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   9389篇
  免费   516篇
  国内免费   64篇
耳鼻咽喉   126篇
儿科学   267篇
妇产科学   247篇
基础医学   1373篇
口腔科学   200篇
临床医学   814篇
内科学   2132篇
皮肤病学   344篇
神经病学   1002篇
特种医学   469篇
外国民族医学   1篇
外科学   1013篇
综合类   45篇
一般理论   4篇
预防医学   470篇
眼科学   184篇
药学   594篇
中国医学   41篇
肿瘤学   643篇
  2023年   86篇
  2022年   153篇
  2021年   252篇
  2020年   147篇
  2019年   203篇
  2018年   260篇
  2017年   194篇
  2016年   211篇
  2015年   246篇
  2014年   306篇
  2013年   374篇
  2012年   595篇
  2011年   617篇
  2010年   374篇
  2009年   355篇
  2008年   566篇
  2007年   581篇
  2006年   611篇
  2005年   547篇
  2004年   558篇
  2003年   541篇
  2002年   456篇
  2001年   137篇
  2000年   128篇
  1999年   124篇
  1998年   105篇
  1997年   86篇
  1996年   67篇
  1995年   54篇
  1994年   46篇
  1993年   45篇
  1992年   66篇
  1991年   54篇
  1990年   67篇
  1989年   83篇
  1988年   68篇
  1987年   57篇
  1986年   51篇
  1985年   43篇
  1984年   41篇
  1983年   45篇
  1982年   32篇
  1981年   22篇
  1980年   17篇
  1979年   33篇
  1978年   21篇
  1977年   21篇
  1974年   24篇
  1970年   21篇
  1967年   14篇
排序方式: 共有9969条查询结果,搜索用时 15 毫秒
1.
Introduction: Collaborative interactions between several diverse biological processes govern the onset and progression of breast cancer. These processes include alterations in cellular metabolism, anti-tumor immune responses, DNA damage repair, proliferation, anti-apoptotic signals, autophagy, epithelial-mesenchymal transition, components of the non-coding genome or onco-mIRs, cancer stem cells and cellular invasiveness. The last two decades have revealed that each of these processes are also directly regulated by a component of the cell cycle apparatus, cyclin D1.

Area covered: The current review is provided to update recent developments in the clinical application of cyclin/CDK inhibitors to breast cancer with a focus on the anti-tumor immune response.

Expert opinion: The cyclin D1 gene encodes the regulatory subunit of a proline-directed serine-threonine kinase that phosphorylates several substrates. CDKs possess phosphorylation site selectivity, with the phosphate-acceptor residue preceding a proline. Several important proteins are substrates including all three retinoblastoma proteins, NRF1, GCN5, and FOXM1. Over 280 cyclin D3/CDK6 substrates have b\een identified. Given the diversity of substrates for cyclin/CDKs, and the altered thresholds for substrate phosphorylation that occurs during the cell cycle, it is exciting that small molecular inhibitors targeting cyclin D/CDK activity have encouraging results in specific tumors.  相似文献   

