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   1818篇
  免费   77篇
  国内免费   5篇
耳鼻咽喉   23篇
儿科学   16篇
妇产科学   25篇
基础医学   431篇
口腔科学   25篇
临床医学   198篇
内科学   339篇
皮肤病学   10篇
神经病学   146篇
特种医学   62篇
外科学   261篇
综合类   6篇
预防医学   77篇
眼科学   16篇
药学   141篇
中国医学   2篇
肿瘤学   122篇
  2023年   8篇
  2022年   55篇
  2021年   63篇
  2020年   28篇
  2019年   37篇
  2018年   53篇
  2017年   24篇
  2016年   33篇
  2015年   43篇
  2014年   39篇
  2013年   55篇
  2012年   101篇
  2011年   116篇
  2010年   50篇
  2009年   39篇
  2008年   95篇
  2007年   88篇
  2006年   70篇
  2005年   104篇
  2004年   81篇
  2003年   73篇
  2002年   68篇
  2001年   27篇
  2000年   27篇
  1999年   27篇
  1998年   13篇
  1997年   15篇
  1996年   7篇
  1995年   13篇
  1992年   27篇
  1991年   34篇
  1990年   30篇
  1989年   24篇
  1988年   24篇
  1987年   31篇
  1986年   34篇
  1985年   22篇
  1984年   26篇
  1983年   31篇
  1982年   16篇
  1980年   9篇
  1979年   13篇
  1978年   11篇
  1977年   11篇
  1976年   10篇
  1975年   10篇
  1974年   13篇
  1973年   6篇
  1972年   11篇
  1971年   16篇
排序方式: 共有1900条查询结果,搜索用时 31 毫秒
31.
32.
Historically, most vaccines have been based on killed or live‐attenuated infectious agents. Although very successful at immunizing populations against disease, both approaches raise safety concerns and often have limited production capacity. This has resulted in increased emphasis on the development of subunit vaccines. Several recombinant systems have been considered for subunit vaccine manufacture, including plants, which offer advantages both in cost and in scale of production. We have developed a plant expression system utilizing a ‘launch vector’, which combines the advantageous features of standard agrobacterial binary plasmids and plant viral vectors, to achieve high‐level target antigen expression in plants. As an additional feature, to aid in target expression, stability and purification, we have engineered a thermostable carrier molecule to which antigens are fused. We have applied this launch vector/carrier system to engineer and express target antigens from various pathogens, including, influenza A/Vietnam/04 (H5N1) virus.  相似文献   
33.
The spatial accuracy of transcranial magnetic stimulation (TMS) may be as small as a few millimeters. Despite such great potential, navigated TMS (nTMS) mapping is still underused for the assessment of motor plasticity, particularly in clinical settings. Here, we investigate the within‐limb somatotopy gradient as well as absolute and relative reliability of three hand muscle cortical representations (MCRs) using a comprehensive grid‐based sulcus‐informed nTMS motor mapping. We enrolled 22 young healthy male volunteers. Two nTMS mapping sessions were separated by 5–10 days. Motor evoked potentials were obtained from abductor pollicis brevis (APB), abductor digiti minimi, and extensor digitorum communis. In addition to individual MRI‐based analysis, we studied normalized MNI MCRs. For the reliability assessment, we calculated intraclass correlation and the smallest detectable change. Our results revealed a somatotopy gradient reflected by APB MCR having the most lateral location. Reliability analysis showed that the commonly used metrics of MCRs, such as areas, volumes, centers of gravity (COGs), and hotspots had a high relative and low absolute reliability for all three muscles. For within‐limb TMS somatotopy, the most common metrics such as the shifts between MCR COGs and hotspots had poor relative reliability. However, overlaps between different muscle MCRs were highly reliable. We, thus, provide novel evidence that inter‐muscle MCR interaction can be reliably traced using MCR overlaps while shifts between the COGs and hotspots of different MCRs are not suitable for this purpose. Our results have implications for the interpretation of nTMS motor mapping results in healthy subjects and patients with neurological conditions.  相似文献   
34.
Novel functionalized (biofunctionalization followed by cisplatin immobilization) Fe3O4@SiO2@Au nanoparticles (NPs) were designed. The encapsulation of Fe3O4 cores inside continuous SiO2 shells preserves their initial structure and strong magnetic properties, while the shell surface can be decorated by small Au NPs, and then cisplatin (cPt) can be successfully immobilized on their surface. The fabricated NPs exhibit very strong T2 contrasting properties for magnetic resonance imaging (MRI). The functionalized Fe3O4@SiO2@Au NPs are tested for a potential application in photothermal cancer therapy, which is simulated by irradiation of two colon cancer cell lines (SW480 and SW620) with a laser (λ = 808 nm, W = 100 mW cm−2). It is found that the functionalized NPs possess low toxicity towards cancer cells (∼10–15%), which however could be drastically increased by laser irradiation, leading to a mortality of the cells of ∼43–50%. This increase of the cytotoxic properties of the Fe3O4@SiO2@Au NPs, due to the synergic effect between the presence of cPt plus Au NPs and laser irradiation, makes these NPs perspective agents for potential (MRI)-guided stimulated chemo-photothermal treatment of cancer.

