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   938篇
  免费   69篇
  2023年   6篇
  2022年   20篇
  2021年   22篇
  2020年   12篇
  2019年   15篇
  2018年   15篇
  2017年   21篇
  2016年   31篇
  2015年   48篇
  2014年   51篇
  2013年   75篇
  2012年   56篇
  2011年   75篇
  2010年   38篇
  2009年   36篇
  2008年   51篇
  2007年   51篇
  2006年   43篇
  2005年   44篇
  2004年   36篇
  2003年   38篇
  2002年   47篇
  2001年   10篇
  2000年   5篇
  1999年   10篇
  1998年   10篇
  1997年   9篇
  1996年   8篇
  1995年   9篇
  1994年   8篇
  1993年   7篇
  1992年   3篇
  1991年   6篇
  1989年   5篇
  1988年   4篇
  1983年   6篇
  1982年   7篇
  1981年   4篇
  1980年   4篇
  1978年   4篇
  1973年   4篇
  1972年   8篇
  1971年   3篇
  1969年   4篇
  1967年   2篇
  1966年   2篇
  1964年   2篇
  1963年   2篇
  1962年   5篇
  1951年   2篇
排序方式: 共有1007条查询结果,搜索用时 15 毫秒
41.
42.
Relatively little is known about the genetic aberrations of conjunctival melanomas (CoM) and their correlation with clinical and histomorphological features as well as prognosis. The aim of this large collaborative multicenter study was to determine potential key biomarkers for metastatic risk and any druggable targets for high metastatic risk CoM. Using Affymetrix single nucleotide polymorphism genotyping arrays on 59 CoM, we detected frequent amplifications on chromosome (chr) 6p and deletions on 7q, and characterized mutation‐specific copy number alterations. Deletions on chr 10q11.21‐26.2, a region harboring the tumor suppressor genes, PDCD4, SUFU, NEURL1, PTEN, RASSF4, DMBT1, and C10orf90 and C10orf99, significantly correlated with metastasis (Fisher's exact, p ≤ 0.04), lymphatic invasion (Fisher's exact, p ≤ 0.02), increasing tumor thickness (Mann–Whitney, p ≤ 0.02), and BRAF mutation (Fisher's exact, p ≤ 0.05). This enhanced insight into CoM biology is a step toward identifying patients at risk of metastasis and potential therapeutic targets for systemic disease.  相似文献   
43.
Easy, economic, precise species authentication is currently necessary in many areas of research and diagnosis in molecular biology applied to conservation studies of endangered species. Here, we present a new method for the identification of three fox species of the Lycalopex genus in Chile. We developed an assay based on high‐resolution melt analysis of the mitochondrial cytochrome B gene, allowing a simple, low cost, fast, and accurate species determination. To validate the assay applicability for noninvasive samples, we collected fecal samples in the Atacama Desert, finding unexpectedly one species outside of its known distribution range. We conclude that the assay has a potential to become a valuable tool for a standardized genetic monitoring of the Lycalopex species in Chile.  相似文献   
44.
Aquatic Ecology - Jellyfish blooms are an increasingly common event in our seas. Occurring via polyps’ asexual reproduction induced by human stresses, they represent a hazard for ecosystems...  相似文献   
45.
Critical blind assessment of structure prediction techniques is crucial for the scientific community to establish the state of the art, identify bottlenecks, and guide future developments. In Critical Assessment of Techniques in Structure Prediction (CASP), human experts assess the performance of participating methods in relation to the difficulty of the prediction task in a biennial experiment on approximately 100 targets. Yet, the development of automated computational modeling methods requires more frequent evaluation cycles and larger sets of data. The “Continuous Automated Model EvaluatiOn (CAMEO)” platform complements CASP by conducting fully automated blind prediction evaluations based on the weekly pre-release of sequences of those structures, which are going to be published in the next release of the Protein Data Bank (PDB). Each week, CAMEO publishes benchmarking results for predictions corresponding to a set of about 20 targets collected during a 4-day prediction window. CAMEO benchmarking data are generated consistently for all methods at the same point in time, enabling developers to cross-validate their method's performance, and referring to their results in publications. Many successful participants of CASP have used CAMEO—either by directly benchmarking their methods within the system or by comparing their own performance to CAMEO reference data. CAMEO offers a variety of scores reflecting different aspects of structure modeling, for example, binding site accuracy, homo-oligomer interface quality, or accuracy of local model confidence estimates. By introducing the "bestSingleTemplate" method based on structure superpositions as a reference for the accuracy of 3D modeling predictions, CAMEO facilitates objective comparison of techniques and fosters the development of advanced methods.  相似文献   
46.