2.
3.
This study evaluated the effect of new motions of the motor TriAuto ZX2 on the cyclic fatigue of endodontic instruments. Vortex Blue 35.06 instruments were divided into four groups (n = 10) and tested for fatigue in a curved artificial canal (90° and 2 mm radius) using the following motions: continuous rotation (CR), Optimum Torque Reverse (OTR) set at 180° and the Optimum Glide Path (OGP), which was tested at 90° and 240°. The time to fracture (TTF) and the lengths of the fractured fragments were recorded. The mean TTF was significantly different among the groups (anova , P < 0.05): OGP 90° (213.39 ± 27.45), OTR 180° (121.24 ± 17.03), OGP 240° (45.24 ± 5.61) and CR (8.43 ± 1.27). Weibull analysis confirmed the shortest life expectancy for CR and the longest survival for OGP at 90°. The resistance to fatigue was affected by motions and pre‐set angles. The proprietary movements that are currently available for endodontic instruments were classified according to their kinematics.  相似文献   
4.
Background:  Nucleolin is a major nucleolar argyrophilic protein involved in carcinogenesis. There are only few studies on its tissue expression in human cancer and none in melanoma. We aimed at exploring this protein and its prognostic impact in cutaneous melanocytic lesions.
Methods:  We studied 193 cases including benign, dysplastic and malignant melanocytic lesions. Nuclear positivity was evaluated by immunohistochemistry and quantified by automated image analysis.
Results:  Most dysplastic and malignant lesions showed high percentages of cells with abnormal patterns of nuclear positivity (Abn+N) consisting in multiple, irregular, positive dots (ID+) and a coarse, irregularly positive nucleoplasm (CNpl+) or both (ID+CNpl+). The patterns CNpl+ and/or ID+CNpl+ were never observed in benign lesions, in which ID+ were also virtually absent. Abn+N% was significantly lower in dysplastic nevi than in primary melanomas and metastases and in primary melanomas than in metastases (p < 0.05). Furthermore, Abn+N was the second powerful prognostic discriminator, after melanoma thickness, and a significantly lower survival was observed in vertical growth phase melanoma patients showing Abn+N in more than 50% of melanoma cells.
Conclusion:  An altered nuclear nucleolin expression seems to accompany melanoma progression. Further investigation on nucleolin functionality and subcellular trafficking could add information on its altered role in melanoma.  相似文献   
5.
In an in vitro study, 10 gallbladders of adult pigs and 6 gallbladders of lambs, all removed immediately after slaughtering, were stimulated in a water bath by electric means to induce active contraction. Gallbladder emptying was followed by ultrasonography employing five measurement procedures: (1) gallbladder width, (2) longitudinal planimetry, (3) transverse planimetry, (4) ellipsoid method, and (5) sum of cylinders method. In an in vivo investigation, gallbladder emptying of 30 volunteers (12 healthy subjects, 18 diabetics) was evaluated in the same way after ingestion of a fatty meal. Gallbladder width was found to be unsuitable to estimate the decrease in gallbladder volume due to a nonlinear relation of the parameters. Longitudinal planimetry tended to be less valid than transverse planimetry in assessing gallbladder volume reduction. The most valid estimation of gallbladder volume decreases was obtained by the two three-dimensional procedures. However, in neither in vitro nor in vivo could a significant difference between the sum of cylinders method and the ellipsoid method in determining relative volume reduction be established. We conclude that a three-dimensional measurement procedure should be used for valid assessments of gallbladder motility. However, according to our data there is no advantage in using the time-consuming sum of cylinders method compared to the simple ellipsoid method.  相似文献   
6.
The present study investigated the expression of c-erbB-2 in 59 meningiomas, including different histological subtypes and anaplastic variants, by immunocytochemistry and molecular biological techniques. Immunohistochemistry using the monoclonal antibody FWP-51 directed against c-erbB-2-encoded oncoprotein gp185 demonstrated variable degrees of immunoreactivity in all meningiomas. The intensity of immunostaining correlated with the degree of expression as assessed by Western analysis in 28 meningiomas using polyclonal antiserum 21N. There was no correlation between the degree of expression and histological variants. Immunoreactivity of all menigiomas was distinctly less intense, however, than that of the human breast cancer cell line SK-BR-3, and slightly lower than that of brain metastases of breast and ovarian carcinomas that served as positive controls for both methods. By Southern analysis all meningiomas showed a single copy of the c-erbB-2 gene. Non-neoplastic arachnoid cap cells also exhibited c-erbB-2 expression and the degree of immunoreactivity was comparable with the majority of meningiomas. These data argue against an overexpression of c-erbB-2 in meningiomas, but rather indicate a cell-type-specific constitutive expression of the c-erbB-2 gene product in meningiomas and their putative progenitor cells. Since a subgroup of meningiomas is known to express progesterone receptors (PR), gp185 immunoreactivity was compared to the hormone receptor status using monoclonal antibody KD68. Fifty-six percent meningiomas showed PR immunoreactivity, but there was no statistically significant correlation with the degree of gp185 expression.This study was supported by a grant of the Tumorzentrum Heidelberg/Mannheim (M.K., No. 10028060)  相似文献   
7.
8.
OBJECTIVES: To assess clinical experience with NuvaRing in daily practice in Switzerland, including a large subgroup of young women (aged < or = 22 years). METHODS: Open, prospective, multicentre, observational clinical experience study to investigate cycle control, acceptability and usage of NuvaRing. RESULTS: Altogether, 2642 women participated in the programme and were included in the analysis, of which 658 were aged < or = 22 years (25% of the total group). A total of 744 women (28% of the total group) discontinued NuvaRing use; the main reason was adverse events (11% of all users). In younger women, there was a shift from moderate (-18%) and heavy (-45%) bleeding to mild bleeding (+71%) and dysmenorrhoea decreased by 60%, despite previous hormonal contraception use by 83% of women. Most women found ring insertion and removal to be straightforward (>95%), and were satisfied with its use (85%), primarily for the ring's once-a-month application (81%). Data were very similar for the total group. Cycle control and satisfaction were further improved with duration of treatment. CONCLUSIONS: In daily practice, NuvaRing improved cycle control and was highly acceptable to women, including young women. Switchers from other hormonal methods also showed improved cycle control and high satisfaction.  相似文献   
9.
Sonography is assuming an increasingly dynamic role in pediatric diagnosis. The small size of the patient and the use of short-focus, higher frequency transducers, coupled with continuous improvement in sonographic equipment, provide remarkably detailed images. The introduction of Doppler technology has catapulted sonography from the realm of purely anatomic information to that of physiologic and angiographic data. In neurosonography, there has been refinement of the nomenclature, quantification, and prognosis of intracranial hemorrhage and ischemic disorders. Doppler technology has helped us in understanding the vascular dynamics that occur after acute interruption of right internal carotid flow in patients who undergo extracorporeal membrane oxygenation. In abdominal diagnosis, sonography is also playing an increasingly important role in assessing both gastrointestinal and renal conditions. This review outlines some of the important concepts underlying pediatric sonography today and reviews some salient contributions of recent literature.  相似文献   
10.
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