Novel functionalized nanoparticles, with toxicity controlled by laser irradiation, are perspective agents for potential (MRI)-guided stimulated chemo-photothermal treatment of cancer.  相似文献   
35.
36.
The research included 54 individuals of the goosander Mergus merganser L., 1758 (Anseriformes, Mergini), wintering on Lake Dabie within the administrative limits of Szczecin. Seven species of cestoda from two families were found in those ducks. Two species from the family Diphyllobothriidae were recorded: Ligula intestinalis (Linnaeus, 1758) and Schistocephalus solidus (Müller, 1776), and five species from family Hymenolepididae: Dicranotaenia mergi Yamaguti, 1940, Fimbriaria mergi Grytner-Ziecina et Cielecka, 1995, Microsomacanthus vistulae (Czaplinski, 1960), Retinometra macracanthos (von Linstow, 1877) oraz Tschertkovilepis tenuirostris (Rudolphi, 1819). Founding species Dicranotaenia mergi is the first observation of this type in Poland.  相似文献   
37.
Combination of the Q beta replicase reaction with the Escherichia coli cell-free translation system markedly enhances replication of a recombinant RQ-DHFR RNA consisting of the dihydrofolate reductase (DHFR) mRNA sequence inserted into RQ135(-1) RNA, an efficient naturally occurring Q beta replicase template. The enhancement is associated with a replication asymmetry previously described for the replication of Q beta phage RNA in vivo; the sense (+)-strands are produced in large excess over the antisense (-)-strands. This, in turn, results in increased synthesis of the functionally active DHFR. These effects are not observed when DHFR mRNAs or RQ135(-1) RNAs are used as templates, if the translation system is not complete, or if it is inhibited by puromycin. The coupled replication-translation of nonviral mRNA recombinants can serve as a useful model for studying the fundamental aspects of virus amplification and can be implemented for large-scale protein synthesis in vitro.  相似文献   
38.
Idiopathic pulmonary fibrosis (IPF) is an age-related fatal disease with unknown etiology and no effective treatment. In this study, we show that primary cultures of fibroblasts derived from lung biopsies of IPF patients exhibited (i) accelerated replicative cellular senescence (CS); (ii) high resistance to oxidative-stress-induced cytotoxicity or CS; (iii) a CS-like morphology (even at the proliferative phase); and (iv) rapid accumulation of senescent cells expressing the myofibroblast marker α-SMA. Our findings suggest that CS could serve as a bridge connecting lung aging and its quite frequent outcome -- pulmonary fibrosis, and be an important player in the disease progression. Consequently, targeting senescent cells offers the potential of being a promising therapeutic approach.  相似文献   
39.

Background and Objectives:

Women with endometriosis often report onset of symptoms during adolescence; however, the diagnosis of endometriosis is often delayed. The aim of this study was to describe the experience of adolescents who underwent laparoscopy for pelvic pain and were diagnosed with endometriosis: specifically, the symptoms, time from onset of symptoms to correct diagnosis, number and type of medical professionals seen, diagnosis, treatment, and postoperative outcomes.

Methods:

We reviewed a series of 25 females ≤21 years of age with endometriosis diagnosed during laparoscopy for pelvic pain over an 8-year period. These patients were followed up for 1 year after surgery.

Results:

The mean age at the time of surgery was 17.2 (2.4) years (range, 10–21). The most common complaints were dysmenorrhea (64%), menorrhagia (44%), abnormal/irregular uterine bleeding (60%), ≥1 gastrointestinal symptoms (56%), and ≥1 genitourinary symptoms (52%). The mean time from the onset of symptoms until diagnosis was 22.8 (31.0) months (range, 1–132). The median number of physicians who evaluated their pain was 3 (2.3) (range, 1–12). The adolescents had stage I (68%), stage II (20%), and stage III (12%) disease. Atypical endometriosis lesions were most commonly observed during laparoscopy. At 1 year, 64% reported resolved pain, 16% improved pain, 12% continued pain, and 8% recurrent pain.

Conclusions:

Timely referral to a gynecologist experienced with laparoscopic diagnosis and treatment of endometriosis is critical to expedite care for adolescents with pelvic pain. Once the disease is diagnosed and treated, these patients have favorable outcomes with hormonal and nonhormonal therapy.  相似文献   
40.
Uterine organization and interaction with developing eggs in Tetrabothrius erostris (Tetrabothriidea), Nippotaenia mogurndae (Nippotaeniidea), Arostrilepis tenuicirrosa, and Monocercus arionis (Cyclophyllidea), cestodes belonging to three different orders, were investigated by scanning electron microscopy. The interactions were traced from sexually mature to gravid proglottids for all species. Pieces of evidence of interactions among these species include specific tight contacts between microlamellae of the uterine epithelium and the egg capsule, networks of fibrils between eggs and uterus, or numerous branched diverticula of the uterine wall that surround eggs or combinations of these. The contacts between uterine epithelium and eggs take place in mature and post-mature proglottids, at a period of development when eggs are newly formed and the embryos are rapidly developing. The eggs grow and develop actively in tight contact with the uterine wall. The maximum diameter of eggs increases 1.5–2 times (or 3.5–4 times in M. arionis) during development. In all species, the intimate contacts between uterus and eggs have weakened or disappeared by the time the proglottids have become gravid. The association between uterus and eggs thus appears as strong evidence of active trophic interaction (or matrotrophy) between the parent organism and developing eggs.  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