Candida albicans and C. dubliniensis genotype differences among Israeli ethnic groups were assessed. Isolates from Jews (51), Arabs (35) and Druze (25) were genotyped. The distributions among ethnic groups were not different, however they differed (p = 0.002) from global populations. Therefore, C. albicans and C. dubliniensis genotype distribution differences in Israel are related to changes in all ethnic groups.  相似文献   
47.
CRM197 (nontoxic diphtheria toxin): effects on advanced cancer patients   总被引:3,自引:0,他引:3  
Purpose: Many years ago, diphtheria toxin (DT) showed antitumor activity in mice and in humans, but it was unclear whether this depended on the toxicity of the molecule only or on its strong inflammatory-immunological property as well. To deal with this open question, we planned to treat a group of cancer patients with cross-reacting material 197 (CRM197). CRM197 is a nontoxic mutant of DT that shares the immunological properties of the native molecule and its ability to bind to heparin-binding epidermal growth factor (HB-EGF), the specific cell-membrane receptor for DT that is often overexpressed in cancer. Methods: 25 outpatients with various advanced tumors who were refractory to standard therapies (23 subjects) or had refused, in whole or in part, conventional therapies (2 subjects) were treated with CRM197 injected subcutaneously in the abdominal wall, on alternate days, for 6 days. Three different dosages (1.7, 2.6, or 3.5 mg/day) were used according to the patients degree of immunological reactivity to DT/CRM197 (none, moderate, or high). Results: After the first administration of CRM197, a significant increase in the number of circulating neutrophils and in the serum level of TNF- was detected. Toxicities were minimal. Only patients with delayed-type hypersensitivity to DT/CRM197 had irritating skin reactions in the injection sites and a flu-like syndrome with fever. Pharmacokinetics showed a mean peak concentration (12.7 ng/ml) 12 h after the first injection and a mean half-life of 18.1 h. There were two complete and one partial responses (metastatic breast carcinoma, neuroblastoma, and metastatic breast carcinoma) lasting 4, 45+, and 15 months, respectively. Six cases of stable disease, lasting from 1 to 15 months, were also recorded. Conclusions: CRM197 injected subcutaneously elicited an inflammatory-immunological reaction, caused tolerable toxicities, was absorbed to a good extent into the circulatory system, and exerted some degree of biological antitumor activity. A possible role of neutrophils and TNF- in the mode of action of the molecule is hypothesized.  相似文献   
48.
49.
The absolute sensitivity of sporangiophores of Phycomyces blakesleeanus to centrifugal acceleration was determined on a clinostat centrifuge. The centrifuge provides centrifugal accelerations ranging from 10(-4) to 6 x g. The rotor of the centrifuge, which accommodates 96 culture vials with single sporangiophores, is clinostatted, that is, turning "head over", at slow speed (1 rev min(-1)) while it is running. The negative gravitropism of sporangiophores is characterized by two components: a polar angle, which is measured in the plane of bending, and an aiming-error angle, which indicates the deviation of the plane of bending from the vector of the centrifugal acceleration. Dose-response curves were generated for both angles with centrifugations lasting 3, 5, and 8 h. The threshold for the polar angle depends on the presence of statoliths, so-called octahedral protein crystals in the vacuoles. The albino strain C171 carAcarR (with crystals) has a threshold near 10(-2) x g while the albino strain C2 carAgeo-3 (without crystals) has a threshold of about 2 x 10(-1) x g. The threshold for the aiming error angle is ill defined and is between 10(-2) and 10(-1) x g. The threshold for the polar angle of the wild type NRRL 1555 (with crystals) is near 8 x 10(-2) x g.  相似文献   
50.
In order to study the genetic structure of the Adriatic shared stock of red mullet (Mullus barbatus), we developed a set of dinucleotide microsatellite markers. A dinucleotide-enriched genomic library was obtained, and 6 polymorphic dinucleotide loci were successfully optimized. The markers showed high expected heterozygosity (from 0.68 to 0.92) and allele number (from 12 to 33); thus they appear to be suitable for detecting genetic differences in the population of red mullet. Four Adriatic samples were subsequently analyzed for microsatellite variation, and the results showed subtle but statistically significant genetic differentiation, indicating that the Adriatic red mullet may group into local, genetically isolated populations. No correlation between geographic distance and genetic differentiation was observed. In addition, the evidence of recent bottlenecks in the Adriatic samples indicates that the observed population subdivision might reflect random local allelic variations, generated by reproductive success, survival rates, or fishing pressure.  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