted of 460 patients with active RA who had received no prior MTX therapy and started it at our hospital between August 1998 and December 2003 (80 men and 380 women with a mean age of 59.3 years). After 24 weeks of MTX therapy, 61.3% of patients showed a 20% improvement, and 30.4% achieved a 50% improvement according to the ACR criteria. The cumulative rate of patients who continued MTX therapy for 48 weeks was 0.567. During the observation period, 260 patients (56.5%) experienced 304 adverse reactions. 52 patients (11.3%) discontinued treatment because of adverse reactions, and 10 patients (2.2%) died. The adverse reactions that occurred in at least 1% of patients were: abnormal hepatic function (31.7%), infection (6.1%), gastrointestinal symptoms (5.0%), stomatitis (3.9%), hematological abnormalities (3.5%), fracture (3.5%), malignant tumor (2.6%), interstitial pneumonia (2.0%), cerebrovascular or cardiovascular disorder (2.0%), headache (1.7%), eruption (1.3%), and alopecia (1.1%). Adverse reactions were more common in the elderly and patients with advanced stage disease. This study reaffirms the therapeutic benefit of MTX, but suggests that careful monitoring is of great importance.  相似文献   
29.
Using two representative immunosuppressants, FK506 (FK) and cyclosporin A (CyA), of which the mechanism of pharmacological action is the same although there is a great difference in the pharmacological intensity, the distribution characteristics were studied in both in vivo and in vitro experiments using rat, dog, and human blood. Blood samples were fractionated by means of sedimentation in Ficoll-Paque®, and the drug contents in the diluted plasma fraction, erythrocyte fraction, and lymphocyte fraction were measured by an HPLC method. FK distributes to the lymphocyte fraction to a level about three times greater than that of CyA, while CyA distributes to the erythrocyte fraction to a level ten times that of FK. The distribution pattern of these fractions was independent of the drug concentration and species after correcting the drug concentration in each fraction with the blood drug concentration. The uptakes of FK and CyA in the isolated lymphocytes obtained from the rat spleen and human peripheral blood were also studied. The amount of FK taken up by the spleen lymphocytes is five times greater than that of CyA. In the case of the uptake study using human peripheral blood lymphocytes, the concentration of FK in the lymphocyte is 100-fold higher than that of CyA. This difference in the lymphocyte level between the two immunosuppressants is thought to be one of the reasons why FK is more potent than CyA, a difference of about 100-fold in the in vitro pharmacological study and about tenfold in the in vivo organ transplantation experiments.  相似文献   
30.
The blocking effects of complement-dependent sperm immobilizingantibodies in the sera of infertile women and monoclonal antispermantibodies against humans and mice on fertilization were investigated.The hemizona assay (HZA) and sperm penetration assay (SPA) wereused to study the inhibitory effects of sera from 22 infertilepatients positive for sperm immobilizing antibodies. Use ofthese tests allowed us to differentiate whether the antibodyblocked sperm—zona pellucida tight binding and/or spermpenetration into the ooplasm. The zona pellucida penetrationassay (ZPA) was also used to study the effects of four monoclonalantibodies (mAbs) on human sperm penetration into the zona pellucida.Seven mAbs against murine spermatozoa were tested for theirinhibitory effects on in-vitro fertilization (IVF) and HZA inmice. Of 22 patient sera with sperm immobilizing antibodies,21 (95.5%) inhibited HZA attachment and penetration, whereasthis did not occur in any of 13 patient sera without these antibodies.However, 19 of 22 (86.4%) patient sera with sperm immobilizingantibodies and eight of 13 (61.5%) patient sera without theseantibodies inhibited the SPA. Two (2C6, 1G12) of four mAbs againsthuman spermatozoa showed strong inhibitory effects in all theassays (HZA, ZPA and SPA). One mAb (3B10) did not inhibit HZAbut blocked ZPA and SPA. Another mAb (H6-3C4) seemed to haveno inhibitory effects on fertilization. Two (Vx 5 and Vx 8)of seven mAbs against murine spermatozoa inhibited IVF in micebut did not block mouse HZA. These findings suggest that antispermantibodies block fertilization at specific stages. Some of themmay inhibit sperm capacitation and thus prevent all processesof fertilization that follow. Some other antibodies may notaffect capacitation and sperm binding to zona pellucida butinhibit the acrosome reaction, followed by the blocking of spermpenetration through zona pellucida and ooplasm.  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